Interaction of nanoparticles in the seed coat and seedling of Phaseolus vulgaris during the germination investigated by synchrotron-based techniques

Nanoecotoxicology is a growing field of science driven by the extensive use of nanomaterials in commercial products and agriculture. Their use in agriculture is to become a reality trough fertilizers and pesticides. On the other hand, little is known about possible collateral effects that of nanomaterials, and therefore they may pose a threat to human health and the environment. To shed light on these topics, one must better understand the mechanisms of interaction between nanoparticles and living beings. Seed treatment is a common practice that provides micronutrients and protection. At my Ph.D. research I investigated the effects of ZnO NP and Ag NP on the germination of Phaseolus vulgaris seeds and the interaction (uptake and biotransformation) with the seed coat. Zinc-based nanoparticles were chosen because it is a plant micronutrient, whilst Ag ones present antimicrobial activity. The common bean seed treatments and synchrotron analysis were performed at the ID21 beamline in ESRF, CENA-USP and XRF beamline in LNLS. The seed coat presents three different layers composed of macrosclereids, osteosclereids and parenchyma cells. The seeds were exposed to Ag₂S NP, Ag metallic NP, ZnO NP, AgNO₃ and ZnSO₄ in different concentrations (Ag 100 and 1000 mg L^-1 while Zn 100, 1000 and 5000 mg L^-1). After 5 days of post-treatment and germination, seed coats were recovered and cryosectioned and investigated by FTIR, μ-XRF, and μ-XANES. μ-XRF analysis under cryogenic conditions showed that most of the NP treatments remained trapped in the seed coat, while μ-XANES unraveled that depending on the composition of pristine materials they can be biotransformed. Now it is necessary to obtain more detailed XRF maps using a nanometric beam in frozen hydrated tissue samples from seed coats treated with Ag nanoparticles in lower concentrations (10-100 ppm).to obtain XANES maps to access speciation in 2D across seed coat cellular layers. To study another micronutrient such as Fe nanoparticles to compared the behavior around the seed coat interaction. It will enable us to get more detailed speciation of the NPs and identify accurately the biotransformation compartment. To improve the sample preparation methods for cryogenic analysis of seed coat and different parts of common bean seedlings such as primary roots and cotyledons to investigate the potential effects of NPs seed treatment in the seedlings.