Nodules produced on legume roots by root-nodule bacteria provide the major nitrogenous input into natural and agricultural systems worldwide. This book provides an in-depth and up-to-the-minute analysis of what is known about this symbiosis, its origins, the process of nodule formation and development, and the biochemistry and genetics of nodular nitrogen fixation. It also reviews the physiology of the root-nodule bacteria themselves, their ecology in both natural and agricultural systems, and how we can introduce new legumes along with the bacteria they require. This book is recommended for scientists working with root nodule bacteria or host legumes, agronomists, forestry scientists, and soil scientists.

This book is the stand-alone final volume of a comprehensive series covering the basic and applied science relating to nitrogen fixation. It addresses the most important nitrogen-fixing symbiosis of all that between legumes and their root-nodule bacteria and therefore deals with the properties and behaviour of both macro- and micro-symbiont. The coverage is comprehensive, beginning with the extent of the symbiosis and how it may have arisen in the geological past. It considers how legumes select the root-nodule bacteria they allow to form nodules on their roots and the intricate series of signals to be exchanged between legume and bacteria for infection to occur. The immense progress in understanding the genetic systems in the bacteria necessary for nodulation is now being replicated in a rapidly increasing understanding of the required systems in the legumes. The cell biology of the processes of both infection and nodule development is analysed and leads to a parallel assessment of the biochemical processes in carbon and nitrogen metabolism required for successful nitroogen fixation by the symbiotic bacteroid. Attention is given to the ways in which the nodule has solved the conundrum of providing enough O2 for energy generation to drive nitrogen fixation without either inactivating the O2-sensitive nitrogenase or creating damaging reactive oxygen species. The volume also covers the basic physiology of the variety of root-nodule bacteria infecting legumes, as well as looking at the renewed controversy about the chemical form(s) of nitrogen exported to the legume. Successful exploitation of the legume symbiosis in agriculture, horticulture, and forestry demands an understanding of the ecology of the root-nodule bacteria particularly what makes for a successful inoculant strain for legume introduction to agricultural systems. Then, there is a requirement for inoculation technology to both successfully deliver viable bacteria to the root surface and facilitate nodulation. These practical aspects are thoroughly covered in the volume, with a final chapter assessing how the massive amount of recent information can be exploited in matching host and microsymbiont for the wide variety of environments in which they are needed in our production systems."

A special meeting of the Royal Society in London in 1986 marked the centenary of the first demonstration of nitrogen fixation. Currently the subject is of great practical importance because the use of nitrogenous fertilizers has resulted in unacceptable levels of water pollution; also these fertilizers are becoming steadily less economic both in cash terms and in utilization of fossil fuels for their manufacture. The number of papers published and the frequency of national and international meetings to discuss research into nitrogen fixation have both increased steadily during the 1970s and 1980s. Specialist monographs and review papers are often too detailed to be of real use to undergraduates in biology or related areas such as agriculture and forestry, and even for graduates and research workers newly entering the field of nitrogen fixation. For people in these categories, the senior author wrote The Biology of Nitrogen-fixing Organisms published by McGraw Hill in 1979. This book has similar aims. It incorporates new findings that have not only resolved some of the uncertainties reported in that earlier text hut, more importantly, it reflects the influence on the subject of recent developments in biochemistry, molecular biology, genetic engineering and other biotechnologies. We have devoted more attention to quantitative aspects of the subject, but unfortunately the many practical difficulties for accurate field assessment of nitrogen fixation and its contribution to nitrogen cycles means that many assessments are either in contlict with each other or must be accepted as tentative.

Many people learn the rudiments of the nitrogen cycle while at school. However, the details of the various processes in the cycle and their magnitude are still not fully understood. Some of them are of great current interest, for example use of nitrogen fixing crops to feed the increasing world population and the problems of pollution of groundwaters by nitrates. While some of the world needs to fix nitrogen, other parts are using natural processes of denitrification (forming nitrogen gas) as a way of getting rid of waste from humans and intensively farmed animals.

This book describes the general processes of the nitrogen cycle and then takes examples to show how the cycle is modified for particular ecological and geographical situations. They are drawn from all major areas of the world and the impact of man via agriculture, forestry and fuel combustion is discussed. Numerous references are included. The book provides a background for all those whose specialist interests interact with nitrogen cycling, whether they are involved in research or have the task of attempting to manage the environment.

Collection of 16 papers addressing various aspects of the nitrogen economy of legumes, including nodulation and its evolution, the phytochemistry, costs and benefits of nitrogen compounds, and the relationship between legumes and their predators.