Characterization of the foliar uptake of zinc sources by soybean (Glycine max L.)

• Autor(a) principal: Gomes, Marcos Henrique Feresin
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/64/64135/tde-31102023-093912/
• topic: Adubação foliar; Cellulose microbeads. Nanoparticles; Espectroscopia de Absorção de Raios X Próximo da Borda (XANES); Espectroscopia por Fluorescência de Raios X (XRF); Foliar fertilization; Microesferas de celulose. Nanopartículas; X-Ray Absorption Near Edge Spectroscopy (XANES); X-Ray Fluorescence Spectroscopy (XRF); Zn

Zinc (Zn) is an essential element for plant, animal and human nutrition. Around the world, ca. 800,000 children under 5 years die annually due to a Zn-deficient diet. The application of zinc in crops can be performed on plant leaves or in the soil, however, the low use-efficiency is remarkable. This study aims to understand and characterize the absorption, transport and metabolization of Zn when applied on soybean leaves by the most common fertilizers used by worldwide, i.e. inorganic salts, complexes/chelates, and concentrated suspensions, as well as evaluate possibility of the employment of new technologies, such as nanoparticles and cellulose microspheres. X-ray fluorescence (XRF) and X-ray absorption (XANES) spectroscopy were employed to perform in vivo analysis on soybean plants together with greenhouse trials. The absorption and transport of Zn depended on the type of Zn source. Zinc from ZnSO4 was absorbed and transported faster than ZnO commercial suspension, while Zn applied as Zn-phosphite was transported faster than Zn-EDTA. The XANES analysis demonstrated that Zn from ZnSO4 and Zn phosphite was transported bound with organic acids such as malate and citrate. Conversely, Zn supplied by Zn-EDTA was transported in its pristine form. In a short-term experiment, i.e. few days, cellulose microspheres were able to reduce the toxicity caused by ZnSO4 salts and increase Zn transport trough leaf petiole. However, under longer evaluation, i.e. a couple of weeks, the root application of ZnSO4 increased by 42% the Zn accumulation in soybean plants compared to the control (low Zn supply). Additionally, root uptake mechanism under hydroponics was more efficient than the foliar application of ZnSO4, ZnO nanoparticles and ZnSO4 + cellulose microspheres. The foliar and root application of Zn did not affect the activity of ezymes related to the metabolism of reactive oxygen species. Understanding the mechanisms ruling the foliar absorption and metabolization of nutrients is fundamental for the development of the next generation of fertilizers. Therefore, more studies on this subject are necessary