Effects Of Different Light Quality On Growth And Development, Photosynthesis And Polyphenolic Metabolism In Tobacco Plants

Using tobacco (Nicotiana tobacum L.) plants as experimental materials, thisstudy investigated the effects of light quality on the growth and development,photosynthesitic characteristics, contents of primary polyphenolic compounds andactivity of key enzymes in polyphenolic metabolism in tobacco leaves.①Effects of light quality on the growth and development, photosynthesiticcharacteristics of tobacco plants.Use LEDs to produce different monochromatic light to irradiate the tobaccoplants that grown in artificial climate chambers, effects of different light quality ongrowth, development and photosynthetic characteristics were investigated. The resultsshowed that, compared with the plants irradiated white light, Each monochromaticlight treatment reduced the plant height, and length and width of tobacco leavesexcept irradiated with red light which increased the length of leaves; The length andwidth of leaves were minimal under yellow, green and blue light, But the ratio oflength/width under yellow、purple、red and green light were bigger than irradiate withwhite light; The shape of leaves under different light quality were long and narrowexcept irradiate with blue light. In general, different monochromatic inhibited thegrowth and development of tobacco.Compared with irradiate white light,the contents of chlorophyll a,chlorophyllb,total chlorophyll and carotenoid were increased under red light, While chlorophylla,chlorophyll b,total chlorophyll and carotenoid were decreased under yellow,purpleand blue light, but raised the ratio of chlorophyll a/b.Compared with irradiate white light, Each treatments decreased the netphotosynthetic rate(Pn) of leaves, While stomatal conductance(Cond),IntercellularCO2concentration(Ci),transpiration rate(Trm) decreased at the same time. Whichmeans the decreased of net photosynthetic rate (Pn) may be caused by the factors ofthe limitation of the stomatal, different monochromatic light inhibited the growth ofphotosynthesis.Compared with irradiated white light，Each treatments decreased the initialfluorescenceintensity (F0), maximum fluorescence intensity (Fm),maximum photo -chemical quantum efficiency (Fv/Fm),photochemistry quenching coefficient (qp),Photosynthetic quantum yield photosystemⅡ(ΦPsⅡ),Nonphotochemistry quenching (NPQ) were decreased, while it is increased under yellow and green light.In general, chlorophyll fluorescence parameters of each treatments indirected show that, compared with irradiated white light，Each treatments decreased the abilit-y of photosynthesis of tobacco leaves.②Effects of light quality on the primary polyphenolic compounds and the activitiesof key enzymes in polyphenolic metabolism in tobacco leaves.Use LEDs to produce different monochromatic light to irradiate the tobaccosthat grows in artificial climate chambers, effects of different light quality on theprimary polyphenolic compounds and the activities of key enzymes in polyphenolicmetabolism in tobacco leaves were studied. The results showed that, compare withirradiate white light, Each treatments promoted the acclimation of chlorogenic acid,raised the contents of chlorogenic acid. At60d, the total contents of rutin andscopoletin of each treatment were higher than that of white light. Each treatmentincreased the total contents of rutin,scopoletin and chlorogenic acid，except underyellow light.General meaning, the activity of phenylalnine ammoniayase (PAL) raised underpurple and blue light. The rest of treatments reduced the peroxidase (POD) exceptunder red light.40d， each treatment raised the activity of polyphenoloxidase(PPO)except yellow light; At60d, the activity of PPO increased underyellow、purple and blue light.The results showed, that purple,blue light remote the synthesis and acclimationsof the chlorogenic acid,total contents of rutin and scopoletin, perhaps because of theactivity of PAL raised while the activity of POD decreased under purple and bluelight to some extent.