35. The hormone responsible for leaf epinasty(curvature) in flooding-sensitive plants such as tomato is
(1) abscisic acid                                 (2) auxin
(3) ethylene                                  (4) gibbrellic acid

Correct answer: (3) Ethylene

Explanation:

• Leaf epinasty (downward curvature of leaves) in flooding-sensitive plants such as tomato is primarily caused by ethylene.

• Flooding or waterlogging induces ethylene production, which triggers epinastic bending as an adaptive response to low oxygen stress.

• Abscisic acid is more involved in stress responses and stomatal closure, not epinasty.

• Auxin can influence various growth responses but is not the main hormone causing epinasty under flooding stress.

• Gibberellic acid mainly regulates growth processes like stem elongation, not leaf epinasty.

• Ethylene acts as a crucial signal in plants experiencing flooding by regulating morphological changes, including leaf epinasty, to improve survival under hypoxic conditions. This hormone-mediated adaptation helps maintain gas exchange and mitigate damage due to excessive water.