Preliminary Course.
Eco-Physiology
Photosynthesis.
Maintenance respiration
-
Maintenance respiration (Rm variable on previous page) refers to the carbon dioxide (CO2) released, or oxygen (O2)
consumed during the generation of usable energy (mainly ATP, NADPH, and NADH) and
metabolic intermediates used to:
- resynthesize compounds that undergo renewal (turnover) in the normal process of metabolism (examples are enzymatic proteins, ribonucleic acids, and membrane lipids)
- maintain chemical gradients of ions and metabolites across cellular membranes that are necessary for cellular integrity and plant health
- operate metabolic processes involved in physiological adjustment (i.e., acclimation) to a change in the plant's environment.
Maintenance respiration is essential for the biological health and growth of plants.
It is estimated that about half of the respiration carried out by terrestrial plants during their lifetime is for the support of maintenance processes.
Typically, more than half of global terrestrial plant photosynthesis (or gross primary production) is used for plant respiration, more than one quarter of global terrestrial plant photosynthesis is presumably consumed in maintenance respiration.
Modelling maintenance respiration.
Maintenance respiration is a key component of most physiologically based mathematical models of plant growth, including models of crop growth and yield and models of ecosystem primary production and carbon balance.
Maintenance respiration mainly depends on biomass and temperature.
The following model is common:
-
Rm = Coef * Dry Biomass Weight
-
Here the coefficient Coef is computed from a reference coefficient
(for instance at 25°C) and a power function.
In experiments, it has been shown that this coefficient value may double for every 10°C increase of temperature. Hence the following model:
Coef = Coef25 * Q10(t-25)/10
Setting the Q10 value to 2.0 simulates the experiment results.
Coef25 values lie typically in the range [0.01, 0.02]