Until recently the interest of plant physiologists in the structure and function of the root, as compared with the above-ground organs, was rather limited. In contrast to the data obtained from agricultural research, where the root is understood as an organ of water and nutrient uptake, recent studies on root systems have evolved as a consequence of an increase in our general knowledge of the transport of substances across biological cell membranes. This has led to increased interest in studies of ion uptake and transport from a novel viewpoint. Parallel to this, the complexity of the histological structure of the root has necessitated a study of this structure in relation to processes which take place in the root. The evaluation of such complex relationships is, in this book, concentrated on recent findings concerning the anatomical structure of the root in relation to its functional manifestations. Based on the principles of structure and function, the metabolic processes in the root, as well as the uptake and transport of water and ions are dealt with. The emphasis throughout is on the structural features. Finally, a short chapter has been included about the root under conditions of environmental stress.

The plasma membrane is at once the window through which the cell senses the environment and the portal through which the environment influences the structure and activities of the cell. Its importance in cellular physiology can thus hardly be overestimated, since constant flow of materials between cell and environment is essential to the well-being of any biological system. The nature of the materials mov ing into the cell is also critical, since some substances are required for maintenance and growth, while others, because of their toxicity, must either be rigorously excluded or permitted to enter only after chemical alteration. Such alteration frequently permits the compounds to be sequestered in special cellular compartments having different types of membranes. This type of homogeneity, plus the fact that the wear and tear of transmembrane molecular traffic compels the system to be constantly monitored and repaired, means that the membrane system of any organism must be both structurally complex and dy namic. Membranes have been traditionally difficult to study because of their fragility and small diameter. In the last several decades, however, remarkable advances have been made because of techniques permit ting the bulk isolation of membranes from homogenized cells. From such isolated membranes have come detailed physical and chemical analyses that have given us a detailed working model of membrane. We now can make intelligent guesses about the structural and func tional interactions of membrane lipids, phospholipids, proteins, sterols and water.

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."

The application of molecular techniques is rapidly transforming the study of plant systematics. The precision they offer enables researchers to classify plants that have not been subject to rigorous classification before and thus allows them to obtain a clearer picture of evolutionary relationships. Plant Molecular Systematics is arranged both conceptually and phylogenetically to accommodate the interests not only of general systematists, but also those of people interested in a particular plant family. The first part discusses molecular sequencing; the second reviews restriction site analysis and the sequencing of mitochondrial DNA. A third section details the analysis of ribosomal DNA and chloroplast DNA. The following section introduces model studies involving well-studied families such as the Onagraceae, Compositae and Leguminosae. The book concludes with a section addressing theoretical topics such as data analysis and the question of morphological vs. molecular data.

The beauty of a knotty oak tree is different from that of a lovely flower. It is the rough beauty of an old soldier's face showing the traces of wind and sun, of harm and of victory, bearing the scars of bygone battles. It is different from the fragile, delicate beauty of a young girl which is evident to anyone at first sight. The beauty of an old and crippled tree is hidden unless perceived by the alert eye which is able to fancy or rather discern the hard trials of life the tree has ex perienced. Contemplating trees in this way is not much different from busying oneself with physiognomies, i.e. with the art of judging character from the features of the human face. Physiognomies is often considered a dubious science, but is prac ticed every day in human communication by everybody from early childhood to old age. Although we all are able to discern the angrily furrowed brow, the laughing crow's-feet below the eyes, the arrogant harsh lines around the nose, the hard narrow mouth, the gluttonous lip, and the secret eye of the silent ob server, we would never admit to rely on such seemingly doubtful methods."

In the preface to the first edition ofthis book, we expressed a conviction that there was a need for a short book that highlighted important advances in the new discipline of plant molecular biology. The rapid development of this topic has been brought about by the recognition of the unique properties of plants in the study of growth and development together with the application of recombinant DNA techniques to tackle these problems. Plant cells contain DNA in nuclei, plastids and mitochondria, and so ofTer the unique challenge of studying the interaction of three separate genetic systems in a single organism. The molecular approach has provided, in recent years, a wealth of important information about how plants function, and how they interact with bacteria, fungi and viruses. Furthermore, plant development involves the regulation of gene expression in response to internal and external signals, and plant molecular biology has provided a fundamental insight into how this development is regulated. This is not only of considerable scientific interest, but also has important implications for the production of plants and plant products in agriculture, horticulture and the food industries.

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.

This book presents edited and revised papers from the seventh International Workshop on Seeds, held in Salamanca, Spain, in May 2002. The key topics addressed include seed development, germination and dormancy, as well as desiccation, seed ecology and seed biotechnology.

