Phytoalexin

Thu, 02 Apr 2026 00:00:00 +0000

A phytoalexin is a defensive compound that a plant synthesizes de novo in response to stress — pathogen infection, ultraviolet radiation, physical damage, or herbivore attack. Unlike constitutive defenses (compounds always present), phytoalexins are induced: the plant produces them only when threatened. The term was coined by Müller and Börger in 1940 from Greek phyton (plant) + alexein (to ward off).

Phytoalexins are typically low-molecular-weight antimicrobial compounds that accumulate at the site of infection, creating a localized chemical barrier against the invading pathogen. They belong to diverse chemical classes depending on the plant family: stilbenoids in Vitaceae (grapes) and Polygonaceae (knotweeds), isoflavonoids in Fabaceae (legumes), sesquiterpenes in Solanaceae (nightshades), indole derivatives in Brassicaceae (mustards).

Plant Signaling: Molecular Mechanisms

Sat, 28 Mar 2026 00:00:00 +0000

This file covers the biochemistry and molecular biology of plant signaling systems. For the ecological and relational framing, see plant-signaling.md.

¶1. Phytohormone Signaling

Plants use at least nine major classes of hormone. Each is synthesized through specific enzymatic pathways, perceived by identified receptor proteins, and transduced through defined signaling cascades.

¶1.1 Auxin (Indole-3-Acetic Acid, IAA)

Function. Cell elongation, apical dominance, tropisms (photo- and gravitropism), vascular differentiation, lateral root initiation, embryo patterning.

Plant-Defense on emsenn.net

Phytoalexin

Plant Signaling: Molecular Mechanisms

¶1. Phytohormone Signaling

¶1.1 Auxin (Indole-3-Acetic Acid, IAA)