Influence of pH on lead uptake, chlorophyll and nitrogen content of Nasturtium officinale R. Br. and Mentha aquatica L.

In the present study, effects of pH (5.0, 7.0 and 9.0) and lead (1, 5, 10, 25, 50 and 100 microg mL(-1)) were investigated on uptake of lead, content of chlorophyll and nitrogen in Nasturtium officinale and Mentha aquatica. Total chlorophyll and nitrogen contents were adversely affected from Pb2+ concentrations dose dependently at each pH. The macrophytes were adversely affected by pH 5.0 or more than 9.0. After 12-days Pb2+ treatment, results showed that lead accumulation of macrophyte tissues was variable. According to the parts of the macrophytes, Pb2+ amounts were generally found at all tested pH levels and the metal concentrations for M. aquatica in the following order: root > stem > leaf and for N. officinale root > leaf > stem. Pb2+ concentrations in plant tissues (root, stem, leaf) in relation to pH were generally found for both macrophytes in following order: 7.0 > 9.0 > 5.0. Despite of the fact that high Pb2+ accumulation was observed in root tissues of the macrophytes, low metal accumulation was measured in the above-ground parts indicating low root-leaf translocation. The study indicated that uptake rate of Pb2+ and its toxicity on Chlorophyll and nitrogen contents in the macrophytes were dependent upon pH value of solutions.