ISHS Acta Horticulturae 615: IV International Conifer Conference
TAXUS SPECIES - MORPHOLOGICAL AND CHEMICAL VARIATIONS IN NEEDLES AND SEEDS |
| Authors: | D. Dempsey, C. O’Flaherty, I. Hook |
| Keywords: | cuticular n-alkanes, fatty acids, fixed oil, leaf sizes, paclitaxel, seeds, stomatal numbers, Yew species |
| Abstract:
To allow more accurate identification of Taxus species, a number of morphological and chemical characteristics of needles and seeds were examined. Macro- and microscopical foliar characteristics of Taxus baccata, T. canadensis, T. celebica, T. cuspidata, T. x hunnewelliana and T. x media were examined. All mean needle lengths fell within the recognised T. baccata range (14 to 34 mm), except T. baccata ‘Adpressa’ and T. baccata ‘Compacta’ (8 mm). Mean stomatal pore lengths for the genus Taxus were 14.26 µm. Stomatal numbers per mm2 of lower epidermis averaged 99.9 for Taxus, with 122.8 for T. canadensis and 82.3 for T. baccata ‘Neidpathensis’. Foliar paclitaxel content showed significant inter- and intra-specific variations, ranging from 20 mg/kg (0.002%) in T. baccata ‘Adpressa Aurea’ to 250 mg/kg (0.025%) in T. brevifolia (= T. baccata ‘Brevifolia’). The average for T. baccata was 90 mg/kg (0.009%). The predominant n-alkanes in all needle epicuticular waxes were C31 (19-35%) and C33 (7-18%). Only the sample collected as T. celebica differed, containing equal amounts (7%) of both these n-alkanes. Seed dimensions showed variability depending on sources and questioned identities. Fixed oil contents and fatty acid profiles were determined for four Taxus species (T. baccata, T. chinensis, T. cuspidata and T. mairei). These showed similarities, having oleic and linoleic acids as major constituents, with significant amounts of the delta 5-olefinic acid taxoleic acid (8.4-16.6%) | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
