Increased emphasis is being placed on protecting wetlands (6) and several agencies including U.S. Environmental Protection Agency and Environment Canada are beginning to require, for the registration of pesticides, data regarding toxicity of test materials to rooted aquatic vascular plants (7,8,9).

Much research is being conducted with vascular plants, both terrestrial and aquatic (10), however, protocols for phytotoxicity testing with freshwater emergent macrophytes still are not well defined.

This guide is designed to assess potential detrimental effects of water soluble chemical substances on selected surrogate species of freshwater emergent macrophytes.

This guide focuses on diminishment of chlorophyll content in leaves as the measurable endpoint, however, not all chemicals affect chlorophyll production. Dry weight can be used as the endpoint for O. sativa, however, exposure times may need to be extended to detect treatment differences. Dry weight is not a recommended endpoint for any of the test species started as rhizomes or tubers. Other endpoints, such as peroxidase activity (11) or chlorophyll fluorescence (12) could possibly be used.

This guide could be used to provide early indication of potential problems, identify hazardous substances before contamination of wetlands occurs, and establish “margins of safety” for specific chemicals within wetlands (see Guide E 1023).

This guide is not designed to replace field assessments or other aquatic testing procedures. It is designed to compliment such testing, so that a more complete assessment is possible.

1.1 This test guide is designed to give general guidance for assessing the potential phytotoxicity of water soluble test material to freshwater emergent macrophytes.

1.2 This renewal test continuously exposes selected plant species, growing in sediment, to various concentrations of test material, dissolved in a nutrient solution.

1.3 This test guide is based on the Toxic Substances Control Act (TSCA) guidelines for conducting toxicity tests with terrestrial plants (1) and is applicable to most water soluble chemicals, either individually or in formulations, commercial products, or known mixtures (see Guides E 1193 and E 1598). With slight modifications the procedure also might be used for effluents (see Guide E 1192).

1.4 Results from this toxicity test can be used to report an IC50 or NOEC (see Section 3) based on the concentration of chlorophyll extracted from the plants (see Guides D 3731 and E 1218). In some situations, it might be necessary to only test at one concentration to determine whether or not that specific concentration is toxic to the plants.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 7.