The objective of our study was to investigate the effect of As(III)- and As(V)-treatments on the dry mass and nutrient uptake of plants.

A nutrient solution experiment was carried out with sunflower seedlings to investigate the effect of the different arsenic forms. Seedlings were grown in climate room under strictly regulated environmental condition for 21 days. The concentration of the As(III)- and As(V)-treatments were 0, 1 and 3 mg dm-3. The number of the replications was 3, separately in the case of As(III)- and As(V)-treatments. Among the macro- and mesoelements, the concentration of phosphorus (P) and sulphur (S) was measured. The concentration of copper (Cu), iron (Fe), zinc (Zn), molybdenum (Mo) and manganese (Mn) was also determined from the samples.

Based on the obtained data, it was obvious that the dry mass of shoots and roots was reduced as a result of the performed As(III)-treatments. The dry mass of the shoots was also reduced in the case of the As(V)-treatments; however, the dry mass of the roots did not vary significantly under As(V)-stress.

According to the obtained results, the As(III)- and As(V)-treatments increased the concentration of P and S in the shoot and root. The amount of Cu, Fe and Zn in the shoot was reduced; however, the concentration of these element in the root was increased owing to arsenate and arsenite stress. As(III) and As(V) caused increasing

tendency in the Mn content of the root and the shoot, respectively. In the case of both As(III)- and As(V)-treatments, it was found that the concentration of Mo was decreased in the shoot. The Mo content in the root was also decreased in the case of the 3 mg dm-3 As(V)-treatment. It was also obvious that the 1 mg dm-3 As(III)-treatment increased the amount of Mo in the root, even if the uptake of Mo was hampered when the seedlings were treated with 3 mg dm-3 As(III).

Keywords: sunflower, arsenic, phosphorus, sulfur, microelement, dry mass