Banca de QUALIFICAÇÃO: LEÔNIDAS CANUTO DOS SANTOS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: LEÔNIDAS CANUTO DOS SANTOS
DATA: 12/12/2025
HORA: 14:00
LOCAL: Online pelo google meet
TÍTULO:

Selenium Distribution in Brazilian Soils and Agronomic Biofortification Strategies for Rice under Water Deficit

PALAVRAS-CHAVES:

Selenium geochemistry; Geochemical baseline; Tropical soils; Rice physiology;
Food security; In vitro bioaccessibility; Plant protection; Food quality.

PÁGINAS: 1
GRANDE ÁREA: Ciências Agrárias
ÁREA: Agronomia
SUBÁREA: Ciência do Solo
ESPECIALIDADE: Fertilidade do Solo e Adubação
RESUMO:

Selenium (Se) is an essential element for humans and animals, which require only trace
amounts (approximately 70 μg day-1 for adequate adult nutrition). However, malnutrition,
including Se deficiency, has caused public health problems in poor regions around the world.
The low intake of this element by humans is directly linked to low concentrations in soils,
especially highly weathered tropical soils in Brazil. The parent material, soil moisture, pH,
organic matter, clay content, iron and aluminum oxides strongly influence Se concentration
and mobility in soils. To solve this problem, agronomic biofortification has attracted interest,
as this practice increases the availability of micronutrients to plants, enabling their
incorporation into organic compounds that later enter the human diet, increasing food security
and reducing malnutrition. Additionally, Se enhances antioxidant enzyme activity in plants,
mitigating the deleterious effects of environmental stresses, especially water stress, a problem
that limits agricultural production. Therefore, the objective of this study was to evaluate the
distribution of Se in Brazilian soils and its correlation with soil chemical and physical
attributes, and to develop strategies for agronomic biofortification with Se and evaluate its
potential as a mitigator of water stress in the rice crop (Oryza sativa). For this purpose, three
experiments were carried out to investigate Se concentrations in Brazilian soils, the potential
for biofortification, and protection against stress caused by water deficit. The average
concentration of Se in tropical Brazilian soils varied widely with the parent material and soil
management. Reference soils derived from sedimentary rocks showed a higher average Se
concentration (0.404 mg kg -1 ) than soils of other origins. Reference soils showed an average
Se concentration ranging from 0.150 to 0.404 mg kg -1 , while cultivated soils showed an
average variation from 0.239 to 0.746 mg kg -1 . In cultivated soils of the Atlantic Forest biome,
the Se concentration was significantly higher than in soils of the Cerrado biome. These
findings demonstrate that biomes with distinct biogeoclimatic characteristics strongly
influence Se distribution. Soil organic carbon, clay, and oxyhydroxides were the main divers
of the Se concentration in Brazilian soils. Se protected rice plants from water deficit through
enhancing of antioxidant system enzymes and reducing stress markers. Furthermore, it
improved physiological and biochemical resilience, increasing water use efficiency, stomatal
conductance, and gas exchange, in addition to increasing proline, proteins, and amino acids.
Moreover, the combined foliar application of Se + Zn, and the addition of urea to the spray
solution increased rice productivity. However, the production environment strongly
influenced the responses of plants to the imposition of water deficit. Our study, therefore,
demonstrates that the distribution of Se in tropical soils of Brazil results from the interaction
among lithology, soil management, chemical and physical attributes, and the biogeoclimatic
conditions that modulate its distribution, retention, and mobility in soils. The strategies of
agronomic biofortification proved to be highly beneficial to the rice crop, increasing the
concentration of essential elements for humans and protecting plants from water stress. The
effectiveness of Se application (essentially in conjunction with Zn) enhanced the potential of
agricultural systems, becoming a tool against hidden hunger, increasing bioaccessibility in the
human gastrointestinal system, and increasing food security.

MEMBROS DA BANCA:
Interno - TEOTONIO SOARES DE CARVALHO (Membro)
Presidente - LEONIDAS CARRIJO AZEVEDO MELO (Membro)
Externo à Instituição - FÁBIO AURÉLIO DIAS MARTINS - EPAMIG (Suplente)
Externo à Instituição - FABRÍCIO WILLIAM DE ÁVILA - UNICENTRO (Membro)
Interno - CYNTHIA DE OLIVEIRA - UFLA (Suplente)
Interno - BRUNO MONTOANI SILVA (Membro)