Possible Application of the Medicinal Plant Hyoscyamus albus in Phytoremediation: Excess Copper Compensates for Iron Deficiency, Depending on the Light Conditions

Abstract

Seedlings of the medicinal plant Hyoscyamus albus were supplied with an excess of Cu to examine the possible application in phytoremediation. The seedlings were cultured in B5 medium supplied with basal 0.1 μM Cu and 200 μM Cu under various light conditions: short day (SD); long day (LD); and continuous light (CL). In addition, the effect of supplying 200 μM Cu under Fe deficiency was determined, in order to elucidate the interaction between Cu and Fe. Interestingly, Fe-deficiency symptoms that developed in plants grown with basic levels of Cu under LD almost disappeared when excess Cu was supplied. Plant growth mainly depended on the photo irradiation period (SD < LD~CL); and 200 μM Cu did not inhibit growth at all when Fe was available, whereas in the absence of Fe, CL caused damage to growth. Analysis of the Cu and Fe contents of the plants revealed that Cu was distributed equally in both the aerial parts and roots, whereas most of the Fe was found in the roots; under Fe deficiency, Cu accumulation in the roots apparently increased. Cu was mainly distributed in the soluble fraction, which included vacuoles and the cell-wall fraction. These results provide evidence indicating that H. albus seedlings are tolerant of Cu present in excess. Furthermore, excess Cu was able to compensate for Fe deficiency, depending on the light conditions. Continuous light inhibited this effect, probably as a result of the induction of Mn deficiency. The possible applications of this newly discovered cuprophyte are discussed.