Leaf Optics:

Light absorption, photosynthesis, and hydraulics

Light absorption within the leaf not only drives the photosynthetic uptake of CO2, it generates internal temperature gradients that control transpiration rates. Despite its importance for natural and agricultural systems, our understanding of the physical interaction between light and leaves, or leaf optics, is quite abstract. Along with intensity, light is defined by its directional and spectral qualities. When leaves intercept light they act as a filter, lowering its intensity, changing its direction, and selectively removing bands of color. I am interested in understanding how the diverse range of leaf geometries that exist across the plant kingdom have geometrically and biochemically evolved to manipulate light. To do this, I use a combination of biophysical modeling, leaf optical instrumentation, gas exchange systems, and fluorescence/X-ray microscopy. In one recent study, we investigated how the directional quality of light (i.e. diffuse versus direct) spatially affects internal CO2 transport, and ultimately photosynthesis within sun and shade leaves (Earles et al., 2017). In another project, we are examining how the spectral quality of light affects the sites of absorption and photosynthesis within sun and shade leaves. Further, the geometric models hosted in the 3D Leaf Atlas will provide the opportunity to link our biophysical modeling approach to realistic 3D leaf anatomies across the plant kingdom.


relevant publications

Earles, J.M., Théroux-Rancourt, G., Gilbert, M.E., McElrone, A. and Brodersen, C. (2017). Excess diffuse light absorption in upper mesophyll limits CO2 drawdown and depresses photosynthesis. Plant Physiology, 174: 1082-1096.



Craig Brodersen – Yale University
Matthew Gilbert – University of California, Davis
Andrew McElrone – USDA Agricultural Research Service
Guilluame Théroux-Rancourt – University of California, Davis