Banca de QUALIFICAÇÃO: MARIA ELIZIANE PANTOJA DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : MARIA ELIZIANE PANTOJA DA SILVA
DATA : 28/02/2025
HORA: 15:00
LOCAL: On line
TÍTULO:

Exogenous dopamine reduces oxidative damage to the photosynthetic system, antioxidant defense and stimulates the increase in biomass of rice plants subjected to iron excess

PALAVRAS-CHAVES:

Antioxidant enzymes. Oryza Sativa. Photosynthesis. Neurotransmitter. Toxicity

PÁGINAS: 46
RESUMO:

Rice is a crucial food crop, often cultivated in waterlogged soils. However, waterlogged soils with low pH can exhibit iron (Fe) toxicity due to low redox potential, which increases Fe availability. Excessive Fe concentrations in these soils are harmful to rice plants, causing toxicity and affecting growth and productivity. In this context, dopamine (DOP) has emerged as a molecule that regulates stress in plants. Therefore, the objective of this research was to investigate whether the exogenous application of dopamine can reduce oxidative damage to the photosynthetic system in rice leaves exposed to excess Fe, as well as to evaluate changes in leaf structure, stomatal variables, reactive oxygen species production, antioxidant enzyme activity, and the nutritional status of the plants. The research was conducted at the Federal Rural University of the Amazon, Paragominas Campus, in a greenhouse with controlled temperature and humidity. Seedlings of O. sativa, 10 days old, were selected and cultivated under hydroponic conditions. The experiment consisted of four treatments, including two with Fe supply (250 and 5000 μM Fe, representing control and excess conditions, respectively) and two dopamine concentrations (0 and 50 μM DOP, referred to as −DOP and +DOP, respectively). DOP was applied directly to the nutrient solution for 20 days (days 20-40 after sowing). Fe was supplied for 10 days (days 30-40). On the 40th day, physiological and morphological parameters were measured, and tissues were collected for anatomical, biochemical, and nutritional analyses. The results were analyzed according to statistical assumptions and subjected to one-way ANOVA. Significant differences between means were evaluated using the Scott-Knott test at a 5% significance level. The results showed that stress caused by excess Fe damaged the photosynthetic apparatus. However, DOP minimized oxidative damage, promoting increases in Chl a (4%), Chl b (7%), Total Chl (5%), and Car (30%). Exogenous DOP caused increases of 6%, 4%, and 2% in Fv, Fm, and Fv/Fm, respectively. There were increases in ΦPSII (13%) qP (11%), and ETR (13%) with DOP application. In gas exchange parameters, the treatment with excess Fe and DOP showed increases in PN, QUE and PN/Ci of 14%, 25%, and 23%, respectively. DOP contributed to antioxidant defense, enhancing the activities of SOD (33%), CAT (29%), APX (75%), and POX (17%), while reducing concentrations of ROS such as O2 - (14%) and H2O2 (8%), as well as MDA (37%) and EL (4%). Plants exposed to excess Fe exhibited reductions in biomass. In contrast, DOP favored increases in SDM, RDM, and TDM of 6%, 3%, and 6%, respectively. Therefore, exogenous dopamine proved effective in mitigating the toxic effects of excess Fe, protecting the photosynthetic system, reinforcing antioxidant defense, and stimulating the growth of rice plants.

MEMBROS DA BANCA:
Presidente - 1803899 - ALLAN KLYNGER DA SILVA LOBATO
Externo à Instituição - FLÁVIO JOSÉ RODRIGUES CRUZ - IFAP
Externo à Instituição - IVAN BECARI VIANA - UEMG
Externa à Instituição - TALITHA SOARES PEREIRA