Many agricultural crops worldwide, especially in semi-arid climates, suffer from iron deficiencies. Among plants sensitive to iron deficiency are apples, avocado, bananas, barley, beans, citrus, cotton, grapes, peanuts, pecans, potatoes, sorghum, soybeans, and numerous ornamental plants. Deficiencies are usually recognized by chlorotic, in new leaves and are typically found among sensitive crops grown in calcareous or yellowed, interveinal areas soils which cover over 30% of the earth's land surface. Iron deficiency may lead, in extreme cases, to complete crop failure. In intensive agriculture on calcareous soils, iron often becomes a major limiting nutrient for optimal crop production, thus, correction of iron deficiency is required. Various chemicals and practices are available. They are, however, costly and do not always result in a complete remedy of the deficiency. Crucial questions relative to the cost-benefit equation such as the recovery rate of plants and the long-term fertilizing effect have not yet been resolved. The complexity of iron nutrition problems requires an understanding of the chemistry of iron oxides in soils, of the chemistry of both natural and synthetic chelates, of rhizosphere microbiology and biochemistry, and of the physiological involvement of the plant in iron uptake and transport.

The study of plant development using molecular and genetic techniques is rapidly becoming one of the most active areas of research on flowering plants. Developmental Biology of Flowering Plants relates classical developmental work with the outstanding problems of the future in the study of plant development. An important feature of this book is the integration of results from molecular and genetic studies on various aspects of plant development in a cellular and physiological context.

In recent decades, repeated use of herbicides in the same field has imposed selection for resistance in species that were formerly susceptible. On the other hand, considerable research in the private and public sectors has been directed towards introducing herbicide tolerance into susceptible crop species. The evolution of herbicide resistance, understanding its mechanisms, characterisation of resistant weed biotypes, development of herbicide-tolerant crops and management of resistant weeds are described throughout the 36 chapters of this book. It has been written by leading researchers based on the contributions made at the International Symposium on Weed and Crop Resistance to Herbicides held at Cordoba, Spain. This book will be a good reference source for research scientists and advanced students.

In vitro Embryogenesis in Plants is the first book devoted exclusively to this topic. As the ultimate demonstration of totipotency in plants, somatic and haploid embryogenesis is of vital importance to all those working on or interested in basic and applied aspects of plantlet information and regeneration. The text includes comprehensive reviews written by experts, on all facts of in vitro and in vivo embryogenesis. Some chapters deal with the morphogenic, structural and developmental, physiological and biochemical, and molecular biological aspects of the subject. Chapters are also devoted to haploid embryogenesis, asexual embryogenesis in nature, zygotic embryogenesis, and zygotic embryo culture. Detailed tables summarizing successful somatic embryogenesis in all vascular plants are also included. This book, therefore, brings together previously scattered information to provide an indispensable reference book for both active researchers, graduate students and anyone interested in this aspect of tissue culture technology and plant development.

With an ever-increasing demand for more food supply, agricultural scientists will have to search for new ways and technologies to promote food production. In recent decades, plant growth regulators (PGRs) have made great strides in promoting plant growth and development. PGRs are organic compounds which have the ability to dramatically affect physiological plant processes when present in extremely low concentrations (in the range of micro-to picograms). Although all higher plants have the ability to synthesize PGRs endogenously, they do respond to the exogenous sources most likely due to not having the capacity to synthesize sufficient endogenous phytohormones for optimal growth and development under given climatic and environmental conditions. In recent years, PGRs have established their position as a new generation of agrochemicals after pesticides, insecticides and herbicides. Interest in the commercial use of PGRs for improving plant growth and crop yields is also increasing because of their non-polluting nature. The use of PGRs in the post-harvest technology is well established and many new breakthroughs have recently been revealed.

