Differential growth and physiological responses to heat stress between two annual and two perennial cool-season turfgrasses

Abstract

Heat stress is a major limiting factor for the growth of cool-season turfgrass species. The objective of this study was to compare growth and physiological responses to heat stress between annual and perennial cool-season grass species. Two annual grass species, annual ryegrass (Lolium multiflorum, cv. ‘Panterra’) and annual bluegrass (Poa annua, ecotype ‘Njpl’) and two perennial grass species, perennial ryegrass (Lolium perenne, cv. ‘Premier’) and rough bluegrass (Poa trivialis, cv. ‘Sabre’) were exposed to three temperature regimes in growth chambers: optimal temperature control (20/15°C day/night), moderate heat stress (10°C above the control), and severe heat stress (20°C above the control). Moderate heat stress did not cause significant physiological damages in any of the four grass species. Severe heat stress caused significant decline in turf quality (TQ), leaf relative water content (RWC), antioxidant enzyme (catalase) activity, membrane stability (EL), and resulted in severe membrane lipid peroxidation (MDA) in all four grass species. All these parameters in the two annual grass species were more responsive to severe heat stress, suggesting that the two annual species were less heat tolerant or more heat sensitive than the two perennial species. Differential heat responses between the two annual and two perennial grass species could be associated with the differences in the severity of leaf senescence, as manifested by TQ, EL, and MDA.