Plant Physiology & Development
Respiration, Temperature & Carbon Cost
Respiration supplies usable energy and metabolic intermediates by consuming stored carbon. Temperature strongly affects respiration rate within biological limits, so warm conditions can increase carbon costs even when photosynthetic light is unchanged.
Key concepts
- Respiration occurs in living tissues day and night
- Higher temperature often increases metabolic reaction rates until stress or damage alters the response
- Night temperature can influence carbon balance independently of daytime PPFD
- Roots, stems, leaves, flowers, and growing tissues all have respiratory costs
- Net biomass gain reflects carbon captured minus carbon used for respiration and other losses
What to measure or observe
- Record day and night temperatures separately
- Track growth rate during sustained warm-night periods
- Compare root-zone temperature with canopy temperature
- Relate temperature shifts to light availability and plant stage
- Use controlled comparisons rather than assuming a single optimal night temperature
Common mistakes
- Treating nighttime temperature as irrelevant because photosynthesis stops
- Assuming warmer always means faster productive growth
- Ignoring root respiration and root-zone temperature
- Comparing biomass without considering temperature history
- Using respiration concepts to justify extreme temperature swings
Visuals this lesson still needs
- Photosynthesis-versus-respiration carbon budget
- Day/night temperature timeline
- Whole-plant respiration map
- Temperature and net-carbon-balance diagram