There has been little research on crop lodging and yield determination in response to varying degrees of heat stress in canola. This research aimed to examine root morphology, pod fertility, seed yield and crop lodging of two canola genotypes subjected to normal temperature (23/17°C, light/dark, as CK), and three elevated temperature regimes imposed at flowering for a short term (10 days), namely CK+2 (25.0/22.0°C, light/dark), CK+4 (27.0/24.0°C) and CK+6 (29.0/26.0°C), in a controlled growth facility. Elevated temperature treatment, CK+4 and CK+6, displayed a significant adverse effect on seed yield and stem lodging. Compared to the CK, a significant yield loss of 35.6% and 48.7% in CK+4 and CK+6, respectively, was mainly due to poor pod fertility. This was evident from the smaller number of total filled pods (−21% in the CK+4 and −25% in the CK+6), low success ratio of pod developed (−25%, CK+4 and −29%, CK+6) and poor pollen viability (−36%, CK+4 and −50%, CK+6), averaged across both genotypes. Lateral root development was sensitive to the elevated temperature treatment, showing significant reductions in the lateral root morphology (8.0%–28.5%), while the taproot was relatively tolerant to the elevated temperature stress. A strong relationship between root electrical capacitance and lateral root morphology (R² > .74**) indicates that electrical measurements could be used as a non-destructive method for evaluating root parameters under elevated temperatures. Higher risk of stem lodging (21.4% lower stem safety factor) compared to the CK was evident under severe elevated temperature stress, as ascribed from the reduced stem bending strength that was caused by the deteriorating stem mechanical properties such as decreased flexural rigidity and weakened vascular bundle size (i.e. stunted fibre cell, and thinned size of fibre wall, deteriorated secondary xylem and smaller secondary phloem). These results were further verified by the principal component analysis and structural equation model. The root lodging risk was not influenced by the elevated temperature regime, primarily due to the unaffected anchorage strength and height of the centre of gravity. This information will be useful in improving lodging resistance and alleviating the related impact of heat stress in canola.

中文翻译：

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开花期不同程度短期热胁迫下双低油菜籽的倒伏、豆荚肥力和产量形成

关于油菜籽不同程度的热胁迫对作物倒伏和产量决定的研究很少。本研究旨在检测两种油菜基因型在常温（23/17°C，光/暗，如 CK）和短期开花时施加的三种高温条件下的根形态、豆荚肥力、种子产量和作物倒伏情况。期（10 天），即 CK+2（25.0/22.0°C，亮/暗）、CK+4（27.0/24.0°C）和 CK+6（29.0/26.0°C），在受控生长设施中。升高温度处理，CK+4 和CK+6，对种子产量和茎倒伏表现出显着的不利影响。与 CK 相比，CK+4 和 CK+6 的显着产量损失分别为 35.6% 和 48.7%，主要是由于豆荚肥力差。这从较小的总填充豆荚数量（CK+4 中的 -21% 和 CK+6 中的 -25%）、豆荚开发的低成功率（-25%、CK+4 和 -29%， CK+6）和差的花粉活力（-36%，CK+4 和-50%，CK+6），这两种基因型的平均值。侧根发育对高温处理敏感，侧根形态显着降低（8.0%~28.5%），而主根相对耐受高温胁迫。根电容与侧根形态之间有很强的关系（侧根形态显着减少（8.0%–28.5%），而主根相对耐受高温胁迫。根电容与侧根形态之间有很强的关系（侧根形态显着减少（8.0%–28.5%），而主根相对耐受高温胁迫。根电容与侧根形态之间有很强的关系（[R ² > .74**) 表明电测量可用作评估高温下牙根参数的非破坏性方法。与 CK 相比，在严重升高的温度应力下，明显的茎倒伏风险更高（茎安全系数降低 21.4%），这是由于茎机械性能恶化（例如弯曲刚度降低和血管减弱）导致茎弯曲强度降低。束大小（即纤维细胞发育不良，纤维壁变薄，次生木质部恶化，次生韧皮部变小）。这些结果通过主成分分析和结构方程模型进一步验证。根部倒伏风险不受高温状态的影响，主要是由于不受影响的锚固强度和重心高度。