Mitigating Effect Of Spraying Potassium Fulvic Acid And Polyglutamic Acid On Drought Stress Of Sweet Potato

Drought is one of the main adverse conditions that plants often face.The damage of drought in agricultural production is particularly serious,which seriously affects the growth and yield of crops.In this experiment,three sweet potato varieties（Yanshu 25,Yuzi 7 and Shangshu 19）were used as experimental materials,and method of using soil culture simulation test and liquid culture simulation test,the effects of foliar application of potassium fulvic acid and polyglutamic acid on the growth and development of different varieties of sweet potato were studied.The results showed that:1.Under drought stress,the yield of sweet potato of the three varieties tested in soil culture decreased significantly by 32.79-34.20%compared with T1 treatment.Spraying potassium fulvic acid and polyglutamic acid can significantly alleviate the effect of drought stress on sweet potato yield,but cannot eliminate the harm caused by stress.The optimum concentration of potassium fulvic acid on sweet potato is 1g/L,and sweet potato yield is 17.9-22.7%higher than drought stress.The optimum concentration of polyglutamic acid on sweet potato was 1g/L,and sweet potato yield increased by 15.2-21.1%compared with drought stress.Compared with T1,drought stress will reduce the proportion of sweet potato commercial potatoes by 18.60-25.12%.Spraying potassium fulvic acid and polyglutamic acid is beneficial to increase the proportion of commercial potato,26.25-40.86%higher than drought stress,and improve economic benefits.2.Under soil culture conditions,drought stress reduced the starch content of sweet potato root tuber by 11.37-14.68%and increased the soluble sugar content by 8.02-10.01%compared with T1 treatment.Spraying potassium fulvic acid and polyglutamic acid promoted the conversion of soluble sugar from sweet potato root tuber to starch,increasing starch content by 3.69-8.21%compared with T2 treatment,reducing soluble sugar content by 4.44-7.43%compared with T2 treatment.Drought stress also reduced the soluble protein content of sweet potato root tuber by 8.27-8.56%compared with T2 treatment.Spraying potassium fulvic acid and polyglutamic acid increased the content of soluble protein by 3.29-6.04%compared with T2 treatment.The optimum concentration of potassium fulvic acid on sweet potato quality is1g/L,and the optimum concentration of polyglutamic acid is 1g/L.3.Drought stress reduced the accumulation of nitrogen,phosphorus and potassium in sweet potato.Under drought stress in soil culture,compared with T2 treatment,the accumulation of nitrogen,phosphorus and potassium in stems and leaves decreased by 33.51-51.49%,41.67-56.25%and 42.31-53.51%respectively.The accumulation of nitrogen,phosphorus and potassium in root tuber decreased by 51.98-57.33%,52.43-60.50%and 60.96-70.51%,respectively.Spraying potassium fulvic acid and polyglutamic acid can significantly increase the accumulation of nitrogen,phosphorus and potassium in sweet potato.Compared with T2treatment,the accumulation of nitrogen in stems and leaves increased by 26.08-57.65%,the accumulation of phosphorus increased by 22.14-57.14%,and the accumulation of potassium increased by 25.83-57.08%.Nitrogen accumulation in root tuber increased by 46.15-86.31%,phosphorus accumulation increased by 39.78-84.80%,and potassium accumulation increased by 52.95-120.29%.The effect of drought stress on root tuber is greater than that on stem and leaf.4.Under the condition of solution culture,drought stress caused the activities of SOD,POD,CAT and other antioxidant enzymes and MDA content in stem and leaf of sweet potato seedlings to increase sharply.Compared with T1 treatment,SOD activity increased by 1.10-1.27 times,POD activity increased by 1.72-1.77 times,CAT activity increased by 2.15-2.23times and MDA content increased by 2.52-2.82 times.The soluble protein content in stems and leaves decreased significantly by 28.03-31.39%.The root activity of sweet potato was also significantly inhibited by 63.82-66.84%.After spraying potassium fulvic acid and polyglutamic acid,SOD,POD,CAT and other antioxidant enzyme activities and MDA content showed a downward trend.Compared with T2 treatment,SOD activity decreased by8.15-10.79%,POD activity decreased by 19.31-20.11%,CAT activity decreased by 18.33-22.64%,MDA content decreased by 25.31-32.05%;The content of soluble protein in stems and leaves was significantly increased by 11.03-25.48%.Root activity increased significantly by 45.13-87.44%compared with T2 treatment.The results of solution culture test showed the same trend as that of soil culture.5.Under the condition of soil culture,drought stress will cause the photosynthetic rate,stomatal conductance,intercellular CO₂concentration and SPAD value of sweet potato leaves to drop significantly.Compared with T1 treatment,the photosynthetic rate and SPAD value will drop 47.72-51.46%and 15.70-18.18%respectively.Spraying potassium fulvic acid and polyglutamic acid can significantly improve photosynthetic efficiency and SPAD value.Compared with T2,photosynthetic efficiency increased by 5.0-13.19%,SPAD value increased by 5.11-13.12%.The results of solution culture test showed the same trend.