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Morphology of Flowering Plants Class 11 Notes Biology Chapter 5
Topics and Subtopics in NCERT Solutions for Class 11 Biology Chapter 5 Morphology of Flowering Plants:
|Section Name||Topic Name|
|5||Morphology of Flowering Plants|
|5.8||Semi-technical Description of a Typical Flowering Plant|
|5.9||Description of Some Important Families|
The angiosperms or flowering plants show a large diversity in external structure called as morphology (Gk. Morphe—form; logos—study). However, they all are characterised by the presence of roots, stems, leaves, flowers and fruits.
1. Flowering Plants
The plant body consists of a main axis, which may be branched or unbranched bearing lateral appendages.
The main axis is divided into two parts
(i) Root system The underground root system develops from the radicle embryo and helps in fixation of the plant as well as absorption of water and minerals.
(ii) Shoot system The aerial shoot system develops from the plumule embryo.
It contains root, stem, leaves as vegetative parts and flowers, fruits and seeds as reproductive parts. The Vegetative parts are involved in various vegetative functions like structural organisation, fixation, absorption, nourishment, growth and maintenance of various components and ” reproducting parts are for sexual reproduction and germination of new plants.
In plants, root is the non-green (due to absence of chlorophyll), cylindrical and descending part that normally grows downwards into the soil. It does not bear leaves, buds and not distinguished into nodes and inter nodes.
Regions of the Root
A typical root contains following five regions. However, there is no clear line of distinction between these regions.
i. Root Cap (Calyptra)
The root is covered at the apex by a thimble or cap-like structure called the root cap. It protects the root meristem from friction of the soil particles and also protect tender apex which allow the passage of root through cells, e.g., Lemna, Eichhornia.
ii. Growing Point (Meristematic) Zone
It is a small (about 1 mm in length) thin-walled region having dense protoplasm. It lies partly within and partly beyond the root cap. Its cell divide regularly and repeatedly for elongation. It is responsible for the growth of the root.
iii. Zone of Elongation
It is situated behind the meristematic region (growing point). The cells elongate speedily and increases the length of the root. The cells of this region can absorb water and minerals from the soil.
iv. Root Hair Zone
It is the region where primary tissues differentiate into the root. The vascular tissues like xylem and phloem are formed.
Root hair zone is the most important part of the root for absorption of water (most of the water) from the soil. The root hairs increase the exposed surface of the root for absorption.
v. Zone of Maturation
This zone contains mature cells. It forms the permanent zone of the root and also gives out lateral roots from the interior part of this region, e.g., In dicots and gymnosperms.
• Roots of parasitic plants lack root caps.
• In aquatic plants, root hairs are usually absent.
Types of Root System
The root system can be of two types on the basis of place of origin
i. Tap Root System
The tap root develops from the radicle of embryo of a seed. In most of the plants, primary root persists and becomes stronger to form tap root. The first root forms by the elongation of radicle and is called primary root. It continuously grows and produces lateral roots called secondary roots.
The further branches of the secondary roots are called tertiary roots and so on. These types of roots are present in dicots, e.g., Pea, gram, groundnut, etc.
ii. Adventitious Root System
The roots developing from any part of the plant other than the radicle are known as adventitious roots (L.adventitious .extraordinary). These are usually found in monocots.
The adventitious roots can be further classified as following on the basis of nature of development
(a) Fibrous Roots The primary root soon gets replaced by a cluster of slender, thread-like roots originating from the base of the stem, e.g, Triticum vulgare (wheat), Oryza sativa (rice), Allium sepa (onion).
(b) Foliar Roots These roots develop from the leaf, i.e., from the petiole of the leaf, e.g., Pogostemon, rubber plant.
(c)True Adventitious Roots These roots develop from the nodes and internodes of the stem, e.g., Prop roots of banyan (Ficus), climbing roots of money plant (Pothos), roots from the stem when partially immersed in water (Coleus), roots from nodes (Oxalis repens) etc.
Modification of Roots
The modifications are the changes in shape, form or structure in an organ to carryout special function other than or in addition to the normal functions. Modification of roots are found in both tap roots ancf adventitious roots.
Modification of Tap Roots
The tap roots are modified for the function like storage, nitrogen-fixation and respiration.
(a) Conical Roots These are fleshy tap roots that resemble a cone (broad at the base and gradually tapering towards the apex), e.g., carrot (Daucus carotd).
(b) Fusiform Roots The primary root is spindle-shaped. It is swollen in the middle and gradually tapers at both the ends, e.g., Radish (Raphanus sativus).
(c) Napiform Roots The primary root is almost spherical (pitcher-shaped) at the base and tapers abruptly at the lower end, e.g., – beetroot (Beta vulgaris),-turnip (Brassica rapa), etc.
(d) Tuberous Roots The primary root becomes thick and fleshy but do not attain any definite shape (irregularly-shaped), e.g., 4 O’clock plant (Mirabilis jalapd), Echinocystis lobata.
(e) Nodulated Tap Roots In this the secondary, tertiary and sometimes primary roots bear many small irregular swellings called root nodules which contain countless, minute nitrogen fixing bacteria of the genus Rhizobium, e.g., groundnut (Arachis bypogea), clover (Medicago falcata), pea (Pisum sativum), etc.
(f) Pneumatophores These are special roots that develop in mangrove plants (grow in marshy areas). The pneumatophores or aerophores or respiratory roots grow vertically upward and are negatively geotropic.
They have minute breathing pores called pneumatophores or lenticels present on the tips of vertical roots that help in getting oxygen for respiration.
Modification of Adventitious Roots
The adventitious roots are modified to perform several additional functions like food storage, mechanical support and other vital functions.
(a) Fasiculated Roots These arises in clusters from the base of the stem, e.g., Dahlia, Asparagus.
(b) Nodulous Roots These roots have swellings occur only near the tips, e.g., Arrow root (Maranta), amia haldi (Curcuma amadd).
(c) Tuberous Roots (Single Root Tubers) These are swollen without any definite shape, e.g., Ipomoea batatas (sweet potato).
(d) Prop (Pillar) Roots The prop roots grow as the horizontal branches of the stem and grow vertically downward.
They become thick pillar-like and provide mechanical support to the giant trees, e.g., Banyan tree (Ficus benghalensis).
(e) Stilt Roots These are small thick supporting roots growing obliquely from the basal nodes of the main stem. These provide mechanical support, e.g., Saccharum officinarum (sugarcane), Zea mays (maize).
(f) Climbing (Clinging) Roots These roots are found in climbers. They may arise from the nodes, e.g., Ivy, Pothos (money plant).
(g) Assimilatory (Photosynthetic) Roots These roots have chlorophyll and can synthesise food, e.g., Aerial or hanging roots of some orchids.
(h) Parasitic (Sucking) Roots These roots occur in parasitic plant for absorbing nourishment from their host. These roots function as haustoria, e.g., Cuscuta (dodder).
Functions of Roots
The major functions of roots are as follows
(i) Fixation Root provides fixation to the plants with soil.
(ii) Absorption Roots absorb water and minerals from the soil and provide it to all parts of the body.
Storage Roots of many plants store food for the use of other plant parts and for animals.
(iv) Aeration Plants growing in waterlogged soil or marshy areas have special roots, i.e., pneumatophores for respiration.
(v) Conduction Roots transport water and minerals in upward direction for the uses of stems and leaves.
The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits. It develops from the plumule of the embryo of a germinating seed.
It shows distinction into nodes and internodes; where node is the region from where leaves are born and internodes are the region between two nodes. Its apex bears a terminal bud for growth in length.
A bud can be defined as a condensed embryonic shoot that has a growing point surrounded by closely packed immature leaves. When bud grows, the internodes become longer and the leaves spread out, resulting in the formation of a young shoot.
* The largest bud is cabbage.
* Bamboo is considered to be tallest herb, tallest shrub or arborescent grass. Bamboos are called culms, after the jointed nature of their stems.
Forms of Stem
Stem may be aerial, subaerial or underground. In most of the plants, stems grow above the soil. These are aerial stems. The aerial stems of some plants trail or creep on the ground. They are called subaerial stems. In some plants, the stem grow in the soil and are called underground stems.
i. Aerial Stems
The aerial stems have two forms, i.e., reduced stem and erect stem.
(a) Reduced Stems It is reduced to a small disc. The * nodes and internodes are not distinguished, e.g., carrot, radish, turnip, etc. In some aquatic plants, the reduced discoid stem is green and flattened to float on the surface of water. It does not bear leaves, e.g., Lemna, Wolffia, Spirodela. In underground structures also a reduced, non-green stem is found, e.g., Garlic, onion and lily.
(b) Erect Stems These stems are strong enough to remain erect or upright without any external support.
ii. Subaerial Stem
In subaerial stems, some part lives underground, whereas, the remaining part of the stem is aerial.
The subaerial stem are also divided into two forms
(a) Upright Weak Stems These stems are weak which climb up a support to expose their foliage and reproductive organs.
These are of two types twiners and climbers
* Twiners These are long, slender and very sensitive and coil around an upright support on coming in contact, e.g, Dolichos lab lab (bean), Clitoria (butterfly pea), Cuscuta.
* Climbers These have weak and flexible stem which climb up a support with the help of certain clasping or clinging structures, e.g., Bougainvillea.
(b) Prostate Weak Stems These weak stems take support of the ground for spreading as growth occurs.
They are of following four types
* Trailers (creepers) They trail along the surface and do not climb up.
* Runners These are subaerial weak stems that grow horizontally along the soil surface, e.g., Cynadon (lawn grass), Centella (brahmi booti), Oxalis, etc.
* Stolons These subaerial weak stems are horizontal or branched runners with long internodes which can pass over small obstacless. Stolons, also propagate vegetatively like runners, e.g, Fragaria verica (strawberry), Jasminum (jasmine), Mentha piperita (peppermint).
* Offsets These weak stems are one internode long, stout, slender and runs horizontally and terminates in a bud at a short distance that develops into adventitious roots, e.g., Pistia (water lettuce), Eichhomia (water hyacinth), etc.
iv. Underground Stems
The stem of some plants lie below the soil surface. They are non-green, store food as means of perennation and vegetative propagation.
