Differential responses of tall fescue and zoysiagrass to heat and drought stress

Heat and drought are major abiotic stresses limiting turfgrass growth. The objective of this study was to determine the relative effects of drought and heat on cool-season tall fescue (Festuca arundinacea) and warm-season zoysiagrass (Zoysia matrella). Mature sod of tall fescue ('Barlexus') and zoysiagrass ('Manila') were transplanted from field plots to pots filled with sandy loam soil in growth chambers. Plants of both species were subjected to three treatments for 30 days: Control plants were watered daily to field capacity and maintained at 20 degrees C for tall fescue and 30 degrees C for zoysiagrass; drought stress - plants were subjected to drought stress by withholding irrigation while maintained at the same temperatures as the respective control for each species; and heat stress - plants were exposed to 35 degrees C for tall fescue and 45 degrees C for zoysiagrass. For both tall fescue and zoysiagrass, turf quality and photochemical efficiency (Fv/Fm) declined while electrolyte leakage (EL) increased during 30 days of drought or heat stress. The decline in turf quality and Fv/Fm and the increase in EL occurred earlier and were more severe for tall fescue than zoysiagrass under both drought and heat stress conditions, and for heat-stressed plants than drought-stressed plants for either tall fescue or zoysiagrass. The changes in all three parameters were particularly significant for tall fescue under heat stress conditions. Our results suggested that heat stress was more detrimental to photochemical reactions and cell membrane stability than drought stress for both species, and tall fescue was more sensitive to both heat and drought stress than zoysiagrass, particularly heat stress.