Question

Arrangement of leaves on the stem branches is called--------
A. Ptyxis
B. Vernation
C. Prefoliation
D. Phyllotaxy

Answer 1

Hint: The leaves arise from the nodes on the stem. They are arranged in a particular order like alternate whorls. The arrangement has been the inspiration for a number of architecture and paintings.

Complete Answer:
- The basic arrangement of leaves on the stem may be opposite or alternate. This arrangement of leaves on the stem is called phyllotaxy, where phyllon means stem and taxis means arrangement. The term was coined by Charles Bonnet. Phyllotaxy is the term used to define the arrangement of leaves on the stem.
- There are mainly three types of leaf arrangement- opposite (leaves arise at the same level at the opposite side of each other), alternate (each leaf arises at different points on the stem) and whorled(when several leaves arise at the same node).
- Ptyxis: It is the way in which the leaves are folded in bud.
- Vernation: It is the way in which the leaf is arranged in bud before it opens.
- Prefoliation: It is the arrangement of leaves within a vegetative bud.

Thus the correct answer is (D). Arrangement of leaves on the stem branches is called phyllotaxy.

Note: The leaf arrangement is controlled by the plant growth hormone auxins in the certain areas of meristem. When leaves begin to develop, the auxins flow towards it. This leads to a self propagating system.