Poisonous and Allergy Plants Notes

Chapter 21: Poisonous and Allergy Plants

Necessary Vocabulary

  • Chemical defenses: Plant mechanisms that produce chemicals to deter herbivores or pathogens.
  • Toxic: Substances that can cause harm or death at certain concentrations.
  • Poison: A substance that kills an organism upon exposure.
  • Strychnine: An alkaloid toxin that affects the nervous system.
  • Curare: A plant alkaloid used as a muscle relaxant and poison.
  • Coniine: A toxic alkaloid found in poison hemlock.
  • Hemlock: A plant known for its toxic properties.
  • Galitoxin: A poison derived from certain plants.
  • Milkweed: A plant known for its toxic glycosides that affect herbivores.
  • Allelopathy: A biological phenomenon where plants release chemicals affecting the growth of surrounding plants to gain competitive advantages.
  • Oleander: A plant that contains toxic compounds affecting the heart.
  • Castor bean: Contains ricin, a potent toxin.
  • Snakeroot: Contains tremetone, toxic to animals and humans.
  • Mechanical defenses: Physical structures that deter herbivores (e.g., thorns, spines).
  • Insecticide: A substance that kills insects.
  • Pyrethroids: Synthetic insecticides modeled after pyrethrins.
  • Neem oil: An oil derived from the neem tree used as a natural pesticide.
  • Allergic response: Immune reaction to innocuous substances known as allergens.
  • Respiratory allergies: Allergies affecting the respiratory system.
  • Hay fever: Allergic reaction associated with pollen.
  • Allergic asthma: Asthma triggered by allergens.
  • Contact dermatitis: Skin reaction from exposure to allergens.
  • Food allergies: Immune response to specific food proteins.
  • Latex: A common allergen found in natural rubber.
  • Rotenone: A natural insecticide derived from certain plants.

Big Questions

  1. List the poisonous plants, the substances causing effects in humans, the effects on humans, and the parts of the plant producing these substances.
  2. Define allelopathy. What chemicals do the plants produce? Why does this give the plant an advantage?
  3. Which plant structures cause mechanical damage?
  4. Which plants are used to make insecticides?
  5. How does the human body react to an allergen?
  6. Which plants commonly cause seasonal allergies?

Introduction to Poisonous Plants

  • There is a perception that plants can pose risks to humans.
  • Poison: Any substance that can kill an organism.
  • Toxic / toxin: Substances that can kill in high doses and cause adverse effects at lower doses.

Human Immune System

  • Lymphatic System: Composed of immune system fluid and various white blood cells.
      - Function: Recognizes shapes of molecules like proteins and carbohydrates, crucial for immune response.
      - Examples of allergies include:
        - Celiac Disease (from grasses)
        - Peanut allergy (from legumes)
        - Allergies to fruits like watermelon and strawberry.
Antigen Presentation
  1. A phagocyte engulfs bacteria.
  2. Bacterial parts (antigens) are displayed on the phagocyte's surface.
  3. This presentation activates a helper T cell.
  4. An activated helper T cell stimulates the immune response further.
B Cell Activation
  1. A B cell finds an antigen matching its receptors.
  2. The B cell divides to produce plasma and memory cells.
  3. It waits for activation by a helper T cell.
  4. Plasma cells produce antibodies that mark invaders for destruction.
  5. Eater cells (phagocytes) consume invaders tagged by antibodies.
  6. Memory cells ensure a faster response upon re-exposure to the same invader.
Activation of the Immune System
  • Activation pathways:
      - From the digestive system or damage (e.g., cuts).
  • Inflammation response: Causes heat and swelling to help eliminate invaders.
      - Chemicals (cytokines) are released to combat infectious agents.
      - Note: The inflammation response can damage healthy cells.
Allergic Response Symptoms
  • Common reactions to allergens include:
      - Watery eyes and runny nose
      - Diarrhea and vomiting
      - Swollen, itchy lymph nodes
Immune System Facts
  • The human immune system can recognize approximately 101510^{15} different antibodies throughout a lifetime.
  • Lymph fluid moves primarily when muscles contract.

