CHARACTERIZATION OF HYDRATION-DEPENDENT WALL-EXTENSIBLE PROPERTIES OFRYE COLEOPTILES - EVIDENCE FOR AUXIN-INDUCED CHANGES OF HYDROGEN-BONDING

The magnitude of changes of wall-extensible properties due to changes of the composition or concentration of wall solutions may reflect chan ges in polymer interactions relevant for growth regulation. Employing this approach, the present study demonstrates that in rye coleoptiles (Secale cereale L.) turgor-mediated wall stress can, in principle, be borne by non-covalent polymer interactions. Transfer of turgid coleopt ile segments to methanol fixed the immediate tension-stressed wall len gth dimensions despite turgor elimination. Length dimensions of methan ol-incubated, previously turgid walls of coleoptile segments could rev ersibly be fixed or relaxed to defined extension states depending on w all water content. Previously auxin-incubated segments exhibited an in creased stress relaxation by this method, i.e. they exhibited stronger shrinkage in dependence of defined hydration conditions as compared w ith control. Methanol-mediated fixation of wall length dimensions, inc lusive therein conserved wall stresses, is due to removal of the water from the walls and thereby increased hydrogen bonding between wall po lymers. Auxin-incubated segments therefore are characterized by a decr ease of hydrogen bonding. Denaturation of wall protein by boiling segm ents in water, depectination or extraction of non-covalently bound (gl yco)protein did not impair methanol-induced fixability of wall lengths tension-stressed in the extensiometer. Regulation of auxin-induced gr owth, therefore, in principle may also depend on polymer interactions as the ones affected by changes of hydration conditions due to methano l treatment, i.e. changes in hydrogen bonding.