Postharvest abscission of Geraldton waxflower (Chamelaucium uncinatum Schauer) flower buds and flowers is ethylene-mediated. Exposure of floral organs to exogenous ethylene (1 mu L L-1) for 6 h at 20 degrees C induced separation at a morphologically and anatomically distinct abscission zone between the pedicel and. oral tube. Flower buds with opening petals and flowers with a nectiferous hypanthium were generally more responsive to exogenous ethylene than were flower buds enclosed in shiny bracteoles and aged (senescing) flowers. The anatomy of abscission-zone cells did not change at sequential stages of floral development from immature buds to aged flowers. The zone comprised a layer of small, laterally elongated-to-rounded, closely packed and highly protoplasmic parenchyma cells. Abscission occurred at a two- to four-cell-wide separation layer within the abscission zone. The process involved degradation of the middle lamella between separation layer cells. Following abscission, cells on both the proximal and distal faces of the separation layer became spherical, loosely packed and contained degenerating protoplasm. Central vascular tissues within the surrounding band of separation layer cells became torn and fractured. For flower buds, bracteoles that enclose the immature floral tube also separated at an abscission zone. However, this secondary abscission zone appeared less sensitive to ethylene than the primary ( central). oral-tube abscission zone as bracteoles generally only completely abscised when exposed to 10 mu L L-1 ethylene for the longer period of 24 h at 20 degrees C. The smooth surfaces of abscised separation-layer cells suggest that hydrolase enzymes degrade the middle lamella between adjacent cell walls.
Cat’s claw creeper, Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) is a major environmental weed of riparian areas, rainforest communities and remnant natural vegetation in coastal Queensland and New South Wales, Australia. In densely infested areas, it smothers standing vegetation, including large trees, and causes canopy collapse. Quantitative data on the ecology of this invasive vine are generally lacking. The present study examines the underground tuber traits of M. unguis-cati and explores their links with aboveground parameters at five infested sites spanning both riparian and inland vegetation. Tubers were abundant in terms of density (~1000 per m2), although small in size and low in level of interconnectivity. M. unguis-cati also exhibits multiple stems per plant. Of all traits screened, the link between stand (stem density) and tuber density was the most significant and yielded a promising bivariate relationship for the purposes of estimation, prediction and management of what lies beneath the soil surface of a given M. unguis-cati infestation site. The study also suggests that new recruitment is primarily from seeds, not from vegetative propagation as previously thought. The results highlight the need for future biological-control efforts to focus on introducing specialist seed- and pod-feeding insects to reduce seed-output.
Basal stem diameter was found to be a good predictor of above-ground biomass, canopy litterfall and mass of the accumulated litter layer for Acacia salicina Lindl., a tree that establishes successfully on mined land in central Queensland. The relationship between stem diameter and both biomass and litterfall was best described by an exponential model, and was related to exponential expansion of the canopy as tree diameter increased. In contrast, a simple linear model was used to describe the relationship between stem diameter and accumulated litter, partly reflecting a constant rate of litterfall per unit area of canopy over the range of tree sizes. The models were developed as a means of estimating biomass and nutrient capital and cycling in reconstructed ecosystems following open-cut coal mining.
Changes in the biomass of dead wood can be substantial in tropical woodland and should be included in complete carbon budgets. A recent estimate of biomass changes from long-term, permanent monitoring sites within the eucalypt woodlands of Queensland suggests that carbon accumulated in dead standing wood is similar to the amount of carbon accumulated within live woody biomass. However, this assessment did not include trees that were dead at the commencement of monitoring but have since been burnt or fallen over. Original data are presented from a permanent monitoring site, suggesting that on average 27% of dead standing biomass is consumed per low-intensity fire. The consumption of standing dead wood by fire, together with likely 'fall-down rates', could offset a substantial proportion of recently estimated dead standing wood carbon sink. The potential for using existing allometric equations to ascribe biomass to the components of dead standing wood (trunks, branches, bark) on permanent monitoring plots is reviewed. Some valid generalisations can be recognised but a lack of standardisation in allometric studies presents problems. It is suggested that data from survey, monitoring and experiments could drive worthwhile models of dead standing wood biomass. This pool will probably vary substantially through time and space, depending on climatic conditions, fire and termite activity.
