Abstract Detail

Physiology

Hupp, Jason R. [1], McCoy, Johnathan I. E.  [2], Lynch, Douglas J.  [2], Johnson, Mark A.  [2].

Reducing carbon assimilation measurement uncertainty from aqueous samples in open flow-through gas exchange systems.

Open flow-through, or steady-state, gas exchange systems designed to measure carbon assimilation and transpiration of leaves are optimized for the range of carbon dioxide and water vapor mole fraction differentials observed from vascular plants. For these measurements, the water vapor concentration differentials can be between three and four orders of magnitude larger than those of carbon dioxide. The impact of uncertainties on the assimilation measurement due to water vapor at this range of disparity is relatively small. The gas analyzers used in gas exchange systems often have inherent cross sensitivity between the carbon dioxide and water vapor measurements, and non-linearity in their response to concentration.  Carbon dioxide assimilation uncertainty arises from the imperfect analyzer-specific cross sensitivity correction, imperfect analyzer cross calibrations, as well as a physical correction for water vapor dilution of carbon dioxide. As the disparity between the carbon dioxide and water vapor differentials increases, the impact of these uncertainties on the measurement becomes more significant. In cases where the disparity exceeds four orders of magnitude, as is traditionally the case for aqueous or water saturated samples, the magnitude of the uncertainty may exceed that of the carbon dioxide differential being measured. Here we describe a modification to an open flow-through gas exchange system and a corresponding chamber design that allows for measurement of carbon assimilation and chlorophyll fluorescence in aqueous or water saturated samples, limiting uncertainties in carbon dioxide measurements due to water vapor.  The resulting system provides a limit of resolution on the carbon dioxide differential approaching 0.1 mmol mol^-1. Data will be presented demonstrating system performance and measurement of carbon assimilation from unicellular algae suspensions.

1 - LI-COR, 4647 Superior St., Lincoln, NE, 68504.0, United States
2 - LI-COR Biosciences, 4647 Superior St, Lincoln, NE, 68504, United States

Keywords:
carbon assimilation
gas exchange
aquatic photosynthesis
algae.

Presentation Type: Oral Paper
Session: PHYS2, Physiology II
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 3:15 PM
Number: PHYS2002
Abstract ID:94
Candidate for Awards:None