Forests comprise the greatest storage of carbon on land, provide fuel for millions, are the habitat for most terrestrial biodiversity, and are critical to the economies of many countries. Yet changes in the extent and dynamics of forests are inherently difficult to detect and quantify. Remote sensing technologies may facilitate the measurement of some key forest properties which, when combined with other information contained in various computer models, may allow for the quantification of critical forest functions. This book explores how remote sensing and computer modeling can be combined to estimate changes in the carbon storage, or productivity, of forests - from the level of the leaf to the level of the globe. Land managers, researchers, policy makers and students will all find stimulating discussions among an international set of experts at the cutting edge of the interface between science, technology and management.

There are clearly many directions in which the further development of the GUS gene fusion system can progress. Some of these have been outlined above, but others can be imagined. There are no reasons to limit our conceptions of the use of GUS gene fusions to analysis and manipulation of single genes. We can envision numerous marked genes - perhaps with several new fusion systems - giving valuable information about gene interaction, or population structure. The study of plan- pathogen and plant symbiont interactions can progress rapidly with simple quantitative markers for genes and individuals. We can imagine ways of using gene fusions to report on crop physiology or other complex phenotypes, thereby enhancing the accuracy and speed of screening. Introduction of the biosynthetic pathway for glucuronide detoxification by expressing genes for the UDP-glucuronyl transferases in plants may result in novel mechanisms for plants to deal with xenobiotics such as insecticides or herbicides. Synthesis of substrates, which until now has been performed chemicall- resulting in expensive compounds - can be done biosynthetically. This should make the system not only the most powerful gene fusion system for agriculture, but also the most accessible.

R. F. HUTTL AND W. SCHAAF Brandenburg Technical University Cottbus, Chair of Soil Protection and Recultivation, P.O. Box 10 13 44, 03013 Cottbus, Germany The health status of forest trees and stands is determined by numerous site factors such as chemical, physical, and biological soil factors, water supply, climate, weather conditions, management history as well as atmospheric deposition impacts. In this context, the nutrient supply is an important evaluation parameter. Forest trees well supplied with nutrients are more resistant to stresses that affect the forest ecosystem than other trees. This is true for both biotic and abiotic influences. Therefore the investigation of the so-called 'new type forest damage' was aimed at the exact determination of the health status of damaged trees. When considering the complete forest ecosystem, health (=vitality) means the sustainable ability to withstand negative environmental influences and still remain stable and productive. From this viewpoint, an optimal nutritional status is a prerequisite for an optimal health status. The term 'new type forest damage' comprises a number of damage symptoms which have been observed in various tree species on very different sites since the mid-1970s, particularly in Europe and North America. However, they occurred much more intensively in the 1980s. Generally, this forest damage was thought to be related to negative impacts of air pollutants.

Root hairs are tip-growing cells that originate from epidennal cells called trichoblasts. Their role may be simply thought of as extending the surface area of the root to facilitate absorption of nutrients and water. However, as you will see in this book, the root hair is far more than that. To an increasingly larger number of plant biologists, the root hair is a model cell. It grows in much the same way as a pollen tube, by sending vast numbers of vesicles containing cell wall precursors to a rounded apical dome, the tip. Once the trichoblast becomes committed to root hair fonnation, it no longer divides. The root hair cell has a migrating nucleus and a complex cytoskeleton. It has a varied cell wall. It is easy to observe through differential interference contrast microscopy because there are no other cells around it to disturb the image. Cytoplasmic streaming is exceptionally clear, and amyloplasts and even mitochondria and endoplasmic reticulum can be seen without reporter labelling in some species. Root hair mutants are easy to distinguish and catalogue. Plant honnones are involved in their growth and development. It is thus an almost ideal plant cell for experimental manipulation and observation. The root hair is also involved in interactions with soil microbes, as you will learn from later chapters of the book.

