This book brings together research into the process of stream acidification and its impact on Welsh surface waters, carried out over the past decade or so. It is perhaps surprising that not until the 1980's was clear evidence of stream acidification assembled. In Wales, concerns over pollution had focused water quality sampling principally on the areas of traditional heavy industry and large urban popula tions served by inadequate sewerage systems and sewage disposal arrange ments. Mistakenly, it had been assumed that, with its prevailing westerly winds, Wales would receive precipitation substantially unpolluted by the industrial and urban emissions from Britain and mainland Europe. Assurance of the high quality of Welsh upland streams, the traditional nursery ground of salmonids, was eroded particularly by studies in the vicinity of Llyn Brianne reservoir in the catchment of the River Tywi of Central Wales. These demonstrated a clear correspondence between the biological quality and fisheries of streams in the catchment and aspects of stream chemistry, par ticularly pH, aluminium and calcium on the one hand, and catchment land use on the other. It is salutary to record that the first signals were of an inexplicable failure of the runs of migratory salmonids into the upper catchment, occupied by the Llyn Brianne reservoir and its influent streams, and the failure to restore the fishery by re-stocking with eggs and fry. Only then did the significance of the recent decline in some other upland lake and reservoir fisheries in Wales become apparent.

It is enough to work on the assumption that all of the details matter in the end, in some unknown but vital way. Edward O. Wilson, Biophilia Advances in knowledge of northern ecology have been so rapid that to undertake a synthesis of all the literature now available would be a major enterprise, perhaps even a life's work, and so it must be considered permissible to fill in a few gaps, follow one's own inclinations, leaving comprehensive syntheses to those willing to undertake them. This is the rubric under which I have written, reporting some of the more interesting data I and others have obtained over the years, often diverging into discussions of plants, soils, climate, and faunal relationships which have perhaps not previously been dealt with extensively, or at least in quite the same way. This is purely intentional, since I find it difficult to summon up the needed enthusiasm, at this late hour, to write on topics which unfortunately for me have little attraction. I have thus written for the pleasure derived from depicting, perhaps at times as something of an impressionist, a fascinating biotic region, a captivating land, a collection of interesting ecological problems, environmental relationships to be discerned in part, perhaps understood to some small degree, perhaps one day to be modeled mathematically. As Leo Szilard once wrote: ': . . to be able to say even this much might be of some value" (Szilard, 1960).

Succession-nothing in plant, community, or ecosystem ecology has been so elaborated by terminology, so much reviewed, and yet so much the center of controversy. In a general sense, every ecologist uses the concept in teaching and research, but no two ecologists seem to have a unified concept of the details of succession. The word was used by Thoreau to describe, from a naturalist's point of view, the general changes observed during the transition of an old field to a forest. As data accumulated, a lengthy taxonomy of succession developed around early twentieth century ecologists such as Cooper, Clements, and Gleason. Now, nearer the end of the century, and after much discussion concerning the nature of vegetation communities, where do ecologists stand with respect to knowledge of ecological succession? The intent of this book is not to rehash classic philosophies of succession that have emerged through the past several decades of study, but to provide a forum for ecologists to present their current research and present-day interpretation of data. To this end, we brought together a group of scientists currently studying terrestrial plant succession, who represent research experience in a broad spectrum of different ecosystem types. The results of that meeting led to this book, which presents to the reader a unique summary of contemporary research on forest succession.

Environmental stresses represent the most limiting factors to agricultural productivity worldwide. Their impact is not only on presently cultivated crops, they are also significant barriers to the introduction of crop plants in noncultivated areas. A significant global problem in the improvement of agriculture is the major variation in annual crop yields due to variations in environmental stresses such as drought, flooding, salinity, and temperature variations. This summary presents current background and research knowledge on all important environmental stresses and their respective influence on plant growth, development and crop yield as well as on biochemical and physiological events within plant tissues in reaction to changing environmental conditions.

It is widely recognized that spiral grain in trees severely reduces the value of sawn timber through warping and loss of strength, and that it also causes problems for other wood uses as diverse as transmission poles or plywood. Yet, paradoxically, there are highly valued grain patterns including wavy and interlocked grain, whose origins in the cambium invite direct comparison with those of spiral grain, so that many authorities believe them to be related phenomena. In recent years this concept has prompted extensive research into the anatomy, genetics, and physiology of all such grain patterns in wood. As a result it has become apparent that tree cambia provide excellent systems through which to study the origins of stem polarity and the complex processes of morphogenetic control in plants. Beside these and other pressing topics for research, the book examines methods of measuring grain deviations, and considers their influence on wood properties, on the economics of timber production, and on wood manufacturing.

