With improved microscope and preparation techniques, studies of histo logical structures of plant organisms experienced a revival of interest at the end of the 19th century. From that time, histological data have sub stantially studies of the pioneers in botanical science. From the beginning of the 20th century, the microscope allowed research in cell structure, the general functional unit of living beings. Advances in cytology gradually influenced histology, at first, however, rather timidly. Only the new and spectacular progress in ultrastructural cytology and cytochemistry led to a great increase in modern work on the structures of vascular plants and the related ontogenical and physiological data, thanks to the use of the electron microscope and the contribution of molecular biology. Not only did new techniques lead to new approaches, but achieve ments in general biology shifted the orientation of research, linking in vestigation to the physiological aspects of cell and tissue differentiation. Among these, the demonstration of the general principles of develop ment, and the characterization of molecules common to plants and animals, which control and govern the main basic functions of cells and tissues, have widened the scope of modern research on plant struc tures. Present trends in biological research show that it is necessary to know the structures thoroughly, from the ultrastructural cytological scale to the scale of tissue and organ arrangement, even for physiological research on either cells, tissues, or whole organs. The study of growth factors, differ entiation, or organogenesis can be mentioned as an example."

Clonal forestry has come of age. Basic techniques in genetics and biotechnology of other organisms are generally applicable to forest trees. However, there are some differences, in particular in the juvenile- and maturation-related regeneration. Examined here are crucial topics of juvenility, maturation and rejuvenation in clonal propagation of trees. In addition, the genetics of clones, population biology of clonal deployment, propagation and field testing of clones, clone identification, clonal physiology, regeneration and variation in plant tissue cultures, the role of somatic embryogenesis in clonal forestry, and recent developments in biotechnology, including the molecular structure of trees and gene transfer are covered in depth.

Over the past years, a great deal has been learned about variation in wood prop erties. Genetic control is a major source of variation in most wood properties. Wood is controlled genetically both directly in the developmental or internal pro cesses of wood formation and indirectly by the control of tree form and growth patterns. Emphasis in this book will be on the internal control of wood production by genetics although there will be two chapters dealing with the indirect genetic control of wood, which was covered in detail in the previous book by Zobel and van Buijtenen (1989). The literature on the genetics of wood is very variable, SO'lle quite superficial, on which little reliance can be placed, and some from well-designed and correctly executed research. When suitable, near the end of each chapter, there will be a summary with the authors' interpretation of the most important information in the chapter. The literature on the genetics of wood can be quite controversial. This is to be expected, since both the environment and its interaction with the genotype of the tree can have a major effect on wood properties, especially when trees of similar genotypes are grown under widely divergent conditions. Adding to the confusion, studies frequently have been designed and analyzed quite differently, resulting in conflicting assessments of results."

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."

Developments in statistics and computing as well as their application to genetic improvement of livestock gained momentum over the last 20 years. This text reviews and consolidates the statistical foundations of animal breeding. This text will prove useful as a reference source to animal breeders, quantitative geneticists and statisticians working in these areas. It will also serve as a text in graduate courses in animal breeding methodology with prerequisite courses in linear models, statistical inference and quantitative genetics.

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.

The trend in forestry is toward shorter rotations and more complete utiliza tion of trees. The reasons are: (1) financial pressures to obtain rapid returns on the forestry investment made possible by an earlier harvest; (2) enforced harvest of young plantations to maintain a continuing supply of cellulose for mills where wood shortages are experienced; (3) thinning young plantations, both because they were planted too densely initially and because thinning is done where long rotation quality trees are the forestry goal; (4) more intensive utilization is being done using tops and small diameter trees; and (5) there is interest in using young (juvenile) wood for special products because of its unique characteristics and the development of new technologies. The largest present-day source of conifer juvenile wood is from thinnings of plantations where millions of hectares of pine were planted too densely. Because of the better growth rate resulting from improved silviculture and good genetic stock, plantations will need to be thinned heavily. As a result of this trend, young wood makes up an increasingly larger proportion of the total conifer wood supply each year. Large amounts of juvenile wood from hard woods are also currently available, especially in the tropics and subtropics, because of the fast growth rate of the species used, which results in shorter rotations and ess ntially all juvenile wood."

