The role of vanadium in green plants

Abstract

In a series of experiments, it is demonstrated that the trace element vanadium (4·10^-7 g-at/l as NH₄VO₃) has a considerable positive influence on the synthesis of δ-aminolevulinic acid (δ-ALA) in the autotrophically growing green algaChlorella pyrenoidosa, the effect being visible by an enhanced output of the amino acid into the culture medium in presence of levulinic acid (LA). The level of intracellularly accumulated δ-ALA, however, is not changed in presence of the metal. The V-effect on exogenous found δ-ALA is suppressed, when LA is added to the nutrient medium at low pH (pH 5), although V-uptake into the algal cells is not disturbed by LA. As demonstrated in culture media with various nitrogen sources (urea, partially hydrolized urea, ammonium salts), the development of the pH during the cultivation time is important for the presentation of the V-effect on δ-ALA. It is suggested that vanadium acts as a catalyst in the conversion of 4,5-dioxovaleric acid to δ-ALA by transamination.