Overview
EN ISO 20227:2017 (ISO 20227:2017) specifies a standardized microbiotest to assess water quality by measuring the growth inhibition of the duckweed Spirodela polyrhiza. The method is a stock culture independent microbiotest that uses germinated turions, enabling laboratories to run toxicity assays without continuous culturing. It applies to waste waters, natural waters, treated municipal effluent, industrial discharges, and pure chemicals including pesticides and plant protection products.
Key topics and technical requirements
- Test principle: Germinate turions of Spirodela polyrhiza, then expose first fronds to test samples in a multiwell format and quantify growth inhibition by image analysis.
- Test stages: Typically involves a short turion germination phase followed by a multi‑day exposure (the standard describes a 3-day germination and a 3-day toxicity test in the microbiotest workflow).
- Growth medium and preparation: Use of a defined modified Steinberg medium (stock solutions and final medium preparation are specified).
- Apparatus and format: Multiwell plates, imaging setup for area measurement, and basic lab equipment; the method is designed to be low‑resource and space‑efficient.
- Data handling: Image-based measurement of first‑frond area, calculation of growth inhibition, and reporting of results following the standard’s data‑treatment and validity criteria.
- Quality control: Includes reference chemicals, sensitivity checks, validity criteria and requirements for reporting to ensure reproducible results.
- Documentation: Test report elements, annexes on stock culturing for turion production, sensitivity data and performance examples are provided.
Applications and who uses it
- Environmental monitoring laboratories assessing effluent toxicity, receiving waters and ecological risk.
- Wastewater treatment operators and industrial facilities conducting compliance or impact testing.
- Regulatory and standardization bodies evaluating hazards of chemical formulations, pesticides and discharges.
- Environmental consultants, ecotoxicologists and research groups needing a rapid, reproducible freshwater phytotoxicity assay.
- Product developers and pesticide registrants performing environmental hazard screening.
Practical advantages
- Stock culture independent: uses stored turions with long shelf life - no continuous live culture maintenance.
- Compact and fast: minimal bench space; rapid image analysis enables high throughput.
- Sensitive and relevant: measures effects on a primary producer representative of freshwater ecosystems.
Related standards (if applicable)
- ISO 20079 and other ISO water‑quality and aquatic ecotoxicity methods are relevant complementary references for duckweed and phytotoxicity testing.