| Apex excision changes the balance of hormones in tobacco, and leads to decreasing of potassium concentration in tobacco leaves simultaneusly. GA3 is one of the significant hormones in flue-cured tobacco, affected by topping too. In order to study the effect of spraying foliar nutrient solution on the accumulation and distribution of K+ as well as the quality of flue-cured tobacco,the foliar nutrient solution which is GA3-based nutrient solution mixed potassium, calcium and magnesium. The effect of foliar spraying (spraying after topping immediately) different concentrations mixed nutrient solution on the dry weight, the potassium concentration,the accumulation and distribution of K+ of different tobacco organs, the content of endogenous GA3 and IAA, and IAA oxidase activity in leaves, and the chemical composition of leaves on the Oday, 10days,25days,40days after topping were studied with pot experiment and plot experiment. The mixed nutrient solution which is made up by a constant concentration of potassium, calcium, magnesium solution and different concentrations of GA3 solution.The results are as follows:(1) The GA3-based mixed nutrient solution maintained the content of endogenous GA3 and IAA after toppingThe GA3-based mixed nutrient solution inhibited the activity of IAA oxidase after topping significantly, slowed down the reduction of endogenous GA3, IAA contentin tobacco, then maintained the content of endogenous GA3 and IAA after topping.The greater the concentration of exogenous GA3, the role of inhibition the IAA oxidase activity and slowing down the reduction of endogenous GA3 and IAA content in tobacco after topping the more obvious, so The GA3-based mixed nutrient solution with GA3 concentration of 40 μmol/L treatment was the best. The activity of IAA oxidase in upper middle and lower leaves were lower than in the control of 14.64%,11.61% and 12.73% individually,10 days after topping, And at the 25 and 40 days after topping, the activity of IAA oxidase in upper leaves were lower than in the control of 8.68% and 4.26% individually. The content of GA3 in upper middle and lower leaves were higher than in the control of 31.54%,54.51% and 74.42% individually, And at the 25 and 40 days after topping, The content of endogenous GA3 in upper leaves were higher than in the control of 27.01% and 28.99% individually. The content of IAA in upper middle and lower leaves were higher than in the control of 13.68%,20.45% and 31.59% individually, and at the 25 and 40 days after topping, The content of endogenous IAA in upper leaves were higher than in the control of12.64% and 18.33% individually.(2) The GA3-based mixed nutrient solution promoted the accumulation of dry matter of tobacco plant significantlyThe GA3-based mixed nutrient solution with GA3 concentration of 40 μmol/L treatment promoted the accumulation of dry matter of tobacco plant was the most obvious, within 25 days after topping. The dry weight of middle and upper leaves were higher thanthe control treatment of 3.79% and 8.47% individually, within 10 days after topping. The effect of spraying the GA3-based mixed nutrient solution with GA3 concentration of 20 μmol/L twice treatment on the promotion of tobacco leaf dry matter accumulation is the best, within 10 days after toppingto 25 days after topping, the dry weight of upper leaves were higher thanthe control treatment of 4.56 percentage points.(3) The GA3-based mixed nutrient solution promoted the accumulation of potassium in tobacco and the distribution of potassium in tobacco reasonable significantlyThe GA3-based mixed nutrient solution promoted the accumulation of potassium in tobacco plant and the distribution of potassium in tobacco leaves, reduced the reflux of potassium from leaves and the efflux of potassium from tobacco plant significantly. The GA3-based mixed nutrient solution with GA3 concentration of 40 μmol/L treatment promoted the accumulation of potassium in tobacco plant and the distribution of potassium in tobacco leaves, as well as reduced the reflux of potassium from leaves and the efflux of potassium from tobacco plant was the most obvious. The accumulation of potassium in tobacco plant was higher than the control treatment of 9.63%, the rate of increasewas higher thanthe control treatment of 11.91 percentage points at the same time, in addition the distribution of potassium in tobacco leaves was higher than the control treatment of 7.22 percentage points. Within 10 days after toppingto 25 days after topping, the GA3-based mixed nutrient solution with GA3 concentration of 40μmol/L treatment reduced half of potassium refluxthanthe control treatmentin tobacco leaves, and reduced 28.78% of potassium efflux than the control treatmentin tobacco plant.(4) The GA3-based mixed nutrient solution improved the quality of flue-cured tobacco significantlyThe GA3-based mixed nutrient solution improved the content of potassium in upper middle and lower leaves significantly, the increase amplitude was between 19.16% to 51.03%, especially for the upper leaves, but there have no significant difference between 30 μmol/Land 40μmol/L concentration for the content of potassium in leaves. The GA3-based mixed nutrient solution reduced the content of nicotine in upper leaves significantly.The GA3-based mixed nutrient solution with GA3 concentration of 20 μmol/L treatment had been able toreduce the content of nicotine in upper leaves significantly. The GA3-based mixed nutrient solution with GA3 concentration of 30 μmol/L could help various parts of the tobacco leaves to form an appropriate amount of sugar, the margin of the total sugar to reducing sugar and the ratio of sugar to nicotine. |
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