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Review: morphological, cytological and embryological characters and phylogeny inferred from cladistic analysis of the marine red algal genus Porphyra
Yamazaki, S.; Shimomura, K.; Saga, N. (1999). Review: morphological, cytological and embryological characters and phylogeny inferred from cladistic analysis of the marine red algal genus Porphyra. Bull. Inst. Oceanic Res. & Develop., Tokai Univ. 20: 197-209
In: Bulletin of Institute of Oceanic Research and Development. Tokai University. Tokai University. Institute of Oceanic Research and Development: Shimizu. ISSN 0289-680X
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| Auteurs | | Top |
- Yamazaki, S.
- Shimomura, K.
- Saga, N.
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| Abstract |
In this paper, we review the morphological, cytological, embryological and other characteristics of the genus Porphyra, focusing on their cladistic analysis. Using a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a biochemical approach, a cytological survey of the vegetative cells of the gametophytic and sporophytic phases in Porphyra showed that two stages differ in a number of structural characterisics: form and growth (diffuse vs apical), chloroplast number (one vs many), pit plug (absent vs present), vacuole (peripheral vs central) and cell wall structure (xylan vs cellulose). Though variation in the form and structure of vegetative and reproductive cells in the sporophytic phase of different species has received little attention to date, the aforementioned characteristics of sporophytic thallus may be of significance in Porphyra taxonomy. The development and ultrastructure of the spermatia of this genus have been recently confirmed. Large fibrous vesicles appeared in mature spermatangia. Most spermatia did not possess floridean starch grains. It has also been confirmed that spermatia became attached to prototrichogynes which were derived from carpogonia, followed by the transfer of the contents of spermatia via a fertilization canal to the prototrichogynes.Various characteristics have evolutionary importance implied in this taxonomic arrangement. To establish natural taxonomic systems, it essential to understand phylogenetic relationship among the given groups of organisms. The cladistic methodology (grouping taxa according to shared synapomorphies) provides a sound logical framework for constructing phylogenetic relationships between organisms. However, as far as we know, phylogenetic relationships within the genus Porphyra have not been deduced by cladistic analysis based on morphological, cytological and physiological data. In the present review we discuss the phylogeny and evolution of this genus on the basis of the cladistic analysis of morphological, cytological and physiological data.The results indicate that the consensus tree divides into two groups, one of which is further divided into four groups. In addition, the present analysis suggests that the subgenera Porphyra, Diplastidia and Diploderma were not monophyletic groups and that these groups and that these subgenera may be unnatural taxonomic groups. If we were to attempt a classification of the genus Porphyra at a subgenera level, we would propose the following taxonomic system: two subgenera one (tentatively named "Secretum") in which the characteristics of the arrangement of the reproductive cells is of the sectored type and the other (tentatively named "Mistro") in which the characteristics of the arrangement of the reproductive cells is of the mixed type. Since phylogenetic relationships within the genus Pophyra were not clearly resolved in the present analysis, the accumulation of further data will be required for the clarification of phylogenetic relationships within this genus. |
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