Effects of exogenous salicylic acid on physiological charac-teristics of Cocos nucifera L. young seedlings under cold stress

ObjectiveThe present study was conducted to investigate the effects of exogenous salicylic acid(SA)on physiological indexes of Cocos nucifera L. young seedlings of different varieties under cold stress in order to provide refe-rence for improving cold resistance of C. nucifera young seedlings and breeding new cold resistant C. nucifera varieties.MethodOne-year-old seedlings of Wenye 78F1,Wenye II,Wenye III and Wenye IV were used as materials,and sprayed with different concentrations of SA(100.0,150.0,200.0 and 250.0 mg/L). Activities of superoxide dismutase(SOD),cata-lase(CAT),peroxidase(POD)and contents of malonaldehyde(MDA)and proline(Pro)in leaves under cold stress of 4℃for 1-5 d were determined and analyzed.ResultThe results showed that,after being treated with four different concentra-tions of SA at 4℃,SOD,CAT,POD activities and Pro content of C. nucifera young seedlings were higher than those of clear water control(CK)within 5 d,and these indexes increased firstly and then decreased on a whole. But MDA content was lower than that of CK,decreasing firstly and then increasing. SOD,CAT,POD activities and Pro content in seedling leaves of Wenye 78F1,Wenye II,Wenye III and Wenye IV at 4℃were the highest on the 2nd day,significantly higher than those in CK and in other SA treatments(P<0.05,The same below). But MDA content was the lowest,significantly lower than that in CK and under other concentrations of SA. Among which,SOD,CAT and POD activities and Pro concent of Wenye 78F1 young seedlings were the highest and MDA concent was the lowest. When treated with different concentra-tions of SA at the same cold stress time,SOD,CAT and POD activity and Pro content of C. nucifera young seedlings of various varieties treated by 150.0 mg/L SA were the highest and the MDA content was the lowest,among which,SOD, CAT and POD activity and Pro concent of Wenye 78F1 seedlings were the highest and MDA concent was the lowest on the whole. The effects of 200.0 and 250.0 mg/L SA treatments were weaker than those of 150.0 mg/L SA treatment. There were no obvious changes in the five cold resistant indexes in seedlings treated with 100.0 mg/L SA.ConclusionSpraying 150.0 mg/L exogenous SA can improve cold resistance of C. nucifera young seedlings,it especially has optimal effects on Wenye 78F1 cold resistance. Therefore,this method can be applied in breeding cold resistant C. nucifera seedlings and cold resistant C. nucifera new varieties .