Water Stress, Endogenous Ethylene, and Ficus benjamina Leaf Abscission

Ficus benjamina L. were subjected to 48 hr of polyethylene glycol (PEG)-induced water stress. Leaf abscission and concentrations of endogenous ethylene (C 2 H 4 ) in the leaves were monitored. Leaf abscission began 24 to 48 hr after stress initiation, and most abscission occurred within the first 24 hr after water stress was relieved. PEG-stressed plants lost 35% to 47% of their leaves by 120 hr after the experiment was initiated. Older leaves abscised first and remained green throughout the abscission process. Endogenous C 2 H 4 concentrations increased sharply and then declined during the first 6 hr of water stress. Endogenous C2H4 concentrations then increased gradually, and, by the time leaf abscission began, leaves contained 1.50 to 2.25 µl C 2 H 4 /liter.