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Universidade Federal Rural de Pernambuco (2013)

Populações bacterianas nodulíferas de leguminosas em solos da caatinga com distintos períodos de regeneração

Morais Andrade Monaliza Mirella de

Titre : Populações bacterianas nodulíferas de leguminosas em solos da caatinga com distintos períodos de regeneração.

Auteur : Morais Andrade Monaliza Mirella de

Université de soutenance : Universidade Federal Rural de Pernambuco

Grade : Mestre em Ciencia do Solo 2013

Résumé
.Due to the present agricultural systems, the native vegetation in the Brazilian semi-arid region is a mosaic of small areas with different regeneration periods, interspaced with preserved mature caatinga areas. The areas in the initial regeneration stages are dominated by nodulating legume species, while the mature caatingas have small populations of these species. In spite of being an essential nitrogen source to the land ecosystems, the importance of biological N fixation (BNF), through the symbiosis of legume species and bacteria belonging to the rhizobia group, along the process of vegetation regeneration of caatinga areas is not well established. The objective of this study was to determine the occurrence and efficiency of native bacteria populations in the nodules of legume plants grown in soil collected from areas with different caatinga regeneration periods (4, 19, 41 and > 60 years) after being used as pasture. Two greenhouse experiments were established, using soil collected in random spots from three plots in each of these regeneration areas, located in Fazenda Tamanduá. Santa Terezinha municipality, Paraíba state. In the first experiment, culture characteristics and the diversity and efficiency of nodule forming bacteria populations were determined, using cowpea as the trap plant. In the second experiment, the occurrence and efficiency of these bacteria were determined, using native nodulating legume species (Mimosa tenuiflora, Piptadenia stipulacea, Anadenanthera colubrina) as trap plants. In both experiments, the efficiency of the populations was evaluated by the shoot and nodule biomass production and by the N concentration and fixation (15N abundance technique) of the legume plants. The data were submitted to analysis of variance and the averages compared by the Tukey test, considering each regeneration period as a fixed treatment. The results indicate that in regenerating caatinga areas there is an ample populatin of bacteria able to nodulate cowpea, a promiscuous species, and also the native M. tenuiflora species. The population of A. colubrina and P. stipulacea nodulating bacteria is more restricted, leading to low nodulation and absence of N fixation. The period of caatinga regeneration influenced the bacteria populations when cowpea was used as the trap. Differences in culture characteristics (media pH and mucous production) and nodulation were observed. The symbiotic N fixation contributed to the N content of M. tenuiflora grown in soil from all the different regeneration areas, reaching up to 86% of the N content of the plants.

Mots clés  : Mimosa tenuiflora ; Piptadenia stipulacea ; Anadenanthera colubrina ; Vigna unguiculata ; Leguminosa ; Caatinga ; Legume

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Page publiée le 18 décembre 2015, mise à jour le 24 juillet 2017