Mechanical properties and polysaccharide nature of the cell walls of maize root

Changes in mechanical properties and chemical nature of the cell walls of the different zones along elongating maize ( Zea mays L. cv. LG 11) roots were analyzed and the following results were obtained. (1) The apical region 2 to 5 mm from the tip of 15 mm long roots showed rapid elongation whereas the region 8–10 mm from the tip showed very little growth. (2) The minimum stress-relaxation time (To) and the mean stress-relaxation rate (R) of the cell wall were small whereas the maximum stress-relaxation time (Tm) was large in the region where cell elongation was optimum. The To and R increased and the Tm decreased gradually towards the base of the root. (3) The amounts of non-cellulosic polysaccharides of the cell wall were highest in the region 1.5–2.5 mm from the tip, decreasing until 5 mm from the tip, and then increasing towards the base. However, the proportion of this fraction in the total cell wall polysaccharides was highest in the extreme tip (cap and meristem, 0–1 mm) and decreased towards the base. (4) Major neutral sugars constituting the non-cellulosic polysaccharides of the cell wall were xylose, arabinose, galactose and glucose, with minor amounts of rhamnosc. mannose and fucose. The 1–15 mm region was on the whole rich in glucose and xylose and contained arabinose to a lesser extent. However, the chemical nature in the apical region, (0–2 mm, was rather special, being rich in galactose and fucose. (5) The cell wall of maize roots contained, as a whole, only little pectic substances but was high in hemicellulose 1 (rich in xylose, arabinose and glucose) and hemicellulose 2 (rich in glucose and xylose). (6) It appeared that in the elongating region (apical 2 to 5 mm) the cell elongation rate (CET) showed a rather good correlation with the parameters of mechanical properties (To, Tm and R) and with neutral sugar compositions in the non-cellulosic polysaccharides.