Shousaku Horiuchi

Involvement of polyamines in gibberellin-induced development of seedless grape berries

The roles of polyamines (PAs) in the development of seedless grape berries induced by gibberellin (GA3) was investigated. The development of seedless grape berries was stimulated by the application of putrescine (Put), but not by that of spermidine (Spd) and spermine (Spm), regardless of the presence of GA3. At harvest, the fresh weight of seedless grape berries treated with 500 ppm Put + 25 ppm GA3 and 500 ppm Put increased to 111 and 112%, respectively, of the control. Treatment with methylglyoxal-bis (guanyl hydrazone), a potent inhibitor of S-adenosylmethionine decarboxylase that plays a role in Spd and Spm synthesis, did not affect the development of seedless grape berries induced by 100 ppm GA3. The application of 100 ppm GA3 significantly increased endogenous free Put levels. Levels of free Spd and Spm were not affected by GA3. Although the levels of endogenous perchloric acid insoluble bound PAs were higher than those of free PAs, obvious changes in the levels of bound PAs were not observed. These results indicate that free Put is implicated in the development of seedless grape berries induced by GA3.

The Role of Glutathione on the Onset of Endodormancy of Grape Buds

The role of glutathione, which maintains protein thiol groups in the reduced state in living cells, on the onset of endodormancy (rest) of grape buds was investigated. When potted grapevines were exposed to 30°C/25°C (high), day/night, or 20°C/15°C (low), day/night, before the onset of bud dormancy, buds administered low temperature became dormant, but those treated with high temperature did not. On shoots treated with low temperature, endogeneous ABA levels increased soon after treatment, whereas ABA levels in shoots treated with high temperature remained low. Reduced glutathione (GSH) content in the shoots treated with high temperature increased, whereas in shoots treated with low temperature, it decreased gradually. Oxidized glutathione (GSSG) content in the shoots treated with high temperature remained almost constant during the experimental period, whereas under the low temperature treatment it increased. GSSG content increased in shoots induced to dormancy by the ABA treatment. Furthermore, exogenous treatment with GSSG inhibited budbreak. Therefore, we conclude that glutathione is one of the potent factors in controlling grape bud dormancy.

CHANGES IN CARBOHYDRATE AND WATER CONTENT WITH OVULE GROWTH OF GINKGO BILOBA L.

SummaryThe carbohydrate and water contents of the ovule of Ginkgo biloba L. (ginkgo) were evaluated during its development. The ovule grew rapidly (stage I) after pollination in early May, temporarily stopped growing, in mid-July (stage II), and resumed growth slowly (stage III) from mid-August until maturation. The water content in the endosperm and outer integument were highest in June, and decreased thereafter, accompanied by ovule development. In the endosperm, the sugar content decreased rapidly during stage I, followed by a rapid increase in the starch content which is high level in early September. In the outer integument, the sugar content increased in early June, and remained nearly constant until early August. Then it transiently decreased in mid-August, when meso-integument hardening was completed, followed by a rapid increase. The starch content in the outer integument was low, but peaked in mid-August, when the sugar content was lowest. Although ginkgo nuts are usually harvested in October, w...

JASMONIC ACID EFFECTS ON GIBBERELLIC ACID-INDUCED SEEDLESSNESS IN 'NEO MUSCAT' TABLE GRAPES

SummaryThe effect of jasmonic acid (JA), applied alone or in combination with gibberellin A3 (GA3), on the induction of seedlessness in ‘Neo Muscat’ (Vitis vinifera) was investigated. Endogenous JA levels in the florets of ‘Neo Muscat’ and ‘Delaware’ (Vitis vinifera x Vitis labrusca) were also studied. The proportion of seedless berries induced by application of GA3 alone 12 d before full bloom (DBB) was 17.0%, and at 6 DBB it was 62.7%. The proportion of seedless berries induced by GA3 + JA applied 6 DBB increased significantly with increasing JA concentration, while pollen germination decreased quadratically with increasing JA concentration. JA did not affect seed number per berry or the seed’s fresh weight. Treatment with JA alone also induced seedlessness effectively. Although the fresh weight of the seedless berries induced by the application of GA3 + JA 12 DBB decreased quadratically with increasing JA concentration, there were no significant differences between the treatments at 6 DBB. Fruit solubl...

Changes in indole-3-acetic acid and abscisic acid concentrations during development of the Ginkgo biloba L. ovule

SummarySeasonal changes in the concentrations of indole-3-acetic acid (IAA) and abscisic acid (ABA) in the endosperm and integument of the ovule of Ginkgo biloba L. were analysed by GC-MS using [d5]-IAA and [d6]-ABA as internal standards. The concentration of IAA in the endosperm increased rapidly during the period of rapid growth, and was closely correlated with the growth rate of the ovule. The concentration of IAA in the integument was much lower than that in the endosperm, but also changed similarly. The concentration of ABA in the endosperm showed a peak after the cessation of rapid growth, and decreased during the fertilization period. The concentration of ABA in the integument also increased after the cessation of rapid growth, though slowly.