Effects of Heavy Metal Stress on Seedling Growth and Antioxidant System in Sorghum (Sorghum bicolor (L.) Moench)

Abstract

Factors that impede the normal growth and development of plants are termed 'stress factors' and result in yield loss. Exposure to elevated concentrations of heavy metals has been demonstrated to induce the production of reactive oxygen species (ROS), which can affect physiological and biochemical processes. The present study investigated the effects of two common heavy metals (Hg2+ and Cd2+) on specific physiological and biochemical parameters of sorghum (Sorghum bicolor (L.) Moench). The study utilized doses ranging from 3 to 15 ppm for the application of heavy metals. The study focused on the effects of these metals on the activities of enzymes (superoxide dismutase and peroxidase), chlorophyll content, fresh weight, dry weight, and proline content in sorghum plants. The study found that applying mercury at 9 ppm resulted in the highest activity of peroxidase (POX), with an observed increase of 69.57% compared to the control. Conversely, cadmium application at 12 ppm elicited the highest activity, increasing by 102.17% compared to the control. For superoxide dismutase (SOD), the peak activity was observed at 6 ppm for both applications, with an increase of 84.16% in the mercury application control group and 121.08% in the cadmium application group compared to the control group. A similar pattern was observed in the chlorophyll content, which initially increased and then decreased. Declines in fresh weight, dry weight, and proline accumulation were also documented.