The physiological response of Mirabilis jalapa Linn. to lead stress and accumulation

Smelters, metal refineries and mining operations have all been considered as major sources of metal release into the environment. As a highly toxic and cumulative poison, once in the environment Pb is difficult to remove and can adversely affect human health. Mirabilis jalapa Linn. (The Marvel of Peru) is a fast growing plant that shows potential for phytostabilization of Pb contaminated soils. Fourier Transform Infrared (FTIR) spectrometry was adopted to detect physiological changes in the chemical composition of M. jalapa exposed to six different concentrations of Pb in solution (0, 50, 100, 200, 500 and 1000 μmol L−1 Pb). Results indicated that biomass was reduced in plants grown in Pb treatments compared to controls, although M. jalapa grew typically well at the greatest concentration, 1000 μmol L−1. The concentration of Pb in plant tissues occurred in the order roots > leaves > stems, with a translocation factor of less than 0.04. The absorbance of dominating bands near 3420, 2920, 1610 and 1060 cm−1 firstly increased but then declined in root tissues; the bands respectively corresponding to organic acids, carbohydrate, protein and amino acids. However, no obvious changes were observed in leaves and stems. The results suggest that M. jalapa can reduce transportation of Pb from roots to shoots, subsequently preventing Pb toxicity in shoots.