Quantitative monitoring of paramagnetic contrast agents and their allocation in plant tissues via DCE-MRI

BACKGROUND

Studying dynamic processes in living organisms with MRI is one of the most promising research areas. The use of paramagnetic compounds as contrast agents (CA), has proven key to such studies, but so far, the lack of appropriate techniques limits the application of CA-technologies in experimental plant biology. The presented proof-of-principle aims to support method and knowledge transfer from medical research to plant science.

RESULTS

In this study, we designed and tested a new approach for plant Dynamic Contrast Enhanced Magnetic Resonance Imaging (pDCE-MRI). The new approach has been applied in situ to a cereal crop (Hordeum vulgare). The pDCE-MRI allows non-invasive investigation of CA allocation within plant tissues. In our experiments, gadolinium-DTPA, the most commonly used contrast agent in medical MRI, was employed. By acquiring dynamic T₁-maps, a new approach visualizes an alteration of a tissue-specific MRI parameter T₁ (longitudinal relaxation time) in response to the CA. Both, the measurement of local CA concentration and the monitoring of translocation in low velocity ranges (cm/h) was possible using this CA-enhanced method.

CONCLUSIONS

A novel pDCE-MRI method is presented for non-invasive investigation of paramagnetic CA allocation in living plants. The temporal resolution of the T₁-mapping has been significantly improved to enable the dynamic in vivo analysis of transport processes at low-velocity ranges, which are common in plants. The newly developed procedure allows to identify vascular regions and to estimate their involvement in CA allocation. Therefore, the presented technique opens a perspective for further development of CA-aided MRI experiments in plant biology.

Towards the revision of the drinking water directive 98/83/EC. Development of a direct injection ion chromatographic-tandem mass spectrometric method for the monitoring of fifteen common and emerging disinfection by-products along the drinking water supply chain

According to the recent proposal released by the European Commission for the revision of the 98/83/EC Directive, water suppliers will be requested to monitor the nine bromine- and chlorine congeners of haloacetic acids, HAAs, as well as the oxyhalides chlorite and chlorate, as disinfection by-products (DBPs) originated during the potabilization process. In this work, we propose a direct-injection method based on ion chromatography and mass spectrometric detection for the determination of the mentioned DBPs as well as bromate (already included in the 98/83/EC), implemented also for the following emerging HAAs monoiodo-, chloroiodo- and diiodo-acetic acids. The method was optimized to include the fifteen compounds in the same analytical run, tuning the chromatographic (column and gradient) and detection conditions (suppression current, transitions, RF lens settings and collision energies). To avoid matrix effect and to manage the instrumental conditions, optimization was performed directly in drinking water matrix. The method quantitation limits satisfy the new limits imposed by the future directive and range from 0.08 μg/L (monobromoacetic acid) to 0.34 μg/L (trichloroacetic acid). The performance of the method was checked along different strategic sampling points of three potabilization plants serving the city of Turin (Italy), including intermediate treatments and finished waters. Recovery was checked according to the ±30% limit of acceptability set by EPA regulations. The effect of disproportionate concentrations of chlorite and chlorate in respect to HAAs on HAA signals was studied; this aspect is underestimated in literature. The method is routinely applied by the potabilization plant of the city of Turin to confirm the effectiveness of all control measures in abstraction, treatment, distribution and storage. This study represents the first example in Italy of development and use of a cutting-edge technique for HAAs analysis along the potabilization processes.

Endemic plants of Crete in electronic trade and wildlife tourism: current patterns and implications for conservation

Background

The island of Crete is a biodiversity hotspot having 223 endemic vascular taxa (species and subspecies) as a result of its long isolation and the wide range of habitats it includes. We explore trends and patterns in the electronic trade of these unique genetic resources and in their involvement in wildlife tourism, the ways these two activities are performed and the associated potential threats on the plants' wild populations, and we also identify priority taxa requiring special attention. The main part of the study was conducted in 2016-2017 using English as a search language; an additional search was conducted in 2019 using German and French.

Results

We found e-commerce for 28 (13%) endemic taxa. These are traded by 65 nurseries from 14 countries, the UK primarily. Among the traded plants, 16 face extinction risk and/or are under protection status. Prices vary largely for the same taxon and form of sale. Lamiaceae is the family with the highest number of e-traded taxa, Tulipa bakeri is the most traded species, and the living plant is the commonest form of sale. Thirty-seven endemic taxa are advertised in the websites of travel agencies involved in wildlife tourism. Tulipa doerfleri is the most frequently encountered taxon in these websites, whereas Lamiaceae, Liliaceae and Orchidaceae are similarly represented. The additional search showed a very rapid increase in the e-trade of the Cretan endemis.

Conclusion

The two examined markets are similar in that geophytes play a prominent role and Lamiaceae rank first among the represented plant families, but differ in several aspects: only 22.6% of the taxa detected are common in both, obedience to rules exhibited by travel agencies is not usually the case with nurseries, and potential threats to wild populations are estimated as considerably higher for the traded plants. Sixteen endemic taxa of Crete were identified as requiring special attention.

Effect of arsenic on reflectance spectra and chlorophyll fluorescence of aquatic plants

Arsenic pollution of groundwater is a serious problem in many regions of Latin America that causes severe risks to human health. As a consequence, non-destructive monitoring methodologies, sensitive to arsenic presence in the environment and able to perform a rapid screening of large polluted areas, are highly sought-after. Both chlorophyll - a fluorescence and reflectance of aquatic plants may be potential indicators to sense toxicity in water media. In this work, the effects of arsenic on the optical and photophysical properties of leaves of different aquatic plants (Vallisneria gigantea, Azolla filiculoides and Lemna minor) were evaluated. Reflectance spectra were recorded for the plant leaves from 300 to 2400 nm. The spectral distribution of the fluorescence was also studied and corrected for light re-absorption processes. Photosynthetic parameters (Fv/Fm and ΦPSII) were additionally calculated from the variable chlorophyll fluorescence recorded with a pulse amplitude modulated fluorometer. Fluorescence and reflectance properties for V. gigantea and A. filiculoides were sensitive to arsenic presence in contrast to the behaviour of L. minor. Observed changes in fluorescence spectra could be interpreted in terms of preferential damage in photosystem II. The quantum efficiency of photosystem II for the first two species was also affected, decreasing upon arsenic treatment. As a result of this research, V. gigantea and A. filiculoides were proposed as bioindicators of arsenic occurrence in aquatic media.