This volume summarises the result of an interdisciplinary research programme entitled Rehabilitation of the Atmosphere of the New States of Germany - Effects on Terrestrial Ecosystems'. Before the unification of Germany, emission loads of SO2 and dust particles were up to 18-fold higher in East than in West Germany. However, emission rates have decreased significantly since reunification in 1990, due to the breakdown of a large number of industrial and particularly lignite- fired powerplants and the implementation of clean air technologies. In order to study the effects of these dramatic changes in atmospheric chemistry on terrestrial ecosystems, comprehensive field studies were conducted in pine forest ecosystems along an historic gradient of atmospheric deposition rates in the northeastern lowlands of Germany. The fast and dramatic reduction of dust particle and SO2 emissions offers a unique opportunity to test the role of SO2 and alkaline particle deposition with regard to changes or damage to forest ecosystems and whether the forest stands return to a state of resilience. In this respect, this ecosystem experiment can be looked upon as a roof experiment without a roof.

5. 3. 2 Some facts and figures 177 5. 3. 3 Policy implications 179 5. 4 Tropical moist forest 182 5. 4. 1 Introduction 182 5. 4. 2 History 184 5. 4. 3 Policy considerations 186 5. 4. 4 Policy options 188 5. 5 Farm Forestry 190 5. 5. 1 Introduction 190 5. 5. 2 Types of farm forests 192 5. 5. 3 The dynamics in farm forestry 193 5. 5. 4 Forest policy and farm forestry 194 5. 6 Agroforestry 196 5. 6. 1 Introduction 196 5. 6. 2 History 198 5. 6. 3 Policy aspects 200 5. 7 Rural community development 203 5. 7. 1 Introduction 203 5. 7. 2 Developing countries 203 5. 7. 3 Developed countries 207 References 210 6 INSTITUTIONS AND ADMINISTRATION 213 by Fred Hummel 6. 1 Forest ownership 213 6. 1. 1 State forests 213 6. 1. 2 Forests owned by individuals 214 6. 1. 3 Communal forests 216 6. 1. 4 Co-operative forests 217 6. 1. 5 Forests owned by industry 218 6. 1. 6 Forests owned by institutions 219 6. 1. 7 Policy considerations 220 6. 2 Legislation 221 6. 2. 1 General considerations 222 6. 2. 2 Drafting and reviewing forest legislation 223 6. 2. 3 Specific legal issues (land, production, protection) 225 6. 3 Taxation and incentives 227 6. 3. 1 Taxation 228 6. 3. 2 Incentives 230 6. 4 Education and training 233 IX 6. 4.

A large proportion of the world's population is directly involved in agriculture, many of them as small businessmen. Each of these businessmen applies his skill and resources day in, day out, to produce food and raw materials. All of them to a greater or lesser extent operate in a changing environment to which they must adjust. Many aspects of the environments of agricultural institutions by the decisions of other people; in the marketplace, are influenced in ancillary industries, in research institutes and places of learning and in Government organisations that create and implement agricultural policy. Improvements in the quality of decisions made by those who manage all the various parts of the agricultural system can have a major impact on the quality of everyone's life. How can such improvements be achieved? This book is based on the belief that a grasp of concepts or principles can add a great deal to the understanding and management of agricultural systems of all kinds. It therefore attempts to transmit some ideas and observations about management in agriculture. It is not about techniques nor about the particular problems of a specific type of agriculture. Its aim is to promote reflection, thought and discussion by professional people whose decisions influence the performance of agricultural VII V11l PREFACE systems. As such, the book attempts to convey only the -central concepts of management in as simple a language as possible.