Over forty years ago, concern was first focussed on cadmium contamination of soils, fertilisers and the food chain. Adverse effects on human health were first highlighted nearly 30 years ago in Japan with the outbreak of Itai-itai disease. Since then, substantial research data have accumulated for cadmium on chemistry in soils, additions to soils, uptake by plants, adverse effects on the soil biota and transfer through the food chain. However, this information has never been compiled into a single volume. This was the stimulus for the Kevin G. Tiller Memorial Symposium "Cadmium in Soils, Plants and the Food Chain", held at the University of California, Berkeley, in June 1997 as part of the Fourth International Conference on the Biogeochemistry of Trace Elements. This symposium brought together leading scientists in the field of cadmium behaviour in soils and plants, to review the scientific data in the literature and highlight gaps in our current knowledge of the subject. This series of review papers are presented here and deal with the chemistry of cadmium in soils, the potential for transfer through the food chain and management to minimise this problem. We hope this information provides a sound scientific basis to assist development of policies and regulations for controlling cadmium in the soil environment.

Tea is a unique crop and, incidentally, a very interesting and attractive one. The tea bush, its cultivation and harvesting do not fit into any typical cropping pattern. Moreover, its processing and marketing are specific to tea. Thus the Tea Industry stands apart and constitutes a self contained entity. This is reflected in the title given to this book, Tea: Cultivation to consumption, and its treatment of the subject. The book is logically planned - starting with the plant itself and finishing with the traditional'cuppa'. Every aspect of tea production is covered, inevitably some in greater detail than others. However, it gives an authentic and comprehensive picture of the tea industry. The text deals in detail with cultural practices and research, where desirable, on a regional basis. The technology of tea cultivation and processing has been developed within the industry, aided by applied research which was largely financed by the tea companies themselves. This contributed to a technically competent industry but tended to bypass the more academic and fundamental investigations which might bring future rewards. The sponsorship of research has now widened and the range and depth of tea research has increased accordingly. The editors and authors of this book have played their part in these recent developments which are well reported in the book.

Science is essentially a descriptive and experimental device. It observes nature, constructs hypotheses, plans experiments and proposes theories. The theory is never contemplated as the 'final truth', but remains ever subject to modifications, changes and rejections. The science of allelopathy in a similar way has emerged, and exists on a similar footing; our endeavour should be to keep it fresh and innovative with addition of newer in formation and concepts with the rejection of older ideas and antiquated techniques. During the past few decades encouraging results have been obtained in various aspects of allelopathic researches. However, in addition to continuing efforts in all these directions, constant attempts are to be made to describe the mechanics of allelopathic activity in molecular terms and to discover ways and means to exploit it for the welfare of mankind. We feel that multidisciplinary efforts are the only tool to achieve this goal. It is the hope of the editors that this book will serve as a document which identifies an integrated approach, through which research both to understand and exploit allelopathy can be conducted. The present volume arose out of an attempt to bring together eminent scientists in allelopathy to describe their work, of a highly diverse nature, under one title."

However, the transition from primitive to 'advanced' cultivars has had the effect of narrowing the genetic base. This has happened in two distinct ways: (1) selection for relative uniformity, resulting in 'pure' lines, multi lines, single or double hybrids, etc.; and (2) selection for closely defined objectives. Both of these processes have resulted in a marked reduction in genetic variation. At the same time, there has been a tendency to restrict the gene pool from which parental material has been drawn. This is a result of the high level of productivity achieved when breeding within a restricted but well-adapted gene pool, and of breeding methods which have made it possible to introduce specifically desired improvements, such as disease resistance and quality characteristics, into breeding stocks with a minimum of disturbance to genotypic structure. Developments in agriculture, such as intensive mechanization, the widespread application of fertilizers and the use of herbicides, fungicides and pesticides, have created a situation whereby a few, selected high yielding cultivars may be grown over large parts of the earth, so further contributing to a decline in crop genetic diversity. This process is under way in all countries, both developed and developing, and unfortunately in cludes some of the richest primary and secondary gene centres of several important food crops."

Chemical reactions and interactions between molecules are commonly considered the basis of life, and thus the biochemical nature of cells and organisms is relatively well recognized. Research conducted in recent years, however, increasingly indicates that physical forces profoundly affect the functioning of life at all levels of its organization. To detect and to respond to such forces, plant cells and plants need to be structured mechanically. This volume focuses on mechanical aspects of plant life. It starts with a consideration of the mechanical integration of supracellular structures and mechanical properties of cellular building blocks to show how the structural integrity of plant cells is achieved and maintained during growth and development. The following chapters reveal how the functioning of integrated plant cells contributes to the mechanical integration of plants, and how the latter are able to detect physical stimuli and to reorganize their own cells in response to them. The mechanical aspects of plant responses to stresses are also presented. Finally, all these aspects are placed in an evolutionary context.

