Physical Plant Defences
- Animals possess a wide range of defence mechanisms to defend themselves against disease
- The same can be said for plants
- In leaves, plants put up some strong physical defences
- Waxy cuticle
- This keeps the leaf waterproof from rain and also prevents pathogens from getting in through the leaf surface
- Many pathogens are water-borne so they roll off the leaf in a raindrop and drop quickly onto the soil
- The cell wall
- Its main purpose is to provide strength and support but cellulose cell walls also act as a physical barrier to pathogens within the leaf
- Callose production
- The presence of pathogens can cause callose to form which forms a temporary extra cell wall between cells and adds support to cell walls
- This is particularly important when a piece of plant tissue is wounded or injured, exposing the cell contents to pathogens
- Production of antimicrobial substances
- Some plants produce antimicrobial substances to defend against pathogens
- These may kill the pathogen or prevent it from reproducing
- For example, basil plants produce essential oils called terpenoids that are active against species of Salmonella bacteria
- Even fruit sugar fructose, a simple sugar found in cranberries and many other fruit, has antibacterial properties because many pathogenic bacteria cannot metabolise fructose
Defence mechanisms employed by plants include those in the leaves: waxy cuticle, cell wall