Influence of assimilate and water supply on seasonal variation of acids in peach (cv Suncrest)

Seasonal variations of acid concentrations in peach fruit (cv Suncrest) were investigated in relation to assimilate and water supply for four years. The leaf/fruit ratio and girdling of the shoots on both sides of the fruit pedicel were used to manipulate the assimilate supply. Irrigation intensity was used to manipulate the water supply. There was a positive relationship between assimilate or water supply and fruit growth. The responses of organic acids to assimilate supply were different with fruit development. At the beginning of growth, fruits with high leaf/fruit ratio had lower malate and higher citrate concentration. Near maturity, greater assimilate supply is related to high malate and low citrate concentration. High leaf/fruit ratio increased quinic acid concentration at the beginning of growth. With development, quinic acid concentration in fruits with more assimilate supply decreased more. Shikimic acid concentration fluctuated differently with fruit development in the four years and was generally lower in fruits with more leaves. Irrigation tended to reduce acid concentrations but did not affect the seasonal patterns of the different acids. There were no interactions between tree irrigation and leaf/fruit ratio.