Crop growth limitation set by low water temperature stress in rice

灌溉水温过低会影响水稻(Oryza salva L.)通过限制各种不同的过程来实现增长，这与增长阶段不同，但综合理解仍然有限。在田间条件下，研究了三个生育期内低水温对水稻生长发育和产量的影响。冷水处理在营养生长期、生殖生长期和灌浆期进行，在16~25ﾟC温度范围内，冷水对生殖生长期籽粒产量的影响最大，在19ﾟ℃时，不同品种间的产量相差5倍以上，但对作物生长速率的损害最小。小穗育性的品种差异与CGR、光合作用速率和花药长度无关。穗形成期和孕穗期的根系修剪也不会改变小穗密度。对CGR影响最大的是营养生长期。在叶面积和辐射截获显著减少的同时，辐射利用效率相对不受影响。叶片展开能力强的品种在凉水温度下表现出较高的CGR。在整个处理期间，对光合作用速率的影响相对较小(5-15%)，但在营养生长期和生殖生长期处理期间，对水温的响应变化很大，前半部分下降较大，后半部分恢复。这些变化在很大程度上是由于气孔导度对水温的响应，可能是通过植物水分状况的变化。冷水还通过限制单位生物量氮素积累和单位氮素增加叶面积产量来减少作物氮素积累，但由于水温较低，后者在降低CGR方面具有相对重要的作用。

Low temperature of irrigation water can affect rice (Oryza saliva L.) growth by limiting various processes, which differ with the growth stages, but a synthetic understanding is still limited. The objective of this study was to determine the effect of low water temperature on growth, development and yield during three growth periods under field conditions. The treatment was conducted during the vegetative, the reproductive and grain-filling periods, In the temperatures range from 16 to 25ﾟC, cool water decreased grain yield most severely during the reproductive period by limiting spikelet fertility with a more than five-fold difference between cultivars at 19ﾟC, but the crop growth rate (CGR) was least damaged. The varietal difference in spikelet fertility was not associated with CGR, photosynthetic rates, and anther length. Root pruning at panicle formation and at booting also did not alter spikelet density. The largest influence on CGR occurred in the vegetative period. While leaf area and radiation interception were markedly reduced, radiation use efficiency was relatively unaffected. A cultivar with high ability of leaf expansion showed higher CGR under cool water temperatures. The effect on the photosynthetic rates was relatively small (5-15 %) when averaged over the treatment period, but the response to the water temperature changed substantially during the treatment for the vegetative and the reproductive growth periods, with a large reduction in the first half and the recovery in the second half. These changes were largely attributable to the response of the stomatal conductance to the water temperature, possibly via changes in the water status of the plants. Cool water also reduced crop N accumulation by limiting both N accumulation per unit biomass increase and leaf area production per unit N increase, but the latter had the comparative importance in CGR reduction due to low water temperatures.