The Plant Root and the Rhizosphere was a major topical feature of the first International Symposium on Factors Determining the Behavior of Plant Pathogens in Soil held at the University of California, Berkeley in 1963. The symposium was edited by K. F. Baker and W. C. Snyder and published under the title Ecology of Soil-Borne Plant Pathogens. Since that time, several other international efforts, either on the root-soil interface specifically or on topics relating to the root environment, have provided"a wealth of valuable information basic to promoting the culture of healthier, more productive plants. For the writing of this book, inspiration has come, in large part, from 10 years of cooperative rhizosphere research in association with leading scientists participating in a regional effort within the southern United States. We have attempted to bring together in this work the major aspects of rhizosphere research and the principles of rhizosphere ecology for the benefit of developing young scientists and technologists, as well as for the established professional researcher and teacher. A prime objective and hope is that this volume might generate ideas that will bring forth new approaches and methodology leading to further advances in our understanding of rhizosphere interactions and their implications for agriculture. ' Because of the enormous complexity of the chemical, physical, and microbiological environment of roots, the methods used by various workers are rarely standardized, but must be devised or modified for each experiment.

Neurochemical Techniques in Insect Research properly emphasizes the insect. It only scratches the surface of the exploding repertoire of general neuro chemical techniques that can be applied to insect research in 1985. But it al so presents the advantages of using insects for studying certain biological questions that are approachable by neurochemical techniques. Even more so, it summarizes the long list of unique problems encountered in attempting to study insects by neurochemical techniques. As in other volumes of this series, the contributors to this volume are the authorities in the field. They themselves have developed much of the material presented. Thus the sum effort provides a true description of the state of the art; and, pleasantly, it does so in a very complete and clear manner. Readers of this series will not need to be reminded that, despite the fact that vertebrates make up only about 3% of all animal species, research in in vertebrates such as insects has lagged behind that on vertebrates, at least in the neurochemistry area; the relative simplicity and large cell size of the in sect nervous system has always provided incentive for work in neurophysiol ogy and neuroanatomy. Toxicology interests will always stimulate a certain amount of work on insect neuropharmacology, and insects are extremely suitable for several areas of toxin research. Last but not least, the insects are beautiful organisms for which the applications of genetics can be made to the study of nervous system function."

By their powers of reason scientists will be able to extract from nature the answers to their questions. From: Critique of Pure Reason, 1781 Immanuel Kant (1724-1804), German Philosopher History is a composite of stories. The history of the biological disciplines has been written by all those who opened the gates of new knowledge by generating ideas and the experiments to support them. Previous authors have attempted various approaches to the history of virology, as is reflected in the numerous books and book-series issuing from the publishing houses. This volume is an attempt at a compre hensive yet compact survey of virology, which has meant penetrating the rigid limits of the separate disciplines of biology in which virologists have worked. Writing this history of experimental virology was really a search for the origins and for vital signposts to portray the wide scope of the knowledge attained thus far. This was done in com plete awareness of the fact that every presentation depends heavily upon the perspective of the observer, and of necessity communi cates only a part of the whole. The present scientific story hopes to recount the most important knowledge achieved during this past century - the first century of the exciting developments in virology."

Rapid progress in the field of organophosphate compounds has made this new edition necessary. Particular attention has been paid to new developments in biologically active products as this is probably of greatest interest to practical chemists. I have therefore updated the chapter on chemistry and, in connection with this, rewritten the chapter on metabolism. I should especially like to thank Professor Dr. HELLMUT HOFFMANN for his constant encouragement and interest in my work and for many fruitful discus sions. The co-author to the 1st edition, Dr. KARL-JULIUS SCHMIDT, died suddenly on November 21, 1980. I treasure the memory of a valued colleague of many years standing. Elberfeld, January 1982 CHRISTA FEST VII Preface to the First Edition Our intention has been to provide a short introduction to the chemistry and mode of action of insecticidal phosphoric acid compounds, with particular ref erence to the relationship between structure and activity. The yearly produc tion of these pesticides is now approaching 100,000 tons and thus offers an im portant example of applied research. If, however, one examines the historical development of these compounds, it is apparent that this was preceded by a hundred years of pure chemistry of phosphorus."

The development of powerful new techniques and refmements of tech niques in molecular genetics in recent years, and the surge in interest in biotechnology based on genetic methods, have heralded a new golden age in molecular genetics, and stimulated in diverse disciplines much interest in the technologies themselves and their potential uses in basic and applied biomedical sciences. Although some excellent specialist laboratory manuals (especially the Cold Spring Harbor Laboratory manuals by I. H. Miller; R. W. Davies et al.; and T. Maniatis et al. ) on certain chapters of molecular genetics exist, no general text that covers a broad spectrum of the sub ject has thus far been published. The purpose of this manual is to pre sent most, though of necessity not all of the important methods of molecular genetics, in a series of simple experiments, many of which can be readily accomplished by the microbiologist, biochemist or biotechnologist that has had only limited exposure to genetics. The remainder of the experiments require either greater familiarity with the subject, or guidance by someone with such experience. The book should, therefore, not only enable individuals to acquire new proce dures for ongoing projects, but also serve as a basis for the teaching of molecular genetic techniques in formal predoctoral and postdoctoral laboratory courses."

