IMPROVEMENT OF CHILLING RESISTANCE IN RICE BY APPLICATION OF AN ABSCISIC-ACID ANALOG IN COMBINATION WITH THE GROWTH RETARDANT TETCYCLACIS

The protective effect of a synthetic terpenoid analog of the plant hor mone abscisic acid (ABA) coded LAB 173711 applied alone or in combinat ion with the growth retardant tetcyclacis on chilling injury of rice w as studied under growth chamber, greenhouse, and field conditions. The compounds were applied as a foliar spray before and after the onset o f chilling treatment, as a substrate via the root system, and as a med ium for seed soaking. The ABA analog increased chilling resistance in a manner similar to ABA. Combination of the analog with tetcyclacis re vealed additive effects. Increased chilling resistance involved severa l processes: stomatal closure which reduced water loss during chilling , stabilization of the membranes, stabilization of the chlorophyll lev el, and stabilization of the root system. Possibilities for practical use of the compounds in rice production are discussed.