Plant defense against herbivory refers to a range of adaptive mechanisms and strategies employed by plants to deter or mitigate damage caused by herbivorous organisms. Herbivory, the consumption of plant material by animals such as insects, mammals, or birds, poses a constant threat to the survival and reproductive success of plants. As a result, plants have evolved various defenses to reduce herbivore damage and minimize potential negative impacts on their growth and fitness.
These defense mechanisms can be categorized into constitutive and induced defenses. Constitutive defenses are continuously present and are part of a plant's innate characteristics. Examples of constitutive defenses include physical structures like thorns, spines, or trichomes, which act as physical barriers for potential herbivores. Additionally, plants may produce secondary metabolites, such as toxic chemicals or compounds that deter feeding or digestion. Constitutive defenses are considered pre-formed and always present.
Induced defenses, on the other hand, are triggered in response to herbivore attack or sensory signals. When plants detect damage or herbivore saliva, they activate specific defense pathways, leading to the production of toxins, repellents, or signaling compounds. Induced defenses can be chemical, such as the release of volatile organic compounds that attract natural enemies of herbivores or toxins that inhibit herbivore feeding. They can also be structural changes, such as increased lignification or cell wall fortification to make the plant less palatable or more difficult to digest.
In summary, plant defense against herbivory encompasses a range of constitutive and induced mechanisms aimed at reducing the impact of herbivores on plants. These defenses involve physical, chemical, and structural adaptations that increase plant survival and reproductive success.