It has been known for a long time that the majority of plant viruses contain RNA and in the past decade and a half it has been realized that many have genomes consisting of three molecules of single-stranded RNA with positive polarity. Among these are viruses belonging to four groups recognized by the International Committee for Virus Taxonomy: the Bromovirus and Cucumovirus groups whose genomes are encapsi dated in small icosahedral particles or the Ilarvirus and alfalfa mosaic virus groups with spheroidal or bacilliform particles. In addition to their tripartite genomes, these viruses share a number of other properties and it has been proposed that they should perhaps be grouped in a single virus family for which the name Tricornaviridae has been suggested, the tri indicating the tripartite nature of the genome, the co emphasizing the cooperation of the three genome parts required to initiate infection, and the rna indicating that the genome is composed of RNA. Viruses of this "family" are less uniform in their biological proper ties. A number of them are widespread, causing very destructive plant diseases. Viruses such as those of cucumber mosaic and alfalfa mosaic have very extensive host ranges and are responsible for serious crop losses in many parts of the world. Others such as prunus necrotic ringspot or prune dwarf viruses are more restricted in their host ranges but never theless infect important perennial hosts such as stone fruits and reduce productivity considerably."

This volume presents the papers given at the meeting "Estuarine Management and Quality Assessment" held at Trinity College, Dublin in September 1983. The meeting was organised by the Environmental Sci ences Unit, TCD and the Estuarine and Brackish-Water Sciences Associ ation and was attended by delegates from the United Kingdom, Ireland, France, Holland and Portugal. The theme for the meeting was deliberately chosen in an attempt to bring together the various disciplines and interests in the field of estuarine quality, and the extent to which this objective was met may be judged from the diversity of the contributions. The meeting was arranged under three sub-headings which could be roughly summar ised thu- a) Modelling - as representative of the engineering hydrodynamicist approach. b) Impact - as representative of the biologist-type approach. c) Management - attempting to reconcile the different approaches to, and demands on, the estuary. In fact, since most contributions overlapped into the other two categories, the order in this volume has been changed somewhat from the meeting, and we feel that this book may be fairly presented as one unit. Contributions for which it was not possible to give full transcripts have been included, for completeness, as abstracts. In each session, an invited speaker summarised the state of the art, and the other speakers followed up by describing some new approach to or refinement of the problem."

The role of arthropods in forest ecosystems is poorly understood. Yet such knowledge may be critical in order to explain fully the fundamental forces that shape the structure and regulate the functioning of such ecosys tems. There are numerous hypotheses about the roles of various arthropods, but few, if any, of these hypotheses have been rigorously tested. Some, however, have been repeated so often and so widely that they are now accept ed by many as unequivocal fact. Nothing could be further from the truth. Forest arthropods which derive most of their sustenance from plants are usually specially adapted for feeding in one of three subsystems-the above-ground plant system, the soil-litter system, or the aquatic stream system. Plant-feeding arthropods in the soil-litter and stream systems are primarily saprophous although many consume significant amounts of microorganisms. Research on the role of arthropods in each of these three subsystems has historically been provincial. Until very recently there has been little effort to collate, assimilate, and syn thesize the plethora of findings in even one of these systems-rnuch less all three. This Symposium (at the 15th International Congress of Entomology, Washington, D.C. August 19-27, 1976) was organized for the specific pur pose of promoting scientific synthesis. It fulfills one of the first requirements in such endeavors; namely, the juxtapositioning of current knowledge and hypotheses so that similarities can be perceived, insights can be de rived, and more elaborate conceptual constructs can be built."

One of the most fundamental aspects of the auditory system is its frequency selectivity - the ability to resolve a complex sound into frequency compOhents. This ability plays a role in many aspects of auditory perception, including: the masking of one sound by another; the perception of pitch for pure tones and complex tones; the perception of timbre; the perception of the relative phase of components in complex sounds; and the perception of loudness. Over the last decade, there have been considerable advances in our understanding of frequency selectivity, both at the physiological and psychophysical level, and rapid progress continues to be made. This book summarizes the proceedings of a NATO Advanced Research Workshop on Auditory Frequency Selectivity which was held in Wolfson College, Cambridge from June 23rd to 27th, 1986. The Workshop brought together leading researchers from all disciplines relevant to the topic, with the aim of reviewing and consolidating the latest research findings, and identifying areas of uncertainty or controversy where further research is needed. The book is aimed primarily at research scientists and research students in the fields of psychology, audiology, auditory physiology, biophysics, medicine, acoustical engineering, noise control, communication and speech science. It should also be useful for advanced undergraduates in these disciplines. A feature of the book is that it includes summaries of the discussions which followed the presentation of each paper at the Workshop.

