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Caracterização Ecofisiológica de Linhagens de Milho Submetidas a Baixa Disponibilidade Hídrica Durante o Florescimento

DOI: http://dx.doi.org/10.18512/1980-6477/rbms.v8n3p223-232

http://rbms.cnpms.embrapa.br/index.php/ojs/index 

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Paulo C. Magalhães1, Thiago C. de Souza2, Paulo E. P. de Albuquerque1, Décio Karam1, Marcelo M. Magalhães2 & Fernando R. de O. Cantão1

 

Resumo: O estudo de cultivares tolerantes a limitações hídricas é uma alternativa sustentável para mitigar os impactos negativos das mudanças climáticas globais. Este trabalho foi realizado com o objetivo de caracterizar linhagens de milho contrastantes quanto a resistência a seca no estádio de florescimento, baseando-se nas trocas gasosas e fluorescência da clorofila, em casa-de-vegetação. Foram avaliadas três linhagens de milho, sendo duas tolerantes (L 31.2.1.2 e L 29.1.1) e uma sensível (L 2.3.2.1) a deficiência hídrica. No pré-florescimento, dois tratamentos hídricos, sem (SD) e com deficiência hídrica (CD), foram impostos, e após cinco dias de imposição do estresse, foram avaliadas a taxa de fotossíntese foliar (A), a condutância estomática (gs), a transpiração foliar (T), a eficiência intrínseca do uso da água (EIUA, A/gs), o teor relativo de clorofila (SPAD) e parâmetros da fluorescência da clorofila (Fv/Fm, Fo/ FM, Fv/Fo). As linhagens tolerantes a seca apresentaram maior eficiência no uso da água em comparação com a linhagem sensível. A linhagem L 29.1.1 apresentou maior eficiência no fotossistema II (Fv/Fm) do que as linhagens L 2.3.2.1 e L 31.2.1.2. Podese concluir que existem diferenças ecofisiológicas nas trocas gasosas e na fluorescência da clorofila, que caracterizam as linhagens tolerantes à seca em relação às linhagens sensíveis. Os resultados desta pesquisa fornecerão subsídios para os melhoristas selecionarem material tolerante a seca.

Palavras-chave: trocas gasosas, Zea mays L., seca, fluorescência da clorofila.

 

Abstract: The study of cultivars tolerant to water limitation is a sustainable alternative to mitigate the negative impacts of global climatic changes.  This study was performed with the objective of characterizing maize lines exhibiting contrasting drought resistance at flowering stage, using gaseous exchange and chlorophyll fluorescence, under greenhouse conditions. Three maize lines were evaluated, being two tolerant (L 31.2.1.2 and L 29.1.1) and one sensitive (L2.3.2.1) to water deficit. At pre-flowering growth stage, two water treatments were imposed: without stress (WS) and with water deficit (WD). Five days after imposing the water stress the following characteristics were evaluated: photosynthesis rate (A), stomatal conductance (gs), leaf transpiration (T), intrinsic water use efficiency (iWUE, A/gs), relative chlorophyll content (SPAD) and chlorophyll fluorescence parameters (Fv/Fm; Fo/FM; Fv/Fo). The drought tolerant lines showed greater efficiency in water use, compared to the sensitive line. The line L 29.1.1 presented greater photosystem II efficiency (Fv/Fm) than lines L 2.3.2.1 and L 31.1.2. Based on the results it can be concluded that there are ecophysiological differences on gaseous exchange and chlorophyll fluorescence, which characterize the drought tolerant lines, when compared to the sensitive one. The results obtained in this research will be useful for plant breeders to select drought tolerant genotypes.

Key words: gaseous exchange, Zea Mays L., drought, chlorophyll fluorescence.

 

1 Embrapa Milho e Sorgo, Sete Lagoas, MG, Brasil, caixa postal 151, cEp 35701-970, pcesar@ cnpms.embrapa.br
2 Departamento de Biologia, Setor de Fisiologia Vegetal, campus Universitário, Lavras, MG, Brasil, caixa postal 37, cEp 37200-000, thiagonepre@hotmail.com

 

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