Year 3 science: Plants: understanding what plants need to grow -for Age 7-8 years

Roots

Roots support the plant, acting as an anchor to prevent it blowing away. The roots are also vital for nutrition. Thousands of tiny root hairs absorb (soak up) water and minerals from the soil. The water and minerals then travel up through the plant.

Stem

The stem is needed for support and for nutrition. It holds the plant up so it can get light, and it transports water and nutrients from the roots to the leaves and flowers. In trees, the stem is known as the trunk.

The important functions of a stem include:

• A stem carries out a number of functions essential for various processes such as photosynthesis.
• Provides a definite framework and structure to a plant which later develops into a tree.
• Support: Primary function of the stem is to hold up buds, flowers, leaves, and fruits to the plant. Along with the roots, a stem anchors the plants and helps them to stand upright and perpendicular to the ground.
• Transportation: It is the part which transports water and minerals from the root and prepared food from leaves to other parts of the plant.
• Storage: Stems are one of the storerooms of plants where the prepared food is stored in the form of starch. The stems of a few plants in the desert areas, such as Opuntia, get modified into thick, fleshy structures that store food and prevent excessive water loss due to transpiration.
• Reproduction: A few stems help in reproduction through vegetative propagation and also help to bear flowers and to produce fruits.
• Guards: Protects Xylem and phloem allowing them to perform their functions. The stem tendrils are spirally coiled and help the plant to climb support. The axillary buds also get modified into thorns that protect the plant from grazing animals.
• The stems of a few plants in the desert areas, such as Opuntia, get modified into thick, fleshy structures that store food and prevent excessive water loss due to transpiration.

Leaves

Leaves are needed for nutrition because they make food for the plant using sunlight and carbon dioxide from the air in a special process called photosynthesis.

A leaf consists of three main parts- petiole, leaf base and lamina.

1. The petiole keeps the leaf blade exposed to wind and cools the leaf.
2. The leaf base is a protruding part of a leaf.
3. The lamina of the leaf contains veins and veinlets that provide rigidity to the leaf blade and help in the transport of mineral nutrients.

Primarily, leaves have three main functions:

• Photosynthesis: Green leaves prepare food for plants by using water and carbon dioxide in the presence of sunlight. This process is called photosynthesis.
• Transpiration: Other than photosynthesis, leaves play a crucial role in the removal of excess of water from plants through tiny pores called stomata. This is the process of transpiration.
• Reproduction: Leaves of some plants helps in reproduction also. For e.g. leaves of Bryophyllum give rise to a new Bryophyllum plant.

Other Parts of Plants

The other parts of a plant include flowers and fruits.

Flowers

Flowers are needed for reproduction. Colour and scent attract insects. Pollen and eggs are produced by the flowers and these are needed to produce seeds. Flowers are the most beautiful and colourful part of a plant. They are the reproductive part of a plant. A flower has four major parts, namely,

• Petals: It is the colourful part of a flower which attracts insects and birds.
• Sepals: Sepals are green leafy parts present under petals and protect the flower buds from damage.
• Stamens: This is the male part of the flower consisting of anther and filament.
• Pistil: This is the female part of the flower consisting of stigma, style and ovary.

Fruits

Fruits are the main features of a flowering plant. It is a matured ovary that develops after fertilisation. Some fruits are developed without fertilization and are known as parthenocarpic fruits and the process is known as Parthenocarpy.

Thus, we see how different parts of a plant help in the growth and development of a plant. All the plant parts are beneficial and work in coordination with each other.

Water Transport in Plants

Water absorbed by the roots travels up inside the stem of the plant. From the stem, the water can enter the leaves and flowers, helping the plant to grow and be healthy by delivering essential minerals to where they are needed.