Influence of Surface Structure, Pigmentation and Particulate Matter on Plant Reflectance and Fluorescence.

Optical properties of plant leaves are relevant to evaluate their physiological state and stress effect. The main objective of this work was to study how variegation, pigment composition or reflective features modifies leaves' photophysical behavior. For this purpose, green leaves (Ficus benjamina), purple leaves (Tradescantia pallida), green leaves covered by white trichomes (Cineraria maritima) and variegated leaves (Codiaeum aucubifolium) were analyzed. Firstly, foliar surface morphology was evaluated by scanning electron microscopy. UV-vis and near-IR reflectance and transmittance spectra were obtained to calculate absorption (k) and scattering (s) coefficients. The theoretical approaches of Pile of Plates and Kubelka-Munk's theory resulted still valid for nonstandard leaves with differing surface conditions. However, frequently used spectral indices were not reliable for predicting water content, when leaves differed from conventional ones. The proportionality between the absorption factor and chromophore/pigment concentration was also lost for hairy leaves. A simplified model to describe these facts was presented here. Fluorescence spectra were recorded and corrected, due to light re-absorption. Water-optical parameter connection and pigment-optical parameter connection were thoroughly discussed. Leaf surface morphology and pigmentation have not only influenced the optical features of leaves but also played a role in the effect that particulate matter could cause on leaf photosynthesis.