The series "Chemistry of Plant Protection" continues the handbook "Chemie der Pflanzenschutz- und Schadlingsbekampfungsmittel", edited by R. Wegler. This volume covers contributions in the fields of pyrethroid residues and immunoassays.

Presented here is an analysis of plant development and plant metabolism using the tools of genetics and molecular biology, such as mutant analysis, mutation tagging, mapping using polymorphic characters and basic molecular biology techniques. Studies with a range of model genetic organisms, most notably maize and "Arabidopsis," are included. The reader gains a comprehensive view of the subject which is more and more of both scientific and industrial interest. The value of basic research in plants is highlighted and examples where basic studies have led to applications in agricultural biotechnology are given.

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."

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.

7. 2 The Pilot Zone of the FerIo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 7. 2. 1 Geographical Zoning and Administrative Setup. . . . . . . . . . . . . 157 7. 2. 2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 7. 2. 3 The Substratum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 7. 2. 4 Surface Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 7. 2. 5 Vegetation and Rangelands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 7. 2. 6 Wildlife. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7. 2. 7 Livestock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7. 2. 8 Evolution of Land Use and History of Development . . . . . . . . 170 7. 3 Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 7. 3. 1 Principles, Problems and Methods . . . . . . . . . . . . . . . . . . . . . . . . 181 7. 3. 2 Evaluation of Green Herbaceous Biomass by Orbital Remote Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 7. 3. 3 Evaluation of Range Production from Ground Sampling . . . . 207 7. 3. 4 Low Altitude Systematic Reconnaissance Flights (SRF) . . . . . . 211 7. 3. 5 Practical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 7. 4 Conclusions on Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 8 General Conclusions: Towards an Ecological Management of the Sahelian Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 of Scientific Names. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 . . . . . . . . . . . . Index Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 VII Abbreviations and Acronyms AVHRR Advanced Very High Resolution Radiometer CILSS Comite Inter-Etats de Lutte contre la Secheresse au Sahel CIPEA Centre International pour l'Elevage en Afrique CNRS Centre National de la Recherche Scientifique CP Crude Protein (N x 6.

Isolated protoplasts are a unique tool for genetic manipulation of plants. Since the discovery of a method for the enzymatic isolation of pro-. toplasts by Professor E. C. Cocking in 1960, tremendous progress has been made in this very fascinating area of research. I have witnessed the struggle in the 1960's and early 1970's, when obtaining a clean prepara tion of protoplasts was considered an achievement. I also shared the pioneering excitement and enthusiasm in this field during the 2nd Inter national Congress of Plant Tissue Culture held at Strasbourg in 1970, where Dr. I. Thkebe of Japan presented his work on the induction of division in tobacco protoplasts. This was followed by my participation in three international conferences devoted to plant protoplasts held in 1972 in Salamanca (Spain) and Versailles (France), and then in 1975 in Nottingham (England). The enthusiasm shown by plant scientists at these meetings was ample proof of the bright future of protoplast technology, and it became evident that protoplasts would playa major role in plant biotechnology, especially in genetic engineering. Since then we have never looked back, and now the methods for isolation, fusion, and culture, as well as regeneration of somatic hybrids, have become routine laboratory procedures for most plant species. Currently the focus is on cereal and tree protoplasts. In order to bring about any genetic manipulation through fusion, in corporation of DNA, and transformation, the regeneration of the entire plant through manipulation of protoplasts is a prerequisite."

