Within the extreme diversity of aquatic and terrestrial plant genera, each has characteristic cell wall forms. A number of hypotheses have been advanced to explain differences in microfibril arrangements across anyone such wall. Of those, only the 'multinet' theory, which involves the postulation of reorientation of microfibrils caused by cell extension, now has a substantial number of ad herents. However, many scientists are sceptical of its validity; obviously it is incompatible with various observed microfibril arrangements. The tenet of this study is that any such hypothesis can be valid only if it is applicable to all plant forms and wall types. Initially, reanalyses are made of data claimed to confirm justification for multi net postulations. The results show that previous deductions from those data, in support of multinet, are subject to serious challenge. Similarly, a re-examination of the observations, which inspired the multinet theory, shows they have a more logical explanation. Herein, it is concluded that cell wall development involves biophysical factors, which neces sarily prevent multinet's postulated large reorientations of microfibrils, after their formation. Unfortunately the previously most recent published theory, which is based on the absence of reorientation during extension, fails to answer the fundamental question of how alternating orientations between lamellae are controlled, or explain variations in thickness of wall layers. Extensive published data are used to identify forces involved in cell wall development.

Dutch elm disease is a significant problem in forestry and horticulture which has proven remarkably difficult to ameliorate. Since the introduction of the Dutch elm disease pathogen to North America, the disease has devastated the elm population of this continent and has been the subject of intensive research. This book summarizes the range of approaches that have been taken to address the disease, and emphasizes the significant progress over the past decade in applying methods from cell and molecular biology. Dutch Elm Disease: Cellular and Molecular Approaches will be of interest to scientists in plant pathology, horticulture, forestry, biological control, and plant breeding.

This is the third annual compendium of a Technical Session of the Physiology Working Group of the Society of American Foresters held at the National Convention. Specialists in a dedicated area of tree physiology were invited to prepare chapter contributions synthesizing the status of knowledge in their area of expertise. Plant growth regulators (PGRs) was selected as the topic for in-depth examination at the 1986 Technical Session because a knowledge of how these "secondary messengers" regulate tree morphogenesis is vital to applications of biocontrol and biotechnology. Plant growth regulators have been the subject of numerous reviews in recent years. However, few have dealt specifically with woody perennials, and they are generally confined to single processes and/or organs. This volume attempts to provide a more comprehensive treatise of PGRs as they influence various ontogenetic events in forest trees. Reproductive physiology, both sexual and asexual, is emphasized because of its relevance to current efforts directed at increasing efficiency in the breeding and production of genetically improved trees for reforestation. The chapters on vegetative growth will be of interest to silviculturists and urban foresters as they consider cultural treatments in the management of forests and individual trees for specific products and purposes. This book should serve as a valuable text and source of reference for students, researchers and other professionals interested in gaining a better understanding of PGRs. The reader, however, who expects definitive answers to how PGRs function or can be used to control specific processes is likely to be disappointed.

Chemistry of Plant Protection, Volume 7, provides critical review articles on new aspects of herbicide resis- tance, serving the needs of research scientists, pesticide manufacturers, government regulators, agricultural practitioners.

Since the middle of the Sixties, new types of formulation for biologically active com pounds have been developed, which have been introduced into the literature under the term Controlled Release Formulations (CRF). Stimulated by results from former and successful pharmaceutical research, which was engaged in the production of prepa rations with protracted effects (introduction onto the market in the year 1952 of D amphetamine in the form of pellets, coated to varying degrees with fats and waxes) 1), experiments were carried out to transfer the prolongation of effectiveness to pesticidal substances also, by means of a depot formulation. Initial work was concerned with the production of protective coatings for sonar systems in marine ecosystems. By means of antifouling paints or rubber coatings containing tri-n-butyl-tin oxide (TBTO), the growth of marine organisms on sonar domes, buoys and hulls in the water could be effectively prevented 2. 3). Controlled release formUlations of pesticides are defined as depot systems which continuously release their toxic constituents into the environment over a specified period of time (usually months to years) 4). According to this definition, such formu lations can be successfully employed where a chronic exposure to biologically active compounds is required over a longer period. The following hypothetical example is intended to illustrate this 5). In Fig. 1, the duration of activity of a non-persistent pesticide with a loss rate under environmental conditions of t1/2 = 15 days, is graphically illustrated."

