Thesis (doctoral)--Rijks-Universiteit te Groningen, 1932. / "Extrait du Recueil des travaux botaniques néerlandais, vol. XXIX ) 1932)" "Stellingen" ([2] p.) inserted. Bibliography: p. 367-378.

Patterns of cellulose deposition within the cell wall directly affect the size and shape of plant cells, in turn affecting the overall structure of the plant. In the primary wall of Nitella, and in the walls of many other algae and higher plants, a correspondence has been observed between the organization of cellulose microfibrils and cortical microtubules, each lying on opposite sides of the plasma membrane. The present work examines the development of the secondary wall in maturing Nitella internodal cells in an attempt to determine whether a relationship exists between cellulose microfibril organization and the organization of cortical microtubules. Treatments that artificially rearrange or remove microtubules were used, and effects on cellulose organization in the cell wall were examined through the use of transmission electron microscopy in thin sections and by the replica technique. Removal of microtubules in very young cells had a randomizing effect on cellulose organization, but absence of microtubules or their rearrangement did not prevent the formation of secondary walls with characteristic helicoidal patterns. The findings on the timing of helicoidal development in Nitella and the appearance of the innermost surface of helicoidal layers are discussed in relation to models of helicoidal architecture.

The actin fibrils found at the ectoplasm-endoplasm interface in Nitella internodal cells are a major component of the mechanism that is responsible for cytoplasmic streaming in these giant algal cells. The fibrils have been shown to attach to the inner surface of internodal chloroplasts which are embedded in long files within the stationary ectoplasm along the length of the cell. The existence of actin bundles at the ends of the cell, where chloroplast files are absent, has not been examined. Through the use of scanning and transmission electron microscopy, the present work shows that actin bundles are continuous throughout the cell and that those bundles in the chloroplast-free endwall region have a distinct distribution from those associated with chloroplast files. Additionally, the organization of regenerated actin bundles in blue light-irradiated areas of cells {in which an area of the cell cortex is stripped of its chloroplasts and associated actin fibrils) is compared to untreated regions of the cell. These morphological observations are quantified and discussed in terms of their implications towards the nature of actin bundle immobilization and bundle organization during cell ontogeny.

Mechanical support is a required function of most biological materials. Skeletal helicoids are a structural motif often used in the construction of plant cell walls and arthropod exoskeletons. Nitella axillaris, a giant-celled freshwater alga has many characteristics which make it an ideal subject for helicoidal analysis. Earlier research had shown that the cell wall of mature Nitella internodes exhibit helicoidal layers. However, no previous work had concentrated on studying the relationship between the presence of helicoids and internodal age. The work presented here examines the relationships among growth rate, cell age, cell length, and presence of helicoidal layers. Internodes were categorized according to age, from their position along the shoot. In addition, by monitoring cell growth, the cultures were classified into three groups, slow, medium and fast. Cross sections of the various cells were examined for the presence of helicoidal layers. Once the presence of helicoidal layers was established, oblique, longitudinal and tangential sections were used to further study helicoidal structure. We showed that the transition state between the presence and lack of helicoidal layers is between cells III and IV. The timing of this transition was not exact but more or less coincided with the cessation of cell elongation. Also, no apparent correlation was found between the timing of helicoid deposition and growth rate for cells of equivalent age (internode number}.

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 105-110). Also available via the World Wide Web.

This research is the outcome of investigations of the ability of Nitella congesta, a charophyte, to hyperaccumulate metal contaminants, as well as contribute to the sustainable development of a chain of lakes derived from the sand mine voids at Capel 250km south of Perth, Western Australia. Studies were conducted to ascertain the taxonomy of Nitella congesta as well as its life cycle pattern in relation to the hydrological regime of the lakes of the wetlands. It was observed that a decrease in the availability of water in the lakes particularly on the onset of summer, initiated the production of fruiting bodies whiles prolonged availability of water ensured a prolonged vegetative growth. / Aquatic plants play an important role in the structuring of freshwater communities. Freshwater macrophytes such as Nitella congesta have been reported to serve as food source as well as provide refuge and shelter for macroinvertebrates. Thus the presence of freshwater macrophytes in one way or the other has a direct impact on the species abundance and diversity of macroinvertebrates that use them as their habitat. A study of the impact of Nitella congesta as a suitable macrophyte on diversity and abundance of macroinvertebrates showed a positive outcome. It was observed that species richness and diversity were high in Nitella congesta dominated sites of the lakes. Experimental outcome showed that Nitella congesta is a hyperaccumulator of metals. Both the mucilage and the thallus displayed concentrations of few metals. / The disappearance of submerged macrophytes such as charophytes in shallow lakes is a major problem caused by eutrophication. There has been an approved proposal to discharge treated waste water with a phosphorus concentration of about 4,000μg/L into the lakes of the Capel Wetlands Centre. This necessitated a study of the impact of eutrophication on the establishment of Nitella congesta as a functional macrophyte for the enhancement of the ecological structure of the wetlands. / Results showed that though eutrophication will initially increase the primary productivity of the lakes of the wetlands, the eventual consequence will be the loss of Nitella congesta as a functional macrophyte in the wetlands. / At the last stage of the study, a consistent decrease in pH readings of the lakes and lack of successful germination of Nitella congesta as a result of prolonged drought and exposure of the lake sediment was observed. This necessitated a thorough study of the impact of climate change on the establishment of Nitella congesta in the wetlands. In conclusion, it was observed that Nitella congesta could serve as a suitable tool for the rehabilitation of the wetlands.