While working in the laboratory of Professor Dr. Jacob Reinert at the Freie Universitat Berlin (1974-1976), I had the opportunity to become deeply involved in studying the intricacies of the fascinating phenomenon of somatic embryogenesis in plant cells and protoplasts. In numerous stimu lating discussions with Professor Reinert on this subject, I was fully convinced that somatic embryogenesis would become one of the most important areas of study, not only regarding basic and fundamental aspects, but also for its application in crop improvement. During the last decade, we have witnessed tremendous interest and achievements in the use of somatic embryos for the production of synthetic seeds, for micro prop a gation, genetic transformation, cryopreservation, and conservation of germplasm. The en masse production of somatic embryos in the bioreactors has facilitated some of these studies. Somatic embryos have now been induced in more than 300 plant species belonging to a wide range offamilies. It was therefore felt that a compilation ofliterature/state of the art on this subject was necessary. Thus, two volumes on Somatic Embryo genesis and Synthetic Seed have been compiled, which contain 65 chapters contributed by International experts. Somatic Embryogenesis and Synthetic Seed I comprises 31 chapters, arranged in 3 sections: Section I Commitment of the cell to somatic embryogenesis; early events; anatomy; molecular basis; gene expression; role of polyamines; machine vision analysis of somatic embryos. Section II Applications of somatic embryos; technology of synthetic seed; fluid drilling; micropropagation; genetic transfor mation through somatic embryos; cryopreservation."

Properly treated sewage effluent becomes an alternative source of irrigation water, and at the same time it provides a convenient means of sewage disposal through land treatment to prevent potential health and environmental hazards caused by uncontrolled flow of wastewater. The objective of this volume is to provide the reader with a comprehensive up-to-date overview of the principles and practices of irrigation with treated sewage effluent, including special reference to arid quality of the water (e.g. pathogenic organisms, salt, nutrients). The present volume describes the main components of effluent-soil-plant systems involved in the development of appropriate irrigation-fertilization-cropping management for optimizing crop production. Comprehensive information has been suggested on the following subjects: 1. source, treatment and properties of sewage effluent; 2. main processes of different effluent constituents on soil-plant systems; 3. irrigation-fertilization management; 4. irrigation systems for sewage effluent.

Crassulacean acid metabolism (CAM) represents one of the best-studied metabolic examples of an ecological adaptation to environmental stress. Well over 5 % of all vascular plant species engage in this water-conserving photosynthetic pathway. Intensified research activities over the last 10 years have led to major advances in understanding the biology of CAM plants.
New areas of research reviewed in detail in this book include regulation of gene expression and the molecular basis of CAM, the ecophysiology of CAM plants from tropical environments, the productivity of agronomically important cacti and agaves, the ecophysiology of CAM in submerged aquatic plants, and the taxonomic diversity and evolutionary origins of CAM.

Modem Methods of Plant Analysis When the handbook Modern Methods of Plant Analysis was fIrst introduced in 1954 the considerations were: 1. the dependence of scientifIc progress in biology on the improvement of existing and the introduction of new methods; 2. the difficulty in fInding many new analytical methods in specialized journals which are normally not accessible to experimental plant biologists; 3. the fact that in the methods sections of papers the description of methods is frequently so compact, or even sometimes so incomplete that it is difficult to reproduce experiments. These considerations still stand today. The series was hIghly successful, seven volumes appearing between 1956 and 1964. Since there is still today a demand for the old series, the publisher has decided to resume publication of Modern Methods of Plant Analysis. It is hoped that the New Series will be just as acceptable to those working in plant sciences and related fIelds as the early volumes undoubtedly were. It is difficult to single out the major reasons for success of any publication, but we believe that the methods published in the fIrst series were up-to-date at the time and presented in a way that made description, as applied to plant material, complete in itself with little need to consult other publications. Contributing authors have attempted to follow these guidelines in this New Series of volumes.

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.

An increase in the demand for wood results in improved recovery and less residual biomass in the forests. Paradoxically, interest in forest residue as a renewable source of raw material seems to be in a reverse ratio to its availability in a certain area. Finland and Sweden are probably more dependent on forestry and forest in dustries than any other developed countries in the world. A sufficiency of raw ma terial for integrated forest industries is vital for the national economy of both countries, and a great deal of attention is being paid to the long-term potential of unutilized biomass left behind in logging operations. Furthermore, since these countries possess no reserves of fossil fuels, and since their per-capita consump tion of primary energy is exceptionally high, they also consider unmerchantable forest biomass a realistic source of indigenous energy. A joint Nordic research project on harvesting and utilization of logging residue was carried out in 1969-1976 under the auspices of the Nordic Research Council on Forest Operations. This fruitful cooperation soon gave rise to related national projects in Sweden, Finland, Norway, and Denmark, stimulating further research and producing practical applications. Concurrently, particularly after the worldwide energy crisis in 1973, research on all aspects of utilization of forest bio mass mushroomed in the United States, Canada, and the Soviet Union. An ex plosive increase occurred in both the number and diversity of biomass studies.

