Isolation of Vacuoles from Immature Apple Fruit Flesh and Compartmentation of Sugars, Organic Acids, Phenolic Compounds and Amino Acids1

摘要

Vacuoles of immature apple fruit (Malus pumilaMill. var.domesticaSchneid.) were obtained by purification using Ficoll density gradient centrifugation after lysis of the protoplasts by both mild osmotic shock and the addition of EDTA and BSA. The recovery was about 35of the protoplasts. The isolated vacuoles had a mean diameter of about 100μm.The distribution of sugars, organic acids, phenolic compounds and amino acids in the vacuole, the cytoplasm and the free space was determined. Almost all of the fructose and glucose, the major sugars of the tissue, were found in the vacuole. Sorbitol was mainly located in the free space and the vacuole, and sucrose in the free space and the cytoplasm. More than 90of the malic acid, the main organic acid, was located in the vacuole. Almost all of the phenolic compounds were also deposited in the vacuole.The volumes of the vacuole, the cytoplasm and the free space in the whole tissue were calculated from the cell numbers of the whole tissue, the volume of the isolated protoplasts, and the volume of the vacuoles present in the protoplast. The solute concentration in each compartment was estimated: vacuoles, 888 mm; cytoplasm, 37 mm; free space, 57 mm. How these compartmentations of solutes affected the translocation of sugars into the fruit and the cell expansion is discussed