Pork continues to occupy an important position as a food source in affluent societies as well as in developing countries with slower economic growth. The growth of the world swine population continues at a faster rate than that of the human population, a reflection of the sustained demand for pork in all parts of the world. The technical basis for commercial production of swine was presented in our two earlier textbooks-Swine Production in Temperate and Tropical Environ ments, by Pond and Maner, 1974, and Swine Production and Nutrition, by Pond and Maner, 1984. In view of rapidly advancing technology and an appreciation for the systems approach in industry and agriculture, this third book has been restructured to provide the student and practitioner with an integrated concept of pork production. We have attempted to blend the fundamental principles from genetics, physiology, nutrition, and biotechnology into the modern concepts of systems analysis and simulation modeling. The objective is to create a teaching approach which empha sizes the integrated synthesis of biological with physical and environmental sci ences and economics. This approach is expected to provide an overall pork pro duction systems view that individual producers can adapt to their specific resources, needs, and goals. Our new co-author, Dr. Dewey Harris, has used his expertise and perspective on interacting systems to change the complexion of the book to fulfill this objective. In addition, Dr."

William C. Taylor Department of Genetics University of California Berkeley, California 94720 It is evident by now that there is a great deal of interest in exploiting the new technologies to genetically engineer new forms of plants. A purpose of this meeting is to assess the possibilities. The papers that follow are concerned with the analysis of single genes or small gene families. We will read about genes found within the nucleus, plastids, and bacteria which are responsible for agri culturally important traits. Given that these genes can be isolated by recombinant DNA techniques, there are two possible strategies for plant engineering. One involves isolating a gene from a cultivated plant, changing it in a specific way and then inserting it back into the same plant where it produces an altered gene product. An example might be changing the amino acid composition of a seed pro tein so as to make the seed a more efficient food source. A second strategy is to isolate a gene from one species and transfer it to another species where it produces a desirable feature. An example might be the transfer of a gene which encodes a more efficient pho tosynthetic enzyme from a wild relative into a cultivated species. There are three technical hurdles which must be overcome for either strategy to work. The gene of interest must be physically isolated.

It is appropriate at this time to reflect on two decades of research in biological control of weeds with fungal plant pathogens. Some remarkable events have occurred in the last 20 years that represent a flurry of activity far beyond what could reasonably have been predicted. In 1969 a special topics review article by C. L. Wilson was published in Annual Reviews of Phytopathology that examined the literature and the potential for biological control of weeds with plant pathogens. In that same year, experiments were conducted in Arkansas that determined whether a fungal plant pathogen could reduce the infestation of a single weed species in rice fields. In Florida a project was under way to determine the potential use of a soil-borne plant pathogen as a means for controlling a single weed species in citrus groves. Work in Australia was published that described experiments that sought to determine whether a pathogen could safely and deliberately be imported and released into a country to control a weed of agricultural importance. All three projects were successful in the sense that Puccinia chondrillina was released into Australia to control rush skeleton weed and was released later into the United States as well, and that Colletotrichum gloeosporioides f.sp. aeschynomene and Phytophthora palmivora were later both marketed for the specific purpose of controlling specific weed species.

This volume is the last contribution of a series of With the present book, a further gap concern studies concerned with the plant material of one ing leaf morphology and leaf venation, as well and the same area of Venezuelan Guiana. The as some structural peculiarities of physiological importance, is closed so that an exhaustive survey studies originated through a collaboration with the forest engineer Dr. B. Rollet, the FAO expert in of bark and leaf morphology and anatomy as well forest inventory who collected the material of tree as of fruit and seed structure of the plants of a barks, leaves, fruits and seeds in Venezuelan certain well-known area is herewith given. Not Guiana around the "Rio Grande," "EI Paraiso," only were hundreds of species studied, but and "EI Dorado" camps. In the first place, tree structural characteristics were related to "forest barks of about 280 species of dicotyledons stratification," i. e. to the different micro climatic belonging to 48 families were studied (family by conditions in the forest, as the height of the trees family) by Roth in separate publications which and shrubs studied was known. It is of common mainly appeared in Acta Botanica Venezuelica knowledge that in the lower forest layers, light is a and in Acta Biol6gica Venezuelica (see the bibli limiting factor, while humidity is sufficiently avail ography in Roth 1981)."

