Drought Responses of Perennial Ryegrass Treated with Plant Growth Regulators

Abstract

Plant growth regulators (PGRs) are used on golf course fairways, and may have positive or negative effects on turfgrass response to drought. Greenhouse and field studies in 1995 and 1996 evaluated perennial ryegrass (Lolium perenne L.) response to drought stress after PGR application. Turf was maintained under golf course fairway conditions, and received adequate water until PGR application; thereafter, irrigation was withheld. Trinexapac-ethyl was the only PGR evaluated that enhanced turfgrass quality during dry down in the greenhouse, had no deleterious effects on rooting, and suppressed canopy height for up to 2 weeks in the field. Ethephon enhanced quality during drought in the greenhouse, reduced root length density (RLD) in the field from 0- to 10-cm and 10- to 20-cm depths, but had no effect on canopy height. Mefluidide caused unacceptable chlorosis, reduced rooting at 0 to 40 cm, and suppressed canopy height. Paclobutrazol had negligible effects on ryegrass quality, rooting, and canopy height. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); N-{2,4-dimethyl-5-[[(trifluoromethyl)-sulfonyl] amino]phenyl} acetamide (mefluidide); (2RS,3RS)-l-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4,-triazol-l-yl) penta-n-3-ol (paclobutrazol); 4-(cyclopropyl--hydroxy-methylene)-3,5-dioxo-cyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).