The crucial elements for lettuce (Lactuca sativa L.) growth under DMA stress and the linkage with DMA behavior: A new application of ionome.

Dimethylarsinic acid (DMA) is one of the common arsenic (As) species present in soil and is more toxic to plants than others. Identifying the crucial elements for plant growth under DMA stress is essential to enhance plant tolerance to DMA. Herein, we provided for the first time an ionome-based approach to address this issue. The phenotype, As species and concentrations of 11 essential elements in lettuce tissues were monitored under exposures of 0.1, 0.5, 1, 2, 5 mg L DMA in hydroponic culture for 32 days. Lettuces remained normal (no significant difference in phenotype from the control) under 0.1-2 mg L DMA stress, and were inhibited with fresh weights of leaf and root under 5 mg L DMA stress. Integrating the difference in ionome profiles between the two growth states (normal and inhibited) and the responses of the individual element, Mg and S were clarified as the most possible candidates for the crucial elements for lettuce growth under DMA stress. Under 5 mg L DMA stress, the accumulation of Mg and S declined, yet their BCF values were significantly increased, which was consistent with the change in BCF of DMA. Based on the physiological functions of Mg and S and the toxicity of DMA, it could be inferred that the enhanced transfer of Mg and S to leaves should be induced by the potential damage caused by the increased DMA accumulation in leaves, and would result in a shortage of both elements in roots as well as the growth inhibition.