Conclusion
We quantified boundary layer conductance to heat transfer in matched
patches or leaves, with or without leaf hairs (trichomes), in five
broadleaved species, using dynamic infrared thermography. Our results
provide the first direct experimental proof for the long-standing
hypothesis that leaf hairs impede convective heat exchange between
leaves and the adjacent air. Boundary layer conductance was 2 – 39%
greater in patches or leaves without hairs than in the presence of
hairs. Leaf hair layer depth did not predict increases in boundary layer
resistance due to the presence of hairs, in contrast with prior
theoretical predictions, but these results were uncertain due to
uncertainty in the ratio of boundary layer resistance between the two
leaf surfaces in the absence of hairs. This study supports the use of
dynamic IR thermography as a viable, practical technique for studying
boundary layer conductance in real leaves.