Benech Arnold R L, Fenner M, Edwards P J
Department of Biology, University of Southampton, Southampton SO9 5NH, UK.
New Phytol. 1991 Jun;118(2):339-347. doi: 10.1111/j.1469-8137.1991.tb00986.x.
The effect of intermittent water stress during grain filling on the germinability of developing seeds of S. bicolor was investigated. The drought treatment was imposed in cycles within the maturation period by withholding water for 5-6 days, rewatering at the end of each drought cycle and withholding water again. Changes in abscisic acid (ABA) content and embryonic sensitivity to ABA in the maturing seeds were also monitored in order to find out if there were any parallel changes with seed germinability resulting from drought conditions. Seeds developing in plants subjected to drought showed a high level of germinability earlier in the maturation period than did control seeds; consequently, they were less resistant to pre-harvest sprouting as shown when panicles were exposed to high humidity conditions. Very high levels of ABA accumulated in the early stages of development in seeds maturing on water-stressed mother plants; however. ABA content fell markedly when the seeds stopped growing, and remained significantly below those recorded in control seeds until the end of the maturation period. Development under drought conditions decreased the sensitivity of the isolated embryo to exogenous ABA by about 10-fold. The good agreement found between germinability, endogenous ABA concentrations and embryo sensitivity to ABA at different stages of development, suggests a key role for ABA as a major inhibitor of precocious germination and shows that changes in germinability caused by water stress during grain filling are likely to be related to changes in ABA pool size in the developing seed.
研究了灌浆期间歇性水分胁迫对二色蜀黍发育种子发芽能力的影响。在成熟期内，通过停水5 - 6天进行干旱处理，每个干旱周期结束时复水，然后再次停水，循环进行。还监测了成熟种子中脱落酸（ABA）含量和胚对ABA的敏感性变化，以确定干旱条件下种子发芽能力的变化是否与之平行。与对照种子相比，遭受干旱的植株上发育的种子在成熟期较早阶段具有较高的发芽能力；因此，当穗暴露于高湿度条件下时，它们对收获前发芽的抗性较低。在水分胁迫的母株上成熟的种子，在发育早期积累了非常高的ABA水平；然而，当种子停止生长时，ABA含量显著下降，直到成熟期结束一直显著低于对照种子中的记录水平。干旱条件下的发育使离体胚对外源ABA的敏感性降低了约10倍。在发育的不同阶段，发芽能力、内源ABA浓度和胚对ABA的敏感性之间的良好一致性，表明ABA作为早熟萌发的主要抑制剂起关键作用，并表明灌浆期水分胁迫引起的发芽能力变化可能与发育种子中ABA库大小的变化有关。
