PLANT PHYSIOLOGY , Vol 106, Issue 2 755-761, Copyright © 1994 by American Society of Plant Biologists
|
DEVELOPMENT AND GROWTH REGULATION |
Differential Changes in Size Distribution of Xyloglucan in the Cell Walls of Gravitropically Responding Pisum sativum Epicotyls
L. D. Talbott and B. G. Pickard
Biology Department, Washington University, St. Louis, Missouri 63130
Growth-related change in the size distribution of hemicellulosic wall
polymers during the gravitropic curvature response of intact pea (Pisum
sativum L. cv Alaska) epicotyls was examined by gelfiltration
chromatography. The gravitropic response was characterized by the
appearance of curvature 20 to 30 min after horizontal placement, with
35[deg] of curvature attained by 80 min. Correlated with the onset of
curvature, on the upper side of the epicotyl, there was a conspicuous
transient increase in the abundance of relatively large hemicellulosic
xyloglucan polymers, similar to increases previously found under conditions
where diminished wall extensibility was expected. On the lower side there
was a moderate, slower, and longer-term increase in abundance of small
xyloglucan, similar to changes previously found in connection with
auxin-stimulated growth responses. Both shifts occurred primarily in the
epidermis. They appear to represent two coordinated physiological
mechanisms contributing to differential growth.
