4. Write a short note on the following.
a.
Phyllotaxy , venation
Answers
Venation- is the phenomenon of arrangement of veins in the lamina of the leaf surface. It is of three types, reticulate, parallel and furcate venation. In reticulate venation, veins form the network like structure. For example, leaves of dicot plants. In parallel venation, veins arise from the mid rib and run parallel.
In botany, phyllotaxis or phyllotaxy is the arrangement of leaves on a plant stem. Phyllotactic spirals form a distinctive class of patterns in nature. The term was coined by Charles Bonnet to describe the arrangement of leaves on a plant.
Explanation:
a) Phyllotaxy is the pattern of arrangement of leaves on the stem or branch of a plant. There are mainly three types: Alternate: When a single leaf arises from each node, in an alternate manner. ... Opposite: In this type, pairs of leaves arise at each node and lie opposite each other.
b) Leaf venation is the arrangement of veins in lamina of the leaf. Two types of venation are reticulate venation and parallel venation.
When the veins are irregularly distributed to form a channel, it is known as reticulate venation. When the veins are parallel and do not form a network, it is known as parallel venation.