The effect of cadmium on growth and antioxidant responses in the safflower (Carthamus tinctorius L.) callus

Abstract

Safflower (Carthamus tinctorius L.) callus cultures grown in the presence of different concentrations (0-100 µM) of cadmium were assayed for growth, Cd accumulations, and antioxidative responses. Cadmium inhibited the growth of calli by 25% and 46% at 75 and 100 µM Cd concentrations, respectively. Cadmium concentration in the calli increased with an increased Cd supply in the growth medium. Calli accumulated 334 mg Cd kg^{-1} of their dry weight at 100 µM Cd. Cadmium induced oxidative stress, which was indicated by modulating antioxidant (glutathione and \alpha-tocopherol) levels and antioxidative enzymes. The effect of Cd on glutathione (GSH) was dose-dependent. The GSH content increased up to a concentration of 75 µM Cd and then decreased. Levels of \alpha-tocopherol showed a significant increase with the increase in concentrations of Cd in the media. Antioxidant enzyme activity increased significantly up to a concentration of 75 µM Cd. Concentrations of Cd greater than 75 µM resulted in a decline in antioxidant enzyme activity. Increased antioxidant levels and antioxidant enzyme activity in Cd-treated calli indicate that Cd detoxification and accumulation in the safflower callus might be associated with the efficiency of these mechanisms.