ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Sugars supplied to germinating seedlings of maize (Zea mays L.) regulate the secretion of polysaccharides by the outer cells of the root cap. The polysaccharide secreted by these cells adheres to the root tip as a droplet and the size of the droplet was used to quantitate polysaccharide secretion. The polysaccharide contains glucose, galacrose, and galacturonic acid residues with smaller quantities of mannose, arabinose, xylose, fucose and rhamnose. These sugars supplied to maize seedlings had marked effects on the rate of polysaccharide secretion by root tips. The effects on secretion were independent of the growth rates of the roots. Glucose, fucose and xylose increased droplet size 1.5–2 fold (as did sucrose, maltose, lacrose, fructose and ribose) whereas galactose, arabinose and galacturonic acid were inhibitory. Mannose increased dropler size 5–7 fold.The marked effect of mannose on polysaccharide secretion was due to an increased rate of secretion combined with a longer phase of extrusion of polysaccharide into the forming droplet. The effect of mannose was partially reversed by inorganic phosphate and other sugars (except for fucose which had no effect or promoted secretion in the presence of mannose). In contrast to sucrose, mannose stimulated secretion in a maize variety having a high sugar endosperm (high endogenous sugar). The results suggest that regulation of secretion by mannose is due to an alteration of normal sugar metabolism; whereas stimulation of secretion by sucrose and other sugars may be due to an increased availability of sugars for metabolism.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1973.tb04812.x
Permalink