They are of following types
(a) Rhizome It is a prostrate thick stem growing horizontally beneath the soil surface. It has distinct nodes and internodes. The. nodes bear small scale leaves with buds in their axils, e.g., Zingiber (ginger officinale), Curcuma domestica (turmeric).
(b) Suckers These are non-green slender stem that grows horizontally in the soil and ultimately comes out to form a new aerial shoot. Each sucker contains one or more nodes with scale leaves and axillary buds, e.g., Mentha (podina), Chrysanthemum (guldaudi).
(c) Corm It is a swollen condensed form of rhizome which grows in the vertical direction in the soil. It stores a large amount of food, e.g., Amorphophallus, Colocasia (taro).
(d) Tuber It is a swollen end of underground stem branches. Each tuber has many notches on the surface called eyes or buds, which grow into new plants, e.g, Solanum tuberosum (potato).
(e) Bulb It is a highly reduced disc like stem. It bears a large number of fibrous adventitious roots at its base. Leaf bases form bulblets. The bulblets grow into new plants, e.g., Allium cepa (onion), Allium sativum (garlic).
Branching Pattern of Stem
The stems may be branched or unbranched.
Branching in stems may be dichotomous and lateral.
(i) The dichotomous branching occurs by the division of the apical growing point or bud into two equal parts in a forked manner. It occurs in lower plants-cryptogams (non-flowering plants), higher plants~Hyphaene (palm), Canscora, screw pine, etc.
(ii) The lateral branching occurs from the axillary buds of the nodes, e.g., Pinus, grapevine, etc.
Functions of Stem
Stems perform various primary and secondary functions.
(a) It bears leaves, fruits, flowers and seeds in position.
(b) It conducts water and minerals to roots, leaves, flowers, fruits, etc.
(c) It holds flower in suitable position, so that pollination and fertilistaion takes place.
(a) Many stems store food as reserve food materials.
(b) Some stems also help in photosynthesis and vegetative propagation.
(c) The underground stems help in perennation.
(d) Stem branches provide support to its various parts.
Modification of Stem
The various forms of aerial stem modification are following
i. Stem Tendrils
These are thin, long and sensitive structures which can coil around a support.
Tendrils can be of following types on the basis of their origin (d) Axillary Arise from axiallary buds, e.g., Passiflora (passion flower).
(b) Extra axillary Develop near the axillary bud, e.g., Lujfa, Cucurbita (pumpkin), etc.
(c) Apical bud These are modified to form tendrils, e.g., Vitis vinifera.
(d) Floral bud These are modified to form tendrils, e.g., Antigonon.
The stem thorns are stiff, woody, sharp and pointed. They develop from axillary bud. They protect the plants from browsing animals, e.g., Citrus, Duranta, Bougainvillea, Pomegranate, etc.
These are modified stems and act as climbing organs. They protect the plants from grazing animals and also help in climbing in some cases, e.g., Argemone maxicana (prickly poppy), Rosa indica (rose), Bombax (sembal), etc.
These are green, flattened structures bearing several nodes and internodes. The true leaves are reduced to spines or scales. They show unlimited growth. Some phylloclades also store food and water. The phylloclades are examples of some xerophytic plants, e.g., Opuntia (nagaphani), Casuarina, Euphorbia.
Cladodes (Cladophylls) .
They are green photosynthetic stems generally one inter node long. These develop by the modification of only stem branches of limited growth and are green (photosynthetic). The true leaves of the plant are reduced to scales or spines, e.g., Ruscus, Asparagus.
These are modified vegetative or floral buds arising in the axil of scale or foliage leaves. The bulbil helps in vegetative propagation, e.g., Lilium, Agave, Dioscorea (wild yam), Oxalis, etc.
The leaf is a lateral, generally Battened structure borne on the stem. It develops at the node and bears a bud in its axil. The axillary bud later develops into a branch. Leaves originate from shoot apical meristems and are arranged in an acropetal order. They are the most important vegetative organs for photosynthesis.
Parts of a Leaf
The leaves also consist of two lateral outgrowths called stipules at their bases.
A typical leaf has three main parts.
i.Leaf Base (Hypopodium)
The leaf is attached to the stem by the leaf base. Monocots, the leaf base is said to be sheathing as it expands and partially and wholly surrounds the stem. In dicots, the leaf base bears two lateral outgrowths called stipules.
In some leguminous plants, the leaf base may become swollen which is called the pulvinus. Leaves with stipules are called stipulate and those without them are termed as exstipulate.
ii. Petiole (Mesopodium)
It is the stalk of a leaf. Petiole help hold the leaf blade towards light. Petiole raises the lamina high to the level of stem so as to provide maximum required exposure to light and air.
iii. Lamina (Epipodium)
The lamina or leaf blade is the green, expanded part of the leaf with veins and veinlets. It has a prominent median vein called the midrib. It produces thinner lateral veins which in turn branch to form veinlets.
The lamina is the seat of photosynthesis, gaseous exchange, transpiration and other metabolic activities. The shape, margin, apex, surface and extent of invision of lamina varies in different leaves.
The arrangement of veins and veinlets in the lamina of leaf is called venation. The midrib, veins and veinlets are contain vascular tissues, i.e., The xylem and phloem for conduction water, mineral salts and food.
Leaves have mainly two types of venation
i. Reticulate Venation
When the veinlets form a network, the venation is called reticulate. It is found in dicot leaves. However, some monocot leaves like Smilax, Dioscorea and Alocasia also show reticulate venation.
ii. Parallel Venation
When the veins run parallel to each other within a lamina, the venation is termed as parallel, e.g. Calophyllum, Zingiber officinale, etc.
Types of Leaves
Leaves can be of following types
i. Simple Leaves
A leaf having a single or undivided lamina is called simple leaf. The lamina of a simple leaf may be incised but the incisions do not touch the midrib.
The lamina can have various types of incisions which may reach upto half (fid), more than half (partite) or near the base or midrib (sect).
A leaf is called compound when the incision of the leaf blade goes down to the midrib (rachis) or to the petiole so that the leaf is broken up into a number of segments called leaflets.
A bud is present in the axil of petiole in both simple and compound leaves but not in the axil of leaflets of the compound leaf.
A compound leaf can be of following two types
(a) Pinnately Compound Leaves In these leaves, the incision of lamina is directed towards the midrib, which is known as rachis. Leaflets are arranged on both side on the rachis, e.g., Neem, rose, etc.
(b) Palmate Compound Leaves The leaflets are attached at a common point, i.e., at the tip of petiole as in silk cotton.
The pattern of arrangement of leaves on the stem or branch is called phyllotaxy. It helps to avoid overcrowding and provide every leaf with optimum sunshine.
Phyllotaxy is usually of three types
i. Alternate (Spiral) Phyllotaxy
A single leaf arises at each node in alternate manner, e.g, China rose, mustard and sunflower plants.
ii. Opposite Phyllotaxy
A pair of leaves axises at each node and opposite to each other, e.g., Calotropis and Psidium guajava (guava plants).
Whorled (Verticillate) Phyllotaxy
If more than two leaves arise at a node and form a whorl, it is called whorled. The leaves of one whorl generally alternate with those of the adjacent whorls in order to provide maximum exposure, e.g., Nerium (kaner), Alstonia.
Modification of Leaves
Leaves of plants are modified to perform different additional functions in addition to their main function, i.e., photosynthesis.
i. Leaf Tendrils
These are thread-like sensitive structures, which can coil around a support to help the plant in climbing, e.g, Wild pea (Lathyrus aphaca), Pisum sativum (sweet pea) and Gloriosa superba (glory lily). ”
It is a green, short lived and flattened petiole or rachis of a leaf, which performs the function of photosynthesis, e.g, Australian Acacia. Phyilodes develop usually vertically and possess fewer stomata hence, reduce transpiration.
The segments of the leaf modify into bladder-like structures, which trap small insects present in the water. e.g., Bladderwort (Utricularia).
It is a petiole modified into a tendril to hold the pitcher upright. The leaf base is expanded to carry out photosynthesis. The leaf apex is modified into a lid, e.g, Nepenthes, Dischidia and Sarracenia.
v. Leaf Spines
The entire leaf or a part of a leaf may be modified into a pointed structure called a spine, as in Opuntia.
vi. Scale Leaves
These are thin, membranous leaves found at the nodal region. Each scale leaf contains an axillary bud in its axil, e.g, Zingiber officinale (ginger).
Functions of Leaves
The leaves have many primary and secondary functions.
(a) The most important function of leaves is photosynthesis with the help of sunlight and carbon dioxide.
(b) Leaves contain stomata through, which gaseous exchange occurs,
(c) Leaves are the site of transpiration.
(d) They protect axillary and terminal bud from mechanical injury and desiccation.
(a) Leaves store food as in the leaf base, e.g., Onion.
(b) Leaves change into phyilodes to protect against transpiration.
(c) Storage of water in the cells of some succulent plants, e.g., Aloe.
(d) In Salvinia, one leaf of each node is changed into roots that act as balancer for floating.
(e) In some leaves like of Euphorbia, the young leaves are brightly coloured to attract insects for pollination.
The arrangement and distribution of flowers over a plant is called inflorescence.
The inflorescence can be of following three types
1. Racemose Inflorescence
In racemose type of inflorescence, the main axis continues to grow and the flowers are borne laterally in an acropetal succession (the older flowers are found towards the base and younger ones at the apex) or centripetal (older towards periphery and younger towards centre).
2. Cymose Inflorescence
In cymose inflorescence, the tip of the main axis terminates in a flower and further growth continues by one or more lateral branches, which also behave like the main axis.
The arrangement of flowers in either basipetal (younger flowers occupy basal position, while older flowers towards the apex) or centrifugal (older towards center and younger towards periphery).
3. Special Inflorescence
It mainly involves highly modified and densely crowded inflorescences.
The special type of inflorescence can be divided into following types
It is highly reduced and is a cup-shaped involucre of five bracts having nectariferous glands. A single large female flower is present in the centre of the cup and scorpioid male flowers surrounded this female flower. Every male flower is represented by a single stalked stamen borne in the axil of a scaly bract, e.g, Euphorbia.
These are two clusters each having 3-9 flowers that develop on a node in the axils of opposite leaves, e.g., Ocimum sanctum (basil).
