Tvelve-species of the alqa class Eustigmatophyceae were studied by means of light and electron microscopy, with particular reference to structural aspects of the vegetative cells and the flagellar apparatus of the zoospores. The Vegetative cells are shown to have microfibrils (probably cellulose)' in the cell wall (Vischeria stellata), lamellate vesicles in the cytoplasm of all the species observed and a clear connection between the cfiloroplast endoplasmic reticulum and the nuclear envelope only in representatives of the Monodopsidaceae. Microfibrils (probably cellulose) were also found in the cell wall of the tribophycean species Ophiocytium malus. The most significant results on uni- and biflagellate zoospores include the observation of a Golgi body for the first time in a eustigmatophycean zoospore (Vischeria helvetica) and the first reconstruction of the system of flagellar roots in the Eustigmatophyceae (V. stellata). This consists of a rhizoplast and four microtubular roots: roots R1 (3 MTs) and R2 (2 MTs) originate-at basal body B1 and run anteriorly around the flagellar swelling; root R3 (5 MTs) arises between the basal bodies and runs to the posterior end of the cell; root R4 (2 MTs) originates at basal body B2 and curves around the eyespot. For comparison, zoospores of the tribophycean species Heterococcus marietanii and H. protonematoldes were also studied. A system of flagellar roots consisting of a small rhizoplast and three microtubular roots, two directed anteriorly and one posteriorly was confirmed. A double helix was shown to be typical of the transition region of the flagella in-this genus. The few observations on settling cells shoved the withdrawal of the complete flagellar apparatus including the swelling-and the possibility of reformation of the pyrenold in Vischeria from material stored in the spiral vesicles during the motile stage. In preliminary observations on mitosis and cytokinesis it was found that, at early stages, basal bodies appear near the nuclear surface and the chloroplast and the pyrenoid divide. Cytokinesis seems to occur by a cleavage furrow. My reconstruction of the flagellar root system in Eustigmatophyceae shows sufficient similarities with the flagellar, roots of other heterokont algal and fungal classes to justify its, inclusion with them in a single division,the Heterokontophyta. On the basis of this observation and the main ultrastructural features known for these classes,a phylogeny is, constructed for the whole group and the probable characteristics of the, common ancestor are proposed.

Immunocytochemical analyses have demonstrated that the Calvin cycle enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is predominantly localized in the pyrenoid region of chloroplasts of evolutionarily diverse algae. That Rubisco remains pyrenoid-localized at photosynthetically-saturating irradiance in the green alga Chlorella pyrenoidosa indicates a catalytic, rather than storage function for pyrenoid-localized Rubisco. This is further supported by the immunolocalization of Rubisco activase to the pyrenoids of two species of green algae. The exclusion of phosphoribulokinase from the pyrenoids of a red and a green alga indicates that pyrenoids do not possess the full complement of Calvin cycle enzymes. / Thylakoid lamellae traverse the pyrenoids of many algae. The absence of light-harvesting phycoerythrin and of photosystem (PS) II activity, but not PSI activity, from the intrapyrenoid thylakoids of the red alga Porphyridium cruentum indicates a structural and functional heterogeneity between these lamellae and those located in the chloroplast stroma. In contrast, the intrapyrenoid thylakoids of cryptomonads, algae whose chloroplast is thought to have evolved from red algae, possess both PSI and PSII protein complexes. These results are discussed with reference to Rubisco being mainly pyrenoid-localized in these algae.

No description available.

A study on the process of bud initiation and development in the filamentous brown alga Sphacelaria furcigera (Kutz) was carried out using techniques of light and electron microscopy, as well as cytochemistry. A localized thickening and subsequent protrusion of the outer cell wall of the axial mother cell characterizes the earliest detectable stage of bud initiation. This protrusion forms through the combined deposition of newly synthesized microfibrils together with the partial lysis/loosening of the existing cell wall. Evidence is presented that of the three enzyme activities localized, peroxidase, adenosine triphosphatase and acid phosphatase activity, only peroxidase activity is related to the lysis/loosening of the cell wall during the early development of the bud initial. Continued incorporation of new cell wall material into the outer cell wall maintains its structural integrity. However, there is a change in the layered appearance of the cell wall microfibrils. The cell wall of the bud initial is characterized by two cell wall layers instead of the four found in the pre-existing cell wall of the axial mother cell. This original cell wall is composed of an outer-most fucan layer, overlying an alginate layer, which in turn overlies another fucan layer and finally terminates in an inner-most alginate layer. In contrast the bud initial's cell wall has only a thin outer fucan layer and a thick inner alginate layer. Concomitant with the formation of the cell wall protrusion, there is a loss of cytoplasmic vacuoles, an increase in cytoplasmic mass and density and an increase in the number of organelles. The endomembrane system (endoplasmic reticulum, dictyosomes and the derivative vesicles) also proliferates. Organelle migration into the bud protrusion keeps pace with bud expansion. The movement of the nucleus, however, lags behind and it migrates towards the bud protrusion only after a "vacuole free" cytoplasm becomes established. As the nucleus approaches a medial position between the base of the axial mother cell and the tip of the bud protrusion, cytoplasmic vacuoles re-appear. They are confined, however, to the basal region of the axial mother cell. After karyokinesis, a cross wall is deposited between the two daughter nuclei resulting in the formation of a bud cell and a sister axial cell. The sister axial cell is highly vacuolated and structurally resembles the adjacent quiescent axial cells. The bud cell is dense and non-vacuolated, a feature characteristic of a mefistematic cell. / Science, Faculty of / Botany, Department of / Graduate

No description available.

A comparative study was made between two similar red algal endophytes, Audouinella porphyrae (Drew) Garbary and Audouinella vaga (Drew) Garbary, Hansen et Scagel, (Acrochaetiaceae, Acrochaetiales) and their red algal hosts Porphyra spp. and Pterosiphonia bipinnata, respectively. Both endophytes have axial, stellate chloroplasts with a central pyrenoid and reside in their host's cell walls, producing erect portions outside the host that may bear monosporangia. The endophytes were cultured "free" from their hosts and morphological and cytological features of the free-living forms were compared with field material. Although the two endophytes differ significantly in cell dimensions and branching patterns, the free-living forms do not retain these differences. Cell dimensions, branching patterns and developmental patterns are identical in the two free-living forms. Asexual reproduction with regeneration by monospores was observed. Sexual reproduction was not observed in either endophytic or free-living forms of the endophytes. Free-living forms were used for re-infection and cross-infection experiments. Under all experimental conditions, the endophytes showed only epiphytic growth. The hosts seem to have some effect on both of the endophytes. Epiphytes, Audouinella porphyrae and A. vaga were not selective and grew on both hosts, Porphyra torta and Pterosiphonia bipinnata. Both epiphtyes growing on blades of Porphyra tended to branch and have more extensive prostrate portions (3-5 cells) whereas both epiphytes on Pterosiphoni a bipinnata tend not to branch and have only 1-2 cells in the prostrate portions. Ultrastructural studies of both endophytes showed typical florideophycean features. Ultrastructural features of field material of the two endophytes were similar and free-living, cultured endophytes were similar to field material. A large vacuole was observed in sections of the field material of both prostrate and erect portions whereas this was not observed in cultured material. Based on the results of this study it is proposed that the two endophytes are conspecific. Audouinella vaga is referred to synonymy in Audouinella porphyrae (Drew) Garbary, Hansen et Scagel. / Science, Faculty of / Botany, Department of / Graduate

No description available.