The physiological responses of two aquatic plants, Alternanthera philoxeroides (Alligator Weed) and Nasturtium officinale (Watercress) to heavy metal exposure

Abstract

Abstract Alternanthera philoxeroides is a nonnative invasive plant species that has spread throughout the wetland ecosystem in the southern part of the United States. Its invasion is facilitated by its ability to thrive in a wide range of abiotic conditions. Nasturtium officinale is an aquatic plant that is sensitive to relatively low amounts of pollution and is most commonly found in springs and shallow bodies of water. While A. philoxeroides tolerates organic pollution and heavy metals, N. officinale exhibits stress at low levels of pollution. We examined the effects of copper and lead on the antioxidant enzyme response of A. philoxeroides and N. officinale, which was measured using a benchtop luminometer. Alternanthera philoxeroides antioxidant enzyme production was unaffected by increasing concentrations of both copper and lead. The antioxidant enzyme response of N. officinale showed a significant increase when plants were exposed to 10 and 25 ppm lead. Endogenous peroxidase concentrations of the control plants were also compared showing that A. philoxeroides possessed a significantly higher concentration of peroxidases than N. officinale. We hypothesize that a higher endogenous peroxidase concentration may be a mechanism that hyperaccumulator plants use to tolerate inhospitable environmental conditions.