Relationship Between Nanoparticles and Higher Plants

The study of relationship between vascular plants and nanoparticles was subdivided in two branches, in particular the first part of the research was focused on the investigation the plants capacity to synthetize nanoparticles (NPs) inside their tissues and which are the principal molecules involved in the process. Subsequently the principal aim of the research was focused on the study of possible toxic effects caused by the NPs when they enter in contact with the plants during their first development stages and along their entire life cycle. In order to investigate the plant capacity to synthetize NPs B. juncea, M. sativa and F. rubra plants were exposed for 24 hours in a hydroponic system to a solution of silver nitrate (AgNO3) at 1000 ppm. All three plant species show high uptake and translocation of Ag. The ultrastructural analyses and microanalyses of electron dense aggregates present in roots stems and leaves in all three plant species confirm the presence of AgNPs and for the first time was confirmed in F. rubra. The content of reducing sugars and antioxidant substances analyzed were quite different between species thus suggesting it is unlikely that a single substance is responsible for this process. The focus of experiments move to the investigation of possible toxic effects caused by the interaction of NPs with plants during their first development stages. For this purpose H. vulgare seedlings were exposed to increasing concentration of cerium (Ce) and titanium (Ti) NPs for 24 hours in order to check the possible genotoxic effects and H. vulgare seeds for 7 days for testing the possible phytotoxic effects. Difference between treated plants with CeNPs and controls were observed in RAPD band pattern and a reduction in the in cell division, while the TiNPs resulted ineffective. The phytotoxic effects were checked at cellular level by monitoring the oxidative stress in term of reactive oxygen species (ROS) generation and ATP content. Again the CeNPs result to have an effect on these parameters while the TiNPs resulted ineffective. The materials were used also for check the NPs uptake and their translocation in the seedling tissues. The NPs uptake were confirmed at root level for both NPs whereas the NPs translocation weren’t confirmed but only the elements. The toxic effects of NPs were checked along the entire plant life cycle, for this purpose H. vulgare plants were grown to physiological maturity in soil enriched with either Ce NPs or TiNPs at increasing concentration and their combination. The growth cycle of CeNPs and TiNPs plants was about 10 days longer than the controls. In CeNPs treated plants the number of tillers, leaf area and the number of spikes per plant were reduced whereas TiNPs stimulated plant growth and compensated for the adverse effects of nCeO2. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline TiNPs aggregates were detected within the leaf tissues whereas CeNPs was not present in the form of nanoclusters. The kernels obtained from the previous experiment were used to check if the treatment have got some effects on their nutritional quality. For this purpose the mineral nutrients, amylose, β-glucan, amino acid and crude protein (CP) concentrations in H. vulgare kernels were measured. Ce and Ti accumulation were not enhanced by MeNPs trereatments. However, CeNPs and TiNPs impacted the nutritional quality of H. vulgare kernels in contrasting ways. Both MeNPs reduced amylose and increased amino acid and CP content. Potassium and S were both negatively impacted by MeNPs, while B only under at lower concentration of CeNPs. On the contrary Zn and Mn concentrations were improved under lower concentration TiNPs and Ca at both nTiO2 treatments.