Botany Study Notes

Botany Study Notes

PLANT TAXONOMY

  • Definition: The classification of plants in an ordered system that indicates natural relationships.

What is Plant Taxonomy?

  • Definition: The science that finds, describes, classifies, identifies, and names plants.

  • Taxonomist: A biologist specializing in the classification of organisms based on their structure, origin, and behavior.

Purpose of Taxonomy

  1. Draw up an inventory of the flora.

  2. Establish identification methods for plants and provide means of communication for scientists.

  3. Provide a classification system for related plants.

  4. Provide insight into the evolution of plants.

Elements of Taxonomy

  1. Description: Collecting plants and noting their characteristics.

  2. Identification: Comparing characteristics.

  3. Nomenclature: Establishing a naming system, often involving a dichotomous key.

  4. Classification: Arranging organisms into groups.

Description

  • Importance: A correct description allows experts to classify plants accurately. Essential for nurserymen, breeders, and producers.

Advantages of Accurate Description

  1. Enables farmers to predict if a cultivar is suitable for specific climatic conditions.

  2. Prevents confusion and duplication of names.

  3. Allows nurserymen to select mother material correctly and market true-to-type cultivars.

  4. Helps recognize off-type trees early.

  5. Ensures breeders are informed about cultivar characteristics and mother stock choices are facilitated.

Identification of Plants

  • Definition: Assigning a plant to a specific taxonomic group, ultimately to the species.

  • Identification Process: Determining if a specimen is identical or similar to known plants. Literature or comparison aids may be used, but naming is not involved in identification.

Methods of Identification

  • Locality References: When collecting an unknown plant, refer to regional plant accounting books, containing analytical keys and descriptions.

Key Characteristics for Plant Identification

  • Leaves: Shape, size, arrangement (simple or compound), and surface characteristics (serrated or smooth).

  • Flowers: Color, shape, size, arrangement, number of petals, presence of structures like stamens and pistils.

  • Stems: Types (woody or herbaceous), thickness, texture.

  • Growth Habit: Determining if the plant is a tree, shrub, vine, or herb; also annual, biennial, or perennial.

  • Habitat: The specific environment (e.g., wetlands, dry areas, forests) informing identification based on plant preferences.

Examples of Common Trees

  • Birch: Betula sp.

  • Black Poplar: Populus nigra

  • Sycamore: Acer pseudoplatanus

  • Alder: Alnus glutinosa

  • White Poplar: Populus alba

  • Blackthorn: Prunus spinosa

  • Apple: Malus sp.

  • Aspen: Populus tremula

  • Goat Willow: Salix caprea

  • Beech: Fagus sylvatica

  • Grey Poplar: Populus x canescens

  • Lime: Tilia sp.

  • Hawthorn: Crataegus sp.

  • Horse Chestnut: Aesculus hippocastanum

  • Field Maple: Acer campestre

  • Crack Willow: Salix fragilis

  • Ash: Fraxinus excelsior

  • Sweet Chestnut: Castanea sativa

  • Hazel: Corylus avellana

  • Elder: Sambucus nigra

  • Wild Cherry: Prunus avium

  • Rowan: Sorbus aucuparia

  • Oak: Quercus sp.

  • Wych Elm: Ulmus glabra

Categories of Leaves

  • Opposite: Example: American ash (Fraxinus americana)

  • Alternate: Example: Flowering dogwood (Cornus florida)

  • Simple: Example: Red maple (Acer rubrum)

  • Pinnate: Example: Black walnut (Juglans nigra)

  • Palmate: Example: Horse chestnut (Aesculus hippocastanum)

  • Compound: Example: Black locust (Robinia pseudoacacia)

Margins of Leaves

  1. Entire: E.g., Flowering Dogwood (Cornus florida)

    • Smooth, round edges

  2. Lobed: E.g., Red maple (Acer rubrum)

    • Earlobe-resembling protrusions

  3. Toothed: E.g., Horse Chestnut (Aesculus hippocastanum)

    • Sharp, serrated edges

Botanical Nomenclature

  • Definition: The scientific naming of plant species, controlled by the International Code of Botanical Nomenclature (ICBN).

  • Each plant receives a binomial Latin name, which includes the genus and species epithet.

Common and Scientific Names

  • **Common Name Examples:

    • Stemless lady slipper

    • Sweet fern
      Advantages:

    • Colorful and easy to remember.

    • Useful for non-scientists to communicate about plant diversity.
      Disadvantages:

    • One plant may have multiple common names, leading to confusion.

Scientific Names

  • Developed through International Botanical Congresses, with a primary goal to establish stable and correct names for taxonomic groups.

  • Authority: Refers to the person or group who first named a species (e.g., L. for Linnaeus).

  • Example: Carex buxbaumii Wahlenb.

Rules of Scientific Classification

  1. A genus name cannot be reused for different taxa; independent of animal and fungi nomenclature.

  2. Names can change frequently, leading to synonyms for the same species.

Taxonomic Concepts

  1. Morphological Species Concept: Defined by physical traits.

  2. Interbreeding Species Concept: Defined by reproductive isolation and interbreeding capabilities.

  3. Ecological Species Concept: Based on unique ecological niches.

  4. Cladistic Species Concept: Determined by evolutionary history.

Cladistics and Phylogenetics

  • Cladistics examines relationships based on shared features, clarified through cladograms.

  • Character States: Value or form of features; hypotheses about which are ancestral.

  • Principle of Parsimony: Seeks the explanation that makes the fewest assumptions (Occam's Razor).

Taxonomic Ranks

  • Systems include:

    • Species

    • Genus

    • Family

    • Order

    • Phylum

    • Kingdom

  • Cultivar: A specially cultivated variety of plant.

Taxonomic Systems and Examples

  1. Artificial Classification: Based on superficial features.

  2. Natural Classification: Based on hereditary characteristics, grouping plants with common origins.

  3. APG Systems: Various molecular-based systems (APG, APG II, APG III).

Inflorescence

  • Definition: The aggregation of flowers on a plant.

  • Kinds:

    1. Racemose Inflorescence (indefinite, monopodial)

    2. Cymose Inflorescence (definite, sympodial)

    3. Mixed Inflorescence (combination of both types).

Types of Inflorescence

  1. Racemose: Includes raceme, corymb, umbel, capitulum, spike, spadix, catkin, and strobile.

  2. Cymose: Can be simple or compound.

Flower Morphology

  • Defined as a condensed reproductive shoot with various parts:

    • Receptacle (Thalamus): Swollen part of the pedicel.

    • Sepals and Petals: Parts of the flower structure.

    • Stamens: Male reproductive component.

    • Pistil: Female reproductive component (comprises stigma, style, and ovary).

Types of Flowers

  • Complete Flower: All four whorls present.

  • Incomplete Flower: Missing one or more whorls.

  • Bisexual Flower: Contains both gynoecium and androecium.

  • Unisexual Flower: Contains either gynoecium or androecium.

  • Monoecious Plants: Male and female flowers present on the same plant.

  • Dioecious Plants: Male and female flowers on separate plants.