Effects of Heavy Metal Cr~(6+) Pollution on Physiological and Biochemical Characteristics of Pepper (Capsicum Annuum L.) Seedlings

The effects of heavy metal Cr6+ pollution on the physiological and biochemical characteristics of pepper (Capsicum annuum L.) were studied through water cultivation. The results showed that there existed significant differences in the aboveground dry weight and underground dry weight between the control groups and the treatments of low Cr6+ concentration. The ratio of root to crown (dry weight) tended to increase, but the pepper’s weight, the content of chlorophyll and the ratio of chlorophyll a/b decreased remarkably with the increasing of Cr6+ concentration. Superoxide dismutase (SOD) and peroxidase (POD) are two important protective enzymes in plants. Low concentration of Cr6+ had little inhibition on the activity of SOD in the pepper seedlings, while that of POD increased dominantly. As the Cr6+ concentration increased, the plasma membrane's permeability of the pepper seedlings and the content of malondialdehyde (MDA) increased gradually, and the activity of SOD decreased. When the concentration of Cr6+ was 20 ml·L-1, the activity of POD reached a peak then decreased, suggesting that POD had great adaptability to the chromium stress, and played a critical role in the resistance to chromium stress.