Drought, as a major environmental factor that limits plant growth and photosynthesis, is a challenge for agriculture in the context of climate change. High temperatures and drought stress impact crops as a function of their stage of development and genotypic tolerance. Choosing adapted sunflower ( L.) varieties and management practices can mitigate impacts of water deficit on growth, physiology and productivity, but with complex genotype × environment interactions. Cover crops (CC), used mainly as catch crops and/or green manure, can release mineral nitrogen after destruction, which influences growth and development of the following crop. Here, we studied how nitrogen released by CC residues can influence water deficit responses of sunflower. In semi-controlled experiments, using the high-throughput phenotyping platform Heliaphen, we tested impacts of water deficit on vegetative and post-flowering stages of four sunflower varieties in pots, in which CC residues of rye ( L.) or vetch ( R.) had been incorporated before sowing. We studied impacts of water deficit during the vegetative stage on sunflower growth and transpiration and water deficit during the post-flowering stage on sunflower physiology and productivity. Under well-watered conditions, CC residues of vetch increased sunflower growth and productivity. Under water deficit conditions, CC residues mitigated the water-deficit response when applied during the vegetative stage, by limiting a decrease in growth, but they did not mitigate it post-flowering. Varieties responded differently to CC residues during vegetative and post-flowering stages. During seed development, severe water deficit cancelled out positive impacts of CC on productivity. Further research is needed to understand impacts of the intensity and period of water deficit on sunflower growth, physiology and yield following CC.

中文翻译：

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覆盖作物残留物可以减轻向日葵在营养生长过程中因品种差异而造成的水分亏缺的影响，但不能减轻种子发育过程中的影响

干旱作为限制植物生长和光合作用的主要环境因素，是气候变化背景下农业面临的挑战。高温和干旱胁迫对作物的影响取决于其发育阶段和基因型耐受性。选择适应的向日葵 (L.) 品种和管理实践可以减轻水分亏缺对生长、生理和生产力的影响，但具有复杂的基因型与环境相互作用。覆盖作物（CC）主要用作农作物和/或绿肥，破坏后可释放矿质氮，影响后续作物的生长和发育。在这里，我们研究了 CC 残留物释放的氮如何影响向日葵的水分亏缺反应。在半对照实验中，我们使用高通量表型分析平台Heliaphen，测试了水分亏缺对盆栽四个向日葵品种的营养和花后阶段的影响，其中黑麦（L.）或野豌豆（R. ）已在播种前合并。我们研究了营养阶段水分亏缺对向日葵生长和蒸腾作用的影响以及花后阶段水分亏缺对向日葵生理和生产力的影响。在浇水良好的条件下，野豌豆的 CC 残留物可促进向日葵的生长和生产力。在缺水条件下，CC残留物在营养阶段施用时可以通过限制生长下降来缓解缺水反应，但它们并不能缓解开花后的缺水反应。不同品种在营养阶段和花后阶段对 CC 残留物的反应不同。在种子发育过程中，严重的缺水抵消了 CC 对生产力的积极影响。需要进一步的研究来了解缺水的强度和持续时间对 CC 后向日葵生长、生理和产量的影响。