Biowastes to augment the essential oil production of Leptospermum scoparium and Kunzea robusta in low-fertility soil.

Biowastes are unwanted materials of biological origin. They include biosolids, dairy shed effluent, and sawdust. When applied to soil, biowastes can provide plant nutrients, but also introduce heavy metals, pathogens, or xenobiotics. Biowastes could improve degraded or low-fertility soils and generate revenue through the production of non-food products such as essential oils. We grew New Zealand native plants, manuka (Leptospermum scoparium J.R. Forst & G. Forst) and kanuka (Kunzea robusta de Lange & Toelken) in series of greenhouse experiments in low-to-medium-fertility soils (Bideford clay loam, Lismore stony silt loam, and Pawson silt loam) amended with either biosolids (up to 13500 kg N ha-1 equiv.), biosolids + sawdust (1:0.5-1250 kg N ha-1 equiv.) and dairy shed effluent (200 kg N ha-1 equiv.). Two types of biosolids from Kaikoura (KB) and Christchurch City Council (CB) were used in the experiments. CB (1500 kg N ha-1 equiv.) and dairy shed effluent (200 kg N ha-1 equiv.) increased the biomass of L. scoparium by up to 120% and 31%, and K. robusta by up to 170% and 34%, respectively. Adding sawdust to KB increased the biomass of L. scoparium and K. robusta although it offset the L. scoparium growth increase in the KB-only treatment. The growth response of K. robusta to biowastes was greater than L. scoparium with oil production in K. robusta increasing by up to 211% when 1500 kg N ha-1 equiv. of CB was applied to Lismore stony silt loam. Generally, the treatments had a negligible effect on oil concentration in all the soil types, except for the KB + sawdust treatment, which increased the oil concentration by 82%. Most of the EOs' major components were unaffected by biowaste addition in the soils, although some components increased in the Bideford clay loam following KB and KB + sawdust application. Biosolids increased foliar concentrations of Zn, Cu, and Cd, but these were below risk-threshold concentrations. Applying CB (up to 1500 kg N ha-1 equiv.) to low-fertility soils is recommended to establish ecosystems dominated by L. scoparium and K. robusta that annually would produce ca. 100 kg ha-1 of EOs worth US$ 26k and 24k, respectively. Adding sawdust to CB could have environmental benefits through reduction of N leaching. Field trials are warranted to elucidate critical ecological variables and production economics in biowaste management.

Breeding behaviour of Kunzea pomifera (Myrtaceae): self-incompatibility, intraspecific and interspecific cross-compatibility.

To examine breeding system characteristics of the endemic Australian prostrate shrub Kunzea pomifera, artificial hybridisations were undertaken using thirteen different genotypes of K. pomifera, to elucidate: (1) self-incompatibility, (2) intraspecific cross-compatibility in the species and (3) interspecific cross-compatibility with each of K. ambigua and K. ericoides. K. pomifera exhibited very low self-compatibility, with the barrier to self-fertilisation being prevention of pollen-tube growth in the style or ovary. Following intraspecific pollination amongst a number of different genotypes of K. pomifera, 38.4% of pollinated flowers developed fruit; arrest of compatible pollen-tubes in the style, preventing fertilisation, contributes to the low fruit set in this species. Interspecific compatibility was examined between K. pomifera (pistillate parent) and K. ambigua (staminate parent) where seed set per pollinated flower (4.47) was not significantly different from intraspecific crosses (4.66). In crosses between K. pomifera (pistillate parent) and K. ericoides as staminate plant, 0.037% of pollinated flowers produced fruit, with 0.0075 seeds per pollinated flower. Reproductive barriers between these two species were evident in the style of K. pomifera, where the growing tips of the K. ericoides pollen-tubes swelled and ceased to grow.

The interaction of temperature, water availability and fire cues regulates seed germination in a fire-prone landscape.

Ambient temperature and water availability regulate seasonal timing of germination. In fire-prone landscapes, the role of fire-related cues in affecting the range of temperatures and water potentials (psis) across which germination can occur is poorly known, especially in non-Mediterranean landscapes. We examined interactive effects of temperature (15 or 25 degrees C), psi (0 to -0.9 MPa), and fire-related cues (heat and smoke) on germination for seeds of three shrub species from fire-prone southeastern Australia. Incubation temperature affected germination of untreated seeds of Kunzea ambigua and Kunzea capitata (Myrtaceae) (reduction at 25 degrees C), but germination was uniformly low in Epacris obtusifolia (Ericaceae). Decreasing psi reduced germination across both incubation temperatures. Fire cues increased germination at both incubation temperatures and across psis, although in Kunzea the increase was smaller and occurred over a narrower range of psis at 25 degrees C. Hydrotime analysis suggested that fire cues reduced the amount of water necessary for germination of Kunzea seeds. Post-fire germination of the three study species may occur during the warm season, although it is reduced and confined to wet periods for the two Kunzea species. Warm season germination of the study species is consistent with a trade-off between the increased risk of failure of a cohort of seedlings, and benefits of early establishment of a cohort that may survive in an environment with aseasonal rainfall.