Current Perspectives In Nitrogen Fixation

Plenary discussion; Chemistry of nitrogen fixation; Mechanism of nitrogenase action; Energetics of nitrogen fixation; Photosynthesis and nitrogen fixation; Plenary discussion; Genetics of symbiotic microorganisms; Molecular genetics of nitrogen fixation; Regulation of nitrogenase activity; Host determinants in symbiotic nitrogen fixation; Microbiology and physiological ecology of diazotrophs.

This volume discusses the most recent advances in biological nitrogen fixation, with chapters written by experts on the ecology, physiology, biochemistry and genetics of biological nitrogen fixation.

Sustainability has a major part to play in the global challenge of continued development of regions, countries, and continents all around the World and biological nitrogen fixation has a key role in this process. This volume begins with chapters specifically addressing crops of major global importance, such as soybeans, rice, and sugar cane. It continues with a second important focus, agroforestry, and describes the use and promise of both legume trees with their rhizobial symbionts and other nitrogen-fixing trees with their actinorhizal colonization. An over-arching theme of all chapters is the interaction of the plants and trees with microbes and this theme allows other aspects of soil microbiology, such as interactions with arbuscular mycorrhizal fungi and the impact of soil-stress factors on biological nitrogen fixation, to be addressed. Furthermore, a link to basic science occurs through the inclusion of chapters describing the biogeochemically important nitrogen cycle and its key relationships among nitrogen fixation, nitrification, and denitrification. The volume then provides an up-to-date view of the production of microbial inocula, especially those for legume crops.

This volume constitutes the proceedings of an international meeting held from June 28 to July 1, 1981, at Zif, Zentrum far Interdisziplin~re Forschung an der Universit~t Bielefeld, West Germany. The meeting was one of a continuing series organized through Zif on topics which transcend the boundaries of the traditional academic disciplines. The almost exponentially growing area of nitrogen fixation research fits this criterion completely. It is, however, so broad that we oriented and focused the meeting on just the chemical, biochemical, and genetic aspects to maximize the interaction among the participants and to produce a volume which would serve as a reference source for the involved researcher, the newly interested scientist and those with a more casual interest. The meeting was generously supported by Zif, the Westf~lisch Lippische Universit~tsgesellschaft, and the Fonds der Chemischen Industrie. We sincerely thank these organizations for their generosity and interest and for recognizing the importance of nitrogen fixation research for the future of mankind.

Agriculture in the industrial world has gone A common interest of the contributors is increas through dramatic changes over the past decades. ing the understanding of the turnover of carbon Mechanization in combination with high inputs of and inorganic nutrients in terestrial ecosystems. fertilizers and pesticides has turned deficits of agri The authors approach this topic from different cultural products into surplus. Over the same directions depending on their interests and ex period we have experienced increased environment pertise. Difficulties are identified in the quantifica al problems in both the atmosphere and our water tion of below-ground production where death and resources, which have been associated with the re-growth, if incorporated into the calculations, changes in management practices. can change production figures considerably as Concern about the potential pollution by compared to values derived from "peak" estimates. nitrogen fertilizers as well as the low utilization The role of root-derived carbon is investigated in efficiency of applied nitrogen by plants has created relation to nutrient competition between roots and a need for a better understanding of nitrogen microorganisms, the cost of N2 fixation and the cycling in the plant-soil-water system. To achieve decomposition of organic nitrogen. Mycorrhizae this, it is neccessary to study process interactions use root-derived carbon and their roles in phos and process regulation in an ecosystem context. phorus conservation and in supplying nutrients to During the last decade many ecosystem studies the host are exemplified.

Proceedings of a Workshop, ICARDA, Syria, April 14-17, 1986.