The Effect Of Light Quality And Light Intensity On Related Enzyme Activities And Polyphenol Products Of Phenylpropanoid Metabolic Pathway In Flue-cured Tobacco

The content of polyphenol effect the quality of tobacco leaves. Polyphenol products comes mainlyfrom phenylpropanoid metabolic pathway. Light quality and light intensity play a regulatory role on thekey enzyme of phenylpropanoid metabolic pathway and polyphenols in Flue-cured tobacco. It wasfound out that the content of polyphenol of different varieties were significantly different by fieldexperiment. The experiment was carried out through pot experiment, set up four light intensitytreatments(100%,78%,67%,44%of full sunlight) and four light intensity treatments (white light, redlight, blue light, purple light). studied the effect of different light quality and light intensity on relatedenzyme activity and polyphenol of phenylpropanoid metabolic pathway and mutual relationships in fastgrowing period, topping stage and technical maturity stage.in order to provide a theoretical reference forthe regulatory of phenylpropanoid metabolic pathway and formative mechanism of the quality oftobacco leaves. The main results are as follows:(1) The activities of cinnamic acid-4-hydroxylase (C4H), ρ-coumaric acid-4-ligase (4CL) and thecontent of polyphenol were max in Hongda which significant difference with K326and Yunyan87. Theactivities of phenylalanine aminolyase (PAL) was no significant difference in all the tobacco cultivars.The contents of polyphenols from different tobacco cultivars varied differently, which demonstratedhongda was the highest and K326was the lowest at maturity stage.(2) The activities of phenylalanine aminolyase (PAL), cinnamic acid-4-hydroxylase (C4H),ρ-coumaric acid-4-ligase (4CL) and the content of polyphenol were max in technical maturity stagewhich significant difference with fast growing period, topping stage. The changes of related enzymeactivity and polyphenol of phenylpropanoid metabolic pathway were well illustrated from strengtrlygrowing stage to maturity stage, and it was possibly the crucial period. Studies on related enzymeactivities and polyphenol products of phenylpropanoid metabolic pathway in six flue-cured tobaccos.The results showed that Polyphenol metabolic has space-time and genotypic variation characteristicsand C4H is the most important enzyme during polyphenol biosynthesis.(3) The polyphenol content of different cultivars increased sustainedly from strengtrly growingstage to maturity stage, the content of polyphenol were max in technical maturity stage. The activities ofphenylalanine aminolyase (PAL) was decreased under shading condition. The activities of cinnamicacid-4-hydroxylase (C4H) of Hongda and K326were increased under appropriate shading condition,theactivities of ρ-coumaric acid-4-ligase (4CL) of K326also has same tendency. The activities of theseenzymes were all smothered under44%of full sunlight. Light quality had obvious effect on thesynthesis and accumulation of the polyphenol. The polyphenol content of the upper leaves of Hongdaand Zhongyan100and the middle leaf of Hongda under appropriate shading condition were more thanfull sunlight, while the upper leaves of K326and the middle leaf of Zhongyan100and K326has anopposite tendency. The polyphenol content of the upper leaves of all the cultivars under shadingcondition were less than full sunlight. The synthesis and accumulation of the polyphenol was smotheredunder44%of full sunlight. (4) The activities of phenylalanine aminolyase (PAL), cinnamic acid-4-hydroxylase (C4H),ρ-coumaric acid-4-ligase (4CL) were higher than the other light quality. The activities of phenylalanineaminolyase (PAL) under white light, red light, purple light were max in technical maturity stage, whileit was max in topping stage under blue light. The activities of cinnamic acid-4-hydroxylase (C4H) wasdecreased under red light, blue light, purple light from topping stage to maturity stage. But it it was maxin maturity stage under white light. The activities of ρ-coumaric acid-4-ligase (4CL) was obviouslyincreased from strengtrly growing stage to maturity stage and was max in technical maturity stage.Compared with the white light, the activities of cinnamic acid-4-hydroxylase (C4H), ρ-coumaric acid-4-ligase (4CL) were all smothered under red light, blue light, purple light treatments. The polyphenolcontent of the upper and middle leaves were decreased under red light, blue light, purple light. Thepolyphenol content of the lower leaves of Hongda and Zhongyan100were decreased under purple light,while red light can smother its synthesis and accumulation in lower leaf. Compared with the white light.The synthesis and accumulation of polyphenol were all smothered under red light, blue light, purplelight treatments, and blue light treatment was most evident.