Banca de DEFESA: LORENE BIANCA ARAUJO TADAIESKY

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LORENE BIANCA ARAUJO TADAIESKY
DATA : 16/02/2019
HORA: 09:00
LOCAL: Auditório da biblioteca/UFRA
TÍTULO:

IRON TOLERANCE MODULATED BY BRASSINOSTEROIDS IS TRIGGERED ENHANCING AERENCHYMA AREA AND METAL HOMEOSTASIS, COUPLED TO BENEFITS ON ROS SCAVENGING AND CO2 ASSIMILATION IN RICE
PLANTS

PALAVRAS-CHAVES:

24-epibrassinolide. Catalase. Photosynthesis. Oryza sativa. Root anatomy

PÁGINAS: 67
RESUMO:

Iron (Fe) toxicity is one of the most frequent abiotic stresses in rice, affecting from 15% to
30% of total production. Brassinosteroids (BRs), including the 24-epibrassinolide (EBR)
regulate ion homeostasis and improve antioxidant system. The aim of this research was to
answer if the EBR can contribute to tolerance of rice plants exposed to Fe toxicity, evaluating
the possible repercussions on anatomical characteristics, nutrient concentrations, antioxidant
system, and gas exchange. The experiment was randomized with four treatments, including
two Fe supply (250 and 6250 Mm Fe described as control and toxicity, respectively) and two
concentrations of brassinosteroids (0 and 10 nM EBR, described as – EBR and + EBR,
respectively). Plants exposed to Fe toxicity and treated with EBR presented increases in
Mg2+/Fe2+, Mn2+/Fe2+, Cu2+/Fe2+ and Zn2+/Fe2+ ratios in shoot of 83%, 89%, 103% and 120%,
comparing with same treatment without EBR. This research revealed that the EBR mitigated
the deleterious effects of the Fe toxicity on rice plants, modulating the aerenchyma area, in
which this structure contribute to the formation of an oxidative barrier, Fe immobilization in
root surface. Concomitantly, this steroid increased the contents of other metals, such as
magnesium, manganese, copper and zinc, proving the influence related to metal homeostasis,
confirmed by increases in metal ratios. Plants under Fe toxicity and treated with EBR
presented increases in all enzyme activities evaluated, superoxide dismutase, catalase,
ascorbate peroxidase and peroxidase, mitigating the oxidative damages and favoring the
scavenging of reactive oxygen species. Finally, the EBR actions alleviated the negative
impacts induced by Fe excess on net photosynthetic rate and carboxylation instantaneous
efficiency, being these benefits directly related to higher electron transport and stomatal
density and indirectly linked to protection mechanism exercised by the antioxidant enzymes
on photosynthetic machinery. Therefore, our results clearly indicate that the EBR is able to
confer tolerance in rice plants under Fe toxicity.

MEMBROS DA BANCA:
Presidente - 1803899 - ALLAN KLYNGER DA SILVA LOBATO
Interno - 1551252 - GISELE BARATA DA SILVA
Externo ao Programa - 1740947 - DENMORA GOMES DE ARAUJO
Externo à Instituição - RAFAEL SILVA GUEDES - NENHUMA