Efeito do silício na anatomia radicular e na produção de grãos de arroz

• Ano de defesa: 2013
• Autor(a) principal: Lavinsky, Alyne Oliveira
• Orientador(a): Damatta, Fábio Murilo
• Banca de defesa: Detmann, Kelly da Silva Coutinho , Cavatte, Paulo Cezar
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fisiologia Vegetal
• Departamento: Controle da maturação e senescência em órgãos perecíveis; Fisiologia molecular de plantas superiores
• País: BR
• Palavras-chave em Português: Índice de colheita; Panícula; Microanálise raios-X
• Palavras-chave em Inglês: Harvest index; Panicle; X-ray microanalysis
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::FISIOLOGIA DE PLANTAS CULTIVADAS
• Link de acesso: http://locus.ufv.br/handle/123456789/1002

Silicon (Si) is one of most abundant element in Earth crust. All plants grown in soil contain some Si in their tissues, and due to the widespread abundance of this element in nature and non-apparent visible symptoms of either def1ciency or toxicity, Si is often assumed to be biologically unreactive and it is not considered as an essential element for higher plants, except under stressful condition. However, repeated cropping and constant application of chemical fertilizers have depleted the amount of Si that is available to plants in the soil. An awareness of Si def1ciency in soil has been now recognized as a limiting factor for crop production particularly in soils that are deemed to be low or limiting in plant available Si for known Si-accumulating species such as rice (Oryza satíva). The effects of removal or addition of Si during the vegetative (V) or reproductive growth stages (corresponding to panicle formation (Rl) or grain filling (R2)) on the rice grain production and physiological related traits were evaluated. It was found that Si fertilization during Rl played a pivotal role in the enhanced number and mass of rice grains, with little, if any, significant impact of this element on grain yield when supplied during V and/or R2 stages, regardless of treatments, the panicle number, leaf area and total biomass remained unaltered. Consequently, the harvest index increased by 61% (coupled to higher percentage of filled spikelets and grain mass) in plants supplied with Si during Rl in relation to the others groups. There was a much higher number of filled grains and loo0-grain weight in these plants. Noteworthy, Si is essential during panicle formation and plants that received Si during Rl overexpressed the gene Lsíó, possibly to ensure Si concentration in panicle similar those found in Si- fertilized plants since the beginning of growth cycle. Increased grain yield led to improvements of the source capacity through a feed-forward stimulation of 15% on photosynthetic rates of the flag leaf, probably to support increased sink demand coupled with anticipation of grain filling, which, in turn, shifted sucrose accumulated to embryo, increasing embryo area. Furthermore, it was shown that Si, to some extent, affected the carbonic anhydrase (CA) activity and aquaporin abundance, it was also depicted an existing interaction between CA and three genes encoding for transporters of organic acids in the guard cells, and one gene associated with the activation of the enzyme RuBisCO, in agreement with the highest Values of maximum rate of carboxylation limited by Ribulose-1,5-bisphosphate and maximum rate of carboxylation limited by electron transport in Si-fertilized plants during Rl. Therein the root tissues, Si fertilization increased phenylalanine ammonia liase and led to increased suberization of the exodermis and lignif1cation of the sclerenchyma, which collectiVely may act to form a barrier against radial O; loss (PRO) of the root tissues. In addition, Si affected the extent of aerenchyma. In parallel, scanning electron microphotographs associated with X-ray energy dispersiVe spectroscopy revealed that Fe deposition increased four-times on root surface of Si-fertilized plants, while the deposition of Ca was decreased by 58% compared to their counterparts not challenged with Si. In turn, the root concentrations of Fe and Ca, measured by atomic absorption spectrometry, were reduced in Si-fertilized plants. From the above, it is proposed that Si fertilization is necessary not only to increase productiVity, but also to promote simultaneous formation of barrier against PRO and Fe plaque in rice roots, which in turn imposes compensatory changes in root morphology to increase hypoxia tolerance, with little effect on Si absorption.