Thursday, November 8, 2007 - 8:45 AM

Drought Responses of Kentucky Bluegrass and Creeping Bentgrass as Affected by Abscisic Acid and Trinexapac-ethyl.

Stephen McCann, Rutgers University Cooperative Extension, Rutgers University, 310 Buttonwood St., Mount Holly, NJ 08060 and Bingru Huang, Rutgers University, 19 Dudley Road, New Brunswick, NJ 08901.

The plant growth regulators abscisic acid (ABA) and trinexapac-ethyl [(4-cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid methyl ester] (TE), may affect turfgrass responses to drought stress through regulating shoot growth and water relations. The objectives of this study were (1) to investigate the effects of foliar application of TE and ABA on turf growth of two cool-season turfgrass species, Kentucky bluegrass (Poa pratensis L.) and creeping bentgrass (Agrostis stolonifera L.) exposed to drought stress; and (2) to examine water relations associated with changes in drought tolerance due to TE or ABA treatment. Bentgrass (cv. L-93) and Kentucky bluegrass (cv. Brilliant) plants were foliar sprayed with 0.8 L ha-1 Primo Maxx [1.95 mL L-1 (v:v); a.i. TE = 0.113] five times before exposure to drought or with 0.8 L ha-1 abscisic acid [1.95 mL L-1 (v:v)] weekly before and after exposure to drought in growth chambers. Drought stress was imposed by withholding irrigation until plants were permanently wilted. TE or ABA treatment maintained higher soil volumetric water content, leaf relative water content, and turf quality for a longer period of time during 28 d of stress exposure for both Kentucky bluegrass and creeping bentgrass compared to the untreated control. Leaves of TE-treated and ABA-treated plants in both species also had lower osmotic potential at 28 d of drought stress. Creeping bentgrass treated with TE or ABA and Kentucky bluegrass treated with TE exhibited significantly lower shoot vertical growth rates at the initiation of drought stress, but maintained higher growth rates during prolonged drought. Turf treated with TE or ABA also showed higher levels of photochemical efficiency for both species. Results suggest that TE or ABA application could prolong survival of turfgrass under conditions of drought stress by sustaining growth and photosynthetic activity during prolonged periods of drought stress through osmotic adjustment for retaining cellular hydration.