will probably be clarified by the continued cooperative efforts of scientists such as those in the group that met in Berlin last September. The staff of Dahlem Konferenzen is responsible for making the meeting of this group memorably pleasant and pleasantly mem- orable. Dr. Bernhard's gifts of charm, organizational skill, and administrative toughness assured that the conference was run elegantly, smoothly, and decisively, even down to the choice of editors for this volume. Marie Cervantes-Waldmann performed minor miracles extracting manuscripts gently but persistently from the authors and in turning the typescripts into a book. The other staff members of Dahlem Konferenzen were unfailingly helpful even under trying circumstances. They will be well rememberedbyall who were fortunate enough to be asked to Berlin for the first week in September, 1980. Mineral Deposits and the Evolution of the Biosphere, eds. H. D. Holland and M. Schidlowski, pp. 5-30. Dahlem Konferenzen, 1982. Berl in, Heidelberg, New York: Springer-Verlag. Microbial Processes in the Sulfur Cycle Through Time H. G. TrUper Institut f. Microbiologie, Rheinische Friedrich-Wilhelms-Universitat, 5300 Bonn 1, F. R. Germany Abstract. Two microbial processes are involved in the sulfur cycle of the earth's biosphere: anoxic dissimilatory sulfur oxidation by phototrophic bacteria and dissimilatory sulfate reduction by sulfate-reducing bacteria. In the presence of oxygen at chemoclines and redoxclines dissimilatory sulfur oxidation by chemolithotrophic bacteria (Thiobacillus, Beg- giatoa, and others) occurs. In addition, dissimilatory sulfur reducing bacteria participate in the sulfur cycle.

During the last decade it has become clear that bacteria-plant interactions play an important role in agricultural science. In particular, symbiotic nitro gen fixation, plant tumorigenesis, and plant pathogenic bacteria have been extenSively investigated. Therefore, several of my colleagues suggested the importance of organizing a specialized symposium on the "Molecular genetics of the bacteria-plant interaction." This symposium was held in Germany, at the University of Bielefeld, in the autumn of 1982. The International Program Advisory Board, together with the National Organizing Committee, initially decided to concentrate on the following three topics: 1. Rhizobium-plant interaction 2. Agrobacterium-plant interaction 3. Plant pathogenic bacteria In retrospect, these topics proved to be most popular: Nearly all important groups working in this field contributed to the Bielefeld Symposium. The papers presented are now published as the Proceedings. It will be obvious that this book represents the most comprehensive collection of papers describing the molecular genetics of the bacteria-plant interaction. Scientists, as well as students, can use this book to learn about the basic principles and the current ideas that have recently been developed in this growing research area. The Symposium was financed by the Bundesministerium ftir Forschung und Technologie (Federal Ministry of Science and Technology). I express on behalf of the Organizing committee its sincere appreciation to this sponsor, without whom the Symposium would not have been possible. In addition, the help of several industrial companies is acknowledged."

Compared with forces occurring in soil mechanics problems in civil engineering, the forces that are applied to soil in farming operations generally have a short duration, less than a few seconds, a small loaded area, no more than a few square decimeters, and small intensities, 10 bar being a high value. On the other hand, soil properties vary widely between those of a weak mud and a stone-like dry soil. Tillage and related applications of force to soil are practiced worldwide in farming. Tillage operations are performed on one hectare of land for every three human beings. This means that for the food production for each individual daily, something like one cubic meter of soil is stirred, or about 20 times his body weight. Theoretical knowledge of this most common human activity, which largely determines the surface shape of the fertile part of the earth, is still very limited. In this book the authors have tried to give an outline of the present state of the art. One of the starting points was a course in soil dynamics taught by the authors at the Agricultural University at Wageningen, The Netherlands. We hope to reach interested readers who have no more theoretical knowledge than high school level, as well as readers who want to go beyond the level of a third year university student. For the chapter on wheels and tires we received substantial support from F. G. J. Tijink of the Tillage Laboratory at Wageningen.

