University of Tasmania
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Aspects of leaf and extract production from Tasmannia lanceolata

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posted on 2023-05-27, 18:23 authored by Read, CD
This thesis examines several aspects of the preparation, extraction and analysis of solvent soluble compounds from leaf material of Tasmannia lanceolata and reports a preliminary survey of extracts of some members of the natural population of the species in Tasmania. A major constituent of these extracts, polygodial, was shown to be stored within specialised idioblastic structures scattered throughout the mesophyll, and characterised by distinctive size and shape, and a thickened wall. The contents of these cells were sampled directly, analysed and compared with the composition of extracts derived from ground, dry whole leaf. This result was supported by spectroscopic analysis of undisturbed oil cells in whole leaf tissue. In a two year field trial, the progressive accumulation of a number of leaf extract constituents (linalool, cubebene, caryophyllene, germacrene D, bicyclogermacrene, cadina-1,4 - diene, aristolone and polygodial) during the growth flush was followed by a slow decline during the subsequent dormant season. These results were interpreted in relation to leaf dry matter accumulation, in order to propose a harvest period within which leaf material will produce consistent composition of extract. Under four levels of irradiance in a growth cabinet experiment the plant exhibited many characteristics of a 'shade' species, in particular, a limited ability to acclimate to high light levels. Assimilation rates were highest at 150˜í¬¿mol m-2s-l while elevated respiration rates and a reduced quantum yield occurred at a higher light level. Maximum assimilation rates in leaves grown at 150˜í¬¿mol m-2s-l were obtained at around 250˜í¬¿mol m-2s-l. Optimum net assimilation rate was obtained from 18-25¬¨‚àûC. The effect of level of irradiance on the proportion of extractable compounds in the leaf, chlorophyll levels, specific leaf area, leaf thickness and percentage dry matter in the leaf are reported and discussed in relation to a probable production system in which the new canopy is largely removed at the end of each growth cycle. The ontogenetic patterns determining canopy architecture were observed in the field, and used, with support from the results of a trial pruning of mature trees, to discuss the likely outcome of various harvest methods. These results are combined to suggest a production strategy for maximum yield of leaf extract of consistent composition. The strategy proposes harvesting in late summer, after new leaf has achieved full maturity and may enable full canopy recovery in the subsequent growing season.


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Copyright 1995 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Library has additional copy on microfiche. Thesis (Ph.D.)--University of Tasmania, 1997. Includes bibliographical references

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