Mn, as Fe, Zn, Cu and Ni is a heavy metal and also a necessary element all the living organisms. Excessive Mn nutrition causes a strong oxidative stress. The aim of the studies was to determination the effect of Se treatment (as sodium selenite Na2O4Se3) to alleviate the Mn stress of plants. Because of its sensitivity to oxidative stress induced by excessive concentrations of Mn a model plant was lettuce (Lactuca sativa L. ‘Sunny’). The studies were conducted in a controlled environment growth room in stable climate conditions: 16 h photoperiod; temperature light/dark 18.0 ±0.5°C/16.0 ±0.5°C; relative humidity 70-80%; quantum flux density 195-205 μmol m−2 s−1. Plants were grown hydroponically in nutrient solution characterized by excessive Mn content (19.2 mg dm−3) and different contents of Se (control; 0.77, 1.05, 1.33 mg dm−3). In all the combination were also tested different foliar sprays (distilled water and a 0.005% Se solution). Plants grown under conditions described above take up and transported Se from nutrient solutions into their leaves with a significant reduction of Mn concentration and changes in the plant nutrient status. With the increase in the concentrations of Se clearly narrowed quantitative relations in the leaves between this element and micro-metallic. Increasing Se levels in nutrient solution has a positive influence on the growth of plants, but Se foliar treatment generally decreases plant yield. The study shown that Se application may lead to alleviation of Mn stress of plants, with simultaneous reduce in Mn concentration in leaves - which may be of practical importance also in the cultivation of more economically important species.
