Cultivation of sunflower (Helianthus annuus L.) as one of the most important oil crops is of great importance, especially with focus on drought tolerance under the current climate change. Less precipitation and increasing temperatures lead to more regions with drought problems. In a container experiment, with two different sunflower cultivars, drought stress of 40% water‐holding capacity was applied at the seed‐filling phase and compared to a control group with regular irrigation to 70% water‐holding capacity. Four intermediate harvests during the seed‐filling phase and a final harvest at maturity were conducted. During the seed‐filling phase, sugar and α‐amino‐acid concentrations of seeds were not reduced by drought stress. Thus, assimilate availability was sufficient, pointing to no source limitation of seed development. The DNA content of the seeds was also not affected and pointed to no limitation of cell division. However, 40 days after flowering a reduction of cell extension was found. Consequently, a sink limitation occurred under drought stress. At final harvest, seed yield was significantly reduced under drought stress due to a lower single seed weight, whereas seed number per plant was unaffected. Oil concentration was not reduced by drought stress. Thus, oil synthesis did not limit oil yield. Consequently, a reduced oil yield under drought stress during the seed‐filling phase was caused by a lower seed weight, which resulted from a decreased cell extension.

中文翻译：

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向日葵的干旱胁迫由于减少的细胞延伸生长而导致种子填充受抑制

向日葵（向日葵）的栽培L.）作为最重要的油料作物之一，具有非常重要的意义，特别是在当前气候变化下着重于耐旱性。降水减少和温度升高导致更多地区出现干旱问题。在一个容器试验中，使用两个不同的向日葵品种，在灌浆期施加了40％持水量的干旱胁迫，并与定期灌溉至70％持水量的对照组进行了比较。在种子灌装阶段进行了四次中间收获，在成熟期进行了最后一次收获。在种子灌浆阶段，干旱胁迫并未降低种子中糖和α-氨基酸的含量。因此，同化物的可用性就足够了，表明种子发育没有来源限制。种子的DNA含量也没有受到影响，并指出没有细胞分裂的限制。然而，开花后40天发现细胞延伸减少。因此，在干旱胁迫下发生了下陷限制。在最终收成时，由于单种子重量降低，干旱胁迫下种子产量明显降低，而单株种子数量不受影响。干旱胁迫并没有降低油的浓度。因此，油的合成不限制油的产率。因此，在种子灌浆期干旱胁迫下，油的产量降低是由于种子重量降低，这是由于细胞伸长减少所致。由于较低的单粒重，干旱胁迫下种子产量显着降低，而单株种子数不受影响。干旱胁迫并没有降低油的浓度。因此，油的合成不限制油的产率。因此，在种子灌浆期干旱胁迫下，油的产量降低是由于种子重量降低，这是由于细胞伸长减少所致。由于较低的单粒重，干旱胁迫下种子产量显着降低，而单株种子数不受影响。干旱胁迫并没有降低油的浓度。因此，油的合成不限制油的产率。因此，在种子灌浆期干旱胁迫下，油的产量降低是由于种子重量降低，这是由于细胞伸长减少所致。