Academic literature on the topic 'Stackhousia tryonii Bailey (Stackhousiaceae)'

To elucidate the evolutionary origin of nickel (Ni) hyperaccumulation by the Australian serpentinite-endemic plant Stackhousia tryonii Bailey, phylogenetic analyses of chloroplast and nuclear DNA for Stackhousia and its close relatives were combined with assays of plant-tissue Ni concentrations. Thirty-five plants from 20 taxa were analysed by sequencing nuclear rDNA (ITS) and the plastid trnL–F region. Phylogenetic analysis of sequence data was conducted under maximum parsimony and Bayesian search criteria. In all, 100 plants from 39 taxa, including all 33 Stackhousia species, were analysed for Ni concentration by radial inductively coupled plasma atomic-emission spectrometry (ICP–AES). In phylogenetic analyses, S. tryonii was monophyletic, nested within a monophyletic Stackhousia. Only S. tryonii contained concentrations of Ni above the hyperaccumulation threshold (0.1%; 1000 ppm), containing between 0.25% (2500 ppm) and 4.1% (41 000 ppm) Ni by dry weight. Nickel-hyperaccumulation ability appears to have been acquired once during diversification of Stackhousia, by S. tryonii.

Stackhousia tryonii Bailey, which appears to be endemic to the serpentinite soils of the Port Curtis district, central Queensland, is a hyper-accumulator of nickel. Concentrations of this element reach 1-20% of the dry weight of the leaves and 0.1-1% in other parts of the plant. This is the first discovery of such behaviour in a plant from eastern Australia. S. tryonii is easily distinguishable from the Queensland occurrences of a related species, S. monogyna Labill., by its smaller inflorescences and muchbranched, tufted, slender stems and distinctive sparsely tuberculate seed coat. S. monogyna shows no abnormal nickel accumulation. Detailed diagnostic comparative descriptions of S. tryonii and S. monogyna are provided, and notes are given on the ecology and distribution of the two species.

Stackhousia tryonii Bailey is a rare, serpentine-endemic herb, with potential for use in phytoremediation and/or phytomining. This study evaluates the use of herbaceous heel cuttings to propagate S. tryonii on three rooting media [sand, Medium I; a commercial nursery mix, Medium II; and sand : peat moss : perlite (2 : 2 : 1; v/v), Medium III] following the application of plant growth hormones, viz. indole-3-butyric acid and naphthalene acetic acid (both as pure and commercial formulations, viz. Clonex Gel-green, Gel-purple and Gel-red), and honey. Cutting survival, rooting percentage, the number of primary and secondary roots produced, the length of the longest root and the total root length were evaluated after 10 weeks. Results show that there was a positive (P < 0.001) influence of plant growth regulator treatments on cuttings' survival. Medium III failed to support survival of cuttings. Percentage rooting (as a proportion of original number of cuttings) was 10–30% higher in Medium I than in Medium II. Cuttings treated with Clonex Gel-red, IBA at 1000 ppm and NAA at 250 ppm had 60–70% higher percentage rooting in Medium�I than in Medium II. Total number of primary roots per rooted cuttings was significantly (P�<�0.05) higher in Medium I with Clonex Gel-red and NAA at 1000 ppm. Treatments did not have significant effects on the number of secondary roots, the length of the longest root and the total root length. However, values for these parameters were significantly (P < 0.05) higher in Medium I than in Medium II. We conclude that cuttings from mature plants of S. tryonii could be used effectively to multiply S. tryonii, particularly with sand as rooting medium and prior to treatment of cuttings with Clonex Gel-red.

Stackhousia tryonii Bailey is one of the three nickel hyperaccumulators reported from Australia. It is a rare, herbaceous plant that accumulates (Ni) both in leaf and stem tissues. Localisation of Ni in leaf and stem tissues of S. tryonii was studied using two micro-analytical techniques, energy dispersive X-ray spectrometry (EDXS) and micro-proton-induced X-ray emission spectrometry (micro-PIXE). Dimethylglyoxime complexation of Ni was also visualised by bright- and dark-field microscopy, but this technique was considered to create artefacts in the distribution of Ni. Energy dispersive X-ray spectrometric analysis indicated that guard cells possessed a lower Ni concentration than epidermal cells, and that epidermal cells and vascular tissue contained higher levels of Ni than mesophyll, as reported for other Ni hyperaccumulators. The highest Ni concentration was recorded (PIXE quantitative point analysis) in the epidermal cells and vascular tissue (5400 μg g–1 DW), approximately double that recorded in palisade cells (2500 μg g–1 DW). However, concentrations were variable within these tissues, explaining, in part, the similarity between average Ni concentrations of these tissues (as estimated by region selection mode). Stem tissues showed a similar distribution pattern as leaves, with relatively low Ni concentration in the pith (central) region. The majority of Ni (73–85% for leaves; 80–92% for stem) was extracted from freeze-dried sections by water extraction, suggesting that this metal is present in a highly soluble and mobile form in the leaf and stem tissues of S. tryonii.

