Year: 2025
Type: article
Abstract: A parsimonious model based on Dalton's law reveals substomatal cavities to be dilute in oxygen (O 2 ), despite photosynthetic O 2 production. Transpiration elevates the partial pressure of water vapour but counteractively depresses the partial pressures of dry air's components – proportionally including O 2 – preserving cavity pressurization that is negligible as regards air composition. Suppression of O 2 by humidification overwhelms photosynthetic enrichment, reducing the O 2 molar fraction inside cool or warm leaves by hundreds or thousands of parts per million. This elucidates the mechanisms that realize O 2 transport: diffusion cannot account for up-gradient conveyance of O 2 from dilute cavities through stomata to the more aerobic atmosphere. Rather, leaf O 2 emissions depend on non-diffusive transport via mass flow forced by cavity pressurization, which is not negligible in the context of dynamics. Non-diffusive O 2 expulsion overcomes massive inward O 2 diffusion to force net O 2 emission. At very high leaf temperatures, mass flow also influences transport of water vapour and carbon dioxide, physically decoupling their exchanges and reducing water-use efficiency, independently of stomatal regulation.
Source: Biogeosciences
Author: Andrew S. Kowalski
Institution: Universidad de Granada
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,628
OpenAlex ID: W4407419184