Physiological Mechanisms Of Ameliorating Effects Of KNO₃ On Salinity In Chenopodium Quinoa Willd.

Soil salinization is a factor limited the development of agriculture.Salt stress significantly limited crop growth and seed yield.How to improve the salt tolerance of crops and reduce the damage of salt stress to crops has always been a research hotspot of stress physiology.Previous studies had shown that exogenous nitrate can alleviate the damage of salt to crops.In order to explore the physiological mechanisms of KNO₃ improving salt tolerance of crops,quinoa（Chenopodium quinoa Willd.）was used as materials in this experiment.The effects of KNO₃（0,5,10,40,100 m M）on photosynthetic rate,ion balance and antioxidant capacity of quinoa were investigated under 200 m M NaCl.From the points of physiological characteristics,the mechanism of KNO₃ ameliorating the effects of salt in quinoa.The main results were as follows:Under salt stress,the application of KNO₃ improved the photosynthetic ability of quinoa.KNO₃ affected stomatal conductance by regulated stomatal open and close,and increased the electron transfer activity and the efficiency of primary light energy conversion under salt stress.The results showed that the SPAD,Pn,Gs and E of quinoa were increased by 14.80%（40 m M）,101%（40 m M）,101.21%（40 m M）,and 138.77%（10 m M）,respectively,when KNO₃ was applied.Exogenous use of KNO₃ enhanced the scavenging of reactive oxygen species,and reduced the oxidative damage of membrane lipids.The results showed that the activity of SOD,POD and CAT were increased by 38.01%（40 m M）,228.53%（5 m M）and 57.30%（100 m M）,respectively.The content of MDA was decreased by 9.85%（40 m M）.In addition,the ion imbalance of quinoa was regulated under the combined application of KNO₃ and NaCl.The selectived absorption in the roots of quinoa was enhanced because of competitive inhibition between K⁺and Na⁺.The accumulations of organic osmotic regulators were promoted.The experimental data showed that:exogenous application of 10 m M KNO₃ reduced the content of Na⁺（young leaf）,Na/K（functional leaf）,Cl^-（root）and H₂PO₄^-（old leaf）were reduced by31.60%,41.32%,12.85%,and 18.73%,respectively.Moreover,the content of proline was increased by 64.16%under combined application of 40 m M KNO₃ and 200 m M NaCl.Based on the effects of KNO₃ on photosynthetic capacity,antioxidant capacity,ion balance and osmotic adjustment of quinoa,the growth parameters of quinoa were significantly improved.The RGR of seedlings was increased by 55.52%（5 m M）.The exogenous application of low concentration KNO₃ could alleviate water stress,improve the ratio of root to shoot,improve the absorption of water and mineral elements,and enhance the survival ability of plants under 200 m M NaCl.Secondly,exogenous application of low concentration KNO₃ could regulate stomatal opening,effectively improve transpiration rate,net photosynthetic rate and RGR of quinoa.Thirdly,exogenous application of low concentration of KNO₃ could increase the activity of antioxidant enzymes,and decrease the content of MDA,which effectively alleviated the oxidative damage caused by salt injury.Under stress conditions,KNO₃ can effectively improve the salt tolerance of quinoa,and promote plant growth.