Foliar Calcium Absorption by Tomato Plants: Comparing the Effects of Calcium Sources and Adjuvant Usage

Author(s)

Santos, Eduardo ; Montanha, Gabriel Sgarbiero ; Agostinho, Luis Fernando ; Polezi, Samira ; Marques, Joao Paulo Rodrigues ; de Carvalho, Hudson Wallace Pereira

• Document type: Journal article
• Source: PLANTS-BASEL; v. 12, n. 14, p. 15-pg., 2023-07-01.

Abstract

The deficiency of calcium (Ca) reduces the quality and shelf life of fruits. In this scenario, although foliar spraying of Ca2+ has been used, altogether with soil fertilization, as an alternative to prevent deficiencies, little is known regarding its absorption dynamics by plant leaves. Herein, in vivo microprobe X-ray fluorescence was employed aiming to monitor the foliar absorption of CaCl2, Ca-citrate complex, and Ca-3(PO4)(2) nanoparticles with and without using adjuvant. We also investigated whether Sr2+ can be employed as Ca2+ proxy in foliar absorption studies. Moreover, the impact of treatments on the cuticle structure was evaluated by scanning electron microscopy. For this study, 45-day-old tomato (Solanum lycopersicum L., cv. Micro-Tom) plants were used as a model species. After 100 h, the leaves absorbed 90, 18, and 4% of aqueous CaCl2, Ca-citrate, and Ca-3(PO4)(2) nanoparticles, respectively. The addition of adjuvant increased the absorption of Ca-citrate to 28%, decreased that of CaCl2 to 77%, and did not affect Ca-3(PO4)(2). CaCl2 displayed an exponential decay absorption profile with half-lives of 15 h and 5 h without and with adjuvant, respectively. Ca-citrate and Ca-3(PO4)(2) exhibited absorption profiles that were closer to a linear behavior. Sr2+ was a suitable Ca2+ tracer because of its similar absorption profiles. Furthermore, the use of adjuvant affected the epicuticular crystal structure. Our findings reveal that CaCl2 was the most efficient Ca2+ source. The effects caused by adjuvant suggest that CaCl2 and Ca-citrate were absorbed mostly through hydrophilic and lipophilic pathways. (AU)

• FAPESP's process: 22/10718-5 - Characterization of calcium foliar absorption and its translocation by tomato plants using strontium as a physiological tracer
• Grantee: Eduardo Santos
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate