Studies on the Chemical Basis of Auxin-Induced Cell Wall Loosening

Abstract

Chemical changes accounting for the increase in wall extensibility of tissue grown in the presence of auxin were sought on the basis of chain scission mechanisms. Incorporation of glucose-14C into the hotwater extractable constituents from cell walls of basal sections of soybean hypocotyl was increased 15 min after the addition of auxin. However, this increase represented only 1%-2% of the total incorporation of radioactivity into the cell walls. With pea internode sections, both auxin-induced growth and incorporation of radioactivity from glucose-14C were inhibited at supraoptimal auxin concentrations that resulted in increased wall extensibility. No consistent correlation was found between wall loosening and rate of incorporation of glucose-14C into cell wall fractions, average length of wall polymers (based on number of free reducing groups), or the ratio of semicrystalline to amorphous wall materials (based on deuterium exchange). It is unlikely that wall loosening is mediated to a significant extent ...