| Aiming at the problem that it is difficult for tobacco leaves to fall yellow at maturity stage in Xiangyang,Hubei Province,taked K326 as the research object,set up different concentration of sodium tungstate,analyzed the effects on growth and development of tobacco leaf,carbon and nitrogen metabolism enzyme,antioxidant enzyme activity,degradation of plastid pigment in maturation period,and the quality of tobacco leaves.The main results are as follows:1.The leaf length,leaf width and the maximum leaf area of the upper and middle tobacco leaves were reduced by sprayed sodium tungstate.After topping,the leaves of each treatments were lengthened and widened,but sodium tungstate inhibited the growth of tobacco leaves.That is,with the increase of sprayed concentration,the inhibition of tobacco growth was enhanced.30 days after topping,compared with the control,the maximum leaf area of the upper leaves treated with T1,T2 and T3 decreased by 7.12%,11.76% and 26.59%,respectively,while the middle leaves decreased by 6.37%,14.08% and 22.32%.The root activity of the tobacco treated with sodium tungstate after topping was lower than that of the control,and decreased with increasing concentration.On the 30 day after topping,they decreased by 9.16%,30.34% and 41.57%,respectively.It was demonstrated that sodium tungstate effectively controlled the growth of excessive growth tobacco plants at later stages,and The higher the concentration,the stronger the inhibition.Among them,the tobacco plants treated with T2 showed good performance in the field and the leaves of tobacco fell yellow earlier.2.Sodium tungstate treatment effectively reduced the content of chlorophyll and carotenoids in tobacco leaves after topping,and gradually decreased with the time of topping and the increase of sodium tungstate concentration.30 days after topping,compared with the control,the chlorophyll content of T1,T2 and T3 decreased by 11.40% and 27.42% 35.98,and carotenoid decreased by 14.10% and 22.84% 43.58%.The degradation rate of chlorophyll was faster in 20~30 days after topping,the degradation rate of carotenoid was different among different treatments.However,the degradation amount of each treatment was negatively correlated with the concentration of sodium tungstate,and the degradation rate of chlorophyll was faster than that of carotenoids.It indicated that sodium tungstate promoted the degradation of plastid pigment in mature tobacco leaves and accelerated the maturation of tobacco leaves.3.After sprayed sodium tungstate,the NR activity of tobacco leaves was significantly decreased,and the NR activity decreased significantly with the increase of the concentration.The activity of GS was negatively correlated with the concentration of sodium tungstate in a certain concentration range.The inhibitory effect of high concentration of sodium tungstate on GS activity was not obvious.The activity of Inv and AM was higher than that of the control.The activity of Inv was positively correlated with the concentration of sodium tungstate.Both T1 and T2 treatments enhanced AM activity,and T2 treatment was better than T1 treatment,while the AM activity of T3 decreased compared with that of T2,but still higher than that of T1 and control.It was indicated that T2 treatment was more conducive to the reduction of nitrogen metabolism and the transformation of carbon and nitrogen metabolism in late mature stage of tobacco leaves,thus promoting the late maturity of tobacco leaves.4.All treatments of sodium tungstate increased the activities of SOD and POD after the topping,and T2 was significantly higher than that of other treatments,On the 30 day after topping,the enzyme activities of all treatments decreased.The content of MDA in each treatment was always rised after topping,but the content of MDA in the tobacco plants treated by sodium tungstate was lower than that of the control,which decreased with the increase of concentration.It indicated that sodium tungstate can regulate antioxidant enzyme activity and reduce MDA content in tobacco leaves.It was beneficial to reduce the harm of reactive oxygen to tobacco leaves after topping,while the decrease of antioxidant enzyme activities and the decrease of MDA content may be a symbol of tobacco senescence,to deal with T2 effect is better.5.The suitable concentration of sodium tungstate could decrease the nitrate content in the middle and upper leaves.The nitrate content was decreased by T1 and T2 treatment,but T3 treatment resulted in nitrate accumulation in tobacco plants.The nitrite content decreased with the increase of sodium tungstate concentration,and the difference between T2 and T3 treatment and control reached a significant level.As a whole T2 treatment can reduce nitrite content of nitrate River better.6.Sodium tungstate decreased leaf length,leaf width,single leaf weight,leaf quality weight,stem content,There was a significant negative correlation between sprayed concentration and the above indexes,which corresponded to the performance of field growth.The tensile strength of tobacco leaves was significantly decreased by T3 treatment.With the increase of sodium tungstate concentration,the content of nicotine and total nitrogen of tobacco leaf was decreased effectively,and the content of total sugar and potassium was increased appropriately.Combined with the requirements of high quality flue-cured tobacco,The content of chemical composition,the ratio of sugar to alkali,the ratio of nitrogen to alkali,and the ratio of potassium to chlorine in tobacco leaves treated by T2 were the best,which could harmonized the chemical composition of tobacco leaves and improved the smoking quality of tobacco leaf.Overall,the quality of cured tobacco leaves treated by T2 is the best.According to the result of the analysis of the physiological indexes of tobacco leaves by used the membership function,the treatment of T2 can effectively regulate the growth and physiological indexes of tobacco leaves at mature stage,which was beneficial to the maturity of tobacco leaves,and the quality of tobacco leaves after baking is better. |
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