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Wax on, Wax off: The Contribution of Epicuticular Plant Waxes to Leaf Reflectance Spectra of Tallgrass Prairie Grasses

Presentation Date
Tuesday, December 12, 2023 at 2:10pm - Tuesday, December 12, 2023 at 6:30pm
MC - Poster Hall A-C - South



The surface of vascular plants is covered by epicuticular wax composed of a diverse array of organic compounds. While this surface wax layer plays critical roles ranging from water retention to plant defense, leaf waxes are rarely considered in spectral analysis of leaf properties. Hyperspectral imaging in the Visible to Shortwave Infrared (VSWIR; ~400-2500 nm) is an increasingly promising method for remote sensing plant functional traits, biodiversity, and ecosystem attributes. Yet, it remains largely unknown how variation in reflectance due to leaf waxes fits into these other dimensions. Here, we ask whether leaf waxes contribute to interspecific differences in leaf reflectance. We collected leaves from thirty-three species of abundant perennial prairie grasses at the Konza Prairie Biological Station, a remnant North American tallgrass prairie. For these species, we measured full VSWIR leaf spectral reflectance before and after removing adaxial and abaxial leaf waxes with an organic solvent (9:1 n-hexanes to ethyl acetate). We find that the grass leaves with and without wax were spectrally separable across many regions in the VSWIR. Using Partial Least Squares Discriminant Analysis to classify leaves as wax or no-wax, we calculate a Kappa value of 0.94 (p < 2e-16) overall accuracy of 0.97. Wax removal resulted in a mean reduction in NIR (780- 2500 nm) reflectance of 9.1%. These results suggest that the wax reflectance is a prominent component of the overall leaf spectral reflectance of these grass species. Leaf wax is detectable by spectroscopy, indicating the possibility for future remote sensing applications that might quantify waxes as a plant trait.

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