Selective accumulation of certain metals (elements) to exceptionally high concentrations in plants is intriguing. Approximately 425 species of so-called metal hyperaccumulators are currently known, of which about 75% hyperaccumulate nickel. Stackhousia tryonii Bailey (Stackhousiaceae) - a rare, herbaceous, serpentine-endelnic species - is one of the three nickel hyperaccumulators reported from Australia. This thesis reports research aimed at two broad aspects: propagation and ecophysiology of Ni hyperaccumulation in S. tryonii. Protocols were developed for seed germination, vegetative propagation and micropropagation and with the view to producing sufficient plants for use in the current study. Four-year-old S. tryonii seeds had poor germination (< 25%). However, this species was relatively easy to propagate via stem cuttings and micropropagation methods, as it possessed very high regenerative capacity (one explant produced up to 18 shoots within 4 weeks). Micropropagated shoots also responded well to ex vitro rooting, and were successfully hardened under controlled conditions. These propagation protocols could be useful to underpin conservation programs and mine site revegetation. The examination of natural populations of S. tryonii for arbuscular mycorrhizal colonisation suggested that S. tryonii is a favourable host. A moderately high colonisation (29-39%) of roots by arbuscular mycorrhizal fungi suggested a possible role of these fungi in improved nutrition of S. tryonii in typically nutrient-poor serpentine soils. A positive relationship between root colonisation and leaf Ni concentration suggested that mycorrhizal fungi might be involved in increased influx of Ni into the roots, which is readily transported and localised in the tissues. Spore density was very low (3-4 spores 100 g-¹dry soil, for two depths) in the associated serpentine soils and the dominant mycorrhizal species were: Glomus albidum, aggregatum, G. intraradices and G. tenebrosum. Based on five key soil characteristics (viz. pH, Ca, Mg, Ni and P), the study sites were segregated into four groups using hierarchical cluster analysis. Considerable variation existed in tissue Ni (and other elements) concentrations, both within and between populations and followed the order: leaf> root> stem. Localisation and spatial distribution of nickel, within both vegetative (leaf and stem) and reproductive (fruit) tissues were investigated using two microanalytical techniques [viz., micro-proton-induced x-ray emission spectrometry (micro-PIXE; nuclear microprobe) and scanning electron microscope with energy-dispersive x-ray spectroscopy (SEM-EDXS)]. In leaf and stem tissues, Ni was localised within epidermal and sub-epidermal tissues, palisade/mesophyll tissues, vascular bundles and/or pith. In contrast, in fruits, this metal was partitioned to the fruit wall (pericarp), while endospermic and cotyledonary tissues contained very little Ni. Accumulation of higher levels of Ni within the pericarp does not appear to inhibit seed germination in S. tryonii. To elucidate physiological mechanisms o fNi detoxification in S. tryonii, organic acids (leaf tissue) and free amino acids (xylem sap) were quantified using HPLC. Nickel concentration in the leaf tissues increased from 3695 g g-¹to 13,717 g g-¹with soil nickel supplementation, of which > 60% was extracted with dilute acid (0.025 M HCI). Oxalic, citric and malic acids were detected and quantified in the leaf tissue. Malic acid was the dominant organic acid, and based on a Ni to malic acid ratio (between 0.2:1 and 1:1), malic acid appears to play a major role in detoxification/transport and storage of Ni in S. tryonii. The total amino acid concentrations in the xylem sap decreased with nickel treatment. Glutamine was the major amino acid in both the low- and high- nickel treated plants. A role of amino acids in nickel complexation and transport in S. tryonii could not be established. The possibility of hyperaccumulated Ni acting as an osmoticum under waterstress (drought) in serpentine soils was also investigated. Drought severely affected the growth and overall biomass of the plants. However, survival of plants at the lowest levels of soil moisture (i. e. 20% of field capacity) suggested that it possesses an efficient water regulation mechanism. The results indicated possible involvement of Ni in osmotic adjustment under drought stress.