Arsenite toxicity and uptake rate of rice (Oryza sativa L.) in vivo.

Toxicity threshold of arsenite on intact rice seedlings was determined and arsenite uptake characteristics were investigated using non-toxic concentrations of arsenite. The arsenite toxicity threshold was 2.4 μM arsenite which reduced growth by 10% (EC(10)). The two highest arsenite levels induced wilting of seedlings and reduced both, transpiration rate and net photosynthetic rate. Arsenic content in plant tissue increased up to 10.7 μM arsenite and then declined with increasing arsenite concentration in the treatment solution. The contents of Si, P, K, and of micronutrients Cu, Fe, Mn and Zn in shoot d.m. were reduced by arsenite levels ≥ 5.3 μM. In the non-toxic range, arsenite uptake rate was linearly related to arsenite concentration. High arsenite levels reduced growth without being taken up which might be due to increasing binding of arsenite to proteins at the outer side of the plasmalemma.