Plant disease

Like animals, plants have developed a range of defence mechanisms to protect against pathogens and herbivores. These defences can be physical, chemical, or mechanical.

Physical Defences

These defences act as barriers to prevent pathogens from entering the plant, similar to the skin in humans:

• Cellulose cell walls provide a strong outer layer for each cell.

• Tough waxy cuticle on leaves prevents microorganisms from entering.

• Layers of dead cells around stems, such as bark on trees, provide a protective barrier that falls off, removing pathogens.

Chemical Defences

Plants also produce chemicals to protect against pathogens, similar to how stomach acid in humans helps kill microbes:

• Antibacterial chemicals: Some plants produce chemicals that kill bacteria. For example, herbs like mint and oregano contain natural antimicrobials.

• Poisons: Plants like foxglove and deadly nightshade produce toxins that deter herbivores.

Mechanical Adaptations

Mechanical adaptations help protect plants by deterring animals or tricking them:

• Thorns and hairs: Cacti and some other plants have these features to prevent animals from eating them.

• Leaves that droop or curl when touched: This movement can deter herbivores by moving the leaves out of reach.

• Mimicry: Some plants resemble other objects, like stones or pebbles, to avoid being eaten.