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

The following LI-COR Analyzers can be used to Study Respiration

LI-6400XT Portable Photosynthesis System

The LI-6400XT system is a compact, rugged, field portable instrument able to provide researchers with detailed information on plant responses such as CO₂ assimilation rates, stomatal conductance, intercellular CO₂ concentrations, carboxylation and light use efficiencies, and CO₂ and light compensation points.

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