In this type, the main axis is condensed into a cup or flask-shaped, fleshy receptacle. It bears three kinds of flowers, i.e., male flowers (towards the pore), female flowers (towards the base) and neutral flowers occurs in between male and female flowers, e.g., Peepal (Ficus relegiosa) and banyan (Ficus benghalensis).
The flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. Morphologically, it is considered as a shoot bearing nodes and modified floral leaves. A flowers is called modified shoot because the position of the buds of both flower and shoot which is same and can be in terminal or axillary in position.
Structure of Flower
A flower arises in the axil of a leaf like structure called bract. Flowers with bracts are called bracteate and those without bracts are called ebracteate.
The terminal part of the axis of the flower is the receptacle or thalamus. The receptacle contains sepals, petals, stamens and carpels. If the leaves are present on the pedical, they are called bracteoles.
Parts of a Flower
A typical flower consists of four distinct parts the calyx, the corolla, the androecium and the gynoecium. The calyx and corolla are accessory parts and the androecium and gynoecium are essential parts.
These essential parts consist of two kinds of (male) sporophylls, the microsporophyll (male) and the megasporophyll (female).
A flower can be unisexual or bisexual. It is borne on short or long axis. The axis contains two regions the pedicel and the thalamus or receptacle.
The pedicel may be short, long or even absent. The thalamus is the swollen end of the axis on which the floral whorls are arranged.
Different parts of flower are given below
It is the outermost whorl of a flower. It is made up of units like sepals. The sepals are generally green, leaf like and protect the flower in the bud stage, i.e., when floral in bud condition. They have veins and stomata like ordinary leaves but are thicker in nature. The sepals may be gamosepalous (sepals united), e.g., Caesalpinia or polysepalous (sepals free), e.g., Crotalaria.
The sepals also prevent transpiration from inner parts of the flower. Coloured sepals attract insects for pollination.
It is composed of petals. Petals are usually brightly coloured to attract insects for pollination. Like calyx, corolla may also be gamopetalons (petals united) or polypetalous (petals free). The shape and colour of corolla may vary greatly in shape. Corolla may be tubular, bell-shaped, funnel-shaped.
The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation. The aestivation pattern is important in classification of – plants.
It is of following types
(a) Valvate Petals come to each other but do not overlap, e.g., mustard (Brassica).
(b) Twisted Regular overlapping of petals occurs in which margin of one petal overlap with the next one petal, e.g., China rose (Hibiscus rosa sinensis).
(c) Imbricate There are five petals, arranged in such a way that one petal is completely external and another petal is completely internal, while three petals are partially external and partially internal, e.g., Cassia, Cullistemon,Caesalpinia.
(d) Vexillary When the largest petal overlaps the two lateral petals which in turn overlap the two smallest anterior petals (keel), the aestivation is called as vexillary or papilionaceous.
It is the third whorl of flower composed of stamens or microsporangium. Each stamen, which represents the male reprodutive organ consists of a stalk or a filament and an anther. Each anther is usually bilobed which are attached at the back by a sterile band called connective and each lobe has two chambers, the pollen sacs. The pollen grains are produced in pollen sacs. A sterile stamen is called staminode. Stamens can be of different types depending on their union with other members such as petals or among themselves.
(a) When stamens are attached to the petals, they are epipetalous, e.g., Brinjal.
(b) When stamens are attached to the perianth, the condition is called epiphyllous, e.g., Lily.
(c) The stamens in a flower may either remain free, i.e., polyandrous or may be united in varying degrees.
(d) The stamens may be united into one bunch or one bundle, i.e., monoadelphous as in China rose. It may be two bundles, i.e., diadelphous as in pea or into more than two bundles, i.e., polyadelphous as in citrus.
(e) There may be variation in the length of filament as in Salvia and mustard.
Gynoecium is the female reproductive part of the flower and is made up of one or more carpels or megasporangium. Megaspores are produced within the megasporangium.’A carpel consists of three parts, i.e., stigma, style and ovary.
The stigma is usually at the tip of style and is the receptive surface for pollen grains.
Ovary is the enlarged basal part on which lies the elongated tube, the style.
The style connects the ovary to the stigma. Each ovary bears one or more ovules attached to a flattened, cushion like placenta.
Depending on the number of carpel present may be free or united, gynoecium can be of following types
(a) Apocarpous When more than one carpel is present, they may be free are called apocarpous, e.g., Lotus and rose.
(b) Syncarpous When carpels are fused together, the gynoecium is called syncarpous, e.g., Brinjal and Hibiscus.
The cavity enclosed by the ovary wall is called locule. The number of locules in the ovary correspond to the number of carpels in the gynoecium, i.e., unilocular (only one locule, e.g., Pea), bilocular (two locules, e.g., Tomato), trilocular (three locules, e.g., Ricinus), multilocular (many locules, e.g., Orange and lemon).
The arrangement of ovules within the ovary is known as placentation. The placenta is a tissue, which develops along the inner wall of the ovary. The ovule or ovules remain attached to the placenta.
The placentation can be of different types
(а) Marginal The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows is called marginal placentation, e.g., Pea.
(b) Axile When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is called axile, e.g., China rose, tomato and lemon.
(c) Parietal When the ovules develop on the inner wall of the ovary or on peripheral part, it is called parietal placentation. Ovary is one chambered but it becomes two-chambered due to formation of the false septum, e.g., Mustard and Argemone.
(d) Free central When the ovules are borne on central axis and septa are absent, the placentation is called free central, e.g., Dianthus and primrose.
(e) Basal In this type, the placenta develops at the base of ovary and a single ovule is attached to it as in sunflower, marigold. The placenta develops directly on the thalamus.
Insertion of Floral Parts (Forms of Thalamus)
The positions of different whorls of flowers are different. This is due to the position of ovary.
These positions may be of three types
i. Hypogynous Flower
The thalamus is conical, dome-shaped or flat. The ovary is present at the top of thalamus. The stamem, petals and sepals are separate and successively inserted below the ovary. Ovary is superior, whereas rest of the structures are inferior, e.g., Brassica, Hibiscus, Petunia.
ii. Perigynous Flower
The margin of thalamus grows upwards forming a cup like structure called calyx tube. The calyx tube encloses ovary, but remains free from it and the sepals, petals and stamens are present in it. The ovary is half inferior, e.g., rose, plum, peach, etc.
iii. Epigynous Flower
The thalamus grows upwards to completely develop the ovary and also fused inseparably with the latter. The other floral parts are borne at the top of the fused thalamus and ovary. The ovary is called inferior, e.g., Helianthus (sunflower), Cucurbita (pumpkin), Pyrus (apple).
Number of Floral Parts
When the floral appendages are in the multiple of 3, 4 or 5, the flower is considered as trimerous, tetramerous or pentamerous respectively.
Dicotyledonous flowers are usually di, tetra or pentamerous, while, monocotyledonous flowers are trimerous.
Symmetry of A Flower
The symmetry of a flower depends upon the shape, size and arrangement of floral parts, e.g., Calyx, corolla, androecium and gynoecium. Flowers can be actomorphic and zygomorphic on the basis of symmetry.
In this type, a flower can be divided into exactly equal halves by any vertical section passing through the centre of a flower, e.g., Mustard, datura.
In this type, flower can be divided into two identical halves through only one particular vertical plane, e.g., Ocimum, Cassia.
The characteristic feature of flowering plants is fruit. Fruit is a mature or ripened ovary, developed after fertilisation.
During fertilisation, the important changes taking place in the ovary are
(ii) The ovules present in it develops into seeds.
(ii) The wall of the ovary thickens and ripens into pericarp (fruit wall).
* Fruits developed from the fertilised ovary is called true fruits. A true fruit has two parts pericarp and the seeds.
* Fruits developed from any part of the flower along with ovary is called false fruits. The thalamus grows along with the ovary to form a false fruit i.e. in Pyrus malus (apple).
* The fruit of mango and coconut are also known as drupe, as it develop from monocarpellary superior ovaries and have only one seed.
The ovary after these changes is known as the fruit. If a fruit is formed without fertilisation, it is called parthenocarpic fruit, e.g., Banana, grapes, pineapple, etc. The parthenocarpic fruits do not have seeds.
The fruit consists of wall or pericarp and seeds. The pericarp may be dry or fleshy. When pericarp is thick and fleshy, it is differentiated into outer epicarp, the middle mesocarp and the inner endocarp.
Types of Fruits
Fruits can be broadly classified into following three types
i. Simple Fruits
A simple fruit develops from the single simple or compound ovary of a flower. These can be dry fruits (pericarp dry) or succulent fruits (pericarp fleshy).
ii. Aggregate (Etaerio) Fruits
An aggregate fruit is a group of fruitlets which develops from a flower having polycarpellary apocarpous (free) gynoecium. The aggregate fruit is also called etaerio.
iii. Multiple (Composite) Fruits
A composite (multiple) fruit develops from an entire inflorescence. The multiple fruit is composed of a number of closely associated fruits (which may or may not get fused) along with its peduncle. Hence, these fruits are pseudocarps and are also called inflorescence fruits.
Pomology is the branch of horticulture that deals with the study of fruits and their cultivation.
Edible Parts of Some Common Fruits
Importance of Fruits
(i) Fruits are a source of vitamins, organic acids, minerals, pectin and sugars and some of them are used as vegetables, e.g., Okra (lady’s finger), tomato, pumpkin, cucumber, gourd, etc.
(ii) Cereals are one seeded dry fruits, form the stable food of humans.
(iii) Fruits are important foods for fruit eating birds (frugivorous) and some animals.
(iv) Some fruits are also used as medicines, e.g., Emblica officinalis (amla), Datum stramonium (datura), Papaver somniferum (poppy), etc.
(v) They protect immature seeds against climatic conditions till their maturity.
(vi) The unripe fruits are bitter due to the presence of tannins, bitter alkaloids, astringents, sour acids, etc. This way they keep the animals away from eating them.
Seed is a ripened ovule which contains an embryo or tiny plant with sufficient reserve food for the development of embyo.
The ovules after fertilisation develops into seeds. A seed is made up of seed coats and an embryo. The embryo is made up of a radicle, an embryonal axis and one (wheat and maize) or two cotyledons (gram and pea).
Types of Seeds
Seeds can be classified into two different types based on the number of cotyledons and presence or absence of endosperms, i.e., dicotyledonous and monocotyledonous seed.
