The influence of drought stress on barley (Hordeum vulgare) has been investigated. The experiments were conducted with seedlings of barley—by the application of combined drought and temperature stresses. Here we showed that combination of drought and high temperature inflicted more severe damage to plants than the drought and low temperature stress. The temperature stress triggered more drastic changes in plant morphology/physiology and biochemistry than the drought stress. Interestingly, plants exposed to high temperature exhibited significant reduction of shoot and root aldehyde oxidase (AO) activity. Moreover, increased temperature resulted in lower levels of reactive oxygen species (ROS), while drought stress had an opposite effect on ROS accumulation and AO activity. This is the first demonstration of inhibition of plant AO and ROS in response to heat stress. The combined heat and drought stresses resulted in increased activity of catalase (CAT) and superoxide dismutase (SOD) in roots but not in shoots. Our findings indicate that heat and drought stresses may induce activation of different antioxidant enzymatic defense mechanisms and heat stress significantly affects enzymes responsible for the ROS accumulation in plants.

干旱胁迫对大麦的影响（大麦) 进行了调查。实验是在大麦幼苗上进行的——通过应用干旱和温度胁迫。在这里，我们表明干旱和高温的结合比干旱和低温胁迫对植物造成了更严重的损害。与干旱胁迫相比，温度胁迫在植物形态/生理和生物化学方面引发了更剧烈的变化。有趣的是，暴露于高温的植物表现出地上部和根部醛氧化酶 (AO) 活性的显着降低。此外，温度升高导致活性氧 (ROS) 水平降低，而干旱胁迫对 ROS 积累和 AO 活性有相反的影响。这是第一次证明植物 AO 和 ROS 响应热应激而受到抑制。热和干旱的联合胁迫导致根中过氧化氢酶 (CAT) 和超氧化物歧化酶 (SOD) 的活性增加，但在芽中没​​有。我们的研究结果表明，热和干旱胁迫可能会诱导不同抗氧化酶防御机制的激活，热胁迫显着影响负责植物 ROS 积累的酶。