Abstract:
This study was planned to contribute the views examining the physiological mechanisms of selenium-induced growth reductions with regard to selenium and plant nutrient interactions. Growth inhibition in the seedlings and the changes in nutrient compositions of epidermal cells with administration of increasing concentrations of selenium were investigated at the initial growth stage, which is the most stress-sensitive stage, of plant. The effects of selenium on Lycopersicon esculentum Mill. seedlings were investigated by EDX (Energy Dispersive X-Ray Microanalysis) analysis of the regions, approximately 450 μm x 500 μm in size, with use of low-vacuum (∼ 24 Pascal) Scanning Electron Microscope, and SEM images were obtained. Increasing concentrations of selenium in the nutrient solution led to decreased cell growth particularly in the hypocotyl and roots, and to increased selenium content in the cells. The growth inhibitions were found at the selenium concentrations of ≥ 100 ppm. Development of the glandular hairs in the hypocotyl epidermal system was significantly reduced with the administration of ≥ 200 ppm of selenium. Development of the absorbing hairs in the roots was decreased in parallel with the increasing selenium concentrations in the nutrient solution; and because the development of the root is often limited to only to the development of radicula at the selenium concentrations of 500 and 1000 ppm, no absorbing hairs was found in these roots. Some macro- and micronutrient contents of radicle and hypocotyl epidermal cells were changed in response to selenium toxicity. In conclusion, ≥ 200 ppm of selenium administered in the form of SeO2 was certainly toxic for the initial growth period of Lycopersicon esculentum cv. H-2274
