TL;DR: Duckweed is a fast-growing aquatic model for plant biology, ecotoxicology and environmental monitoring. The EVOS FL Auto 2 automated fluorescence microscope is well suited to multi-well duckweed assays because it can capture transmitted-light and fluorescence images across plates on a scheduled timetable, then export quantifiable morphology data. It is the predecessor platform to the EVOS M7000 line.
Why duckweed matters in UK labs
Duckweed species such as Lemna minor and Spirodela polyrhiza are among the smallest and fastest-growing flowering plants. In UK research they are used for:
- Plant biology: studying growth, development and circadian rhythms under controlled conditions.
- Ecotoxicology: detecting herbicide, heavy metal and pharmaceutical contamination in water.
- Phytoremediation: monitoring nutrient and pollutant uptake from wastewater.
- Biofuel and food research: selecting high-yield strains by measuring biomass accumulation.
- Education: teaching plant physiology and microscopy in schools and universities.
Because duckweed floats and grows in liquid medium, it fits naturally into multi-well plate formats. This makes it ideal for automated imaging platforms that can scan many wells without manual handling.
What duckweed imaging needs
- Low magnification overview: whole-frond and colony imaging at 2×–10×.
- Transmitted-light contrast: brightfield or phase to see frond boundaries and root structure.
- Fluorescence capability: chlorophyll autofluorescence and GFP/reporter detection.
- Plate scanning: reliable stage movement across 6-, 24-, 48- or 96-well plates.
- Time-lapse scheduling: capturing growth over hours or days inside an environmentally controlled chamber.
- Image analysis: measuring frond number, area, root length and fluorescence intensity.
Benefits of the EVOS FL Auto 2 for duckweed
The EVOS FL Auto 2 is an automated inverted fluorescence imaging system. For UK duckweed labs its main advantages are:
- Plate-based automation: scan a full multi-well plate unattended, capturing consistent fields per well.
- Onstage incubator option: maintain temperature, humidity and CO₂ for multi-day growth assays.
- LED fluorescence channels: stable excitation for chlorophyll, GFP and common viability dyes.
- Integrated software: acquire, annotate and export images without a separate analysis workstation.
- Compact footprint: fits on a standard lab bench, unlike larger high-content screening systems.
- Quantitative output: image sequences can be fed into segmentation pipelines for frond counting and area measurement.
These features make the FL Auto 2 a practical bridge between low-throughput stereomicroscopy and full high-content screening. Researchers who establish duckweed assays on the FL Auto 2 can later move similar workflows to the newer EVOS M7000 platform.
Published duckweed imaging examples
Automated duckweed imaging has been described in the peer-reviewed literature. Cox et al. (2022) published a high-throughput pipeline for duckweed growth and development in Plant Direct, using transmitted-light and fluorescence imaging to track frond area and root length over time (PMC9510441). More recently, Subbaraman et al. (2024) described “The Duckbot,” a system for automated imaging and manipulation of duckweed in PLoS One. Both studies show that plant phenotyping benefits from the same automated imaging principles used in cell culture.
For cell-level and molecular imaging, Klimaj & Munoz (2020) described a high-throughput imaging and quantification pipeline for the EVOS platform in PLoS One (PMC7406032), demonstrating how automated EVOS imaging can be integrated with analysis scripts for reproducible phenotyping.
Typical FL Auto 2 duckweed workflow
- Culture duckweed axenically in liquid medium.
- Transfer fronds to multi-well plates with treatment or control media.
- Place the plate on the FL Auto 2 stage with an onstage incubator if needed.
- Define scan positions and channels: brightfield for morphology, chlorophyll fluorescence for viability.
- Run a time-lapse schedule: image every 6–24 hours for several days.
- Export images and run segmentation to extract frond count, area and root length.
- Plot growth curves and compare treatments statistically.
Why the FL Auto 2 is still relevant
Although the EVOS M7000 is the current-generation platform, the FL Auto 2 remains a capable workhorse in UK labs. It uses the same core inverted optics, LED illumination and multi-well scanning concept. Labs that already own an FL Auto 2 can continue running duckweed, cell culture and small-organism assays without immediate replacement. The main upgrade path to the M7000 adds faster automation, improved software and newer environmental control options.
Frequently asked questions
Why use the EVOS FL Auto 2 for duckweed imaging?
It automates multi-well plate scanning, supports time-lapse growth assays, captures LED fluorescence and exports quantitative images that feed frond-counting and area-measurement pipelines.
Can the FL Auto 2 still be useful now that the EVOS M7000 exists?
Yes. It shares the same inverted optics, LED illumination and multi-well scanning concept. Existing FL Auto 2 systems remain capable for duckweed, cell culture and small-organism assays.
What duckweed species are usually imaged?
Common models include Lemna minor, Spirodela polyrhiza and Wolffia globosa (Mankai). Each has different size, growth rate and research applications.
What fluorescence channels are useful for duckweed?
Brightfield for morphology, chlorophyll autofluorescence for viability and health, and GFP or common viability dyes for transgenic or stress assays.
Where can I find published duckweed imaging methods?
Cox et al. (2022, Plant Direct), Subbaraman et al. (2024, PLoS One) and Klimaj & Munoz (2020, PLoS One) all describe automated duckweed or EVOS imaging workflows.