Symmetry and the causes of shifts in different types of symmetries in flowers follow specific patterns that are ruled by developmental and genetic factors. Using a unified system of phyllotaxic equations, we have modeled the molecular mechanisms and pressure forces that act in inflorescence and floral meristems, giving flowers their organ arrangement. In this book, we state general physical principles, whereby the symmetry of the perianth is derived from the symmetry of certain TCP gene expression. Thus, we define the interplay between the expression of CYC2-like genes and the phyllotactic mechanisms. This new evo-devo approach is applied to major groups of angiosperms with predominantly actinomorphic flowers (in which rare zygomorphy is positional) and groups with mainly bilaterally symmetrical flowers (in which zygomorphy is constitutional). It has thus allowed us to revisit the contributions of the great floral morphologists of the 20th and early 21st centuries.

Table of Contents:
Foreword ix Preface xi Acknowledgments xv Introduction xvii Chapter 1. Concepts of Phyllotaxis and the Genetics of Floral Symmetry 1 1.1. Types of floral symmetry 1 1.2. The bracteole theory 3 1.3. Phyllotaxis 5 1.3.1. Phyllotaxis models 5 1.3.2. Fibonacci spirals 9 1.3.3. Whorled phyllotaxis 12 1.3.4. Molecular and contact pressure origin 14 1.4. Genetic control of floral symmetry 17 1.5. Curie’s symmetry principle 22 Chapter 2. Spirals Are Symmetrical Figures 23 2.1. The model 23 2.2. Phyllotaxic spirals are symmetrical figures 25 2.3. Projection of the three-dimensional meristem 28 2.4. Examples of spiral symmetry 30 2.4.1. Plant lattices 30 2.4.2. Disc-stacking in a cylinder 31 2.4.3. Levitov’s energy model 32 2.4.4. The Douady–Couder experiment 33 2.4.5. The magnetic cactus 34 2.4.6. Contact pressure 35 2.5. Phyllotaxis as a dynamical system 36 2.5.1. The dynamics of phyllotaxis 36 2.5.2. Whorled phyllotaxis 38 2.5.3. Fibonacci spiral phyllotaxis 39 2.5.4. Periodic divergence angles 41 2.5.5. Chaotic/quasi-symmetric phyllotaxis 42 2.5.6. Pseudo-whorled phyllotaxis 45 2.5.7. Lucas phyllotaxis 46 2.6. Appendix 50 2.6.1. Appendix 1: the growth index 50 2.6.2. Appendix 2: cylindrical versus centric lattices 51 Chapter 3. Symmetry in Ranunculales 53 3.1. Papaveraceae 54 3.1.1. Papaveroideae 54 3.1.2. Fumarioideae 56 3.2. Menispermaceae 60 3.3. Ranunculaceae 62 Chapter 4. Symmetry in Lamiales 83 4.1. Introduction 83 4.2. Oleaceae 84 4.3. Gesneriaceae 87 4.4. Plantaginaceae 89 4.5. Lamiaceae 95 Chapter 5. Constitutional versus Positional Monosymmetry 101 5.1. Introduction 101 5.2. Saxifragales 102 5.3. Malpighiales 104 5.3.1. Elatinaceae 104 5.3.2. Malpighiaceae 105 5.3.3. Old World Malpighiaceae 108 5.4. Ericales 110 5.4.1. Balsaminaceae 110 5.5. Geraniales 111 5.5.1. Geraniaceae 111 5.6. Brassicales 114 5.6.1. Brassicaceae 114 5.6.2. Tropaeolaceae 117 5.7. Solanales 120 5.7.1. Solanaceae 120 5.8. Asterales 125 5.8.1. Asteraceae 125 5.9. Dipsacales 128 5.9.1. Adoxaceae 129 5.9.2. Diervillioideae 130 5.9.3. Caprifolioideae 130 5.9.4. Valerianoideae 133 5.9.5. Dipsacoideae 134 5.9.6. Scabioseae 137 Chapter 6. Symmetry in Fabales 139 6.1. Introduction 139 6.2. Quillajaceae. 140 6.3. Fabaceae 142 6.3.1. Cercidoideae 142 6.3.2. Detarioideae 144 6.3.3. Caesalpinioideae 146 6.3.4. Faboideae 150 Chapter 7. Symmetry in Monocots 155 7.1. Introduction 155 7.2. Acorales 156 7.3. Alismatales 158 7.3.1. Melanthiaceae 158 7.3.2. Alismataceae 159 7.3.3. Hydrocharitaceae 160 7.4. Dioscoreales 161 7.4.1. Nartheciaceae 161 7.4.2. Dioscoreaceae 162 7.5. Liliales 163 7.5.1. Liliaceae 163 7.5.2. Alstroemeriaceae 164 7.6. Asparagales 165 7.6.1. Orchidaceae 165 7.6.2. Iridaceae 168 7.7. Commelinales 170 7.7.1. Commelinaceae 170 7.8. Zingiberales 172 7.8.1. Cannaceae 172 7.8.2. Heliconiaceae, Costaceae 174 7.9. Poales 176 7.9.1. Poaceae 176 Conclusion 181 References 201 Index 217