Ernauxin

Ernauxin is a hypothetical plant hormone described in educational and theoretical discussions as an auxin-like regulator of plant growth. The name appears as a placeholder in models of polar auxin transport and in classroom demonstrations of plant developmental physiology. In these contexts ernauxin is treated as a small, weakly acidic molecule analogous to indole-3-acetic acid (IAA) that can move through plant tissues and influence cell elongation and pattern formation.

In model scenarios, ernauxin participates in the acid-growth mechanism by stimulating proton-pumping activity in the plasma membrane, lowering cell wall pH and enabling cell expansion. It is also used in simulations of apical dominance, lateral root initiation, and tropic responses, where its transport is assumed to be directed by PIN-family efflux carriers similarly to real auxins.

Biochemical properties and biosynthesis are not defined in real organisms because ernauxin has not been isolated or characterized in nature; rather, it serves as a pedagogical stand-in for discussing structure-activity relationships among auxins. Because it is not a confirmed natural or synthetic compound, there are no standardized synthesis routes, receptor binding assays, or regulatory networks associated with ernauxin in the scientific literature. If encountered in curricula, ernauxin provides a framework for comparing auxin-like molecules and exploring how transport, metabolism, and signaling shape plant development. Researchers generally use real compounds such as IAA, 2,4-D, or NAA for experimental work instead of ernauxin.