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 stu dy aimed to investigate the possibility of using PCs as a biomarker for chr onic Cd toxicity in Silene vulgaris. For this purpose, the effects of Cd on growth rate, related to plant weight, and the PC concentrations were recor ded throughout the bigger part of the vegetative phase. The lowest concentr ations 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 e xposure concentration of 2 mu M Cd, the toxic effect increased with plant w eight. At 3.5 mu M Cd, the plant growth rates were inhibited up to 90%. Fur ther increases of the exposure concentration did not produce additional inh ibition. Root PC concentrations correlated with growth inhibition only at t he lower Cd concentrations, i.e. up to 2 mu M Cd. Above this concentration the correlation was lost.