Real-time CO2 uptake/emission measurements as a tool for early indication of toxicity in Lemna-tests.

Abstract

This paper presents an application of continuous monitoring of the emission and uptake rate of CO2 in Lemna toxicity test. On a real-time basis, the CO2 concentration data were collected by the Arduino platform-based respiratory activity measuring system (ResTox) and reported as CO2 concentration dynamic curves. The results of CO2 measurements demonstrated that tested metals (Co, Cu, Hg, and Cd), as well as herbicides (nicosulfuron, diquat, and tembotrione), stimulated the CO2 exchange rates at low doses, while at high doses CO2 exchange rates were inhibited. The addition of higher concentrations of clopyralid stimulated photosynthetic activity and caused a higher increase in respiration rates indicating its mode of action as auxin mimic herbicide. The results obtained underline the necessity of considering other biological endpoints like continuous measurements of gas exchange from the very beginning of exposure to toxicants. Simultaneous measurements of real-time CO2 concentrations, as the primary effect of toxicant mode of action, and processes that are supported by carbon flux, as the secondary effect or endpoint, are needed to relate actual and substrate-induced or inhibited respiration and photosynthesis to those processes. Therefore, continuous measurements of CO2 exchange rates can be implemented for the initial screening of potential toxicity to give valuable information that is needed for further examination of toxicity mechanisms and risk assessment.