Naturally derived products that may enhance the functionality of fertilizers or other agricultural inputs are needed to reduce inputs associated with stress damage and increase the sustainability of turfgrass management. Damage to high-value creeping bentgrass (Agrostis stolonifera) turf areas caused by heat stress is a widespread problem. This study aimed to evaluate multiple, diverse treatments that may illicit antioxidant responses in plants, melatonin, rutin, and Si, when applied as foliar pretreatments to heat stress. Creeping bentgrass plants were grown in growth chambers at optimal (23 °C) or heat stress conditions (35 °C). Turfgrass quality, chlorophyll content, leaf electrolyte leakage, photochemical efficiency, lipid peroxidation, antioxidant enzyme activity, and fatty acid content were measured to determine the effects of foliar treatments on heat stress responses. Melatonin, Si, and rutin were all found to improve some or all of the physiological parameters measured in the study, but only melatonin and Si reduced lipid peroxidation, increased antioxidant enzyme activity, and altered fatty acid contents. Melatonin- and Si-treated plants had greater superoxide dismutase and peroxidase activity and increased the content of the unsaturated fatty acid, linoleic acid, in creeping bentgrass leaves during heat stress compared with controls. Rutin improved turf quality and reduced electrolyte leakage during heat stress, but the mechanism associated with these changes is unclear because no changes were found in antioxidant enzyme activities or fatty acids. Melatonin and Si treatment promoted antioxidant enzyme activity and linoleic acid content of leaves, which have been associated with the improved heat tolerance of creeping bentgrass plants.
The authors thank the Michigan Turfgrass Foundation, AgBioResearch of Michigan State University, and the National Institute for Agriculture and Residex Co. for funding and support of this research.
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