Shigeo Imada

Sucrose synthase and sucrose phosphate synthase, but not acid invertase, are regulated by cold acclimation and deacclimation in cabbage seedlings

Summary Cabbage seedlings acquire freezing tolerance during exposure to low temperature (acclimation), however, it is lost by returning the plants to moderate temperature (deacclimation). Soluble sugars, except myo -inositol, accumulated during cold acclimation in the leaves of cabbage seedlings. During deacclimation for 5 days, sucrose, glucose and fructose contents decreased rapidly to the same levels as before cold acclimation. To identify the enzymes responsible for changes in sugar concentrations, we investigated changes in activities of sucrose synthase (E.C. 2.4.1.13), sucrose phosphate synthase (E.C. 2.4.1.14) and acid invertase (E.C. 3.2.1.26) during cold acclimation and deacclimation. Activity of sucrose synthase during cold acclimation increased up to 3 times the activity before cold acclimation, but decreased to the level of activity before cold acclimation during deacclimation. The activity of sucrose phosphate synthase also increased during cold acclimation, but decreased to the level of activity before cold acclimation during deacclimation. However, the activity of acid invertase decreased gradually during cold acclimation and did not increase to the level of activity before cold acclimation during deacclimation. These results suggest that SS and SPS, but not acid invertase, are regulated by cold acclimation and deacclimation and play important roles in sugar accumulation and acquisition of freezing tolerance in the leaves of cabbage seedlings.

Growth dependence of ovaries of facultatively parthenocarpic eggplant in vitro on indole-3-acetic acid content

This work was undertaken to investigate the growth of tissue-cultured ovaries of facultatively parthenocarpic eggplant in vitro in relation to their indole-3-acetic acid (IAA) content. Ovaries isolated from facultatively parthenocarpic eggplant (Solanum melongena L. cv Talina) and nonparthenocarpic eggplant (S. melongena L. cv Senryo-nigo) were grown under tissue culture conditions. The ovaries of facultatively parthenocarpic eggplant grew for 40 days on hormone-free medium when sucrose concentration was 50‐70 g l ˇ1 . The growth of ovaries of non-parthenocarpic eggplant ceased after 10 days. The ovaries of facultatively parthenocarpic eggplant on the medium containing 2,3,5-triiodobenzoic acid (TIBA) did not develop at all. The levels of IAA in the ovaries of both facultatively parthenocarpic and non-parthenocarpic plants were identical at excision, but were higher in ovaries of facultatively parthenocarpic than in those of non-parthenocarpic eggplant and ovaries of facultatively parthenocarpic eggplant grown on the medium containing TIBA at 20 and 40 days after culture initiation. Our findings indicated that the growth of the ovaries of facultatively parthenocarpic eggplant is supported by the availability of endogenous IAA. # 1999 Elsevier Science B.V. All rights reserved. Scientia Horticulturae 79 (1999) 143‐150