Nanocondicionamento com óxido de zinco em sementes de tomate: análise de imagens e qualidade fisiológica em resposta a condições de estresse

Abstract

The physiological quality of seeds is fundamental for the initial establishment of crops, especially in species sensitive to environmental stresses, such as tomato. Physiological conditioning (priming) and the use of nanoparticles have been explored as strategies to enhance vigor and stress tolerance. This study aimed to evaluate the effect of nanoconditioning with zinc oxide (ZnO) nanoparticles on the physical and physiological quality of tomato seeds (Solanum lycopersicum L.) subjected to conditions of water deficit and thermal stress. Seeds of the Gyottone cultivar were subjected to three treatments: control (without conditioning), osmoconditioning with PEG, and osmoconditioning with PEG + nanoparticles of ZnO. After conditioning, the seeds were evaluated through physical and physiological analyses at temperatures of 25 °C and 35 °C, with and without water deficit (-0.3 MPa). The ZnO nanoparticles were also characterized using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The analyses showed that ZnO nanoparticles were effectively incorporated into the seed coat and exhibited a polycrystalline wurtzite structure. Seeds conditioned with PEG showed greater vigor, better seedling development, and improved performance under water and thermal stress. In contrast, the treatment with PEG + ZnO exhibited signs of phytotoxicity, with reduced seedling length and lower vigor, particularly under stress conditions. X-ray analysis confirmed that conditioned seeds exhibited higher density and internal filling, reflecting greater metabolic activity. Nanoconditioning with ZnO, at the tested concentration, compromised the physiological performance of the seeds and did not mitigate the effects of the evaluated stresses, while osmoconditioning with PEG was effective in promoting greater vigor and tolerance to adverse conditions.