The peroxidase response of Alternanthera philoxeroides (Alligator Weed) and Nasturtium officinale (Watercress) to heavy metal exposure.

We examined the effects of copper and lead on the antioxidant enzyme response of Alternanthera philoxeroides and Nasturtium officinale using a benchtop luminometer. Alternanthera philoxeroides is a nonnative invasive plant species that has spread throughout the wetland ecosystem in the southern part of the USA. 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. 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 concentrations of copper and lead.

Chemiluminescent examination of abiotic oxidative stress of watercress.

Watercress (Nasturtium officinale) is an aquatic plant that readily bioaccumulates heavy metals that may be found in contaminated aquatic systems. Toxic effects of contaminants on the physiological processes cause changes in oxidase enzymatic activity in watercress, which can be measured with a luminometer. The luminometer uses the reaction produced when peroxidases break down hydrogen peroxide into water and an oxygen radical. The resulting oxyradical binds to and oxidizes phenolic groups, producing a measureable luminescent reaction. Nasturtium officinale plants were exposed to 3 different concentrations of heavy metals, including lead, nickel, copper, and manganese for 24 h, 48 h, and 72 h. Aquatic exposure to the 4 heavy metals caused a significant increase in oxidative enzyme production. Fluorometric and morphometric measurements were also conducted to compare plant stress with the oxidative enzyme analyses. Fluorometric measurements performed on plants stressed by exposure to heavy metals revealed no significant decreases in photosystem II efficiency. Morphometric measurements of root length showed decreased root growth resulting from exposures to Ni, Cu, and Mn.

Chemiluminescent examination of abiotic oxidative stress of watercress.

Watercress (Nasturtium officinale) is an aquatic plant that readily bioaccumulates heavy metals that may be found in contaminated aquatic systems. Toxic effects of contaminants on the physiological processes cause changes in oxidase enzymatic activity in watercress, which can be measured using a luminometer. The luminometer uses the reaction produced when peroxidases break down hydrogen peroxide into water and an oxygen radical. The resulting oxyradical binds to and oxidizes phenolic groups producing a measureable luminescent reaction. N. officinale plants were exposed to three different concentrations of heavy metals including lead, nickel, copper, and manganese for 24, 48, and 72 hour exposures. Aquatic exposure to the four heavy metals caused a significant increase in oxidative enzyme production. Fluorometric and morphometric measurements were also conducted in order to compare plant stress to the oxidative enzyme analyses. Fluorometric measurements performed on plants stressed by exposure to heavy metals revealed no significant decreases in photosystem II efficiency. Morphometric measurements of root length showed decreased root growth resulting from exposures to nickel, copper, and manganese. Environ Toxicol Chem © 2013 SETAC.