Revista Ciência Agronômica (Sep 2013)
Eficiência na absorção e utilização de nitrogênio e atividade enzimática em genótipos de milho Nitrogen uptake and utilization efficiency and enzymatic activity in maize genotypes
Abstract
O objetivo desse estudo foi investigar o emprego dos componentes da eficiência no uso de nitrogênio e das atividades das enzimas nitrato redutase e glutamina sintetase na seleção de genótipos de milho eficientes no uso de nitrogênio (N). Foram avaliados 10 genótipos de milho em estádio de V4 em condições de alto e baixo N. O experimento foi composto por um fatorial 2 x 10 (dois níveis de N e 10 genótipos de milho) em delineamento inteiramente casualizados com três repetições. Os seguintes caracteres foram avaliados: as eficiências na absorção (EAbN), na utilização (EUtN) e no uso de N (EUsN) e as atividades das enzimas glutamina sintetase (GS) e nitrato redutase (NR). Para os caracteres que o efeito de genótipos foi significativo (pThe aim of this study was to investigate the employment of components of the nitrogen efficiency use (NUE), and of the activities of the nitrate reductase and glutamine synthetase enzymes in the selection of nitrogen use efficient maize genotypes of maize. Ten maize genotypes at V4 stage were evaluated under high and low N. The experiment consisted of a 2 x 10 factorial (two levels of N and ten maize genotypes), in a randomized complete block design with three replicates. The following traits were evaluated: N uptake efficiency (NUpE), N utilization efficiency (NUtE) and N use efficiency (NUE), and activities of the glutamine synthetase (GS) and nitrate reductase (NR) enzymes. For traits which the effect of genotype was significant (p<0.05) in the variance analysis for level of N, the mean were compared using the t test (p<0.05). The indirect gains in NUE and their components with selection over the activities of the enzymes NR and GS were estimated under low N. We conclude that: under high N, NupE is efficient to differentiate nitrogen use efficient maize genotypes; under low N, NupE and NUtE efficient to differentiate nitrogen use efficient maize genotypes, the activity of NR enzyme is not a good physiological parameter for differentiate nitrogen use efficient maize genotypes, and selection over activity of GS enzyme enables the indirect selection of nitrogen use efficient maize genotypes.
