Exogenously Application Of 24-epibrassinolide Improved Salt Stress Tolerance Of Perennial Ryegrass

In order to study the effect of exogenously applied 24-epibrassinolide (EBR) on the responses of perennial ryegrass (Lolium perenne L.) under salt stress, two varieties of perennial ryegrass Accent and Evening shade were used as plant materials. Seedings were treated with EBR under salt stress, physiological indexes such as proline, malondialdehyde, soluble sugar, protein, H2O2 contents and antioxidant enzyme activities were measured. Evening shade was chosen to futher study the effect of EBR on mature turf. Four concentrations of EBR (0,0.1,10,1000 nM) were sprayed on perennial ryegrass turf. Osmotic adjustment and antioxidant defense system again were investigated. Results are as following: 1. Under salt stress, exogenous EBR application significantly promoted salt tolerance by increased the content of proline, soluble sugar and soluble protein, decreased H2O2 and MDA content, which have positive effects on osmotic adjustment and decrease the oxygen damage from salt stress. Meanwhile, EBR further increased the activities of SOD and APX, but have little influence on the CAT and POD activity, which indicated that SOD and APX plays a major role in antioxidant enzymes system of plant in the process of removing of the reactive oxygen. Results also show that EBR treatment have more effects on the physiological indexes in Evening Shade, includes proline, H2O2, MDA, SOD, APX,which indicated that Evening Shade is more sensitive in response to EBR.2. According to the above results, Evening shade as the plant material were pretreated with different concentrations of EBR (0,0.1,10,1000 nM) under salt stress. Results show that the concentration of 10 nM,1000 nM EBR significantly increased the leaf relative water content, decreased the electrolyte leakage under salt stress, alleviated the membrane peroxidation damage in plant. EBR treatment significantly (P< 0.05) increased the content of proline, soluble sugar, soluble protein which provide better protection for plants under salt stress, the increasing is significantly at lOnM EBR treatment. Results also found that proline played a positive role in plants to resist salt stress. EBR reduce the accumulation of Na+ and increased Ca2+ content compared to salt treatment, which is conducive to the ion balance inside the plant, slow down the osmotic stress and ion poisoning. However, it just have little influence on K+ except for the 10 nM EBR treatment.3. Similar to the results in the seedlings, EBR treatment significantly (P< 0.05) decreased the content of H2O2 and MDA in Evening Shade, promoted the activity of SOD, APX and CAT, which proved that the activity of SOD, APX played a positive role in proving the plant salt resistance in response to EBR treatment. EBR also significantly (P< 0.05) increased AsA and GSH content, AsA showed more sensitive response in different concentrations of EBR treatment. These results indicated that exogenous EBR showed protective effects on perennial ryegrass under salt stress condition and 10 nM was the most effective concentration. The low concentration of 0.1 nM EBR just markedly increased the proline and AsA content and had no effects on other indicators.