Banca de DEFESA: SUSANA SILVA CONCEIÇÃO
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : SUSANA SILVA CONCEIÇÃO
DATA : 29/10/2019
HORA: 15:00
LOCAL: Sala 02 do Curso de Pós-graduação de Ciências Florestais
TÍTULO:
Cadmium phytoremediation by Khaya ivorensis A. Chev. MITIGATION OF SILENT STRESS IN PHYSIOLOGICAL, BIOCHEMICAL AND ANATOMIC MODULATIONS.
PALAVRAS-CHAVES:
Heavy metal, silica, chlorophyll a fluorescence, antioxidants, epidermal thickness.
PÁGINAS: 101
GRANDE ÁREA: Ciências Agrárias
ÁREA: Recursos Florestais e Engenharia Florestal
RESUMO:
Among the heavy metals (MPs), cadmium (Cd) represents one of the biggest threats to the environment on a global scale, due to its high ecotoxicological potential and increasing soil indices, which contributes to the loss of carbon dioxide. productivity and biodiversity of ecosystems. Fast-growing woody plants represent effective tools for Cd extraction in contaminated soils. In this sense, African mahogany (Khaya ivorensis A. Chev), a tree species belonging to the Meliaceae family, presents satisfactory characteristics for remediation due to accelerated growth, axial root system and high biomass production. However, the phytoremediation strategies and mechanisms of Cd tolerance implemented by this species, associated with the improvement of nutritional status, are not clear. From the above, this research aims to identify the modulations of silicon (Si), a beneficial micronutrient, in physiology , biochemistry, antioxidant system and anatomy of African mahogany seedlings submitted to toxic levels of Cd and correlate these processes with the increase of phytoremediation potential to MP. The experimental design was a randomized block design in a 4x4 factorial scheme with five repetitions, and the factors constituted by increasing levels of MP (Cd 0, 25, 50 and 75 mg L-1) and doses of silicon (Si 0, 100, 150 and 300 mg L-1). Polynomial regression, response surface. The concentrations of Cd 50 and 75 mg L-1 were toxic and caused changes in biochemical processes with negative physiological and anatomical repercussions in Khaya ivorensis. There were photoinhibitory damages to the PSII, where the variables of chlorophyll a, (ΦPSII), (qP) and (ETR) fluorescence, photosynthesis (A), gas exchange (gs), (Ci/Ca) and photosynthetic pigments, especially chlorophyll b, were the most affected by the highest metal level and presented respective minimum points by the regression adjustment of 0.05; 0.07; 0.15 µmol CO2 molar-1; 3.2 mmol CO2 m-2 s-1; 0.1 mol H2O m-2 s-1; 0.06 µmol CO2 molar-1 and 0.18 mg g-1 and were 78%, 82%, 75%, 83%, 96%, 93% and 95% lower than the control. Disruption in cytosolic metabolism caused lipid peroxidation. Malonoaldehyde (MDA) content was increased by 63% and 69% in leaves and roots, which was accompanied by reductions in activity of antioxidant enzymes. Above all, APX expression decreased by 69% in the root system. Anatomical changes in tissues occurred with marked decreases in epidermal thickness. The palisade parenchyma and root cortex were 84% and 72% less thick under that toxic level of Cd. However, Si attenuated the stress promoted by the ion and modulated an overpressure in those variables, which ensured the growth and development of Kaya ivorensis under conditions of MP contamination. Normal plant metabolism was resumed only in those treated with Cd 50 mg L-1 and nourished with Si 150 mg L-1. Canonical analysis showed that the combination of Cd 45 mg L-1 and Si 160 mg L-1, resulted in the maximum expression points of those parameters, where the values came close to the control. Si modulation in antioxidant metabolism was confirmed by the 31% increase in SOD activity. These response patterns were related to the reduction of Cd translocation to the aerial parts and its Si-induced entrapment in the root system. Thus, the micronutrient increased the tolerance and phytoremediation potential of Khaya ivorensis to Cd by phytostabilization of the MP, was due to mechanisms of cocomplexation of Si to Cd, as well as to the ion restrictions imposed by the caspary striae, mediated by Si. We also attributed to the improvement in water relations.
MEMBROS DA BANCA:
Presidente - 2595267 - CANDIDO FERREIRA DE OLIVEIRA NETO
Externo ao Programa - 140.391.332-34 - JESSIVALDO RODRIGUES GALVAO - UFRA
Externo ao Programa - 1492115 - ANTONIO VINICIUS CORREA BARBOSA
Externo à Instituição - SEBASTIÃO DA CUNHA LOPES - UEPA
Externo à Instituição - CRISTINE BASTOS DO AMARANTE - INT