Damage suffered by swamp morning glory (Ipomoea aquatica Forsk) exposed to vanadium (V)

To elucidate the physiological and morphological responses generated by vanadium (V) in plants, hydroponic culture experiments were performed with swamp morning glory (Ipomoea aquatica Forsk) exposed to 0 mg L(-1) to 2.50 mg L(-1) pentavalent V [V(V)] in Hoagland nutrient solutions. The concentration of chlorophyll a, chlorophyll b, and carotene peaked at a V(V) concentration of 0.05 mg L(-1) and gradually decreased at higher V(V) concentrations. Similarly, the plant biomass was stimulated at low levels of V(V) and was inhibited when V(V) concentrations exceeded 0.1 mg L(-1). Pentavalent V had negative effects on the uptake of phosphorus (P) by roots, shoots, and leaves. The biological absorption coefficients of V of the roots were higher than those of the aerial parts. Under low concentrations of V(V) exposure, the predominant species of V in the aerial parts was tetravalent V [V(IV)], whereas V(V) became more prevalent when concentrations of V(V) in the solution was higher than 0.50 mg L(-1). In the roots, however, the concentrations of V(V) were always higher than those of the V(IV), except in the control group. Organelles in the V(V)-treated leaves were distorted, and the periplasmic space became wider. These results indicate V(V) has concentration-dependent effects on the physiological properties of swamp morning glory, whereas the plant has the ability to develop self-protective function to adapt to the toxicity of V(V).