Date of Award

2002

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science (Honours)

Faculty

Faculty of Computing, Health and Science

First Supervisor

Mary Boyce

Second Supervisor

Ian Bennett

Abstract

Carbohydrates in P. coriacea leaves were analysed to determine if, when in artificial culture, they were unable to replenish their carbohydrate stores once the seed starch reserve was consumed. While no evidence was found to suggest that this was happening, other findings were made. Soluble carbohydrates determined in P. coriacea were sucrose, fructose, glucose, trehalose, myo-inositol and mannitol. However, mannitol was only found in in situ plants sampled in June. This may be due to high epiphyte coverage elevating plant stress and therefore mannitol levels. P. coriacea grown in tissue culture has soluble carbohydrate levels up to 20-fold higher than plants maintained in aquaria or grown in situ. The average concentration (± I.0 SE) of the soluble carbohydrates in P. coriacea in situ plants were: sucrose 2.54 (0.93) mg g-1 fwt, glucose 0.42 (0.06) mg g-1 fwt, fructose 0.70 (0.05) mg g·-1 fwt, trehalose 0.40 (0.01) mg g-1 fwt, myo-inositol 0.05 (0.00) mg g-1 fwt and mannitol 0.31 mg g-1 fwt. P. coriacea leaves generally had < 40 mg starch g-1 fwt. For the experiment duration there was no significant variation of starch levels except in seawater tissue culture seedlings sampled in August and September, where starch levels were higher. Between environments there was a significant difference in starch levels measured in June, August and September. In June and August the in situ plants had significantly higher starch levels than seawater tissue culture plants, but levels were significantly lower than the seawater tissue culture plants in September. For the analysis of soluble carbohydrates a chromatographic method was developed specifically for highly sensitive detection, plus simplicity for routine analysis. Method development compared a variety of methods used for the extraction, preparation and chromatographic analysis of soluble carbohydrates. An HPLC method employing a polyamine column, acetonitrile/water mobile phase and evaporative light scattering detection, was developed. While this method was simple and robust, detection limits were not low enough to allow analysis of sugars from limited seagrass material of 0.l g for each sample. A GC method was developed for the analysis of soluble carbohydrates in seagrasses maintained in an artificial culture. It consisted of an 80 %ethanol extraction at room temperature, derivatisation of carbohydrates with BSTF A and analysis on a BP-1 column with FID detection. This method was simple, robust and sensitive for the analysis of plant soluble carbohydrates. This method only required 0.1 g of leaf for each sample. The detection limits were 90 mM L-1 fructose, 40 mM L-1 glucose and sucrose, and 20 mM L-1 trehalose, mannitol and myo-inositol.

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