Contributing Authors. Preface. 1. Introduction E. Pacini, S.W. Nicolson. 1.1 Evolutionary origins. 1.2 Secretions analogous to nectar. 1.3 Floral and extrafloral nectarines. 1.4 Nectar components. 1.5 Organization of this volume. 2. A Systematic Survey of Floral Nectaries G. Bernardello. 2.1 Introduction. 2.2 Nectaries in gymnosperms. 2.3 Nectaries in angiosperms. 2.3.1 Diversity. 2.3.1.1 Nectar presentation. 2.3.1.2 Structure. 2.3.1.3 Fate. 2.3.1.4 Symmetry. 2.3.1.5 Number. 2.3.1.6 Colour. 2.3.2 Factors influencing nectary diversity. 2.3.3 Basic types of floral nectarines. 2.3.4 Nectariferous spurs. 2.3.5 Patterns of variability in nectarines. 2.3.5.1 Asteraceae. 2.3.5.2 Brassicaceae. 2.3.5.3 Cucurbitaceae. 2.3.5.4 Euphorbiaceae. 2.3.5.5 Ranunculaceae. 2.3.5.6 Solanaceae. 2.3.6 Nectaries and deceit pollination. 2.3.6.1 Apocynaceae. 2.3.6.2 Bignoniaceae. 2.3.6.3 Orchidaceae. 2.3.7 Relictual nectarines in anemophilous species. 2.3.8 Distribution of nectary types. 2.3.8.1 Early-branching lineages. 2.3.8.2 Magnoliids. 2.3.8.3 Early-branching monocots. 2.3.8.4 Monocots. 2.3.8.5 Commelinids. 2.3.8.6 Ceratophyllales. 2.3.8.7 Eudicots. 2.3.8.8 Core Eudicots. 2.3.8.9 Rosids. 2.3.8.10 Eurosids I. 2.3.8.11 Eurosids II. 2.3.8.12 Asterids. 2.3.8.13 Euasterids I. 2.3.8.14 Euasterids II. 2.3.9 Evolutionary trends. 3. Nectary Structure and Ultrastructure M. Nepi. 3.1 Introduction. 3.2 Nectary structure and ultrastructure. 3.2.1 Epidermis. 3.2.1.1 Secretory trichomes. 3.2.1.2 Nectary-modified stomata. 3.2.2 Nectary parenchyma. 3.2.2.1 Patterns of plastid development in nectary parenchyma cells. 3.2.3 Subnectary parenchyma. 3.2.4 Nectary vasculature. 3.3 Gynopleural (septal) nectarines. 3.4 Extrafloral nectarines. 3.5 Nectary histochemistry. 4. Nectar Production and Presentation E. Pacini, M. Nepi. 4.1 Introduction. 4.2 Nectar secretion mechanism and models of nectary function. 4.3 Dynamics of nectar components. 4.3.1 Nectar reabsortion: resource recovery and homeostasis. 4.3.2 Nectar standing crop. 4.4 The source of nectar components. 4.5 Ecophysiological significance of parenchyma plastids. 4.6 Nectar presentation. 4.6.1 Floral nectarines. 4.6.2 Extrafloral nectarines. 4.7 Fate of nectar and nectarines. 4.8 Variability of nectar characteristics. 4.8.1 Environmental variables. 4.8.2 Intraspecies variability. 4.8.3 Interpopulation differences. 4.8.4 Variability and experimental design. 5. Nectar Chemistry S.W. Nicolson, R.W. Thornburg. 5.1 Introduction. 5.2 Water. 5.2.1 Nectar concentration. 5.2.2 Chemical and microclimatic influences on nectar concentration. 5.2.3 Viscosity and feeding rates. 5.3 Sugars. 5.3.1 Constancy of sugar composition within species. 5.3.2 The use of sugar ratios can be misleading. 5.3.3 Is sugar composition determined by floral visitors or common ancestry? 5.4 Inorganic ions. 5.5 Amino acids. 5.5.1 Non-protein amino acids. 5.5.2 Nectar amino acids are under the control of environmental factors. 5.5.3 Contribution of amino acids to the taste of nectar. 5.6 Proteins. 5.6.1 Proteins in leek nectar. 5.6.2 Nectar redox cycle. 5.7 Other nectar constituents. 5.7.1 Lipids. 5.7.2 Organic acids. 5.7.3 Phenolics. 5.7.4 Alkaloids. 5.7.5 Terpenoids. 5.8 Conclusion. 6. Molecular Biology of the Nicotiana Floral Nectary R.W. Thornburg. 6.1 Introduction. 6.2 The ornamental tobacco nectary. 6.3 Developmental processes. 6.3.1 Origin of the floral nectary. 6.3.2 Conversion of chloroplasts into chromoplasts. 6.3.3 Filling of the nectary. 6.4 Protection of the gynoecium. 6.5 Gene expression. 6.5.1 Macroarray analysis indentifies defence genes. 6.5.1.1 Role of hydrogen peroxide in plant stress and defence. 6.5.1.2 Role of ascorbate in plant stress and defence. 6.5.2 EST analysis. 6.5.3 Nectary-specific gene expression. 6.6 Nectary molecular biology in other species. 6.6.1 Other n