Gram seed is a dicot seed formed in a small pod or legume. The outermost covering is the seed coat. An endosperm is absent.
Seed can be studied under two heads, i.e., external structure and internal structure.
It is light or dark brown in colour. Its surface may be smooth or wrinkled. A small oval scar present at the side called hilum. It is the point where the stalk or funicle of the seed is attached to it. A narrow ridge called raphae runs from hilum to chalaza inside the furrow. A small pore called micropyle present between the hilum and pointed end.
The outermost covering of the seed is seed coat. The outer hard and leathery layer of the coat is called testa and the inner thin and membranous layer is the tegmen. In some seeds, the tegmen and testa are fused.
The seed coat encloses the embryo, which is differentiated into a radicle, a plumule and cotyledons. The radicle develops into root and plumule into shoot. Cotyledons may be one or two to serve as reserve food.
Hypocotyl is a part present between the point of attachment of cotyledon and radicle. Epicotyle is present between point of attachment of cotyledons and plumule.
In some seeds, such as castor seeds, the endosperm is formed as a result of double fertilisation, which is a food storing tissue. In plants like bean, gram and pea, the endosperm is not present in mature seeds (i.e., non-endospermous seeds).
ii- Monocotyledonous Seed
The monocotyledonous seeds are endospermic but some as in orchids are non-endospermic. In the cereals, such as maize, the seed coat is membranous and generally fused with the fruit wall.
Structure of Monocotyledonous Seed
The endosperm is bulky and stores food. The outer covering of endosperm separates the embryo by a proteinous layer called aleurone layer. The embryo is small and situated in a groove at one end of the endosperm. It consists of one large shield-shaped cotyledon known as scutellum and a short axis with a plumule and a radicle. The plumule and radicle are enclosed in sheaths which are called coleoptile and coleorhiza respectively.
Coleoptile has a terminal pore for the emergence of first leaf during germination. The sheath is capable of growth. It helps the future shoot in passing through the soil during germination, e.g., Maize grain is whitish, yellow, violet or red in colour. It has smooth or shiny surface.
Its grain is covered with a single, thin hard covering. It is formed by the fusion of seed coat or testa and the fruit wall gr pericarp.
Semi-Technical Description of a Typical Flowering Plant
The description of a flowering plant should be brief, sequential and in scientific language. This is required to designate a plant in its appropriate taxonomic position.
The Plant can be Described Briefly in the following Way
The symbolic representation of floral characters of a flower is called floral formula. For example, the floral formula ofBrassica (mustard) represented as given by
Description of this formula is Ebracteate, actinomorphic, bisexual, bimerous, calyx-4, polysepalous, in two whorls of two each corolla-4, polypetalous, cruciform, androecium-6, polyandrous, tetradynamous in two whorls, one with two, gynoecium—bicarpellary syncarpous, superior.
Symbols used in Floral Formula
Symbols for Number of Floral Parts
The number of floral parts are written at right foot of the symbol. If they are fused they are bracketed.
Some examples are given below
A floral diagram provides information about the number of parts of a flower, their arrangement and the relation, they have with one another.
The floral diagram of flower tell us about the following
In the floral diagram, the position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram.. Calyx, corolla, androecium and gynoecium are drawn in successive whorls, calyx being the outermost and the gynoecium in the centre.
Description of Some important Families
This family was earlier called Papilionoideae, a sub-family of family—Leguminosae. It is distributed all over the world.
1. system position
2. Distribution The family includes 600 genera and 13000 species. It is distributed all over the world except the Arctic regions.
3. Habit The plants are mosdy herbs, however shrubs, trees and climbers are also common.
4 Vegetative Characters
(i) Root Tap root with lateral branches. The lateral branches mostly contain bacterial nodules (with Rhizobium bacteria which fix atmospheric nitrogen).
(ii) Stem Herbaceous or woody, branched, erect or climbing.
(iii) Leaf Alternate, pinnately compound or simple, leaf base, pulvinate, stipulate, venation-reticulate.
5. Floral Characters
(i) Inflorescence Simple raceme, axillary cyme or solitary.
(ii) Flower Bracteate, pedicellate, subsessile, bisexual, mostly, irregular, zygomorphic, sometimes regular, pentamerous, hypogynous or slightly perigynous.
(a) Calyx Sepals 5, gamosepalous, imbricate aestivation.
(b) Corolla Petal 5, polypetalous, papilionac¬eous, consisting of a posterior standard, two later wings, two anterior ones forming a well (enclosing stamens and pistil), vexillary aestivation.
(c) Androecium Stamens 10, usually diadelphous [(9) +1] or monadelphous, sometimes free, polyandrous, another dithecous, basifixed (attached by its base).
(d) Gynoecium Monocarpallary, ovary superior, unilocular with marginal placentation, style bent, stigma simple and hairy.
(e) Fruit Legume (pod).
(f) Seed One to many non-endospermic.
(iii) Floral Formula
Economic Importance with Examples
Plants belonging to this family hqs their importance in the following fields
(i) Pulses and Vegetables The family is an important source of pulses and vegetables. The ^pulses are rich in proteins like gram (chana), pea (matar), field bean (bankla), cluster bean (gwar), lima bean (lobia), lentil (masoor), bean (sem), soya(soyabean), etc.
(ii) Oil Edible oils are obtained from the seeds of Arachis hypogaea (groundnut) and Glycine max (soyabean). Vegetable ghee is prepared by using the oils after hydrogenation.
(iii) Timber Dalbergia sissoo (Indian redwood),Dalbergia latifolia (Indian rose wood), are important timber yielding trees of the family.
(iv) Dye Indigofera tinctoria (indigo), Butea monosperma (flame of the forest) is used to produced red dye used as an astringent.
(v) Fodder Plants like Trifolium alexandrium (barseem), Medicago sativa, Cyamopsis tetragonoloba, etc., yield fodder for the cattle.
(vi) Fibres Crotalaria juncea (sunhemp) is used to produce fibres.
(vii) Ornamentals Some common ornamental plants are Lathyrus odoratus (sweet pea), Clitoria (butterfly pea), Lupinus, etc., are common ornamental plants.
(viii) Jewellar s Weights The seeds of Abrus precatorius (ratti) are used weight by jewellars.
(ix) Medicinal Plants The flowers of Trifolium pratense are used in whooping cough. The gum of Butea monosperma (dhak) is useful for treating dysentery and diarrhoea. There are several other examples in this family that are used as medicines.
It is a large family, commonly called as the ‘potato family, it is widely distributed in tropics, sub-tropics and even temperate zones.
1. Systematic Position
The family is represented by 90 genera and 2800 species distributed in both tropical and temperate regions.
Annual or perennial herbs, shrubs or rarely soft wooded trees.
4. Vegetative Characters
(i) Root Usually tap roots.
(ii) Stem Herbaceous or woody, hair or prickles often present, sometimes underground tubers (Solanum tuberosum).
(iii) Leaf In vegetative parts alternate and floral regions opposite, exstipulate, simple, rarely pinnately compound as in potato and tomato.
5. Floral Characters
(i) Inflorescence Solitary, axillary or cymose as in Solarium.
(ii) Flower Bisexual, actinomorphic, ebracteate, pedicellate, pentamerous and hypogynous.
(а) Calyx Sepals 5, united, valvate aestivation, usually persistent as in brinjal, tomato, chilly, etc.
(b) Corolla Petals 5, united, valvate aestivation, rotate or tubular, rarely funnel-shaped.
(c) Androecium Stamens 5, epipetalous, alternating with, petals, inserted in corolla tube, filaments usually of unequal length, anthers bithecous.
(d) Gynoecium Bicarpellary, syncarpous, ovary superior, bilocular, placenta swollen with many ovules.
(e) Fruits Berry or capsule.
(f) Seeds Endospermic, embryo straight.
Economic: Importance with Examples
Plants belonging to the family-Solanaceae has their importance in the following fields
(i) Food The family-Solanaceae includes a number of vegetables and spice yielding plants.
For example., Solanum tuberosum (potato), Solanum melongena (brinjal), Lycopersicon esculentum (tomato), Physalis peruviana (ground cherry), Capscicum annuum (chillies), etc.
(ii) Tobacco Nicotiana tabacum and N. rustica . contain toxic alkaloid nicotine. It is used for chewing, smoking and snuff.
(iii) Medicines Atropa bellodona is used to obtain Bellodona and atropine. Bellodona is used for relieving pain and treating cough. Atropine is used for dilating eye pupil. Datura stramonium is used in asthma. Other medicinal plants are Solanum xanthocarpum, Withania somnifera, Hyoscymus niger, etc.
Ornamentals The common ornamental plants are Cestrum nocturnum (Rat-ki-Rani), Petunia hybrida, Physalis peruviana (cape gooseberry), etc.
1. Systematic Position
The family—Liliaceae (lily family) includes about 250 genera and 3700 species showing world wide distribution. About 200 species are available in India.
Usually perennial herbs, perenating by underground rhizomes, corms or bulbs, rarely shrubs or climbers (e.g., Smilax, Gloriosa, etc).
4. Vegetative Characters
(i) Root Generally adventitious, fibrous or fleshy (e.g., Asparagus).
(ii) Stem Herbaceous or woody. In some species underground bulbs or rhizomes.
(iii) Leaves Mostly basal, alternate, linear, exstipulate with parallel venation.
5. Floral Characters
(i) Inflorescence Mostly racemose, sometimes cymose, rarely solitary.
(ii) Flower Bracteate, pedicellate, actinomorphic, incomplete, bisexual, trimerous and hypogynous.
(a) Perianth Tepal six (3 + 3), often united into tube, valvate aestivation.
(b)polyandrous, opposite to tepals, sometimes epiphyllous.
(c) Gynoecium Tricarpellary, syncarpous, trilocular with many ovules, axile placentation, rarely unilocular with parietal placentation, ovary superior, style simple with three lobed stigma.
(d) Fruit A loculated capsule, rarely a berry.
(e) Seed Endospermic, embryo curved or straight.
(f) Floral Formula by
Economic Importance with Examples
Plants belonging to this family has their importance in the following fields
(i) Food Allium cepa (onion), Allium sativum (garlic) young shoots and fleshy roots of Asparagus (shatavar) are used as vegetables.
