SUMMARYThe effects on different vegetal parameters of asymbiotic nitrogen-fixing bacteria isolated from the rhizosphere of Pinus patula were studied under greenhouse conditions, in experiments designed for statistical analysis using these forest specie seedlings. This research also examined the interactions of ectomycorrhizal fungus Suillus luteus and the microorganism isolates in P. patula, as well as the nitrogenase activity in these bacteria by acetylene reduction assay. The free nitrogen-fixing bacteria Azotobacter chroococcum, Bacillus macerans, Enterobacter agglomerans and Pseudomonas sp., were isolated of the rhizosphere of P. patula. Their maximum acetylene-reducing values were 120, 18.7, 100, 120 nmol ethylene/tube respectively. Results showed that the best plant growth and nitrogen uptake in the in vivo test in P. patula with these microorganisms and S. luteus were observed with A. chroococcum. According to the longitudinal root cuts in the treatments using S. luteus with A. chroococcum, B. macerans, E. agglomerans, or Pseudomonas sp., the fungus with the agglutinated bacteria was showed around the mycorrhizal root surface only in the S. luteus and B. macerans treatment, but the mycorrhizal infection percentage was low. The inoculation with nitrogen fixing bacteria stimulated longitudinal growth and nitrogenous nutrition of P. patula.Key words: asymbiotic, ectomycorrhizas, nitrogen-fixation. RESUMENEl efecto de bacterias fijadoras de nitrógeno asimbióticas aisladas de la rizósfera de Pinus patula sobre diferentes parámetros vegetales fue estudiado bajo condiciones de invernadero, usando plántulas de esta especie forestal. Esta investigación también examinó la interacción entre el hongo ectomicorrízico Suillus luteus y los microorganismos aislados en P. patula, así como la actividad de la nitrogenasa por el ensayo de reducción de acetileno. De la rizósfera de P. patula se aislaron las bacterias fijadoras libres de nitrógeno Azotobacter chroococcum, Bacillus macerans, Enterobacter agglomerans y Pseudomonas sp. Los valores máximos de reducción de acetileno presentados por estas bacterias fueron 120, 18, 7, 100, 120 nmol etileno/tubo, respectivamente. Los resultados en el ensayo in vivo de P. patula con estos microorganismos y S. luteus mostraron que el mejor crecimiento de las plantas y la captación de nitrógeno se observaron con A. chroococcum. Al observar los cortes longitudinales de raíz de los tratamientos usando S. luteus con las diferentes bacterias (A. chroococcum, B. macerans, E. agglomerans y Pseudomonas sp.) sólo el tratamiento con S. luteus y B. macerans presentó el hongo con bacterias aglutinadas alrededor de la superficie de la raíz micorrizada, pero el porcentaje de micorrización fue bajo. La inoculación con bacterias fijadoras de nitrógeno estimuló el crecimiento longitudinal y la nutrición nitrogenada de P. patula.Palabras clave: asimbiótico, ectomicorrizas, fijación de nitrógeno.

Composting of the macrophytes Eichhornia crassipes (water hyacinth) and Egeria densa (Brazilian elodea) has been proposed as a final disposal, following their mechanical removal in the lake Fúquene (Ubaté, Cundinamarca). Microorganisms, isolated and selected by antagonism, were evaluated as inoculants to accelerate the composting and to stimulate plant growth. In microbial biopreparations of bacteria, actinomycetes and fungi, maximum amylolytic activities were found of 2,422 U L -1 , 1,744 U L -1 and 1,426 U L -1 , respectively; cellulolytic activities of 233.2 U L -1 , 668 U L -1 and 701.4 U L -1 and proteolytic activities of 660 U mg -1 , 520 U mg -1 and 400 U mg -1 . In test of these biopreparations in windrow composting of aquatic macrophytes waste, the best result was obtained with a concentration of 2%. The assay conducted on seedlings of radish (Raphanus sativus L) under greenhouse conditions (P <0.05), using the following treatments: microbial inoculants, compost inoculated to 2%, pure or mixed with soil (1:1), peat 50% and chicken manure at 33% mixed with soil, showed that actinomycetes stimulated plant growth significantly, as did chicken manure and bacteria. Microbial inoculants role for growth, development and nutrients assimilation in radish, was evident, and also for accelerating polluting macrophytes composting process.

Invasive aquatic plants from Lake Fúquene (Cundinamarca, Colombia), water hyacinth (Eichhornia crassipes C. Mart.) and Brazilian elodea (Egeria densa Planch.) have been removed mechanically from the lake and can be used for edible mushrooms production. The growth of the oyster mushroom (Pleurotus ostreatus) on these aquatic macrophytes was investigated in order to evaluate the possible use of fruiting bodies and spent biomass in food production for human and animal nutrition, respectively. Treatments included: water hyacinth, Brazilian elodea, sawdust, rice hulls and their combinations, inoculated with P. ostreatus at 3%. Water hyacinth mixed with sawdust stimulated significantly fruiting bodies production (P = 3.3 × 10(-7)) with 71% biological efficacy, followed by water hyacinth with rice husk (55%) and elodea with rice husk (48%), all of these have protein contents between 26 and 47%. Loss of lignin (0.9-21.6%), cellulose (3.7-58.3%) and hemicellulose (1.9-53.8%) and increment in vitro digestibility (16.7-139.3%) and reducing sugars (73.4-838.4%) were observed in most treatments. Treatments spent biomass presented Relative Forage Values (RFV) from 46.1 to 232.4%. The results demonstrated the fungus degrading ability and its potential use in aquatic macrophytes conversion biomass into digestible ruminant feed as added value to the fruiting bodies production for human nutrition.

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