THE EFFECTS OF WATER-STRESS ON THE GROWTH, SUGAR AND NITROGEN-CONTENTOF CHERRY TOMATO FRUIT

Cherry tomato (Lycopersicon esculentum Mill. cv. Pike) plants were dri p-irrigated at four soil moisture levels (pF 1.5, pF 2.0, pF 2.5 and p F 2.9) from the 17th day before fruits on the first cluster reached th e red ripe stage. Under high water stress (pF 2.9), the total dry weig ht and water content of the plant decreased, compared to other treatme nts. However, the proportion of fruit dry weight per plant gradually i ncreased proportionately to the pF, but the proportion of the leaf and root dry weight decreased. The total sugar content of the fruit incre ased as the pF value rose, but that of sucrose was lower than that of glucose and fructose under all of water conditions. Starch content in the fruit was equal and decreased during its ripening in all treatment s. Although the water content of the fruit decreased with higher water stress, the difference in concentration among the four conditions was within 3% so that the sugar concentration was barely affected. Total nitrogen content and the nitrogen content in the water soluble protein under water stress at pF 2.9 mere lower than thoes at pF 1.5 which su ggests that the low nitrogen content may account for the high sugar co ntent. We conclude that the optimum pF value ranges between pF 2.5 and 2.9, within which is optimum tomato fruit quality without any reducti on in yield.