Study On The Changes Of Sugar And Organic Acid Components And Accumulation Properties In Pear Fruits

P. pashia, P. calleryana, P. betulaefolia and their scion cultivar ’Hosui’ were used as experimental materials in this study. The components and contents of sugars and organic acids in leaves, petioles, fruit spurs, fruit stalks and pulps were determined by HPLC. The effects on components and content changes of sugars and organic acids in ’Hosui’ pears caused by rootstocks were analyzed, as well as the characteristics of sugar and organic acid accumulation in pear fruits during fruit development were discussed. The main results were as follows:l.The method to determine sugars in pear fruit by HPLC-RID was established. The column was Transgenomic CARBO sep CHO620 column, flow rate was 0.5ml/min, the column temperature was 80 ℃, the injection volume was 5μl, and the RID cell temperature was 35 ℃.Under the experimental conditions, the correlation coefficient was 0.999, the detection limit was 2.415-3.636mg/L, the standard deviation (RSD) was 0.9933%-1.2797%, and the recovery was up to 95.2582%.2. Main accumulation sugar was sorbitol in young fruits, and it was fructose in mature fruits. Sucrose wasn’t accumulated in fruits at the early development period, while it was accumulated in fruits rapidly at later development stage. Main accumulation organic acid was quininic acid in young fruits, and it was malic acid and citric acid in mature fruits.3.Total soluble sugar and sorbitol contents were high in ’Hosui’ pear fruits, while it was grafted on P. calleryana with low total soluble sugar and sorbitol contents in fruits.Total soluble sugar and sorbitol contents were low in ’Hosui’ pear fruits, while it was grafted on P. betulaefolia with high total soluble sugar and sorbitol contents in fruits.4. There was a regulatory role in components and content changes of organic acids by rootstocks for their scion cultivar’Hosui’. The content of citric acid would be decreased when the ’Hosui’ pear was grafted on P. betulaefolia, the ratio of malic acid accounted for citric acid would be increased, and the quality in fruits would be improved.5. During slowly growth period there was no sucrose in pulps and the content of sucrose was also very low in leaves, fruit spurs and fruit stalks, but there was no fructose in leaves and petioles. Because sorbitol was rich in leaves, petioles, fruit spurs, fruit stalks and pulps during fruit growth period, and fructose was frequent in pulps in mature, it was believed that sorbitol was the main transported sugar in pear fruits where the sorbitol could be turned into fructose or other sugars.6. Since citric acid could not be measured in fruit spurs and fruit stalks during the slowly growth period of fruits, Citric acid in fruits might be synthesized in pulp itself. The contents of quinine acid, malic acid, oxalic acid and shikimic acid in petioles and fruit stalks which were classified as transporting organs were higher than those in leaves and pulps. It was thought that the some organic acid could be transported among the different tissues or organs consisted of leaves, petioles, fruit spurs, fruit stalks and pulps in pear trees.