Interaction of Arsenic and Phosphate on Their Uptake and Accumulation in Chinese Brake Fern

Interactive effects of arsenate (As (V)) and phosphate (Pi) were investigated under hydroponic culture. Arsenic concentrations in fronds and roots of Chinese brake fern (Pteris vittata L.) significantly (p0.05) increased with increasing As (V), but decreased (p0.05) with increasing Pi in nutrient solution. Phosphate uptake was significantly (p0.05) inhibited by 1000 mol L-1 As (V). Under 100 mol L-1 As (V), frond phosphorus (P) increased at 100 and 1000 mol L-1 Pi, and root P increased at 250 mol L-1 Pi exposures. Arsenic and P concentrations in fronds and roots of Chinese brake fern were negatively correlated (p0.05). Arsenate treatments enhanced As and P transport to fronds, while increasing Pi inhibited their transportation, with highest frond P and As (%) obtained under 100 mol L-1 treatment. pH values in nutrient solution increased with increasing exposure time, but decreased with increasing Pi levels. Dissolved organic carbon (DOC) contents (dry weight) in nutrient solution decreased with increasing Pi levels, both for treatments with and without As (V). Arsenate at 1000 mol L-1 significantly (p0.05) increased DOC contents, especially for treatment without Pi. Six organic acids were detected in root exudates of Chinese brake fern, with oxalic and malic acids being most dominant.