DescriptionHeat stress is a key factor that inhibits the growth and development of cool-season plant species and accelerates leaf senescence, which is characterized by premature chlorosis of leaves. Bentgrasses (Agrostis sp.) are widely used perennial on golf courses and putting greens and are sensitive to prolonged exposure to high temperatures. As climate change steadily increases the average global temperature, cool-season plants, such as bentgrass, will undergo longer periods of heat stress and symptoms will be more severe. In order to suppress heat-induced leaf senescence, it will be necessary to understand the biochemical mechanisms regulating heat stress and promoting heat tolerance in bentgrasses so that a reduction in quality and performance may be mitigated. The objectives of this research were to identify the biochemical factors associated with heat tolerance in bentgrasses and how various plant growth regulators may inhibit damage associated with heat stress. To accomplish this, multiple studies were conducted that 1) examined whether chlorophyll enzyme metabolism is associated with heat-induced leaf senescence in various bentgrass lines differing in heat tolerance, 2) identified how exogenously applied amino acids and ammonium nitrate control heat-induced leaf senescence in creeping bentgrass (A. stolonifera) by regulating chlorophyll metabolism and 3) amino acid metabolism, 4) evaluated how glutamate inhibits heat-induced leaf senescence in creeping bentgrass by acting on amino acid metabolism, 5) assessed the ways in which treating creeping bentgrass with a sterol or 6) a carotenoid pigment suppresses heat-induced leaf senescence by promoting membrane health through the enzymatic antioxidant system, 7) explored how application of an ethylene inhibitor or 8) a morphactin reduce heat-induced leaf senescence in creeping bentgrass by altering chlorophyll metabolism, and 9) investigated how protease inhibitors enhance heat tolerance by repressing protein degradation. The findings of this research may be utilized in the future to develop heat-tolerant bentgrass lines that maintain a stay-green phenotype under high temperatures and will provide turf managers with strategies for enhancing plant health during heat stress.