(ii) Medicines Aloe leaves are used to cure piles, liver problems. Roots of Smilax are used as blood purifier. Raw onion is useful in constipation, diarrhoea and cholera. Dried corms of Colchicum autumnale (meadow saffron) are used against rheumatism and gout.
(iii) Ornamentals The common ornamentals are Ruscus, Yucca, Aloe, Asparagus, Gloriosa, Smilax, tulips, lilies, etc.
(iv) Fibres The fibre yielding plants of IHy family are Yucca filamentosa, Sansevieria roxburghiana, etc.
CBSE Class 11 Biology Chapter-5 Important Questions
1 Marks Questions
1. Which part of opuntia is modified to form spines?
2 .Name our plant in which leaf is pinnately compound.
Ans. Neem, Rose, Aeacia.
3.In mangroves, Pneumatophores are the modified adventitious roots How are these roots. How to the plant?
Ans. pncumatohores in mangroves help in respiration.
4. Which part of mango fruit is edible?
5. Why de various plant have different type of phyllotaxy?
Ans. For proper exposure of leaves to get sunlight.
6.Slate the main function of leaf tendril.
Ans. The leaf tendrils help the plant for climbing.
7. Which plant family represent the following floral formula.
8. The endosperm is formed as a result of double fertilisation (triple fusion) What is its function.
Ans. Endosperm stores the food.
9. Which type of venation do you observe in dicot leaf?
Ans. Reticulate venation.
10. In pea flower, the a in corolla is known as vexillary. (live reason.
Ans. In peas, there are five petals. The largest one (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel).
11. What is the name given to the cotyledon in case of Monocots.
12.Name one monocot & one dicot in which endosperm is present?
Ans. Monocot: Maize grain & Dicot: castir oil seed.
13.Why are date palm referred to as dioecious?
Ans. Because male & female flowers are borne on different plants.
14.What is placentation?
Ans. The arrangement of ovule in the ovary is called placentation.
15.Write floral formula of Brassica Campestris.
16.Why are flowers of cucumber referred to as epigynous ?
Ans. Because the floral parts lie above the ovary & the ovary is inferior.
17.What is false fruit?
Ans. When floral parts other than ovary takes part in formation of fruit & become edible, it is called false fruit.
18.What is the term used for a plant bearing both male & female flowers.
Ans. Monoecious flowers
19.What are runners?
Ans. A long creeping stem with long internodes running horizontally on the surface of the soil is called a runner.
20.Why are flowers of mustard referred to as hypogynous.
Ans. Because ovary is situated at the top & other three whorls are inserted below the pistil.
21.Name the two layers of seed coat.
Ans. Testa & Tegmen.
22.Which family has characteristically a swollen axile placenta.
23.Why root system is poorly developed in aquatic plants.
Ans. Because in aquatic plants there no soil to anchor firmly rather, absorption of water occurs through diffusion hence root system is not completely developed.
24.Name two plants where seeds do not have endosperm?
Ans. Bean, gram, pea.
25.Which plants part has given rise to following modifications:-
(a) Spines of opuntia (b) Pitcher of Nepenthes.
Ans. (a)modified stem (b)modified leaf.
26.Why is leaf of Neem called unipinnately compound.
Ans. Leaf of Neem is called unipinnately compound because leaflets are found in pairs on either side of rachis.
2 Marks Questions
1. Flower is a modified shoot. Justify.
Ans. The flower is considered to be a modified shoot because the internodes in a flower are highly condensed and the appendages such as sepals, petals, stamens and carpels (pistil) are generally large in number.
2.Name the type of mot for the following
(a) Roots performing the function of photosynthesis.
(b) Roots come above the surface of the soil to absorb air.
(c) The pillar like roots devclopc4 from lateral branches for providing mechanical support.
(d) Roots coming out of the lower nodes of the stem and provide the support to the plant.
Ans. (a) Assimilatory roots(b) Respiratory roots
(c) Prop roots(d) Stilt roots
3. Fill up the blank spaces (a), (b), (c) and (d) in the (able given below:
|Type of flower||Position of calyx, corolla and and roecium in respect of the ovary on thalamus||Type of ovary|
On the rim, of the thalamus almost n the name level of ovary.
Ans. (a) Floral parts are situated below the ovary
(d) floral parts are xitnated above the ovary
4. Provide (he scientific terms for (he following:
(i) The leaf without a petiole (stalk).
(ii) The flat and expanded portion of a leaf,
(iii) Orderly arrangement of leaves on the node.
(iv) Lateral appendages on either side c the loaf.
Ans. (i) Sensible
5.What is Rhizome? Give its two examples.
Ans. Rhizome is a prostrate & a thickened underground stem having distinct nodes, internodes scales, leaves as well as buds. It creeps horizontally under the ground eg. Ginger, turmeric.
6.Differentiate between epigynous & perigynous flowers.
|Epigynous flowers||Perigynous flowers|
|i) The thalamus is cup shaped & is fused with the ovary so that floral parts rise on the top of ovary.||i) The thalamus is cup-shaped structure around the ovary but is not fused & bears sepals, petals & stamens.|
|ii) Ovary is inferior eg. Apple, cucumber||ii) Ovary is half inferior eg. Rose.|
7.Give reason to justify that onion bulb is a modified stem?
Ans. Onion bulb is a modified, highly condensed & disc like. It has a large number of fleshy scale leaves. Terminal & auxiliary buds are present. On the lower posterior side a cluster of adventitious roots are present.
8.What is the difference between alternate & whorled phylotaxy.
|Alternate phyllotaxy||Whorled phyllotaxy|
|i) Only one leaf arises at each node.||i) More than two leaves arises at each node|
|ii) Leaves arises alternately on left & right sides of the stem||ii) Leaves arise in whorl from one point|
|iii) Eg. chinarose, mango||iii) Eg. Neruim|
9.Define venation? What are two types of venation?
Ans. Veins arrangement in leaf lamina is called venation. There are two types of venation:-
(a) Parallel:- when veins are arranged parallel to each other on lamina
(b) Reticulate:- when veins forms a network on leaf lamina.
10.Why is leaf of Bombax categorized as palmately compound multifoliate leaf?
Ans. Leaf of Bombax is categorized as palmately compound multifoliate leaf because the petiole bears leaflets in its lips in pinnately compound leaf. Five or more leaflets are articulated on a long axis & the shape of leaf is like the palm of a hand in Bombax. This type of leaf is called digitate.
11.Explain with suitable examples of different types phyllotaxy
Ans. Phyllotaxy is the arrangement of leaves on the stem or branch. It can be of two types:-
(i).OPPOSITE PHYLLOTAXY:- Two leaves at each node opposite to each other. Eg. calotropis Guava.
(ii).WHORLED PHYLLOTAXY:- Where more than two leaves arise at each mode eg. nerium
12.“Flower is a modified shoot.” justify the statement.
Ans. “Flower is considered as modified shoot” because the internodes in a flower are highly condense & the appendages such as sepals, petals, stamens & carpels are generally large in number.
13.Distinguish between prop root & stilt roots.
|PROP ROOTS||STILT ROOTS|
|i) arises from horizontal aerial branches of a free stem||i) Arises from basal nodes of stem.|
|ii) Long & provide support to plant like pillars||ii) Short roots and grows downward obliquely to provide support to stem like rope of tent.|
|iii) Eg. banyan tree||iii) Maize, Jowar.|
14.What is inflorescence? What are its two types?
Ans. The arrangement of flowers an the floral axis is called inflorescence. Inflorescence are of two major types:-
(a)Racemose inflorescence:- main axis continues to grow & flowers are borne laterally in acropetal succession.
(b)Cymose inflorescence: – main axis terminates in a flower hence, is limited in growth, flowers are borne in basipetal order.
15.Draw the floral formula & floral diagram of family solanaceae.
Floral Diagram :-
16.Differentiate between true fruit & false fruit.
|TRUE FRUIT||FALSE FRUIT|
|i) it develops from the ovary||i) it develops from other parts along with the ovary|
|ii) No other part is involved in fruit formation||ii) Thalamus and perianth takes part in fruit formation.|
|iii) Eg. pea.||iii) Eg. apple.|
17.Write the floral formula & draw the floral diagram of family Liliaceae.
Floral formula: –
Floral diagram: –
18.“Underground parts of a plant are not always roots” justify the statement.
Ans. Usually roots develop below the ground. But in potato, the stem gets modified into “tuber” like structure for the storage of reserve food material. These tubers develop & grow under the ground. Potato is a stem because it bears scale leaves, buds, nodes etc.
19.How would you differentiate leaflets of a compound leaf from simple leaves on a branch?
|SIMPLE LEAF||COMPOUND LEAF|
|i) Lamina is not divided into distinct lobes or leaflets.||i) Lamina is incised into two or more distinct leaflets.|
|ii) Axilliary bud is present in the axil of simple leaf.||ii) Bud is present in the axil of whole leaf.|
|iii) Simple leaves are in acropetal succession on stem||iii) Leaflets of compound leaf are not in acropetal succession.|
|iv) Base of leaf may have stipules||iv) Stipules may be present base of compound leaf|
|v) Simple leaves appear in one or more plane.||v) Leaflets in a compound leaf lie in one plane only.|
20.Draw a well labeled diagram of V.S. of maize seed.
21.Write differences between phyllode & phylloclade.
|i) Modification of petiole||i) Modification of stem|
|ii) Bears an bud in its axil||ii) Developed in axial of leaf|
|iii) Nodes internodes are not borne||iii) Nodes internodes are found.|
|iv) Does not have leaves & flowers||iv) Has reduced bristles spiny leaves & flowers.|
3 Marks Questions
1. Observe the given figure showing various types of placenta ion. Identify the type of plancentation. Give one example of each.
Ans. (a) Marginal placentrationPea
(ID) Parietal placenta ion – Mu Argemone
(c) Free central plancentation— Dianthus Primrose
2. Potato is a stem and sweet potato is a root.’ Justify the statement on the basis of external features.
Ans. Potato is the swollen tip if an underground stem branch (sto1or IL ha nodes (eyes) which consist of One or more buds subtended by a leaf sear Adventitious roots also during sprouting. On the other hand Sweet potato is a swollen adventitious root (tuberous root) It has no nodes, intern- odes and buds like a stem.