Ivermectin and abamectin, members of the avermectin family of compounds, were introduced to the market in the 1980's as a veterinary antiparasitic drug and agricultural pesticide, respectively. Their acceptance and commercial success have been remarkable; both are highly effective and in worldwide use. The efficacy of ivermectin in river blindness has expanded the interest in its use in human medicine. In response to the intense scientific and industrial interest in ivermectin and abamectin and the likelihood that they will be forerunners of an expanding family of drugs, this comprehensive monograph satisfies the need for a review and synthesis of current knowledge about the use of these substances in crop protection as well as in cattle, sheep, swine, horses, dogs, cats, birds, fish, reptiles, and in man. This overview presents chemical, biochemical, and microbiological data, as well as pharmacological, safety, and environmental aspects and covers practical use of the compounds as antiparasitic and pesticide agents, as well as the available safety data that have emerged from the clinical experience with human applications.

Geoffrey R. Dolby, PhD One of the principal characteristics of a scientific theory is that it be falsifiable. It must contain predictions about the real world which can be put to experimental test. Another very important characteristic of a good theory is that it should take full cognisance of the literature of the discipline in which it is embedded, and that it should be able to explain, at least as well as its competitors, those experimental results which workers in the discipline accept without dispute. Readers of John Parks' book will be left in no doubt that his theory of the feed ing and growth of animals meets both of the above criteria. The author's knowl edge of the literature of animal science and the seriousness of his attempt to incor porate the results of much previous work into the framework of the present theory result in a rich and imaginative integration of diverse material concerned with the growth and feeding of animals through time, a theory which is made more precise through the judicious use of mathematics. The presentation is such that the key concepts are introduced gradually and readers not accustomed to a mathematical treatment will find that they can appreciate the ideas without undue trauma. The key concepts are clearly illustrated by means of a generous set of figures. The crux of the theory comprises three differential Eqs. (7. 1-7."

The development of a crop, and therefore its health, is always the result of interplay between biological and environmental factors, as influenced by human agency. In other words, crop health is a highly complex affair. This book is concerned with only one group of agents affecting crop health, the pathogens, and not with animal pests or direct effects of physiological or weather factors. Even within this one group, however, the interaction of causal agents with environmental and biotic factors is highly complex. No less complex is the effect of cultural practices on the crop and its health. There is probably no major practice that does not affect diverse facets of crop growth, which in turn affects crop/pathogen relationships. Thus tillage se quentially affects depth and rate of root development, hence nutrient uptake, hence general plant size and habit as well as crop climate and crop susceptibility. Irri gation affects all these parameters, and facilitates crop growth under diverse macro climatic conditions, with all the ensuing implications for disease development. In this book an attempt is made to superimpose one set of complexities, the cul tural practices, on another such set, crop health. This may seem overambitious, not to say foolhardy, unless we remember that it has been done by farmers, consciously or unconsciously, ever since the beginnings of agriculture. We are here chiefly try ing to rationalize traditional practices, review modern research on the development of further practices, and assess the place of the latter in integrated disease control."

This thorough study is an assessment of the risks involved with the deliberate release of microorganisms modified by means of genetic engineering. Major emphasis is on European cooperative research projects such as the ones on Rhizobium and Baculovirus. Further contributions cover aspects of soil microbiology, genetic transformation in soil, molecular and plasmid genetics, horizontal spread of plasmids, as well as administrative, regulative and legal aspects in relation to possible releases.

Global attention in scientific, industrial, and governmental commUnItIes to traces of toxic chemicals in foodstuffs and in both abiotic and biotic environ ments has justified the present triumvirate of specialized publications in this field: comprehensive reviews, rapidly published progress reports, and archival documentations. These three publications are integrated and scheduled to pro vide in international communication the coherency essential for nonduplicative and current progress in a field as dynamic and complex as environmental con tamination and toxicology. Until now there has been no journal or other publica tion series reserved exclusively for the diversified literature on "toxic" chemicals in our foods, our feeds, our geographical surroundings, our domestic animals, our wildlife, and ourselves. Around the world immense efforts and many talents have been mobilized to technical and other evaluations of natures, locales, magnitudes, fates, and toxicology of the persisting residues of these chemicals loosed upon the world. Among the sequelae of this broad new emphasis has been an inescapable need for an articulated set of authoritative publications where one could expect to find the latest important world literature produced by this emerging area of science together with documentation of pertinent ancil lary legislation."

