Grain-filling, as the final growth stage of rice, is sensitive to environmental temperature change. Previous studies mainly concerned about the effects of high temperature stress during grain-filling on rice growth, and most experiments were carried out with pot for cultivating rice and greenhouse for warming. This research investigated the response of rice grain-filling of superior spikelets (SS) and inferior spikelets (IS) of two japonica cultivars to elevated temperature during grain-filling stage under open-field warming conditions in lower reaches of Yangtze River Basin using free-air temperature enhancement facility. Results indicated that rice yield was not significantly changed by warming less than 4°C. SS and IS showed different responses to elevated temperature during the grain-filling stage, whereas there were similar trends between two cultivars and years. For SS, although elevated temperature enhanced its filling rate during the early grain-filling period, and caused a shorter grain-filling period and a lighter grain weight; for IS, elevated temperature improved its grain weight by enhancing its filling rate during middle and late grain-filling period due to the increased number of days with suitable temperature. For both SS and IS, key starch biosynthesis enzymes and indole-3-acetic acid content exhibited generally a similar dynamics trend with grain-filling rates, and these sink strength parameters presented higher levels under elevated temperature relative to natural temperature for IS during middle and late grain-filling period. Consequently, warming less than 4°C presented different influences on SS and IS; the improvement of IS filling under warming regime was associated with the intensification of grain sink strength.

中文翻译：

---

长江下游低幅度增温下粳稻优小穗灌浆研究

灌浆作为水稻的最后生长阶段，对环境温度变化敏感。以往的研究主要关注灌浆期高温胁迫对水稻生长的影响，大部分试验都是用盆栽水稻和温室增温进行的。【摘要】：本研究采用自由-热法研究了长江下游露地增温条件下2个粳稻品种上穗(SS)和劣穗(IS)灌浆对灌浆期温度升高的响应。空气温度增强设施。结果表明，升温低于4°C，水稻产量没有显着变化。SS和IS在灌浆期对升高的温度表现出不同的响应，而两个品种和年份之间也有相似的趋势。对SS而言，虽然高温提高了其灌浆前期的灌浆率，但导致灌浆期变短，粒重变轻；对于IS，由于适宜温度的天数增加，温度升高通过提高其灌浆中后期的灌浆率来改善其粒重。对于 SS 和 IS，关键淀粉生物合成酶和吲哚-3-乙酸含量与灌浆率总体表现出相似的动态趋势，并且这些库强度参数在升高的温度下相对于自然温度在中、灌浆后期。因此，升温低于 4°C 对 SS 和 IS 有不同的影响；