Effects And Mechanisms Of Nitric Oxide And Salicylic Acid On Alleviating Salt Stress In Winter Wheat Plants

Wheat is one of the most important crops in coastal saline alkali soil.As key growth stages,wheat plants during germination and seedling formation are very sensitive to salt stress.Then,it is important to improve seed germination and early seedling formation to increase wheat grain yield of coastal saline soil area and protect national food security.This research with wheat?Triticum aestivum L.?as the material,using exogenous NO and SA as the regulatory substance,to study the effects of exogenous NO and/or SA on growth,physiological characteristics and yield of wheat under 120mM NaCl stress by hydroponic culture and pot experiment,in order to clarify the possible mechanisms of enhancing salt-tolerancein plants..The results are showed as follows:1.Under hydroponic culture condition,the effect of 120 mM NaCl on shannong 22 was less than jimai 22.Add 0.1 mM of SNP could improve chlorophyll content and antioxidant enzyme activities of two varieties of Wheat Seedlings under salt stress,so as to promote photosynthesis and improve wheat resistance;reduce membrane peroxidation induced by salt stress,increase the content of proline,soluble sugar,soluble protein and ascorbic acid in wheat plants,so as to promote osmotic adjustment;maintain a higher K/Na value in plants,alleviate ion toxicity caused by excessive Na.The effect of SNP on jimai 22 was more significant than that on shannong 22 under salt stress.2.Different concentrations of SA have different effects in alleviate the salt stress.The effect of low concentration and high concentration of SA on alleviate Salt stress was not obvious.However,200?M SA could significantly improve the chlorophyll content,root activity and root plasma membrane H⁺-ATPase activity,promote the uptake of mineral elements and the selective absorption of Na,maintain the normal K⁺/Na⁺ratio,so as to promote seedling growth;significantly increase antioxidant enzyme activity to reduce the accumulation of ROS;increase proline and soluble protein content to alleviate lipid peroxidation damage.The results showed that 200?M SA could significantly alleviate the damage caused by salt stress to wheat seedlings.3.Compared with application of SNP or SA alone,the application of SA+SNP had the better effect on alleviating salt stress of wheat,and the 1/2?SA+SNP?treatment had the most significant effect.The application of 1/2?SA+SNP?could significantly reduce ROS accumulation induced by salt stress,MDA content and electrolyte leakage;improve the wheat chlorophyll content,proline content and soluble protein content,antioxidant enzyme activity;increase root activity to promote the absorption and transportion of mineral elements,so as to improve the dry matter accumulation of wheat seedlings.The above results showed that NO and SA showed a positive synergistic effect on alleviating salt stress of wheat seedlings.4.On the pot experiment,compared with application of SNP applied into soil directly or soaking seeds in SNP solution,SNP prepared into controlled release fertilizer was more effective to alleviate the effects of salt stress on the growth and physiological characteristics of wheat seedlings.And to a certain extent,these three methods could improve the salt resistance of wheat seedlings by promoting seedling growth,improving antioxidant enzymes activity,regulateing ion homeostasis and other ways;also could promote the growth of wheat seedlings by regulating absorption of nutrients.The results showed that exogenous NO could improve the salt tolerance of wheat.5.On the pot experiment,both SNP and SA could alleviate the effects of salt stress on the growth and production of wheat,and there were some differences between the effects of different methods.Slow release SNP and slow release SA had the better effects.That may be they could release slowly SNP and SA in a long time.Slow release SNP and slow release SA significantly increased the chlorophyll content,antioxidant enzyme activity,proline and soluble protein content of leaves at different nodes?flag leaf,the second and third upper leaf?;decreased O₂^·-production rate,H₂O₂ and MDA content;inhibited the the absorption of Na,promoted N,P,K,Ca and Mg uptake and transport to the ground,and improved the yield of winter wheat in saline-alkali soil.