摘 要：本试验以两种不同低温耐性的水稻品种：南粳 46（低温敏感型）和淮稻 5 号（耐冷型）作 为材料，利用人工气候室设置 4 个温度水平：Tmax/Tmin 分别为 27℃/21℃(T1)，23℃/17℃(T2)，19℃/13℃(T3)和 15℃/9℃(T4)， 3 个持续时间： 3d(D1)、6d(D2)、9d(D3)。研究了开花期和灌浆期低温 胁迫对水稻叶片光合参数和叶绿素含量等方面的影响。研究结果表明：在低温胁迫处理期间水稻剑叶初始光能利用率和净光合速率都有一定程度的下降，且耐冷品种淮稻 5 号下降幅度较小；随着低 温处理水平的降低和持续时间的延长，两品种光合参数下降幅度明显增加，其中开花期低温胁迫对光合参数影响较灌浆期低温胁迫更为明显。处理结束后，剑叶净光合速率均能恢复到正常水平，且耐冷品种有着更快的恢复速度。随着生育期推进，低温胁迫处理后剑叶净光合速率下降速度明显慢 于正常处理，可能是有由于低温造成了叶片生育期推迟，最后表现为 T4>T3>T2>T1。叶绿素的变化 有着和净光合速率类似的变化趋势，耐冷品种淮稻 5 号在处理结束后 T4 和 T3 较 T1 和 T2 叶绿素含 量下降幅度更缓慢。南粳 46 由于对低温敏感而叶绿素总量表现为 T4 的温度下可能造成了光合结构 损伤，而表现为规律性并不明显且 T4 值较低。研究结果对明确低温胁迫对水稻光合生产的影响具有 重要意义，为定量模拟未来气候条件下不同情景低温胁迫对水稻干物质生产和产量形成奠定了基础。 

关键词：低温胁迫；水稻；剑叶；初始光能利用率；净光合速率；叶绿素含量； 

Effects of Low Temperature Stress on Leaf Photosynthesis during Flowering and Filling Stages in Rice

Abstract：In this study, one-year cold stress experiment with four temperature levels (Tmax\/Tmin 27℃/21℃(T1), 23℃/17℃(T2), 19℃/13℃ (T3) and 15℃/9℃ (T4)) and 3 durations (3d (D1), 6d (D2), and 9d (D3) was conducted in artificial climate chamber in two rice cultivars with different low temperature tolerance (Nanjing46 (Cold sensitive type) and Huaidao5 (Cold resistant type)). The effects of cold stress during flowering and grain filling period on photosynthetic parameters in flag leaf and chlorophyll content were studied. The results show that the initial light use efficiency and net photosynthetic rate of rice flag leaf decreased with the increase of low temperature level and duration during cold stress treatment period, and the decrease of Huaidao5 was smaller, compared with Nanjing46. Photosynthetic parameters during stress treatment in both cultivars were more sensitive to cold stress at flowering than at grain filling. After cold stress treatment, net photosynthetic rate in flag leaf in cold stress treatments can recover to same level with check treatments, and the recovery speed was faster in Huaidao5. With the senescence of rice leaves, the decrease rates of flag leaf net photosynthetic rate were smaller in cold stress treatments than in check treatments, as a delayed senescence due to cold stress. And the net photosynthetic rate was: T4>T3>T2>T1 at maturity. The changes of chlorophyll content has a similar trend with net photosynthetic rate after cold stress. After the treatment, chlorophyll content in T4 and T3 of Huaidao5 decreased more slowly than T1 and T2. But in Nanjing46, due to the high sensitivity to low temperature, it may cause irreversible damage to the photosynthetic structural damage at T4 .so the regularity of chlorophyll content not obvious and the T4 value was low. Our results was important for dissecting the effects of cold stress on rice leaf photosynthesis, and will lay a foundation for simulating the impacts of cold stress on rice biomass production and yield formation in future climate scenarios.

Key words: Cold stress; Rice; Flag leaf; Initial light use efficiency; Net photosynthetic rate; Chlorophyll content;