Abstract Future increases in yield potential will rely largely on improved photosynthesis. Whereas emphasis has traditionally been given to measuring leaf photosynthesis, wheat spikes have an important role in filling grains since they can intercept up to a third of incident light. In the present study, 196 genetically diverse spring wheat lines were evaluated for spike photosynthesis (SP) under temperate (yield potential) and heat stressed, irrigated conditions. Two different methods to estimate SP were used: (i) gas exchange measurements of SP rate and (ii) integrative measurements using a SP inhibition treatment (consisting of a permeable textile covering the spikes). Rate of SP was measured directly in 45 selected genotypes under yield potential conditions using a custom-made illuminating chamber. In these lines, a variation of 2.8-fold for spike photosynthetic rate is reported for the first time with good heritability estimates. Correlations between SP rate and yield, thousand grain weight, number of grains per spike and radiation use efficiency are reported across different panels. Genotypic variation in SP was independent from flag leaf photosynthesis suggesting that any strategy aiming to increase canopy photosynthesis should also consider SP. The SP inhibition treatments were applied on the 196 lines in both environments to estimate SP contribution to grain weight per spike, which was 30–40 % under both heat stressed and yield potential conditions averaged across lines. Positive correlations with grain yield were observed for spike photosynthesis contribution across all of the panels under heat stress and when combining heat and yield potential environments (P

中文翻译：

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以高通量测量的穗光合作用表明遗传变异与旗叶光合作用无关

摘要 未来产量潜力的增加将在很大程度上依赖于光合作用的改进。传统上强调测量叶片光合作用，而小麦穗在填充谷物方面具有重要作用，因为它们可以拦截多达三分之一的入射光。在本研究中，对 196 个遗传多样性春小麦品系在温带（产量潜力）和热胁迫、灌溉条件下的穗光合作用 (SP) 进行了评估。使用两种不同的方法来估计 SP：（i）SP 速率的气体交换测量和（ii）使用 SP 抑制处理（由覆盖尖峰的可渗透纺织品组成）的综合测量。使用定制的照明室在产量潜力条件下直接测量 45 个选定基因型的 SP 率。在这些行中，变体为 2。首次报道了峰值光合速率的 8 倍，并具有良好的遗传力估计。SP 率与产量、千粒重、每穗粒数和辐射利用效率之间的相关性报告在不同的面板上。SP 的基因型变异与旗叶光合作用无关，这表明任何旨在增加冠层光合作用的策略也应考虑 SP。SP 抑制处理应用于两种环境中的 196 个品系，以估计 SP 对每个穗粒重的贡献，在热胁迫和产量潜力条件下平均为跨品系的 30-40%。在热应激下以及结合热和产量潜在环境时，观察到所有面板的穗状光合作用贡献与谷物产量呈正相关（P