Water relations of yellow sweetclover under the synergy of drought and selenium addition

In the last two decades drought and elevated toxic metal concentration phenomena in plants have gained the interest of the scientific world. Nevertheless, up to day relatively little ecophysiological research concerning the effect of water stress and elevated selenium (Se) concentration on plant water relations is available. A pot experiment was conducted in order to evaluate the effects of the implied synergy of drought and Se uptake on water relations of yellow sweetclover (Melilotus officinalis L.). The effects of two different Se concentrations (0 mg Se L^?1 irrigation water, 3 mg Se L^?1 irrigation water) and two water regimes (full irrigation — limited irrigation) applied to seedlings of yellow sweetclover were detected by measuring changes in water potential, relative water content, stomatal conductance, transpiration rate and tissue Se concentration. The findings suggest that yellow sweetclover, concentrating up to 200 μg Se g^?1 dry weight in its tissues, could be considered a secondary Se accumulator. Se effect on water relations was more evident under limited irrigation, as expressed by decreased values of leaf water potential, transpiration rate and stomatal conductance, limiting the flux rate of the water solution in the conducting system of the plant.