A study on selected physiological parameters of plants grown under lithium supplementation

Exposure of sunflower and maize plants to increasing concentrations of lithium (0-50 mg Li dm(-3)) in a nutrient solution induced changes in biomass, leaf area and photosynthetic pigment accumulation, as well as levels of lipid peroxidation. The highest applied lithium dose (50 mg Li dm(-3)) evoked a significant reduction in the shoot biomass for both examined species, as well as necrotic spots and a reduction of the leaf area in sunflower plants. An enrichment of a nutrient solution with 5-50 mg Li dm(-3) did not significantly affect chlorophylls a and b and the carotenoid content in sunflower plants. However, in maize, a significant decrease in all pigment content under highest used lithium concentration was noted. The levels of lipid peroxidation of the cell membranes in leaves of sunflower plants and the roots of maize increased significantly in the presence of 50 mg Li dm(-3), which suggests disturbances of the membrane integrity and pro-oxidant properties of the excess lithium ions. Nonetheless, in maize, an increase of shoot biomass and leaf area in the presence of 5 mg Li dm(-3) was found. An analysis of the metal content indicated that lithium accumulated significantly in sunflower and maize shoots in a dose-dependent manner, but differences occurred between species. The sunflower plants accumulated considerably greater amounts of this metal than maize. The potassium content in shoots remained unchanged under lithium treatments, except for a significant increase in the potassium levels for sunflower plants grown in the presence of 50 mg Li dm(-3). These results suggest that lithium at 50 mg Li dm(-3) is toxic to both plant species, but the symptoms of toxicity are species-specific. Moreover, the lithium influence on plants is dose-dependent and its ions can exert toxicity at high concentrations (50 mg Li dm(-3)) or stimulate growth at low concentrations (5 mg Li dm(-3)).