Topic
Nitrogen fixation
About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.
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TL;DR: Evidence is provided that non-heterocystous blue-green algae may fix nitrogen if grown under low oxygen tension, so that heterocysts are not essential for nitrogen fixation in these algae.
Abstract: THE function of heterocysts in blue-green algae has been controversial for some time; there are indications that these enlarged cells are the site of nitrogen fixation1,2. But non-heterocystous blue-green algae may fix nitrogen if grown under low oxygen tension3, so that heterocysts are not essential for nitrogen fixation in these algae. According to a current hypothesis4, in aerobic conditions nitrogen fixation is confined to heterocysts, while in anaerobic or semi-anaerobic conditions the vegetative cells fix nitrogen as well. We have evidence to support this view.
69 citations
TL;DR: Tn5 mutational analysis is most powerful as a tool for the initial localization of important genes or gene clusters, and for preliminary analyses of organization, and other approaches are required to further refine the identities and patterns of the regulation of such genes
Abstract: Publisher Summary This chapter focuses on the Tn5 mapping of Rhizobium nitrogen fixation genes. Gram-negative bacteria of the genus Rhizobium have the ability to infect legumes and induce the formation of symbiotic nitrogen-fixing root nodules. Differentiated bacterial forms within these nodules (bacteroids) use photosynthetically generated carbon compounds provided by the plant to convert atmospheric nitrogen to ammonia. The techniques used for creating symbiotically defective Tn5 mutants in Rhizobium are generalized mutagenesis, plasmid mutagenesis, and site-directed mutagenesis. Tn5 mutational analysis is most powerful as a tool for the initial localization of important genes or gene clusters, and for preliminary analyses of organization. The chapter also discusses the various benefits of Tn5 mutagenesis and the marker exchange procedure. Other approaches are required to further refine the identities and patterns of the regulation of such genes.
69 citations
TL;DR: The relative growth rates of stressed plant parts declined initially but were subsequently higher than those of control for a period, suggesting that the plants tended to adapt to unfavourable environment even while being stressed.
Abstract: The effects of salt stress on growth, nodulation, and nitrogen accumulation in cowpea (Vigna sinensis) and mung beans (Vigna aureus) were studied in sand culture.
Salinity (NaCl) retarded the growth of leaves, stem and roots of both the crops. Root growth of mung beans was more sensitive to the increase in salt stress than that of cowpea. The relative growth rates of stressed plant parts declined initially but were subsequently higher than those of control for a period, suggesting that the plants tended to adapt to unfavourable environment even while being stressed. The total nodule number, weight and nitrogen content per plant decreased due to salt treatment, which interfered with the initiation of nodules but not with their further development. There was a considerable fall in the nitrogen fixation efficiency of mung beans under saline environment; it was not so in cowpea.
69 citations
TL;DR: A high bacterial diversity and abundances of C and N decomposing bacteria in lowland rice rhizosphere were found under e-CO2T, which could be explored further for their specific role in nutrient cycling, sustainable agriculture and environment management.
69 citations
TL;DR: In this paper, the authors reconstructed major parts of the nitrogen cycle in the rhizosphere soil/root system of Leucanthemopsis alpina (L.) Heathwood: as well as the corresponding bulk soil by quantifying functional genes of nitrogen fixation (nifH), nitrogen mineralisation (chiA, aprA), nitrification (amoA AOB, amoA AOA) and denitrification (nirS, nirK and nosZ) in a 10-year and a 120-year ice-free soil of the Damma glacier
Abstract: Glacier forefields are an ideal playground to investigate the role of development stages of soils on the formation of plant-microbe interactions as within the last decades, many alpine glaciers retreated, whereby releasing and exposing parent material for soil development. Especially the status of macronutrients like nitrogen differs between soils of different development stages in these environments and may influence plant growth significantly. Thus, in this study, we reconstructed major parts of the nitrogen cycle in the rhizosphere soil/root system of Leucanthemopsis alpina (L.) HEYWOOD: as well as the corresponding bulk soil by quantifying functional genes of nitrogen fixation (nifH), nitrogen mineralisation (chiA, aprA), nitrification (amoA AOB, amoA AOA) and denitrification (nirS, nirK and nosZ) in a 10-year and a 120-year ice-free soil of the Damma glacier forefield. We linked the results to the ammonium and nitrate concentrations of the soils as well as to the nitrogen and carbon status of the plants. The experiment was performed in a greenhouse simulating the climatic conditions of the glacier forefield. Samples were taken after 7 and 13 weeks of plant growth. Highest nifH gene abundance in connection with lowest nitrogen content of L. alpina was observed in the 10-year soil after 7 weeks of plant growth, demonstrating the important role of associative nitrogen fixation for plant development in this soil. In contrast, in the 120-year soil copy numbers of genes involved in denitrification, mainly nosZ were increased after 13 weeks of plant growth, indicating an overall increased microbial activity status as well as higher concentrations of nitrate in this soil.
69 citations