Various Roles of a Leaf in a Plant

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The Structure of A Leaf:

Leave shooting out of branches of the stem are green in color. On observing a leaf carefully, we can see that the place where the leaf is attached to the stem is called as petiole. A leaf is usually narrow towards its ends and broadened in the middle. The broader part of the leaf is called as lamina. A leaf consists of a thick vein called midrib which runs centrally from the petiole towards the end of the leaf. The midrib is responsible for transporting water and minerals from the stem to leaves. On looking carefully, the midrib is then branched into smaller veins on both sides of the leaves. This design of veins on the leaves is called as leaf venation.

The midrib is responsible for transporting water and minerals from the stem to leaves. On looking carefully, the midrib is then branched into smaller veins on both sides of the leaves. This design of veins on the leaves is called as leaf venation. The net-like design of veins in plants is called as reticulate venation and in grasses where the veins run parallel to mid-rib then the design is called as "parallel venation".

 

Figure 3.2.1Leaf venation

 

A.Reticulate venation           B. Parallel venation

 

Transpiration:

We know that leaves contain water as one of their components. To test the presence of water present inside the leaves, a test can be performed by wrapping a previously well-watered leaf inside a polythene (plastic) bag tightly and placing it under the sun for few minutes. It will be observed that there are few drops of water on the polyethylene bag.

This is because there is a loss of water from leaves in the form of water vapor. This phenomenon in plants is called as transpiration. Through this process, plants release a lot of water into the air, thus making the atmosphere cooler.

 

Photosynthesis:

 

Plants prepare their own food and hence are called as autotrophs. Plants prepare their food with the help of sunlight, carbon dioxide, water and chlorophyll, a substance responsible for their green color. This process is called as photosynthesis. During photosynthesis, carbon dioxide from the air is taken in and oxygen is given out. The food is stored in the form of starch in different parts of the plant.

It is interesting to learn that roots absorb water and minerals from the soil and stem conduct this from the roots to leaves and other parts of the plants. Amazingly, leaves prepare food through the process of photosynthesis and store it in the form of starch. In some plants, the starch is transported across the stem and stored in roots.

For example, potato, carrot, radish, tapioca. This indicates that stem is enabled with two-way access in the plant, transporting water and minerals up and collecting and transporting food for storage down to roots.

Various Roles of a Leaf in a Plant Assignment Help