Banca de DEFESA: ANDRESSA FABIANE FARIA DE SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANDRESSA FABIANE FARIA DE SOUZA
DATE: 29/11/2022
TIME: 14:00
LOCAL: VIDEOCONFERÊNCIA
TITLE:

Signaling pathways activated by humic acids to stimulate root growth in rice plants

KEY WORDS:

Humic acid. Root Growth. Reactive Oxygen Species. Rice. 

PAGES: 108
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

The use of biostimulants is gaining significant scientific and commercial visibility and is considered a promising technique in improving the ecological sustainability of crop production. Among the biostimulant substances, numerous studies report the effect of humic acids (HA) as a root growth promoter improving the acquisition and efficient use of nutrients, increased tolerance to abiotic stresses, and productivity. Despite the established evidence of biostimulant effects, many functional aspects still need to be elucidated. The research performed in this thesis looks to contribute to the understanding of the physiological mechanisms behind these responses using phenotypic and molecular approaches associated with the use of ROS inhibitors and hormonal pathways. The following hypotheses were formulated: (i) if AH is able to stimulate root system growth in the presence of a specific inhibitor, it is because the route interrupted by the given inhibitor is not the preferred pathway in the mechanism of action of AH; (ii) on the other hand, if AH does not stimulate root system growth in the presence of a given inhibitor, it is because this route is the preferred pathway in the mechanism of action of AH. To verify these premises, the purpose of this research was to elucidate the signaling mechanisms by which humic acid stimulates root system growth in rice plants. The specific purposes were: a) to determine the optimum concentration of humic acid for the greatest stimulus to root system growth; b) to determine the optimum concentration of reactive oxygen species inhibitors (scavengers) and inhibitors of hormonal action that result in harm to the development of the root system, without, however, presenting severe toxicity to the plants; c) to combine the application of inhibitors and humic acid and verify the effect on the development of the root system of rice plants; d) by both phenotypic and molecular approaches, elucidate the signaling mechanisms activated by the application of AH. The data obtained from the execution of this study suggest AH from vermicompost has a higher predominance of aliphatic fragments and carboxylic carbon, which contribute to increased bioactivity. Through the phenotypic approach it was possible to verify the effects of AH application on the morpho-physiological characteristics of rice seedlings, suggesting that root growth promotion is a mechanism dependent on ROS production, and the stimulatory effect of AH seems to be dependent on HO*, O₂^-* e H₂O₂. production. Through the molecular approach it was possible to observe changes in gene regulation caused by the application of AH, being more expressive in genes related to antioxidant enzymes. The results presented in this study show that AH extracted from vermicompost play a role in stimulating root growth in rice plants and clearly it is a mechanism dependent on ROS and hormonal signaling pathways, in addition to the protective effect on plant growth, partly explaining the physiological mechanisms of AH behind the responses in promoting root growth.

COMMITTEE MEMBERS:
Presidente - 2626406 - LEANDRO AZEVEDO SANTOS
Externo à Instituição - LEONARDO BARROS DOBBSS - UFVJM
Externa à Instituição - MARCIA SOARES VIDAL - EMBRAPA
Interno - ***.383.947-** - ORLANDO CARLOS HUERTAS TAVARES - UFRRJ
Interno - 387406 - RICARDO LUIZ LOURO BERBARA