What hormones infuence the shedding of leaves, and how do they work?

Question

What hormones infuence the shedding of leaves, and how do they work?

Answer 1

Abscisic acid (ABA), named for its effect on leaf abscission, reverses the effect of growth-stimulating hormones (auxin, gibberellins, cytokinin). In leaf and fruit drop ABA counters the auxin that acts to retain the them during growth and development.

ABA is involved in dormancy beyond dropping leaves it inhibits shoot growth but does not have as much affect on roots or may even promote growth of roots even in dormancy. It keeps seeds dormant until growth conditions are met.