Impactos negativos do arsênico na fotossíntese em folhas de arroz são mitigados pela suplementação de silício, sem aumento da capacidade antioxidante

• Autor(a) principal: Sanglard, Lílian Maria Vincis Pereira
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4345
• topic: Arroz - Fisiologia; Antioxidante; Arsênio; Fluorescência; Fotossíntese; Stress oxidativo; Silício; Rice - Physiology; Antioxidant; Arsenic; Fluorescence; Photosynthesis; Oxidative stress; Silicon; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::MELHORAMENTO VEGETAL

Silicon (Si) plays important roles in alleviating various abiotic stresses, possibly by counteracting stress-induced oxidative damage. In rice (Oryza sativa), arsenic (As) is believed to cause oxidative stress and to share the Si transport pathway for entry into roots. Despite much progress in understanding the mechanisms underlying the uptake of As and how they can be affected by Si, the physiological mechanisms through which Si might alleviate As toxicity in plants remain to be elucidated. We combined gas exchange and chlorophyll fluorescence measurements with analysis of the activity of the antioxidant system to examine the effects of Si nutrition on photosynthetic performance and oxidative stress in rice plants (a wild-type cultivar and its lsi1 mutant defective in Si uptake) challenged with arsenite. Arsenite treatment led to an impairment of carbon fixation that was unrelated to stomatal and photochemical limitations but, rather, was associated with decreased mesophyll conductance. This impairment could be reverted to a considerable extent by Si in a time- and genotypedependent manner. The ameliorative effects of Si on As-treated plants were uncoupled from any noticeable up-regulation of the antioxidant capacity. We identified Si nutrition as an important target in attempts to not only decrease As concentrations but also to improve the photosynthetic performance of rice plants challenged with As, which may ultimately result in better crop yield coupled with enhanced food safety.