Root disease epidemics, because much of the activity takes place in soil and out of sight, pose special challenges to growers who seek to manage them and to scientists who study them. All relevant topics of root disease epidemics and their management are presented: The critical aspects of specific disease components including inoculum, host roots, mycorrhiza and the soil environment are explored. Challenges of disease assessment and the temporal and spatial aspects of epidemic development are considered, and approaches to root disease management including host resistance, chemical, biological and cultural management are discussed in detail. The book fulfills the needs of researchers, teachers, and practitioners of plant pathology.

Most books on epidemiology have treated the subject from a statistical, mathematical or computer applicational point of view. However, experiments must be performed first to provide the data for models which in turn can then be proven by further experimentation. This mutual interplay of theory and empirics gives epidemiology its scientific thrust and charm. This book provides a choice of methods for varying applications and objectives, covering all important aspects for the designing of experiments. Furthermore, the reader is supplied with solutions to his experimental problems and many "tricks of the trade." The newcomer to the field will also profit by this methodology guide.

Tropical climates, which occur between 23 Degrees30'N and S latitude (Jacob 1988), encompass a wide variety of plant communities (Hartshorn 1983, 1988), many of which are diverse in their woody floras. Within this geographic region, temperature and the amount and seasonality of rainfall define habitat types (UNESCO 1978). The F AO has estimated that there 1 are about 19 million km of potentially forested area in the global tropics, of which 58% were estimated to still be in closed forest in the mid-1970s (Sommers 1976; UNESCO 1978). Of this potentially forested region, 42% is categorized as dry forest lifezone, 33% is tropical moist forest, and 25% is wet or rain forest (Lugo 1988). The species diversity of these tropical habitats is very high. Raven (1976, in Mooney 1988) estimated that 65% of the 250,000 or more plant species of the earth are found in tropical regions. Of this floristic assemblage, a large fraction are woody species. In the well-collected tropical moist forest of Barro Colorado Island, Panama, 39. 7% (481 of 1212 species) of the native phanerogams are woody, arborescent species (Croat 1978). Another 21. 9% are woody vines and lianas. Southeast Asian Dipterocarp forests may contain 120-200 species of trees per hectare (Whitmore 1984), and recent surveys in upper Amazonia re corded from 89 to 283 woody species ~ 10 cm dbh per hectare (Gentry 1988). Tropical communities thus represent a global woody flora of significant scope.

This volume presents a body of research conducted over more than thirty years, including an intensive interdisciplinary five-year study begun in 1991. Chapters include studies of the relationships of biogeography and climate to the region's air pollution, the chemical and physiological mechanisms of ozone injury, as well as the impacts of nitrogen-containing pollutants and natural stresses on polluted forests.

The Dictionary contains the names of nearly 2500 plant species, in some cases including subspecies and varieties. Tropical crops from all parts of the world receive the same attention as those from the temperate zone. Common names are given not only in English, French, German, Portuguese and Spanish but also in many other languages, where such names are used in the technical literature. Agronomic plants' comprise not only the agricultural and horticultural crops but also pasture plants, green manure, soil covers, trees used in agroforestry, and major weeds. Also included are plants which are presently being discussed as new crops, with considerable economic value. The Dictionary will meet the needs not only of scientists in agriculture, botany and geography but also those of agricultural extensionists, merchants in agricultural products and professional translators.

Based on papers presented at the International Symposium on Sexual Reproduction in Higher Plants, this volume covers the topics: micro- and macrosporogenesis, the activation and recognition of mature pollen, pollen germination and tube emission in vivo and in vitro, pollen and pollen tube cytoskeleton, stigma and style morphology, pollen/stigma interactions, incompatibility mechanisms and gene expression. The reinvestigation of classical topics using modern methods such as immunofluorescence, micromanipulation, freeze-substitution, electron microscopy, etc., is the common basis of all results presented. Especially applied aspects of sexual reproduction important e.g. for crop improvement, are discussed in detail.

The understanding of pollutant transformations, sorption and transport in soils and uptake by plants is the key to controlling contaminant movement towards groundwater and accumulation in food-chains. Some of these major processes were discussed in the first International Workshop on Pollutants in Porous Media, con vened in Israel in 1983 (pollutants in Porous Media, Eds. Yaron, Dagan and Goldshmid, Springer-Verlag, 1984). Since that meeting, research on contaminant impact on the environment expanded considerably. New mechanisms explaining inorganic pollutant par titioning between solid and solution phases in soils were proposed and tested; specific elements and specific reactions were investigat ed, and more case studies to evaluate management practice effects on drinking water quality and accumulation of contaminants in crops were carried out. The recognition that the new knowledge needs to be discussed and evaluated, and the scientific and engineering communities be updated, led the IUPAC (Interna tional Union of Pure and Applied Chemistry) and IAHS (Interna tional Association of Hydrological Sciences) Water Quality Com missions to organize a second International Workshop on pollu tant behaviour in the vadose zone, hosted by the Institute of Soils and Water of the Agricultural Research Organization, Israel. In this workshop, taking place in June 1987, attention was focused on chemical, physico-chemical and microbial-mediated reactions of different contaminants in the vadose zone. This book contains selected works presented in the 1987 workshop by invited special ists from various disciplines and countries."