The 1997 European Conference on Spectroscopy of Biological Molecules (ECSBM) is the seventh in a biennial series of conferences devoted to the applications of molecular spectroscopy to biological molecules and related systems. The interest of these conferences rests mainly on the relationship between the structure and physiological activity of biological molecules and related systems of which these molecular species form part. This volume ofECSBM contains articles prepared by the invited lecturers and those making poster presentations at the seventh ECSBM. The reader will find mainly applications of vibrational spectroscopy to protein structure and dynamics, biomembranes, molecular recognition, nucleic acids and other biomolecules and biological systems containing specific chromophors. Biomedical applications of vibrational spectroscopy are expanding rapidly. On the other hand, a significant number of the papers describe applications of other methods, such as NMR, circular dichroism, optical absorption and fluorescence, X-ray absorption and diffraction and other theoretical methods. One aim has been to achieve a well balanced, critically comparative review of recent progress in the field of biomolecular structure, bonding and dynamics based on applications of the above spectroscopic methods. A great part of the contributions included in this volume are devoted to biomedical and biotechnological applications and provide a broadly based account of recent applicationS in this field. The content of this book has been organized in sections corresponding mainly to the different types of biological molecules investigated. This book includes also another section related to theoretical methods where MO calculations of vibrational frequencies dominate clearly the topic.

This volume contains selected papers presented at the First Balkan Botanical Congress. The articles refer to all groups of plants and to all scientific disciplines in plant sciences and cover several major themes of current interest to botanists: taxonomy, geobotany and evolution: flora, vegetation, geographical distribution, pollen morphology and deposition, biodiversity, conservation, phytosociology biochemistry, metabolism and bioenergetics: secondary metabolites, enzymes, membrane transport, virus infection ecology and ecophysiology: metal accumulation and tolerance, toxicity and pollution, bio-monitoring systems, dynamics of vegetation communities, leaf structure and ecological types, UV-B and ozone radiation, pesticides and herbicides, ecological evaluation, management and protection of ecosystems, adaptation, photosynthesis structure and its dynamics: organization and molecular characterization of biomembranes and different cell structures and organelles, ultrastructure, anatomy, biosynthesis and localization of different cell compounds genetics, plant breeding and biotechnology: gene transfer, genetic engineering, genetic sterility and diversity, biodiversity and conservation, in vitro regeneration, micropropagation, genotype-environment interaction growth, development and differentiation: differentiation of cell structures, reproductive biology, photoreceptors, crop simulation model, regulators and plant morphogenesis, plant growth patterns, somatic-embryogenesis and organogenesis.

Plant-Microbe Interactions, Volume 2 Volume 1 of this series has made its appearance and dealt forcefully with impor tant current topics in the field of plant-microbe interactions. We believe that the quality of those chapters was high and should serve as a focal point for the state of the art as well as an enduring reference. Volume 2 builds upon these accom plishments. Chapter 1 discusses the fascinating lipo-chitin signal molecules from Rhizo bium, aspects regarding their biosynthesis, and the basis for host specificity. These molecules are a cardinal example of how microorganisms influence plant development and stimulate speculation that they have identified a previously un known aspect of plant hormone activity. Chapter 2 continues the discussion of Rhizobium by considering the trafficking of carbon and nitrogen in nodules. Al though the ostensible advantage of nodules to plants is the fixation of atmos pheric nitrogen, the actual process involved in supplying reduced nitrogen to the plant host is complex."

