Pathogens can cause diseases in plants, for example, rose black spot and tobacco mosaic virus (TMV). Plants are vulnerable, so they are constantly fighting off pathogens and pests. Just like humans, plants have both physical and chemical defences to fight and prevent infection and disease.
Some of the plant’s physical characteristics provide defence against pests and pathogens.
Physical barriers are sometimes not enough to protect a plant. Some plants produce chemicals that have antimicrobial properties.
Some plants protect themselves from herbivores. For example, stinging nettles contain long, thin hairs that can inject toxins into the skin of a herbivore when touched. The toxins can cause irritation or pain, so their purpose is to deter herbivores from eating the plant.
Farmers can also genetically engineer plants to make them resistant to infections.
The structural features of plants can help to protect them from herbivores. For example:
|Adaptation||How they protect the plant||Example|
|Thorns and hairs||Makes it unpleasant or painful for herbivores to touch or eat the plant||Brambles and cacti|
|Mimicry||Plants can manipulate their appearance to confuse herbivores or pollinators||The hammer orchid mimics a female wasp to lure males into depositing and picking up pollen|
|Drooping leaves||Some leaves droop or curl up when touched. This can dislodge insects and protect the plant from being eaten||The Mimosa pudica plant closes its leaves and droops its stem when touched, making it more difficult for insects to feed on the leaves|