Monday, November 13, 2006 - 1:30 PM

Physiological Effects of Trinxapac-ethyl on Bentgrass Adaptation to Summer Stress.

Stephen E. McCann and Bingru Huang. Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901

Previous research has shown inhibitory effects of trinexapac-ethyl [(4-cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid methyl ester] (TE) on shoot vertical growth in various turfgrass species.  The objective of this study was to determine whether applications of TE would enhance creeping bentgrass (Agrostis stolonifera cv ‘L-93’) tolerance to prolonged heat and drought stress by reducing water demand associated with retarded shoot vertical extension.  Plants were foliar sprayed with .8 L ha-1 Primo Maxx [1.95 ml L-1 (v:v); a.i. TE = .113] three times before exposure to combined drought and heat (35°C) in growth chambers.  Foliar application of TE significantly improved visual turf quality and maintained higher relative water content (RWC) during 21 d of stress exposure.  Rates of shoot vertical growth and canopy photosynthesis (Pn) in TE-treated plants were initially significantly lower, but Pn and growth rate were significantly higher when compared to the untreated control at 21 d of stresses.  Additionally, TE-treated plants maintained lower canopy evapotranspiration rate (ET) under control conditions (0 d), but higher ET at 21 d of stress. TE-treated plants showed no significant differences from the control in osmotic potential, and had significantly lower levels of total nonstructural carbohydrates (TNC).  These findings suggest that TE application was able to alleviate or delay stress injury, as demonstrated by maintenance of higher turf quality and physiological functions, which may be associated with slower shoot vertical growth and reduced water consumption.