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."

The unsaturated zone is the medium through which pollutants move from the soil surface to groundwater. Polluting substances are subjected to complex physical, chemical and biological transformations while moving through the unsaturated zone and their displacement depends on the transport properties of the water-air porous medium system. Pollution caused by human activities, agriculture, and industry, has brought about a growing interest in the role of the unsaturated zone in groundwater pollution. Due to the complexity and the multidisciplinary nature of the subject, it is being investigated by specialists from various scientific disciplines, such as soil physicists, chemists, biologists, and environmental engineers. This state of affairs has motivated the initiative taken by the Water Quality Commissions of IUPAC (the International Union of Pure and Applied Chemistry) and IAHS (the International Association of Hydrological Sciences) to convene an international workshop, which was organized and hosted by the Institute of Soils and Water of the Agricultural Research Organization in Bet Dagan, Israel in March 1983. The lecturers at the workshop were an invited group of specialists who are engaged in studying the many facets of the unsaturated zone, and the present book is a selection of their presentations. Each chapter of the book relates to a different aspect of the unsaturated zone."

The author has drawn together almost all published methods since 1975 on the determination of anions in all types of matrices. He presents the methods in a logical manner so that the reader can quickly gain access to the method and types of instrumentation available.

This is a stimulating tale of the interplay of observation, experimentation, working hypotheses, tentative conclusions, niggling and weightier doubts and great aspirations, on the part of some score of students, on varied ecological and other aspects of the regime and role of fire in relevant biomes and ecosystem- mainly in South Africa - and on other pertinent features of fire ecology. The impressive contents is a tribute to conveners and authors alike. One can expect a profound range and depth ofinvestigation and interpretation, a closeknit fabric of knowledge, delicately interwoven with wisdom, an exposition and quintessence of information. Admipable is the collective vision responsible for selecting appropriate topics: the wide sweeps of the brush picturing the nature of the biomes; ably describing the fire regimes - whether in grassland, savanna, fynbos or forest; skillfully defining the effects of such regimes - according to ecosystem - upon aerial and edaphic factors of the habitat, upon constituent biota, individually, specifically and as a biotic community; elucidating the basic implications in the structure and dynamics of the plant aspect of that community ... and unravelling to some degree the tangled knot of the conservation and dissipation of moisture and nutrients. Moreover, gratitude is owed for efforts exerted to understand the interplay of fire and faunal behaviour and dynamics as well as composition, together with the principle of adaptive responses of organisms of diverse kinds.

Due to the long-term planning horizons and the great variety of natural, economic, and operational hazards affecting forest ecosystems, uncertainty and multiple risk are typical aspects of forest management. Applications of risk analysis are surprisingly rare, in spite of the rich assortment of sophisticated forest planning tools that are available today. The objective of this particular volume within the book series Managing Forest Ecosystems is to present state-of-the-art research results, concepts, and techniques regarding the assessment and evaluation of natural hazards and the analysis of risk and uncertainty relating to forest management. Various aspects of risk analysis are covered, including examples of specific modelling tools. The book is divided into three sections covering ecological perspectives, applications in engineering and planning, and methods applicable to economics and policy.

In terrestrial ecosystems, soil microorganisms and soil animals are essential for litter degradation, soil formation and the availability of nutrients and trace elements. The measurement of biological soil parameters allows a rapid evaluation of the effects of chemical and physical influences due to pollutants or soil management.
This book introduces a number of well proved methods for the analysis of carbon, nitrogen, phosphorus and sulfur cycles. It focuses further on the determination of the number and biomass of microorganisms, algae and animals in the soil. Particular emphasis is placed on the comprehensible and complete description of the experimental procedures.