Changes in carbohydrate and water contents of kiwifruit (Actinidia deliciosa) during growth

Abstract

The concentration of a constituent in a fruit, which is often related to fruit quality, is caused by changes in the accumulation of a constituent, water, or both. In this study, changes in dry matter percentage and sugar concentration of 'Hayward' kiwifruits were analyzed with respect to the accumulation of dry matter, sugars, or water during growth in 1995 and 1996. Fruit growth curve by fresh weight and water content showed a clear double sigmoid curve, whereas that based on dry matter did not. Percentage of dry matter, which increased until the end of stage II, decreased immediately after the start of stage III, and then recovered gradually. The decrease in dry matter was accompanied by a rapid inflow of water into the fruit, which indicates that the increase in water import into fruits is responsible for the re-starting of rapid growth at the beginning of stage III. During the latter half of stage III, dry matter content increased without an increase in water content. Starch concentration increased during stages I and II to reach a plateau at the beginning of stage III. Toward the end of stage III, starch concentration decreased, and total sugar concentration increased rapidly. Since no change in water content occurred during this period, the increase in total sugar content reflected directly to the concentration.