Question

The movement of auxin is largely
A) Acropetal
B) Basipetal
C) Lateral
D) Centripetal

Answer 1

Hint: Auxins are plant growth regulators firstly obtained from coleoptile tips of oat seedlings. It inhibits lateral buds and promotes the growth of apical buds, it promotes phototropism, flowering, initiation of the stem, etc. Indole 3 acetic acid is a type of natural auxin.

Complete answer: Auxin is a type of plant growth regulator produced at stem, buds and roots and is transported to other parts of the plant. Auxin contains a group of plant hormones. Some are synthetic example naphthalene acetic acid and 2-4 dichlorophenoxyacetic acid and some are natural such as indole 3-acetic acid and indole butyric acid. The main plant hormone present is indole 3 acetic acid. The movement of the stem is basipetal as it travels from the shoot apex towards the base. It also moves from the shadier part to the brighter part of the plant which makes the cell grow longer. Elongation occurs in the basipetal side due to auxins. Auxin to cytokinin ratio determines root or shoot formation. Auxin affects phototropism, the process in which plants follow the sun. Auxin causes changes in cells and bends the plant towards the sunlight
Functions of Auxin are as follows:
i. Apical dominance: The growth of lateral buds is inhibited and the growth of apical bud is promoted.
ii. Helps in the detachment of old dead leaves and fruits
iii. Also inhibits detachment of unripened fruits and young leaves.
iv. It promotes flowering in plants.
v. Promotes root growth in stem cuttings.
vi. Also used in plant propagation methods.
vii. Inhibits growth of weeds.
Hence, the correct answer is option B.

Note: Other types of plant growth regulators are gibberellins, cytokinins, abscisic acid and ethylene. Gibberellins regulate stem elongation and germination in plants, cytokinin regulates cytokinin promotes cell division, abscisic acid has an important role in the closing of the stomata on leaves and ethylene induces ripening of fruits.