Submitted by RODOLFO JOSÉ TÓFOLI null (rodolfo_tofoli@hotmail.com) on 2017-04-27T16:00:45Z No. of bitstreams: 1 DISSERTAÇÃO VERSAO FINAL.pdf: 1411835 bytes, checksum: 522077674c28c7cf92bf9e1eaf83b999 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-03T14:38:01Z (GMT) No. of bitstreams: 1 tofoli_rj_me_assis.pdf: 1411835 bytes, checksum: 522077674c28c7cf92bf9e1eaf83b999 (MD5) / Made available in DSpace on 2017-05-03T14:38:01Z (GMT). No. of bitstreams: 1 tofoli_rj_me_assis.pdf: 1411835 bytes, checksum: 522077674c28c7cf92bf9e1eaf83b999 (MD5) Previous issue date: 2017-03-09 / No Brasil, há uma grande biodiversidade de espécies de algas lóticas, Dentre as mais conhecida, encontradas em rios e riachos da região sudeste do estado de São Paulo destaca-se a Oedogonium sp. e a Nitella microcarpa var. wrightii., dois gêneros de algas verdes. Entretanto, estudos de caracterização química de extratos destas algas ainda são inexistentes. Por esse motivo destaca-se a importância deste trabalho, o qual encontra-se subdivido em dois estudos. O primeiro teve por objetivo avaliar e quantificar compostos fenólicos e capacidade antioxidade de extratos de diferentes solventes da alga Oedogonium sp. Utilizou-se um delineamento experimental de mistura para determinar a influência dos solventes e verificou-se qual desses apresentou melhor rendimento na extração desses compostos da alga em pó. O segundo estudo teve por objetivo realizar a caracterização de duas macroalgas verdes: Nitella microcarpa var. wrightii, e Oedogonium sp., através da obtenção de um extrato, com o melhor sistema de solventes obtidos no primeiro estudo. Desta forma, foi possível quantificar quanto a presença de minerais, flavonoides, umidade, carotenoides, compostos fenólicos e capacidade antioxidante. No primeiro estudo, os resultados sugeriram que a mistura acetona-etanol apresentou melhor rendimento de extração tanto para compostos fenólicos como à capacidade antioxidante. No segundo estudo, a alga Oedogonium sp. destacou-se por apresentar uma grande quantidade de carotenoides totais. Já a espécie Nitella microcarpa var. wrightii, obteve altos valores de minerais. / In Brazil, there is a great biodiversity of lotic algae species. Among the most well known species found in rivers and streams in the southeast region of the state of São Paulo is Oedogonium sp. and Nitella microcarpa var. Wrightii., Two genus of green algae. However, studies of chemical characterization of extracts of these algae are still non existent. For this reason the importance of this work is highlighted, which is subdivided in two studies. The first one had the objective to evaluate and quantify phenolic compounds and antioxidant capacity of extracts of different solvents of the algae Oedogonium sp. An experimental design of the mixture was used to determine the influence of the solvents and it was verified which of them presented better yield in the extraction of these compounds from the powdered seaweed. The second study aimed to characterize two green macroalgae: Nitella microcarpa var. Wrightii, and Oedogonium sp., by obtaining an extract, with the best solvent system obtained in the first study. In this way, it was possible to quantify the presence of minerals, flavonoids, moisture, carotenoids, phenolic compounds and antioxidant capacity. In the first study, the results suggested that the acetone-ethanol-water mixture had a better extraction yield for both phenolic compounds and antioxidant capacity. In the second study, the alga Oedogonium sp. was characterized by a large amount of total carotenoids. The other alga, of the species Nitella microcarpa var. Wrightii, has achieved high mineral values.