Effects Of Bagging On Sugar Metabolism And Ultrastructure In 'Whangkeumbae' Pear Fruits

Bagging cultivation was one of the most useful techniques for the production of pear fruits with high quality. The technique was applied widely in pear production. However, fruit bagging changed the micro-environment and influenced the normal physiological metabolism. Therefore, the fruit quality in bagging was decreased. It is concluded that fruit bagging affected pear production with high quality in a certain extent.The decline of inherent quality influenced the production with high quality seriously. In order to resolve the new physiological disorders existed in fruit bagging cultivation, the effects of bagging on fruit growth, sugar metabolism and ultrastructure of flesh cell were studied in 'Whangkeumbae 'pear during development with the aim to elucidate the fundamental reason of low quality and provide the theory thereunder for the production of high quality fruits.The effects of bagging on fruit growth and development were studied with 'Whangkeumbae' pear. The results showed that fruit weight and soluble solid content under bagging condition had almost the same change trends of increasement with those of control fruits during the whole developmental stage. Compared with the natural growth fruits, fruit weight and soluble solid content in bagging fruits were much lower in some extents. On the other hand, the results also indicated that fruit firmness and water potential were decreased with fruit development in both bagging and natural growth fruits. And water potential of control fruits was much lower than bagging fruits, but the control fruits' firmness was a little higher than the bagging fruits.The results also showed that the sugar and starch contents and related enzyme activities under bagging conditions had almost the same change trends with those of control fruits during the whole developmental stage. Compared with the natural growth fruits, sugar and starch contents in bagging fruits were much lower in some extents. On the other hand, the results also indicated that bagging fruits increased the activities of invertase and amylase, but decreased the activities of SS and SPS. In the fruits, the POD and PPO activity appeared to rise at first, and then slowly declined; the POD and PPO activity in the bagging fruits were higher than those in the control fruits. Therefore, it was concluded that the changes of activities of related enzymes in sugar metabolism influenced by bagging micro-environment might be responsible for the regulation of fruit growth, sugar accumulation and quality formation.'Whangkeumbae' pear fruit was used to study the effects of bagging on the ultrastructure of flesh cells and vascular bundle cells in developing pear fruits with transmission electron microscopy. The results showed that at the early developmental stage, the ultrastructures of fresh cells in pear fruit were relatively clear and the cytoplasm was more densely, moreover, the main organelles and big center vacuoles were found in the fresh cells. Along with the fruit developing, the amounts of starch grain and the distribution density of plasmodesma increased significantly. At the late developmental stage, the cytoplasm of flesh cell dispersed in vacuoles and the transparency of cell wall decreased slightly. The starch grain hydrolyzed and turned to soluble sugars. On the other hand, the results indicated that the ultrastructure of canaliculus in phloem, such as sieve element/companion cell complex and other organelles had no remarkable changes during fruit development. The results also showed that the micro-environment of bagging affected the ultrastructure of flesh cell and vascular bundle cell. The fresh cell of bagging fruits was not compacter than control. And the starch grains were less. The ultrastructure of vascular bundle cell after bagging was similar with the control. However, the most difference showed that the SE/CC complex were not compacter than control. The cell wall of the SE and CC were thicker than the control.