Nitrogen is an essential element for plant growth. During the green revolution nitrogenfertilisation was responsible for spectacular yield increases. At present yield is balanced with commitments towards the environment and sustainable agriculture. For agro-biotechnology comprehensive knowledge of plant functioning is needed. Yield improvement and accumulation of essential nitrogen compounds is relying on selection and gene technologies.

Research on the uptake, acquisition and assimilation of nitrogen, as well as the synthesis and storage of reserve and defence N-compounds, therefore, is essential. The third volume in the Plant Ecophysiology series integrates functional and molecular physiology with ecophysiological and sustainable agricultural approaches to get a better understanding of the regulation and the impact of environmental and stress signals on nitrogen acquisition and assimilation. The book is of interest for advanced students and junior researchers and supplies comprehensive information for scientists working in the field of nitrogen metabolism and readers interested in sustainable development.

As drought tolerance is a multidirnensional stress, drought tolerance study is a multidisciplinary adventure. In 1992, the network INTERDROUGHT was created with the objective of joining the scientists of the different fields of research involved in drought tolerance study. The network was funded by the EEC and gathered 25 European teams specialized in molecular biology, physiology and geneties. 1\vo workshops were successively organized in 1993 in Sitges (Spain) and in 1994 in Ischia (Italy). After those two European workshops, the necessity of opening the network to the whole scientific community was already clear, and in 1995 the first INTERDROUGHT international conference was held in Montpellier (France). During this meeting, eleven speakers were invited to present a review in their field of research, in a way accessible to all researchers and students, especially those who are not familiar wlth one of the three fields of interest. These eleven reviews are presented in this book. From these reviews three major difficulties arose for drought tolerance irnprovement: - the definition of the drought stress that plants experience; -the differentiation between non adaptive and adaptive response to drought stress; -the identification of the adaptive responses that improved drought yield without decreasing significantly the potential yield. The use of integrated strategies of research will certainly provide irnportant results, such as the recent data obtained on molecular and physiologieal analysis of Arabidopsis mutants.

The beginnings of human civili zation can be traced back to the time , ne- ly 12 ,000 years ago , when th e early humans gradually ch anged from a life of hunting and gathering food , to producing food. This beginning of pri- tive agriculture ensured a dependable supply of food , and fostered the living together of people in groups and the development of s o c i e ty. During th is time, plant s e e ds were recognized a s a valuable s o ur c e of food and nutrition , and began to be used for growing plants for food. Ever s i n c e , plant seeds have played an important role in the development of the human civilization . Even today, s e e ds of a few crop s p e c i e s , s uc h as the cereals and legume s, are the primary s o u r c e of most human food , and the predominant commodity in international agriculture. Owing to their great importance as food for human s and in international trade , seeds have been a favorite object of s t u d y by developmental biologists and physiologi sts , nutritionist s and chem i sts . A wealth of useful information i s available on th e biology of seed s .

Increased atmospheric nitrogen deposition and changes in the management of heathlands have caused a significant change in the species composition of the NW-European heathlands. This change from ericaceous towards gramineous dominance is analysed in detail in Heathlands: Patterns and Processes in a Changing Environment. Special emphasis is put on the effects of increased atmospheric nutrient input on nutrient cycling, competition between plant species and plant--herbivore interactions. The possibilities for the long-term conservation of heathlands are discussed by considering regeneration from seed and the usefulness of mathematical management models. The book provides a synthesis of pure and applied plant ecology. It is vital reading for plant ecologists, biological conservationists, heathland managers and government decision makers.

Wheat breeders have achieved significant results over the last fifty years in research on mankind's one of the most important crops. Classical genetic and breeding methods, far broader international cooperation than was experienced in earlier periods, and improvements in agronomic techniques have led to previously unimaginable development in the utilisation of wheat for human consumption. The contribution of wheat researchers is particularly noteworthy since these results have been achieved at a time when the world population has grown extremely dynamically. Despite this demographic explosion, of a proportion never previously experienced, thousands of millions of people have been saved from starvation, thus avoiding unpredictable social consequences and situations irreconcilable with human dignity. Despite these developments in many regions of the world food supplies are still uncertain and the increase in the world's wheat production has not kept pace with the population increase during the last decade. Due to the evils of civilisation and the pollution of the environment there is a constant decline in the per capita area of land suitable for agricultural production. Based on population estimates for 2030, the present wheat yield of around 600 million tonnes will have to be increased to almost 1000 million tonnes if food supplies are to be maintained at the present level.

