Short-and long-term effects of carbohydrate limitation on sugar and organic acid accumulation during mandarin fruit growth

BACKGROUND: The physiological roles of organic acids in fruit cells are not fully understood, especially in citrus, whereas the decline in titratable acidity during ripening shown by many citrus fruits is due to the utilization of citric acid. We induced carbohydrate depletion by removing source leaves at two key periods in mandarin development (early and full citric acid accumulation). Then, we assessed the resulting changes in the short term (within 48 h) and long term (several weeks until ripening). RESULTS: Control mature fruits were characterized by elevated fresh weight, large diameters and high quantities of malic acid, citric acid and sucrose. At the same stage, fruits subjected to early or late defoliation had higher glucose, fructose, citric acid concentrations and lower sucrose concentrations. They differed only in their malic acid concentrations, which were higher in early defoliation fruits and similar in late defoliation fruits when compared to control fruits. Finally, fruits subjected to late defoliation were characterized by high proline and í µí¼¸minobutyric acid concentrations, and low fructose and glucose concentrations. CONCLUSION: We have shown that short-and long-term carbohydrate limitation modifies sugar and organic acid metabolism during mandarin fruit growth