The solvent extract of Tasmannia lanceolata from a small community of plants was examined over 230 days of the growing season. The results from gas chromatography were analyzed using cluster analysis and principal coordinate analysis. Two distinct groups of plants were identified, based on polygodial content and the entire range of components detected. The use of as many components as possible is recommended for the analysis, to give the most complete representation of the composition of the extracts. Within the low-polygodial group, the tendency was for polygodial levels to remain constant over time, whereas in the high-polygodial group, concentrations varied. Keywords: Cluster analysis; Tasmannia lanceolata; polygodial; gas chromatography

Fruit set is a key component of essential oil yield from fennel (Foeniculum vulgare Mill.) under Tasmanian conditions. Fruit set in commercial crops is often low, possibly due to incomplete pollination. Fennel flowers are strongly protandrous and a series of flowers must be produced to ensure pollination. The hypothesis tested was that decreasing stand density increases the number of lateral branches, thereby increasing the number of higher order umbels and thus increasing the overlap between the periods of pollen production and stigma receptivity. A field trial was used to examine the number of umbels of each order produced under stand densities of 4, 12, 25, 50 and 100 plants/m2. Stand density influenced the ratio of pollen producing to pollen receptive umbels and stand densities of 50 and 100 plants/m2 showed a distinct imbalance between pollen production and stigma receptivity. The data collected supported the hypothesis and it is probable that, in commercial crops, fruit set is being reduced by a lack of synchrony between pollen production and stigma receptivity. The highest stand density tested reduced total oil production. We therefore recommend the inclusion of low stand-density strips within standard-density commercial crops.

Fennel (Foeniculum vulgare Mill.) is grown commercially in Tasmania for the production of a steam-distilled essential oil, which is high in trans-anethole. Often, only the generative canopy is harvested since this contains the bulk of the oil and further this oil is higher in anethole than oil from other parts of the plant. Regardless of whether the whole crop is forage harvested or the generative canopy alone is removed using a combine-harvester, the most efficient oil production occurs when the greatest proportion of the canopy is generative, giving maximum oil yield from a minimum of fresh weight to be processed. A trial was conducted to examine the relationship between stand density and the various yield components of fennel in order to predict the likely effect on yield of increasing stem density as the short term perennial crop matures. As for most crops, planting density and biomass yield are closely related and the optimum planting density was predicted using a mathematical model. The results suggest that an initial stand density of 10 to 12 plants/m2, in a square layout, would produce the greatest yield of essential oil per unit area by maximising the production of the generative canopy. This density also maximises the yield of oil relative to the weight of material to be distilled.

No abstract

No abstract