Effects of different levels of phosphorus on sunflower seedling root growth and protective enzyme activity

This experiment employed high yield and strong resistance variety ‘WWW-178'and edible variety ‘Chengpai 233'sunflowers as materials and studied the influences of low phosphorus stress on sunflower root growth and activities of protective enzymes.All test sunflowers were grown in pots by using Hoagland basic nutrient solution as control and 60% phosphorus concentration Hoagland solution as treat-ment.The results showed that root length was more sensitive to phosphorus concentration.The root length of two varieties was significantly lower than control during treatment time continued,but the dry weight of foot end and root-shoot ratio were significantly higher than control.The activities of superoxide dismutase(SOD)and catalase(CAT)of ‘WWW-178'seedling leaves had no significantly change under different concentration phosphorus,while the activity of peroxidase(POD)significantly increased.The activities of SOD and CAT obviously decreased in‘Chengpai 223'seedling leaves under low phosphorus stress after 40 days,but the activity of POD increased.The enzymes activity of sensitive variety decreased under low phosphorus stress,‘WWW-178'has stronger resistance than ‘Chengpai 223'under 60% phosphorust.It is suggested that‘WWW-178'sunflower is suitable cultivated in acid soils with low phosphorus content.