Infrared Monitoring of Dinitrotoluenes in Sunflower and Maize Roots

Abstract

Infrared microspectroscopy (IMS) is emerging as an important analytical tool for the structural analysis of biological tissue. Th is report describes the use of IMS coupled to a synchrotron source combined with principal components analysis (PCA) to monitor the fate and eff ect of dinitrotoluenes in the roots of maize and sunfl ower plants. Infrared imaging revealed that maize roots metabolized 2,4-dinitrotoluene (DNT) and 2,6-DNT. Th e DNTs and their derivative aromatic amines were predominantly associated with epidermis and xylem. Both isomers of DNT altered the structure and production of pectin and pectic polysaccharides in maize and sunfl ower plant roots. Infrared peaks diagnostic for aromatic amines were seen at the 5 mg L −1 concentrations for both DNTs in maize and sunfl ower treated tissue. However, only infrared peaks for nitro groups, not aromatic amines, were present in the maize treated at 10 mg L −1 . For sunfl ower, the 10 mg L −1 level was toxic and also produced very dark root systems making spectra diffi cult to obtain. Maize and sunfl ower seem unable to metabolize eff ectively at concentrations higher than about 5 mg L −1 DNT in hydroponic solution. Based on the results of this study, IMS combined with PCA can be an eff ective means of determining the fate and metabolism of organic contaminants in plant tissue when isotopically labeled compounds are not available.

Plant roots and spectroscopic methods – analyzing species, biomass and vitality

“…However, while Naumann et al (2010) did not find differences in species’ spectral patterns between different environments (i.e., substrate, competitive neighborhood) and root segment positions, Zuo et al (2007) divided Polygonum cuspidatum root samples from seven geographical origins in China into six classes with principal component analysis (PCA) based on IR fingerprint spectra (Xu et al, 2003). Furthermore, different spectral pattern were detected if roots were inoculated with either rhizobacteria (El Zemrany et al, 2007) or mycorrhizal fungi (Calderón et al, 2009), or treated with environmental pollutants such as benzotriazole (Dokken and Davis, 2011). Thus, because changes in chemical root composition can be caused by changes in abiotic and biotic environments and by secondary growth of roots (White et al, 2011), pure reference samples reflecting the environmental variability and the analyzed “type” of root system are needed to establish more reliable calibration spectra for each species.…”

Differential Effects of Cerium Oxide Nanoparticles on Rice, Wheat, and Barley Roots: A Fourier Transform Infrared (FT-IR) Microspectroscopy Study

“…15,16,19 It has been extensively employed in determining structural changes in plants exposed to biotic and abiotic stressors. For example, FT-IR microspectroscopy was used to investigate the macromolecular modifications in the epidermis, cortex, and xylem of sunflower (Helianthus annuus) and maize (Zea mays) roots treated with dinitrotoluenes, 20 and macromolecular changes in the root and stem tissues of Mexican palo verde (Parkinsonia aculeata) exposed to Cr. 21 Similarly, alterations in the carbohydrate chemistry of leaves due to chemical and enzymatic degradation 22 and profiling of the chemical fingerprint of the inner and outer surfaces of distinct types of plant tissues have been assessed by employing the FT-IR microspectroscopic technique.…”

Advanced in situ Spectroscopic Techniques and their Applications in Environmental Biogeochemistry: Introduction to the Special Section

“…Synchrotron radiation infrared microspectroscopy (SR‐IMS) offers the advantage that the IR spectra can provide information regarding the localization of various molecules on the basis of the distribution of characteristic functional groups. In this specific case, Dokken and Davis (2011) report that DNTs and the derivative aromatic amines mainly are found in association with lignified structures and that metabolization of DNT did not occur when plants were exposed to concentrations >5 mg L −1…”

“…The usefulness of SR is not limited to elemental speciation and distribution as it can be extended to the investigation of organic molecules. For instance, Dokken and Davis (2011) used another portion of the SR, the infrared (IR) region, to investigate the fate and behavior of dinitrotoluenes (DNTs) in plants. Synchrotron radiation infrared microspectroscopy (SR‐IMS) offers the advantage that the IR spectra can provide information regarding the localization of various molecules on the basis of the distribution of characteristic functional groups.…”