3. Define aestivation . Which type of aestivation is found in China rose, Caltrop’s Gulmohar and pea
Ans. The mode of arrangement of sepals or petals in a floral bud is known a aestivation.
Chine rose — twisted Calotropis — valvate
Gulmohar — imbricate Pea — vexillary
4. Explain the different types of phyllotaxy. Give one example of each type.
Ans. Type of phyllotaxy Exaniples
(i) AlternateChina rose, mustard
(ii) OppositeCalotropis, guava
(iii) WhorlsNerium , Alstonia
5. differeutiate between :
(a) Actiuomorphic flower and Zygornorphic flower
(b) Apocarpous ovary and Syncarpous ovary
(c) Racemose inflorescence and Cymes inflorescence
Ans. (a) Actinomorphic FlowerZygomorphic flower
(1) Two equal halves are firmedTwo equal halves are by any vertical division paproduced only by one through the centrevertical division
(2) It has a radmi yrnmetryIt has a bilateral syrnmetry
(b) Apocarpous OvarySyncarpous Ovary
1) The flower has several The flower has fused carpels. free carpels (ovary).
(2) On maturity it forms On maturity it forms a single fruit. Fruitlet of aggregate type.
(c) Recompose inflorescenceCymose Inflorescence
(1) The main axis hax unlimited growth. The main axis hax a Limited growth.
(2) flwers are arranged acropetally i.e,. flowers are arranged basipetally i.e., the lower flowers are younger.the lower l1owar ar oidet.
6. In the given structure Ma Monocotyledonous seed label the path a, b, c, d, e. (jive the function of part ‘a’
Ans. (a) Endosperm
(e) Alcuronc layer
Function of(a) – Provide nutrition.
7.Describe that parts of a typical angiospermic leaf?
Ans. A typical angiospermic foliage leaf possesses the following parts.
(i)LEAF BASE:- It is the region in the stem, from which leaf arises. Its main function is to attach the leaf with the stem are a branch.
(ii)PETIOLE:- The stalk of a leaf is called petiole. The leaves having petiole is called petiolate. As in banyan leaf, some leaves may lack petioles.
(iii)LAMINA:- The green, flattened part of the leaf attached with petiole is known as “lamina”. It is the part which performs photosynthesis, respiration & transpiration. There is a “midrib” in the middle of the lamina. The midrib in compound leaf is called rachis. The lamina may be of different shapes in different kinds of leaves.
8.Differentiate between a maiz grain & a bean seed?
|MAIZE GRAIN||BEAN SEED|
|i) It is single seeded fruit called the caryopsis||i) It is a true seed formed inside a fruit called the pod or legume.|
|ii) The fruit wall or the pericarp is fused with testa.||ii) The pericarp is free from testa.|
|iii) There is one seed coat which inseperably fused with pericarp||iii) There are two seed coats called testa & tegmen They are fused with each other.|
|iv) The grain is endospermic||iv) The seed is non endospermic.|
|v) The grain has no hilum, micropyle & chalaza on its surface.||v) The chalaza, hilum & micropyle are clearly visible.|
|vi) There is no ridge like raphe||vi) The raphe is clearly risible.|
|vii) The plumule & radical are protected by distinct sheath called the coleoptinct sheath called the coleoptiles & coleorhizae respectively||vii) The plumale & radical are not covered by any such protective sheath.|
|viii) The cotyledon acts as the absorbing structure that absorbs food from endosperm & transfers it to embryo.||viii) The cotyledons are merely food storage organs.|
9.Describe the arrangement of floral members in relation to their insertion on thalamus.
Ans. Based on the position of calyx, corolla & the androecium in respect of ovary on the thalamus, flowers may be explained into 3 kinds.
(a).HYPOGYNOUS FLOWERS:- Gynoecium located at highest position & rest whorls of flower lies below it. eg. mustard, chinarose.
(b).PERIGYNOUS FLOWERS:- The gynoecium is situated in center, other parts of flower lie on the rim of thalamus almost at same level, Ovary is half inferior eg. plum, rose.
(C)EPIGYNOUS FLOWERS:- The margins of thalamus grows upwards enclosing the ovary fully & getting to it, rest parts of the flower arises above the ovary. i.e. Ovary is inferior in these flowers. Eg. Guava, sunflower, cucumber.
10.How is herbaceous stem different from a woody stem?
|HERBACEOUS STEM||WOODY STEM|
|i) Annual or biennial & short- lived||i) Always perennial & long. Lived.|
|ii) Green, soft and fleshy and on bending does not break.||ii) Brown or grey & hard and break on bending|
|iii) The protective superficial layer epidermis forms the outer covering.||iii) Thy epidermis is replaced by corky layer or bark.|
|iv) Stomata are present throughout its length for gaseous exchange||iv) It develops dot- like pores called lenticels for gaseous exchange|
|v) Buds often naked||v) buds are often protected by scales|
|vi) They consist of primary permanent tissues.||vi) They consist of secondary permanent tissues.|
11.How do various leaf modifications help plants?
Ans. The normal functions of leaves are photosynthesis, respiration & transpiration. Besides these function the leaves have to perform other functions. Hence, they modify themselves in different ways as follows:-
(i)TENDRIL:- In some plants the entire leaf or part of it gets modified to coiled thread like structure called tendrils . Tendrils help the plants to climb up eg. pea, clematis.
(ii)SPINES:- In many plants the leaves or their apices are modified into thin sharp & pointed structure known as spines. They help in defence eg. opuntia, yucea. Etc.
(iii)SCALE LEAVES:- In onion mostly all the leaves are present in the form of fleshy scale leaves.
(iv)PITCHER:- It is the modification of leaf in insectivorous plant in which the lamina takes the form of a pitcher, apex in the form of a lid to trap the insects. There are number of digestive glands in the inner walls of the pitcher. These glands secrete a fluid which digests insects eg. Nepenthes.
(v)PHYLLODE :- The petiole becomes green, flattened & leaf like & is called phyllode eg. Australian Acacia.
12.Differentiate between Tuber & Bulb.
|TUBER (POTATO)||BULB (ONION)|
|i) Stem is very well developed||i) Stem is reduced to a disc.|
|ii) Adventitious roots absent||ii) Adventitious roots are present.|
|iii) Potato plant can bear numerous tubers||iii) Only one bulb develops in one onion plant.|
|iv) Food is stored in stem.||iv) Food is stored in fleshy scale leaves.|
|v) Food stored in the form of starch.||v) Food not stored in the form of starch.|
|vi) Buds external||vi) Buds internal|
|vii) Distinct nodes & internodes are present||vii) Nodes & internodes are indistinct|
|viii) Scale leaves found in the nodal region are very small.||viii) Scale leaves are fleshy & conspicuous|
|ix) The tuber is a total stem.||ix) The bulb is a shoot.|
13.Give four types of underground stem & give examples for each.
Ans. FOUR TYPES OF UNDERGROUND STEMS:-
(i)RHIZOME:- The stem is prostate, thickened & grows horizontally under the soil. Stem is much branched & each branch ends in terminal bud. Adventitious roots arise in profusion eg. fern, water lily, turmeric.
(ii)BULB :- Highly condensed & discoidal stem. Terminal bud in the centre produces aerial root that produces flowers. From base of stem adventitious roots develop. Leaves store food material. Terminal bud & scale leaves are present eg. onion garlic.
(iii)CORM:- Condensed form of rhizome with auxiliary buds & scale leaves. It is swollen base of underground stem axis. Nodes & internodes are present eg. zimikand, saffron, colocasia.
(iv)TUBER:- It grows horizontally & swells at the apex. Adventitious roots arise during sprouting. It has many buds that grow into new plants eg. potato, Halianthus
14.Compare Trailer, runner & sucker.
|i) Semi aerial creeping stem it does not roots at intervals||i) Prostate, sub-aerial stem. It is green & root at intervals.||i) Underground non green stem.|
|ii) Does not participate in perennation||ii) Does not participate in perennation.||ii) Helps in perennation.|
|iii) No help in vegetative propagation.||iii) Helps in vegetative propagation.||iii) Helps in vegetative propagation.|
15.What do you mean by “modification of roots”. Describe some of the modifications of tap roots giving suitable example.
Ans. The functions other than normal functions of roots eg. fixation, absorption & conduction are to be carried out by roots. These are called modifications of roots. The modifications of top roots includes:-
(a).FUSIFORM:- This roots is swollen in the middle & tapers at both the ends gradually eg. Raddish.
(b).NAPIFORM:- The shape of this root becomes almost spherical but tapers abruptly downward eg. turnip.
(c).CONICAL:- The shape becomes cone like eg. carrot.
(d).TUBEROUS:- It is a swollen root having no specific shape eg. mirablis, Trichosanthes.
16.What is aestivation? What are its different types give examples.
Ans. (a)valvate:-petals or sepals meet eacf other at the edge.
Arranged without overlapping
(b)Twisted:-petals or sepals show overlapping is done by one margin of each petal over the margin of adjacent petals
(c)IMBRICATE:- If margins of sepals or petals overlaps one another but not in a particular direction eg. cassia & gulmohar.
(d)VEXILLARY:- There are five petals the largest overlaps the two lateral petals which in turn overlaps the two smallest anterior petals eg. bean, pea.
17.Describe the sub- aerial modifications of stem.
Ans. The main function of sub-aerial modification of stems is vegetative propagation. They are of following types:-
(i)RUNNERS:- These stems are long & thin with branches which creep along the ground & develop root at the nodes. Many such branches are produced by mother plant & they spread out in all direction. They may break off & start living as independent plants eg. oxalis, doob grass.
(ii)STOLON:- This is also a thin lateral branch which arises from the base of stem. It grows upward & bent down again developing roots at the tip & producing a bud. The bud grows into a new plant eg. mint, strawberry.
(iii)OFFSET:- This is a thickened horizontal branch arising in the axil of a lower leaf. It is a short branch which produces a cluster of leaves above & tufts of roots below. Offset can break off from mother plant & start living independent life. Eg. Water lettuce, water hyacinth.
(iv)SUCKER:- The sucker is a lateral branch which develops from underground part of stem. It grows upward in obliquely manner & directly give rise to new plant eg. banana, pineapple.
18.Explain with examples. What are the different modifications of adventitious roots?