This supplement, containing six chapters, is the first in a series of important works designed to be integrated into the text of the Plant Tissue Culture Manual to maintain it as a valuable source of laboratory methodology

Plant cell and tissue culture comprises a broad range of techniques of great value to research workers in the fields of cell and molecular biology, physiology, biochemistry, plant breeding and propagation and genetic engineering. This manual provides protocols for the major techniques in such a format that they can be followed step-by-step at the bench. Both applied and more fundamental uses of cell, tissue and organ culture are covered, and the ring-binder design allows the manual to be updated regularly with supplementary chapters. Each chapter, discussing a single technique or protocol, provides background information, references to the relevant literature and a guide to troubleshooting in addition to a thorough methodology. This second Supplement to the core text of the "Manual" provides important techniques to be added to the Sections on "Basic Techniques, Tissue Culture & Transformation of Crop Species and Reproductive Tissues".

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."

For the past twenty years I have worked as an applied plant virologist, attempting to identify and control virus diseases in field crops. During the last ten years it has been my privilege to present short courses in plant virology to final-year students studying plant pathology, micro biology and general botany. Throughout the period I have been lecturing, it has been possible to recommend several excellent 'library' books for further reading in plant virology, but there has been no publication covering applied plant virology that a student might consider purchasing. With teaching requirements in mind this book has been written to provide a concise introduction to applied plant virology based on the experiences I have gained working on virus diseases, both in an applied laboratory and in the field. The text concentrates on introducing the reader to aspects of plant virology that would be encountered every day by an applied virologist trying to identify viruses and develop control measures for virus diseases of crop plants. Although a brief introduction to virus structure and its terminology is given in the opening chapter of the book, no attempt is made to cover in detail the more fundamental aspects of virus structure, biochemistry and replication. Similarly, the symptoms caused by individual viruses are not described, although the various types of symptoms that plant viruses cause and which might be encountered by a student or research worker are described."

capable of providing at least a relative measure of stomatal aperture were first used shortly thereafter (Darwin and Pertz, 1911). The Carnegie Institution of Washington's Desert Research Laboratory in Tucson from 1905 to 1927 was the first effort by plant physiologists and ecologists to conduct team research on the water relations of desert plants. Measurements by Stocker in the North African deserts and Indonesia (Stocker, 1928, 1935) and by Lundegardh (1922) in forest understories were pioneering attempts to understand the environmental controls on photosynthesis in the field. While these early physiological ecologists were keen observers and often posed hypotheses still relevant today they were strongly limited by the methods and technologies available to them. Their measurements provided only rough approximations of the actual plant responses. The available laboratory equip ment was either unsuited or much more difficult to operate under field than laboratory conditions. Laboratory physiologists distrusted the results and ecologists were largely not persuaded of its relevance. Consequently, it was not until the 1950s and 1960s that physiological ecology began its current resurgence. While the reasons for this are complicated, the development and application of more sophisticated instruments such as the infrared gas analyzer played a major role. In addition, the development of micrometeorology led to new methods of characterizing the plant environments."

Genetic erosions in plant cell cultures, especially in chromosome number and ploidy level, have now been known for over 25 years. Until the mid -1970ssuch changes were consideredundesirable and thereforediscarded because the main emphasis wason clonal propagation and genetic stability of cultures. However, since the publication on somaclonal variation by Larkin and Scowcroft (1981) there has been a renewed interest to utilize these in vitro obtained variations for crop improvement. Studies conduc- ted during the last decade have shown that callus cultures, especially on peridical subculturing over an extended period of time, undergo morpho- logical and genetic changes, i. e. polyploidy, aneuploidy, chromosome breakage, deletions, translocations, gene amplification, inversions, muta- tions, etc. In addition, there are changes at the molecular and biochemical levelsincluding changes in the DNA, enzymes,proteins, etc. Suchchanges are now intentionally induced, and useful variants are selected. For instance in agricultural crops such as potato, tomato, tobacco, maize, rice and sugarcane, plants showing tolerance to a number of diseases, viruses, herbicides and salinity, have been isolated in cell cultures. Likewise induction of male sterility in rice, and wheat showing various levels of fer- tility and gliadin, have been developed in vitro. These academic excercises open new avenues for plant breeders and pathologists. Another area of tremendous commercial importance in the pharmaceuti- cal industry is the selection of cell lines showing high levels of medicinal and industrial compounds. Already high shikonin containing somaclones in Lithospermum are being used commercially.

