Study On Carbon Dynamic Of Coffea Arabica L. Under Drought And Rehydration

With the global climate change,drought intensifies and seasonal drought become frequent.Coffee producing areas in Yunnan have been seriously affected.Water deficit caused by drought severely restrict the photosynthetic capacity of plants,reduce the content of non-structural carbohydrates(NSC)stored in plants,and lead to the lack of NSC required for growth and metabolism in plants,thus affecting the formation of yield and quality and even causing plant death.In the study of coffee drought resistance,the mechanism of NSC response to drought stress and rehydration after drought is still unclear.In our study,water-controlled in soil culture pot experiment was used to treat half-aged Coffea arabica L.under drought stress and rehydration,to explore the dynamic changes of NSC in different organs,photosynthetic characteristics of leaves,and dry matter accumulation and distribution,the roots was selected to study the molecular response mechanism at transcriptome level.The main results are as follows:(1)After 7 days of drought,the coffee leaves wilted,the stomata gradually closed and the net photosynthetic rate continued to drop to zero.After 3 days of rehydration had a significant recovery effect on the morphology and photosynthetic parameters caused by drought.After 14 days of drought,coffee seriously withered,photosynthetic parameters remained near zero and all growth indexes decreased to a certain extent.After 3 days of rehydration,the morphological growth and photosynthetic parameters of seedlings could not return to normal.(2)With the development of drought stress,the contents of soluble sugar,sucrose,starch and NSC and the ratio of soluble sugar to starch in coffee roots increased first and then decreased,while the fructose content and NSC ratio did not change significantly.The ratio of soluble sugar,sucrose,fructose,starch,NSC and NSC ratio in leaves decreased continuously,while the ratio of soluble sugar to starch increased continuously.The contents of soluble sugar,sucrose and fructose,NSC ratio and the ratio of soluble sugar to starch in stems continued to increase,while the starch content continued to decrease,and the content of NSC increased first and then decreased.(3)After 7 days of drought,seedlings tended to accumulate substances in storage organs and change the ratio of soluble sugar to starch in NSC to maintain the relative stability of the whole plant.After 14 days of drought,NSC and its components were consumed in large quantities.NSC tended to continuously convert starch into soluble sugar and transport it to stem to cope with drought stress.Rehydration after 7 days of drought,the soluble sugar in roots had a tendency to transport upward and the carbon allocation strategy of seedlings changed from storage to metabolic consumption.(4)Transcriptome analysis of coffee roots showed that four carbon responsive pathways were screened out from the pathways with significant enrichment of differentially expressed genes,including starch and sucrose metabolism,galactose metabolism,amino sugar and nucleotide sugar metabolism and glycolysis/glyconeogenesis.Sixteen genes related to the change of carbohydrate content of coffee were obtained,including SS,SS2,SSS1,AMY2,BMY1,FK2,INV,SUC6,GAL,Gal K,HK2,PK1,PKMG,PFK2,PFK3 and their expression pattern was consistent with the trend of carbohydrate content change.