Effect of cadmium on cytogenetic toxicity in hairy roots of Wedelia trilobata L. and their alleviation by exogenous CaCl2

Effects of cadmium (Cd) alone and in combination with calcium on mitosis and chromosomal aberration in the hairy root tips of Wedelia trilobata were investigated. The results showed that Cd concentrations below 50 mu mol/L had a lesser or even a promoting effect on the mitotic index (MI) and the rate of chromosomal aberration in hairy root tips, while those higher than 100 mu mol/L significantly decreased the MI and gradually stimulated the rate of chromosomal aberrations with prolonged time and increasing concentrations of Cd. Concentrations of 50 mu mol/L Cd mainly induced C-mitosis, while more than 100 mu mol/L Cd mainly caused chromosome breakage and chromosome adhesion in hairy root tip cells. When cultured with 300 mu mol/L Cd, micronuclei were only observed in the interphase, middle, and late phase of hairy root tip cells. Compared with untreated controls, exogenous calcium had an alleviating effect on Cd-induced cytotoxicity by effectively enhancing the MI and reducing the rate of chromosomal aberration in root tip cells. The results presented here provide evidence that W. trilobata hairy roots with rapid autonomous growth could be used as a sensitive tool for monitoring and evaluation of Cd pollution in the environment.