Phosphorus deficiency modifies As translocation in the halophyte plant species Atriplex atacamensis

Most arsenic in surface soil and water exists primarily in its oxidized form, as arsenate (As(V); AsO₄^3-), which is an analog of phosphate (PO₄^3-). Arsenate can be taken up by phosphate transporters. Atriplex atacamensis Phil. is native to northern Chile (Atacama Desert), and this species can cope with high As concentrations and low P availability in its natural environment. To determine the impact of P on As accumulation and tolerance in A. atacamensis, the plants were cultivated in a hydroponic system under four treatments: no As(V) addition with 323µM phosphate (control); 1000µM As(V) addition with 323µM phosphate; no As(V) and no phosphate; 1000µM As(V) addition and no phosphate. Phosphate starvation decreased shoot fresh weight, while As(V) addition reduced stem and root fresh weights. Arsenate addition decreased the P concentrations in both roots and leaves, but to a lesser extent than for P starvation. Phosphorus starvation increased the As concentrations in roots, but decreased it in shoots, which suggests that P deficiency reduced As translocation from roots to shoots. Arsenate addition increased total glutathione, but P deficiency decreased oxidized and reduced glutathione in As(V)-treated plants. Arsenate also induced an increase in S accumulation and nonprotein thiol and ethylene synthesis, and a decrease in K concentrations, effects that were similar for the P-supplied and P-starved plants. In contrast, in As(V)-treated plants, P starvation dramatically decreased total soluble protein content and increased lipid peroxidation, compared to plants supplied with P. Phosphorus nutrition thus appears to be an important component of A. atacamensis response to As toxicity.