Common Poisonous Plants

1. Strychnos nux-vomica
  • Common Name: Asian vomit button tree
  • Origin: Asia & India
  • Part Used: Roots and stems
  • Compound Extracted: Alkaloids - Strychnine & brucine
  • Important Details:
      - Causes neuron damage.
      - Used in rodent poison.
      - Associated with increased athletic performance (weak correlation).
      - Strychnine binds to glycine receptors amplifying CNS signals.
      - Causes convulsions, leading to asphyxiation; very fast acting (death within ~30 minutes).
      - No known cure; muscle relaxers may alleviate symptoms.
2. Strychnos toxifera
  • Origin: South America
  • Part Used: Any part of the plant
  • Compound Extracted: Strychnine.
  • Important Details:
      - Grows as a vine, historically used to make curare (poison arrows).
3. Atropa belladonna
  • Common Name: Deadly nightshade
  • Origin: Europe & Asia
  • Part Used: Any part of the plant
  • Compound Extracted: Atropine (alkaloid)
  • Important Details:
      - Disrupts acetylcholine function.
      - Causes pupil dilation, hallucinations, and body temperature regulation issues.
      - Antidote for digitoxin poisoning.
4. Aconitum
  • Common Name: Monkshood
  • Origin: Europe, Asia & North America
  • Part Used: Any part
  • Compound Extracted: Aconite (alkaloid)
  • Important Details:
      - Historically used to treat gout.
      - Prevents sodium channels from closing in nerve cells.
      - Causes numbing, tingling, and increased heart rates.
5. Conium maculatum
  • Common Name: Poison Hemlock
  • Origin: Europe
  • Part Used: Any part of the plant
  • Compound Extracted: Coniine
  • Important Details:
      - Symptoms resemble nicotine overdose (headache, nausea, vomiting).
      - Introduced to North America.
6. Cicuta maculatum
  • Common Name: Water Hemlock
  • Origin: North America
  • Part Used: Roots
  • Compound Extracted: Circutoxin
  • Important Details:
      - Onset: Symptoms within ~60 minutes (nausea, convulsions).
      - Known colloquially as the “suicide root.”
7. Asclepias spp.
  • Common Name: Milkweed
  • Origin: North America
  • Part Used: Any part
  • Compound Extracted: Glycosides similar to digitalis
  • Important Details:
      - Toxic to most organisms; monarch caterpillars can consume it without dying but lose fitness.
8. Nerium oleander
  • Common Name: Oleander
  • Origin: Asia (research ongoing)
  • Part Used: Any part
  • Compound Extracted: Glycosides
  • Important Details:
      - Often used in landscaping; burning releases airborne toxins.
9. Taxus spp.
  • Common Name: Yew
  • Origin: Various (species-dependent)
  • Part Used: All parts, except arils surrounding seeds
  • Compound Extracted: Taxine alkaloids
  • Important Details:
      - Common in landscaping; burning releases airborne toxins.
10. Ricinus communis
  • Common Name: Castor Bean
  • Origin: East Africa
  • Part Used: Seeds
  • Compound Extracted: Ricin (alkaloid)
  • Important Details:
      - Highly poisonous; as few as 4-8 seeds can be lethal.
      - Ricin prevents ribosomes from functioning, causing cell death over several days.
11. Ageratina altissima
  • Common Name: White Snakeroot
  • Origin: North America
  • Part Used: All parts (mainly leaves & stems)
  • Compound Extracted: Tremetone ketone
  • Important Details:
      - Causes muscle weakness and tremors in animals, which can be concentrated in their flesh leading to illness in humans.

Plants Requiring Contact for Reaction

Poisonous Plant Group
  • This group includes plants that need only touch to affect humans, unlike the first group which requires ingestion.

  1. Poison Ivy (Toxicodendron radicans)
       - Origin: North America
       - Part with Compounds: Primarily leaves
       - Compound Extracted: Urushiol oils
       - Important Details: Causes intense itching and blistering when touched; oils become airborne when burned.

  2. Poison Oak (Toxicodendron diversilobum)
       - Similar in effects and characteristics to poison ivy.

  3. Poison Sumac (Toxicodendron vernix)
       - Origin: North America
       - Part with Compounds: Primarily leaves
       - Compound Extracted: Urushiol oils
       - Important Details: Notably, the leaf petiole is bright red and causes similar dermatitis responses like the others.

Mechanical Defense in Plants

  • Many cacti develop leaves into spines for mechanical protection against herbivores, effectively causing physical harm to predators.
Examples:
  • Cacti: modifications include rolled-up leaves into spines.
  • Devil’s Claw (Proboscidea parviflora): fruit locks together to deter herbivory.
  • Stinging Nettle (Urtica dioca): releases histamines and causes skin rashes by trichomes injecting irritants.

Phytotoxic Plants

  • Certain plants release phytotoxins that may cause skin rashes when in contact.
Examples:
  • Saint John’s Wort (Hypericum perforatum): causes skin rashes due to a phototoxic oil activated by sunlight.
  • Snow on the Mountain (Euphorbia marginata): similarly causes skin rashes.
  • Wild Parsnip (Pastinaca sativa): known for causing rashes through sun-exposed skin.

Insecticidal Chemicals from Plants

  • Plants generate various chemicals as a defense against herbivores. Some of these compounds are now used in human-made insecticides.
Notable Insecticides:

  1. Rotenone
       - Plant Sources: Tropical legumes (Lonchocarpus or Derris).
       - Mechanism: Acts as a neurotoxin, paralyzing insects.
       - Ecological Impact: Toxic to fish, causing fish kills in waterways.

  2. Pyrethrins
       - Plant Sources: Chrysanthemum cinerariiolium and Chrysanthemum coccineum.
       - Mechanism: Disrupts nerve function.
       - Environmental Considerations: Breaks down in sunlight, accumulates in sediment, harmful to bees.

  3. Neem Oil
       - Plant Source: Neem tree (Azadirachta indica).
       - Mechanism: Creates a physical barrier against insects while being less toxic to pollinators.

Allelopathy

  • Definition: A biological phenomenon in which certain plants release chemicals through their roots to inhibit the growth of nearby plants, essentially engaging in competitive biochemical warfare in the soil.
  • This leads to distinct spatial arrangements of plant life across landscapes.
Examples of Allelophtic Plants:
  1. Black Walnut: Suppresses growth of deep-rooted competitors with chemical secretions.
  2. Thistle: Secretes root chemicals inhibiting other plant growth.
  3. Blue Fescue Grass: Can hinder nearby plant growth due to secretions.
  4. Red Bottlebrush Plant: Utilized in hedgerows; exhibits allelopathic properties, influencing plant distribution in ecosystems.

Cautionary Advice About Ethnobotany

  • Example: Into the Wild depicts an individual’s fatal mistakes in plant identification highlighting the risks of consuming misidentified plants.
  • Wild sweet pea seeds, although seemingly innocuous, contain toxins halting nutrient absorption in the digestive system.
  • Contrast between wild sweet pea and Eskimo potato demonstrates the necessity for careful plant identification, as misidentification can lead to dire consequences.