Nanopartículas na fisiologia e bioquímica de girassol sob estresse hídrico

Abstract

Water deficit is one of the main environmental factors that affects plant growth and development. This study evaluated the effects of nanoparticles on ornamental sunflower Smiley under water stress. The experiment was conducted in a greenhouse and consist of two factors: the first factor consisted of four different molecule sources (copper sulfate, chitosan nanoparticles, and chitosan nanoparticles incorporated with copper sulfate), the second factor involved two water conditions (no water deficit at 90% of water retention capacity and water deficit at 60% of water retention capacity for a period of four consecutive days) which were factorially combined and laid out in a Completely Randomize Design (CRD) and replicated fifteen (15) times. The molecules were applied via foliar spray in the morning, between 8 and 9 a.m., with two applications before imposing water deficit during the vegetative phase V6 and the reproductive phase R1, respectively while water deficit was imposed at the beginning of the reproductive period, during the R1 phase. Growth, eco-physiological, and biochemical parameters were evaluated during the reproductive phase, at stages R4 and R5. Plant durability was assessed during the reproductive period, at stage R6. Results showed higher average values in the treatment with chitosan nanoparticles incorporated with copper sulfate. This treatment resulted to a higher mean values for variables such as plant height, stem diameter, midday water potential, stomatal conductance, photosynthetic pigments (chlorophylls a, b, and carotenoid content), reducing sugars, total soluble sugars, proteins, and amino acids. However, reductions in the mean values were observed for proline, malondialdehyde, and hydrogen peroxide levels. Additionally, higher averages were found in the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase, and catalase. Greater mean values were also observed on the variables analyzed at the end of the experiment, such as relative water content, fresh biomass (roots, stems, leaves, and inflorescences), dry biomass (roots, leaves, inflorescences), and stem diameter. It can be concluded that chitosan nanoparticles, especially when incorporated with copper sulfate, have the potential to mitigate the effects of water stress in potted ornamental sunflower plants.