Effects of Water Flow from the Xylem on the Growth-induced Water Potential and the Growth-effective Turgor Associated with Enlarging Tomato Fruit

摘要

Intact tomato {Solarium lycopersicum L.) fruit growth was monitored while heat-girdling treatment was conducted. Heat-girdling treatments revealed that most water flow into enlarging fruit of tomato plants originated from the xylem throughout fruit growth periods. After measuring the water status and growth rates simultaneously, the growth parameters of Lockhart's equation were determined in expanding fruit of tomato plants. During the early stage of fruit growth, when, the growth-induced water potential was obtained by calculating the difference between water potentials of the growing region and the water source, it was found that sizes of the growth-induced water potential and the hydraulic conductance were predominant factors to regulate cell expansion. When fruit became almost mature, sizes of the growth-effective turgor and the wall extensibility were primary factors to regulate cell expansion, but not the water potential gradients. Such changes in water flow from the xylem related to enlarging processes of fruit may explain how fruit cracking takes place right before fruit maturation.