DEVELOPMENT OF A PLANT BIOASSAY TO ASSESS TOXICITY OF CHEMICAL STRESSORS TO EMERGENT MACROPHYTES

摘要

A static renewal bioassay has been proposed to evaluate the effects of chemical stressors on the growth of emergent macrophytes. Bioassay methods were developed using Oryza sativa L. (domestic rice) as the test species and boron as the test compound. After culturing O. sativa in a natural sediment for 2 weeks, the plants were continuously exposed to various concentrations of boron dissolved in the dilution water. At the end of the exposure period the plants were evaluated. Endpoints included visual observations, dry weight, residue, and chlorophyll concentration in the leaf tissue. Dose-response relationships were established for each endpoint; however, dry weight appears to be the least sensitive endpoint. Exposure duration also significantly influenced toxic values. The bioassay procedure was then used to screen several other emergent macrophytes for toxicity to boron. Visual observations and residue indicated treatment differences for each of these species; however, dry weight and chlorophyll concentration did not confirm the differences. Oryza sativa plants exposed to water naturally contaminated with boron accumulated similar concentrations of boron in their leaf tissue as plants exposed to laboratory-prepared solutions of boron. Based on the data presented here, this bioassay appears to be useful in evaluating the potential toxicity of chemical stressors to emergent macrophytes.