This book provides a comprehensive, global synthesis of current knowledge on the potential and challenges associated with the multiple roles, use, management and marketing of non-timber forest products (NTFPs). There has been considerable research and policy effort surrounding NTFPs over the last two and half decades. The book explores the evolution of sentiments regarding the potential of NTFPs in promoting options for sustainable multi-purpose forest management, income generation and poverty alleviation. Based on a critical analysis of the debates and discourses it employs a systematic approach to present a balanced and realistic perspective on the benefits and challenges associated with NTFP use and management within local livelihoods and landscapes, supported with case examples from both the southern and northern hemispheres. This book covers the social, economic and ecological dimensions of NTFPs and closes with an examination of future prospects and research directions.

Thrips (fhysanoptera) are very small insects, widespread throughout the world with a preponderance of tropical species, many temperate ones, and even a few living in arctic regions. Of the approximately 5,000 species so far identified, only a few hundred are crop pests, causing serious damage or transmitting diseases to growing crops and harvestable produce in most countries. Their fringed wings confer a natural ability to disperse widely, blown by the wind. Their minute size and cryptic behavior make them difficult to detect either in the field or in fresh vegetation transported during international trade of vegetables, fruit and ornamental flowers. Many species have now spread from their original natural habitats and hosts to favorable new environments where they often reproduce rapidly to develop intense damaging infestations that are costly to control. Over the past decade there have been several spectacular examples of this. The western flower thrips has expanded its range from the North American continent to Europe, Australia and South Africa. Thrips palmi has spread from its presumed origin, the island of Sumatra, to the coast of Florida, and threatens to extend its distribution throughout North and South America. Pear thrips, a known orchard pest of Europe and the western United States and Canada has recently become a major defoliator of hardwood trees in Vermont and the neighboring states. Local outbreaks of other species are also becoming problems in field and glasshouse crops as the effectiveness of insecticides against them decline.

The XXX Congress of the International Union of Physiological Sciences took place in Vancouver, Canada, in July 1986; and this Volume contains a selection of the Review Lectures which formed part of the Congress programme. They cover most of the areas of contemporary physiology and were presented by distinguished scientists from many parts of the world. An innovation at this Congress was the inclusion in the programme of a number of lectures devoted to historical subjects. These lectures attracted large audiences at the meetings, and three of them also appear in this book. Finally, the Plenary Lectures which formed part of the opening and closing ceremonies and which deal with some aspects of Canadian physiological history, find a place here as well. The Editors are grateful to all of the authors who provided the manuscripts which go to make up this book, and to John Donald for his invaluable assistance in the preparation of the final text; as well of course to all of the contributors whose participation made the Congress the success which it was. It is hoped that this Volume will provide a useful memento of the event.

Temperate forests cover large areas of Europe and perform a number of important functions such as the regulation of energy and matter, production of wood and other resources, and conservation of biodiversity and habitats; they also have special signi?cance in social and cultural contexts. Initiated in 1960s, the ?rst International Biological Program (IBP) focused on ''the biological basis of productivity and human welfare. '' As the German contribution to the IBP, ecosystem research has been carried out since 1966 in the Solling area (Ellenberg H., Ecological Studies 2, 1971), an upland region in Northwest Germany. This study provided clear evidence that the stability of forest ecosystems was threatened by the high inputs of at- spheric pollutants. This promoted many interdisciplinary research programs which were coordinated by Prof. Dr. Bernhard Ulrich and the Forest Ecosystems Research Center of the University of Go]ttingen. This involved, in addition to the Solling site, the establishment of two other sites for long-term monitoring of ecosystem pro- ] cesses. The two contrasting sites were established in 1980 at Gottinger Wald on base-rich calcareous soil and in 1989 at Zierenberg on volcanic soil. These projects were funded initially by the Federal Ministry of Research and Technology (BMBF) as interdisciplinary projects under the titles: ''Conditions of Stability of Forest Ecosystems'' (1989-1993), and ''Dynamics of Forest Ecos- tems'' (1993-1998). The primary goal of these studies was to quantify the ecolo- cal condition of forests in a changing environment and element ?uxes."

