Intracellular compartmentation and membrane permeability to sugars and acids at different growth stages of peach

• We determine distributions of sugars and acids with compartmental analysis method.
• We examine the alteration of sugars and acids in vacuole, cytoplasm and free space.
• Membrane permeability to sugars and acids are measured at different growing stages.
• We analyze distributions of sweetness and sour in different compartments of cells.

The aim of the present work was to evaluate the distribution of sugars and acids in vacuoles, cytoplasm, and free space in peach fruits picked at premature (June 22) and mature (July 22) stages and assess the membrane permeability to sugars and acids. The results showed that sugars (sucrose, glucose, fructose and sorbitol) and acids (malate, citrate, quinate and shikimate) in vacuole, cytoplasm and free space were 1.0, 2.3 and 2.4 mg g−1, and 0.15, 0.31 and 0.72 mg g−1, respectively, in immature fruit, 27.4, 11.5 and 9.0 mg g−1, and 1.97, 0.96 and 0.32 mg g−1, respectively, in mature fruit. Vacuole was the main site for sugar and acid deposits in maturity. Sucrose and malate accounting for 80.6% and 77.3% of total sugars and acids, respectively, in mature fruit were principal accumulation form in ripe peach fruit. The permeability through plasma membrane and tonoplast decreased with peach fruit maturation. The tonoplast with lower permeability was the most resistant barrier to sugars and acids release. The permeability of sorbitol across plasma membrane in immature fruit with a releasing rate of 41.1 × 10−3mg g−1 min−1 was the highest value among all velocity constants. The sweetness and sour distributed in vacuole accounted for 57.3% of total sweetness and 59.9% of total acidity, respectively, which indicated that sweetness and sour were mainly located in vacuole.