Lord Rutherford has said that all science is either physics or stamp collecting. On that basis the study of forest biomass must be classified with stamp collecting and other such pleasurable pursuits. Japanese scientists have led the world, not only in collecting basic data, but in their attempts to systematise our knowledge of forest biomass. They have studied factors affecting dry matter production of forest trees in an attempt to approach underlying phYf'ical principles. This edition of Professor Satoo's book has been made possible the help of Dr John F. Hosner and the Virginia Poly technical Institute and State University who invited Dr Satoo to Blacksburg for three months in 1973 at about the time when he was in the final stages of preparing the Japanese version. Since then the explosion of world literature on forest biomass has continued to be fired by increasing shortages of timber supplies in many parts of the world as well as by a need to explore renewable sources of energy. In revising the original text I have attempted to maintain the input of Japanese work - much of which is not widely available outside Japan - and to update both the basic information and, where necessary, the conclusions to keep them in tune with current thinking. Those familiar with the Japanese original will find Chapter 3 largely rewritten on the basis of new work - much of which was initiated while Dr Satoo was in Blacksburg.

Biotechnological methods are opening new ways in plant breeding. They allow novel strategies for improving crop productivity and quality, especially in the agrofood sector. The molecular mechanisms underlying these biotechnological approaches are presented here. Topics included are: pollen development, pollen tube growth, macrosporogenesis and fertilization and the effects of pesticides on sexual plant reproduction.
Fertilization in higher plants is a complex process consisting of two events, the fusion of the egg with one sperm cell resulting in the diploid zygote, and the fusion of embryosac nuclei with another sperm cell, leading to a triploid endosperm. This "double fertilization" is preceded by the pollination process and a long lasting interaction between the dipoid pistil and the haploid pollen tube (progamic phase). Fertilization of flowering plants results in the formation of seeds and fruits, our basic food supply.

Until relatively recently the valuable tropical montane cloud forests (hereaf ter usually referred to as TMCFs) of the world had scarcely come under the assaults experienced by the downslope montane and lowland forests. TMCFs are not hospitable environments for human occupation, and their remoteness (except in places near Andean high mountain settlements and in the Ethiopian Highlands) and difficult terrain have given them de facto protection. The ad jacent upper montane rain forests have indeed been under assault for timber, fuelwood, and for conversion to grazing and agriculture for many decades, even centuries in the Andes, but true cloud forest has only come under ex ploitation as these lower elevational resources have disappeared. They have also been "nibbled" at from above where there have been alpine grasslands under grazing pressure. Increasingly now, however, these cloud forest eco systems are being fragmented, reduced, and disturbed at an alarming rate. It is now becoming recognized that steps must be taken rapidly to increase our understanding of TMCF and to achieve their conservation, because: their water-capture function is extremely important to society; * their species endemism is high; they serve as refugia for endangered species being marginalized in these environments by increasingly transformed lower elevation ecosystems; they are relatively little studied; yet, their value to science is extremely high; they have low resilience to disturbance; vii viii Preface and many other reasons, which will be discussed subsequently in this publi cation.

This volume comprises the lectures of the speakers at the NATO Advanced Research Workshop held at the Congress Centre The Flevohof at Biddinghuizen, The Netherlands, May 11-16, 1986. The purpose of the workshop was to bring together experts in symbiosis, plant pathology and plant molecular biology in order to discuss recent progress in the field of microbe -plant re cognition at the molecular level, to promote integration of various disciplines, and to define recommendations for future research and applications. Plants have developed a variety of sophisticated defence mechanisms to cope with an environment in which many different microbes live. Most microbes which colonize plant tissues are harmless. Some microbes have developed ways to attack plants successfully, resulting in enormous losses of crop yields. Other microbes have reached an agreement with the host plant which is beneficial for both: these microbes live in symbiosis with the plant and provide their host plant for example with substantial amounts of atmospheric nitrogen. Chemical protection of crops is a necessity in modern crop management but this treatment has some negative effects as well. Therefore scientists are looking for alternative, biological, ways to control crop pests. Against this background specialists from eleven countries discussed the results of their most recent work on the molecular background of microbe -plant interactions. It appeared that, in order to capitalize the recent rapid progress made in the mole cular genetical studies on Rhizobium-legume and pathogen-host plant interactions, a multidisciplinary approach is required."