Advances in Soil Science is a review series relevant to all areas of soil science. These reviews, intended primarily for scientists, teachers, and students of soil science, also provide technical background information for many additional workers and groups interested in our natural resources and man's influence on them. This is the eighth volume in the series with an international list of contributors from the United States, India, Canada and New Zealand. It contains four review chapters on the following subjects: factors affecting aluminum transformations in soil; soil productivity in dryland regions of developing countries; changes in soil structure under different cropping systems; properties and management of the depleted soils of India. These contributions present valuable information on a diversity of topics and serve as an excellent source of references.

Starting with the description of meteorological variables in forest canopies and its parameter variations, a numerical three-dimentional model is developed. Its applicability is demonstrated, first, by wind sheltering effects of hedges and, second, by the effects of deforestation on local climate in complex terrain. Scientists in ecology, agricultural botany and meteorology, but also urban and regional lanners will profit from this study finding the most effective solution for their specific problems.

A year has passed since Eshel Bresler, my good friend and colleague, and a member of the editorial board of the Advanced Series in Agricultural Sciences, died suddenly while on a visit to the Chinese Academy of Sciences in Beijing. We had worked together for almost 30 years at the Institute of Soils and Water, ARO, The Volcani Center at Bet Dagan. At the very beginning of our scientific careers we cooperated directly and as a result one of our first publications was coauthored (Soil Sci. 101:205-209, 1966). Thereafter, our specific research interests diver sified, but we continued to work together, with similar approaches to research, and to strive towards the development of Israel soil science and its integration into general worldwide scientific progress. I don't need to emphasize Eshel's contribution to the understan ding of the processes governing water flow and solute transport pro cesses in soils and unsaturated zones. The contributions to this Volume by such a body of outstanding scientists shows the apprecia tion of the international scientific community to his research achievements."

With one new volume each year, this series keeps scientists and advanced students informed of the latest developments and results in all areas of botany.
The present volume includes reviews on structural botany, plant taxonomy, physiology, genetics and geobotany.

In November 1988 the "'Third Oberursel Symposium" devoted to the problems of input of pollutions into forest-ecosystems and their effects on plants or soil convened. After several years of intensive research on the effects of pollutions on forest ecosystems it is obvious that not a single specific pollutant can be made responsible but a mixture of several components act together or interact with each other. The contributions of the workshop _ reflect to a large extend the results of research projects which were started at the beginning of the eighties. They review our improved knowledge on the patterns of concentration, of the mechanism of wet and dry deposition and fog interception, modelling studies and the effect of the processes on plant receptors and surfaces. Since the 1985 symposium the pathways of pollutants leading to biological damage have been examined and are more clearly recognised. The book reflects the common interest and the continuous effort of scientists from many different disciplines to better understand the physical and chemical processes which finally lead to the observed damage of forest-trees. Comparing the conclusions of the contributions of this book _ with the results of the first Oberursel symposium in 1981, our knowledge on the relevance of the different mechanisms leading to forest-decay has been considerably improved. The book indicates also in which directions future work should be concentrated. Again, I have to thank the authors for their cooperation by submitting their recent research-results."

In 1977, the Volkswagen Foundation sponsored the first of a series of International Symposia on Fire Ecology at Freiburg University, Federal Republic of Germany. The scope of the congresses was to create a platform for researchers at a time when the science of fire ecology was not yet recognized and established outside of North America and Australia. Whereas comprehensive information on the fire ecology of the northern boreal, the temperate, and the mediter ranean biotas is meanwhile available, it was recognized that conside rable gaps in information exist on the role of fire in tropical und sub tropical ecosystems. Thus it seemed timely to meet the growing scientific interest and public demand for reliable and updated infor mation and to synthesize the available knowledge of tropical fire ecology and the impact of tropical biomass burning on global eco system processes. The Third Symposium on Fire Ecology, again sponsored by the Volkswagen Foundation and held at Freiburg University in May 1989, was convened to prepare this first pantropical and multidisci plinary monograph on fire ecology . The book, in which 46 scientists cooperated, analyzes those fire-related ecosystem processes which have not yet been described in a synoptic way. Following the editor's concept, duplication at previous efforts in describing tropical vegeta tion patterns and dynamics was avoided. Extensive bibliographical sources are given in the reference lists of the chapters."

