Two rice genotypes Huanghuazhan (HHZ, heat-resistant) and IR36 (heat-susceptible) were subjected to high-temperature (HT, 40 °C) and normal-temperature (NT, 32 °C) treatments at the spikelet differentiation stage. HT treatment inhibited spikelet differentiation, aggravated spikelet degeneration, reduced spikelet size, and disordered carbohydrate allocation. Meanwhile, HT treatment increased nonstructural carbohydrate content in leaves, but decreased that in stems and young panicles, and the same tendencies of sucrose and starch contents were observed in leaves and stem. However, HT treatment significantly increased the sucrose content and sharply decreased the glucose and fructose contents in young panicles. Lower activity levels of soluble acid invertase (EC3.2.1.26) and sucrose synthase (EC2.4.1.13) were observed under HT treatment. Moreover, HT treatment reduced the activities of key enzymes associated with glycolysis and the tricarboxylic acid cycle, which indicated sucrose consumption was inhibited in young panicles under HT treatment. Exogenous glucose and fructose applied under HT treatment increased the spikelet number more than exogenous sucrose. In conclusion, the results demonstrated that the reduction of spikelet number under high temperature was more affected by the decrease in sugar consumption than the blocking of sucrose transport. The impairment of sucrose hydrolysis was the main reason for the inhibition of sugar utilization.

在小穗分化阶段，对两种基因型黄花病（HHZ，耐热）和IR36（热敏感）基因型进行了高温（HT，40°C）和常温（NT，32°C）处理。HT处理抑制了小穗分化，加剧了小穗变性，减小了小穗大小和碳水化合物分配紊乱。同时，HT处理增加了叶片中非结构性碳水化合物的含量，但降低了茎和幼穗中的非结构性碳水化合物含量，并且在叶片和茎中观察到了相同的蔗糖和淀粉含量趋势。然而，HT处理显着增加了幼穗中蔗糖的含量，并急剧降低了葡萄糖和果糖的含量。在HT处理下观察到较低的可溶性酸转化酶（EC3.2.1.26）和蔗糖合酶（EC2.4.1.13）活性水平。此外，HT处理降低了与糖酵解和三羧酸循环相关的关键酶的活性，这表明在HT处理下幼穗中的蔗糖消耗受到抑制。在高温处理下施用的外源葡萄糖和果糖比外源蔗糖增加小穗数更多。总之，结果表明，糖分消耗的减少比阻止蔗糖运输受到的影响更大。蔗糖水解的损害是抑制糖利用的主要原因。在高温处理下施用的外源葡萄糖和果糖比外源蔗糖增加小穗数更多。总之，结果表明，糖分消耗的减少比阻止蔗糖运输受到的影响更大。蔗糖水解的损害是抑制糖利用的主要原因。在高温处理下施用的外源葡萄糖和果糖比外源蔗糖增加小穗数更多。总之，结果表明，糖分消耗的减少比阻止蔗糖运输受到的影响更大。蔗糖水解的损害是抑制糖利用的主要原因。