Increasing severity of environment associated with increasing altitude in mountain ecosystems (decreasing temperature, increasing duration of snow cover) can affect relative and absolute biomass-allocation patterns in plants. Biomass allocation was examined along a 620-m altitudinal gradient in the Australian Alps for the important environmental weed Achillea millefolium (L., Asteraceae, yarrow). Relative and absolute biomass allocation (dry weight) to reproductive (capitula, flowering stems and associated leaves), vegetative (leaves not on the flowering stem) and below-ground structures (rhizome and roots) were measured at each of nine sites by using quadrats. Increasing altitude resulted in a decrease in relative and absolute allocation of biomass to reproductive structures. For example, the dry weight of inflorescences declined as altitude increased because of a decrease in the weight of the terminal and side branches of the inflorescences, but not the total number of capitula produced. There was also a trend for increased relative allocation to below-ground structures with increasing altitude, even though altitude did not affect absolute allocation to below-ground and vegetative structures, or the total dry weight of A. millefolium. These results are consistent with those for other species growing at high altitude. The management implications for the control of A. millefolium in the Australian Alps are discussed, including in relation to predicted climatic change. Yes Yes
The reproductive ecology of the dioecious herb Aciphylla simplicifolia (F.Muell.) Benth. (Apiaceae, Mountain Aciphylla) was examined in Kosciuszko National Park. Differences in floral display and flowering phenology between male and female plants were consistent with predictions based on theories concerning sexual dimorphism in dioecious plants. For example, male plants had larger floral displays than females at the alpine sites sampled. Male inflorescences had four times as many flowers as females and more than three times the area of floral display. In addition to differences in floral display, there was a sex-specific pattern in flowering phenology at six alpine sites. At these sites, there were more male inflorescences with buds and flowers and more female inflorescences finished flowering than would be expected if gender did not affect flowering phenology. To determine whether increasingly severe conditions associated with higher-altitude sites were associated with male-biased sex ratios, the number of male and female plants were compared for 20 sites over a 600-m altitudinal range from montane to alpine (total 4274 plants). As altitude increased and as the vegetation zone changed from subalpine to alpine, the sex ratio became increasingly male-biased, with sites in the alpine ranging from 1.45 males per female to 8.53 males per female. Sexual dimorphism in floral display, flowering phenology and sex ratios was consistent with what would be predicted for plants with sex-specific differences in resource allocation. Yes Yes
In one of the few dioecious species in the Australian alpine region, Aciphylla glacialis (F. Muell.) Benth. (Apiaceae) flowering and resource allocation patterns were found to differ between males and females, potentially a response to sex-specific selection under the limited conditions for growth and reproduction imposed by the alpine environment. Sex ratios were male biased with approximately 1.49 males to each female in each of five populations of A. glacialis. Male plants had larger floral displays than female plants, producing four times as many flowers per inflorescence and an average of 3.5 inflorescences per plant, compared to 2.9 inflorescences for females. Male and female plants commenced flowering within a few days of each other (average 18 January for males, 19 January for females) but female plants completed flowering earlier, finishing at the end of January, while males were still flowering well into February. Male and female plants did not differ in size as estimated by the number of stems per plant, nor in the proportion of resources allocated to reproduction compared with above ground vegetative structures. However, they did differ in the way resources were allocated to vegetative and floral structures, particularly among larger plants. Large female plants produced heavier stems and infloresences than males. Heavier inflorescences in females may be associated with the need for greater structural support for inflorescences when fruiting, while the increased dry weight of stems may reflect differences in the ways in which the sexes match growth and resource demands for flowering.
