Nitrogenase activity on the roots of tropical forage grasses

Nitrogen Fixation (Acetylene Reduction) by Rhizosphere Sediments of the Eelgrass Zostera marina

“…Nonetheless, a number of investigators have resorted to long term (days) assays in order to demonstrate NZ fixation. Extended lag periods before the detection of nitrogenase activity have been reported for intact rhizosphere sediments and excised roots in seagrass (Patriquin and Knowles, 1972), Spartina alterniflora (Patriquin and Denicke, 1978;Dicker and Smith, 1980a), and mangrove (Zuberer and Silver, 1978) communities, as well as in terrestrial systems (Dobereiner et al, 1972;Day et al, 1975). This phenomenon has variously been attributed to substrate limitation (Day et al, 1975) and 0, inactivation (Patriquin, 1978) of nitrogenase.…”

“…Extended lag periods before the detection of nitrogenase activity have been reported for intact rhizosphere sediments and excised roots in seagrass (Patriquin and Knowles, 1972), Spartina alterniflora (Patriquin and Denicke, 1978;Dicker and Smith, 1980a), and mangrove (Zuberer and Silver, 1978) communities, as well as in terrestrial systems (Dobereiner et al, 1972;Day et al, 1975). This phenomenon has variously been attributed to substrate limitation (Day et al, 1975) and 0, inactivation (Patriquin, 1978) of nitrogenase. Remedies have therefore included overnight preincubation (Day et al, 1975;Teal et al, 1979), extended assay (Patriquin and Knowles, 1972;Dicker and Smith, 1980a) and substrate additions in experiments intended to evaluate in situ rates of nitrogen fixation.…”

History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

“…This medium, containing starch or glycerol as a carbon source and calcium carbonate, when inoculated with small pieces of washed roots from gramineous plants gave rise to the development of an abundant pellicle with high nitrogenase activity. However, it was not possible to isolate and identify the predominant bacteria due to the difficulties in growing the organisms on plates containing nitrogen-free medium, even under low oxygen levels (Döbereiner 1973 (Döbereiner and Day 1975). In addition, the authors suggested that this bacterium was responsible for the high ARA rates detected.…”

“…Studies on the localization of S. lipoferum in roots of D. decumbens, using the tetrazolium reduction technique, showed that the bacteria were mostly found in the inner cortex layer. This led to the suggestion that S. lipoferum was an intermediate between bacteria involved in the rhizospheric association and the legume symbiosis (Döbereiner and Day 1975).…”

“…The strategy used to solve this problem was to maintain the root samples in flasks containing water and then substitute it with nitrogen gas in the laboratory. The flasks were incubated overnight at a low oxygen level before the injection of 10% of acetylene (Abrantes et al 1976a (Day et al 1975). Soil temperature (Abrantes et al 1976b) and the level of ammonia in the soil (Neves et al 1976) also interfered with the nitrogenase activity.…”