Our knowledge of the biochemistry and biophysics of dinitrogen fixa tion has developed rapidly in the 15 years since the first N2-fixing enzyme system was successfully extracted from a bacterium. This peri od has produced a literature that now describes the N2 fixation reac tion and the nitrogenase enzyme itself in sophisticated terms, though a detailed reaction mechanism at the chemical level has not yet emerged. It is the purpose of the present monograph to present an in-depth re view, analysis, and integration of this research as is possible with a non-contributed publication and to relate this work to considera tions of N2 fixation that reach beyond the confines of the biochem ist's laboratory. The first section is directed as much toward the general science read er as toward the specialist. It covers the agricultural origins of man's interest in N2 fixation and also pertinent areas of taxonomy, physiology, and evolution. Ecological aspects of the subject include a comprehensive evaluation of the nitrogen cycle leading to a sub stantially greater estimate of the rate of global N2 fixation than previous ones. The treatment is of a survey fashion, in part to pro vide a general over-view of N2 fixation and in part to provide context for the biochemistry and biophysics that follow in the second section.

During the past three decades there has been a large amount of research on biological nitrogen fixation, in part stimulated by increasing world prices of nitrogen-containing fertilizers and environmental concerns. In the last several years, research on plant--microbe interactions, and symbiotic and asymbiotic nitrogen fixation has become truly interdisciplinary in nature, stimulated to some degree by the use of modern genetic techniques. These methodologies have allowed us to make detailed analyses of plant and bacterial genes involved in symbiotic processes and to follow the growth and persistence of the root-nodule bacteria and free-living nitrogen-fixing bacteria in soils. Through the efforts of a large number of researchers we now have a better understanding of the ecology of rhizobia, environmental parameters affecting the infection and nodulation process, the nature of specificity, the biochemistry of host plants and microsymbionts, and chemical signalling between symbiotic partners. This volume gives a summary of current research efforts and knowledge in the field of biological nitrogen fixation. Since the research field is diverse in nature, this book presents a collection of papers in the major research area of physiology and metabolism, genetics, evolution, taxonomy, ecology, and international programs.

This book provides an introductory-level survey of biological nitrogen fixation, covering the role of the process in the global nitrogen cycle as well as its biochemistry, physiology, genetics, ecology, general biology and prospects for its future exploitation.

This book discusses the association that exists between plants and their most important dietary component, nitrogen. The author combines ecological, physiological and biochemical approaches to provide the reader with an overall view of nitrogen in the biosphere and a specific view of nitrogen processing in plants. The processes which make up the nitrogen cycle, including mineralization, immobilization by microbes and nitrification, are discussed and the losses and gains of combined nitrogen from and to the cycle. The part which plants play in this cycling, by their processing of inorganic nitrogen into compounds which are required by plants and animals alike, and the chemistry and production of those compounds, is also covered. Transport of nitrogen compounds within the plant, and the fate of these compounds, is discussed. The final chapter considers the part which humans play in the cycling of nitrogen, with special reference to the nitrogen fertilizers used in agriculture.

The nitrogen-fixing organisms. Free-living heterotrophic nitrogen-fixing bacteria. Nitrogen-fixing bacteria in the rhizosphere. Nitrogen fixation in the phyllosphere. Photosynthetic bacteria. Blue-gree algae. Associations with blue-green algae. Root-nodule symbioses with rhizobium. Root-nodulesymbioses withactinomycete-like organisms. Development of root-nodule symbioses. Root-nodule morphogenesis. Formation and function of bacteroids. The endophytes of the root nodules in nonleguminous plants. Leghemoglobin. Environmental effects on nodulation and symbiotic nitrogen fixation. Putative nitrogen fixation in other symbioses. The nitrogen-fixing system. The enzyme system. Genetics of N2-fixing organisms.

This self-contained volume covers fundamental and applied aspects of nitrogen-fixation research. The book describes milestones in the discovery of the associative and endophytic nitrogen-fixing bacteria found involved with cereal crops, forage grasses, and sugar cane. It provides a comprehensive overview of their phylogeny, physiology, and genetics as well as of the biology of their association with their host plants, including tools for in situ localization and population-dynamics analysis. Also included are chapters describing the functions required for a bacterium to be competent and competitive in the rhizosphere, and analysis of associations of cyanobacteria with fungi, diatoms, bryophytes, cycads, Azolla, and Gunnera.

Inorganic Nitrogen in Plants and Microorganisms summarizes new experimental data, ideas and conclusions on the whole metabolic spectrum: - transport through the cell membranes, - the distribution within plant organs, - nitrate and nitrite reduction with their complicated genetic and physiological regulation, - the assimilation of ammonium and dinitrogen. Short reviews cover the dissimilatory reduction of the various inorganic nitrogen intermediates by bacteria, genetic regulation, and ecological and environmental problems. Inorganic Nitrogen in Plants and Microorganisms will help readers understand recent developments in the field of inorganic nitrogen uptake and metabolism.

The Indian Nitrogen Assessment: Sources of Reactive Nitrogen, Environmental and Climate Effects, and Management Options and Policies provides a reference for anyone interested in Reactive N, from researchers and students, to environmental managers. Although the main processes that affect the N cycle are well known, this book is focused on the causes and effects of disruption in the N cycle, specifically in India. The book helps readers gain a precise understanding of the scale of nitrogen use, misuse, and release through various agricultural, industrial, vehicular, and other activities, also including discussions on its contribution to the pollution of water and air. Drawing upon the collective work of the Indian Nitrogen Group, this reference book helps solve the challenges associated with providing reliable estimates of nitrogen transfers within different ecosystems, also presenting the next steps that should be taken in the development of balanced, cost-effective, and feasible strategies to reduce the amount of reactive nitrogen. - Identifies all significant sources of reactive nitrogen flows and their contribution to the nitrogen-cycle on a national, regional, and global level - Covers nitrogen management across sectors, including the environment, food security, energy, and health - Provides a single reference on reactive nitrogen in India to help in a number of activities, including the evaluation, analysis, synthesis, documentation, and communications on reactive nitrogen