Vol. 81 No: 6

Title:
Seasonal changes in cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in 'Orin' apples

Authors:
H. YAMADA, T. OKUMURA, Y. MIYAZAKI and S. AMANO

pp: 1069-1073

Abstract:
The intensity of watercore in ´Orin` apples (Malus × domestica Borkh.) from the outer canopy increased from early-July to mid-August, followed by a decrease through late-October, while no watercore was detected in inner canopy fruit during the same period. Seasonal changes in sorbitol content in each cellular compartment paralleled the development of watercore. Significantly higher sorbitol, fructose and glucose contents in the vacuoles of cells in outer canopy fruit than in inner canopy fruit suggest that active metabolism and uptake of sorbitol might occur in watercored apples in mid-August. The permeability of sorbitol across the tonoplast was significantly higher in outer than in inner canopy fruit after mid-August, whereas no difference was observed between bearing position for the other sugars or for the plasma membrane. These data suggest that elevated sorbitol levels in the intercellular spaces might result from active apoplastic unloading and not from an inhibition of metabolism and/or an increase in leakage from cells.

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