This study was conducted to obtain the basic informations on the mechanism of bulb formation and secondary grow th in garlic. The effect of short day (8hr) treatment on growth and the level of endogenous growth substances were investigated. Also, total sugar content and concentrations of N, P, K, Ca were measured. The results summarized are as follows.
1. Short day treatment resulted in the suppression of growth, no bulb formation and induction of secondary growth.
2. Under the natural day length ABA-like substances and unknown inhibitor(s) were detected in the leaf blade extracts with an increasing activity in the course of leaf senescence, while gibberellin- and ABA-like substances in the extracts from bulb with leaf sheath.
3. Under the short day length gibberellin- and ABA-like substances in the leaf blade extracts were detected, but only the gibberellin-like substances in the extracts from bulb with leaf sheath. and the activity increased in the former extracts, while decreased in the latter.
4. The activity of ABA-like substances in bulb sampled at 25th day after harvest was much higher than that sampled before storage, whereas the activity of gibberellin-like substances decreased during the period of storage.
5. Total sugar level of the plants under the natural day length was higher than those under short day.
6. Short day treatment tended to increase the concentrations of mineral nutrients(N, P, K, Ca) as compared to natural day length.
7. In conclusion, a high activity of ABA-like substances and high level of total sugar was considered to be the major internal factors that are closely related bulb formation, and gibberellin-like substances was not considered so.
8. The result obtained in this experiment suggests that the secondary growth in garlic be induced by a high activity of gibberellin-like substances with little or no ABA-like substances.
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