What is induced defense in plants?

• A. Mechanical changes in plant tissues that deter insects.
• B. Chemical changes in plant tissues triggered by damage that deter insects.
• C. Structural hardening of tissues independent of damage.
• D. The production of nectar to attract pollinators.

Answer: (B)

Induced defense in plants is the set of chemical defenses that a plant activates after its tissues are damaged by herbivores. When a leaf or stem is chewed or wounded, plants often switch on production of defensive compounds such as tannins, alkaloids, protease inhibitors, and various terpenoids. They may also release volatile signals that recruit the herbivore’s natural enemies or warn neighboring plants. This response is dynamic and can be local to the damaged site or spread systemically to other parts of the plant, and it is coordinated by signaling molecules like jasmonates.

This is the best description because it focuses on chemical changes triggered by damage that deter insects, which is the defining feature of induced defenses. Mechanical changes in tissues can be part of defense but are not the core definition of induced chemical responses. Structural hardening independent of damage describes constitutive defenses that are always present rather than induced. Producing nectar to attract pollinators serves a reproductive function and is not a defense against herbivores.