Fruit calcium content in relation to phenolic compounds in stalk and berry of young developing fruits of Actinidia deliciosa var. deliciosa

The pattern of phenolic compounds in both berry and fruit stalk of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa), in relation to calcium (Ca) accumulation was studied. Fruit were collected weekly during the early stages of fruit growth, Ca was determined by atomic absorption spectroscopy and phenolics using high performance liquid chromatography techniques. Ca concentrations fell to a minimum value of 0.22% DM by 30-40 days after fruit-set. The predominant phenolic compounds were hydroxycinnamic acids, flavonols and the flavan 3-ol, epicatechin. Generally, phenols reached their lowest concentrations correspondingly to the Ca decrease. Thereafter, only hydroxycinnamic acids in the stalk showed an increase, suggesting that in the berry secondary xylem formation did not occur, thereby accounting for the early cessation of Ca imports into the fruit.