Plant defences

Plant defences

Physical defence responses include:
- Cellulose cell walls act as a barrier to pathogens.
- Tough waxy cuticle on leaves to control water loss acts as a barrier to pathogens.
- Layers of undigestible dead cells around stems (bark on trees) prevent plant being eaten by herbivores, and dead cells falling of sheds pathogens.
Chemical plant defence responses include antibacterial chemicals (e.g. tea tree leaves), or poisons to prevent being eaten by herbivores (e.g. deadly nightshade).
Mechanical adaptations include thorns and spines to prevent being eaten by herbivores, leaves that droop or curl when touched, knocking insects off, and mimicry to trick animals, e.g. some species have spotted leaves that look like butterfly eggs, which prevents butterflies from egg-laying to avoid competition.

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