Ans. MODIFICATIONS OF ADVENTITIOUS ROOTS:-
(i)TUBEROUS:- It is swollen root & shapeless occurring singly eg. sweet potato.
(ii)FASCICULATED:- Several tuberous roots arise from the same place in a cluster eg. dahlia, Asparagus.
(iii)BEADED ROOTS:- These roots have swollen parts at frequent intervals eg. portulaca, vitis.
(iv)PROP ROOTS:- These are pillars like roots hanging vertically downward from aerial branch of plant eg. Banyan tree.
(v)STILT ROOTS:- The roots are short which grow obliquely from near the base of the main stem & they provide anchorage & support to the stem eg. sugarcane, maize, sorghum.
(vi)PARASITIC ROOTS:- These roots penetrate into the host cells & absorb nutrients from host tree eg. cuscutta.
(vii)ASSIMTLATORY ROOTS:- Adventitious roots in certain plants become green to carry out photosynthesis & are called assimilatory roots eg. tinospora, trapa.
5 Marks Questions
1.Describe various stem modifications associated with food storage, climbing and protection.
Ans. Stem Modifications:
• Fur food storage Ginger (Rhizome), potato (Tuber), Onion (Bulb). Colocasia (Corm).
• For climbing (support Skin tendril (cucumber, grapevine, watermelon)
• For protection Thorn (Bougainvillea, Citrus, Drama)
Description Refer page 6 NCERT, Text Book of Biology for Class X
2. Give the distinguishing features of gynoccium of family Fabaccace, Solanaccac and Liliaccae. Draw floral diagrams of Fabaccac and Solanaccac.
Family Fabaceae: Ovary superior monocarpellary, unilocular w many ovules, style single.
Faniily Solonaceae: Ovary superior, bicarpellary, syncarpous, bilocular,. placenta swollen with many ovules.
Fam Liliaceae: Ovary superior, tricarpellary syncarpous, trilocular with many ovules, axile placentation
3.Describe the various types of placentations found in flowering plants & represent diagrammatically.
Ans. The various types of placentations found in flowering plants are:-
(i)MARGINAL:- Ovary one chambered and ovules lies along the margin of the ovary eg. pea & gram
(ii)PARIETAL:- Ovary one chambered and ovules lies at the level of the fusion of the fusion of the carpels. Eg. mustard.
(iii)AXILE:- Ovary many chambered and ovules are attached to the central column eg. onion & lemon.
(iv)FREE CENTRAL:- Ovary one chambered and at the centre it bears many ovules eg. Dianthus, Primula.
(v) BASAL:- Ovary one chambered and ovules develop on the thalamus eg. sunflower.
(vi)SUPERFICIAL:- Ovary is multilocular & syncarpous. Ovules develop on the minor surface of the ovary. Eg. Nymphea.
Types of placentation :(a) Marginal (b) Axile (c) Parietal (d) Free central (e) Basal
4.What is a flower? Describe the parts of typical angiospermic plants with the help of a diagram.
Ans. The flower can be defined as a modified shoot bearing nodes & modified floral leaves. It consists of following parts:-
(i).CALYX:- It is the outermost whorl of flower. It is green. Leaf- like structure it may be polysepalous (sepals free) or gamosepalous (sepals united) calyx may be regular or irregular.
(ii).COROLLA:- It is the second whorl of the flower inside the sepals. The petals are usually brightly coloured. The insects are attracted due to colour of the petals so they help in pollination. The narrow stalk like lower portion of petal is called a claw & the upper extended portion is known as limb.
(iii).ANDROECIUM:- It represents as male reproductive parts. It consists of stamens in each stamen there are three parts:-
(a)Anther:- Knob like bilobed structure containing pollen grains. Each lobe contains two chambers called pollen sac.
(b)Connective:- A strip of tissue, which connects the anther lobe is called connective.
(c)Filament:- a slender stalk by which anther lobes are attached is called filament.
(iv).GYNOECIUM:- It is the female part of the flower it is made up of three parts
(a)Stigma:- upper part of pistil which receives pollen grains
(b)Style: – The stalk between stigma & ovary.
(c).Ovary:- basal part containing ovules.
5.Describe the aerial modifications of stem.
Ans. AERIAL MODIFICATIONS OF STEM INCLUDES:-
1.STEM TENDRIL:- Stem tendrils are thin leafless slender & spirally coiled structures which develop from auxiliary buds. They help the plant such as cucumber, water melon, grape vine etc. to climb.
2.STEM THORN:- sometimes the auxiliary buds grows into hard, woody straight & pointed structures called thorns. It arises in the axil of leaf or at the tip of branch. Sometimes thorn bears leaves also. They are commonly found on plants eg. citrus durantha, Bougainvillea etc.
3.PHYLLOCLADE:- It is the green flattened or cylindrical stem which takes the form and function of leaf. They contain chlorophyll & carry photosynthesis. They have many nodes & internodes. Their true leaves are reduced, spines or scales. It is commonly found in xerophytic plants eg. opuntia, epiphyllum etc.
4.CLADODE:- This is a phylloclade of limited growth which develops, from the node of the stem or branch & in the axil of a scale leaf eg. asparagus, Ruscus, asculentus etc. cladodes are green flat & leaf like structures which carry on photosynthesis.
5.BULBILS:- This is a modified vegetative or floral bud meant for the production of a new plant. It detaches itself from mother plant & grows into an independent plant. Bulbils are found in oxalis, Agava american, Lilium etc.
NCRT TEXTBOOK QUESTIONS SOLVED
1.What is meant by modification of root? What type of modification of root is found in the:
(a) Banyan tree
(c) Mangrove trees
Soln.Roots of some plants change their shape and structure and become modified to perform certain functions other than absorption and conduction of water and minerals. It is called modification of roots. Roots are modified for support, storage of food and respiration, etc.
(a) Root modification in banyan tree : In banyan tree, the root modifies to form prop roots. Prop roots arise from branches and enter the soil. Thus, they provide mechanical support to densely branched, huge trees.
(b) Root modification in turnip : The
modification of root found in turnip is napiform for food storage. The upper portion of these fleshy roots is inflated or swollen which tapers towards the lower end.
(c) Root modification in mangrove trees : In mangrove plants, i.e., plants growing in saline marshes, the branches of tap root come out of the ground and grow vertically upwards showing negative geotropism. These roots are called pneumatophores. They help to get oxygen for respiration.
2.Justify the following statements on the basis of external features:
(i) Underground parts of a plant are not always roots.
(ii) Flower is a modified shoot.
Soln. (i) Underground parts of plant are not always roots because sometimes the stem also becomes underground and gets modified into various forms to perform different functions of storage, vegetative propagation, perennation, etc. Underground modifications of stems are tuber, rhizome, corm and bulb. The underground stems can be distinguished from roots externally by the presence of nodes and internodes, axillary buds, scale leaves etc. and by absence of root cap and root hairs.
(ii) Flower is the reproductive part of the angiospermic plant and it is defined as the modified shoot because (a) like shoot, flower develops from an axillary or rarely terminal bud. (b) flowers may get modified into fleshy buds or bulbils, (c) A transition from foliage leaves to floral leaves is found in Paeonia. (d) Nymphaea shows transition from sepals to petals and petals to stamens, (e) In Passiflora and Cleome long intemodes occur below gynoecium and stamens.
3.How is a pinnately compound leaf different from a palmately compound leaf?
Soln.The compound leaves may be of two types, pinnately compound leaf and palmately compound leaf. In pinnately compound leaf, a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf as in neem. Pinnately compound leaf may be of different types as unipinnate, bipinna te, tripinna te and decompound. In palmately compound leaf, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton. Palmately compound leaf may be of different types as unifoliate, bifoliate, trifoliate, quadrifoliate and multifoliate.
4.Explain with suitable examples the different types of phyllotaxy.
Soln.Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is usually of three types – alternate, opposite and whorled. In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower plants. In opposite type, a pair of leaves arises at each node and lie opposite to each other as in Calotropis and guava plants.
If more than two leaves arise at a node and form a whorl it is called whorled phyllotaxy as in Alstonia.
5.Define the following terms:
(a) aestivation (b) placentation
(c) actinomorphic (d) zygomorphic
(e) superior ovary (f) perigynous flower (g) epipetalous stamen.
Soln. (a) Aestivation : The mode of arrange¬ment of accessory floral organs (sepals and petals) in relation to one another in floral bud is known as aestivation. The main type of aestivation are valvate, twisted, imbricate, and vexillary.
(b) Placentation : The arrangement of ovules within the ovary is known as placentation. The placentation are of different types namely, marginal, axile, parietal, basal, and free central.
(c) Actinomorphic : When flower can be divided into equal radial halves in any radial plane passing through the centre, it is said to be actinomorphic, e.g., mustard, Datura etc.
(d) Zygomorphic : When a flower can be divided into two similar halves only in one particular vertical plane, it is said to be zygomorphic, e.g., pea, gulmohar, bean, Cassia.
(e) Superior ovary : In hypogynous flower, the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, brinjal.
(f) Perigynous flower: If gynoecium is situated in the centre and other parts of the flower are
located on the rim of the thalamus almost at the same level, it is called perigynous. Here ovary is half superior, e.g., peach, plum.
(g) Epipetalous stamen : When stamens are attached to the petals, they are called epipetalous stamens e.g., brinjal.
(a) Racemose and cymose inflorescence
(b) Fibrous root and adventitious root
(c) Apocarpous and syncarpous ovary
(a) Differences between racemose and cymose inflorescence are as follows:
(b) Differences between fibrous and adventitious roots are as follows :
(c) Differences between apocarpous and syncarpous ovary are as follows :
7.Draw the labelled diagram of the following:
(i) Gram seed (ii) V. S. of maize seed.
(i) Gram seed.
(ii) V.S. of maize seed.
8.Describe modifications of stem with suitable examples.
Soln. Stems are modified to perform different functions. Underground stems of some plants are modified to store food in them. They also act as organs of perennation to tide over conditions unfavourable for growth. Different modifications of stem are :
(i) Underground modifications
(i)Underground modifications of stem are discussed as follows:
(a)Tuber: It is the branch of main stem which accumulates or stores food in it and swells up, e.g., Solarium tuberosum (potato).