Physical changes and flows of energy at the interface between two contrasting ecosystems affect the distribution of species across the ecotone. The maintenance and stability of the, often abrupt, transition between Australian rainforest and non-rainforests is often attributed to fire. We use pre-germination treatments of smoke and heat on soil seed bank samples to determine plant distributions across the edge between subtropical rainforest and an adjacent eucalypt-dominated wet sclerophyll forest. Soil seed bank collections at 15 m within the eucalypt forest had both significantly higher density and diversity of seedlings than those at 30 m, at the edge itself or at any site within the rainforest. This response was most apparent when a pre-germination smoke treatment was applied. We suggest that smoke is an important germination trigger for species regenerating at this interface. Our results confirm the importance of fire in determining and maintaining the nature of this ecotone. Yes Yes
Limited information exists on the relation between the capacity of mangrove seedlings to oxidise the rhizosphere and their differential waterlogging tolerance. Laboratory experiments were conducted to estimate radial oxygen loss (ROL) by the entire root, the area of oxidising sites (AOS) on the root surface, root porosity (POR), and the internal diffusive resistance in the ground tissue of seedlings of six mangrove species that show a differential response to flooding. Radial oxygen loss was extremely low in all viviparous seedlings (0.7-1.5 μmol O2 per cm2AOS per day). Differential tolerance of species coincided with the degree of porosity (14.8-45.7%) and the ability of seedlings to develop barriers to oxygen leakage on the root surface. The percentage area of lacunae in the ground tissue of seedlings of the four viviparous species revealed a constriction of the air flow path at the hypocotyl junction. These findings suggest that: (i) the differential tolerance to waterlogging in mangrove seedlings is not simply based on their ability to oxidise the rhizosphere; (ii) the high diffusive resistance in the hypocotyl junction is likely to affect root aeration when the plant's access to air is limited by partial or total submergence; and (iii) waterlogging tolerance is probably a function of the strategy by which roots conserve oxygen to maintain aerobic metabolism for longer periods during submergence. Implications of these findings in seedlings are discussed in relation to other anatomical and morphological adaptations to waterlogging in mature mangroves.
Alternative-state theory commonly applied, for aquatic systems, to shallow lakes that may be dominated alternately by macrophytes and phytoplanktons, under clear-water and enriched conditions, respectively, has been used in this study as a basis to define different states that may occur with changes in wetland salinity. Many wetlands of the south-west of Western Australia are threatened by rapidly increasing levels of salinity as well as greater water depths and permanency of water regime. We identified contrasting aquatic vegetation states that were closely associated with different salinities. Salinisation results in the loss of freshwater species of submerged macrophytes and the dominance of a small number of more salt-tolerant species. With increasing salinity, these systems may undergo further changes to microbial mat-dominated systems composed mostly of cyanobateria and halophilic bacteria. The effect of other environmental influences in mediating switches of vegetation was also examined. Colour and turbidity may play important roles at low to intermediate salinities [concentration of total dissolved solids (TDS) 1000 mg L-1 TDS). The role of nutrients remains largely unquantifies in saline systems. We propose that alternative-states theory provides the basis of a conceptual framework for predicting impacts on salinity adds a further tool to decision-making processes. A change in state represents a fundamental change in restoration strategies. Further work is required to better understand the influence of temporal variation in salinity on vegetation states and probable hysteresis effects.
Pathogenicity tests with Phytophthora cinnamomi were conducted on 25 perennial species from the jarrah (Eucalyptus marginata) forest of Western Australia. Most species tested had been found in a separate study to be scarce on sites affected by Phytophthora cinnamomi but frequently found in unaffected vegetation. Some species that were known to be field-tolerant of P. cinnamomi and some that were highly susceptible to infection were included in the study for comparison. Phytophthora cinnamomi was recorded from 13 of 17 species not previously known to be susceptible. Phytophthora cinnamomi was subsequently isolated from dead plants of two of these 13 species in the field. The interpretation of results from the glasshouse trials was difficult for some species because of inconsistent patterns of death and P. cinnamomi isolation in the glasshouse trials. Phytophthora cinnamomi probably causes decline in wild populations of Stylidium amoenum, based on the ease of field and glasshouse isolation of P. cinnamomi and the scarcity of this forb on dieback sites. It may also contribute to decline in populations of Boronia fastigiata, Hybanthus floribundus, Labichea punctata, Scaevola calliptera and Stylidium junceum, although further field sampling is required to confirm this.
