Levels of Organic Compounds, Number of Microorganisms and Cadmium Accumulation in Festuca ovina Hydroponic Culture

Understanding the microbiological, biochemical and physiological aspects of phytoremediation of soil and water environments polluted to different degrees with heavy metals has very important theoretical and practical implications. In this study, a comparison was made between total cadmium concentration in root and shoot tissues as well as concentrations of particular fractions of Cd immobilized by roots of Festuca ovina (Sheep’s fescue) hydroponically cultivated in nutrient solutions supplemented with 1 μg Cd ml⁻¹ and those cultivated at 10 μg Cd ml⁻¹. After three weeks of F. ovina cultivation, the number of bacterial CFU and the amounts of organic chelators, siderophores, proteins and reducing sugars in the growth medium and on the root surface were higher at 10 than at 1 μg Cd ml⁻¹. The grass also reacted to the high Cd concentration by a decrease in plant growth and dehydrogenase activity in root tissues. The concentration of Cd determined in fractions bound with different strength in roots was significantly dependent on Cd concentration in the growth medium. When the plants were grown at 1 μg Cd ml⁻¹, 9% of the immobilized cadmium was loosely bound to the root surface, 20% was exchangeable adsorbed, and 28% was bound by chelation; at 10 μg Cd ml⁻¹, the respective values were 12%, 25%, and 20%. About 43% of the immobilized cadmium remained in roots after sequential extraction, and bioaccumulation factors in shoots had the same values independently of Cd concentration.

At both Cd concentrations, the cadmium translocation index for F. ovina was low (< 1), which is why this grass can be recommended for phytostabilization of the metal under study.