Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou University, Yangzhou, Jiangsu, China.
J Exp Bot. 2010 Aug;61(13):3719-33. doi: 10.1093/jxb/erq198. Epub 2010 Jun 28.
Cytokinins may reflect soil water status and regulate rice (Oryza sativa L.) grain filling. This study investigated the changes in cytokinin levels in rice plants and their relations with grain filling under alternate wetting and drying irrigation. Two 'super' rice cultivars were field grown. Three irrigation regimes, alternate wetting and moderate soil drying (WMD), alternate wetting and severe soil drying (WSD), and conventional irrigation (CI, continuously flooded), were imposed after flowering. No significant differences in grain-filling rate, grain weight, and cytokinin content were observed for the earlier-flowering superior spikelets among the three irrigation regimes. For the later-flowering inferior spikelets, however, their grain-filling rate and grain weight were significantly increased in the WMD and significantly reduced in the WSD when compared with those in the CI. Cytokinin contents in shoots (inferior spikelets and the flag leaves) in the WMD at the soil drying time were comparable with those in the CI, but they were significantly increased when plants were rewatered. The WSD significantly reduced cytokinin contents in the shoot either during soil drying or during the rewatering period. Cytokinin contents in roots showed no significant difference between the WMD and CI regimes. The WSD increased trans-zeatin-type cytokinins, whereas it reduced isopentenyladenine-type cytokinins, in roots. Grain-filling rate and grain weight of inferior spikelets were very significantly correlated with cytokinin contents in these spikelets. The results suggest that a post-anthesis WMD holds great promise to improve grain filling of inferior spikelets through elevating cytokinin levels in the rice shoot.
细胞分裂素可能反映土壤水分状况并调节水稻（Oryza sativa L.）灌浆。本研究在淹水和干湿交替灌溉条件下，调查了水稻植株中细胞分裂素水平的变化及其与灌浆的关系。在田间种植了两个“超级”水稻品种。在开花后，分别采用三种灌溉制度，交替湿润和适度土壤干燥（WMD）、交替湿润和严重土壤干燥（WSD）和常规灌溉（CI，持续淹水）。在三种灌溉制度中，WMD 和 WSD 对早期开花的优势小穗的灌浆速率、粒重和细胞分裂素含量没有显著差异。然而，对于晚期开花的弱势小穗，WMD 和 WSD 可显著提高其灌浆速率和粒重，而与 CI 相比，其灌浆速率和粒重显著降低。在土壤干燥时，WMD 下的茎叶（弱势小穗和旗叶）中的细胞分裂素含量与 CI 相当，但当植物重新浇水时，其含量显著增加。WSD 无论在土壤干燥期还是在重新浇水期都显著降低了茎叶中的细胞分裂素含量。WMD 与 CI 之间，根中的细胞分裂素含量没有显著差异。WSD 增加了根中的玉米素型细胞分裂素，而降低了异戊烯基腺嘌呤型细胞分裂素。弱势小穗的灌浆速率和粒重与这些小穗中的细胞分裂素含量呈极显著正相关。结果表明，在开花后进行 WMD 处理可以通过提高水稻地上部细胞分裂素水平来提高弱势小穗的灌浆。
