| Soil salinization has become one of the major problems restricting the development of modern agriculture in China.,so it is urgent to alleviate the damage caused by salt stress to plant growth and improve the yield and quality of crops.For the possibility of secondary salinization of soil for cultivating tobacco.In this article,flue-cured tobacco K326 was used as the material to study the effect of exogenous biochar and potassium fulvic acid with different dosage on the stress of NaCl stress.The optimal dosage of biochar and potassium fulvic acid for tobacco growth and development under NaCl stress was explored by detecting the biomass of tobacco,physiological indicators of stress resistance,water content and mineral element content,analyzing the mechanism of action of these two substances in alleviating salt stress.The main research results are as follows:(1)NaCl stress inhibited the growth of the ground of tobacco plant and root of tobacco,resulting in the decrease of biomass.The addition of biochar and potassium fulvic acid promoted the root development of tobacco plants and increased the fresh and dry weight.The effect was different because of the amount of the two substances and the extension of time.The promoting effect of biochar on the growth and development of tobacco was gradually enhanced with the increase of dosage.After adding 30g/kg biochar under salt stress for 75 days,the maximum leaf width,root length and root volume of tobacco plants were all the largest in the five treatments,and there was no significant difference in biomass accumulation,root surface area and root average diameter compared with CK.Under salt stress,adding 0.4g/plant potassium fulvic acid and treating 60 days,the maximum leaf length,maximum leaf width and root volume of the tobacco plant were the largest among the five treatments.After 75 days of treatment,root indexes of tobacco plants treated with exogenous addition of 0.4g/plant potassium fulvic acid were not significantly different from CK.(2)Under NaCl stress,the content of chlorophyll,MDA and H2O2 increased significantly compared with CK.The change of chlorophyll content was inconsistent in different time periods after the application of biochar,among which 20g/kg biochar could significantly increase the total chlorophyll a,chlorophyll b and chlorophyll in tobacco leaves,and the color of leaves was darker than that of salt treatment The addition of 30g/kg biochar could significantly reduce the content of MDA and H2O2.The application of potassium fulvic acid reduced the contents of chlorophyll a and b,reduced the contents of MDA and H2O2 at the initial stage of application,and the contents of the two substances remained stable during the subsequent time.(3)Under salt stress,the water content of tobacco leaves decreased,the ratio of free water to bound water decreased,the content of Ca2+,K+and Mg2+in the abovemeal part of tobacco plant showed a decreasing trend compared with CK,and the content of Na+gradually increased.Adding 20g/kg biochar could significantly improve the relative water content of the leaves and the ratio of free water to bound water.The addition of 30g/kg biochar increased the Ca2+content and decreased the Na+content in the overground part of the tobacco plant.The addition of 10g/kg biochar significantly increased the K+content,while the change of Mg2+content showed no obvious pattern.Application of potassium fulvic acid under salt stress increased the ratio of free water to bound water in tobacco leaves among which 0.6g fulvic acid per plant had the greatest effect on leaf water status.The addition of potassium fulvic acid under salt stress could increase the content of K+and Ca2+in the overground part of the tobacco plant,reduced the accumulation of Na+,and slowed down the reduction rate of Mg2+,among which the application of potassium fulminate 0.4g/plant is the best.(4)Under salt stress,tobacco regulated the growth balance through the antioxidant enzyme system and non-enzyme system,and SOD and POD enzyme activities increased significantly,after the addition of biochar,SOD and POD enzyme activity showed a decreasing trend,and the content of GSH also decreased.The amount of biochar added had different effects on the three substances,among which the addition of biochar of 10g/kg had the greatest impact on the change of enzyme activity.Potassium fulvic acid could reduce SOD and POD enzyme activity under salt stress,increase GSH content,and slow down the damage of salt stress on tobacco from non-enzymatic pathway.Among them,the treatment with potassium fulminate added 0.4g/plant was the best.The results indicated that exogenous addition of biochar and potassium fulvic acid could improve the water condition of tobacco leaves under salt stress to different degrees,and promote the development of roots and the accumulation of biomass of tobacco plants,at the same time alleviate the membrane lipid peroxidation reaction caused by the increase of reactive oxygen species caused by salt stress,and regulate the ion balance in the overground part of tobacco.In particular,the addition of 30g/kg biochar and 0.4g/plant potassium fulvic acid had the best effect on the growth of tobacco under 150mmol/L NaCl stress. |
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