热害胁迫条件下水稻花药发育异常的早期特征

田间条件下持续高温(而非短期高温)是导致水稻生殖生长期高温危害的重要条件,由此推测水稻花粉母细胞减数分裂至抽穗的一段期间,可能均为水稻的高温敏感期,且高温诱导可能具有累积效应。本研究模拟田间典型灾害天气条件,在人工气候箱内对杂交水稻"金优63"花粉母细胞减数分裂期进行连续3d的热害胁迫处理,对处理后不同发育时期的花药组织取样切片观察,从组织、细胞水平探讨水稻受高温胁迫后花药可能出现的早期异常特征。结果表明,受高温胁迫后,在小孢子形成阶段,水稻花粉母细胞发育异常、四分体无法适时分散;在花粉粒成熟阶段,水稻生殖细胞失去正确的排列方向、绒毡层细胞发生非正常分解、花药壁和花粉粒发生形态异常并出现败育。此外,植株减数分裂期受高温胁迫后,开花时花粉活力显著降低。这些结果表明,抽穗前的高温直接导致水稻花药组织和生殖细胞异常发育,从而减少有效花粉的形成和降低裂药与授粉性能,可能成为田间条件下持续高温引起水稻不育的重要原因。

Early signs of heat stress-induced abnormal development of anther in rice

A continuous high temperature (other than short-term rise in temperature) leads to heat stress in rice at the reproductive growth stage under field conditions. Hence rice can be sensitive to heat stress from meiocyte meiosis to anthesis stage, and not just at anthesis. Rice is likely to respond to heat stress in a cumulative way. Under imitated daily field microclimatic conditions for heat stress, the rice cultivar "Jinyou63" (which is a hybrid rice combination) was treated with a consecutive 3-day heat stress during meiosis in phytotron. Anther and pollen tissues at different development stages after subjected to heat stress were sampled and analyzed for transverse abnormalities. The analysis shows that under heat stress, meiocytes degenerate while tetrad cell dispersion fails at microspore formation phase. During pollen maturation phase, loss of orientation of reproductive cells, abnormal vacuolization of tapetal cells, paramorphia or abortion of anther walls and pollens are observed under heat stress. In addition, pollen activity at anthe-sis decreases significantly under heat stress during meiosis stage. The findings suggest that abnormalities in anther tissues and repro-ductive cells are caused by heat stress before heading. This decreases yield potential of active pollens and destroys dehiscence and pollination, which could be the primary cause of rice sterility under continuously high temperature field conditions.