The genetic work that has been carried out with volume, and especially in Section V 'Germplasm crop plants indicates that many nutritional charac- resources and creation of genotypes for specific teristics are independently inherited and could be environmental including low input systems', is selected for a breeding program. evident. This can be considered as genuine progress This volume presents the proceedings of the in the direction of an effective use of nutrients by 'Third International Symposium on Genetic plants. Aspects of Plant Mineral Nutrition' held in We look forward to more advances in our un- Braunschweig 1988, and demonstrates the wide derstanding of the mechanisms involved in the acceptance that cultivars respond differently to nutrient efficiency of crop plants and in the nutritional and stress factors. An improved re- development and improvement of screening sponse of cultivars to nutrients and stress con- techniques at the Fourth Symposium to be held in ditions is accessible via screening, selection and Australia in 1991. breeding of the available plant genetic resources and will help to reduce the inputs and to protect the N. EI Bassam environment. M.Dambroth The contribution of the plant breeders in this B. c. Loughman XI N. El Bassam et al. (Eds.), Genetic aspects a/plant mineral nutrition, 1-7. PLSO PN 122 (c) 1990 Kluwer Academic Publishers.

which individuals are heterozygous (H). A review by Selander (1976] comparing these param eters in various populations has been followed by many other studies. In the present volume, J. B. Mitton has used H to evaluate the importance of heterozygosity in natural populations. The degree of polymorphism expressed by P, has been used in several contributions to approach various problems of population genetics. particularly breeding structure and mating systems by Hamrick, Barrett and Shore, Brown, Burdon and Jarosz. as well as Soltis and Soltis, and Wyatt. Stoneburner. and Odrzykoski. New knowledge derived from these investigations has strengthened a point of view already stressed by Darwin: evolution takes place in a complex environment, that can be constantly changing over long periods of time. or can alternate between long periods of relative stability and cycles of rapid change. The most successful plant species become adjusted to these vagaries in several ways, including shifts in heterozygosity. polymorphism and mating systems. The strength of isozyme ana ysis for testing hypotheses is well illustrated by the contribution of the Soltises, who have shown clearly that a previously held hypothesis, predicting self fertilization fortified by polyploid genetic segregations in ferns, must be rejected."

This text explores the means, processes and mechanisms by which plants change the orientation and juxtapositions of various organs in order to optimize their harvest of energy, and examines the major stumuli which provokes such responses. These interactions are re-described for higher plants through to ferns, fungi and algae, and the text constantly emphasizes the functional significance of particular growth movements to plants in their natural surroundings. This book should be of interest to research students and lecturers in plant physiology; research workers in agriculture and plant biochemistry.

This handbook is intended as an introductory guide to students at all levels on the principles and practice of plant growth analysis. Many have found this quantitative approach to be useful in the description and interpretation of the performance of whole plant systems grown under natural, semi-natural or controlled conditions. Most of the methods described require only simple experimental data and facilities. For the classical approach, GCSE biology and mathematics (or their equivalents) are the only theoretical backgrounds required. For the functional approach, a little calculus and statistical theory is needed. All of the topics regarding the quantitative basis of productivity recently introduced to the Biology A-level syllabus by the Joint Matriculation Board are covered. The booklet replaces my elementary Plant Growth Analysis (1978, London: Edward Arnold) which is now out of print. The presentation is very basic indeed; the opening pages give only essential outlines of the main issues. They are followed by brief, standardized accounts of each growth-analytical concept taken in turn. The illustrations deal more with the properties of well-grown material than with the effects of specific environmental changes, even though that is where much of the subject's interest lies. However, detailed references to the relevant parts of more com prehensive works appear throughout, and a later section on 'Inter relations' adds perspective. Some 'Questions and answers' may also help to show what topics will arise if the subject is pursued further."

Every year between three and four hundred papers are published on the topic of insulin action. This extraordinary publication rate prevents any author from includ ing an exhaustive bibliography in any review or book. Perhaps due to this there is no single text that attempts to cover the effects and the mechanism of action of insulin. This book is such an attempt. I intend to present a review of the physiological effects of insulin, the pathology of defects in the action of insulin, and the current views on the mechanism of action of this hormone. I make no apology for the fact that the bibliography will not be extensive and that the amount of experimental detail and data discussed will be kept to a relevant minimum. This book is not intended for the expert in the field, but for the second- or third-year undergraduate and graduate student of medicine, biochemistry, physiology or related disciplines, and will be valuable as a reference source for research workers. The book is presented as a guide, a summary of the ideas and facts; it will present a reader with a foretaste of a fascinating and ever-changing field. I have attempted to be up-to-date with published research work. Any significant contributions to the field not included in the first draft have been added as footnotes. I assume a basic knowledge of the metabolic pathways of carbohydrates, fats and proteins."

Even though most of the biomass of the planet is in forests, we live in a world where wood as a raw material and its products are increasingly scarce. This is particularly so in important areas such as the European Community, which is far from self-sufficient in terms of wood. In recent years the need to intensify forest production and, in some cases, to uti lize abandoned agricultural land for forestry has focussed world-wide attention on the economic importance of fast-growing tree plantations. These are usually managed as short "rotations" (growing cycles) of less than 15 years, often for the production of industrial raw materials or biomass for energy. Under the designation of fast-growing tree plantations, or short rotation silviculture, one may find ecosystems managed for different economic objectives, with different intensities of technical intervention and different levels of productivity. They may include any of a wide range of species grown under various environmental conditions. A common factor, however, is the greater possibility that exists, relative to conventional forestry, for manipulation of both the environment and the genetics of the trees."

