Abstract
Cherry tomato (Lycopersicon esculentum Mill. cv. Piko) plants were drip-irrigated at four soil moisture levels (pF 1.5, pF 2.0, pF 2.5 and pF 2.9) from the 17th day before fruits on the first cluster reached the red ripe stage. Under high water stress (pF 2.9), the total dry weight and water content of the plant decreased, compared to other treatments. However, the proportion of fruit dry weight per plant gradually increased proportionately to the pF, but the proportion of the leaf and root dry weight decreased. The total sugar content of the fruit increased 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 treatments. 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 were lower than thoes at pF 1.5 which suggests that the low nitrogen content may account for the high sugar content. We conclude that the optimum pF value ranges between pF 2.5 and 2.9, within which is optimum tomato fruit quality without any reduction in yield.
