Response of phosphorus sensitive plants to arsenate

Abstract Arsenate (As (V)) is a highly toxic species of arsenic (As) which is also an excellent phosphate analogue. Plant species that are adapted to phosphorus (P) impoverished soil display a negative response to elevated phosphate due to an inability to downregulate P acquisition. Despite widespread As contamination and shared transport systems for As (V) and P uptake, little to no information is available on the response of P-sensitive plants to As (V). The aim of the study was to investigate the response of P-sensitive plants to As (V). One high (Hakea prostrata R.BR) and one moderate (Banksia seminuda B.Rye) P-sensitive species and one vegetable plant species (Cucumis sativus L.) were grown in nutrient solution containing different As (V) concentrations. Based on EC50 data from nutrient culture, Hakea prostrata was the most sensitive species to As (V) followed by B. seminuda and C. sativus. Critical exogenous concentrations of As that reduced plant growth by 50 % (EC50) in H. prostrata, B. seminuda and C. sativus were respectively 0.64, 0.76 and 1.08 μ M for shoot and 0.66, 0.51, 1.07 μ M for root. Hakea prostrata had the highest translocation factor (ratio of As concentration in shoot to root) of 0.11, followed by B. seminuda (0.03), and C. sativus (0.01). Plant species with high and moderate P sensitivity were associated with high sensitivity to As (V) exposure and accumulation in shoots. The increased sensitivity has important implications in ecological risk assessment and selection of plant species for rehabilitation. The impacts of As(V) at low P levels in soil solution is needed to inform contaminated site assessment and rehabilitation.