Spraying KH2PO4 enhances the physiological activity of wheat flag leaves and roots to alleviate the damage caused by late spring coldness
[Objectives]In North China Plain,winter wheat often suffers late spring coldness during the jointing stage,foliar application of potassium dihydrogen phosphate(KH2PO4)is a widely used technology to improve the resistance.We investigated the regulatory effect of KH2PO4 on the physiological activities of functional leaves and roots of wheat after anthesis to provide theoretical support for disaster prevention and mitigation in wheat production.[Methods]A pot experiment was conducted under field condition,the wheat cultivar Yanong 19(YN)with strong cold resistance and Xinmai 26(XM)with weak cold resistance were selected as the test materials.The experiment was composed of spraying water without late spring coldness treatment(CK),spraying water with late spring coldness treatments(T1)and spraying KH2PO4 with late spring coldness treatment(T2).During the panicle differentiation stage to metaphase,the pots in T1 and T2 treatments were moved into artificial climate chamber and subjected to-4°C for 4 hours,then moved out.On the following day of cold treatment,water or KH2PO4 were sprayed as designed.At 7,14,21,and 28 days after anthesis,the SPAD values of flag leaves,root activity,and the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)and malondialdehyde content(MDA)in flag leaves and roots were measured.Principal component analysis(PCA)was employed to construct a comprehensive evaluation model for aboveground and root physiological activities in 28 days after anthesis under late spring coldness.[Results]Compared to CK in flag leaves,T1 treatment significantly reduced SPAD by 13.94%-35.03%,decreased the activity of SOD,POD,and CAT by 16.09%-32.84%,18.16%-50.10%,and 19.21%-75.40%,respectively,and increased MDA content by 29.55%-124.56%.And in roots,T1 treatment significantly reduced root activity by 44.00%-75.63%,decreased the activities of SOD and POD by 42.42%-86.11%,and 31.00%-66.67%,but increased MDA content by 61.54%-330.11%.Compared with T1 in flag leaves,T2 treatment significantly increased SPAD values by 7.90%-23.38%,increased SOD,POD,and CAT activity by 10.63%-32.28%,14.20%-57.20%,and 10.75%-115.56%,and decreased MDA content by 6.66%-36.08%.And in roots,T2 treatment significantly increased root activity by 44.71%-139.75%,SOD and POD activities by 12.13%-102.01%and 21.05%-146.61%,decreased MDA content by 12.01%-51.23%.The 9 physiological activity indexes were correlated closely with each other,and the ranking of the comprehensive physiological activity index was as follows:YNCK>XMCK>YNT2>XMT2>YNT1>XMT1.[Conclusions]Application of KH2PO4 could alleviate the damage of late spring coldness stress as it could enhance the relative chlorophyll contents of wheat flag leaves,root activity,and antioxidant enzyme activities,reduce MDA content in both flag leaves and roots,thus delaying the aging processes of flag leaves and roots.
potassium dihydrogen phosphatewheatlate spring coldnessroot activityantioxidant enzyme activity
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