Metabolic activities produce the required energy for biochemical processes in living tissues. In plants, metabolic activity has commonly been assessed by measuring the rate of CO2 evolution or O2 consumption in the dark (dark respiration). However, these measures may not reflect the total metabolic rate accurately because some intermediates of respiratory carbon metabolism can be diverted into synthetic reactions and never appear as CO2 , and the energy use efficiency and temperature dependency of different synthetic pathways using respiratory products varies [1,2]. A more accurate assessment of total metabolic activity and respiration in plants can be made through measuring tissue’s metabolic heat production (Rq), which reflects total metabolism with an emphasis on the oxidative reactions. This makes Rq a more general and informative measure of respiration rate than is CO2 production or O2 consumption rate [3]. Measures of Rq per unit of CO2 evolution or O2 consumption (Calorespirometry) can then be used to detect thermodynamic efficiency of metabolic reactions and quantify catabolic and anabolic components of respiration and their ratio to determine if a plant is experiencing favorable conditions and growing or if it is stressed and in decline. If the efficiency of metabolic activity is assumed to be homogeneous within a plant species, then under optimum environmental conditions when resources (e.g., light, temperature, CO2 concentration, moisture, nutrients) are not limiting growth, Rq should indicate the sink activity in converting photosynthate to structural components or realized growth, and thus, differential growth potential of different genotypes within a species [1,4].

Calorespiromerty has been used successfully in a number of fields such as entomology [5] but its use in plant sciences and main stream plant ecophysiology journals has been limited compared to the use of gas exchange measurements. Calorespirometry is a promising method that can be used in many different fields of plant, soil, and animal sciences. For instance, it can be used in plant sciences to measure metabolic rate in leaf, stem, and root tissues to test hypotheses regarding determinants of growth potential, availability of the source (CO2 , light, nutrients) versus activity of the sink, genotype screening, stress (air pollution, temperature, cold, water, etc.) indicator (inefficient respiration), seed quality, etc. The Calorespirometry theory and methodology are thoroughly discussed by Hansen et al. and Wadsö, Hansen [6,7]

Momen B (2018) Calorespirometry: A Promising Method for Plant Ecophysiology Research. JSM Environ Sci Ecol 6(1): 1058.

1. Smith BN, Walker JL, Stone RL, Jones AR, Hansen LD. Temperaturedependent respiration-growth relations in ancestral maize cultivars. USDA Forest Service Proceedings. 2000; 276-279.

2. Hansen LD, Criddle RS, Smith BN. Calorespirometry in Plant Biology. In: Lambers H, Ribas-Carbo M. Plant Respiration. Advances in Photosynthesis and Respiration. 2005.

3. Criddle RS, Breidenbach RW, Lewis EA, Eatough DJ, Hansen LD. Effects of temperature and oxygen depletion on metabolic rates of tomato and carrot cell-cultures and cuttings measured by calorimetry. Plant Cell Envir. 1988; 11: 695-701.

4. Criddle RS, Anekonda TS, Tong S, Church JN, Ledig FT, Hansen LD. Effects of climate on growth traits of river red gum are determined by respiration parameters. Aust J Plant Physiol. 2000; 27: 435-443.

5. Zhang H, Liu J, Li CR, Momen B, Kohanski RA, Pick L. Deletion of Drosophila insulin-like peptides causes growth defects and metaboloic abnormalities. Proc Natl Acad Sci. 2009; 106: 19617-19622.

6. Hansen LD, Macfarlane C, McKinnon N, Smith B, Criddle RS. Use of calorespirometric ratios, heat per CO2 and heat per O2 , to quantify metabolic paths and energetics of growing cells. Thermochim Acta. 2004; 422: 55-61.

7. Wadso L, Hansen LD. Calorespirometry of terrestrial organisms and ecosystems. Methods. 2015; 76: 11-19.