Being a trace element, selenium (Se) has beneficial effects on vegetables growth and development. Nevertheless, the impact of Se on the lettuce (Lactuca sativa L.) characteristics has not been systematically examined. In our study the plants of an autochthonous local Slovenian variety of crisp lettuce ’Ljubljanska ledenka’ were exposed to foliar treatment with an aqueous solution of Na2SeO4. The foliage of target plants underwent two rounds of spraying with a nutrient solution at a 5-day interval. In the first experiment, the concentrations used were 0 (distilled water spray as a control); 1 + 1; 2 + 2, and 5 + 5 mg Se L-1. In the second experiment, the concentrations were 0; 10 + 0, 10 + 10, and 10 + 50 mg Se L-1. First spraying began at 3 fully developed leaves. The experiment was carried out in a completely randomized design in a plastic greenhouse on a field near Ljubljana (46°04'46.0"N, 14°34'20.0"E). No significant differences in the shoot height, leaf number per plant, and root dry matter were observed between treatments. Leaves in control and 1+1 mg Se L-1 treatment had higher dry matter percentage in comparison with other treatments. The growth analysis revealed that 5+5, 10+0, and 10+10 mg Se L-1 treatments increased the weight of shoots. The shoots yield was reduced after foliar application of strong enlarged doses of selenate (10+10 mg Se L-1). The Se concentration in shoots increased in proportion to the level of the concentration of Na2SeO4 and the highest values were recorded from the plants in which 10+10 mg Se L-1 was applied. The portion of photosynthetic pigments (chlorophylls and carotenoids) decreased from the control group to the treatment with the highest Na2SeO4 solution (10 + 50 mg Se L-1).

Key words: selenate, lettuce, Lactuca sativa, growth components, pigments