61. Westafer, J. M. and R. M. Brown, Jr.
1976. Electron microscopy of the cotton fiber: new observations
on cell wall formation. Cytobios. 15:111-138.
The ultrastructure of the cotton fiber was
examined after developing successful fixation methods. Fiber
cells were fixed at different stages of development. In cells
which were elongating and producing primary cell walls, the Golgi
apparatus appeared to be directly involved in secretion and synthesis
of primary wall components. In cells which were synthesizing
thick secondary cell walls, evidence suggested a major role for
the endoplasmic reticulum and plasma membrane in the synthesis
and secretion of secondary wall materials. The possibility of
a shift from a Golgi apparatus pathway for primary wall synthesis
to an endoplasmic reticulum pathway for secondary wall synthesis
is discussed. Plasma membrane micro-invaginations are present
only during secondary wall synthesis and may represent sites of
cellulose assembly. A model for primary wall biogenesis via the
Golgi apparatuses is presented, and the potential of the cotton
fiber as a model system for studying cellulose biogenesis in higher
plants is discussed.