One of the most important problems in turfgrass industry is shortage of available water. New management strategies to improve turfgrass drought resistance is critical. Various cultural practices for water saving including the use of plant growth regulators (PGRs) have been used. Trinexapac-ethyl (TE) is a growth retardant commonly used on turfgrass that effectively reduces cool- and warm-season turfgrass growth and subsequent mowing requirements. TE competitively inhibits the conversion of GA20 to GA1 by 3-?-hydroxylase, markedly reducing leaf cell elongation. Several recent studies reported that TE also improved turfgrass tolerance to invironmental stresses. The objective of this study was to examine effects of different concentrations of TE on visual qulity and drought response of desert wheatgrass ( Agropyron desertorum L.) in a factorial complete randomized block design. Treatment included four concentrations 0, 6, 12 and 18 (mg.m -2 ) of TE and two levels of irrigations (no irrigation and full irrigation). For TE treatment, turf foliage was spryed 14 days before drought treatment began and on the day of drought stress imposed. The investigations of TE effects on wheatgrass visual quality showed that TE significantly enhanced turf color at the rate of 12 and 18 mg.m -2 compared with nontreated plants. The results indicated that plant height growth was inhibited by trinexapac-ethyl and was lower with higher application rate. The inhibition rate of plant height by 18 mg.m -2 was 46/4%. Under drought stress, TE-treated wheatgrass at the concentrations of 12 and 18 mg.m -2 maintaind turf color above the minimum acceptable level (6.0) until the early phase of drought stress. However, at the end of the drought period, no significant differences were observed between the treatments. Plants treated with 12 and 18 mg.m -2 rate of TE had significantly higher chlorophyll and carotenoid contents and leaf realative water content (RWC) than nontreted plants under drought stress. The lowest percentage of electrolyte leakage (EL) was observed at the rate of 12 mg.m -2 TE-treated plants. Notably, EL% was not significant between 12 and 18 mg.m -2 rates of TE. Proline content increased under drought stre however, TE had no significant effects on proline content under well-watered conditions or drought stress. Application of TE resulted in significant increase in antioxidant enzymes activities including catalase, ascorbat peroxidase and peroxidase. The highest level of all three enzymes activities was observed in plants treated by 12 mg.m -2 TE. It seems that TE at the rate of 12 mg.m -2 could enhance turf performance under drought conditions. Keywords: Wheatgrass, Drought stress, Trinexapac-ethyl, Antioxidant enzymes
