2002 Volume 46 Issue 1 Pages 39-46
Initiation of tuber enlargement in water yam (Dioscorea alata L.) is controlled by under short-day conditions. Jasmonic acid (JA), gibberellins (GAs) and abscisic acid (ABA) are considered to play a role in this phenomenon. However, the relationship between the initiation of tuber enlargement and these endogenous plant hormones has not been elucidated.
Thus, we investigated the relationship between the initiation of tuber enlargement in water yams and the contents of endogenous JA, GAs and ABA in the leaves to compare the plants subjected to short-day conditions with untreated plants. In order to initiate the enlargement of tubers, we exposed 60-days-old plants to a 10-hour day length (short-day treatment) 30 times. After the treatment, we extracted the leaves with 80% methanol and then purified them by silicic acid partition column chromatography. Bioassay for GA activity was carried out using the rice-seedling growth test, and the contents of endogenous JA and ABA were measured by gas chromatography.
We detected endogenous JA, GA-like substances and ABA from yam leaves. Tuber enlargement was initiated by short day treatment, and the content of JA and level of GA-like substances in the leaves increased at the same time. These phenomena suggest that JA and GA like substances may be related to the initiation of tuber enlargement. In contrast, the ABA content did not change after short-day treatment but rather remained constant through out the growth stages under natural conditions. These results suggest that ABA is related indirectly to the initiation of tuber enlargement.
