Various methods are available for improving drought resistance in turfgrasses. Several studies have reported the application of plant growth regulators as an effective method for reducing drought stress effects. A factorial experiment based on a randomized complete block design with three replications was performed in 2011 and 2012 to investigate the effects of the gibberellic acid (GA) inhibitors trinexapac-ethyl (TE) and drought stress on the physiological responses of wheatgrass (Agropyron desertorum) and tall fescue (Festuca arundinacea) to drought stress. The foliage of wheatgrass and tall fescue were sprayed with 1.95 ml L-1 TE at 0.113 % a.i. 14 days prior to and at the beginning of the drought stress. Both Tetreated and untreated plants were placed to well-watered and no water circumstances for 45 days in field conditions. Results indicated that drought stress reduced turf quality (color, density, and uniformity), relative water content (RWC), and total chlorophyll content, but increased proline content, electrolyte leakage (EL), malondialdehyde (MDA) and soluble sugar content (SSC) in both species. Superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) activities in the two turfgrass species initially increased transiently, but declined subsequently. TE application increased SOD, APX, POX, and CAT activities, especially under drought stress conditions. Correlation analysis showed that there were significantly positive correlation between turf quality and RWC and negative correlation between turf quality and proline content, EL, MDA and SSC in both species. The use of TE seems to have enhanced resistance to drought stress in both species by improving proline, SSC and antioxidant activities.
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