Intensity and frequency of heat waves (HW) accompanied by drought are increasing, however, still little is known about its effect on forage plants. A pot experiment was carried out in growth chambers in order to elucidate the multiple response of forage rape to combined HW and drought (HD) under current and elevated CO₂ (HD + CO₂). Forage rape was proved to be relatively HD-resistant plant, with no significant and long-term effects on shoot growth and photosynthetic performance, and effective stimulation of antioxidative system, especially in the case of HD + CO₂ exposure. Activities of enzymes of ascorbate–glutathione cycle were further stimulated by elevated CO₂ even after the termination of HD treatment. Nutritive value of forage rape was also positively affected, as was shown by elevated content of water-soluble carbohydrates after exposure and starch after the period of recovery (up to 80% and 92%, respectively). Concentrations of most macro- and microelements were increased, and stabilized higher or equalized to control level after the period of recovery in a similar pattern for HD and HD + CO₂ exposure. However, content of Ca was reduced and remained significantly lower (~20%). One of the most important negative and lagged HD effects was reduction of dry root biomass (~30%), most possibly induced by accumulation of non-structural carbohydrates in shoot and was not mitigated by elevated CO₂. To conclude, forage rape was proved to be a promising forage crop for the future climate with increased frequency of HWs; however, a special attention should be paid to the lagged effects, such as inhibition of root growth.

中文翻译：

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草料油菜在当前和二氧化碳升高的情况下对热浪和干旱的多方面响应

伴随干旱的热浪 (HW) 的强度和频率正在增加，然而，对其对牧草植物的影响仍然知之甚少。在生长室中进行盆栽试验以阐明草料油菜在当前和升高的 CO ₂ (HD + CO ₂ )下对 HW 和干旱 (HD) 组合的多重响应。牧草油菜被证明是相对抗HD的植物，对枝条生长和光合性能没有显着和长期的影响，并且有效地刺激了抗氧化系统，特别是在HD + CO ₂暴露的情况下。升高的 CO ₂进一步刺激了抗坏血酸-谷胱甘肽循环酶的活性即使在 HD 治疗终止后。草料油菜的营养价值也受到积极影响，如暴露后水溶性碳水化合物和恢复期后淀粉含量升高（分别高达 80% 和 92%）表明。大多数宏量和微量元素的浓度增加，并在恢复期后以类似的模式在 HD 和 HD + CO ₂暴露中稳定在更高或等于对照水平。然而，Ca 含量降低并保持显着较低（~20%）。最重要的负面和滞后 HD 效应之一是干根生物量减少（~30%），这很可能是由地上部非结构性碳水化合物的积累引起的，并且不会因 CO ₂升高而减轻. 总而言之，随着 HW 频率的增加，草料油菜被证明是一种有前途的未来气候的草料作物；但是，应特别注意滞后效应，例如抑制根系生长。