Studies on molecular biology of pathogens, infection process and disease resistance, have provided information essentially required to understand the vulnerable stages at which the pathogens can be tackled effectively and to adopt novel strategies to incorporate disease resistance genes from diverse sources and /or to induce resistance of cultivars with desirable agronomic attributes using biotic or abiotic agents. The nature of interaction between the gene products of the pathogen and plant appears to determine the outcome of the interaction resulting in either disease progression or suppression. Transgenic plants with engineered genes show promise for effective exploitation of this approach for practical application. Research efforts during the recent years to sequence the whole genomes of the pathogens and plants may lead to development of better ways of manipulating disease resistance mechanisms enabling the grower to achieve higher production levels and the consumer to enjoy safer food and agricultural products. Experimental protocols included in appropriate chapters will be useful for researchers and graduate students.

The assimilation of sulfur in higher plants and its reduction in metabolically important sulfur compounds are crucial factors determining plant growth and vigor and resistance to stresses. The present book discusses the aspects of sustainable crop production with sulfur, the importance of sulfur metabolites and sulfur metabolizing enzymes in abiotic stress management in plants. The book provides the most up-to-date reference on sulfur assimilation in plants.

Phytohormones are very much involved in directing the plant growth, in a coordinated fashion in association with metabolism that provides energy and the building blocks to develop the form that we recognize as plant. Out of the recognized hormones, attention has largely been focused on Auxins, Gibberellins, Cytokinins, Abscisic acid, Ethylene and more recently to Brassinosteroids. However, in this book we are providing the information about a natural chemical, Salicylic Acid, that could be raised to the status of the above phytohormones because it has significant impact on various aspects of the plant life.

Salicylic acid (SA) was first discovered as a major component in the extracts from Salix (willow) whose bark from ancient time, was used as an anti-inflammatory drug. This acid (SA) is a phenol, ubiquitous in plants generating a significant impact on plant growth and development, photosynthesis, transpiration, ion uptake and transport and also induces specific changes in leaf anatomy and chloroplast structure. SA is recognized as an endogenous signal, mediating in plant defence, against pathogens.

This book includes contributions made by various experts, spread over the world. Since the work on Salicylic Acid is currently rather scattered it was thought prudent to draw this all together in one volume. This will naturally facilitate a ready reference of the material to students and researchers, alike.

The adv antages of those systems are counterbalanced by some important dis- vantages. For one, in heterotrophic and mixotrophic systems high concentrations of organic ingredients are required in the nutrient medium (particularly sugar at 2% or more), associated with a high risk of microbial contamination. How, and to which extent this can be avoided will be dealt with in Chapter 3. Other disadvantages are the difficulties and limitations of extrapolating results based on tissue or cell c- tures, to interpreting phenomena occurring in an intact plant during its development. It has always to be kept in mind that tissue cultures are only model systems, with all positive and negative characteristics inherent of such experimental setups. To be realistic, a direct duplication of in situ conditions in tissue culture systems is still not possible even today in the 21st century, and probably never will be. The organization of the genetic system and of basic cell structures is, however, essentially the same, and therefore tissue cultures of higher plants should be better suited as model s- tems than, e.g., cultures of algae, often employed as model systems in physiological or biochemical investigations. The domain cell and tissue culture is rather broad, and necessarily unspecif ic. In terms of practical aspects, basically five areas can be distinguished (see Figs. 1.1, 1.2 ), which here shall be briefly surveyed before being discussed later at length.

