Leaf boundary layer conductance: the final frontier for diffusion

Leaf-boundary-layer conductance (gb) represents the ease of diffusion through the air layer formed along the leaf surface due to reduced velocity and is mainly influenced by air speed. Under low air speed (e.g. within a plant canopy), gb is an important limiting factor on energy budgets, transpiration and photosynthesis that can be more important than stomatal conductance (gsw) (Kimura et al., 2016; 2020). Methods to measure gb are increasingly needed to improve air mixing in greenhouses and vertical farms, and to derive gsw from thermal or gravimetric measurements used for example in phenotyping platforms. Different techniques exist to measure gb (Brenner & Jarvis, 1995; Stokes et al., 2006) but are not widely used due to technical limitations or because of their reduced reliability under fluctuating environmental conditions. Easy to use and affordable sensors are required to map and monitor the effect of air mixing on plant growth and development in indoor farms.

In this project, you will work on a newly develop sensor to measure gb and compare the results with other methods described in the literature. Once the sensor has been tested and validated, it will be used to map the air mixing in a greenhouse. A diffusional model will then be used to predict the potential limitations of transpiration and photosynthesis that leaves can experience.


Used skills

  • Thermal energy balance
  • Gas diffusion
  • Data analysis

References

Brenner, A.J. and Jarvis, P.G., 1995. A heated leaf replica technique for determination of leaf boundary layer conductance in the field. Agricultural and Forest Meteorology, 72(3-4), pp.261-275.

Kimura, K., Yasutake, D., Miyoshi, Y., Yamanami, A., Daiou, K., Ueno, H. and Kitano, M., 2016. Leaf boundary layer conductance in a tomato canopy under the convective effect of circulating fans in a greenhouse heated by an air duct heater. Environmental Control in Biology, 54(4), pp.171-176.

Kimura, K., Yasutake, D., Yamanami, A. and Kitano, M., 2020. Spatial examination of leaf-boundary-layer conductance using artificial leaves for assessment of light airflow within a plant canopy under different controlled greenhouse conditions. Agricultural and Forest Meteorology, 280, p.107773.

Stokes, V.J., Morecroft, M.D. and Morison, J.I., 2006. Boundary layer conductance for contrasting leaf shapes in a deciduous broadleaved forest canopy. Agricultural and Forest Meteorology, 139(1-2), pp.40-54.


Interested in doing a BSc or MSc thesis at HPP? Please contact the HPP student coordinator Katharina Hanika.