Effects of cadmium exposure on the growth, photosynthesis, and antioxidant defense system in two radish (Raphanus sativus L.) cultivars

Radish is representative root vegetable; its edible parts are directly in contact with Cd-contaminated fields. Two radish cultivars (H4 and L19) with different resistance to Cd were selected to compare their growth, photosynthesis, and antioxidant systems. Our results revealed that H4 was more sensitive to Cd pollution than L19; a significant decrease in the biomass of H4 was observed at higher Cd concentrations. With increasing Cd concentrations, the net photosynthetic rate, effective quantum yield of PSII photochemistry, electron transport rate through PSII, and photochemical quenching were all lowered, however, reductions were more obvious in H4 compared to L19. Further, both peroxidase and catalase activities of L19 were remarkably higher than those of H4. Smaller reductions in ascorbic acid and no obvious changes in glutathione were observed in the leaves of H4. These results suggest that the differences in Cd tolerance could be attributed to the distinct photosynthetic parameters and differences in antioxidant system between L19 and H4.