Drought and salinity are two common abiotic stresses that restrain plant growth and often co-occur, either simultaneously or sequentially. However, the effect of drought on physiological responses of plants to salinity remains unclear. Accordingly, we selected three forage species that differ in drought and salinity tolerance: ryegrass (Lolium perenne L.), alfalfa (Medicago sativa L.) and switchgrass (Panicum virgatum L.). Independent and combined (sequential and simultaneous pattern) drought and salinity were carried out in a pot experiment. Salinity severely injured the plants through decreasing leaf water content and increasing Na⁺ and Cl⁻ concentrations. Compared to the individual salinity treatment, the sequential drought and salinity treatment remarkably enhanced the leaf water status and decreased toxic ion uptake, thereby decreasing levels of reactive oxygen species (ROS), malondialdehyde, and membrane leakage. In contrast, the oxidative damage that resulted from the simultaneous stress treatment was more pronounced than that produced by the independent salinity treatment, which can be attributed to decreased water content, increased toxic ion intake, or/and reduced antioxidant activity. Our results suggested that the physiological responses to combined drought and salinity remarkably depends on the temporal pattern of those stresses.

干旱和盐碱化是两种常见的非生物胁迫，它们会限制植物的生长，并且经常同时或相继出现。然而，干旱对植物对盐分生理反应的影响尚不清楚。因此，我们选择了三种在干旱和盐度耐受性上不同的草料：黑麦草（黑麦草），苜蓿（紫花苜蓿）和柳枝switch（Panicum virgatum L.）。在盆栽试验中进行了独立和组合（顺序和同时进行）的干旱和盐碱化。盐度通过降低叶片含水量和增加Na ⁺和Cl-严重伤害了植物^。浓度。与单独的盐分处理相比，连续的干旱和盐分处理显着提高了叶片的水分状况并减少了有毒离子的吸收，从而降低了活性氧（ROS），丙二醛和膜泄漏的水平。相反，同时进行应力处理所产生的氧化损伤比独立盐分处理所产生的氧化损伤更为明显，这可以归因于水含量的降低，有毒离子的摄入增加或/和抗氧化剂活性的降低。我们的研究结果表明，干旱和盐碱化的生理响应明显取决于这些胁迫的时间模式。