Chlorophyll Fluorescence Imaging-Based Duckweed Phenotyping to Assess Acute Phytotoxic Effects

Area of Science:

• Ecotoxicology
• Plant Physiology
• Environmental Science

Background:

• Duckweeds (Lemnaceae) are standard ecotoxicology models.
• Chlorophyll fluorescence imaging offers high-throughput phytotoxicity testing.
• Diverse fluorescence parameters complicate result comparison across studies.

Purpose of the Study:

• To compare the sensitivity of various chlorophyll fluorescence parameters in *Spirodela polyrhiza* exposed to nickel, chromate, and NaCl.
• To evaluate dark- and light-adapted Photosystem II photochemistry.
• To identify optimal fluorescence endpoints for phytotoxicity assays.

Main Methods:

• Utilized *in vivo* chlorophyll fluorescence imaging on *Spirodela polyrhiza*.
• Assessed plant photochemistry in both dark- and light-adapted states.
• Exposed plants to nickel, chromate (hexavalent chromium), and sodium chloride for 72 hours.

Main Results:

• Chlorophyll fluorescence parameters exhibited divergent sensitivities to toxicants.
• Light-adapted parameters were generally more sensitive than dark-adapted ones.
• Fv/Fm was the least sensitive endpoint; Fv/Fo showed higher responsiveness.
• Toxicants induced distinct patterns in fluorescence parameters and quenching processes.
• Hormetic effects were observed at concentrations causing significant growth inhibition.

Conclusions:

• Parallel assessment of multiple chlorophyll fluorescence parameters is crucial for robust ecotoxicological studies.
• Light-adapted parameters, particularly Fv/Fo, are recommended for enhanced sensitivity in phytotoxicity assays.
• Chlorophyll fluorescence changes do not always correlate directly with growth inhibition, necessitating careful interpretation of endpoints.