18. Brown, Jr. R. M. 1969. Observations
on the relationship of the Golgi apparatus to wall formation in
the marine chrysophycean alga, Pleurochrysis scherffelii.
J. Cell Biol. 41:109-123.
18. Abstract
The role of the Golgi apparatus in wall
formation of vegetative cells of a marine chrysophyte, Pleurochrysis
scherffelii, is described. Wall fragments are synthesized
within the cisternae of the Golgi apparatus. A single Golgi apparatus
is always located at the cell periphery, and the distended cisternae
are oriented toward the cell surface. A highly-ordered body found
near the inflated cisternae is associated with spherical, membrane-bounded
bodies which may be involved in the progressive degeneration of
cisternal membranes which release wall fragments. Protoplast
movement has been detected by time-lapse cine-photomicrography
and is correlated at the ultrastructural level with change in
positions of the Golgi cisternae. Wall-synthesizing capacity
is greatest during transverse wall formation. Senescent cells
lack a Golgi apparatus with inflated cisternae. In addition,
wall fragments are not present in the Golgi cisternae at this
stage. Zoosporogenesis results in a temporary loss of the wall-forming
capacity of the Golgi apparatus; this activity then resumes with
the formation of a different morphological entity, the scale.
Preliminary quantitative measurements of the turnover capacity
of the Golgi apparatus have been made. From these data it has
been determined that between 41 and 82 Golgi generations are required
to synthesize the cell wall of an actively growing cell; this
estimate indicates that approximately one cisterna is produced
every 2 min, provided the cell generation time is 3 days. The
time-lapse cinephotomicrographic data confirm that the rate of
production of Golgi cisternae is at least one cisterna every 2
min.