Research On The Mechanism And Regulation Of Photosynthesis And Carbon And Nitrogen Metabolism In Upper Tobacco Leave

In order to explore the mechanism of sugar synthesis and nitrogen accumulation in upper tobacco leaves and key regulatory technologies,this paper studies the photosynthesis and carbon and nitrogen metabolism processes and influencing factors of upper tobacco leaves,in order to improve the availability of upper tobacco leaves.In this paper,Yunyan 87 was used as the experimental material to explore the effects of spraying trehalose and glutamic acid on the photosynthesis and carbon and nitrogen metabolism of upper tobacco leaves under different light conditions through pot experiments.Based on high-throughput transcriptome sequencing,the photosynthesis of upper tobacco leaves was studied and the molecular physiological response mechanism of carbon and nitrogen metabolism to light,trehalose and glutamate spraying;based on field experiments,the effects of different film removal periods and top dressing periods on the dynamic accumulation process of carbon and nitrogen in upper tobacco leaves were studied.The main findings of this paper are as follows:(1)The chlorophyll content of tobacco plants in shading treatment and supplementary light treatment was significantly increased,the net photosynthetic rate,stomatal conductance and transpiration rate increased with the increase of light intensity,while the intercellular carbon dioxide concentration was the opposite.Spraying trehalose and glutamic acid can effectively improve the photosynthetic efficiency of upper tobacco leaves;Supplemental light can activate the key enzymes in the passivated state of the Calvin cycle,increase the metabolic intensity of the Calvin cycle,and improve the carbon fixation ability of tobacco plants.L3-S2(supplementary light-trehalose)treatment significantly promoted the accumulation of sugar while reducing the nicotine content of the upper tobacco leaves,and the effect was the best.(2)Compared with natural light(L1),the expression of porphyrin and chlorophyll metabolism,complex light-harvesting pigment proteins,and DEGs related to photosynthetic electron transport pathways were up-regulated in shading treatment(L2),while the expression of photosystem I,photosynthetic carbon fixation,starch and sucrose metabolism was up-regulated.,The expression of DEGs related to nitrogen metabolism pathway was inhibited;The expression of DEGs related to porphyrin and chlorophyll metabolism,photosystem I,photosystem II,photosynthetic carbon fixation,starch and sucrose metabolism pathways was up-regulated,and the expression of nitrogen metabolism pathway-related DEGs was inhibited in supplemental light treatment(L3).(3)Compared with spraying clear water(S1),the expression of DEGs related to chlorophyll synthesis,carotenoid biosynthesis,photosynthesis,photosynthetic carbon fixation,starch and sucrose metabolic pathways were up-regulated in the treatment of trehalose(S2),chlorophyll degradation,The expression of DEGs related to nitrogen metabolism pathway was inhibited;The expression of DEGs related to photosynthetic carbon fixation,starch and sucrose metabolism pathways was up-regulated by spraying glutamate(S3),while the expression of DEGs related to chlorophyll degradation and nitrogen metabolism pathways was inhibited.(4)Chlorophyll content,nitrogen content and nitrate reductase activity in the upper leaves gradually decreased with the growth stage,total carbon,reducing sugar,total sugar and nicotine content gradually decreased with the growth stage,and the activities of sucrose synthase and sucrose phosphatase increased first and then decreased,reaching a peak at 105 days,and glutamine synthase showed a trend of first increased,then decreased and then increased.Under the conditions of this study,removing the film for 40-50 days after transplanting can effectively improved the carbon and nitrogen metabolism of tobacco plants,while increased the accumulation of sugar in the upper leaves,while maintaining the nicotine content of tobacco leaves in an appropriate range.(5)When the top-dressing period was shifted later,the carbon and nitrogen metabolism enzymes,reducing sugar,total sugar,nitrogen and nicotine were significantly down-regulated in the pre-growth stage of tobacco plants compared with the CK treatment.If the top-dressing time was too late,the absorption of nitrogen by tobacco plants will increase,the synthesis and accumulation of nicotine will increase,and the time of tobacco leaves to mature and turn yellow will be later.This experimental study showed that top dressing(T2)29 days after transplanting was more beneficial to the accumulation of sugar in tobacco leaves.