The oil crisis during the 1970s turned interest towards the utilization of renewable resources and towards lignocellulosics in particular. The 1970s were also the cradle period of biotechnology, and the years when biotechnical utilization of lignocellulosic waste from agriculture and forestry gained priori ty. This was a logical conclusion since one of nature's most important biologi cal reactions is the conversion of wood and other lignocellulosic materials to carbon dioxide, water and humic substances. However, while biotechnology in other areas like medicine and pharmacology concerned production of expen sive products on a small scale, biotechnical utilization and conversion of ligno cellulosics meant production of inexpensive products on a large scale. Biotechnical utilization of lignocellulosic materials is therefore a very difficult task, and the commercial utilization of this technology has not progressed as rapidly as one would have desired. One reason for this was the lack of basic knowledge of enzyme mechanisms involved in the degradation and conversion of wood, other lignocellulosics and their individual components. There are also risks associated with initiating a technical development before a stable platform of knowledge is available. Several of the projects started with en thusiasm have therefore suffered some loss of interest. Also contributing to this failing interest is the fact that the oil crisis at the time was not a real one. At present, nobody predicts a rapid exhaustion of the oil resources and fuel production from lignocellulosics is no longer a high priority."

As forests decline in temperate and tropical climates, highly-developed countries and those striving for greater economic and social benefits are beginning to utilize marginal forests of high-latitude and mountainous regions for resources to satisfy human needs. The benefits of marginal forests range from purely aesthetic to providing resources for producing many goods and services demanded by a growing world population. Increased demands for forest resources and amenities and recent warming of high latitude climates have generated interest in reforestation and afforestation of marginal habitats in cold regions. Afforestation of treeless landscapes improves the environment for human habitation and provides for land use and economic prosperity. Trees are frequently planted in cold climates to rehabilitate denuded sites, for the amenity of homes and villages, and for wind shelter, recreation, agroforestry, and industrial uses. In addition, forests in cold climates reduce the albedo of the earth's surface in winter, and in summer they are small but significant long-lived sinks for atmospheric carbon dioxide. Finally, growth and reproductive success of forests at their geographic limits are sensitive indices of climatic change. As efforts to adapt forests to cold climates increase, however, new afforestation problems arise and old ones intensify. Austral, northern, and altitudinal tree limits are determined by many different factors. Current hypotheses for high-latitude tree limits are based on low growing-season temperatures that inhibit plant development and reproduction.

Air pollutants provide environmental conditions that drastically differ in many respects from those to which forest trees are naturally adapted. Leading experts in the field here consider these questions of immediate relevance arising from the changing environment: (1) Do air pollutants introduce effects of selection that differ from those known for populations that are not subject to such stress conditions? (2) If air pollutants introduce quantitatively or even qualitatively novel selective effects, which consequences might arise from the adaptation of forest tree populations to the present conditions as well as for the preservation of adaptability to future conditions? In addition to these questions, concepts for preservation of genetic resources are discussed.

Interdependence between species is a law of nature. The degree of this interdependence is vividly evident in the plant-microbial world. Indeed, there is no axenic plant in nature and one finds various forms of interac tions between these two kingdoms ranging from completely innocuous to obligate parasitic. Most of these interactions are poorly understood at the molecular and physiological levels. Only those few cases for which a molecular picture is emerging are discussed in this volume. With the advent of recombinant DNA technology and the realization that some of these interactions are very beneficial to the host plant, a spate of activity to understand and manipulate these processes is occurring. Microbes interact with plants for nutrition. In spite of the large number of plant-microbe interactions, those microbes that cause harm to the plants (i. e., cause disease) are very few. It is thus obvious that plants have evolved various defense mechanisms to deal with the microbial world. The mecha nisms for protection are highly diverse and poorly understood. Some pathogens have developed very sophisticated mechanisms to parasitize plants, an excellent example for this being crown gall caused by a soil bac terium, Agrobacterium tumefaciens. A remarkable ingenuity is exhibited by this bacterium to manipulate its host to provide nitrogenous compounds which only this bacterium can catabolize. This is carried out by a direct gene transfer mechanism from bacteria to plants."