The importance of haploids is well known to geneticists and plant breeders. The discovery of anther-derived haploid Datura plants in 1964 initiated great excitement in the plant breeding and genetics communities as it offered shortcuts in producing highly desirable homozygous plants. Unfortunately, the expected revolution was slow to materialise due to problems in extending methods to other species, including genotypic dependence, recalcitrance, slow development of tissue culture technologies and a lack of knowledge of the underlying processes. Recent years have witnessed great strides in the research and application of haploids in higher plants. After a lull in activities, drivers for the resurgence have been: (1) development of effective tissue culture protocols, (2) identification of genes c- trolling embryogenesis, and (3) large scale and wide spread commercial up-take in plant breeding and plant biotechnology arenas. The first major international symposium on "Haploids in Higher Plants" took place in Guelph, Canada in 1974. At that time there was much excitement about the potential benefits, but in his opening address Sir Ralph Riley offered the following words of caution: "I believe that it is quite likely that haploid research will contr- ute cultivars to agriculture in several crops in the future. However, the more extreme claims of the enthusiasts for haploid breeding must be treated with proper caution. Plant breeding is subject from time to time to sweeping claims from ent- siastic proponents of new procedures.

Recent years have brought an upsurge of interest in the study of arbuscular mycorrhizal (AM) fungi, partly due to the realization that the effective utilization of these symbiotic soil fungi is likely to be essential in sustainable agriculture. Impressive progress has been made during the last decade in the study of this symbiosis largely as a result of increasing exploitation of molecular tools. Although early emphasis was placed on the use of molecular tools to study physiological processes triggered by the symbiosis, such as expression of symbiosis-specific polypeptides and modulation of host defences, other applications await. It was obvious to us that gathering leaders in the field to summarize these topics and point out research needs was necessary if we were to understand the physiology and function of AM fungi at a molecular level. In addition, we have taken the opportunity to present these reviews in a logical sequence of topics ranging from the initiation of the life cycle of the fungus to its functions in plant growth and in the below ground ecosystem. It was a challenge to limit this flood of information to the confines of one text. This is a very exciting time for mycorrhiza biologists and it is our hope that some of this excitement is conveyed to our readers.

There are many good books in the market dealing with the subject of allelopathy. When we designed the outline of this new book, we thought that it should include as many different points of view as possible, although in an integrated general scheme. Allelopathy can be viewed from different of perspectives, ranging from the molecular to the ecosystem level, and including molecular biology, plant biochemistry, plant physiology, plant ecophysiology and ecology, with information coming also from the organic chemistry, soil sciences, microbiology and many other scientific disciplines. This book was designed to include a complete perspective of allelopathic process. The book is divided into seven major sections. The first chapter explores the international development of allelopathy as a science and next section deals with methodological aspects and it explores potential limitations of actual research. Third section is devoted to physiological aspects of allelopathy. Different specialists wrote about photosynthesis, cell cycle, detoxification processes, abiotic and biotic stress, plant secondary metabolites and respiration related to allelopathy. Chapters 13 through 16 are collectively devoted to various aspects of plant ecophysiology on a variety of levels: microorganisms, soil system and weed germination. Fundamental ecology approaches using both experimental observations and theoretical analysis of allelopathy are described in chapters 16 and 17. Those chapters deal with the possible evolutionary forces that have shaped particular strategies. In the section named "allelopathy in different environments", authors primarily center on marine, aquatic, forest and agro ecosystems. Last section includes chapters addressing application of the knowledge of allelopathy.

Flowering plants dominate much of the Earth's surface and yet, as sessile organisms, they must constantly resist attack by numerous voracious herbivores. Survival in the face of an abundance of insect predators relies on sophisticated resistance systems allowing plants to escape from herbivory in time or in space, to confront herbivores directly, or to fight them indirectly by remarkable collaborations with other species. Until recently, plant resistance was believed to be constitutive, i.e. ever-present and independent from herbivore attack. However, plants were discovered to respond actively to herbivory through the mobilization of specific defenses, and this discovery opened an exciting new field of research.
This book provides a thorough overview of the anatomical, chemical, and developmental features contributing to plant defense, with particular emphasis on plant responses that are induced by wounding or herbivore attack.

Adaptation and evolution of terrestrial plants depend, to a large extent, on their ability to acquire nutrients. This is a modern and integrative treatment of the mechanisms controlling plant nutrient uptake and how plants respond to changes in the environment. The following key topics are covered: soil nutrient bioavailability; root responses to variations in nutrient supply; nitrogen fixation; regulation of nutrient uptake by internal plant demand; root characteristics; kinetics of nutrient uptake; root architecture; life span; mycorrhizae; responses to climate change. This integrated view helps us to understand the mechanisms that govern present-day plant communities and is indispensable in models designed to predict the response of plants to a changing climate.

