Question

Tendrils are
A. Stems modified to store the food
B. Stems modified into coiled wires
C. Stems modified into prop roots
D. Roots modified to perform photosynthesis

Answer 1

Tendrils are the modification of axillary buds (majority). We should at first have a brief idea about the bud and its types. The bud is defined as a young, immature, under-developed compact shoot. Two types of buds are taken into consideration:
Terminal bud: These buds are present at the tip of the growing shoot and also referred to as apical bud.
Axillary bud: The angle made between the leaves and the upper part of the stem is known as axil. The bud present in this junction is known as the axillary bud.

Complete answer:
The tendrils are coiled structures that help the plant in climbing purposes. The tendrils coil around the support structure and help the plant to grow erect. These are present in plants that are climbers, i.e., they have a weak stem.
These tendrils usually show a specific type of tropic movement known as Thigmotropism. It is the phenomenon of coiling of the tendril as soon as the tip of the tendril comes in contact with a support structure.
Now, stem tendrils are not necessarily modifications of only axillary buds. They may be the modifications of:
1. Axillary: E.g., Passiflora
2. Extra-axillary: E.g., Luffa
3. Apical bud: E.g., Grapevine
4. Floral bud: E.g., Antigonon

Hence, Option-B) Stems modified into coiled wires, is the correct answer.

Note:
Tendrils are of two types:
1. Stem tendrils
2. Leaf tendrils
We already have grabbed an idea about the stem tendrils. The leaf tendrils also serve the same function of support during climbing, the major difference is that they are modifications of leaves. They are present in plants like peas, sweet peas, etc.
The hormone auxin plays a vital role in the phenomenon of thigmotropism. We all know that in the stem, auxin causes growth. Now, as soon as the tendril tip comes in contact with a support structure, auxin gets deposited on the opposite side and stimulates uneven growth of one side that ultimately results in the coiling up of the tendril around the support structure.