Long-term effects of silver nanoparticles and mineral nutrition components on the photosynthetic processes, chloroplast ultrastructure and productivity of Solanum lycopersicum plants

The effects of silver nanoparticles (AgNPs), both alone and in combination with mineral nutrients, on the growth and photosynthesis of Solanum lycopersicum plants during ontogeny were studied. The experiment involved weekly applications of 10 μmol of AgNPs for 15 weeks in a greenhouse over a summer period. A comprehensive characterization of the AgNPs was performed via TEM, ESI/EELS, and zeta potential measurements before and throughout the experiment. The activity of PSII, stomatal conductivity, photosynthesis, transpiration and respiration rates were measured, and the photosynthetic pigments, chloroplast ultrastructure, and dry and fresh masses of leaves, roots, and fruits were assessed. The results indicated that combining AgNPs with mineral nutrients increased PSII activity and the photosynthesis rate and altered the chloroplast ultrastructure. However, the use of mineral nutrients or AgNPs alone did not induce these changes. Atomic absorption spectrometry detected AgNPs in all the plant organs except the fruits. The highest fruit yield was associated with Veni Prisma®, a commercial product containing colloidal silver, which also caused desynchronized fruit maturation. This study hypothesizes that the synergistic effect of AgNPs and mineral nutrients enhances silver accumulation in chloroplasts, improving light utilization and photosynthetic efficiency, particularly under low light, thus increasing fruit quantity and dry mass. Conversely, long-term use of AgNPs alone was accompanied by silver accumulation outside the chloroplasts and did not lead to increased photosynthesis or an increase in fresh fruit mass.