BIOLOGY [5 Mark Question Answer]

Sometimes, the complete leaf or a part of the leaf is modified to perform a special function.
Some of these modifications include:
1. Leaf tendril:
In the case of certain weak stemmed plants, leaves or leaflets are modified into wiry, coiled structures called tendrils. They are sensitive to touch. As they touch any object, they coil around it and support the plant to climb up. Eg., Sweet pea (upper leaflets are modified into tendrils).
2. Spines: Leaves are modified into spines to reduce water loss, like cactus. In prickly poppy, leaves bear spines on the margin.
3. Scale leaves: In some plants, like onion and ginger, thin and dry or thick and fleshy scale leaves are present. Their function is to protect buds.

Parallel venation:
In this type of venation, veins run parallel to each other, e.g., banana, grass, maize, and wheat leaves (monocot plants).Reticulate venation: In this type of venation, veins and veinlets are irregularly distributed in the lamina, forming a network, e.g. peepal, mango and guava leaves (dicot plants).

Simple leaf:
In a simple leaf, the lamina is undivided and is a single piece, e.g. mango, banana, banyan, etc.compound leaf: In a compound leaf, the leaf blade or lamina is divided into smaller units called leaflets e.g., rose.

The arrangement of veins and veinlets on the lamina of a leaf is called venation. The venation is of two types:
(a).Reticulate venation:Veins are arranged like a network,
e.g. Leaves of mango, Peepal, and guava.
(b). Parallel venation: Veins run parallel to each other.
e.g. Leaves of banana, grass.