Investigations on various aspects of plant-pathogen interactions have the ultimate aim of providing information that may be useful for the development of effective crop disease management systems. Molecular techniques have accelerated the formulation of short- and long-term strategies of disease management. Exclusion and eradication of plant pathogens by rapid and precise detection and identification of microbial pathogens in symptomatic and asymptomatic plants and planting materials by employing molecular methods has been practiced extensively by quarantines and certification programs with a decisive advantage. Identification of sources of resistance genes, cloning and characterization of desired resistance genes and incorporation of resistance gene(s) into cultivars and transformation of plants with selected gene(s) have been successfully performed by applying appropriate molecular techniques. Induction of resistance in susceptible cultivars by using biotic and abiotic inducers of resistance is a practical proposition for several crops whose resistance levels could not be improved by breeding or transformation procedures. The risks of emergence of pathogen strains less sensitive or resistant to chemicals have been reduced appreciably by rapid identification of resistant strains and monitoring the occurrence of such strains in different geographical locations.

Salinity and water stress limit crop productivity worldwide and generate substantial economic losses each year, yet innovative research on crop and natural resource management can reveal cost-effective ways in which farmers can increase both their productivity and their income.

Presenting recent research findings on salt stress, water stress and stress-adapted plants, this book offers insights into new strategies for increasing the efficiency of crops under stressful environments. The strategies are based on conventional breeding and advanced molecular techniques used by plant physiologists, and are discussed using specific case studies to illustrate their potential. The book emphasizes the effects of environmental factors on specific stages of plant development, and discusses the role of plant growth regulators, nutrients, osmoprotectants and antioxidants in counteracting their adverse affects.

Synthesising updated information on mechansisms of stress tolerance at cell, tissue and whole-plant level, this book provides a useful reference text for post graduate students and researchers involved in the fields of stress physiology and plant physiology in general, with additional readership amongst researchers in horticulture, agronomy, crop science, conservation, environmental management and ecological restoration.

The plant' is often the most neglected part of plant-based medicine. Throughout time, humans have searched, collected, and effectively used plants for healing. Currently, the medicinal plant-based business is flourishing at a dramatic pace and at the expense of an already declining population of plant species, many of which are on the verge of extinction. In spite of this history and popularity, the mystery of what transforms a plant into a medicinal plant persists, and there are chronic problems with ensuring the safety and efficacy of medicinal plant products. Therefore, there is a real need for a full characterization of medicinal plant species and for the development and application of novel technologies for the production of plant-based medicines. This book highlights some of the recent advances and new approaches to the development of technologies for plant-based medicines and is intended to stimulate new discussions among researchers, regulatory authorities, and pharmaceutical organizations, leading to significant advancements in the field.

The 12th International Symposium on Plant Lipids was held at the University of Toronto, Canada, from July 7th to 12th, 1996. The conference was attended by over 200 scientists from university, government and corporate laboratories from 24 different countries. The topics covered in the symposium ranged from basic physiology, biochemistry and molecular biology of plant lipids to transformation and genetic engineering of crop plants. Oil seed plants were a particular focus of the symposium. There were 62 oral and 96 posters presentations. A special lecture in memory of the founder of this series of symposium, Terry Galliard, was presented by John Shanklin. This Proceedings Book has been dedicated to Grattan Roughan for his important contributions to our knowledge of plant lipid metabolism. This volume contains manuscripts submitted from most of the presentations at the symposium. It provides a useful summary of the major fields of plant lipid studies and our present state of knowledge. The papers are arranged in eight sections covering the major areas in the field of plant physiology, biochemistry and molecular biology of plant lipids. We would like to thank Valerie Imperial, Rajesh Khetarpal and Mary Williams for their invaluable help in organizing and running the meetings and excursions. John P. Williams, Mobashsher U. Khan and Nora W. Lem Toronto, Canada, October 1996 xvii DEDICATION This volume is dedicated to Grattan Roughan.

