Measuring Respiration

Of the CO2 assimilated by photosynthetic organisms, nearly half is returned to the atmosphere through maintenance and growth respiration. Mitochondrial respiration drives the productivity for both heterotrophs and autotrophs. Having accurate measures of respiration is necessary to close an ecosystem's carbon budget.

Plant respiration is measured by driving carbon assimilation to zero (typically in the dark) and quantifying the CO2 and/or O2 flux. Unlike photosynthetic carbon assimilation, there is not a currently accepted mechanistic model that adequately relates the measured gas exchange and underlying respiratory biochemistry (Amthor, 1994). Accurate empirical measurements can be made for most organisms using sensitive gas exchange techniques. Respiration rate can be impacted by environmental variables such as temperature. Understanding how organisms respond to environmental changes is important for refining projections of changing atmospheric conditions.

Amthor, J.S. 1994. Respiration and carbon assimilate use. P 221-249. In K.J. Boote et. al. (ed.) Physiology and determination of crop yield. ASA, CSSA and SSSA. Madison, WI

LI-COR Photosynthesis Systems:

The LI-6400XT and LI-6800 Portable Photosynthesis Systems are compact, rugged, field portable instruments able to provide researchers with detailed information on plant responses including respiration. The LI-6800 is our newest system, featuring a touch-screen interface and improvements in gas analyzer precision, better control over chamber conditions, and more.

LI-8100A Automated Soil CO2 Flux System

  • Measures CO2 exchange from soils
  • Multiplexed configuration available for larger sampling area
  • Useful for survey or long-term measurements

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