|Budget Amount *help
¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Monocarpic senescence is induced by flowering and/or fruiting. In soybean plants, removal of young immature pods which seem to have small sink activity retarded the commencement of senescence greatly, suggesting that the senescence is not due to the competition of nutritional compounds between pods and vegetative parts, and that immature pods secrete some senescence-inducing compounds to induce senescence of the whole plants. Sice abscisic acid (ABA) is one of the candidate for the senescence-promoting compounds, time course changes in the levels of ABA were examined by HPLC.The maximum level of ABA (ca.5 mug/g fresh weigh) was found in the 3-week-old pods (3 weeks after flowering). On the other hand, chlorophyll retention test which was carried out by the first leaves of wheat showed the presence of strong senescence-promoting activity in the ethyl acetate-soluble fraction obtained from the pods. The maximum activity was found in the fraction of 3-week-old pods, and the level kept constant until 7 weeks after flowering. In terms of ABA equivalent, the maximum senescence-promoting activity was 25 mug/g, the value being 5 times larger than the level of ABA.The result suggests the presence of some other senescence-inducing compound(s) in the fraction. Purification and identification of the compound are now in progress.