Biology Reference
In-Depth Information
CHAPTER
6
Cellular
Morphogenesis i
n Plants
The development of multicellular animals makes much use of animal cells' ability to move
and to exchange neighbours. Plant cells cannot move, so a change in the shape of a plant tissue
bears a very direct relationship to changes in the shapes of its constituent cells (Chapter 4).
Serious technical problems inherent in plant cell biology, chiefly problems of access, mean
that the study of plant cell morphogenesis has lagged behind that of animal cells, although it
is now catching up very quickly. It is therefore not yet possible to describe morphogenetic
systems in the samedetail that is available for animal cells, andbecause of this, it ismore difficult
to step back from the details to recognize emerging principles. Nevertheless, the importance of
cell morphogenesis to plant development makes it worth devoting a chapter of this topic to
some of the systems that have been studied most closely. They reveal some surprising similar-
ities between plant and animal morphogenesis but also stress some important differences.
Plant cells differ from those of animals in many respects, but the most important difference
from the point of view of morphogenesis is that a plant cell is surrounded by a rigid cell wall
(
Figure 6.1
). This wall is made mainly from cellulose, with hemicellulose and pectin also
being present in significant quantities. Cellulose, a polymer of glucose containing
500
e
15,000 glucose monomers, forms quasi-crystalline bundles of about 70 cellulose chains
to produce cellulose microfibrils. These tend to be laid down in flat, parallel arrays, in which
FIGURE 6.1
The structure of a generalized plant cell and the main components of its cell wall.
