Laminaria sinclairii (Harvey) Farlow, Anderson and Eaton, found from Southern California to Central British Columbia, and L. longipes Bory, found from Southeast Alaska to the Kurile Islands, differ in several ways from most other kelp plants. Their most distinctive feature is the rhizome-like holdfast, composed of many haptera, from which arise multiple stipes, each bearing a single blade. The two species are very similar to each other and have been distinguished in the past primarily by the presence of mucilage ducts in the stipe of L. sinclairii and the absence of these in the stipe of L. longipes. In order to determine whether the two species are indeed distinct, their distribution, ecology, growth, and reproduction were studied in the laboratory and on beaches in Alaska, British Columbia, and Oregon. The gross distribution of both species appears to be controlled by temperature. Transplants and laboratory cultures indicate that L. longipes is adapted to lower temperatures than L. sinclairii. Salinity apparently has little influence on distribution, as both species tolerate wide ranges of salinity. L. sinclairii was studied in situ on three beaches in Northern Oregon, where the plants are subjected to heavy surf. The sand level on the beaches rises through the summer so that the plants are partly or wholly buried under sand by late summer. The first heavy storms in the fall remove most of the sand. Maximum growth occurs in early summer, prior to burial. The blades are lost in December and new ones are regenerated in January. Ripe sori are produced on the old blades just before they are lost and on the new blades just after they appear. There is little evidence from either field or laboratory studies to indicate that the gametophytes which develop from the spores in these sori normally produce sporophytes. Sexual reproduction of this type is difficult because of the scouring action of the sand. In March and April there is considerable production of new stipes and blades from the haptera at the margins of the holdfast. This vegetative proliferation is apparently the normal method of reproduction. L. longipes was observed in situ in Alaska on only five occasions. Growth is greatest in summer and sori are produced in December. Laboratory cultures indicate that sexual reproduction is very rare in this species. L. longipes is rarely associated with sand. Transplants and laboratory cultures indicate that production of mucilage ducts in the stipes of the two species is not affected by changes in environmental conditions. Comparison of the two species shows they differ in several other points besides mucilage ducts, including length of stipes, width of blades, winter loss of blades, morphology of gametophytes, and habitat. The evidence confirms that they should be retained as two separate species. / Science, Faculty of / Botany, Department of / Graduate

This thesis describes a series of experiments, firstly into mammalian arsenic urinary metabolites and secondly into the use of phospholipase enzymes as a tool to assist in the characterisation of lipids extracted from the seaweed, <i>Laminaria digitata</i>. HPLC-ICP-MS has been used as the principal analytical instrument, often coupled with ES-MS. The ICP-MS. Provides a ‘hard’ ionisation process and yields data specific to arsenic. ES-MS (electrospray mass spectrometry) is a ‘soft’ ionisation technique that allows analysis of the intact molecules. Analysis of the urine from Scottish Blackface sheep that had been the subjects of a feeding trial in which the sheep routinely ate <i>Laminaria</i> <i>digitata</i> as part of their normal diet revealed the presence of the short chain fatty acids, dimethylarsenopropionic acid and dimethylarsenobutanoic acid. These had previously only been seen in the urine of human volunteers following ingestion of cod liver oil. Further controlled feeding trial experiments were performed in which cod liver oil, <i>Laminaria digitata</i> and aqueous extract of <i>Laminaria digitata</i> was ingested by human volunteers. Similarities and differences in the arsenic urinary metabolites resulting from the different feeding trial regimes were investigated. The continual presence of arsenobetaine in the urine produced by the volunteers, including the control samples, raised questions concerning the accepted retention time of arsenobetaine in the body that were answered by performing another feeding trial, the results of which have been published. Phospholipase D, C, and A2 were used to cleave arsenic containing phospholipids extracted from freeze dried <i>Laminaria digitata</i>. Some valuable information was gained and the technique shows great promise for future study.

Graduation date: 1994

The machair of the Outer Hebrides, Scotland, is a cultural landscape, designated as a Site of Special Scientific Interest. Crofting on the machair is a sustainable low-input, low-output system, producing crops for livestock fodder, which has been practiced for hundreds of years. Recent demographic changes have affected the agricultural practices, with unknown, but potentially negative effects on these marginal soils. The present work investigated the effects of some of these changes in agricultural practices, in particular the effect of amendment with kelp (Laminaria digitata), a brown seaweed, ploughing and land use on soil stability, water repellency and soil microbiology. Furthermore, the effect of kelp on plant seed germination and root development was assessed. The results showed that machair soil is resilient towards amendment with kelp and synthetic NPK fertilizer in a single growing season, and that this resilience was not caused by rapid degradation of kelp. There was evidence that kelp inhibits soil fungi, but increases total microbial biomass and activity. The soil was slightly to severely water repellent. The causes of this repellency could be attributed to a number of factors including plant organic matter, manure, land use and organic matter within aggregates. Kelp increased seed germination in a number of key native machair plants and crops, suggesting that kelp may affect native plant community composition and crop yield. Also, a promoting effect on root development of kelp was seen in some plant species, with a threshold concentration above which it became inhibiting. Furthermore, these results confirmed the presence of plant growth regulators in kelp. The above findings are relevant not only to the machair, but also to other marginal sandy soils, and to the use of seaweed species as organic alternatives to conventional synthetic fertilizers.

Graduation date: 1999

No description available.

Graduation date: 1999

Graduation date: 1997

Graduation date: 1995

Graduation date: 1994