Root development is promoted by
- abscisic acid
- auxin
- gibberellin
- ethylene
Answer
(4) ethylene
Solution
As per NCERT, ethylene promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.
∵ Abscisic acid is a growth inhibitor, and gibberellins mainly cause stem elongation (bolting) and increase in length of axis,
∴ root development (root growth and root hairs) is promoted by ethylene.
(Auxins also initiate rooting in stem cuttings.)
Answer: (4)