Growth and Stress-Relaxation Parameters for the Cell Wall of Normal and 10 Dwarf Barley Strains

Mechanical properties of the cell wall of 2- and 3-day-old barleycoleoptiles of normal and 10 dwarf strains were measured toexplain their different growth rates. Six parameters for mechanicalproperties (minimum and maximum stress relaxation time, relaxationrate, residual stress, strain ratio and the apparent Young'smodulus) were obtained by use of a stress-relaxation technique. The minimum stress-relaxation time and relaxation rate on day2, when the coleoptiles of all the strains had their maximumgrowth rates, were correlated significantly with the growthrates (r=0.79 and 0.72). When coleoptile growth in all the strainswas slowing down, the apparent Young's modulus was correlatedto the final coleoptile length. These results suggest (1) that when the coleoptile cell is activelygrowing, the minimum stress-relaxation time and relaxation rateof the cell wall affect the growth rate and (2) that the apparentYoung's modulus limits the final coleoptile length of the barleystrains examined. (Received October 13, 1983; Accepted April 16, 1984)