Question
The transverse section of a plant shows following anatomical features. [NEET (Sep.) 2020]
I. Large number of scattered vascular bundles surrounded by bundle sheath.
II. Large conspicuous parenchymatous ground tissue.
III. Vascular bundles conjoint and closed.
IV. Phloem parenchyma absent.
Identify the category of plant and its part.
(a) Monocotyledonous root
(b) Dicotyledonous stem
(c) Dicotyledonous root
(d) Monocotyledonous stem
Answer/Explanation
Ans. (d)
The transverse section of monocotyledonous stem shows following anatomical features:
The monocot stem have conjoint and closed vascular bundles, scattered in the ground tissue containing the parenchyma. Each vascular bundle is surrounded by sclerenchymatous bundle-sheath cells. Phloem parenchyma and medullary rays are absent in monocot stems.
Question
Water containing cavities in vascular bundles are found in [CBSE AIPMT 2012]
(a)sunflower
(b) maize
(c) Cycas
(d) Pinus
Answer/Explanation
Ans. (b)
In monocot stem like Zea mays, vascular bundles are conjoint, collateral and closed. In vascular bundles, the lowermost protoxylem vessels and xylem parenchyma cells dissolve forming a water containing schisolysigenous cavity called protoxylem cavity or lacuna or lysigenous cavity. Protoxylem cavity and protophloem may be absent in the smaller vascular bundles in maize.
Question
What is true about a monocot leaf? [CBSE AIPMT 1990]
(a) Reticulate venation
(b) Absence of bulliform cells from epidermis
(c) Mesophyll not differentiated into palisade and spongy tissues
(d) Well differentiated mesophyll
Answer/Explanation
Ans. (c)
Monocot leaves are characterised by parallel venation, leaves are isobilateral (both the surfaces equally green). amphistomatic with dumb bell-shaped guard cells. The upper epidermis possesses groups of larger sized thin walled vacuolate cells called bulliform or motor cells. Mesophyll is undifferentiated and consists of isodiametric cells enclosing intercellular spaces. Midrib region does not contain mesophyll and possesses number of parallel vascular bundles.
Question
Pith and cortex do not differentiate in [CBSE AIPMT 1988]
(a) monocot stem
(b) dicot stem
(c) monocot root
(d) dicot root
Answer/Explanation
Ans. (a)
In monocot stem, ground tissue is undifferentiated, thus endodermis, pericycle cortex and pith are not recognisable. Ground tissue consists of only parenchyma cells that store food.