When [glucitol-H-3]XXFGol (a (NaBH4)-H-3-reduced xyloglucan nonasaccharide) was applied to excised shoots of pea (Pisum sativum L. cv. Progress) at the base of the epicotyl, it inhibited growth in the elongation zone, 4-5 cm distal. Experiments were conducted to discover whether such H-3-oligosaccharides are translocated intact over this distance, or whether an intercellular second messenger would have to be postulated. After 24 h, H-3 from [glucitol-H-3]XXFGol and [glucitol-H-3]XXXGol showed U-shaped distributions, with most H-3 at the base and apex of the Radioactivity from [fucosyl-H-3]XXFGol and [xylo-syl-H-3]XXFG also moved acropetally, but did not concentrate at the apex, possibly owing to removal from the transpiration stream of fucose and xylose formed by partial hydrolysis of XXFG en route. When 10(-7) M [glucitol-H-3]XXFGol was supplied, about 14 fmol . seedling(-1) of apparently intact [H-3]XXFGol was extractable from the elongation zone after 24 h, Larger amounts of degradation products were extractable (including free [H-3]glucitol) and some wall-bound PI-hemicellulose was present (presumably formed by the oligosaccharides acting as acceptor substrates for transglycosylation). We conclude that biologically active oligosaccharides of xyloglucan can move through the stem acropetally and that they are maintained at low steady-state concentrations by both hydrolysis and transglycosylation.
|Number of pages||8|
|Publication status||Published - Jan 1998|