The Enhancement of Drought Stress Tolerance of Kentucky Bluegrass by Prohexadione-Calcium Treatment

Kentucky bluegrass ( Poa pratensis L.) is one of the most widely used turfgrasses for home lawns, golf courses, parks, and athletic fields in temperate climates. Oxidative stress caused by drought stress is a major limiting factor for grass cultivation in arid and semi-arid regions. The objective of this study was to investigate whether Prohexadione-Calcium (Pro-Ca) may play a role in promoting drought tolerance in kentucky bluegrass. Pro-Ca was exogenously applied as a foliar spray at the rate of 0, 7.5, 15 or 25 mg a.i./m2 to well established kentucky bluegrass under wellwatered (100 of field capacity) or drought-stressed (70 and 40% of field capacity) conditions. The effect of Pro-Ca on the growth physiology, drought stress response, antioxidant activity, and lipid peroxidation of kentucky bluegrass exposed to drought stress was measured during 28 days at 7 days interval. Pro-Ca treated kentucky bluegrass exposed to drought stress had higher relative water content (RWC) and turf quality, and lower electrolyte leakage and malondialdehyde (MDA) content as membrane integrity indicators, compared with untreated plants. Pro-Ca application significantly increased the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities under well-watered and drought conditions, but this increase is more evident in drought stressed plants. Pro- Ca application at 15 mg/m2 was found to be more effective in alleviating drought stress damage in kentucky bluegrass. The results from this study suggest that Pro-Ca enhanced drought stress tolerance in kentucky bluegrass by maintaining higher RWC and membrane stability.