Biostimulant Response of Foliar Application of Rare Earth Elements on Physiology, Growth, and Yield of Rice
Author:
de Oliveira Cynthia1ORCID, Ramos Silvio Junio2ORCID, Dinali Guilherme Soares3, de Carvalho Teotonio Soares1, Martins Fábio Aurélio Dias4ORCID, Faquin Valdemar1, Castro Evaristo Mauro de5, Sarkis Jorge Eduardo Souza6, Siqueira José Oswaldo1, Guilherme Luiz Roberto Guimarães1ORCID
Affiliation:
1. Departamento de Ciência do Solo, Universidade Federal de Lavras (UFLA), Lavras 37203-202, Brazil 2. Instituto Tecnológico Vale—Desenvolvimento Sustentável, Rua Boaventura da Silva, 955, Belém 66055-090, Brazil 3. ICL, Avenida Doutora Ruth Cardoso, 8501, Butantã, São Paulo 04795-100, Brazil 4. Empresa de Pesquisa Agropecuária de Minas Gerais (EPAMIG), Lavras 37200-000, Brazil 5. Departamento de Biologia, Universidade Federal de Lavras (UFLA), Lavras 37203-202, Brazil 6. Instituto de Pesquisas Energéticas e Nucleares (IPEN), Universidade de São Paulo (USP), Avenida Lineu Prestes, 2242, Cidade Universitária, São Paulo 05508-000, Brazil
Abstract
Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily applied to soils through phosphate fertilizers. These elements are known to alleviate damage in plants under abiotic stresses, yet there is no information on how these elements act in the physiology of plants. The REE mode of action falls within the scope of the hormesis effect, with low-dose stimulation and high-dose adverse reactions. This study aimed to verify how REEs affect rice plants’ physiology to test the threshold dose at which REEs could act as biostimulants in these plants. In experiment 1, 0.411 kg ha−1 (foliar application) of a mixture of REE (containing 41.38% Ce, 23.95% La, 13.58% Pr, and 4.32% Nd) was applied, as well as two products containing 41.38% Ce and 23.95% La separately. The characteristics of chlorophyll a fluorescence, gas exchanges, SPAD index, and biomass (pot conditions) were evaluated. For experiment 2, increasing rates of the REE mix (0, 0.1, 0.225, 0.5, and 1 kg ha−1) (field conditions) were used to study their effect on rice grain yield and nutrient concentration of rice leaves. Adding REEs to plants increased biomass production (23% with Ce, 31% with La, and 63% with REE Mix application) due to improved photosynthetic rate (8% with Ce, 15% with La, and 27% with REE mix), favored by the higher electronic flow (photosynthetic electron transport chain) (increase of 17%) and by the higher Fv/Fm (increase of 14%) and quantum yield of photosystem II (increase of 20% with Ce and La, and 29% with REE Mix), as well as by increased stomatal conductance (increase of 36%) and SPAD index (increase of 10% with Ce, 12% with La, and 15% with REE mix). Moreover, adding REEs potentiated the photosynthetic process by increasing rice leaves’ N, Mg, K, and Mn concentrations (24–46%). The dose for the higher rice grain yield (an increase of 113%) was estimated for the REE mix at 0.72 kg ha−1.
Funder
“Instituto Tecnológico Vale” in cooperation with the Federal University of Lavras National Council for Scientific and Technological Development National Institute of Science and Technology (INCT) on Soil and Food Security Minas Gerais State Research Foundation
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