Poster: Water Relations

Abs # 210: Water-stress-induced changes in water relations and chemical compositions in pericarp of tomato fruit

Presenter:	Zushi, Kazufumi , zushi@pu-kumamoto.ac.jp
Authors	Zushi, Kazufumi  (A)   Matsuzoe, Naotaka  (A)   Yoshida, Satoshi  (B)   Chikushi, Jiro  (B)
Affiliations:	(A): Prefectural University of Kumamoto (B): Biotron Institute, Kyushu University

Water-stress-induced changes in water relations and chemical compositions in tomato fruit were investigated. Pericarps were excised from tomato fruit, and cultured in vitro. The pericarps were incubated for 72 h under the control (MS salts medium containing 4% sucrose; pH 5.5; osmotic potential -0.5 MPa) and the water stress (control medium + 169 g L^-1 polyethylene glycol MW 6000; osmotic potential -1.0 MPa) conditions. The incubation was carried out under a temperature of 25 ^oC and a continuous fluorescent light (60 mmol m^-2 s^-1). Water potential and osmotic potential of the water-stressed pericarp were lower than those of the control. Both the weight and turgor pressure of the water-stressed pericarp decreased rapidly during first 6 h, but afterward the weight recovered to initial values while the turgor pressure remained level. These results indicate that the water stress causes osmotic adjustment in the pericarp. Sugar and amino acid contents per pericarp were higher under the water stress than under the control during the period of 6 to 24 h and 6 to 72 h, respectively. However, organic acid contents remained relatively constant during the period of water stress. Therefore, the osmotic adjustment under the water stress due to the increase in sugar and amino acid contents in the pericarp. Ascorbate content was also higher under the water stress than under the control during first 6 h. However, under the water stress from 24 to 72 h, ascorbate was greatly oxidized into dehydroascorbate. Thus, we could conclude that the contents of sugar, amino acid and ascorbate in tomato fruit are enhanced by the osmotic adjustment and oxidative stress induced by water stress, and that these effects are mainly derived from the desiccation of tomato fruit tissue.