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Studies on the type species of Compsonema, C. minutum (Fucophyceae, Scytosiphonales); aspects of life history, taxonomic position, shedding of wall elements and plasmodesmata
Author(s) -
Pedersen Poul Møller,
Sokhi Gunwant
Publication year - 1990
Publication title -
nordic journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.333
H-Index - 33
eISSN - 1756-1051
pISSN - 0107-055X
DOI - 10.1111/j.1756-1051.1990.tb02098.x
Subject(s) - pyrenoid , sporangium , biology , plasmodesma , thallus , botany , middle lamella , chloroplast , cell wall , spore , biochemistry , gene
Compsonema minutum , the type species of the genus, shows two features which are characteristic for the Scytosiphonales: the presence of a single large lobed chloroplast per cell with a large pyrenoid in a pyrenoid sac, and a partly parenchymatous prostrate system morphologically similar to the knot filaments in the comparable thallus parts of, for example, Scytosiphon and Petalonia. The genus, therefore, finds a natural position in the Scytosiphonales. The direct type of life history seems to dominate in the reproductive pattern as swarmers from the plurilocular sporangia develop without copulation into plants similar to the parental plant. One unilocular sporangium has been observed but the fate of the swarmers from this reproductive structure has not been determined. The fine structural background for the formation of overlapping wall elements has been investigated. Lacunae develop between the layers in the 2‐layered wall and the outermost part of the wall gradually becomes electron dense. During growth the electron dense part breaks away to become separated from the rest of the wall in the area with lacunae. The plasmodesmata in the transverse walls show a single membrane profile similar to for example Fucus , i.e. the pores provide continuity but lack desmotubules and ER.