Plant Systematics Overview

• Plants


  Organisms that possess photosynthesis, cell walls, spores, and a more or less sedentary behavior
• Land plants


  • Trees
  • Herbs
  • Bushes
  • Grasses
  • Vines
  • Ferns
  • Mosses
• Archaea and Bacteria


  Small, mostly unicellular organisms that possess circular DNA, replicate by fission, and lack membrane-bound organelles
• Eukaryotes


  Unicellular or multicellular organisms that possess linear DNA (organized as histone-bound chromosomes), replicate by mitotic and often meiotic division, and possess membrane-bound organelles such as nuclei, cytoskeletal structures, and (in almost all) mitochondria
• Green plants (Chlorobionta)


  • Characterized by unique chloroplasts with specific pigments, thylakoid structures, and storage compounds
  • Comprise aquatic green algae and land-dwelling embryophytes (Embryophyta)
• Land plants (Embryophyta)


  • Evolved adaptations for terrestrial life, including: Protective outer cuticle against desiccation
  • Specialized reproductive organs (gametangia) with sterile cell layers
  • A life cycle with an intercalated diploid phase and an embryo stage
• Systematics


  Science that includes and encompasses traditional taxonomy (description, identification, nomenclature, and classification of organisms), and that has as its primary goal the reconstruction of phylogeny, or evolutionary history, of life
• Evolution


  Change and can be viewed as the cumulative changes occurring since the origin of the universe some 15 billion years ago
• Biological evolution


  The evolution of life, maybe defined (as it was by Charles Darwin) as descent with modification
• Mechanisms of evolution


  • Genetic drift (Frequency of traits changes in population due to chance events)
  • Natural selection (Traits that improve survival or reproduction accumulate in the population)
• Taxa (taxon)


  A group of organisms
• Components of taxonomy


  • Description
  • Identification
  • Nomenclature
  • Classification
• Character


  Features or attributes assigned to a taxon
• Character state


  Two or more forms of a character
• Identification


  Uses dichotomous keys, which consist of a series of two contrasting statements
• Nomenclature


  Formally naming taxa according to standardized systems, such as the International Code of Botanical Nomenclature (ICBN) for plants, algae, and fungi
• Genus name


  Always capitalized (e.g., Quercus)
• Specific epithet


  Not capitalized (e.g., agrifolia)
• Classification


  Arranges entities (such as taxa) into an ordered system to catalog and express relationships between them
• Taxonomic ranks


  • Dear King Philip Came Over For Good Soup
• Artificial system of classification


  Classifies organisms based on a few superficial characters
• Theophrastus (370-287 BC) classified plants based on their habit into four groups: Herbs, Undershrubs, Shrubs, and Trees
• Theophrastus made important contributions, including distinguishing between dicotyledons and monocotyledons, inflorescence types, and corolla structures
• John Ray (1627-1705) classified plants into herbs (including non-flowering cryptogams and flowering plants) and trees
• Carolus Linnaeus (1707-1778)


  The "Father of Modern Botany" who divided the plant kingdom into 24 classes based on the structure, union, length and the number of stamens
• Natural system of classification

  Based on the natural similarities of vegetative and floral characters among the organisms, considering various external and internal features like the anatomy of a cell, types of embryo and phytochemistry
• Phylogenetic system of classification

  Based on evolutionary sequence and genetic relationship, considering morphological characteristics found from fossil records and genetic constituents
• Two main phylogenetic systems of classification

  • Engler and Prantl system
  • Hutchinson's classification
• Englr and Prantl

  Considered floral characters like single whorl or no perianth, unisexual flowers pollinated by wind as primitive, and arranged plants based on the increasing complexity of the flower morphology
• Hutchinson's divisions of angiosperms

  • Monocotyledons
  • Dicotyledons (Lignosae - woody plants, Herbaoae - herbaceous plants)
• Hutchinson's divisions of monocots

  • Calyciflerae (calyx present)
  • Corolliferae (petaloid perianth)
  • Glumiflorae (perianth absent)
• Taxonomic characters


  Taxonomic attributes used to provide evidence from which relationships (the phylogeny) between taxa are inferred
• Taxonomic evidences


  • Morphology
  • Anatomy
  • Palynology
  • Cytology
  • Phytochemistry
  • Genome Analysis and Nucleic Acid Hybridization
  • Serology
• Morphology in relation to taxonomy


  Deals with the external characters of the plant such as Habit, Root structure, Stem structure, Stem habit, Bud structure, Leaf structure, Inflorescence type, Flower type, Perianth structure, Androecium type, Stamen character, Gynoecial type, Carpel structure, Ovule type, Fruit type, and Seed type
• Anatomy in relation to taxonomy

  Provides evidences from wood cell type, size and shape, Wood cell wall sculpture, pattern, Stealer pattern, Vascular bundle type, Xylem type, wood type and ray type, Ground tissue type, Epidermal type, Mesophyll type, Scleried type, Stomatal type, Trichrome type, crystal type, Nodal type, Venation type, Petiole vasculation type, Periderm origin, Phloem cell type, Specialized cell type
• Palynology

  The study of plant pollen, spores
• Cytology


  The study of structure and function of cells
• Phytochemistry


  The study of phytochemicals, which are chemicals derived from plants
• Genome Analysis and Nucleic Acid Hybridization


  Identification, measurement, arrangement of genomic features
• Serology


  Concerned with the nature and interactions of antigenic material