This book integrates the latest global developments in forestry science and practice and their relevance for the sustainable management of tropical forests. The influence of social dimensions on the development of silvicultural concepts is another spotlight. Ecology and silvicultural options form all tropical continents, and forest formations from dry to moist forests and from lowland to mountain forests are covered. Review chapters which guide readers through this complex subject integrate numerous illustrative and quantitative case studies by experts from all over the world. On the basis of a cross-sectional evaluation of the case studies presented, the authors put forward possible silvicultural contributions towards sustainability in a changing world. The book is addressed to a broad readership from forestry and environmental disciplines.

After the publication of the Diagnostic Manual for the Identification of Insect Pathogens, the authors received many queries asking why they had not included the larger metazoan parasites as well as the microbial forms. An examination of the literature indicated that pictorial guides to the identification of nematodes and the immature stages of insect parasites were unavailable. Consequently we decided to rewrite the sections cover ing insect pathogens and combine these with new sections on ento mogenous nematodes and the immature stages of insect parasites. The result is the present laboratory guide, which is unique in covering all types of biotic agents which are found inside insects and cause them injury or disease. Included as parasites are insects and nematodes. Among the pathogens included are viruses, rickettsias, bacteria, fungi, and protozoans. Emphasis is placed on identification with an attempt to use the most easily recognizable characters. Use of a certain number of technical terms is unavoidable, and explanations of these can be found in most biological dictionaries or the glossary of invertebrate pathology prepared by Steinhaus and Martignoni (1970).

Traditionally, intercellular communication and the regulation of biological functions of the body have been considered the role of two major and distinct systems: the nervous system and the endocrine system. The classic nervous system transmitted its signal rapidly by using electrical currents, whereas the signals used by the endocrine system were hormones produced by endocrine glands which reached the target tissues via the blood stream. During the past few decades, it has become apparent that these systems of intercellular com munication are not distinct and the signal messenger molecules are not unique to one or the other system. Many classic endocrine hormones are found in and act on nervous tissues and evidence exists for their de novo synthesis by neural related tissues. An exciting development in this area is the possibility that insulin and insulin-like growth factors (IGF) are not only produced by neural tissues but also exert profound physiological and biochemical effects on these tissues. The area of investigation of CNS insulin and IGF has been expanding rapidly and the availability of this book complete with up-to-date reviews on the subject by leaders in the field allows other scientists to utilize the knowledge in planning and adapting the latest ideas for future experiments. In addition, the book provides a collection of up-to-date articles for teachers to be used for the latest instructional material. The first section of the book covers general aspects of insulin receptors and insulin action."

The 21st century has seen the beginnings of a great restoration effort towards the world's forests, accompanied by the emergence of an increasing literature on reforestation, regeneration and regrowth of forest cover. Yet to date, there is no volume which synthesises current knowledge on the extent, trends, patterns and drivers of reforestation. This edited volume draws together research from leading researchers to explore reforestation and forest regrowth across the world, from multiple dimensions - including ecosystem services, protected areas, social institutions, economic transitions, remediation of environmental problems, conservation and land abandonment - and at different scales. Detailing the methods and analyses used from across a wide range of disciplines, and incorporating research from North, South and Central America, Africa, Asia and Europe, this groundbreaking book provides a global overview of current trends, explores their underlying causes and proposes future forest trajectories. The first of its kind, the book will provide an invaluable reference for researchers and students involved in interdisciplinary research and working on issues relevant to the biophysical, geographic, socioeconomic and institutional processes associated with reforestation.

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.