Rhizobium species involved in root nodule formation on legume plants are one of the best known groups of micro organisms. The Rhizobium legume symbiosis continues to be of strategic importance particularly in the context of food production. As the world population grows, it is also neces sary to have new developments taking place in crop improve ment. The development and application of new technologies in biological sciences over the past number of years have made the entire area of plant-microbial interaction an exciting and challenging research area to be involved in. In view of the importance of symbiotic nitrogen fixation, it is not surpris ing that it still represents one of the priority areas for commercial development in agricultural biotechnology. Since this symbiosis involves an association between procaryotic and eucaryotic partners, it requires of necessity a co-ordinated and interdisciplinary approach. It was in this spirit that this international conference was organised. The scientific programme was designed to focus on physio logical limitations affecting symbiotic nitrogen fixation and the potential for overcoming such limitations using genetic technologies. Participants were drawn from contractants of the EEC DGVI "Energy in Agriculture" nitrogen fixation prog ramme. The scientific programme was also supplemented with invited scientists from Europe and North America to provide appropriate expertise on the various conference topics.

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.

With the demonstration of the "triple response" in plants by Neljubow at the turn of the century, ethylene has been identified as a substance specifically affecting plant growth. Yet it took a few more decades to show that ethylene is a naturally occurring product of plants having all the characteristics of a phytohormone. Ever since much effort has been devoted to a wide variety of physiological and biochemical problems relevant to ethylene. A first meeting was organized in Israel in 1984 to bring together many people active in this rapidly expanding field of experimental research. It is the aim of the present symposium to provide once more a forum at which researchers might expose and comment progress in their work over the last few years. Speakers were invi ted and their contri buti ons ordered ina number of sessions, each of which was centered on a particular topiC. Much of the benefit came from ensuing discussion sessions which were conducted with much competence and expertise by Anderson, Ben-Arie, Goren, Morgan and Osborne. All of these colleagues are recognized leaders in ethylene research today and the organizers owe a very special gratitude to them for their substantial contribution to the programme. It is well to remember the friendly atmosphere, so essential to the success of the whole meeting and so much enjoyed by every partiCipant. Prompt publi ca tion of the papers was made possi ble by the camera-ready procedure offered by the publisher.

China was the first country to use cytoplasmic male sterility to develop hybrid rice for commercial use in 1973. In 1986 more than 8 million hectares of hybrid rice were planted in China, which is one fourth of the total rice area and produces one third of the total rice in the country. Hybrids usually out yield the leading commercial varieties by -20-30%, giving an average yield advantage of 1 to 1. 5 t/ha, because of their better morphological traits, higher physiological efficiency, better resistance to major diseases and insects, and wide adaptability to various agro-ecological stresses. IMPROVEMENT OF HYBRID RICE A. Mutation techniques Almost all of the cultivated F1 rice hybrids in China are developed from cytoplasmic male sterile and restorer lines. According to surveys made in recent years, more than 30 sources of cytoplasmic male sterility in rice can be identified, among which only six are being commercially used (Table 1). Wild rice with aborted pollen (WA) cytosterility system is the most popular one in use to develop male sterile lines (MS line) in China. The main technique available for developing stable MS lines is sUbstitution backcrossing of the genome of one species into alien cytoplasm of another. Sufficient backcrosses are required to eliminate all nuclear genes derived from the cytoplasm donor species. A number of studies have shown that using interspecies crosses, such as the cross of wild rice (Q. perennis, Q. sativa, f.

The core of the text is aimed at the research worker in the field of nitrogen fixation, but, despite its specialisation, does not lose the emphasis on teaching, both as a direct reference book and as a backbone for a graduate course on the subject.The closing part of the book includes a subject index and a glossary of terms. The latter was included not for the expert, for whom many of the definitions will be too general, but for the newcomer; the author hopes that the quick survey of key terms will help in the reading of this book.

Our requirement for plant breeders to be successful has never been greater. However one views the forecasted numbers for future population growth we will need, in the immediate future, to be feeding, clothing and housing many more people than we do, inadequately, at present. Plant breeding represents the most valuable strategy in increasing our productivity in a way that is sustainable and environmentally sensitive. Plant breeding can rightly be considered as one of the oldest multidisciplinary subjects that is known to humans. It was practised by people who first started to carry out a settled form of agriculture. The art, as it must have been at that stage, was applied without any formal underlying framework, but achieved dramatic results, as witnessed by the forms of cultivated plants we have today. We are now learning how to apply successfully the results of yet imperfect scientific knowledge. This knowledge is, however, rapidly developing, particularly in areas of tissue culture, biotechnology and molecular biology. Plant breeding's inherent multifaceted nature means that alongside obvious subject areas like genetics we also need to consider areas such as: statistics, physiology, plant pathology, entomology, biochemistry, weed science, quality, seed characteristics, repro ductive biology, trial design, selection and computing. It therefore seems apparent that modern plant breeders need to have a grasp of wide range of scientific knowledge and expertise if they are successfully to a exploit the techniques, protocols and strategies which are open to them.

Respiration in plants, as in all living organisms, is essential to provide metabolic energy and carbon skeletons for growth and maintenance. As such, respiration is an essential component of a plant’s carbon budget. Depending on species and environmental conditions, it consumes 25-75% of all the carbohydrates produced in photosynthesis – even more at extremely slow growth rates. Respiration in plants can also proceed in a manner that produces neither metabolic energy nor carbon skeletons, but heat. This type of respiration involves the cyanide-resistant, alternative oxidase; it is unique to plants, and resides in the mitochondria. The activity of this alternative pathway can be measured based on a difference in fractionation of oxygen isotopes between the cytochrome and the alternative oxidase. Heat production is important in some flowers to attract pollinators; however, the alternative oxidase also plays a major role in leaves and roots of most plants. A common thread throughout this volume is to link respiration, including alternative oxidase activity, to plant functioning in different environments.