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Turions are overwintering, dormant organs, produced by aquatic plants. In spring, aerobic dark respiration (RD) and photosynthetic rates (PN) were measured as criteria of metabolic activity and photosynthetic capacity in dormant turions of 7 temperate aquatic plant species. These rates were also measured in old, original turion segments and in the newly formed shoots of sprouting turions. Two non-carnivorous rooting species (Caldesia parnassifolia, Hydrocharis morsus-ranae) and 5 carnivorous rootless species (Aldrovanda vesiculosa, Utricularia vulgaris, U. australis, U. stygia, U. bremii) were studied. RD values of dormant turions per unit fresh weight (range 1.1– 5.4 mmol kgFW h ) were significantly lower (1.9 –13 times) for all species, except A. vesiculosa, than those for old segments of sprouting turions (range 5.2 –14 mmol kgFW h ). However, RD and PN values of old and newly formed turion segments in U. australis and U. stygia were similar. PN values of dormant turions under optimum conditions were either very low or negative, while PN values of old segments of sprouting turions of all species except H. morsus-ranae were very high (18 – 94 mmol kgFW h ). In a Nand P-free solution, turions of all species except A. vesiculosa formed distinct new organs after 6 – 20 days. In conclusion, the intensity of metabolism (both RD and PN) in sprouting turions reaches the level of adult shoots or leaves of the same species. Turions of aquatic plants also function as important storage organs for mineral nutrients (N, P, S and Mg) to ensure the growth of new organs.

The content of macronutrients (N, P, K, Na) and heavy metals (Fe, Mn, Zn, Cu, Ni, Pb, Cd, Co) in plant samples of dominant aquatic macrophytes (Ceratophyllum demersum, Phragmites australis, Trapa natans, Hydrocharis morsus-ranae, Nymphaea alba, Nymphoides peltata, Salvinia natans) from the river Jegricka (Serbia) is presented. Macronutrients content in plant tissue was above necessary limits for plant maximum growth indicating to substantial bioavailability of those elements typical for eutrophic environment. Content of investigated nutrients and heavy metals varied in relation to plant species. Ceratophyllum demersum turned out to be best bioaccumulator for P, K, Fe, Mn, Cu, Ni, Pb, and Co. Salvinia natans accumulated high amounts of N, P, K, Na, and especially Cu and Zn. Nymphaea alba accumulated highest recorded amounts of N and Na. Hydrocharis morsus-ranae accumulated very high amounts of N, P, K, Na, Pb, and Mn. Because of its fast growth, large abundance and homogeneous distribution on this locality, Phragmites australis might have high potential in use for phytoextraction of macronutrients and heavy metals. The application of macrophytes as indicators might be limited depending on the varying of environmental conditions on different localities.