Plant Defence Responses (AQA GCSE Biology)

Physical & Chemical Defences

• Plants have a range of defence mechanisms to infections and infestations

• These can be split into physical and chemical defences

• Plants have adaptations to prevent herbivores from eating them (see Adaptations)

Physical Defences

• The cellulose cell wall not only provides support for the plant but also protection from microorganisms

• The waxy cuticle of the leaf is a barrier to microbes from entering the plant. The only place that they can enter in the leaf is through the stomata

• Bark provides a tough layer around the stem of the plant to prevent pathogens from entering

• As deciduous trees lose leaves in the winter the infection can be taken with them

Chemical Defences

• Many plants produce chemicals that have antimicrobial properties

• Many herbal face creams can use plant extracts such as tea tree oil, mint and witch hazel to have an antibacterial effect

• More plants are being studied for their potential source of antibiotics as more strains are becoming resistant to current antibiotics

Adaptations Against Herbivores

• Herbivores eating a plant can seriously damage the plant structures and they will not flower and reproduce

• Smaller insect infections can remove essential nutrients and energy from the plant and act as vectors for pathogens

Plant adaptions table