Relationship between photosynthesis characteristics and starch accumulation of Pueraria lobata during different growth stages

ObjectiveRelationship between photosynthesis characteristics and starch accumulation of Pueraria loba-ta during different growth stages was studied in order to provide some theoretical references for the regulation and quality improvement in starch accumulation of P.lobata.MethodGuige 1 and Guige 8 were used as experimental materials. The photosynthetic parameters such as net photosynthetic rate(Pn),stomata conductance(Gs),intercellular CO2concentration (Ci)and transpiration rate(Tr),as well as the contents of amylose and amylopectin in root tuber were determined.The total starch content was calculated.At the same time,fresh weight per plant and dry matter content were determined to analyze the variation trend of each index in different growth periods and their relationships between one and one another.ResultThe changes of Pn,Gs,Ciand Trin leaves of Guige 1 and Guige 8 showed a unimodal curve from June to December,and they all reached the peak in October,then decreased rapidly.The photosynthetic parameters during the whole growth period of Guige 8 were larger than Guige 1 in general.The contents of amylose,amylopectin and total starch in root tuber of two P.lobata varieties increased gradually from June to December,accumulated rapidly from June to October,and in-creased slightly or tended to be stable after October.In various periods,amylose content of Guige 1 was higher than that of Guige 8,while amylopectin content of Guige 8 was higher than that of Guige 1.The changes of total starch content and amylopectin content were basically consistent.The fresh weight per plant and dry matter content of Guige 8 during the whole growing period were higher than those of Guige 1.The variation trend of the two indexes was consistent,which showed a slow increase from June to October and a rapid increase after October.The results of correlation analysis showed that there was extremely significant(P<0.01,the same below)or significant positive(P<0.05,the same below)correla-tion between Pn,G s,Ciin leaves of P.lobata and amylopectin content.Pn,G s,Ciin leaves of P.lobata were significantly positively correlated with total starch content,they were also positively correlated with amylose content,root tuber fresh weight per plant and dry matter content,but the correlation was not significant(P>0.05).There was extremely significant positive correlation between amylopectin content,total starch content,and amylose content,fresh weight per plant and dry matter content.ConclusionThe Pn,G s,Ciin leaves of P.lobata are positively correlated with amylopectin content and total starch content,and reach extremely significant or significant levels.Therefore,they could be used as reference indexes to predict the starch content and yield of P.lobata.