| In order to improve the growth quality of the upper leaf of flue-cured tobacco and solve the problems of insufficient opening,uncoordinated internal chemical composition,poor economic characteristics of leaves and low industrial availability of the upper leaf in the process of growth and production,after the normal growth of the tobacco plant,six kinds of foliar potassium fertilizer were sprayed,including potassium dihydrogen phosphate,potassium dihydrogen phosphate mixed with potassium chloride,potassium dihydrogen phosphate mixed with calcium chloride,potassium citrate,potassium sulfate and potassium nitrate.This research studied six kinds of flue-cured tobacco leaf potash agronomic traits,chlorophyll SPAD value,upper leaves photosynthetic performance,carbon and nitrogen metabolism related enzymes activity and substance content,endogenous protective enzymes activity and content,chemical composition,tobacco economic properties after baking,the influence of cultivation treatment designed to optimize the upper leaves and improve the availability of upper leaves to provide theoretical basis and technical support.The main research results are as follows:(1)The application of foliar potassium fertilizer could improve the agronomic traits and photosynthetic performance of the upper leaves of flue-cured tobacco.The application of potassium citrate significantly decreased the aspect ratio of upper leaves and increased the leaf area,and the agronomic traits of upper leaves were best.Compared with CK,the aspect ratio of sixteenth leaf decreased 12.54% and the leaf area increased 19.66%,and the aspect ratio of fourteenth leaf decreased 3.55% and the leaf area increased 7.76%.Spraying potassium dihydrogen phosphate mixed with calcium chloride and potassium citrate could significantly reduce the weight of upper leaves and improve the tissue structure of upper leaves.Spraying potassium citrate and potassium sulfate could significantly increase the SPAD value of chlorophyll in upper leaves.Spraying potassium dihydrogen phosphate mixed with calcium chloride and potassium citrate could significantly increase the net photosynthetic rate of upper leaves and improve the photosynthetic performance of upper leaves.(2)Leaf potassium fertilizer spraying could improve the activities of enzymes related to carbon and nitrogen metabolism and the activities of endogenous protective enzymes in upper leaves,and accelerate the carbon and nitrogen metabolism in upper leaves.Sprays of potassium dihydrogen phosphate mixed with potassium chloride had the best effect on the activity of nitrate reductase in upper leaf,which was 34.38% higher than that of CK.The activity of neutral invertase in upper leaf was increased by 23.95% compared with CK by potassium citrate.The application of potassium dihydrogen phosphate mixed with calcium chloride had the best effect of increasing sucrose content in upper leaves,which was 3.86% higher than that of CK.Spraying potassium dihydrogen phosphate mixed with potassium chloride had the best effect on reducing protein content of upper leaf,which was 7.16% lower than that of CK.The activities of α-amylase,β-amylase and total amylase in upper leaves were increased by 10.99%,19.15% and 32.55% compared with CK,respectively.Spraying potassium dihydrogen phosphate mixed with calcium chloride increased POD activity in upper leaf by 12.71% and7.41%,respectively,compared with CK.Spraying potassium citrate had the best effect on SOD activity in upper leaves,which increased 14.54% and 11.60% compared with CK,respectively.The application of potassium nitrate foliar fertilizer and potassium citrate foliar fertilizer had a better effect on CAT activity in upper leaves.Spraying potassium citrate had the best effect on reducing the content of malondialdehyde and hydrogen peroxide in upper leaves.(3)The application of leaf potassium fertilizer improved the chemical composition of the upper leaves and the economic characteristics of the whole tobacco leaves after curing.The application of potassium citrate could significantly reduce the content of nicotine in upper leaves,and increase the content of potassium,reducing sugar and total sugar as well as the ratio of sugar to base in tobacco leaves.Compared with CK,the content of potassium increased by20.22%,the content of nicotine decreased by 14.95%,the content of reducing sugar increased by 18.76%,the content of total sugar increased by 16.36%,and the ratio of sugar to base increased by 39.45%.The internal chemical composition coordination effect of cured tobacco leaves was the best.Potassium citrate spraying could significantly increase the proportion,yield,average price and output value of top-grade tobacco leaves by 25.82%,8.01%,10.32% and19.14%,respectively,compared with CK,and it had the best effect on improving the economic characters of roasted tobacco leaves. |
