Study On The Metabolism Of Organic Acid And Regulation In Citrus Fruits

Citrus is one of the most important fruit trees in our country,and also plays an important role in international countries.However,there is a stand out problem that the contents of organic acid is too high,the ratio of sugar/acid is lower which make citrus fruits taste bad. So,it is very important to make sure the rules to metabolism of organic acid,the contents and the regulation methods.This paper does some research of above problems using different genotypes of citrus fruits,the aim is to make sure the dynamic growth of citrus fruits,the rules of metabolism of organic acids,and give some primary methods of regulation.The results as followed:1.The content of organic acid in citrus fruit is one of important guidelines which decide the quality of fruits..So It is important to establishing a effective and precise method to determinate the content of organic acids in citrus fruit.This paper analyzed different mobile phases and its pH with RP-HPLC to find:The mobile phase 20m mol/L KH₂PO₄ +3%methanol has the better results.At the same time we analyzed four different extraction methods for determination organic acids in citrus fruit:The contents of tartaric acid and oxalic acid extracted by 80%ethanol are highest;the contents of citric acid and malic acid extracted by water are highest.2.The contents of water in fruits are always increasing during the whole developments. The changes of vertical and horizontal diameter likes the letter 'S'.The pH value increases first,then decline,and is negative correlation with total organic acids.3.All genotype citrus in this paper accumulate hexose.The components of sugar and total sugars increase during the whole developments of fruits.The contents of glucose in early citrus fruit increase slowly from the end of July to the end of august.The contents of glucose in serotinous citrus fruit increase slowly from the middle of august to the end of September,because some of them are used to synthesized acid.4.The contents of organic acid and the relative enzyme activities of organic acid were studied and their correlation was analyzed during the fruit development of citrus.The results showed that there were citric acid,malic acid,susinic acid,Oxalic acid in fresh citrus fruit.Changes in concentration of citric acid are similar with concentration of all organic acid,while the other acids declined gradually.5.The enzyme activities of MDH,PEPC,CS were all from low to high,then down again. The concentration of malic acid declined was because it was catalyzed to oxaloacetic acid for synthesizing citric acid during the early stage of development.Correlation analyses showed that there was a significant positive correlation between concentration of citric acid and PEPC,CS during anabolism of citric acid,while there was no significant correlation during degradation of citric acid6.Organic solvent and ethychlozate can reduce the contents of acids by reducing the activities of PEPC during the early stage,however the later stage is not effective.7.GA can reduce the total contents of organic acids and citric acid,increase the contents of malic acid, because it can reduce the activities of PEPC and increase the activities of MDH.ABA can increase the contents of organic acids and citric acid,and increase the contents of malic acid,because it can increase the activities of MDH and PEPC.The activities of PEPC,MDH,CS still increase during the degradation stage of citric acid,but the contents of metabolism is less than the contents of degradation,so the contents of total acids and citric acid decline.