Deals with biotechnological approaches incorporated into po- tato improvement progammes. These methods have far-reaching implications for the synthesis of improved, disease- resist- ant and nutritious cultivars of potato.

When trying to solicit authors for this book it became apparent that the causal factors for heterosis at the physiological and biochemical level are today almost as obscure as they were 30 years ago. Though biometrical-genetical analyses point to dispersion of complementary genes - not overdominance - as the major cause of the phenomenon, plant breeders' experience still suggests a cautious, pragmatic approach to the dominance-overdominance controversy in breeding hybrid cultivars. Thus we are faced with a striking discordance between our limited comprehension of the causal factors and mechanism of heter osis on the one hand, and the extensive agricultural practice of utiliza tion of hybrid vigor on the other. Such utilization is the result of the economic value of hybrid combinations displaying superior yields and qualities as well as stability of performance, of benefits derived in breeding programs, and of the enhanced varietal protection of proprietary rights. No comprehensive and critical analysis of the phenomenon of heterosis in economic plants has been published for the last three decades since the now classical book Heterosis, edited by J . W. Gowen (Iowa State College Press, Ames, Iowa, 1952). The present book attempts to fill the gap and to assess the status of our present knowl edge of the concept, the basis, the extent, and the application of heterosis in economic plants."

Soils will play a central role in mediating the impact of climate change on natural and managed ecosystems.
The book addresses the various responses of soil processes and properties to environmental change and highlights their contribution to the proper understanding of ecosystem behaviour.
Topics include: Soil hydrology; landscape evolution; salinisation; desertification; soil nitrogen dynamics; soil carbon; soil microbiology; soil erosion; crop modelling.

Legumes and oilseed crops are a rich source of protein and energy. The major objectives in grain-legume breeding are to increase grain yield, protein quantity and quality and digestibility, and to decrease toxic fac- tors, seed hardness and cooking time. Similarly, oilseed crops such as brassicas and peanut share somewhat similar genetic improvement goals, but suffer from susceptibility to a number of pathogens and diseases. In spite of the best efforts through conventional breeding, their yield has been virtually static, with no significant breakthrough. The lack of genetic variability in the base population has been considered to be a major limiting factor for the slow progress made in the improvement of these crops. The desired goals can be achieved by incorporating addi- tional genetic variability in the existing germplasm. The protein and oil contents which are genotypically oriented can be enhanced further by suitable crosses. In this regard, progress made during the last decade, in the area of in vitro manipulation and recombinant DNA technology, holds promise for the improvement of these crops. Among the oilseed crops, Brassica spp. , soybean and sunflower have been well studied, wherein haploids, somaclones, somatic hybrids, cybrids and transformed plants have been produced. Oilpalm is one of the best examples where micropropagation is being commercially prac- ticed. Regarding legumes, though there is extensive work on forages, such as Medicago and Trifolium, much needs to be done on food legumes.

Forty chapters deal with various aspects of tissue culture, in vitro manipulation, and other biotechnological approaches to the improvement of maize.
They are arranged in eight sections: - In Vitro Technology, Callus Cultures and Regeneration of Plants, Somatic Embryogenesis. - Wide Hybridization, Embryo, Ovule, and Inflorescence Culture, in Vitro Fertilization. - Production of Haploids and Double Haploids, Anther and Pollen Culture. - Protoplast Culture, Genetic Transformation. - Somaclonal Variation and Mutations. - Molecular Biology and Physiological Studies. - Proteins and Nutritional Improvement. Pollen Storage, Cryopreservation of Germplasm.

Salinization of soils is a major threat to irrigated agriculture and counteracts the targets of costly public infrastructure investments. In this study, salinization is regarded as the outcome of an institutional arrangement which impedes the effective implementation of well-known and well-established control measures be they technical, managerial or economic. In public irrigation systems neither the management units nor the farmers are offered any incentives towards the control of high groundwater levels and salinization if the management units are embedded in a highly centralized non-market institutional setting. The author answers the question under which conditions management units and irrigators are active in halting and reversing the process of salinization.

