How plants defend insects.

Plants have evolved various defense mechanisms to protect themselves against insect herbivory, or the consumption of plant tissues by insects. These defense mechanisms can be grouped into two main categories: physical defenses and chemical defenses.

Physical defenses include structural features of the plant that make it difficult for insects to feed on or damage the plant. For example, some plants have thorns or spines that deter herbivores from feeding on them. Other plants have tough, fibrous leaves or bark that are difficult for insects to chew through.

Chemical defenses, on the other hand, involve the production and release of chemical compounds that are toxic or repellent to herbivorous insects. Some of these compounds are produced by the plant as a direct response to insect damage, while others are present in the plant tissues as a general defense mechanism. Examples of chemical defenses include:

Alkaloids: These are bitter-tasting compounds that are toxic to insects. They are present in many plant species, including tobacco, potatoes, and tomatoes.

Terpenoids: These are a diverse group of compounds that are toxic or repellent to insects. They are found in many plant species, including conifers, eucalyptus, and citrus.

Phenolics: These are a group of compounds that are involved in plant growth and development, but also have anti-insect properties. They are found in many plant species, including grapes, tea, and soybeans.

Essential oils: These are volatile compounds that are produced by many plants, and have insecticidal properties. They are used in many natural insecticides and repellents.

Overall, plants have evolved complex defense mechanisms to protect themselves against insect herbivores. These mechanisms are an important component of plant-insect interactions and have a significant impact on both the plants and the insects that feed on them.