Deferral of Senescence and Abscission by Chemical Inhibition of Ethylene Synthesis and Action in Bean Explants

Abstract
Three compounds known to inhibit ethylene synthesis and/or action were compared for their ability to delay senescence and abscission of bean explants. Aminoethoxyvinylglycine (AVG), AgNO3 and sodium benzoate were infiltrated into the petiole explants. Their effect on abscission was monitored by measuring the force required to break the abscission zone, and their effect on senescence was followed by measuring chlorophyll and soluble protein in the distal (pulvinus) sections. AVG at concentrations between 1 and 100 .mu.M inhibited ethylene synthesis by .apprx. 80-90% compared to the control during sampling periods of 24 and 48 h after treatment. This compound also delayed the development of abscission and senescence. Treatment with AgNO3 at concentrations between 1 and 100 .mu.M progressively reduced ethylene production, but to a lesser extent than AVG. The effects of AgNO3 on senescence and abscission were quite similar to those of AVG. Sodium benzoate at 50 .mu.M to 5 .mu.M did not inhibit ethylene synthesis during the first 24 h, but appreciably inhibited ethylene synthesis 48 h after treatment. It also delayed the development of abscission and senescence. The effects of AVG, Ag+ and sodium benzoate suggest that ethylene could play a major role in both the senescence induction phase and the separation phase in bean explants.