CARBON-DIOXIDE EXCHANGE-RATE AND CHLOROPHYLL CONTENT OF TURFGRASSES TREATED WITH FLURPRIMIDOL OR MEFLUIDIDE

Plant growth regulators (PGRs) are being used increasingly for high ma intenance turf production. A greenhouse and growth chamber study was c onducted to determine the effect of two PGRs, mefluidide and flurprimi dol, on the carbon dioxide exchange rate, chlorophyll content, and spe cific leaf weight of annual bluegrass and creeping bentgrass. Rate-res ponse and time course studies were conducted. In the rate-response stu dy, increasing flurprimidol rates caused a linear decrease in the carb on dioxide exchange rate (CER). Mefluidide had no effect on the CER in the rate-response experiment but did cause a significant drop in the CER at 4 and 8 days after treatment (DAT) in the time course study. Bo th PGRs increased chlorophyll content at 16 DAT in the time course stu dy. In the rate-response study, chlorophyll content displayed a quadra tic response to an increasing mefluidide rate. The 0.28 kg ha(-1) rate of mefluidide increased the chlorophyll content to 46 mu g cm(-2) fro m 21.5 mu g cm(-2) for control plants. Both PGRs increased specific le af weight, although for flurprimidol the effect was significant only a t the 0.1 level of probability. PGRs decreased the CER and increased t he chlorophyll content and specific leaf weight for both species teste d. The physiologic effects measured were short lived, and so the physi ologic significance of these changes is difficult to determine without further research.