Attenuated total reflectance spectroscopy of plant leaves: a tool for ecological and botanical studies

Abstract

Summary• Attenuated total reflectance (ATR) spectra of plant leaves display complex absorption features related to organic constituents of leaf surfaces. The spectra can be recorded rapidly, both in the field and in the laboratory, without special sample preparation.• This paper explores sources of ATR spectral variation in leaves, including compositional, positional and temporal variations. Interspecific variations are also examined, including the use of ATR spectra as a tool for species identification.• Positional spectral variations generally reflected the abundance of cutin and the epicuticular wax thickness and composition. For example, leaves exposed to full sunlight commonly showed more prominent cutin-and wax-related absorption features compared with shaded leaves. Adaxial vs. abaxial leaf surfaces displayed spectral variations reflecting differences in trichome abundance and wax composition. Mature vs. young leaves showed changes in absorption band position and intensity related to cutin, polysaccharide, and possibly amorphous silica development on and near the leaf surfaces.• Provided that similar samples are compared (e.g. adaxial surfaces of mature, sun-exposed leaves) same-species individuals display practically identical ATR spectra. Using spectral matching procedures to analyze an ATR database containing 117 individuals, including 32 different tree species, 83% of the individuals were correctly identified.

Chemical–physical characterization of isolated plant cuticles subjected to low-dose γ-irradiation

“…ATR-FTIR spectroscopy is very powerful tool for the precise chemical characterization of plant cuticles (Ribero da Luz, 2007;Fernández et al, 2011) and it has been used here to investigate the chemical modifications associated to low dose γ-irradiation. Overall ATR-FTIR spectra of C, C-Ir and CNW are quite similar (see "supplementary material", Figure S1) and indicates no substantial chemical modification, however, small differences can be appreciated.…”

Leaf Area Index Retrieved From Thermal Hyperspectral Data

“…water content) at leaf level. The primary absorption features associated with water and cellulose, as important vegetation components, are only observable in the mid-wave infrared (3-5 µm, MIR) and TIR regions Gerber et al 2011;Ribeiro da Luz 2006). In addition, previously, it has been presumed that plants are opaque and featureless in the TIR region.…”

Sensing vegetation canopies in the thermal domain

“…water, polysaccharides such as cellulose) and leaf structure variables (e.g. thickness) are only discernable in the MIR and TIR domains (Fabre et al 2011b;Gerber et al 2011;Ribeiro da Luz 2006;). …”

“…For instance, Ribeiro da Luz and Crowley (2010) and Ullah et al (2012a) investigated the identification of plant species using emissivity in the TIR region. Only a few researchers opined that the TIR region contains relevant information regarding the biochemical concentration in leaves (Fabre et al 2011b;Gerber et al 2011;Ribeiro da Luz andCrowley 2007, 2010;Ullah et al 2012a). In this regard recently, a few studies focused on estimation of water content using emissivity spectra of plants at leaf level Ullah et al 2012b;Ullah et al 2014).…”

“…water, polysaccharides such as cellulose) and leaf structure parameters (e.g. thickness) are only observable in the mid-wave infrared 3-5 µm (MIR) and TIR regions (Fabre et al 2011b;Gerber et al 2011;Ribeiro da Luz 2006). In addition, different plant species show not only distinct reflectance curves in the VNIR and SWIR regions (Schmidt and Skidmore 2003) but also have distinguishable spectral features in the TIR domain (Ribeiro da Luz and Crowley 2010).…”