Internal conductance of Scots pine varies with vapour pressure deficit
Abstract
Leaf internal conductance is the most limiting step in the transport pathway of CO2 uptake during photosynthesis when stomata are open. This limitation is especially important in coniferous trees, which, as the major species of boreal forests, play a crucial role in the terrestrial carbon cycle. However, the environmental controls on internal conductance are poorly understood. Carbonyl sulfide (COS) is an important tracer of stomatal conductance of plants due to its shared metabolic path with carbon dioxide (CO2). Unlike CO2, COS is fully hydrated in plant's leaves by carbonic anhydrase, so there are no respiration-like emissions from the plant. Plant leaf conductance could be separated into stomatal conductance (controlling plant's uptake of CO2 and losses of water), internal conductance (reflecting a conductance to CO2 diffusion in mesophyll). All processes are important to study to understand a plant's limitations under various conditions in terms of changing climate leading to still more frequent extreme weather situations. However, unlike stomatal conductance, internal one is still understudied. We measured COS emissions from a Scots pine at Hyytiälä ecosystem research station, Finland, during a spring and summer in 2017 with branch transparent chambers, together with ancillary CO2 fluxes and meteorological measurements. Based on the CO2 daytime fluxes, we obtained overall leaf conductance, which could be separated into stomatal (from COS) and internal conductance. Continuous flux measurements enabled us to further study the environmental drivers of internal conductance, providing unique insight into the control of internal conductance under field conditions.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2019
- Bibcode:
- 2019EGUGA..21.8277F