Effects of water and nitrogen coupling on osmotic regulators and stress resistance physiological characteristics of flue-cured tobacco in Southern Shaanxi
Taking Yunyan99 as the material,the two-factor complete combination method was used to set up 3 soil moisture conditions including W1(soil relative water content 75%-85%),W2(soil relative water content 55%-65%),W3(soil relative water content 35%-45%);and 3 nitrogen application rates as N1(4 g),N2(5 g),N3(6 g),and a total of 9 treatments was set in pot experiments.After 15 days of vigorous growing stage of water control,catalase(CAT),peroxidase(POD),superoxide dismutase(SOD)activities and soluble protein,soluble sugar,proline(Pro),reduced glutathione(GSH),ascorbic acid(AsA),malondialdehyde(MDA),and superoxide anion radical(O2-)content were measured to explore the effect of water and nitrogen coupling on the osmotic regulators and stress resistance physiological characteristics of flue-cured tobacco.The results showed that under W3 conditions,nitrogen application could increase the soluble protein content by 42.86%and decrease the soluble sugar content by 12.32%compared with W3N1 treatment.Under W2 conditions,nitrogen application increased the activities of SOD and POD enzymes,which were 31.19%and 44.89%higher than those of W2N1 treatment,respectively.Under medium nitrogen conditions(N2),enzyme promotion effect exhibited,CAT activity in W1 or W2 treatment increased by 40.26%and 43.58%respectively,compared with W1N1 treatment.Compared with W1N1 treatment,the contents of Pro,GSH,MDA and O2-in tobacco leaves in W3 treatment were increased by 69.69%-222.49%,15.2%-89.36%,155.15%-162.37%and 24.89%-72.34%,respectively.The interaction analysis showed that the relative water content of soil had a greater effect on the activities of SOD and POD,and the contents of Pro,GSH,MDA,O2-and soluble sugar,while the nitrogen application rate had a greater effect on the content of soluble protein and CAT activity.The interaction effect of the relative water content and nitrogen application rate had a greater effect on the content of AsA.In general,the treatment with 6 g of nitrogen application had a better effect in promotion of antioxidant enzyme activity in flue-cured tobacco under mild water shortage,while the treatment with 5 g of nitrogen application had a better effect in increasing the content of osmotic regulators and antioxidant substances in flue-cured tobacco under severe water shortage.
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