Root phosphatase activity, plant growth and phosphorus accumulation of maize genotypes

Abstract

The activity of the enzyme phosphatase (P-ase) is a physiological characteristic related to plant efficiency in relation to P acquisition and utilization, and is genetically variable. As part of a study on maize genotype characterization in relation to phosphorus (P) uptake and utilization efficiency, two experiments were set up to measure phosphatase (P-ase) activity in intact roots of six local and improved maize varieties and two sub-populations. Plants were grown at one P level in nutrient solution (4 mg L -1) and the P-ase activity assay was run using 17-day-old plants for varieties and 24-day-old plants for subpopulations. Shoot and root dry matter yields and P concentrations and contents in plant parts were determined, as well as P-efficiency indexes. Root P-ase activity differed among varieties, and highest enzimatic activities were observed in two local varieties -'Catetão' and 'Caiano' -and three improved varieties -'Sol da Manhã', 'Nitrodente' and 'BR 106'. 'Carioca', a local variety, had the lowest activity. Between subpopulations, 'ND 2 ', with low yielding and poorly P-efficient plants, presented higher root P-ase activity as compared to 'ND 10 ', high yielding and highly P-efficient plants.In general, subpopulations presented lower P-ase activities as compared to varieties. Positive and/or negative correlations were obtained between P-ase activity and P-efficiency characteristics, specific for the genotypes, not allowing inference on a general and clear association between root-secreted phosphatase and dry matter production or P acquisition. Genotypic variability must be known and considered before using P-ase activity as an indicator of P nutritional status, or P tolerance, adaptation and efficiency under low P conditions. Key words: Zea mays L., genetic variability, enzymatic activity, nutritional efficiency ATIVIDADE DE FOSFATASE ÁCIDA DE RAÍZES, CRESCIMENTO DAS PLANTAS E ACÚMULO DE FÓSFORO EM GENÓTIPOS DE MILHORESUMO: A atividade da enzima fosfatase é uma característica fisiológica relacionada à eficiência de aquisição e utilização de P pelas plantas e apresenta variação genotípica. Como parte de um estudo de caracterização de genótipos de milho quanto a características relacionadas à eficiência a fósforo, foram realizados dois experimentos para medir a atividade da fosfatase ácida de raízes intactas de seis variedades locais e melhoradas e de duas subpopulações. As plantas foram cultivadas em solução nutritiva com uma dose de P (4 mg L -1 ) e a determinação da atividade da fosfatase foi feita em plantas jovens de 17 a 24 dias de idade. A produção de massa seca da parte aérea e raízes, teor e conteúdo de P e índice de eficiência de utilização de P também foram determinados. Entre as variedades, a maior atividade enzimática foi verificada em Catetão e Caiano (locais), e Sol da Manhã, Nitrodente e BR 106 (melhoradas). A variedade local Carioca foi a de menor atividade da fosfatase nas raízes. Entre as subpopulações, 'ND 2 ' foi menos produtiva e menos eficiente na utilização de P, apre...

Potential of Acid Phosphatase Activity and Mycorrhizal Colonization to Reduce Phosphorus Fertilization in Maize Cultivated in Brazil

“…The differences in PME activity found amongst the lineages show that genetic variability for this character exists (Table 2), agreeing with results shown by Machado and Furlani (2004), which evaluated six genotypes (three common and three improved varieties) and identi ed one genotype with signi cantly a lower PME activity in comparison to the others. The occurrence of genetic variability was also detected by Chen et al (2008), who estimated the broad-sense heritability as 52.7% for PME activity and as 90.9% for P absorption e ciency in maize.…”

Fertilizer P Uptake Determined by Soil P Fractionation and Phosphatase Activity

“…However, we observed a clear correlation between root P-ase and shoot P concentration (Fig. S1a), which could be attributed to plant adaptation to low P, enhanced root P-ase activity being related to P-ase root secretion followed by hydrolysis of organic P (Machado and Furlani 2004). The increase in root P-ase activity on addition of P fertilizer may reflect the role of P-ase in the cycling of stored P in plants, rather than a strategy to obtain P from soil.…”

“…Studies performed on agroforestry species showed that phosphatase activities increased in the rhizosphere of agroforestry species, either directly by secretion or indirectly by stimulation of microbial activity and/or depletion of P i (George et al 2002). However, no clear relationships were found between the activities of both root-associated and exuded phosphatases and the P concentration and content of plants (Machado and Furlani 2004).…”

Colonização micorrízica e atividade de fosfatases ácidas na rizosfera de cultivares de cana-de-açúcar após aplicação de herbicidas

“…Esses resultados demonstram diferentes interações entre os cultivares e os microrganismos do solo. Essas interações foram também encontradas por Machado & Furlani (2004) em solos rizosféricos de genótipos de milho. Também em soja, alguns cultivares apresentaram maior atividade de fosfatase no solo rizosférico (Raposo et al, 2004 Tabela 5 -Atividade de fosfomonoesterases ácidas de solo rizosférico de cana-de-açúcar, amostrado a 10 cm de profundidade, em função de cultivares e herbicidas, aos 7, 14 e 28 dias após a aplicação dos herbicidas.…”