トマトにおける果実生長および光合成産物の転流の動態に対する環境作用 （第３報） 塩ストレスの影響

Abstract

Effects of salt stress on dynamics of expansive growth and water balance in a growing fruit of tomato (Lycopersicon esculentum Mill.) were analyzed by evaluating components of fruit water balance such as phloem sap and xylem sap fluxes through the pedicel. Salt stress was induced by adding NaCl to the hydroponic nutrient solution. The major part of sap flux into the fruit through the pedicel was brought by phloem sap flux, which was scarcely affected by the salt stress. On the other hand, 34% depression was found in xylem sap flux under the salt stress. These responses of phloem sap and xylem sap fluxes resulted in 25% depression in fruit expansive growth and the higher contribution of phloem sap flux under salt stress, where 83% of sap accumulated into the fruit was phloem sap and the contribution of xylem sap was only 17%. Thus, the separate evaluations of phloem sap and xylem sap fluxes into the fruit can suggest quantitatively that salt stress results in smaller tomato fruits with higher sugar concentrations and higher incidence of blossom-end rot.