Effects of Salicylic Acid on the Antioxidant Activity of Barley Seedlings under Water Stress

Salicylic acid(SA) is a stress-related growth regulator in plants.In this study,the antioxidant activity of barley seedlings under water stress with 15% PEG solution was investigated.Before water stress,seedlings were pre-treated by exogenous salicylic acid with concentration from 0.05 to 0.50 mmol/L.Oxidative damage caused by water stress was estimated by the level of malondialdehyde(MDA) and protein carbonyl in seedling leaves.And the activity of antioxidant enzymes(SOD,CAT and APX) was also studied.Results showed that salicylic acid had dual effects: low concentration of salicylic acid(0.30 mmol/L) improved the water content of stressed seedlings,and reduced the oxidant damage caused by water stress,since the MDA content decreased compared with the control,and the content of protein carbonyl stabilized at a low level.However,high concentration of salicylic acid(0.30 mmol/L) aggravated the water deprivation of stressed seedlings,and greatly improved the level of MDA and protein carbonyl,thus causing more damage to seedlings under water stress.The reason for such effects was possible that high concentration of salicylic acid increased the accumulation of reactive oxygen species by regulating the activity of antioxidant enzymes.