PLANT PHYSIOLOGY , Vol 113, Issue 1 103-109, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Effect of Xyloglucan Oligosaccharides on Growth, Viscoelastic Properties, and Long-Term Extension of Pea Shoots
A. Cutillas-Iturralde and E. P. Lorences
Unidad Docente Fisiologia Vegetal, Facultad Ciencias Biologicas, Universidad de Valencia, Doctor Moliner 50, 46100 Burjassot, Valencia, Spain
The growth-promoting effect of xyloglucan-derived oligosaccharides was
investigated using a bioassay with entire pea (Pisum sativum L., var
Alaska) shoots. After a 24-h incubation period at 25[deg]C, xyloglucan
oligosaccharide (XGO) solutions with concentrations of 10-6 M notably
increased the growth rate of pea shoots, whereas the same oligosaccharides
at 10-7 M were less effective. To investigate the possible correlation
between growth rate changes in the XGO-treated shoots and changes in the
wall mechanical properties of their growing regions (third internodes), we
used a short-term creep assay. The promotion of elongation by XGOs was
reflected in an enhancement of the viscoelasticity of the growing regions
of the shoots. To show whether this effect on wall viscoelastic properties
was the cause or a consequence of their growth promotion, we tested the
effect of XGOs on the long-term extension of isolated cell walls. We
characterized an acid-induced extension in isolated cell walls from pea
shoots that was not inhibited by preincubation in neutral buffers.
Exogenously added XGOs did not alter the pattern of pea segment extension
at any pH tested, indicating that XGOs have no direct effect on cell wall
viscoelasticity. Finally, preincubation of pea segments in neutral buffers
with XGOs enhanced their capacity to extend under acidic conditions. This
finding suggests that XGOs at a neutral pH can act via transglycosylation,
weakening the wall matrix and making the wall more responsive to other
mechanisms of acid-induced extension as an expansin-mediated extension.
