Leaf Boundary Layer Conductance - Estimates for Gas Exchange Calculations

​As part of a series of plant gas exchange measurements I have been making in collaboration with Rolf Siegwolf and Lucas Cernusak, we have estimated boundary layer conductance in the Walz gas exchange system that we are using. As a contribution for the common good, I thought I would make those estimates available.
 
The estimates are made for a Walz 3010GWK gas exchange chamber with and without their new elbow flange. We measured conductance to water vapor as the evaporative flux from a saturated piece of filter paper cut into the shape of a poplar leaf with different fan speeds. To do so, we cut two pieces of filter paper, made a thin slit in one, and inserted the thermocouple between the two pieces in the leaf cuvette.
 
The results show that the new flange makes an overwhelming difference in removing the boundary layer and increasing conductance. There are modest differences in leaf size, but this is largely due to the difficulty of keeping the smaller leaf saturated at high fan speeds. Overall, these estimates may be lower than those made in other systems, particularly in comparison to smaller leaf cuvettes, but the result is still a very low resistance.
 
If you have questions or would like access to the raw data, please do not hesitate to contact me. 

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