Metabolic Responses to Heat Stress under Elevated Atmospheric CO2 Concentration in a Cool-season Grass Species

Heat is a major factor limiting growth of C 3 grass species. Elevated CO 2 may mitigate the adverse effects of heat stress or enhance heat tolerance. The objective of this study was to determine metabolic changes associated with improvement of heat tolerance by elevated atmospheric CO 2 concentration in tall fescue ( Festuca arundinacea ). Plants (cv. Rembrandt) were exposed to ambient day/night temperature (25/20 °C) or heat stress (35/30 °C) and ambient CO 2 concentration (400 ± 10 μmol·mol −1 ) or double ambient CO 2 concentration (800 ± 10 μmol·mol −1 ) in growth chambers. Turf quality (TQ), shoot growth rate, and leaf electrolyte leakage results demonstrated that heat stress at ambient CO 2 concentration inhibits turf growth and reduces cell membrane stability, whereas heat-stressed plants under elevated CO 2 concentration exhibit improved TQ, shoot growth rate, and membrane stability. Plants exposed to heat stress under elevated CO 2 exhibited a significantly greater amount of several organic acids (shikimic acid, malonic acid, threonic acid, glyceric acid, galactaric acid, and citric acid), amino acids (serine, valine, and 5-oxoproline), and carbohydrates (sucrose and maltose) compared with heat-stressed plants at ambient CO 2 . The increased production or maintenance of metabolites with important biological functions such as those involved in photosynthesis, respiration, and protein metabolism could play a role in elevated CO 2 mitigation of heat stress damage. Therefore, elevated CO 2 conditions may contribute to improved heat stress tolerance as exhibited by better TQ and shoot growth of heat-stressed plants. Practices to harness the power of CO 2 may be incorporated into turfgrass management for plant adaptation to increasing temperatures, particularly during summer months.