Answer: Abscission of Leaves
Notes: This question is might have trapped almost all of you. The option A which etymologically linked to the question would trap you. We should note that Abscisic acid plays any significant role in leaf abscission is unfortunately not proved. The hormone is also called Dormin and its major functions are inhibition. But abscission of leaves is something better explained by Auxin-ethylene roles. Kindly surf the web and try to find out, if I am right. Inhibition of growth and maintenance of the dormancy of buds are the most striking effects of ABA. ABA activity alone is not enough to keep the dormancy of buds up in the long term though. Further, ABA is an efficient inhibitor of germination and occurs in high concentrations in dormant seeds. The role ABA has during the abscission of fruits and leaves is largely unknown. Though both cases seem to be governed by similar mechanisms (Auxin-Ethylene to a great extent) has ABA nearly no effect on the abscission of leaves while it shows a clear effect on fruit abscission. The role of Abscisic acid in abscission was a pharmacological artifact…applied AbA often induces ethylene biosynthesis.
