Arsenate toxicity to Pisum sativum: mineral nutrients, chlorophyll content, and phytase activity

A significant mechanism of arsenate toxicity to Pisum sativum is interference with its mineral nutrient balance. This conclusion is supported by assessments made after exposing P. sativum L. cv. "Phenomen" for 12 days to 12.5, 20.8, and 33.3 mg, and for 32 days to 7.5, 22.1, 36.7, and 73.3 mg of sodium arsenate/kg dry wt soil in the greenhouse. At 20.8 mg of arsenate, mobilization of manganese from the cotyledons was significantly increased and that of zinc decreased. Nitrogen accumulated in the roots. On Day 32, at 22.1 mg of arsenate, magnesium, zinc, and manganese contents of the roots increased, but that of phosphorus of the shoot decreased. The distribution pattern and the ratios between individual elements were severely altered. Relatively more arsenic accumulated from the low than the high soil concentrations. Growth of the shoot was more affected than that of the roots. After a 32-day exposure, chlorophyll content of the leaves increased, but the chlorophyll a/b ratio decreased. On Day 12, at 12.5 mg and 20.8 mg of arsenate, in vivo phytase activity was 64 and 66% that of the controls, respectively.