The Golgi apparatus in diploid sporogenesis of a red algae

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The Golgi apparatus in diploid sporogenesis of a red algae
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The Golgi apparatus in diploid sporogenesis of a red algae, Gracilaria
mammillaris
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Z.L. Bouzon’ and E. C. Oliveira2
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1.Departamento de Biologia Celular, CCB, UFSC, Florianopolis - SC 88040-900, Brazil.
E-mail: [email protected]
2.Departamento de Bot%ka, IB, USP, S&oPaulo - 05422-970, %o Paul0
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The genus Gracilaria (Rhodophyta, Gracilariales) nowadays the main source of
agar in the word, has been the subject of many publications [l]. Nevertheless, only a few deal
with ultrastructure, and less so with sporogenesis. Here we describe morphological change
observed with the Golgi apparatus during the process of carposporogenesis.
Three stages are easily distinguished in the process of maturation of carpospores in
what concerns the Golgi apparatus: 1. in young cells, that will differentiate into carpospores,
the Golgi apparatus consists of a few dictyosomes scattered in the cytoplasm; the dictyosomes
have 3-5 cisterns and some vesicles associated with the maturation
face and the
mitochondrion
at the formation face, suggestive of metabolic interactions among these
organelles; 2. as maturation takes place the dictyosomes increase considerably in number and
size, presenting lo-12 cisterns and intense production of vesicles; in some dictyosomes fibrilar
vesicles produced from the maturation face seem to be related to the initial deposition of
carpospore cell-wall; the association of dictyosomes with starch grain production is also
hypothesis suggested by some micrographics (Fig. 1); 3. An intense dictyosome activity is
observed at the final stage of maturation of carpospores. At this stage the dictyosome enlarge
considerably and migrate to the periphery of the cell; the expanded cisterns at the maturation
face become semi-circular and begin the production of vesicles with an electron-transparent
matrix and electron-dense center; these vesicles fuse and give rise to the cored vesicles (Fig.
2); at the completion of the maturation process, a large number of cored vesicles are seen at
the cell periphery and the dictyosomic activity ceases. A comparison of our observation will
be made with available data in the literature [2].
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References
1. Oliveira, E. C. 1984. Taxonomic criteria in the genus Gracilaria Grev. (Rhodophyta): an experience
with the Western Atlantic species. Proc. I&. Seaseed Symp. II: 55-58.
2. ‘Tsekos, I. 1985. The system of differentiation carposporangia
in secretion
tenuissima: occurrence
and participation
proteinaceous substances. Protoplama, 29: 127-36.
in the red alga Chondria
of polysaccharidic
and
FIG. 1. Hypertrophied dictyosome producing inflated cisterns of nearly mature
carpospore. Scale bar =I pm.
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FIG. 2. Dictyosome of an older carpospore prior to spore liberation, producing
cored vesicles. Scale bar = lpm.

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