The Study Of Effects Of Exogenous Nitric Oxide On Drought Resistance Of Flue-cured Tobacco Under Drought Stress

"Yu Yan 6" was selected as the experimental material in this study,The effects of exogenous NO(donor of SNP)on the growth,cell membrane permeability,MDA content,protective enzyme activity,osmotic substance content,photosynthetic characteristics and nutrient content of Flue-cured Tobacco under drought stress were studied by pot experiment.The effects of exogenous NO on drought resistance of flue-cured tobacco under drought stress were studied.The main results were as follows:1.The plant height,dry weight of the ground and underground part and root vigor of the tobacco obviously decreased under drought stress.The plant height,dry weight of the ground and underground part and root vigor of the tobacco increased with the application of 0.05 mmol·L-1-0.50 mmol·L-1 of SNP under drought stress.It indicated that spraying suitable concentration of SNP under drought stress was conducive to the growth,the accumulation of dry matter and the uptake of nutrients by roots of flue-cured tobacco.2.Under the condition of drought stress,the membrane permeability and MDA content of the leaf and root of flue-cured tobacco increased significantly,the activity of SOD and POD increased significantly,while the activity of CAT decreased,and the Pro,soluble protein and soluble sugar in the leaves and roots of flue-cured tobacco increased significantly.Spraying SNP could significantly reduce the cell membrane permeability and MDA content of flue-cured tobacco leaves and roots,the activity levels of SOD and POD in flue-cured tobacco gained further improvement,enhanced the activity of CAT,and further increased the content of Pro,soluble protein and soluble sugar in the leaves and roots of flue-cured tobacco.It indicated that NO could regulate and control the drought tolerance of flue-cured tobacco by increasing the antioxidant enzyme system and osmotic adjustment system of flue-cured tobacco,and reduce the permeability and MDA content of flue-cured tobacco.3.The response of the leaf and root of flue-cured tobacco to SNP concentration under drought stress was not consistent.0.25 mmol·L-1 of SNP had the greatest effect on the membrane permeability,POD activity and the content of MDA and Pro of Flue-cured Tobacco Leaves under drought stress.The maximum SNP concentration of the membrane permeability,POD activity and the content of MDA and Pro under drought stress was 0.50 mmol·L-1.These differences may be caused by different sensitivities of different organs to NO,or the changes of transformation ways of partial NO from the leaves to the root.Moreover,the effect of improving the drought resistance of flue-cured tobacco had a certain dose effect.In a certain range of SNP concentration(0~0.50 mmol·L-1),the drought resistance of flue-cured tobacco increased with the increase of SNP concentration.At a high concentration(0.75 mmol·L-1),the drought resistance decreased and even had some poisonous effect to the flue-cured tobacco.4.Under drought stress,the ratio of Chl.a,Chl.b,Chl and Chl.a/Chl.b decreased significantly.Under the drought conditions,there was a "noon break" phenomenon of photosynthesis in flue-cured tobacco,and the Pn,Gs and Tr of flue-cured tobacco decreased obviously,while Ci increased.It indicated that the decrease of photosynthetic ability of flue-cured tobacco was mainly caused by non-stomatal limiting factors.Under drought conditions,spraying 0.25 mmol.L-1 of SNP could significantly increase the total amount of Chl.a,Chl.b and Chl in flue-cured tobacco,increase the ratio of Chl.a/Chl.b.Meanwile,it increased the Pn,Gs and Tr of Flue-cured Tobacco under drought stress,while decreased the Ci.The Photosynthetic Diurnal variation curve changes from double peak curve curve to single peak curve,and the "noon break" phenomenon of photosynthesis vanishes.5.Under drought conditions,the content of N increased by 32.34%,the content of K+ increased by 19.43%,and the content of P,Ca,Mg,Fe and Mn decreased by 19.43%,17.74%,21.12%,30.90% and 20.78% respectively.0.25 mmol·L-1 of exogenous SNP significantly improved the content of P、K、Ca、Mg、Fe and Mn of the tobacco leaf under the drought condition,which showed that the flue-cured tobacco could improve the selective absorption of P、K、Ca、Mg、Fe and Mn under the drought stress,maintain the Cell ion homeostasis,and improve the drought resistance of flue-cured tobacco.