| In order to investigate the effects of the amount of tobacco specific compound fertilizer and the ratio of base to chase on the carbon and nitrogen metabolites,key enzyme activities and the expression of key enzyme genes in flue-cured tobacco,Yunyan 87 was used as material to carry out two factor randomized block test with different compound fertilizer dosage(781.20 kg/hm~2,1031.25 kg/hm~2,1281.30kg/hm~2)and base topdressing ratio(5:5,6:4,7:3).The effects of different compound fertilizer dosage and base topdressing ratio on the content of main products of carbon and nitrogen metabolism,the activity of key enzymes and the gene expression of key enzymes in flue-cured tobacco leaves at field stage were studied,so as to provide reference for determining the suitable amount of tobacco specific compound fertilizer in Yunyan 87 and improving the yield and quality of tobacco leaves.The main conclusions are as follows:1.The carbon metabolism ability of flue-cured tobacco was enhanced by increasing the amount of compound fertilizer.The total sugar content and reducing sugar content of tobacco increased with the increase of the amount of compound fertilizer.When the ratio of base to topdressing was 6:4,with the increase of the amount of compound fertilizer,the activities of INV,AGPase,α-amylase increased at first and then decreased,the declining period of FBPase activity moved forward,SS and SPS activity also increased after budding stage.Under the condition of compound fertilizer dosage of 1281.30 kg/hm~2,the content of main products of carbon metabolism and the activity of key enzymes were the highest when the base topdressing ratio was 6:4.With the increase of the amount of compound fertilizer,the expression of Nt SS and Nt INV decreased at first and then increased,the expression ofα-amylase increased gradually.Correlation analysis showed that the contents of total sugar and reducing sugar were positively correlated with the activities of INV,SSS and FBPase from budding stage to maturity stage of lower leaves,and negatively correlated with the activity ofα-amylase.There were SS activity and Nt SS expression,α-amylase activity and Ntα-amylase expression was negatively correlated from vigorous stage to budding stage.There was a positive correlation between the activity of INV and the expression of Nt INV at vigorous stage,but a negative correlation at budding stage.2.The increase of compound fertilizer could enhance the content of main products of nitrogen metabolism and the ability of nitrogen metabolism of flue-cured tobacco in early growth stage.The contents of total nitrogen,nicotine and protein increased gradually with the increase of the amount of compound fertilizer.When the ratio of base to topdressing was 6:4,the activities of NR,NIR and GS were the highest in the period from cluster stage to vigorous stage.The main product content and key enzyme activity of nitrogen metabolism were the best at 6:4 of base to chase ratio at 1281.30 kg/hm~2.The expression of Nt NR and Nt GS in tobacco leaves increased gradually from the vigorous stage to the budding stage of the flue-cured tobacco,and decreased first and then increased with the increase of the amount of compound fertilizer,and the expression of the treatment with high compound fertilizer was higher.Correlation analysis showed that total nitrogen,nicotine and protein contents were negatively correlated with NR and NIR activities,and positively correlated with GS and GDH activities.The NR activity was negatively correlated with Nt NR expression in vigorous stage,but positively correlated with Nt NR expression in budding stage.From vigorous stage to budding stage,GS activity was positively correlated with Nt GS expression.3.The amount of compound fertilizer and the ratio of base to topdressing had significant effects on the field growth of flue-cured tobacco.With the increase of the amount of compound fertilizer,the agronomic characters of tobacco plant were gradually optimized from cluster stage to budding stage,and treatment 8 was the best.The dry matter accumulation of tobacco stem and leaf increased gradually in different growth stages.4.The amount of compound fertilizer and the ratio of base to topdressing had significant effects on the economic characters and chemical composition of flue-cured tobacco.The yield,output value,average price and superior tobacco rate of tobacco increased gradually with the increase of the amount of compound fertilizer.The yield,output value and superior tobacco rate of T8 treatment were the highest.Among the chemical components of flue-cured tobacco leaves,T8 treatment was more harmonious,in which the contents of total sugar,total nitrogen and nicotine in the middle leaves were in the appropriate range,while the contents of reducing sugar,nicotine and protein in the upper leaves were in the appropriate range.Correlation analysis showed that the activities of SS,AGPase,INV and SSS were positively correlated with the contents of total sugar and reducing sugar in middle leaves from budding stage to maturity stage of lower leaves;there was a negative correlation between the content of total sugar and reducing sugar in upper leaves.The activities of NR,NIR and GDH were negatively correlated with the contents of total nitrogen,nicotine and protein in the middle leaves,while the activity of GS were positively correlated with the contents of total nitrogen,nicotine and protein in the middle leaves.In conclusion,treatment 8(compound fertilizer dosage 1281.30 kg/hm~2,base topdressing ratio 6:4)was the most favorable for the balance of carbon and nitrogen metabolism of flue-cured tobacco,which was helpful to improve the economic characteristics of tobacco leaves and coordinate the chemical composition of flue-cured tobacco leaves. |
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