This book provides an excellent illustration of the interrelationship between progress in scientific methodology and conceptual advances, and its publica tion should contribute to further advances. It is well known that major advances in understanding often follow the development of new methods. The development of the acetylene reduction assay for nitrogenase activity provides a good example of this interrelationship between theory and methods. Theoretical knowledge led to a search for substrates for nitro genase that could be assayed for more easily than ammonium, the normal product of the enzyme. The discovery of the reduction of acetylene to ethylene by nitrogenase provided the ideal answer to the problem by provid ing a rapid, specific, nondestructive, and inexpensive assay for nitrogenase activity. This assay is now used by almost every laboratory doing research on nitrogen fixation. However, further use and development of the acetylene reduction assay has shown that it can underestimate nitrogenase activity and can even give incorrect relative values under some circumstances. The major problem is that exposure of legume nodules to acetylene can cause a large increase in the resistance to oxygen diffusion into the nodule. This reduced supply of oxygen decreases the rate of nitrogenase activity within a few minutes."

With the demonstration of the "triple response" in plants by Neljubow at the turn of the century, ethylene has been identified as a substance specifically affecting plant growth. Yet it took a few more decades to show that ethylene is a naturally occurring product of plants having all the characteristics of a phytohormone. Ever since much effort has been devoted to a wide variety of physiological and biochemical problems relevant to ethylene. A first meeting was organized in Israel in 1984 to bring together many people active in this rapidly expanding field of experimental research. It is the aim of the present symposium to provide once more a forum at which researchers might expose and comment progress in their work over the last few years. Speakers were invi ted and their contri buti ons ordered ina number of sessions, each of which was centered on a particular topiC. Much of the benefit came from ensuing discussion sessions which were conducted with much competence and expertise by Anderson, Ben-Arie, Goren, Morgan and Osborne. All of these colleagues are recognized leaders in ethylene research today and the organizers owe a very special gratitude to them for their substantial contribution to the programme. It is well to remember the friendly atmosphere, so essential to the success of the whole meeting and so much enjoyed by every partiCipant. Prompt publi ca tion of the papers was made possi ble by the camera-ready procedure offered by the publisher.

Molecular biology, particularly molecular genetics, is among the newest and most powerful approach in modern photosynthesis research. Development of molecular biology techniques has provided new methods to solve old problems in many biological disciplines. Molecular biology has its greatest potential for contribution when applied in combination with other disciplines, to focus not just on genes and molecules, but on the complex interaction between them and the biochemical pathways in the whole organism. Photosynthesis is surely the best studied research area in plant biology, making this field the foremost candidate for successfully employing molecular genetic techniques. Already, the success of molecular biology in photosynthesis has been nothing short of spectacular. Work performed over the last few years, much of which is sum marized in this volume, stands in evidence. Techniques such as site-specific mutagenesis have helped us in examining the roles of individual protein domains in the function of multiunit complexes such as the enzyme ribulose-l,5-bisphos phate carboxylase/oxygenase (RUBISCO) and the oxygen evolving photo system (the photosystem II). The techniques of molecular biology have been very important in advancing the state of knowledge of the reaction center from the photosynthetic bacteria whose structure has been elegantly deduced by H. Michel and 1. Deisenhofer from the X-ray studies of its crystals."

The first edition of The Science of Photobiology was published in 1977, and was the first textbook to cover all of the major areas of photobiology. The science of photobiology is currently divided into 14 subspecialty areas by the American Society for Photobiology. In this edition, however, the topics of phototechnology and spectroscopy have been com bined in a new chapter entitled "Photophysics." The other subspecialty areas remain the same, i.e., Photochemistry, Photosensitization, UV Radiation Effects, Environmental Photobiology, Photomedicine, Circadian Rhythms, Extraretinal Photoreception, Vision, Photomorphogenesis, Photomovement, Photosynthesis, and Bioluminescence. This book has been written as a textbook to introduce the science of photobiology to advanced undergraduate and graduate students. The chapters are written to provide a broad overview of each topic. They are designed to contain the amount of information that might be presented in a one-to two-hour general lecture. The references are not meant to be exhaustive, but key references are included to give students an entry into the literature. Frequently a more recent reference that reviews the literature will be cited rather than the first paper by the author making the original discovery. The chapters are not meant to be a repository of facts for research workers in the field, but rather are concerned with demon strating the importance of each specialty area of photobiology, and documenting its relevance to current and/or future problems of man."