DENDROLOGY

Detailed explanation-1: -Phytoalexins are antimicrobial substances, some of which are antioxidative as well. They are defined, not by their having any particular chemical structure or character, but by the fact that they are defensively synthesized de novo by plants that produce the compounds rapidly at sites of pathogen infection.

Detailed explanation-2: -Defensive chemicals present in plants are broadly classified into nitrogen-and non-nitrogen-containing compounds. Compounds that contain N include cyanogenic glucosides, alkaloids, and nonprotein amino acids. Defensive compounds without N include tannins, terpenes, phytoalexins, steroids, and phenolic acids.

Detailed explanation-3: -Examples of common secondary metabolites used as chemical defenses by plants include alkaloids, phenols, and terpenes. Defensive chemicals used to avoid consumption may be broadly characterized as either toxins or substances reducing the digestive capacity of herbivores.