Co-uptake of atrazine and mercury by rice seedlings from water

The uptake of atrazine (ATR) by rice seedlings (Oryza sativa L.) from nutrient solution was investigated in the presence and absence of Hg²⁺ over a period of 96 h. Either ATR or Hg²⁺ was found phytotoxic to rice seedlings, as they inhibited the seedling growth. The seedlings showed about 50% biomass reduction when exposed to 1.0 mg/L Hg²⁺ alone in nutrient solution, and about 80% reduction when exposed to 12.0 mg/L ATR alone. Observed ATR and Hg²⁺ levels (in mg/kg) in seedlings are not related to biomass changes. When either ATR or Hg²⁺ was applied, the concentrations in seedlings increased largely in proportion to those in nutrient solution. The presence of Hg²⁺ at 0.1 and 1.0 mg/L in solution caused a small-to-moderate decline in ATR uptake by the seedlings, the effect being largely independent of the ATR concentration in nutrient solution (at 6.0 and 12.0 mg/L). The presence of ATR (at 6.0 and 12.0 mg/L) in the nutrient solution led to small-to-moderate irregular changes in the Hg²⁺ concentrations in rice seedlings. The overall results showed that there was no significant interdependence between the uptakes of ATR and Hg²⁺ by rice seedlings, which is in contrast to the enhanced ATR uptake noticed earlier with Pb²⁺ ion. Plant uptake of non-ionic organic compounds, such as ATR may be partly through water channels on the plasma membranes of plant cells.