Effects of different shading treatments on growth and photosynthetic physiology of cigar wrapper leaves
[Objective]The present study aimed to investigate the effects of different shading methods on the growth and photosynthetic physio-logical characteristics of fresh cigar wrapper leaves.[Method]The experiment conducted an orthogonal L9(34)design on the color(green,black,white),shading rate(40％,60％,80％),and shading time(20,25,30 days after transplantation)of the shading net,measured the ag-ronomic traits,chlorophyll content,fluorescence parameters,and photosynthetic physiological indicators of shaded tobacco plants,analyzed the expression of genes related to photosynthesis,and performed significance and range analysis on the measured indicators.[Result](i)Shading net color was the main factor affecting agronomic traits,and the ranking of factors affecting photosynthetic indicators was shading rate＞shad-ing net color＞shading time.(ii)After shading,the white shading net promoted the growth of cigar wrapper tobacco leaves;The total chloro-phyll content of fresh tobacco leaves increased with the increase of shading rate;The actual photosynthetic efficiency(ΦPS Ⅱ),chlorophyll potential activity(Fv/Fo),photochemical quenching coefficient(qP),and maximum photochemical efficiency(Fv/Fm)significantly in-creased under high shading,but the non-photochemical quenching coefficient(qN)significantly decreased;The net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)all decreased,reaching their minimum at 80％shading,while the intercellular CO2 concentration(Ci)significantly increased at 80％shading;The expression levels of the gene encoding the light harvesting complex chlorophyll a/b binding protein 4.2(Lhcb4.2)and the gene encoding the reaction center protein CP47(psbB)in Light System Ⅱ significantly increased under 80％shading.The gene encoding the light harvesting complex chlorophyll a/b binding protein 6(Lhcb6)in Light System Ⅱ signifi-cantly increased under 60％shading.The gene encoding the D2 protein in Light System Ⅱ(psbD)was expressed lower under 80％shading than under non-shading,However,there were no significant changes in ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit gene(rbcS)and the gene encoding D1 protein in photosystem Ⅱ(psbA).[Conclusion]The shading treatment alters light quality and intensity,af-fecting the expression of genes encoding proteins related to photosynthesis,thereby affecting the photosynthesis of tobacco leaves.After shad-ing,the accumulation of chlorophyll and the efficiency of photosynthesis are accelerated to varying degrees,and the effect is the greatest under 80％shading rate treatment.
Cigar wrapper tobacco leavesColor of the shading netShading rateShading timePhotosynthetic index
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万方数据
