Abstract Low temperature greatly affects wheat production, while low-temperature pretreatments may enhance plant tolerance to subsequent low-temperature stress. However, the knowledge on grain yield formation responses to multiple low-temperature stresses under natural conditions is still limited. Here, two years of environment-controlled phytotron experiments were carried out with two wheat cultivars under different low-temperature levels, periods and frequencies, and the temperature regimes in this study were designed to be similar to the daily variation in natural temperature. Spring frost (canopy temperature fall below 0 °C or Stevenson screen air temperatures below 2 °C) had negative effects on grain yield and yield components for both cultivars. Moreover, wheat yield was more sensitive to low temperatures at booting than at jointing. The reduction in grain yield under low-temperature conditions was mainly attributed to the decreased spike number per plant (SNPP) and grain number per spike (GNPS). Furthermore, grains in the apical spikelets were the most sensitive to spring frost, followed by those in the basal and central spikelets. Compared to the non-low-temperature-pretreated plants, the low-temperature-pretreated plants did not have an increased grain yield, except at T4 (Tmin/Tmax/Tmean, −6 °C/4 °C/−1 °C). Grain yield under T4 probably increased because severe low temperatures killed parts of the tillers, which resulted in carbon and nitrogen relocation to the roots, young tillers and axillary buds. As a result, the young and new tillers in the axillary buds grew rapidly and eventually formed spikes.

中文翻译：

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拔节和孕穗低温胁迫对小麦产量的个体效应和联合效应

摘要 低温对小麦产量影响很大，而低温预处理可增强植物对后续低温胁迫的耐受性。然而，关于自然条件下多种低温胁迫下谷物产量形成响应的知识仍然有限。在这里，在不同的低温水平、时期和频率下对两个小麦品种进行了两年的环境控制植物加速器实验，本研究中的温度制度设计为与自然温度的日变化相似。春季霜冻（冠层温度低于 0 °C 或史蒂文森筛网气温低于 2 °C）对两个品种的谷物产量和产量构成都有负面影响。此外，小麦产量对孕穗期的低温比拔节期更敏感。低温条件下谷物产量的降低主要归因于每株穗数（SNPP）和每穗粒数（GNPS）的减少。此外，顶端小穗的籽粒对春季霜冻最敏感，其次是基部和中央小穗的籽粒。与非低温预处理的植物相比，低温预处理的植物没有增加谷物产量，除了在 T4 (Tmin/Tmax/Tmean, -6 °C/4 °C/-1 °C ）。T4 条件下的谷物产量可能增加，因为严重的低温杀死了部分分蘖，导致碳和氮重新定位到根、幼分蘖和腋芽。结果，腋芽中的年轻和新分蘖迅速生长并最终形成穗状花序。