Iron Availability for Micro-Tom Tomatoes via Nanoparticles: Implications for the Antioxidant System and Carbon Metabolism

Solanum lycopersicum converts Fe3+ into Fe2+, the form absorbed by plants. The Fe2+ present in the growth medium can be absorbed in excess by the plants, causing phytotoxicity. Magnetite has an isocratic balance of Fe3+/Fe2+, which enables the release of Fe2+ in the culture medium. The literature reports that high availability of Fe2+ can cause oxidative damage and a reduction in dry mass, whereas the application of maghemite nanoparticles, which release only Fe3+, can promote an increase in biomass. Thus, we investigated the influence of iron oxides (magnetite and maghemite) on photosynthesis, leaf carbohydrate profile and the enzymatic antioxidant system of Solanum lycopersicum “cv Micro-Tom”. Our results indicated that application of iron oxide nanoparticles provided sufficient iron to reverse the element’s deficiency, restoring the photochemical apparatus. However, the supply of magnetite resulted in reduced root dry mass, an accumulation of reducing sugars, and increased antioxidant enzyme activity. Maghemite may have contributed to a greater allocation of photoassimilates to reproductive organs, such as flowers, which showed a higher percentage distribution of dry mass, indicating its potential for use in plant cultivation.