Effects Of Exogenous Nitrogen On Physiological Characteristics Of Walnut Seedlings Under Drought Stress

Walnut(Juglans regia)is an important economic tree species in China.It has a long history of cultivation and is widely planted.It is planted in Xinjiang,Gansu and Yunnan.In recent years,the research on the drought resistance of walnuts mainly involves the analysis of biomass,morphology,physiology and biochemistry,and there are few studies on the application of exogenous substances to improve drought resistance.In recent years,most studies on the improvement of drought resistance of plants by exogenous NO have focused on crops and herbaceous plants.There are few reports on woody plants.Therefore,this study analyzes the drought resistance mechanism of walnut seedlings under drought stress after spraying exogenous NO.The effects of different concentrations of exogenous NO on the physiological,biochemical,biomass and other indicators of walnut seedlings,combined with local precipitation,provided theoretical support for the research and cultivation management of local walnut drought resistance.In this study,the two-year-old grafted seedlings of 'Jinlong No.1' widely cultivated in southern Anhui Province were selected as the research object.According to the local rainfall,the irrigation amount was controlled,the irrigation stress was applied to the seedlings,and the exogenous NO donor SNP was sprayed.The seedling biomass,chlorophyll photosynthesis,fluorescence characteristics,physiological and biochemical indexes of different concentrations of SNP were measured,and the raw data of each index were comprehensively analyzed to analyze the influence of exogenous NO on these indicators,and the walnuts were increased for exogenous NO.The seedling drought resistance provides a theoretical basis.The following conclusions were obtained:1.Exogenous NO promoted the biomass of the plant height and ground diameter of 'Jinlong No.1' under drought stress.Under drought stress,the dry and fresh weight of the aboveground and underground parts of 'Jinlong No.1' was reduced.After SNP treatment,the dry mass of the upper part of the group increased slightly,but the quality of the underground part was not very obvious,so NO The impact on the accumulation of underground growth needs further research.Exogenous NO participates in the regulation of plant photosynthesis,alleviates the damage of photosynthetic system caused by drought stress,and enhances the drought resistance of walnut seedlings.3.The increase of exogenous NO concentration significantly increased the chlorophyll content decreased by drought stress.At the same time,exogenous NO can improve the efficiency of electron transfer in the PSII system,and relatively reduce the reduction state of PSII,which plays an important role in protecting the leaf photosynthetic system from excessive light energy.4.Drought stress leads to the accumulation of osmotic adjustment substances.Exogenous NO can promote the accumulation of these osmotic adjustment substances,increase the cell osmotic potential,maintain swell pressure,and alleviate the impact of drought on the 'Jinlong No.1' seedlings.5.Drought stress caused the production of malondialdehyde,a lipid membrane peroxidation product,the activity of antioxidant enzymes CAT and POD decreased,and the activity of SOD enzyme increased.With the increase of exogenous NO concentration,the content of malondialdehyde decreased gradually.The activity of the enzymes increased and remained at a high level,which alleviated the membrane lipid peroxidation.Among them,the content of malondialdehyde was the lowest under the treatment of 1.0mmol/L SNP,and the effect was the most significant.6.After comprehensive analysis of some indicators,it can be seen that the drought resistance of 'Jinlong No.1' treated with different concentrations of SNP is ranked as T5>T6>T4>T3>T2>T1,ie drought resistance when SNP is 1.5mmol/L.The strongest.Based on the above results,it is considered that the suitable concentration of exogenous NO can improve the drought resistance of walnut seedlings under drought stress,and the treatment effect of 1.0mmol/L-1.5mmol/L is the most significant.