There is limited knowledge about the effects of the severity and timing of drought stress on oat (Avena sativa) yield and the critical stages at which water management could be effectively implemented. A controlled study was conducted to identify a variety-specific critical stage, and to examine the physiological mechanisms of drought stress on photosynthesis (Pn) and yield formation in two contrasting genotypes. We found that compared with sufficient water supply (AW), grain yield was reduced by 36%, 69% and 44% in ‘Shadow’, and by 31%, 33% and 41% in ‘Bia’ under the severe stress imposed either at jointing, heading or post-anthesis stage. The grain/leaf area (LA) ratio increased by 18–32% and biomass distribution to stems + leaves decreased by 5.2–6.2% of Bia under moderate stress (MS) as compared to AW. This, along with the improved harvest index, led to a comparable yield. Under AW, Shadow displayed 13–16% larger LA duration (LAD) and had significantly higher Pn at the heading and post-anthesis stages, leading to 13% to 20% more spikelets panicle−1 and 13–21% greater groat yields than Bia. It can be concluded that (1) water stress at heading for Shadow and at post-anthesis for Bia was detrimental to grain yield through reduced LA and LAD with a reduced sink size, (2) under the MS, greater grain yield of the hulled Bia was attributable to a stronger sink activity, and (3) higher groat yield of the naked Shadow under AW was associated mainly with a higher source activity and more spikelets panicle−1.

中文翻译：

---

源库调整：干旱胁迫对两种对比燕麦 (Avena sativa L.) 基因型光合作用和谷物产量的时间和严重程度的机制理解

关于干旱胁迫的严重程度和时间对燕麦（Avena sativa）产量的影响以及可以有效实施水资源管理的关键阶段的知识有限。进行了一项对照研究，以确定品种特定的关键阶段，并检查干旱胁迫对光合作用 (Pn) 和两种对比基因型产量形成的生理机制。我们发现，与充足的供水（AW）相比，'Shadow' 的谷物产量分别降低了 36%、69% 和 44%，'Bia' 的谷物产量分别在在拔节、抽穗或花后阶段。与 AW 相比，在中等压力 (MS) 下，Bia 的籽粒/叶面积 (LA) 比增加了 18-32%，茎 + 叶的生物量分布减少了 5.2-6.2%。这，随着收获指数的提高，产量相当。在 AW 下，Shadow 的 LA 持续时间 (LAD) 增加了 13-16%，并且在抽穗期和开花后阶段具有显着更高的 Pn，导致小穗圆锥花序-1 多 13% 到 20%，单粒产量比 13-21%比亚。可以得出的结论是：（1）在朝向阴影和开花后的 Bia 水分胁迫通过减少 LA 和 LAD 以及减小的汇尺寸对谷物产量有害，（2）在 MS 下，带壳的谷物产量增加Bia 归因于更强的汇活动，并且 (3) AW 下裸影的较高单粒产量主要与更高的源活动和更多的小穗圆锥花序-1 相关。与 Bia 相比，Shadow 显示的 LA 持续时间 (LAD) 长 13-16%，并且在抽穗和开花后阶段具有显着更高的 Pn，导致小穗圆锥花序-1 多 13% 到 20%，单粒产量高 13-21%。可以得出结论：（1）在阴影抽穗和 Bia 开花后的水分胁迫通过减少 LA 和 LAD 以及减小的水槽尺寸对谷物产量有害，（2）在 MS 下，带壳的谷物产量增加Bia 归因于更强的汇活动，并且 (3) AW 下裸影的较高单粒产量主要与更高的源活动和更多的小穗圆锥花序-1 相关。与 Bia 相比，Shadow 显示的 LA 持续时间 (LAD) 长 13-16%，并且在抽穗和开花后阶段具有显着更高的 Pn，导致小穗圆锥花序-1 多 13% 到 20%，单粒产量高 13-21%。可以得出的结论是：（1）在朝向阴影和开花后的 Bia 水分胁迫通过减少 LA 和 LAD 以及减小的汇尺寸对谷物产量有害，（2）在 MS 下，带壳的谷物产量增加Bia 归因于更强的汇活动，并且 (3) AW 下裸影的较高单粒产量主要与更高的源活动和更多的小穗圆锥花序-1 相关。