Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824-1312.
Plant Physiol. 1992 Jul;99(3):1156-61. doi: 10.1104/pp.99.3.1156.
Submergence induces rapid elongation of rice coleoptiles (Oryza sativa L.) and of deepwater rice internodes. This adaptive feature helps rice to grow out of the water and to survive flooding. Earlier, we found that the growth response of submerged deepwater rice plants is mediated by ethylene and gibberellin (GA). Ethylene promotes growth, at least in part, by increasing the responsiveness of the internodal tissue to GA. In the present work, we examined the possibility that increased responsiveness to GA was based on a reduction in endogenous abscisic acid (ABA) levels. Submergence and treatment with ethylene led, within 3 hours, to a 75% reduction in the level of ABA in the intercalary meristem and the growing zone of deepwater rice internodes. The level of GA(1) increased fourfold during the same time period. An interaction between GA and ABA could also be shown by application of the hormones. ABA inhibited growth of submerged internodes, and GA counteracted this inhibition. Our results indicate that the growth rate of deepwater rice internodes is determined by the ratio of an endogenous growth promoter (GA) and a growth inhibitor (ABA). We also investigated whether ABA is involved in regulating the growth of rice coleoptiles. Rice seedlings were grown on solutions containing fluridone, an inhibitor of carotenoid and, indirectly, of ABA biosynthesis. Treatment with fluridone reduced the level of ABA in coleoptiles and first leaves by more than 75% and promoted coleoptile growth by more than 60%. Little or no enhancement of growth by fluridone was observed in barley, oat, or wheat. The involvement of ABA in determining the growth rate of rice coleoptiles and deepwater rice internodes may be related to the semiaquatic growth habit of this plant.
淹没会导致水稻幼茎（Oryza sativa L.）和深水稻节间迅速伸长。这种适应性特征帮助水稻从水中生长出来并在洪水泛滥中存活。早些时候，我们发现，受淹没的深水稻植株的生长反应是由乙烯和赤霉素（GA）介导的。乙烯通过增加节间组织对 GA 的反应性至少部分促进生长。在本工作中，我们研究了增加对 GA 的反应性是否基于内源脱落酸（ABA）水平的降低的可能性。淹没和用乙烯处理在 3 小时内导致深水稻节间的居间分生组织和生长区的 ABA 水平降低 75%。同时，GA(1)的水平增加了四倍。激素处理也可以显示 GA 和 ABA 之间的相互作用。ABA 抑制了淹没的节间生长，而 GA 则抵消了这种抑制作用。我们的结果表明，深水稻节间的生长速率由内源性生长促进剂（GA）和生长抑制剂（ABA）的比例决定。我们还研究了 ABA 是否参与调节水稻幼茎的生长。将水稻幼苗种植在含有氟啶酮的溶液中，氟啶酮是类胡萝卜素的抑制剂，间接也是 ABA 生物合成的抑制剂。用氟啶酮处理可使 coleoptiles 和第一叶中的 ABA 水平降低 75%以上，并使 coleoptile 生长增加 60%以上。在大麦、燕麦或小麦中，几乎没有或没有观察到氟啶酮对生长的增强作用。ABA 参与决定水稻幼茎和深水稻节间生长速率的原因可能与该植物的半水生生长习性有关。
