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Abstract

Plants often face combinatorial stresses in their natural environment. Here arsenic (As) toxicity was combined with hypoxia (Hpx) in the roots of Arabidopsis thaliana as it often occurs in nature. Arsenic inhibited growth of both roots and leaves, while root growth almost entirely ceased in Hpx. Growth efficiently resumed, and hypoxia marker transcripts decreased upon re‐aeration. Compromised recovery from HpxAs treatment following re‐aeration indicated some persistent effects of combined stress despite lower As‐accumulation. Root glutathione redox potential turned more oxidized in hypoxia and most strongly in HpxAs. The more oxidizing root cell redox potential and the lowered glutathione amounts may be conducive to the growth arrest of plants exposed to HpxAs. The stresses elicited changes in elemental and transcriptomic composition. Thus calcium, magnesium and phosphorous amounts decreased in rosettes, but the strongest decline was seen for potassium. The reorganized potassium‐related transcriptome supports the conclusion that disturbed potassium homeostasis contributes to the growth phenotype. In a converse manner, photosynthesis‐related parameters were hardly affected, while accumulated carbohydrates under all stresses and anthocyanins under hypoxia, exclude carbohydrate limitation. The study demonstrates the existence of both synergistic since aggravating effects and antagonistic effects of single and combined stress.