The Handbook of Plant Ecophysiology Techniques you have now in your hands is the result of several combined events and efforts. The birth of this handbook can be traced as far as 1997, when our Plant Ecophysiology lab at the University of Vigo hosted a practical course on Plant Ecophysiology Techniques. That course showed us how much useful a handbook presenting a bunch of techniques would be for the scientists beginning to work on Plant Ecophysiology. In fact, we wrote a short handbook explaining the basics of the techniques taught in that 1997 course: Flow cytometry to measure ploidy levels, Use of a Steady-State porometer to measure transpiration, In vivo measure of fluorescence, HPLC analysis of low molecular weight phenolics, Spectrophotometric determinations of free proline and soluble proteins, TLC polyamines contents measures, Isoenzymatic electrophoresis, Use of IRGA and oxygen electrode. That modest handbook, written in Spanish, was very helpful, both for the people who attended the course and for other who have used it for beginning to work in Plant Ecophysiology. The present Handbook is much more ambitious, and it includes more techniques. But we have also had in mind the young scientists beginning to work on Plant Ecophysiology. In 1999 Francois Pellissier leaded a proposal presented to the European Commission in the Fifth Framework Program in the High Level * Scientific Conferences, including three EuroLab Courses about lab and field techniques useful to improve allelopathic research."

With one volume published each year, this series keeps scientists and students current with the latest developments and results in all areas of the plant sciences. This present volume includes insightful reviews covering genetics, cell biology, physiology, comparative morphology, systematics, ecology, and vegetation science.

Oxidation-reduction (i.e. redox) processes at the plasma membrane of any cell have been attracting more and more attention, both in basic and in applied research, since the first workshop dealing with the plasma membrane oxidoreductases was organized in Cordoba, Spain, in 1988. This evolution is evident considering the numerous cell functions performed by plasma membrane redox systems not only in healthy cells but also in cells that escaped from the normal metabolic control (e.g. cancer cells) and cells under attack by pathogens. Plasma membrane redox processes have now been demonstrated to play an essential role in growth control and defense mechanisms of these cells. The great importance of the plasma membrane redox systems originates in the fact that they are located in the membrane which is essentially the site of communication between the living cell and its environment. We may say that the plasma membrane can be considered as the "sensory part" of the cell. No chemical substance can enter the cell interior without interaction with the plasma membrane.

Plant secondary metabolism is an economically important source of fine chemicals, such as drugs, insecticides, dyes, flavours, and fragrances. Moreover, important traits of plants such as taste, flavour, smell, colour, or resistance against pests and diseases are also related to secondary metabolites. The genetic modification of plants is feasible nowadays. What does the possibility of engineering plant secondary metabolite pathways mean? In this book, firstly a general introduction is given on plant secondary metabolism, followed by an overview of the possible approaches that could be used to alter secondary metabolite pathways. In a series of chapters from various authorities in the field, an overview is given of the state of the art for important groups of secondary metabolites. No books have been published on this topic so far. This book will thus be a unique source of information for all those involved with plants as chemical factories of fine chemicals and those involved with the quality of food and ornamental plants. It will be useful in teaching graduate courses in the field of metabolic engineering in plants.

In the two decades since the last comprehensive work on plant peroxisomes appeared, the scientific approaches employed in the study of plant biology have changed beyond all recognition. The accelerating pace of plant research in the post-genomic era is leading us to appreciate that peroxisomes have many important roles in plant cells, including reserve mobilisation, nitrogen assimilation, defence against stress, and metabolism of plant hormones, which are vital for productivity and normal plant development. Many plant scientists are finding, and will no doubt continue to find, that their own area of research is connected in some way to peroxisomes.

Written by the leading experts in the field, this book surveys peroxisomal metabolic pathways, protein targeting and biogenesis of the organelle and prospects for the manipulation of peroxisomal function for biotechnological purposes. It aims to draw together the current state of the art as a convenient starting point for anyone, student or researcher, who wishes to know about plant peroxisomes.

The aim of this book is to give an overview of the most important aspects of physiological and biochemical basis for metal toxicity and tolerance in plants. The book is expected to serve as a reference to university and college teachers, students of plant sciences, environmental biology, environmental biotechnology, agriculture, horticulture, forestry, plant molecular biology, and genetics.

The plant hormone ethylene plays a prominent role among several intrinsic and extrinsic factors that control growth and physiology of plants. Its biological activity was discovered over a century ago. However, extensive studies on its mode of action came later. This book brings into focus the recent developments on the biochemical, physiological, and molecular basis for ethylene action in plants.