For 31 years, the North American Symbiotic Nitrogen Fixation Conference (for merly Rhizobium Conference) has been a forum for scientists and graduate students to discuss their research advances, extending from basic aspects to agricultural appli cations, and dealing with topics ranging from bacterial genetics and metabolism to plant genetics and physiology. Nitrogen fixation, being a major life-supporting process on this planet, has attracted the interest of researchers for more than one century. Nitrogen fixation is responsible for the conversion of "inert" dinitrogen (N ) gas from the atmos z phere into usable ammonia, replacing the fixed nitrogen constantly being lost to the atmosphere by the denitrification process. Worldwide agricultural productivity is deter mined by the availability of fixed nitrogen in all its forms, which the continually increas ing human population depends upon for survival. An international momentum is developing in the use of biofertilizers to improve legume and non-legume crop yields and in the study of genomics in this area. New studies are being undertaken in several laboratories to study novel nitrogen-fixing systems, including non-legume crops. The North American Conferences on Symbiotic Nitrogen Fixation have periodically chronicled the advances in our knowledge of this area. For the first time, this conference was held in Mexico. Thus, all three North Amer ican countries have been hosts for this event. This year conference brought nearly 200 scientists from 18 different countries presenting lectures and over 80 posters.

The International Society of Root Research sponsored the Symposium "Root Demographics and Their Efficiencies in Sustainable Agriculture, GrassLands and Forest Ecosystems," July 14-18, 1996, at the Madren Conference Center, Clemson University, Clemson, South Carolina, USA. The conference was a continuation of a series of international symposiums on root research held every three to four years. Symposiums have also been held twice in Vienna, Austria, and once in Uppsala, Sweden, and Almaty, Kazahkstan prior to the meeting at Clemson University. The sponsoring society has made a particular effort in these symposia to include root scientists from the former Soviet Union because of the importance of exchanging information on a worldwide basis. This symposium continued and promoted that effort by providing travel grants to several scientists from that region; however, funds for that purpose were limited. Therefore, in compiling these proceedings, a number of papers from scientists from the former Soviet Union and former Warsaw Pack countries have been included even though the scientists were not actually present for the SymPOSIum.

From its inception, the U.S. Department of the Interior has been charged with a conflicting mission. One set of statutes demands that the department must develop America's lands, that it get our trees, water, oil, and minerals out into the marketplace. Yet an opposing set of laws orders us to conserve these same resources, to preserve them for the long term and to consider the noncommodity values of our public landscape. That dichotomy, between rapid exploitation and long-term protection, demands what I see as the most significant policy departure of my tenure in office: the use of science-interdisciplinary science-as the primary basis for land management decisions. For more than a century, that has not been the case. Instead, we have managed this dichotomy by compartmentalizing the American landscape. Congress and my predecessors handled resource conflicts by drawing enclosures: "We'll create a national park here," they said, "and we'll put a wildlife refuge over there." Simple enough, as far as protection goes. And outside those protected areas, the message was equally simplistic: "Y'all come and get it. Have at it." The nature and the pace of the resource extraction was not at issue; if you could find it, it was yours.

All biomass is derived from photosynthesis. This provides us with food fuel, as well as fibre. This process involves conversion of solar energy, via photochemical reactions, into chemical energy. In plants and cyanobacteria, carbon dioxide and water are converted into carbohydrates and oxygen. It is the best studied research area of plant biology. We expect that this area will assume much greater importance in the future in view of the depleting resources ofthe Earth's fuel supply. Furthermore, we believe that the next large increase in plant productivity will come from applications of the newer findings about photosynthetic process, especially through manipulation by genetic engineering. The current book covers an integrated range of subjects within the general field of photosynthesis. It is authored by international scientists from several countries (Australia, Canada, France, India, Israel, Japan, Netherlands, Russia, Spain, UK and USA). It begins with a discussion of the genetic potential and the expression of the chloroplast genome that is responsible for several key proteins involved in the electron transport processes leading to O evolution, proton release and the production of 2 NADPH and A TP, needed for CO fixation. The section on photosystems discusses 2 how photosystem I functions to produce NADPH and how photosystem II oxidizes water and releases protons through an "oxygen clock" and how intermediates between the two photosystems are produced involving a "two electron gate".

