Lanthanum and cultivated plants

Lanthanum (La), is a metallic element belonging to the group of rare earth elements (REEs). Both REEs and La are present in small concentrations in all parts of the biosphere. REEs are widely used in numerous areas of human activity. The effect of La on the life processes of plants has been studied in detail. Plants can absorb La through roots and aerial organs. Most of the absorbed La is accumulated in the root. Lanthanum affects the absorption and accumulation of other elements in plants through synergism and antagonism. Lanthanum ions might partly be able to replace calcium in plants and magnesium in chlorophyll molecules. Numerous publications point out the positive effects of La on plant growth. The stimulating and inhibitory effects of La on plant growth are associated with alternations in mineral nutrition, enzyme activity, levels of endogenous hormones, tolerance to abiotic and biotic stress, etc. Lanthanum may have a positive effect on photosynthetic rates, and is associated with differences in chloroplast development, increased light absorption, excitation energy distribution, promotion of the Hill reaction, as well as changes in the carboxylation activity of rubisco. Lanthanum might be partly able to alleviate the effect of undesirable ecological factors. In the environment, contamination and phytotoxicity of La rarely occur. The phytotoxic mechanisms of La involve necrotic damage, nutrient imbalance, destroyed cell ultrastructure, disturbance of cell proliferation, inhibition of the specific enzymes and other functional proteins, phosphate deficiency, membrane lipid peroxidation, and, as a final result, growth inhibition. Low concentrations of La favor plant growth, but the mechanisms are still not sufficiently understood. Thus, molecular-level investigations to elucidate the stimulative and toxic mechanisms of La in higher plants are desirable.