Quantitative relationship between phytochelatin accumulation and growth inhibition during prolonged exposure to cadmium in Silene vulgaris

Phytochelatins (PCs) are known to detoxify heavy metals in plants. This study aimed to investigate the possibility of using PCs as a biomarker for chronic Cd toxicity in Silene vulgaris. For this purpose, the effects of Cd on growth rate, related to plant weight, and the PC concentrations were recorded throughout the bigger part of the vegetative phase. The lowest concentrations of Cd used, 1 and 2 mu M, inhibited plant growth rates by 30 and 50%, respectively, independent of the weight of the exposed plants. Above an exposure concentration of 2 mu M Cd, the toxic effect increased with plant weight. At 3.5 mu M Cd, the plant growth rates were inhibited up to 90%. Further increases of the exposure concentration did not produce additional inhibition. Root PC concentrations correlated with growth inhibition only at the lower Cd concentrations, i.e. up to 2 mu M Cd. Above this concentration the correlation was lost.