Monday, November 13, 2006

Effects of Exogenous Cytokinin and Ethylene Inhibitor on Heat-Induced Leaf Senescence for Creeping Bentgrass.

Yan Xu and Bingru Huang. Dept. of Plant Biology & Pathology, Rutgers Univ., 59 Dudley Road, New Brunswick, NJ 08901

Cytokinins and ethylene are two major plant hormones that mediate signaling events involved in plant senescence. Our previous studies demonstrated a negative correlation between cytokinins and leaf senescence, and a positive correlation between ethylene and leaf senescence in creeping bentgrass. In this study, we hypothesize that exogenous application of cytokinin and ethylene inhibitor could compensate the change of cytokinin and ethylene during heat stress, resulting in delayed leaf senescence. Creeping bentgrass (A. stolonifera) cv. Penncross were exposed to either heat stress (35°C) or control temperature (20°C) for 35 days in growth chambers. Four pots in each chamber were sprayed with 50 ml of 25 mM cytokinin [trans-zeatin riboside (tZR)] at the beginning of each week. Another four pots were sprayed with 30 ml of 25 mM ethylene inhibitor [aminoethoxyvinylglycine (AVG)]. Four additional pots were sprayed with 35 ml of 35 mM ammonium nitrate at the same time to compare nitrogen effects with cytokinin and ethylene inhibitor on leaf senescence. Turf quality, chlorophyll and carotenoid content were measured at weekly intervals. A decline was observed in all three parameters for control plants after 14 d of heat treatment, whereas all parameters were maintained in the plants treated with tZR, AVG or ammonium nitrate.