EFFECTS OF ENVIRONMENTAL FACTORS ON MECHANICAL PROPERTIES OF THE CELL WALL IN RICE COLEOPTILES

Cell wall properties determined by the stress-relaxation technique were studied with coleoptiles of rice seedlings grown under different environmental conditions. The cell wall was simulated by a viscoelastic model consisting of either four or an infinite number of Maxwell components. Reciprocal of relaxation time for the first component in the former model (1/τ1 ) and minimum and maximum relaxation times (To and Tm ) in the latter, in addition to the stress/strain ratio, were parameters representing cell wall properties. Parameters changed depending on the ages and regions of the coleoptilles used and 011 the environmental conditions under which rice seedlings were grown. Effects on cell wall properties of aeration during submerged growth, excision of the coleoptile tip, and exposure to small doses of red and/or far-red light were examined. In most cases, high values of 1/τ1 and of Tm and small values of To were consistent with the growth potentiality of cells, while the stress/strain ratio seemed to be a consequence of elongation growth.