3.3.2 Plant Defence Responses

What are the three types of plant defences?

Physical, chemical, and mechanical defences.

What are physical plant defences?

Defences that prevent the invasion of microorganisms.

Give two examples of physical plant defences.

A tough waxy cuticle stops entry into leaves, and cellulose cell walls form a physical barrier into the cells.

What are chemical plant defences?

Defences that deter predators or kill bacteria.

Give two examples of chemical plant defences.

Poisons from plants like foxgloves and deadly nightshades deter herbivores, and antibacterial compounds kill bacteria (e.g. mint and witch hazel).

What are mechanical plant defences?

Defences that physically stop or deter animals from eating the plant.

Give three examples of mechanical plant defences.

Thorns and hairs deter animals from eating, leaves droop or curl to move insects away, and mimicry tricks animals into avoiding them.

What is mimicry in plants?

Some plants droop to look unhealthy, others mimic butterfly eggs to avoid egg-laying, and some like the 'ice plant family' resemble stones to avoid predation.