Uptake and Translocation of Arsenite and Arsenate by Pteris Vittata L.: Effects of Glycerol, Antimonite and Silver.

The arsenic hyper accumulator, Pteris vittata, is capable of taking up both arsenate (As V) and arsenite (As III). As III uptake in living cells is mainly through aquaglyceroporin transporters. Our aim was to understand whether the As III uptake mechanism in P. vittata is also via aquaglyceroporins. For this, separate experiments were conducted to study  the uptake of 0.1mM As III and 0.1mM As V against different concentrations of  glycerol and antimonite (0, 0.1, 1, 10, 100mM) which are analogs of As III. The effect of an aquaporin inhibitor, silver nitrate (AgNO₃) at concentrations 0, 0.001, 0.01 and 0.1 mM was also studied against 0.1mM As III and 0.1mM As V. The total arsenic concentration in the frond ranged from 4.58 to 6.32 mg/kg in presence of glycerol with no significant difference between the treatments (p<0.05). The arsenic concentration in the root ranged from 3.8 to 6.2 mg/kg. Similar results were observed in the antimonite treatment with frond and root concentration from 4.4 to 5.7mg/kg and 3.9 to 4.2 mg/kg respectively.  The presence of glycerol or antimonite had no impact on As III or As V uptake by P. vittata. However, in the presence of 0.1mM AgNO₃ there was 64% and 58% reduction in the uptake of As III in the fronds and roots respectively. Hence, As III uptake might be via an aquaporin transporter different from the glycerol and antimonite transporters.  Further as the As III analogs and the aquaporin inhibitor had no impact on As V uptake, As III and As V might be taken up by different transporters.