Plant Defences: Physical Barriers and Chemicals

Plants face threats from pathogens and pests. They defend themselves using physical barriers like cell walls and bark, which protect against pathogens, and chemical defenses like antimicrobial substances and poisons, which deter both pathogens and pests. Humans have harnessed some of these plant chemicals for medicinal purposes, such as aspirin from willow bark and digitalis from foxglove. The video concludes by summarizing the dual defense strategies of plants.

What are pathogens that attack plants?

• Birds like sparrows

• Large animals like deer

• Microorganisms like bacteria

• Insects like bees

Which physical barrier in plants is effective against pathogens?

• Cellulose cell wall

• Bright flowers

• Deep roots

• Sharp thorns

Why are physical barriers ineffective against pests?

• Pests are not interested in plants

• Pests are too small

• Pests can penetrate barriers

• Pests are repelled by barriers

What type of chemicals do plants produce to deter pests?

• Growth hormones

• Photosynthesis enzymes

• Insect repellents

• Antimicrobial chemicals

Which plant is known for producing a poison?

• Willow

• Marigold

• Foxglove

• Mint

What is aspirin derived from?

• Willow bark

• Mint leaves

• Marigold petals

• Foxglove flowers

Which plant chemical is used in heart medication?

• Aspirin

• Quinine

• Digitalis

• Menthol