(b) Rhizome: It is a branched, prostrate horizontally growing stem having nodes and internodes. On the nodes sessile scale leaves are formed, e.g., Carina, Zingiber officinale (ginger), Curcuma domestica (turmeric) etc.
(c) Corm: This is a spherical,
branched, vertically growing thick underground stem with more diameter than length, e.g., Crocus sativus (saffron), Gladiolus, Colocasia esculenta (arvi) etc.
(d) Bulb: In bulb the stem is highly reduced and can be seen only as a disc-like structure bearing numerous fleshy scaly leaves, e.g., Allium cepa (onion), Allium sativum (garlic) etc.
(ii) Subaerial modifications : Subaerial part of stem grows horizontally on the ground while some part remains underground. Vegetative propagation takes place by means of these. They may be of following kinds.
(a) Runner: It grows prostrate on the surface of soil. It develops at the base of erect shoot called crown. A number of runners arise from one erect shoot which spread in different directions. Each runner has one or more nodes which bear scale leaves and axillary buds, e.g., Cynodon (doob grass).
(b) Stolon: The nodes of horizontally growing underground stem give rise to branches which come out of the soil, e.g., Fragaria (strawberry).
(c) Sucker: Suckers are formed from the node of underground stem. Sucker comes up obliquely in the form of leafy shoot, e.g., Mentha (mint).
(d) Offset: Stem consists of thick and short intemodes. The branches are formed from the main stem and upper portion of each branch bears a group of leaves while the lower portion bears the roots. Each branch is capable of growing as an independent plant after separating from the parent plant, e.g., Eichhornia (water hyacinth), Pistia, etc.
(iii)Aerial modifications : The aerial portion of stem is modified to perform different functions, e.g., climbing, protection, food manufacturing, etc. It may show following types of modifications:
(a) Twinners : The stem is long, flexible and sensitive which can coil around an upright support like a rope, e.g., Ipomoea, Convolvulus.
(b) Climbers : The stem is weak and flexible but is unable to coil around an upright support by itself. It requires the help of clasping or clinging structures. Accordingly, climbers are of four types : root climbers, e.g., Betel; tendril climber, e.g., Passiflora; scramblers, e.g., Bougainvillea and lianas, e.g., Bauhinia.
(c) Phylloclade: The stem performs the function of photosynthesis. The stem modifies into green fleshy leaf-like
structure having distinct nodes and intemodes. Leaves of such plants are reduced into spines in order to prevent loss of water, e.g., Opantia (prickly pear), Euphorbia.
(d) Cladode: It is similar to phylloclade with only one internode, e.g., Asparagus.
(e) Thorn: Stem is modified into stiff, pointed unbranched or branched structures which have lost their growing point and become hard, called as thorns, e.g., Bougainvillea,Pomegranate, Citrus, etc. They perform defensive function.
(f) Tendrils : These are thread like sensitive structures which can coil around a support and help the plant
in climbing, e.g., Cucurbita.
(g) Bulbils: In some plants vegetative buds or floral buds modify into a swollen structure called bulbil. It separates from the parent plant and on approach of favourable condition gives rise to a new plant, i.e., it is an organ of vegetative reproduction, e.g., Agave, Oxalis.
9.Take one flower each of the families Fabaceae and Solanaceae and write their semi-technical description. Also draw their floral diagram after studying them.
Soln.Family Fabaceae (e.g., Pisum sativum) Systematic position:
Class – Dicotyledoneae
Series – Calyciflorae
Order – Rosales
Family – Fabaceae
Habit: herb. Root: tap, branched, with root nodules.
Stem: herbaceous, climbing.
Leaves : pinnately compound, leaf base pulvinate, stipulate, venation reticulate.
Flower : bisexual, zygomorphic, irregular, hermaphrodite, white or pink, complete, hypogynous to perigynous.
Calyx : sepals five, gamosepalous, ascending, imbricate aestivation, campanulate calyx tube.
Corolla : petals five, polypetalous, vexillary aestivation, papilionaceous, consisting of a posterior standard or vexillum two lateral wings or alae, two anterior ones forming a keel.
Androecium : 10 stamens in two bundles (diadelphous) of (9) + 1, anthers dithecous (bilobed), basifixed, introrse.
Gynoecium : ovary superior, monocarpellary, unilocular with many ovules, marginal placentation, style bent and long, stigma simple and-hairy.
Fruit : legume; seeds one to many, non- endospermic.
Floral formula :
Family Solanaceae (e.g., Solanum nigrum) Systematic position:
Class Subclass Series Order Family
Habit: herbs Stem : herbaceous, aerial, erect, cylindrical, branched.
Leaves: alternate, simple, exstipulate, venation reticulate.
Flower : ebracteate, ebracteolate, bisexual, actinomorphic, white, hypogynous.
Calyx : sepals five, gamosepalous, persistent, valvate aestivation.
Corolla : petals five, gamopetalous, valvate. aestivation.
Androecium : stamens five, epipetalous, polyandrous, anthers large, bithecous and basifixed.
Gynoecium : bicarpellary, syncarpous,
ovary, obliquely placed carpels in the flower, bilocular, axile placentation, placenta swollen with many ovules.
Fruits : berry with persistent calyx.
Floral formula :
10.Describe the various types of placentations found in flowering plants.
Soln.Placenta is a parenchymatous cushion present inside the ovary where ovules are borne. The number, position, arrangement or distribution of placentae inside an ovary is called placentation. The placentation are of different types namely, marginal, axile, parietal, basal and free central.
(i)Marginal placentation : The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, e.g., pea.
(ii)Axile placentation : When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is said to be axile, e.g., china rose, tomato and lemon.
(iii)Parietal placentation : The ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum, e.g., mustard and Argemone.
(iv)Free central placentation : When the ovules are borne on central axis and septa are absent, as in Dianthus and primrose the placentation is called free central.
(v)Basal placentation: The placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.
11.What is a flower? Describe the parts of a typical angiosperm flower.
Soln.Flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. A typical flower has four different kinds of whorls arranged successively on the swollen end of the stalk or pedicel, called thalamus or receptacle. These are calyx, corolla, androecium and gynoecium.
Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs. In some flowers like lily, the calyx and corolla are not distinct and are termed as perianth. Some flowers have both androecium and gynoecium and are termed hermaphrodite flowers while some flowers have only one of these two whorls.
Calyx : The calyx is the outermost whorl of the flower and its units are called sepals. Generally, sepals are green, leaf like and protect the flower in the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous (sepals free).
Corolla : Corolla is composed of petals. Petals • are usually brightly coloured to attract insects for pollination. Like calyx, corolla may also be free (polypetalous) or united (gamopetalous). The shape and colour of corolla vary greatly in plants. Corolla may be tubular, bell-shaped, funnel-shaped or wheel-shaped.
Androecium : Androecium is the male reproductive part of the flower. It is composed of stamens. Each stamen which represents the male reproductive organ consists of a stalk or a filament and an anther. Each anther is usually bilobed and each lobe has two chambers, the pollen-sacs. The pollen grains are produced in pollen-sacs. A sterile stamen is called staminode.
Gynoecium : Gynoecium is the female reproductive part of the flower and is made up of one or more carpels. A carpel consists of three parts namely stigma, style and ovary. Ovary is the enlarged basal part, on which lies the elongated tube, the style. The style connects the ovary to the stigma. The stigma is usually at the tip of the style and is’ the receptive surface for pollen grains. Each ovary bears one or more ovules attached to a flattened, cushion-like placenta. When more than one carpel is present, they may be free (as in lotus and rose) and are called apocarpous. They are termed syncarpous when carpels are fused, as in mustard and tomato. After fertilisation, the ovules develop into seeds and the ovary matures into a fruit.
12. How do the various leaf modifications help plants?
Soln.Leaves perform various functions besides photosynthesis and thus they are modified into different forms such as –
(i)Leaf tendrils: The different parts of a leaf are modified into tendrils which help the plant in climbing up. Parts of leaf modified into tendrils include stipules e.g., Smiiax ; petiole e.g., Clematis ; leaf apex e.g., Gloriosa ; leaflets e.g., Pisum; whole leaf e.g., Lathyrus.
(ii)Leaf spines: Either for the protection of plant or to lessen the rate of transpiration in xerophytic plants, the leaves modify into sharp, pointed spines. Parts of leaf modified into leaf spines include stipules e.g., Zizyphus; leaf margins e.g., Argemone; leaf apex e.g.r Yucca; entire leaf e.g., Berberis.
(iii)Phyllode: Petioles modify into leaf¬like green, photosynthesising structure e.g., Parkinsonia, Acacia auriculiformis.
(iv)Scale or protective leaves : The leaves modify into hard scaly leaves which protect the vegetative bud by covering them, e.g., Ficus, Artocarpus, Casuarina, etc.
(v) Leaf hooks : They help in climbing e.g., Bignonia.
(vi)Leaf roots : A leaf transforms into roots for balancing on water e.g., Salvinia.
(vii)Leaf pitchers : Leaf is modified into pitcher e.g., Nepenthes (insectivorous), Dischidia (non-insectivorous).
(viii)Leaf bladder: The leaves modify to form bladder like structure which trap insects and then it is closed by a valve present on the mouth of bladder e.g., Utricularia (bladderwort).
(ix) Leaf tentacles: The leaf of sundew plant, Drosera bear minute hairs which have shinning, sticky substance at their tips (tentacles). When any insect sits on the leaf, it is covered by these hairs.
13. Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants.
Soln. The arrangement of flowers on the floral axis is termed as inflorescence. A flower is a modified shoot wherein internodes do not elongate and the axis gets condensed. The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. Depending on whether the apex gets converted into a flower or continues to grow, two major types of inflorescence are defined – racemose and cymose. In racemose type of inflorescence the main axis continues to grow, the flowers are borne laterally in acropetal succession. In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipeta! order.
14. Write the floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and axile placentation.
Soln. The floral formula for actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and
axile placentation is:
15.Describe the arrangement of floral members in relation to their insertion on thalamus.
Soln. In a typical flower, the floral members like calyx, corolla, androecium and gynOecium are arranged over the thalamus! Based on the position of calyx, corolla and androecium in respect to ovary on thalamus, the flowers are described as hypogynous, perigynous and epigynous ones. In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal. If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior or sub superior, e.g., plum, rose, peach. In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and gets fused with it; the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.