Study On The Cyclic Electron Flow Regulation And Heat Dissipation Mechanism Of Cotton With Different Light Absorption Characteristics

Plants absorb more light energy than they need for carbon assimilation,resulting in a large surplus of excitation energy that destroys the PSII response center.In order to prevent the occurrence of light damage,plants will activate a series of light protection mechanisms to maintain the balance between the absorption and utilization of light energy in the photosynthetic mechanism.The annular electron flow around PSI is a photoprotection mechanism that has attracted much attention in recent years.The cyclic electron flow can promote the establishment of cross-thylakoid membrane proton gradient(?pH),drive ATP synthase to synthesize ATP,accelerate the repair of light damage,acidify thylakoid lumens,stimulate heat dissipation on the side of PSII,and stabilize the oxygen-releasing complex,so as to protect PSII from damage caused by excessive reduction.Cotton is the most important cash crop in xinjiang,which will experience high light,drought and other environmental conditions during the growing season.From this study on the differences of the absorb light energy,selecting the chlorophyll content and anthocyanin content test of absorbing sunlight and differences of cotton with different materials,different cotton photosynthetic characteristics in and around the PSI ring was very big difference,clear cotton leaf absorption characteristics of different effects on photosynthetic characteristics and to maintain the photosynthetic mechanism run started by the thermal dissipation mechanism,reveal the difference of absorption capacity and light protection mechanism,the relationship between the results of the study can provide scientific basis for high photosynthetic efficiency breeding of cotton.The main research results are as follows:(1)The photosynthetic performance of cotton with different chlorophyll content was studied.The content of chlorophyll,carotenoids,carotenoids/total chlorophyll,gas exchange parameters,photorespiration and so on were measured.With the increase of chlorophyll content,the net photosynthetic rate did not increase significantly,while the stomatal conductance and the intercellular carbon dioxide concentration remained stable,while the photorespiration regulation ability of the dark reaction downstream of the photosynthetic mechanism was gradually weakened,and the protection ability of carotenoids on the photosynthetic mechanism was gradually weakened.Studies have shown that cotton with low chlorophyll content has relatively stable photosynthetic capacity and strong photorespiration and carotenoid protection ability.Therefore,low-chlorophyll cotton mainly relies on photorespiration and carotenoids to maintain the stable operation of photosynthetic mechanism.(2)The cotton with high chlorophyll content has strong cyclic electron flow and its regulating ability.On the basis of study I,the total cyclic electron flow activity,NDH mediated cyclic electron flow activity,chlorophyll fluorescence parameters,ATP synthase activity,non-photochemical quenching curve,zeaxanthin synthesis rate and so on were further measured.Studies have shown that with the increase of chlorophyll content,the total cyclic electron flow activity and NDH mediated cyclic electron flow activity are gradually enhanced,and the processes of ATP synthesis and heat dissipation regulated by cyclic electron transfer are also gradually enhanced.Therefore,high chlorophyll content is accompanied by strong ring electron flow activity and its regulatory ability.(3)The activity of PSI and PSII in cotton with high content of anthocyanin was studied.Anthocyanin content,gas exchange parameters and chlorophyll fluorescence parameters of cotton were measured.The results showed that with the increase of anthocyanin content,there was no significant difference in net photosynthetic rate,but the stomatal conductance and intercellular carbon dioxide concentration gradually decreased.Meanwhile,the thermal dissipation of the photoprotection mechanism gradually increased and the light damage gradually weakened,leading to the gradual increase of the photochemical efficiency of PSI.The P700 in the oxidation state was gradually enhanced,while the P700 in the reduced state was gradually weakened,resulting in a gradual increase in the photochemical efficiency of PSI.Therefore,higher anthocyanins can effectively protect the activity of PSI and PSII.(4)The dissipation process of anthocyanin in cotton was studied to maintain the stability of photosynthetic mechanism.On the basis of study 3,the total cyclic electron flow activity,NDH mediated cyclic electron flow activity,ATP synthase activity and zeaxanthin synthesis rate were measured.The results showed that with the increase of anthocyanin content,the total cyclic electron flow activity and the NDH mediated cyclic electron flow activity were gradually enhanced,the ATP synthesis regulated by cyclic electron flow was also gradually enhanced,and the synthesis rate of zeaxanthin was gradually weakened.The synthesis rate of zeaxanthin in cotton without anthocyanin was obviously higher than that in cotton with anthocyanin.Therefore,anthocyanins can be used as a light protection mechanism to dissipate excess light energy.