The effects of short term salinity exposure on the sublethal stress response of Vallisneria americana Michx. (Hydrocharitaceae)

Abstract

Short term exposure of Vallisneria americana to elevated salinity was found to induce a stress response that could be quantified by a series of metabolic assays measuring oxidative stress, photosynthetic efficiency, and dark adapted respiration. Plant specimens exposed to elevated salinity for 24 h displayed signs of oxidative damage represented by the accumulation of reactive oxygen species (ROS) and lipid hydroperoxides in blade tissue (noted at salinities of 10 and 15, respectively). Respiratory demand nearly doubled (140 nanomoles O 2 consumed min −1 g −1) when plants were placed in a salinity of 15 for 24 h versus control specimens maintained at 0. After 1 week of exposure a significant increase in respiration and lipid hydroperoxide content was detected in plants incubated at or above a salinity of 13. In addition, effective quantum yield ( Δ F / F ′ m ) dropped significantly compared to plants maintained at a salinity below 13. These results highlight the use of cellular stress assays to monitor salt-induced sublethal responses in V. americana.