Hydrogen peroxide modulate photosynthesis and antioxidant systems in tomato (Solanum lycopersicum L.) plants under copper stress.

Plant growth and development could be modulated by minute concentrations of hydrogen peroxide (HO) which serves as a signaling molecule for various processes. The present work was conducted with an aim that HO could also modify root morphology, morphology and movement of stomata, photosynthetic responses, activity of carbonic anhydrase, and antioxidant systems in tomato (Solanum lycopersicum L.) plants under copper stress (Cu; 10 or 100 mg kg soil). Roots of 20 d old plants were dipped in 0.1 or 0.5 mM of HO solution for 4 h and then transplanted to the soil filled in earthen pots. High Cu stress (100 mg kg soil) altered root morphology, reduced chlorophyll content and photosynthetic capacity and also affected movement of stomata and generation of antioxidant species at 40 d after transplantation. Further, root dipping treatment of HO to plants under stress and stress-free conditions enhanced accumulation of proline and activity of catalase, peroxidase, and superoxide dismutase, whereas production of superoxide radical (O) and HO were decreased. Overall, HO treatment improved growth, photosynthesis, metabolic state of the plants which provided tolerance and helped the plants to cope well under Cu stress.