The Effect And Regulation Mechanism Of Different Excess Light Energy On The Anthocyanin Synthesis In Leaves Of B.Semperflorens

With the continuously improve of requirements for urban garden greening and living environment greening,more and more people prefer that color-leafed plants should be widely used.The main reason that most of the color-leafed plants present color is the anthocyanin.In order to enrich the varieties of the color-leafed plants in garden greening,more and more scholars are interested in the effect and regulation mechanism under the adversity on anthocyanin synthesis.Therefore,the Begonia semperflorens of ‘Super Olympia’（green leaf）are used as the material in this study.Taking the anthocyanin biosynthesis pathway as the main line and the As A-GSH circulation pathways as the auxiliary line,we investigated the chlorophyll a fluorescence induction kinetics parameters,the anthocyanin synthesis and the As A-GSH circulation pathways under low temperature,intensity strength and excess light energy.The main results are as follows:（1）Ordinary light and high light under low temperature conditions improve greatly the content of O₂^-.in Begonia semperflorens leaves.They are 43.63% and 98.60% higher than the control respectively.As we all known,a lot of excess light energy is accumulated through large amounts of excess excitation energy produced by the transport of pseudocyclic photosynthetic electron.However,the condition of low light under low temperature and ordinary light under room temperature do not result in the same phenomena.Studies on chlorophyll a fluorescence induction kinetics parameters show that ordinary light and high light under low temperature make Fv/Fm and Fv/Fo decrease and Fo rise significantly.This shows that primary light energy coversion of photosystemⅡ（PSⅡ）declines and the use of light in photosynthetic apparatus declines too.The potential activities of PSⅡ were destroyed.It means that the plants produce excess light energy under the two processes.Therefore,the decline of contents of the Fv’/Fm’,ФPSⅡ,qp,J_PSⅡ,PCR,and the increase of 1-qp,NPQ,ФNPQ,HDR,JNPQ in Begonia semperflorens leaves with ordinary light and high light under low temperature also indicate the generation of the excess light energy.However,there are not significant changes on the fluorescence parameters under the treatments for low light under low temperature and ordinary light under room temperature.（2）With ordinary light and high light under low temperature leaves,the expression level of anthocyanin synthesis genes PAL,CHS,F3 H,ANS in Begonia semperflorens increase significantly as the degree of the accumulation of excess light energy increases.And the gene expression quantity relations are ANS>F₃H>CHS>PAL.It produces a large number of anthocyanin.The contents of anthocyanin with ordinary light and high light under low temperature are 166.10% and 330.07%higher than the control.So it can resist external conditions better.However,the plants produce few anthocyanin under the condition of low light with low temperature and ordinary light with room temperature.It may be caused by related synthetase activities affected by the inadequate of the carbohydrate.（3）The As A-GSH circulation pathway in the plant is another main path to scavenge active oxygen and to withstand adversity except for the anthocyanin.Under the condition of ordinary light and high light with low temperature,with the continuous increase of the content of O₂^-.and H₂O₂,the assorbic acid（As A）content increase by 47.33% and 80.09% and the reduced glutathione（GSH）content increase by31.04% and 69.32% compared with the controls.And the activity of the enzyme like Ascorbate peroxidase（APX）,Monodehydroascorbate reductase（MDHAR）,Dehydroascorbate reductase（DHAR）,Gluthatione reductase（GR）has increased in different degrees.Compared with the controls,The ratios of reduction of As A/DHA、GSH/GSSG、NADPH/ NADP+ also increased significantly showing that the plants have enough resilience to cope with adversity stress under the condition of ordinary light and high light under low temperature.With low light under low temperature and ordinary light under room temperature,As A-GSH circulation pathway does not significantly change showing that there are not excess light energy generated and the plant is under a no-stress environment in this conditions.In conclusion,the excess light energy is generated in Begonia semperflorens under the ordinary light and high light with low temperature conditions.Due to the content of the active oxygen increases significantly,it has a negative effect on chlorophyll a fluorescence induction kinetics parameters and thus it has a certain degree of light inhibition on the plant.When the plant produces excess light energy,we know that,though the gene expression,the Begonia semperflorens firstly increases the activity of the enzyme PAL,CHS,F3 H,ANS.Then it synthesizes a large number of anthocyanin,and in the form of "Light Barrier" to reduce the degree of the damage in adversity.With ordinary light and high light under low temperature conditions,the increase of the content of O₂^-.and the H₂O₂ in Begonia semperflorens leaves also changes the circulation pathways of As A-GSH.By improving the As A,GSH,MDHAR,DHAR,APX,GR and reducing of As A/DHA,GSH/GSSG,NADPH/NADP+ to clear the dangers of active oxygen.To maintain the normal physiological function,the degree of the increase is different.