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.