Question

Lateral branches of stem are
A. Endogenous in origin
B. Exogenous in origin
C. Both (A) and (B)
D. None of the above

Answer 1

Hint: Lateral branches of the stem arise from the axillary buds. These buds are present in the axil of the leaves and arise exogenously.

Complete answer:
To answer this question, we should know about the axillary buds, exogenous, and endogenous origin.
To start with, we all know that a typical vascular plant has three parts: roots, stems, and leaves. Roots are the underground parts while the stem is usually aerial and bear branches and leaves.
If we look at a twig of a vascular plant, we can see several branches bearing the leaves. A stalk, called the petiole, attaches leaves to the twig. Axil of leaves has buds. Now, axil means the angle between a petiole and the stem. Since these buds are present in the axil of leaves, they are called axillary buds.
The axillary buds can serve two main functions: it can develop into a lateral branch or a flower. Here, one should know that plants have meristematic tissues that can divide and form the new plant parts. The apical meristem that is present in the apex of the shoot is called shoot apical meristem. As leaves develop from the shoot apical meristem, some of the meristematic cells give rise to axillary buds.
Now, we know that the lateral branches of the stem arise from the axillary buds. But, if the branches arise from the superficial tissues, they will be said to have an exogenous origin. On the other hand, a structure that is derived from the tissues located deeply is said to have an endogenous origin.
The axillary buds of the stem have an exogenous origin as they are derived from the cortex. Therefore, the lateral branches that arise from these axillary buds would also have an exogenous origin.

So, the correct answer is B. Exogenous in origin.

Note:
One should know that lateral branches of roots are endogenous in origin. Stem also have terminal buds that do not form branches. Axillary buds are also called lateral buds.