In this study, an overview is presented of agricultural policies on manure and minerals, relating to the Nitrate Directive to remedy excessive surface- and groundwater contamination from intensive agricultural practices. Six countries belonging to the European Union were studied: the Netherlands, Belgium, Denmark, France, Germany and the United Kingdom. The policies and their legal incorporation were related to agricultural and environmental conditions in each country. In addition, an inventory was made of agricultural mineral poli cies in the United States and Canada. Conditions for livestock farming in North America differ considerably from those in Europe, but their solutions shed a different light on European policies. Research has shown that there are still very considerable mineral surpluses in many countries and regions. In both the Netherlands and in the Flemish part of Belgium, existing problems due to very high levels of manure production are structural rather than local and cannot easily be solved by transport of manure to other regions. To a lesser extent. Germany, Denmark and relatively small parts of France (Brittany) and the United Kingdom, still exceed the norms for an equilibrium fertilization. In Denmark, existing problems can probably be solved within the existing legislative framework. The Netherlands, Flanders. several German Lander (Nordrhein-Westfalen and Schleswig-Holstein) and Brittany.

Many plants produce enzymes collectively known as ribosome-inactivating proteins (RIPs). RIPs catalyze the removal of an adenine residue from a conserved loop in the large ribosomal RNA. The adenine residue removed by this depurination is crucial for the binding of elongation factors. Ribosomes modified in this way are no longer able to carry out protein synthesis. Most RIPs exist as single polypeptides (Type 1 RIPs) which are largely non-toxic to mammalian cells because they are unable to enter them and thus cannot reach their ribosomal substrate. In some instances, however, the RIP forms part of a heterodimer where its partner polypeptide is a lectin (Type 2 RIPs). These heterodimeric RIPs are able to bind to and enter mammalian cells. Their ability to reach and modify ribosomes in target cells means these proteins are some of the most potently cytotoxic poisons found in nature, and are widely assumed to play a protective role as part of the host plant's defenses. RIPs are able to further damage target cells by inducing apoptosis. In addition, certain plants produce lectins lacking an RIP component but which are also cytotoxic. This book focuses on the structure/function and some potential applications of these toxic plant proteins.

Since 1994, the Phytochemical Society of North America has devoted its annual symposia to topics with biological perspectives. Our last four volumes have dealt with medicinal plants (1994), plant/insect interactions (1995), food phytochemicals (1996), and plant/microbe interactions (1997), respectively. The Symposium held in Pullman, Washington, July 26-31, 1998 brought many aspects of these previous symposia once again to the forefront. This time, however, there was greater emphasis on the potential applications of phytochemistry to the diverse topics of human health and nutrition and plant defense. As we learned about innovative uses of molecular biology as it is being applied to these topics, we were reminded once again of the biochemical th foundation on which these advances rest. On the occasion of the 75 birthday of G.H. Neal Towers, which we were privileged to celebrate, a perspective of where we began and how far we have advanced was made patently real for those in attendance. The papers assembled in this volume were presented during the Sympo- sium. Roughly grouped under three broad topics, they include: I. Drug Discov- ery and Pathway Engineering toward New MedicinallNutriceutical Targets (papers by Cragg, Croteau, Thompson, Costa, McLaughlin, Dixon, and Matern), 2. Roles for Polyphenols-Biosynthesis and Applications (Gross, Hillis, Haslam, and Ferreira), 3. New Chemical Prospects and Plant Defense (Asakawa, Selmar, Houghton, and Mizutani).

The Monograph deals with the conception, planning, implementation, results and conclusions of the International Witches' Broom Project (IWBP), which was set up in 1985 with the aim of producing an economic management system for witches' broom disease of cocoa. The contributions of the various sponsors, and the roles played by the participating organizations and scientists are described in the introductory chapter. Chapter 2 provides a review of what was, and what was not known from published literature about the cocoa witches' broom pathosystem in 1989. The scope of the project and the approaches used are covered in Chapter 3, while Chapters 4 to 13 report on the field studies themselves in detail. The recent appearance of witches' broom in the important cocoa area of Bahia in Brazil is described in Chapter 14, before disease management recommendations are summarised and future prospects considered in the closing chapters. The many man-years of field research in the IWBP in a total of six countries generated much useful information which was analyzed both in the individual countries and collectively. Even with a document of this size, certain information and analyses with less direct relevance to disease management had to be omitted. It is expected that more detailed treatments of certain aspects will emerge in scientific papers, and further analyses will be undertaken."

