Cellulases, hemicelluloses and auxin-stimulated growth: a possible relationship.

The plant growth promoter, auxin, may loosen the primary cell wall by increasing the activity of extracellular cellulases - a group of enzymes that cleave hemicellulose chains in the walls of both monocotyledons and dicotyledons. Evidence is reviewed that suggests that these hemicellulose chains tether adjacent microfibrils, and that by cleaving such chains the cellulases facilitate cell expansion. On the basis of this structural arrangement a mechanism for elastic and plastic wall extension is proposed. [ABSTRACT FROM AUTHOR]