Heat-induced Leaf Senescence in Creeping Bentgrass Suppressed by Aminoethoxyvinylglycine Involving Regulation of Chlorophyll Metabolism

Heat stress-induced or stress-accelerated leaf senescence is related to the accumulation of ethylene and loss of chlorophyll in cool-season grass species. The objective of this study was to determine whether foliar-spraying the ethylene inhibitor, aminoethoxyvinylglycine (AVG), may suppress heat-induced leaf senescence through effects on chlorophyll syn-thesis and degrading enzymes in creeping bentgrass (Agrostis stolonifera). Plants were maintained in environmentally controlled growth chambers under non-stress (22/17 & DEG;C day/night) or heat stress (35/30 & DEG;C day/night) temperature condi-tions for 25 days, and turf quality, electrolyte leakage, and chlorophyll content were measured to assess the extent of leaf senescence. Activities of chlorophyll-synthesizing and chlorophyll-degrading enzymes were quantified to determine whether AVG may regulate chlorophyll metabolism. Plants were foliar-sprayed with 25 mM AVG before and during heat stress at 7-day intervals. From 21 through 25 days of heat stress, AVG-treated plants had significantly higher turf quality and chlorophyll content, whereas electrolyte leakage was significantly lower in comparison with untreated controls. The activity of a chlorophyll-synthesizing enzyme, porphobilinogen deaminase, was significantly increased in AVG-treated plants at 21 days of heat stress. The activity of chlorophyll-degrading enzymes was significantly lower in plants treated with AVG from 14 through 25 days of heat stress for peroxidase, from 21 through 25 days of heat stress for pheophyti-nase, and at 25 days of heat stress for chlorophyllase. AVG may have suppressed heat-induced leaf senescence by regu-lating chlorophyll metabolic activities in cool-season grass species.