Genotypic variation in growth and metabolic responses of perennial ryegrass exposed to short-term waterlogging and submergence stress

Physiological mechanisms of waterlogging (WL) and submergence (SM) tolerance are not well understood in perennial grasses used for turf and forage. The objective of this study was to characterize growth, antioxidant activity and lipid peroxidation of perennial ryegrass (Lolium perenne) exposed to short-term WL and SM. 'Silver Dollar' (turf-type cultivar), 'PI418714' (wild accession), 'Kangaroo Valley' (forage-type cultivar) and 'PI231569' (unknown status) varying in growth habits and leaf texture were subjected to 7 d of WL and SM in a growth chamber. Plant height was unaffected by WL but was significantly reduced by SM for all grasses except PI418714. The SM treatment caused greater reductions in leaf chlorophyll and total carotenoid concentrations. Substantial declines in water-soluble carbohydrate concentrations were found in the shoots and roots under SM, particularly in Kangaroo Valley and PI231569, two relatively fast-growing genotypes. Significant increases in malondialdehyde concentrations were noted in the shoots and roots of all genotypes exposed to WL and SM, but to a greater extent in Kangaroo Valley and PI231569 under SM. Shoot activities of catalase (CAT) and peroxidase (POD) increased under SM, more pronounced in Silver Dollar and PI418714, two relatively slow-growing genotypes. Waterlogging or SM stresses decreased root activities of superoxide dismutase, CAT, POD and ascorbate peroxidase, especially for Kangaroo Valley and PI231569. The results indicated that maintenance of antioxidant activity and carbohydrate and minimization of lipid peroxidation could contribute to better waterlogging or submergence tolerance of perennial ryegrasses.