The Sugar-acid Components Of 'Fengtang Plum' Fruit And The Regularity Of Them Accumulation

'Fengtang plum'?P.salicina'Fengtang plum'?was a special kind of local plum in Guizhou.It has high commercial value due to its extremely high sugar content and unique flavor.With'Fengtang plum'and its contrast varieties?Siyue plum‘?P.salicina?Siyue plum‘?as experimental material,the composition and content characteristics of sugar and acid,dynamic changes of sugar and acid and their relationship with related metabolic enzymes were studied.To clarify the accumulation pattern of sugar and acid components of'Fengtang plum',and provided the basis for further study on the characteristics of high sugar accumulation.Following is major results of this paper:1?The content of soluble sugar in the fruit of'Fengtang plum'reached 82.65 mg·g^-1FW and the titratable acid was 6.81 mg·g^-1FW.4 kinds of sugar and 6 organic acids were detected in the fruit of'Fengtang plum'.Sugar included sucrose,fructose,glucose and sorbitol,mainly sucrose,accounting for 40.36%of total sugar,roughly 10 times the sucrose content of plum in?Siyue plum‘.Organic acids included malic acid,tartaric acid,citric acid,oxalic acid,shikimic acid and succinic acid,mainly malic acid,accounting for 88%of total acid content,significantly lower than?Siyue plum‘.The contents of total sugar increased while the contents of glucose,fructose and sorbitol increased first and then decreased during the development of the fruit of'Fengtang plum',and sucrose content increased rapidly during fruit ripening,while?Siyue plum‘sucrose did not increase significantly during ripening stage.The key period for the accumulation of malic acid in the fruit of'Fengtang plum'was in the growth stage of young fruit.The overall change trend of malic acid first increased and then decreased.The content of oxalic acid and tartaric acid decreased and the content of citric acid increased gradually.Compared with the?Siyue plum‘,the trend of malic acid,oxalic acid,tartaric acid and total acid content in the fruit of'Fengtang plum'was the same,and the content of malic acid and total acid was significantly lower than that of?Siyue plum‘in the whole process,but the trend of citric acid content was opposite.2?The activity of sucrose synthase-cleavage direction?SS-cd?decreased gradually with the growth and development of'Fengtang plum'fruit,while the activity of sucrose synthase-synthesis direction?SS-sd?showed a trend of?up-down-up-down?,and the growth rate of SS-sd was much larger than that of?Siyue plum‘in the fruit ripening period.The activity of sucrose phosphate synthase?SPS?in was larger in the whole'Fengtang plum'fruit development stage,while the?Siyue plum‘was more gradual.The activity of acid invertase?AI?and neutral invertase?NI?in the fruit of'Fengtang plum'showed a trend of increasing first and then decreasing,while the activity of?Siyue plum‘in the growth and development of fruits continued to increase.The activity of fructose kinase?FK?and glucose kinase?GCK?in the fruit of'Fengtang plum'increased continuously and was similar to?Siyue plum‘.The sorbitol dehydrogenase?SDH?activity in the fruit of'Fengtang plum'showed a?down-up-down-up?trend,the activity of sorbitol oxidase?SOX?decreased first,but increased during the mature period.The activity of NAD-Malate Dehydrogenase?NAD-MDH?in the fruit of'Fengtang plum'and?Siyue plum‘had a significant difference during the different stages of fruit growth and development.The activity of NAD-MDH in the'Fengtang plum'fruit was fluctuated within the range of 82.24¹69.12 U·mg^-1FW,and relatively smooth change.The change of NAD-MDH activity in?Siyue plum‘showed M type,which was higher than that of'Fengtang plum'.The activity of NADP-malic enzyme?NADP-ME?in'Fengtang plum'was similar to that of the control group,young fruit enlargement period of enzyme activity decreased,increased at maturity.But the difference was that the activity of NADP-ME in the fruit of'Fengtang plum'was always significantly lower than that of?Siyue plum‘.The change of phosphoenolpyruvate carboxykinase?PEPC?activity in the fruit of'Fengtang plum'exhibited a M type,except for the rest of the fruit ripening period was significantly higher than?Siyue plum‘.The activity of PEPC in?Siyue plum‘fruit changed smoothly during the whole development period of fruit.3?In the ripening stage of the fruit development of'Fengtang plum'fruit,the rapid accumulation of sucrose was mainly due to the significant enhancement of SPS and SS-sd activity close to fruit maturity,which promoted the synthesis of sucrose and decreased the activity of SS-cd to reduce the decomposition of sucrose.Comparing with?Siyue plum‘,the activity of AI and NI in the fruit of'Fengtang plum'was similar,but the activity of SPS and SS-sd was significantly higher than that of?Siyue plum‘,and the SS-cd overall activity was lower than that of?Siyue plum‘,making the sucrose content of'Fengtang plum'significantly higher than?Siyue plum‘.There was a significant positive correlation between malic acid content and NAD-MDH activity in the two cultivars,and the correlation coefficients were 0.97**,0.95**,respectively.The activity of NADP-ME was significantly negatively correlated with the change of malic acid content,and the correlation coefficient was-0.86**,-0.87**,respectively.The correlation analysis showed that there was a significant positive correlation between the activity of PEPC and the content of malic acid in the fruit of'Fengtang plum'and?Siyue plum‘,and the correlation coefficient was 0.75*and 0.73*,respectively.It was the early stage of fruit development that was the critical period of accumulation of malic acid in the fruit of'Fengtang plum'.And mainly because the enhanced activity of PEPC promote the synthesis of malic acid and the decreased activity of NADP-ME to reduce the decomposition of malic acid,and NAD-MDH made little effect.However the key enzyme accumulated for?Siyue plum‘malic acid was NAD-MDH.In the ripening stage fruit development,the activity of NADP-ME increased rapidly in the both cultivars,the activity of PEPC in'Fengtang plum'was weakened,the NAD-MDH in?Siyue plum‘activity decreased.And thus the degradation of malic acid was greater than the synthesis and the content of malic acid became lower in the both cultivars.4?Ratio between soluble sugars contentand tartanc acid content were increased with the growth and development of the'Fengtang plum'fruit,and the ratio between soluble sugars contentand tartanc acid content is up to 14.01 when the fruit ripen.Compared with?Siyue plum‘,the variation trend of sugar acid ratio in the'Fengtang plum'fruit was consistent with that,but the whole stage of fruit development was significantly higher than that of?Siyue plum‘.By analyzing the correlation between sugar acid content,it was found that:there was a close relationship between the sugar-acid in the process of the accumulation of sugar-acid,and the correlation coefficient reached-0.91**and-0.93**.There was a strong correlation between oxalic acid and shikimic acid and sugar.