Pathogens are disease-causing viruses, bacteria, fungi or protists which attack plants as well as animals. Plants have physical and chemical defences against pathogens.
Just like animals, plants are constantly defending themselves from attack from pathogenMicroorganism that causes disease.. Again like us, plants have physical and chemical defences which stop pathogens from infecting them and causing disease.
Physical defences
Many plants are covered with a thick bark. This is an external layer of dead cells which forms a physical barrier against infection. In this way it is very much like our skin. Beyond bark, each plant cell has a celluloseA carbohydrate. It forms the cell wall in plant cells. cell wall which acts as another barrier against infection. Leaves are covered with a waxy cuticle The outer layer of a leaf which protects it. which also stops their cells from becoming infected.
Chemical defences
Some plants such as mint and witch hazel produce antibacterial chemicalsNaturally occurring chemicals made by plants like mint and witch hazel which protect them from bacterial pathogens.. These limit the spread of bacteriaSingle-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium. that were not stopped by physical defences. These chemical defences are now used in antiseptics for humans.
Other plants, like stinging nettles, have developed poisons to stop themselves being eaten by herbivoreAn animal that feeds only on plants.. These do not defend plants from infection by pathogens.
Other defences
Farmers can now genetic engineeringProcess which involves the artificial transfer of genetic information from one donor cell or organism to another. crop plants to be resistant to infections.