The dynamic role of plant hormones in regulation of plant growth and development revealed by its control of rates of metabolic processes and various related enzymetic reactions at molecular and submolecular levels is now weil established. During the course of last 35 years endless development in agricultural biotechnology has provided immense literature to understand hormone-regulated aspects of plant growth and development ; but plant physiologists all over the world are still devoting themselves and will continue for an indifinite period to disclose the mystries of this regulation. Volume I of this series has already been published and has been accepted weil. This encouraged me to edit aseries of volumes (I do not know the number) on this subject. In the following pages various aspects of hormone-controlled physiological processes Iike, Hormonal Control of pro tein synthesis in plants, Auxin-induced elongation, Hormonal regulation of abnormal growth in plants, Hormonal regulation of development in mosses, Some phenolics as plant growth and morphogenesis regulators, Plant growth regulating properties of sterol inhibiting fungicides, Hormonal regulation of sex expression in plants, Water relation and plant growth regulators, Hormonal regulation of root development under water stress, Gravity perception and responses meehanism in graviresponding cereal grass shoots, Hormonal regulation of leaf Growth senescence in relation to stomatal movement, and Chloroindole auxins of pea and related species, have been included.

The refinement of molecular techniques and the development of new probes of the phylogeny of diazotrophs has revealed an extreme biodiversity among the nitrogen fixers, which helps explain the role that nitrogen fixation plays in maintaining life on Earth. The most efficient ecosystems are those where the bacteria are associated with a plant in differentiated organs to benefit crop productivity. Most short-term benefit from fundamental research on nitrogen fixation is likely to result in the improvement of existing nitrogen-fixing symbiotic or associative systems. Longer-term efforts are aimed at extending the nitrogen-fixing capacity to other organisms, including transfer of the genetic information for efficient nitrogen fixation into the plant genome and using current knowledge of microbe-plant interactions to extend symbiosis to cereals and, in particular, to rice. Related challenges in sustainable agriculture and forestry include the creation of new nitrogen-fixing associations. All of these approaches were discussed at the 11th International Congress on Nitrogen Fixation, Paris, France, July 20-25, 1997 and covered in the present proceedings volume.

Plants live in a constantly changing environment from which they cannot physically escape. Plants therefore need signalling and response mechanisms to adapt to new local conditions. The ef?cacy of such mechanisms underlies the plant performance during stress and therefore also impacts greatly on agricultural productivity. M- ulation of ion channel activity not only provides a means for rapid signal generation 2+ but also allows adjustment of cellular physiology. For example, Ca permeable ion 2+ channels can transduce environmental stimuli into Ca -encoded messages which can modify the gene expression. Furthermore, ion channel activity is essential to control cellular ion homeostasis that impacts on plant responses to drought, salinity, pathogens, nutrient de?ciency, heavy metals, xenobiotics and other stresses. This volume focuses on the crucial roles of different types of ion channel in plant stress responses. Functions of ion channels are discussed in the context of mechanisms to relay external and endogenous signals during stress and as mechanisms to regulate cellular ion homeostasis and enzymatic activities in the context of biotic and abiotic stress. The chapters presented cover cation and anion channels located in various cellular compartments and tissues.

The double helix architecture of DNA was elucidated in 1953. Twenty years later, in 1973, the discovery of restriction enzymes helped to create recombi nant DNA molecules in vitro. The implications of these powerful and novel methods of molecular biology, and their potential in the genetic manipulation and improvement of microbes, plants and animals, became increasingly evi dent, and led to the birth of modern biotechnology. The first transgenic plants in which a bacterial gene had been stably integrated were produced in 1983, and by 1993 transgenic plants had been produced in all major crop species, including the cereals and the legumes. These remarkable achieve ments have resulted in the production of crops that are resistant to potent but environmentally safe herbicides, or to viral pathogens and insect pests. In other instances genes have been introduced that delay fruit ripening, or increase starch content, or cause male sterility. Most of these manipulations are based on the introduction of a single gene - generally of bacterial origi- that regulates an important monogenic trait, into the crop of choice. Many of the engineered crops are now under field trials and are expected to be commercially produced within the next few years. The early successes in plant biotechnology led to the realization that further molecular improvement of plants will require a thorough understanding of the molecular basis of plant development, and the identification and charac terization of genes that regulate agronomically important multi genic traits.