Aspects of developing Tasmannia lanceolata for commercial extract production

Essential oils crops offer high value, low volume end products for export. Tasmannia lanceolata is currently commercially utilised for its plant extract on a small scale, but the consistency of yield and quality potentially offered by plantation production of the species has the capacity to significantly increase the size of the industry. Early attempts at small scale plantation production highlighted the need to understand the ecophysiology of the species. Climatic and nutritional effects on the growth and plant extract yield and quality of the species were investigated in both glasshouse and field trial conditions. Experiments were conducted on growth responses to manipulated levels of light, temperature, wind and nutrients (with separate experiments focusing specifically on the macronutrients N, P and K and fertiliser rate respectively). Further investigations described the pollen structure of T. lanceolata, as well as vectors that may aid in pollination. Temperature and light levels were manipulated in growth cabinets to determine optimal rates of photosynthesis, and stomatal effects. High light levels and temperatures up to 25°C, positively affected photosynthetic rate. At 25°C, photosynthetic rate significantly declined and stomatal conductance significantly increased. A wind tunnel was used to test plant photosynthesis, stomatal conductance and plant water potential over three different wind speed treatments (16, 28 and 43 km/h). Photosynthetic rate declined at higher wind speeds, while stomatal conductance and plant water potential increased at higher wind speeds, while plants were kept at a constant temperature (20°C). Two field trials with three mulch treatments (bare soil, organic mulch and plastic mulch) and two shelter treatments (with and without tree guards) were applied at two sites. Tree guards increased height and stem circumference after 12 months at both sites on all mulch treatments. Plastic matting and organic mulching increased plant height at one site, while organic mulch significantly increased height of plants over bare soil at the other site. Photosynthetic rates of plants were increased by tree guards under both low and high ambient light conditions. Yield of the most important plant extract component, polygodial, was unaffected by tree guards. Three levels of N, P and K were applied to potted plants in a glasshouse over a 10 month period. The highest application level of N (20mM) achieved the most growth, with considerably increased plant height, leaf number and stem circumference, along with greater yields of polygodial as a percentage of dry matter. Higher rates of N together with lower rates of P produced particularly strong growth. No advances in growth were achieved above the medium level applications of K (6mM) and P (1mM), and oil yield was significantly lowered at the highest treatment levels of both K (12mM) and P (2mM). Five levels of Osmocote Plus Trace Elements were applied to glasshouse grown plants to better understand the effects of total nutrient levels, including nutrients other than N, P and K. Plant height, leaf number and stem width were all affected by fertiliser treatments, with greatest plant height at the highest fertiliser rate but not greatest leaf number or stem width. The lowest fertiliser rate produced a significantly higher extract yield than higher fertiliser treatments, but significantly lower plant growth. Polygodial yield as a proportion of oil yield was unaffected by fertiliser rate. Plant pollen was analysed and pollination was examined in the species. Although a single pollen grain was identified on the leg of a muscoid fly, no positive identification was made that this represented the main pollination vector. Gas chromatography of male and female flower samples indicated very strong similarities between the two, however no compounds were identified that could lead to positive determination of suitable pollination vectors based on known pheromone preferences. Insect traps were laid out in the field to look specifically at the role of native bees in the pollination of T. lanceolata, however no positive identification was made of their role in pollination. The research conducted for this thesis showed that understanding the ecophysiological implications and managing for high winds and temperature will be key to site selection and the implementation of successful commercial production systems, and that adequate and carefully targeted nutrition will be essential for optimising growth and plant extract yield. Critical nutrient values identified in this study will aid in calibrating fertiliser rates for commercial production.