This book is the first comprehensive description of development of the Acipenserid fish published in the English language. It con tains the results of more than 40 years of studies by the authors and their colleagues. My own life in science has been intimately related both with the authors and the fish, which are the subject of this book. Therefore, it gives me a great pleasure to present to the English reader an expanded version of the book. Those interested in the history of biology must be well aware of the fact that genetics in the USSR was practically demolished by Lysenko at the session of the Lenin All-Union Academy of Agricultural Sciences in 1948. However, it is much less well known that other fundamental branches of biology were also persecuted at that time, experimental embryology (developmental mechanics) among them. As a result, many embryologists, in cluding the authors of this book, were forced to turn to more ap plied problems, this being the only way to continue research. They had to abandon amphibians and concentrate their efforts on sturgeon."

Rice is the most important cereal crop which feeds more than half the population of the world. It is being grown in more than 144. 641 million ha with a production of over 468. 275 million tons (in 1988). Rice is attacked by a large number of pests and diseases which cause an enormous loss in its yield. Therefore, the major objectives in rice breeding are the development of disease resistance, tolerance to insects, adverse soil water, and drought; and improvement of quality including increased protein content. Tremendous efforts being made at the International Rice Research Institute have resulted in the release of improved varieties. It is estimated that the world's annual rice production must increase from 460 million tons (in 1987) to 560 million tons by the year 2000, and to 760 million tons by 2020 (a 65% increase) in order to keep up with the population growth (IRRI Rice Facts 1988). To achieve this gigantic goal, new strategies have to be evolved. Since the success of any crop improvement program de pends on the extent of genetic variability in the base population, new techniques need to be developed not only to generate the much needed variability but also for its conservation. In this regard the progress made in the biotechnology of rice during the last 5 years has amply demonstrated the immense value of innovative approaches for further improvement of this crop.

Charles E. Hess Department of Environmental Horticulture University of California Davis, CA 95616 Research in the biology of adventitious root formation has a special place in science. It provides an excellent forum in which to pursue fundamental research on the regulation of plant growth and development. At the same time the results of the research have been quickly applied by commercial plant propagators, agronomists, foresters and horticulturists (see the chapter by Kovar and Kuchenbuch, by Ritchie, and by Davies and coworkers in this volume). In an era when there is great interest in speeding technology transfer, the experiences gained in research in adventitious root formation may provide useful examples for other areas of science. Interaction between the fundamental and the applied have been and continue to be facilitated by the establishment, in 1951, of the Plant Propagators' Society, which has evolved into the International Plant Propagators' Society, with active programs in six regions around the world. It is a unique organization which brings together researchers in universities, botanical gardens and arboreta, and commercial plant propagators. In this synergistic environment new knowledge is rapidly transferred and new ideas for fundamental research evolve from the presentations and discussions by experienced plant propagators. In the past 50 years, based on research related to the biology of adventitious root formation, advances in plant propagation have been made on two major fronts.

Somatic hybrids through the fusion of plant protoplasts have widened the genetic variability of cultivated plants. As "Somatic Hybridization in Crop Improvement I," published in 1994, this volume describes how this discipline can contribute to the improvement of crops. It comprises 24 chapters dealing with interspecific and intergeneric somatic hybridization and cybridization. It is divided into four sections:
I. Cereals: Barley, rice, and wheat.
II. Vegetables and Fruits: "Arabidopsis," "Asparagus," "Brassica," chicory, "Citrus," "Cucumis," "Diospyros," "Ipomoea," and various Solanaceous species, e.g., tomato, potato, and eggplant.
III. Medicinal and Aromatic Plants: "Atropa," "Dianthus," "Nicotiana," and "Senecio."
IV. Legumes/Pasture Crops: Alfalfa.
This book is tailored to the needs of advanced students, teachers and researchers in the fields of plant breeding, genetic engineering, and plant tissue culture.