Selenium effects on oxidative stress in potato

Higher plants are considered not to require selenium (Se). However, it has recently been shown that Se increases the antioxidative capacity and stress tolerance of lettuce (Lactuca sativa L.) and ryegrass (Lolium perenne L.). This research was undertaken to investigate the antioxidative properties of Se during photooxidative stress in potato (Solanum tuberosum L.) and to determine the defence mechanisms. Potato plants were exposed to 600 mumol/m(2)/s light intensity at low temperature (4 degreesC) or paraquat-mediated oxidative stress. The stress responses were monitored by measuring chlorophyll content and following changes in chlorophyll fluorescence and membrane ion leakage. Moreover, the effects of Se on the transcript levels of chloroplast CuZnSOD, mitochondrial MnSOD, glutathione peroxidase (GPX), and psbA were analyzed using northern hybridization. Se supplementation improved the recovery of chlorophyll content following light stress. After prolonged exposure to light, the reduction of Fv/Fm was slightly lower compared with plants cultivated without additional Se. The photosynthesis of Se treated plants was somewhat more tolerant of paraquat and the integrity of membranes was improved during oxidative stress. Se altered transcript accumulation of chloroplast CuZnSOD and GPX but the MnSOD and psbA transcript levels were unaffected. The results suggest that Se is an antioxidant or it activates protective mechanisms, which can alleviate oxidative stress in the chloroplasts. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.