Cytochemical localization of ATPase during fruit development of Lycium barbarum L.

The distribution of ATPase in phloem and the flesh sink-cells during fruit development of Lycium barbarum L.was studied by the conventional ATPase cytochemical positioning technology.This study aims at a better insight into the phloem unloading pathway in fruit of Lycium barbarum L.The results showed that there was a symplasmically isolation between the SE-CC complex and its surrounding cells over the fruit development.And there were less plasmodesmata among the phloem parenchyma cells and the flesh sink-cells.However,there were more plasmodesmata in phloem parenchyma cells adjacent the flesh sink-cells.Numerous vesicles and membrane bubbles were found in the sieve element,phloem parenchyma cells and the flesh sink-cells.The ATPase sediments of the plasma membrane,vesicle membrane and tonoplast were higher in the flesh sink-cells than that in the phloem parenchyma cells,especially in the second rapid growth of fruit,and during this time the ATPase activity was dramatically increased on the membrane system of the flesh sink-cells,cell wall and the intercellular space.The distribution of the ATPase on the plasma membrane of the flesh sink-cells appeared polarity characteristics.It is considered that the phloem unloading is energy-driven process and the apoplastic route is the main pathway of the assimilate unloading over fruit development.However,symplastic and apoplastic pathway may coexist during assimilate unloading from the phloem to the flesh sink-cells.The vesicular transport is the important way of the fruit assimilates unloading and transfer.The phloem parenchyma cells perform the main transport role during the assimilate unloading and transfer.The flesh sink-cells possess strong active transport and transit-oriented capacity in assimilates accumulation.