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145. Abstract
Cells of the charophycean alga, Coleochaete
scutata active in cell wall formation were freeze fractured
in the search for cellulose synthesizing complexes (TCs) since
this alga is considered to be among the most advanced and a progenitor
to land plant evolution. We have found a new TC which consists
of two geometrically distinctive particle complexes complementary
to one another in the plasma membrane and occasionally associated
with microfibril impressions. In the E-fracture face is found
a cluster of 8-50 closely packed particles, each with a diameter
of 5-17 nm. Most of these particles are confined within an 80
nm circle. In the P-fracture face is found an 8-fold symmetrical
arrangement of 10 nm particles circumferentially arranged around
a 28 nm central particle. The TCs of C. scutata are quite
distinctive from the rosette/globule TCs of land plants. The
5.5 x 3.1nm microfibril in C. scutata is also distinctive
from the 3.5 x 3.5 nm microfibril typical of land plants. The
phylogenetic implications of this unique TC in land plant evolution
are discussed.
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Last modified 27 October 2005.
This document is maintained by Dr. R. Malcolm Brown, Jr.