Developmental morphology of a Polysiphonia species (Ceramiales, Rhodophyta) in a culture experiment
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概要
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The morphological development and life history of a Polysiphonia species (Ceramiales, Rhodophyta) were investigated by culture experiment. This alga was reported as Polysiphonia urceolata f. lepadicola by Segi in 1951. Morphological stability and plasticity were assessed in several features, which have been adopted as taxonomic criteria for the genus Polysiphonia. The following features are confirmed as morphological stability in this alga: (1) Thallus is composed of slender upright axes, and intricately entangled prostrate axes; (2) Thallus is soft and flaccid in texture; (3) Thallus produces adventitious branches on the lowermost portion of the main axis in the early stage, and also on the upper portion of upright axes in the late stage; (4) Thallus is ecorticated with four periaxial cells; (5) Rhizoids are formed without septation; (6) Determinate branches have sharply pointed apices; (7) Endogenous axillary branchlets are formed; (8) Vegetative trichoblasts are rarely formed; (9) Carpogonial branch is composed of four cells; (10) Spermatangial branchlets are formed replacing the whole trichoblasts, they are terete to cylindrical in shape with sterile tips; (11) Tetrasporangia are formed in a straight line, on the last two orders of ordinary branchlets and on axillary branchlets. These features are appropriate taxonomic criteria. The external appearance of individual plants, length/diameter ratios of segments showed phenotypic variation according to the growth stage, temperatures and photoregimes.
- 札幌大学の論文
- 2006-03-30