Response Of Main Nitrogen-containing Compounds In Flue-cured Tobacco To External Nitrogen Concentration

Nitrogen is one of the main factors affecting the quality of tobacco.It not only determines the yield of tobacco,but also affects the nitrogen compounds in tobacco,including alkaloids,amino acids and proteins,nitrogen heterocyclic compounds,amines and nitrosamines,nitrogen-containing pigments,nitrates and so on,thus affecting the flavor of tobacco.The different nitrogen compounds have different effects on flue gas.In addition to tyrosine,it is generally believed that amino acids have a positive significance on flue gas,too much protein in flue gas will produce burnt odor of feathers,and nitrates and amine derivatives are harmful to human body.Nicotine in flue gas is necessary but the content should be strictly controlled.Therefore,regulating the type and quantity of nitrogen compounds in tobacco leaves is one of the ways to improve the quality of tobacco leaves.In order to achieve the best regulation of nitrogen content in flue-cured tobacco,the response of different nitrogen-containing compounds to external source nitrogen concentration was discussed by constructing the correlation between nitrogen application amount,nitrogen metabolites and nitrogen metabolites,and the following conclusions were obtained:1.The nitrogen content of tobacco leaves was the highest at the root extension stage,and decreased with the growth stage.From the root extension stage to the middle stage of vigorous growth,the nitrogen content of tobacco increased first and then decreased with the increase of nitrogen application.The nitrogen content of 8.18g/plant or 10.91 g/plant was higher,and there was no significant difference between the two treatments;the nitrogen content of tobacco decreased after the application of more than 10.91 g/plant,which was similar to that of no nitrogen application.The nitrogen content of budding tobacco increased with the increase of nitrogen application.2.The effect of nitrogen application amount on NO₃^-and NRa was the same,that is to say,with the increase of nitrogen application amount,NRa increased,NO₃^-content of tobacco increased,too much nitrogen application amount,NRa decreased,NO₃^-content of tobacco decreased.However,the response concentration of NO₃^-to nitrogen application in different growth stages was not the same.At the root extension stage,it first increased,then decreased and then increased,with 8.18 g/plant as the first peak;at the cluster stage,it first increased and then decreased,with 10.91 g/plant as the highest,which was 15.16 mg/g;at the middle and budding stages,it increased with the increase of nitrogen application,without excessive nitrogen application.3.The content of NH₄⁺in tobacco leaves was controlled by NR,GS and GOGAT.At the root extension stage,the increase of nitrogen application made the nitrification process consume too much energy,resulting in lower GSa and gogata,and decreased with the increase of nitrogen application,the ability of ammonium assimilation decreased,and the content of NH₄⁺decreased.During the period of vigorous growth?including cluster stage,vigorous middle stage and budding stage?,the NH₄⁺content of tobacco increased with the increase of nitrogen application,the increase of GSa and gogata was the main driving force for the increase of NH₄⁺when?5.45 g/plant;when>5.45 g/plant,GSa decreased,gogata first increased and then decreased,ammonia conversion energy decreased,NH₄⁺concentration increased,and GS became the rate limiting enzyme.4.The content of protein and other nitrogen compounds in tobacco leaves increased first and then decreased with the increase of nitrogen application during the period of root extension to the middle of vigorous growth,and when the nitrogen application was 5.45 g/plant or 8.18 g/plant,the protein content was relatively high,and there was no significant difference between the two treatments.The protein content of budding tobacco increased with the increase of nitrogen application.The protein content of 5.45 g/plant was in line with the standard of high quality flue-cured tobacco.5.The total amount of free amino acids in the treatment of no nitrogen application was significantly higher than that in the treatment of no nitrogen application,and the content decreased slightly with the increase of nitrogen application,but the difference between the treatments was small;the total amount of free amino acids increased with the increase of nitrogen application in bud stage,and the amount of free amino acids in the treatment of no nitrogen application was higher than that in the treatment of no nitrogen application.At different growth stages,the free amino acids in tobacco leaves showed four kinds of changes with the amount of nitrogen application:?1?glutamate and alanine increased with the amount of nitrogen application;?2?arginine,lysine and cysteine increased first and then decreased with the amount of nitrogen application,and reached the maximum value under the treatment of 10.91 g/plant;?3?glycine decreased after the amount of nitrogen application,leucine,isoleucine;?4?no obvious or irregular influence:aromatic amino acids?L-lysine and phenylalanine?,threonine,methionine,valine,serine,histidine.6.The response of nicotine content in flue-cured tobacco to the amount of nitrogen application was different in different growth stages,and there was no obvious regularity in the period of root extension.In the middle and budding stages of flue-cured tobacco,the effect of nitrogen application on the activity of putrescine-n-methyltransferase and nicotine content was the same,which increased with the amount of nitrogen application.The nicotine content in flue-cured tobacco increased significantly with the increase of nitrogen application With the increase of nitrogen application amount,it first increased and then decreased,and the maximum value was 0.98%at 8.18 g/plant,which was significantly higher than other treatments.7.The effect of nitrogen application amount on the distribution of nitrogen in flue-cured tobacco leaves at different growth stages is quite different.Protein-N>amino acid-N>nicotine-N>NH₄⁺-N in nitrogen compounds in tobacco leaves at root extension stage>NO₃^--N,the amount of nitrogen application had no significant effect on the distribution proportion of nitrogen-containing compounds.In the vigorous growing stage,the increase of nitrogen application promoted the increase of NH₄⁺,NH₄⁺-N and nicotine-N,while the proportion of protein-N decreased first and then increased with the increase of nitrogen application.In the budding stage,the proportion of NO₃^--N and NH₄⁺-N increased first and then decreased with the increase of nitrogen application,and the trend was 8.18 g/plant,respectively the protein-N ratio decreased significantly,while nicotine-N ratio increased.8.The application of nitrogen had a great influence on the agronomic and economic characters of flue-cured tobacco.At the root extension stage and cluster stage,the agronomic indexes of flue-cured tobacco were the highest under the treatment of 6 kg/667 m²;at the budding stage,the agronomic indexes and yield of 10kg/667 m²were the highest,the ratio of top-grade tobacco in 6 kg/667 m²treatment was the largest,and the output value of 6-10 kg/667 m²treatment had no significant difference.