Abstract
Stress-strain characteristics of the cell walls of cucumber hypocotyls were examined using glycerinated hollow cylinders (GHCs). As observed in cowpea, cucumber GHCs were found to have yield threshold tension (y). The y showed marked acid-induced downward shift that induces the acid-induced enhancement of wall creep. Such y-shift was inhibited by heat-treatments (boiling 15 sec) while the acid-induced increase of wall extensibility (φ) remained unchanged. Moderate concentration urea (2M) showed no promotion of the acid-induced creep but a little inhibition. Creep inhibitors such as high concentration urea (8M), trypsin and metal ions exerted characteristic effects on the changes of both φ and y resulting in creep inhibition. Taking all these findings into consideration, we discuss the mode of pH-sensitive wall creeping during the elongation growth and the possibility that the wall proteins such as expansins are not involved in the regulation of wall extensibility.
