Abstract
Terrestrial plants are ideal sentinels of environmental pollution, due to their sedentary nature, abundance and sensitivity to atmospheric changes. However, reliable and sensitive biomarkers of exposure have hitherto been difficult to characterise. Biospectroscopy offers a novel approach to the derivation of biomarkers in the form of discrete molecular alterations detectable within a biochemical fingerprint. We investigated the application of this approach for the identification of biomarkers for pollution exposure using the common sycamore (Acer pseudoplatanus) as a sentinel species. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to interrogate leaf tissue collected from three sites exposed to different levels of vehicle exhaust emissions. Following multivariate analysis of acquired spectra, significant biochemical alterations were detected between comparable leaves from different sites that may constitute putative biomarkers for pollution-induced stress. These included differences in carbohydrate and nucleic acid conformations, which may be indicative of sub-lethal exposure effects. We also observed several corresponding spectral alterations in both the leaves of A. pseudoplatanus exposed to ozone pollution under controlled environmental conditions and in leaves infected with the fungal pathogen Rhytisma acerinum, indicating that some stress-induced changes are conserved between different stress signatures. These similarities may be indicative of stress-induced reactive oxygen species (ROS) generation, although further work is needed to verify the precise identity of infrared biomarkers and to identify those that are specific to pollution exposure. Taken together, our data clearly demonstrate that biospectroscopy presents an effective toolkit for the utilisation of higher plants, such as A. pseudoplatanus, as sentinels of environmental pollution.
Highlights
The advantages of using higher plants as sentinels for environmental pollution are well known.[8,9] Firstly, as sedentary organisms, they allow easy comparison between set geographical locations
The pseudospectra associated with O3 and biotic stress appears to possess analogous peaks to those associated with terpenes (ROS scavengers) in leaves from polluted sites, Sites 2 and 3 (e.g., 1373 cm−1 in both model stresses)
These common alterations may result from oxidative damage within leaves, as this is a common mode of action of air pollutants and is a consequence of pathogen infection via the oxidative burst defence mechanism
Summary
The advantages of using higher plants as sentinels for environmental pollution are well known.[8,9] Firstly, as sedentary organisms, they allow easy comparison between set geographical locations. Plant biochemistry is fundamentally similar to that of animals in aspects relevant to toxic exposure, including DNA organisation and repair mechanisms, and antioxidant activity.[10] Plant cells can be exposed to air pollutants either directly via leaf stomata, or indirectly via root uptake of pollutants deposited in the soil. Adverse effects on plants can be induced by a variety of air pollutants, among which ozone (O3) is considered to be the most damaging. O3 causes oxidative damage to cell components via the formation of reactive oxygen species (ROS),[11] which are generated by exposure to heavy metals.[12] Other adverse effects of air 2896 | Analyst, 2016, 141, 2896–2903
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