Effects of cadmium stress on hairy roots of Daucus carota

Axenic hairy root cultures of Daucus carota, treated with cadmium sulfate (100 mu mol/L and 1 mmol/L) for 4 days, readily accumulated high concentrations of Cd without any reduction in fresh weight or in total protein content. Hairy roots exposed to Cd: a) showed a stress ethylene production up to 10 fold higher than controls, and at the same time, no differences in lipid peroxidation; b) produced phytochelatins (PC2, PC3, PC4, PC5 and PC6), which bound Cd ions by means of HMW and LMW complexes; no phytochelatin synthesis was detected in controls or in the presence of buthionine sulfoximine or cycloheximide; and c) showed two protein bands with a molecular mass, respectively, of about 30,000 and 35,000, not present in the uninduced material. The apparent insensitivity of carrot hairy roots to short-term Cd stress is probably due to the prompt induction of such an efficient "protection pool".