Background and Aims Cold stress in rice (Oryza sativa) plants at the reproductive stage prevents normal anther development and causes pollen sterility. Tapetum hypertrophy in anthers has been associated with pollen sterility in response to cold at the booting stage. Here, we re-examined whether the relationships between anther abnormality and pollen sterility caused by cold stress at the booting stage in rice can be explained by a monovalent factor such as tapetum hypertrophy. Methods After exposing plants to a 4-d cold treatment at the booting stage, we collected and processed anthers for transverse sectioning immediately and at the flowering stage. We anatomically evaluated the effect of cold treatment on anther internal morphologies, pollen fertilities and pollen numbers in the 13 cultivars with various cold sensitivities. Key Results We observed four types of morphological anther abnormalities at each stage. Pollen sterility was positively correlated with the frequency of undeveloped locules, but not with tapetum hypertrophy as commonly believed. In cold-sensitive cultivars grown at low temperatures, pollen sterility was more frequent than anther morphological abnormalities, and some lines showed remarkably high pollen sterility without any anther morphological alterations. Most morphological anomalies occurred only in specific areas within large and small locules. Anther length tended to shorten in response to cold treatment and was positively correlated with pollen number. One cultivar showed a considerably reduced pollen number, but fertile pollen grains under cold stress. We propose three possible relationships to explain anther structure and pollen sterility and reduction due to cold stress. Conclusions The pollen sterility caused by cold stress at the booting stage was correlated with the frequency of entire locule-related abnormalities, which might represent a phenotypic consequence, but not a direct cause of pollen abortion. Multivalent factors might underlie the complicated relationships between anther abnormality and pollen sterility in rice.

中文翻译：

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冷胁迫对水稻孕穗期花药形态与花粉不育关系的修正

背景和目的水稻 (Oryza sativa) 植物在生殖阶段的冷胁迫会阻止正常的花药发育并导致花粉不育。花药中的绒毡层肥大与孕穗期花粉不育有关。在这里，我们重新研究了水稻孕穗期冷胁迫引起的花药异常与花粉不育之间的关系是否可以用绒毡层肥大等单价因素来解释。方法 在孕穗期对植物进行4 d冷处理后，立即和开花期采集花药进行横切。我们在解剖学上评估了冷处理对具有不同冷敏感性的 13 个品种的花药内部形态、花粉肥力和花粉数量的影响。主要结果 我们在每个阶段观察到四种形态的花药异常。花粉不育与未发育室的频率呈正相关，但与通常认为的绒毡层肥大无关。在低温生长的冷敏品种中，花粉不育比花药形态异常更常见，一些品系表现出非常高的花粉不育，而没有任何花药形态改变。大多数形态异常仅发生在大小房内的特定区域。冷处理时花药长度趋于缩短，并且与花粉数呈正相关。一个品种的花粉数量显着减少，但在冷胁迫下花粉粒可育。我们提出了三种可能的关系来解释花药结构和花粉不育以及冷胁迫引起的减少。结论孕穗期冷胁迫引起的花粉不育与整个室相关异常的发生频率相关，这可能是表型后果，但不是花粉败育的直接原因。多价因素可能是水稻花药异常与花粉不育之间复杂关系的基础。