Factos inducing monocarpic senescence in sovbean plants

一次结实衰老是由开花和/或结果诱导的。在大豆植株中，去除似乎具有小库活性的未成熟的幼荚大大延缓了衰老的开始，这表明衰老不是由于荚与营养部分之间营养物质的竞争，而是未成熟的荚分泌一些衰老诱导物质来诱导整个植株的衰老。脱落酸（阿坝）是促衰老物质的候选物质之一，用高效液相色谱法测定了阿坝含量的时程变化，结果表明，阿坝含量在3周龄豆荚（开花后3周）达到最高，约为5 μ g/g鲜重。另一方面，通过小麦第一叶进行的叶绿素保持试验表明，在从豆荚获得的乙酸乙酯可溶性级分中存在强的衰老促进活性。活性最高的部位是3周龄的荚果，活性水平一直保持到开花后7周。以阿坝当量计，最大衰老促进活性为25 μ g/g，该值是阿坝水平的5倍。该化合物的纯化和鉴定正在进行中。

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.