Plants Produce Defensive Chemicals

1. Some plant chemicals kill microorganisms or slow their growth, reducing damage from pathogens.
2. Other chemicals are toxic, bitter or unpleasant to herbivores, so less plant tissue is eaten.
3. Poisons and bitter-tasting compounds reduce herbivore feeding, so less photosynthetic tissue is lost and fewer wounds are created.

Antimicrobial Chemicals Limit Pathogens

1. Antibacterial chemicals interfere with bacterial growth or cell processes.
2. Antifungal chemicals inhibit spore germination or fungal growth through plant tissue.
3. Plants may produce more defensive chemicals after tissue is damaged or infected.
4. Antimicrobial plant chemicals may disrupt microbial membranes, inhibit enzymes or prevent spores germinating.

Plant Chemicals Can Become Medicines

1. Scientists can isolate a plant chemical, test its biological effect and develop it into a medicine.
2. Aspirin was developed from compounds associated with willow, and digitalis medicines were developed from foxglove chemicals.
3. Medicines require controlled doses because a useful plant chemical may be toxic at a higher concentration.
4. A clear zone in a microbial culture shows inhibition, but disc size, extract volume, concentration, incubation time and microorganism must be controlled.

Evaluate Evidence for a Treatment

1. A laboratory result showing antimicrobial action is preliminary evidence, not proof that a substance is safe and effective in patients.
2. Further tests compare doses, side effects and effectiveness against a control treatment.
3. A potential medicine must pass toxicity, dose and effectiveness testing because activity in a culture does not show that it will be safe inside the body.

Use Precise Biological Language

1. A chemical that inhibits a pathogen reduces its growth or reproduction.
2. A chemical that deters a pest reduces feeding rather than necessarily killing it.