The Effect Of Exogenous Salicylic Acid On Salt Tolerance Of Perennial Ryegrass

Salicylic acid (SA) is a plant growth regulator which can enhance biotic and abiotic stress tolerances of plants. The objects of this study were to examine whether the exogenous SA could enhance salt tolerance of perennial ryegrass(Lolium perenne L.; PRG) and herein the possible physiological mechanism. Under hydroponic conditions, split-plot design was used in this experiment, the main plots were NaCl stress, including two levels:0 mM and 250 mM; the sub plots were salicylic acid, including four levels:0 mM,0.25 mM,0.5 mM and 1 mM. The results indicated that:1. Salicylic acid reduced the damage caused by salt stress in perennial ryegrass, promoted the growth of the tufgrass. Application of salicylic acid at 0.25 mM and 0.5 mM can reduce the the MDA content, the electrolyte leakage and H2O2 content of perennial ryegrass under salt stress, showed that salicylic acid alleviated the membrane lipid peroxidation caused by salt stress, protected the integrality of cell membrane; the relative water content and chlorophyll content of perennial ryegrass under salt stress were increased by 0.25 mM and 0.5 mM salicylic acid treatment; under salt stress, when compared with the control, the turfgrass quality increased by 26.8% in 0.25 mM salicylic acid treated perennial ryegrass, showed that salicylic acid could promote the growth of perennial ryegrass under salt stress, and improve salt tolerance.2. Salicylic acid increased the photosynthetic rate and stomatal conductance, and nitrate reductase activity of perennial ryegrass under salt stress. Photosynthetic rate and stomatal conductance were improved significantly by 0.25 mM of salicylic acid treatment under salt stress or normal conditions, the highest increase of up to 187%; 0.5 mM salicylic acid treatment significantly enhanced photosynthetic rate of perennial ryegrass under salt stress, however, the effect of 0.5 mM salicylic acid treatment on stomatal conductance was not as significant as that of SA treatment at 0.25 mM; salicylic acid treatment at 1 mM significantly inhibited stomatal opening under salt stress. These results indicated that salicylic acid through the regulation of photosynthetic characteristics to improve the salt tolerance of perennial ryegrass. but only 0.25 mM and 0.5 mM concentration had significant effect, application of SA at 1 mM caused the inhibition.3. Salicylic acid enhanced the ability of antioxidant system in salt-stressed perennial ryegrass. SOD, POD, CAT, APX activities of perennial ryegrass could be significantly improved by 0.25 mM and 0.5 mM of salicylic acid treatments under salt stress, while the CytCu/ZnSOD, APX, POD gene has been significantly upregulated. Thesed results showed that salicylic acid enhanced antioxidant capacity of perennial ryegrass under salt stress in enzyme activity and gene expression two levels, enhanced the salt tolerance of perennial ryegrass.In summary, application of salicylic acid alleviated the salt-caused damage in perennial ryegrass, increased photosynthetic capacity and enhanced the antioxidant enzymes activity and gene expression, promoted growth of perennial ryegrass, improved salt tolerance.