Howe, CJ, Beanland, TJ, Larkum, AWD & Lockhart, PJ 1992, 'Plastid Phylogeny and the Problem of Biased Base Composition' in Origins of Plastids, Springer US, pp. 349-353.
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Howe, CJ, Beanland, TJ, Larkum, AWD & Lockhart, PJ 1992, 'Plastid origins', Trends in Ecology & Evolution, vol. 7, no. 11, pp. 378-383.
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Lockhart, PJ, Beanland, TJ, Howe, CJ & Larkum, AW 1992, 'Sequence of Prochloron didemni atpBE and the inference of chloroplast origins.', Proceedings of the National Academy of Sciences, vol. 89, no. 7, pp. 2742-2746.
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The prochlorophytes, oxygenic photosynthetic prokaryotes containing chlorophylls a and b, have been put forward as descended from the organisms that gave rise to chloroplasts of green plants and algae by endosymbiosis, although this has always been controversial. To assess the phylogenetic position of the prochlorophyte Prochloron didemni, we have cloned and sequenced its atpBE genes. Phylogenetic inference under a range of models gives moderate to strong support for a cyanobacterial grouping rather than a chloroplast one. Possible systematic errors in this and previous analyses of prochlorophyte sequences are discussed.
Lockhart, PJ, Howe, CJ, Bryant, DA, Beanland, TJ & Larkum, AWD 1992, 'Substitutional bias confounds inference of cyanelle origins from sequence data', Journal of Molecular Evolution, vol. 34, no. 2, pp. 153-162.
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Available molecular and biochemical data offer conflicting evidence for the origin of the cyanelle of Cyanophora paradoxa. We show that the similarity of cyanelle and green chloroplast sequences is probably a result of these two lineages independently developing the same pattern of directional nucleotide change (substitutional bias). This finding suggests caution should be exercised in the interpretation of nucleotide sequence analyses that appear to favor the view of a common endosymbiont for the cyanelle and chlorophyll- b-containing chloroplasts. The data and approaches needed to resolve the issue of cyanelle origins are discussed. Our findings also have general implications for phylogenetic inference under conditions where the base compositions (compositional bias) of the sequences analyzed differ. © 1992, Springer-Verlag New York Inc. All rights reserved.
Lockhart, PJ, Penny, D, Hendy, MD, Howe, CJ, Beanland, TJ & Larkum, AWD 1992, 'Controversy on chloroplast origins', FEBS Letters, vol. 301, no. 2, pp. 127-131.
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Controversy exists over the origins of photosynthetic organelles in that contradictory trees arise from different sequence, biochemical and ultrastructural data sets. We propose a testable hypothesis which explains this inconsistency as a result of the differing GC contents of sequences. We report that current methods of tree reconstruction tend to group sequences with similar GC contents irrespective of whether the similar GC content is due to common ancestry or is independently acquired, Nuclear encoded sequences (high GC) give different trees from chloroplast encoded sequences (low GC). We find that current data is consistent with the hypothesis of multiple origins for photosynthesis organelles and single origins for each type of light harvesting complex.
Murray, DR & Larkum, AWD 1992, 'Nitrogen content of seeds of Zostera capricorni and Zostera marina', Aquatic Botany, vol. 43, no. 1, pp. 87-91.
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The nitrogen (N) content of mature seeds of Zostera capricorni Aschers, was found by Kjeldahl analysis to be 1.70% of dry matter. The larger seeds of Zostera marina L. were analysed individually by the more sensitive Heraeus procedure. The mean seed N content of these seeds was 1.37% of dry matter (range 1.20-1.56%, standard deviation (SD) 0.13). Seed water contents were similar for both species, 34.7% and 32.3% of seed mass, respectively. The ecological, physiological and evolutionary significance of these observations is discussed. © 1992.
RALPH, PJ, BURCHETT, MD & PULKOWNIK, A 1992, 'DISTRIBUTION OF EXTRACTABLE CARBOHYDRATE RESERVES WITHIN THE RHIZOME OF THE SEAGRASS POSIDONIA-AUSTRALIS HOOK F', AQUATIC BOTANY, vol. 42, no. 4, pp. 385-392.
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Rhizomes of Posidonia australis Hook. f., collected from Botany Bay on the eastern coast of Australia, were analysed for extractable carbohydrates. The concentration of extractable carbohydrate in the stelar tissue of the rhizome was significantly higher
