Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants.

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L(-1)) and a soil pot trail (control, 60 mg As kg(-1)). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O2 kg(-1) root d.w.d(-1)), As uptake (e.g., 8.8-151 mg kg(-1) in shoots in 0.8 mg As L(-1) treatment), translocation factor (2.1-47% in 0.8 mg As L(-1)) and tolerance (29-106% in 0.8 mg As L(-1)). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity.