Biology 200: Chapter 24 Flowering Plants

Introduction to Flowering Plants and Civilization

• Historical Context of Plants in Medicine:
  • Historically, plants have been used to treat various diseases.
  • Modern data has supported some of these historical medicinal uses.
  • However, it can be difficult to distinguish between factual evidence and fiction when examining recorded past uses of plants.

Geographical Origins of Cultivated Plants

• Centers of Diversity:

  • Cultivated plants appear to have originated in six major global regions.
  • Source Material: Derived from K. Starr Chester, Trans. New York: The Ronald Press Company.

• Regional Distributions:

  • Near-Eastern Region (Mediterranean and Northern Europe):
    • Includes: Barley, wheat, peas, lentils, asparagus, beets, carrots, turnips, olives, cherries, plums, apricots, apples, onions, garlic, broccoli, lettuce, flax, and pistachios.
  • Chinese Region (Temperate and Southern China):
    • Includes: Bamboo, peach, walnut, ginger, gourds, camphor, tea, soybean, buckwheat, horseradish, and cucumber.
  • African Continent (Primarily Ethiopia and West Africa):
    • Includes: Yams, sorghum, okra, sweet melons, coffee, and some cotton.
  • South Asia and Pacific Islands:
    • Includes: Sugar cane, eggplant, mango, banana, citrus, safflower, nutmeg, clove, cardamom, turmeric, black pepper, coconut, taro, rice, sesame, and onion.
  • North America:
    • Includes: Sunflower, cranberry, blueberry, and tobacco.
  • South and Central America:
    • Includes: Garden beans, corn, peanut, white potato, lima beans, cashew, pineapple, avocado, red pepper, tomato, cotton, cocaine, cacao (chocolate), sweet potato, pumpkin, squash, rubber, vanilla, and cassava.

Principles of Flowering Plant Classification

• Morphological and Genetic Perspectives:

  • Over $300$ families of flowering plants have been recognized.
  • Current classifications are largely based on morphology; however, DNA sequence data may lead to future reorganization of these groups.
  • Fruit and flower structures are considered more reliable indicators of heredity than leaves or other vegetative parts.
  • Note: Families with more generalized flower structures are typically presented first in botanical studies.

• Medical Warning:

  • Past medicinal uses were not always effective and often had harmful side effects.
  • Experimentation with these plants is strictly discouraged.

The Buttercup Family (Ranunculaceae)

• General Characteristics:

  • Approximately $1,500$ species, nearly all of which are herbaceous.
  • Geography: Concentrated in north temperate and arctic regions.
  • Toxicity: Most members are at least slightly poisonous.

• Floral Morphology:

  • Petals: Vary in number.
  • Stamens: Numerous.
  • Pistils: Several to many, featuring superior ovaries.

• Representative Species:

  • Buttercup.
  • Columbine: Distinguished by five spurred petals that resemble a circle of doves.
  • Hepatica.
  • Monkshood (or Wolfsbane):
    • Yields Aconite: A drug formerly used to treat rheumatism and neuralgia.
    • Extremely poisonous.
    • Historical use: Wolf hunters used the juice from the roots to poison wolves.
  • Isopyrum.

The Laurel Family (Lauraceae)

• General Characteristics:

  • Approximately $1,000$ species consisting of tropical evergreen shrubs and trees.

• Morphology:

  • Flowers: Lack petals, though sepals can sometimes appear petal-like.
  • Stamens: Arranged in three or four whorls; anthers open by lifted flaps.

• Economic and Practical Uses:

  • Cinnamon: Produced from the pulverized bark of a small tree.
  • Cassia: Similar to cinnamon.
  • Camphor: Used in cold remedies and insecticides.
  • Sassafras: Trees native to the eastern United States.
  • Sweet Bay: Used as flavoring in meat dishes.
  • Avocado.
  • California Bay.

The Poppy Family (Papaveraceae)

• General Characteristics:

  • Herbs typically found in temperate and subtropical regions.
  • All species in this family produce alkaloidal drugs.

• Morphology:

  • Stamens: Numerous.
  • Pistils: Single.
  • Sap: Characterized as milky or colored.

• Representative Species and Derivatives:

  • Prickly Poppy.
  • Opium Poppy:
    • Opium: White fluid extracted from capsules.
    • Includes: Morphine, codeine, heroin, papaverine, and noscapine.
    • Poppy seeds: Used in food.

The Mustard Family (Brassicaceae)

• General Characteristics:

  • Approximately $2,500$ species, mostly found in temperate and cooler regions of North America.
  • All members produce a pungent, watery juice.

• Morphology:

  • Petals: Four petals arranged in the shape of a cross.
  • Stamens: Six total ($2$ short and $4$ long).
  • Fruit: Classified as siliques or silicles.

• Cultivated Edible Plants:

  • Includes: Cauliflower, Brussels sprouts, broccoli, radish, turnip, horseradish, watercress, and rutabaga.
  • Mustard: Derived from the ground seeds of two species of Brassica.
  • Shepherd’s Purse.

The Rose Family (Rosaceae)

• General Characteristics:

  • More than $3,000$ species, including trees, shrubs, and herbs.
  • Enormous economic impact.

• Floral Morphology:

  • Basal parts are fused into a cup.
  • Petals, sepals, and numerous stamens are attached to the rim of this cup.
  • The family is subdivided into subfamilies based on flower and fruit structure.

• Fruits and Uses:

  • Stone Fruits: Cherries, apricots, peaches, plums.
  • Pome Fruits: Apples, pears.
  • Aggregate Fruits: Strawberries, blackberries, raspberries.
  • Ornamentals: Roses (used for fragrances).
  • Rose Hips: The fruit of roses, which are high in Vitamin C.

The Legume Family (Fabaceae)

• General Characteristics:

  • The third largest flowering plant family with $13,000$ species.
  • Cosmopolitan distribution (found worldwide).

• Morphology:

  • Symmetry: Flowers range from radial to bilateral.
  • Stamens: Fused into a tube surrounding the ovary.
  • Fruit type: Legume.

• Important Crop Plants:

  • Includes: Peas, beans, soybeans, peanuts, alfalfa, sweet clover, licorice, carob, and winged bean.
  • Notable example: Sweet pea.

The Spurge Family (Euphorbiaceae)

• General Characteristics:

  • Found in tropical and temperate regions.
  • Stamens and pistils are produced in separate flowers.
  • Flowers are often inconspicuous and lack a corolla.

• Morphology and Inflorescence:

  • Cyathium: The specific inflorescence type.
  • Female flower: Elevated on a stalk called a gynophore and surrounded by several male flowers.
  • Male flowers: Consist of little more than an anther.
  • Orientation: Flowers are inserted on a cup of fused bracts, usually with glands on the rim.
  • In some species, such as the Poinsettia, flowers are surrounded by colored bracts.

• Economic Importance:

  • Cassava: A staple food in tropical regions.
  • Para Rubber Tree: Crude rubber is derived from the latex found in the inner bark.

The Cactus Family (Cactaceae)

• General Characteristics:

  • Over $1,500$ species native specifically to the Americas, typically in dry, subtropical regions.

• Morphology:

  • Leaves: Reduced in size and often modified into spines.
  • Stems: Fleshy.
  • Flowers: Showy, with numerous stamens, petals, and sepals.
  • Ovary: Inferior, developing into a berry.

• Practical Uses:

  • Most produce edible fruit, such as Prickly Pear fruits.

The Mint Family (Lamiaceae)

• General Characteristics:

  • Approximately $3,000$ species.
  • Features a unique combination of square/angular stems (in cross-section), opposite leaves, and bilaterally symmetrical flowers.
  • Ovary: Superior and four-parted, developing into four nutlets.

• Mint Oils and Medicinal Uses:

  • Plants produce oils used medicinally and as antiseptics.
  • Menthol: Used in toothpaste, candies, gum, liqueurs, and cigarettes.
  • Representative Herbs: Rosemary, thyme, sage, oregano, marjoram, basil, lavender, catnip, peppermint, and spearmint.
  • Example: Lamb’s ear mint.

The Nightshade Family (Solanaceae)

• General Characteristics:

  • Approximately $3,000$ species, concentrated in the tropics of Central and South America.
  • Many species are poisonous, while some have drug applications.

• Morphology:

  • Flowers: Fused petals with stamens fused to the corolla.
  • Ovary: Superior, developing into a berry or capsule.

• Economically Important and Medicinal Plants:

  • Food/Industrial: Tomato, white potato, eggplant, peppers, petunia, and tobacco.
  • Belladonna Drug Complex:
    • Atropine: Used for shock treatment and pain relief.
    • Scopolamine: Used as a tranquilizer.
  • Capsicum (from red pepper): Used as a gastric stimulant.
  • Jimson Weed: Used for asthma.

The Carrot Family (Apiaceae)

• General Characteristics:

  • Approximately $2,000$ members widely distributed in the Northern Hemisphere.
  • Savory-aromatic herbs with dissected leaves and petiole bases that form sheaths around the stem.

• Morphology:

  • Flowers: Small, numerous, and arranged in umbels.
  • Ovary: Inferior, with a two-lobed stigma.

• Representative Species:

  • Edibles/Spices: Dill, celery, carrot, parsley, caraway, coriander, fennel, anise, and parsnip.
  • Poisonous Members: Water hemlock (believed to have caused the death of Socrates via ingestion).

The Pumpkin Family (Cucurbitaceae)

• General Characteristics:

  • Approximately $700$ species of prostrate or climbing herbaceous vines.
  • Many have been cultivated for so long they are unknown in the wild state.

• Morphology:

  • Flowers: Unisexual with fused petals.
  • Female flowers: Feature an inferior ovary comprising three carpels.

• Important Edible Plants:

  • Includes: Pumpkins, squashes, cucumbers, cantaloupes, and gourds.

The Sunflower Family (Asteraceae)

• General Characteristics:

  • The second largest flowering plant family with over $23,000$ species.

• Morphology:

  • Florets: Individual flowers that make up the whole.
  • Inflorescence: A compact arrangement of florets that resembles a single flower.

• Representative Species:

  • Includes: Dandelions, lettuce, endive, chicory, artichoke, dahlia, chrysanthemum, marigold, sunflower, and thistle.
  • Tarragon: Used as a spice in meat and pickles.

The Grass Family (Poaceae)

• Floral and Structural Morphology:

  • Pollination: Wind-pollinated and highly specialized.
  • Calyx/Corolla: Reduced to tiny scales.
  • Bracts: Boat-shaped bracts protect the flowers.
  • Stigmas: Exposed and feathery.
  • Leaves: Bases sheath the stems.

• Economic Importance:

  • Contains nearly all cereals: Wheat, barley, rye, oats, rice, and corn.
  • Other uses: Baskets, fibers, and thatching for huts.
  • Citronella Oil.

• Sugar Cane Processing:

  • Plant can grow up to $6\,m$ tall.
  • Squeezed juice is centrifuged.
  • Solids crystallize into table sugar, while the dark remaining liquid is molasses.

The Lily Family (Liliaceae)

• General Characteristics:

  • Occur in nearly any area supporting vegetation.

• Morphology:

  • Floral parts are in multiples of three.
  • Sepals and petals अक्सर (often) resemble each other.

• Representative Species and Uses:

  • Includes: Lilies, daffodils, asparagus, sarsaparilla, Aloe, onions, and garlic.
  • Meadow Saffron: Source of colchicine, used to treat rheumatism.
  • Bowstring Hemps (Sansevieria):
    • Used as house plants.
    • Provide long fibers for string, rope, and bowstrings.
  • California Soaproot:
    • Confined to California and southern Oregon.
    • Bulb used for soap; coarse fibers used for brooms.

The Orchid Family (Orchidaceae)

• General Characteristics:

  • Very large family with over $35,000$ species, especially abundant in the tropics.
  • Diverse habitats: Can be epiphytic (on tree bark), aquatic, terrestrial, or saprophytic.

• Floral Morphology:

  • Structure: Three sepals and three petals; one petal (the lip petal) differs from the other two.
  • Column: A single structure resulting from the fusion of stamens and pistil.
  • Pollinia: Sacs of pollen found in the anthers.

• Reproduction and Growth:

  • Seeds: Produced in prodigious numbers but are minute, consisting of only a few cells.
  • Germination: The seed must associate with a specific mycorrhizal fungus to successfully germinate.

• Practical Application:

  • Vanilla: Extracted from the vanilla orchid.