Of all the food produced in the world one third is lost to insect pests, weeds and diseases, and the total world population is estimated as growing from 4000 million in 1975 to about 6000 million by the year 2000. To satisfy these needs, the world's farmers must meet the extra requirement every year. The easiest way in which farmers can increase the amount of food they produce is to prevent the loss due to pests. The biological control measures which were once thought to be the safest methods of pest control have, as we now know, not proved successful on a commercial scale. In such a dismal situation the only solution is to use pesticides to save the losses from pests and to increase the crop yield. Apart from agriculture, pesticides have also contributed much to human com fort by controlling the vectors of typhoid, malaria, sleeping sickness, filariasis, dengue hemorrhage fever, plague etc. On the other hand, the indiscriminate use of insecticides and their harmful effects on nontarget organisms has attracted much attention from people in all walks of life, for example, scientists, administrators, the press and the public. The harmful effects of insecticides on higher organisms such as birds, fish and mammals are easy to observe and have received much attention. However, the interactions of insecticides with microorganisms such as bacteria, fungi, algae and protozoa have gone unnoticed until recently."

Recently, the pharmaceutical industry has shown considerable interest in the en masse micropropagation of elite plants, and the large-scale produc- tion of secondary metabolites in plant cell cultures through the use of bioreactors. This is now being realized by the selection of high-yielding somac1ones or through the production of hairy roots by transformation with Agrobacterium rhizogenes. These new developments need to be high-lighted and brought to the attention of workers dealing with medicinal, aromatic, and other plants of industrial importance. A series of books on the biotech- nology of medicinal and aromatic plants is therefore being compiled to provide a survey of the literature focusing on recent information and the state of the art. This book, Medicinal and Aromatic Plants IV, like the previous three volumes (Medicinal and Aromatic Plants I, II, and III, published in 1988, 1989, and 1991, respectively) is unique in its approach. It comprises 28 chapters dealing with the distribution, economic importance, conventional propagation, review of tissue culture studies, and the in vitro production of important medicinal and pharmaceutical compounds in various species of Ammi, Bergenia, Canavalia, Capsicum, Cassia, Cephaelis, Cornus, Cucurbita, Elettaria, Eupatorium, Genipa, Gentiana, Gypsophila, Hygrophila, Leon- topodium, Nerium, Picrasma, Polygonum, Ptelea, Rheum, Scopolia, Silene, Solanum, Strophanthus, Tagetes, Thymus, and Uncaria. This book is tailored to the needs of advanced students, teachers, and research workers in the fields of plant biotechnology and chemical engineer- ing, pharmacy, botany, and phytochemistry.

In continuation of Volumes 8 and 9 (1989) on in vitro manipulation of plant protoplasts, this new volume deals with the regeneration of plants from protoplasts and genetic transformation in various species of Agrostis, Arabidopsis, Atropa, Brassica, Catharanthus, Datura, Cucumis, Daucus, Digitalis, Duboisia, Eustoma, Festuca, Helianthus, Hordeum, Kalanchoe, Linum, Lobelia, Lolium, Lotus, Lycium, Lycopersicum, Mentha, Nicotiana, Pelargonium, Pisum, Pyrus, Salvia, Scopolia, and Solanum.These studies reflect the far reaching implications of protoplast technologyin genetic engineering of plants. They are of special interest to researchers in the field of plant tissue culture, molecular biology, genetic engineering, and plant breeding.

In keeping with the spirit of an Advanced Series in the Agricultural Sciences, we have attempted to address herein most of the current research areas being used to characterize, describe and manage salt-affected soils. Because of a certain amount of personal bias inherent in our individual viewpoints and backgrounds, some areas have been accorded more emphasis than others. It has been our goal, however, to provide either detail about, or at least a recent reference to, each major area of current soil salinity research. This information, coupled with what we hope to be a rather logical progression from descriptive material on equilibrium or near-equilibrium soil chemistry, through transport processes, to eventual management practices including some elementary economic decisions, should enable the reader to bridge the gap from introductory soil chemistry or soil physics texts to the basic literature of this area. The text will be perceived by the astute reader as somewhat uneven in its treatment of respective sections. We feel that this is to a certain extent appropriate, for it thus portrays the unevenness of progress to date in the corresponding areas of research. The management of saline and sodic soils remains largely an empirical semi-science or even art, whereas transport phenomena are normally dealt with in a much more theoretical (and also a much more highly mathematical) vein. Equilibrium soil chemistry has historically occupied an intermediate position with respect to its mix of empiricism and theoretical rigor.

Although biologists have directed much attention to estimating the extent and causes of species losses, the consequences for ecosystem functioning have been little studied.
This book examines the impact of biodiversity on ecosystem processes in tropical forests - one of the most species-rich and at the same time most endangered ecosystems on earth. It covers the relationships between biodiversity and primary production, secondary production, biogeochemical cycles, soil processes, plant life forms, responses to disturbance, and resistance to invasion. The analyses focus on the key ecological interfaces where the loss of keystone species is most likely to influence the rate and stability of ecosystem processes.