ESEM-EDS: In vivo characterization of the Ni hyperaccumulator Noccaea caerulescens

Environmental scanning electron microscopy (ESEM) permits to analyze samples in their native-hydratedstate, allowing a broad spectrum of biological applications. In this study, ESEM equipped with energydispersive X-ray spectrometer (EDS) was used as a fast method to analyze tissue morphology and toinvestigate metal distribution in the Ni hyperaccumulator Noccaea caerulescens, an established model tostudy the adaptation of plants to metalliferous soils. The low vacuum and wet mode operative conditionsrequired the proper choice of experimental parameters both for morphological and compositional char-acterization of plant tissues. The calibration strategy for semi-quantitative analysis involved the use ofNi fortified agar as standard and signal normalization respect to endogenous carbon, chosen as internalstandard. The obtained results are in accordance with present literature, showing a preferential Ni dis-tribution in the epidermal cells respect to near the stomata for leaves and in the cotyledon epidermidisrespect to cotyledon parenchyma area for seeds. Thanks to the absence of any time consuming sampletreatment steps, ESEM-EDS technique can be proposed as valid strategy for in vivo high-throughput anal-ysis of plant tissues and for a rapid screening and identification of other hyperaccumulator plants in aselected contaminated area.