The vegetation of seven sites in the northern jarrah forest of Western Australia infested with Phytophthora cinnamomi was recorded and compared with adjoining vegetation. The number of species per quadrat was found to be the same in vegetation affected by P. cinnamomi as in healthy vegetation, although there were more species overall in affected vegetation. Vegetation of uninfested sites had a higher cover and more species per quadrat of trees and shrubs and lower cover and fewer species per quadrat of annual plants than vegetation of infested sites. Although many species that are known to be highly susceptible to infection by P. cinnamomi were rare at infested sites, only two (Banksia grandis and Tetratheca hirsuta) were absent from all of the 50-year-old infested parts of sites. Several species that are known to be highly susceptible to infection by P. cinnamomi were as common at infested as at healthy sites. The presence of such species at infested sites and the capacity of P. cinnamomi to infect species it does not kill suggest that this pathogen will persist and continue to influence future vegetation in the jarrah forest.
Aechmea tuitensis (P. Magaba and E. Lott) is a narrow endemic species from Mexico. Only one population has been reported. We studied the genetic variation and structure, and clonal diversity of this rare bromeliad by using starch gel electrophoresis. Six enzyme systems encoded by nine gene loci were resolved in nine subpopulations. The percentage of polymorphic loci was high (77.8%). Mean expected heterozygosity for the population was 0.12. All loci except CPX-1 were in Hardy-Weinberg equilibrium. Genetic diversity was substantially larger within subpopulations (mean F-is = 0.631) than between them (F-st = 0.196). We detected 33 genetically distinguishable clones from 109 plants (ramets) sampled. One clone had a frequency of 32.1%, others showed frequencies ranging from 1.8 to 9.2%, and 19% of the total samples were unique multilocus genotypes. Aechmea tuitensis exhibits high genetic diversity even though it has an extremely narrow distribution. Our results also suggest that the effect of genetic drift on genetic structure in A. tuitensis might be counteracted by the influence of vegetative reproduction.
Woody vegetation cover interpreted from aerial photography requires assessment against field data as the signature of woody vegetation cover may differ between photoscales, vegetation types and photo-interpreters. Measurements of aerial woody cover taken from aerial photography of four different photoscales were compared with a field dataset from Eucalyptus- and Acacia-dominated landscapes of semi-arid Queensland. Two interpreters employed a method that utilises a stereoscope and sample-point graticule for manual quantified measurements of aerial woody cover. Both interpreters generated highly significant models accounting for 77 and 78% of deviance. Photoscale appears to have a consistent effect whereby the signature of woody cover increases as the photoscale decreases from 1 : 25 000 to 1 : 80 000, although the magnitude of this effect was different between interpreters. The results suggest no substantial differences in the shape of models predicting crown cover between Acacia- and Eucalyptus-dominated land types, although the precision of the models was greater for the Acacia (90–91% of residual deviance) than for the Eucalyptus (50–56% of residual deviance) land type. The reduced accuracy in the Eucalyptus land type probably reflects the relatively diffuse crowns of the dominant trees. The models generated for this dataset are within the range of those from other calibration studies employing photography of a range of scales and methodologies. The effect of photoscale is verified between the available studies, but there may also be variations arising from methodological differences or image properties. The present study highlights the influence of photoscale and interpreter bias for assessing woody crown cover from aerial photography. Studies that employ aerial photography should carefully consider potential biases and cater for them by calibrating assessments with field measurements.
Studies attempting to calibrate vegetation attributes from aerial photography with field data are reviewed in detail. It is concluded that aerial photography has considerable advantages over satellite-based data because of its capacity to assess the vertical dimension of vegetation and the longer time period the record spans. Limitations of using the aerial photo record as digital data include standardising image contrast and rectification. Some of these problems can be circumvented by manual techniques, but problems of crown exaggeration that varies with photo scale and variation in contrast between the textures of tree crowns and the ground remain. Applications of aerial photography for assessing vegetation change are also reviewed and include deforestation, reforestation, changes in vegetation boundaries, tree density, community composition and crown dieback. These changes have been assessed at scales ranging from individual tree crowns to regional landscapes. In Australia, aerial photography has provided a clear demonstration of deforestation rates and the expansion and contraction of forest and woodland, which is generally attributed to changes in grazing and fire regimes. It is suggested that manual techniques with point-based sampling, digital processing of data for complete spatial coverages and the application of photogrammetric measurements with stereo-plotters are all techniques with great promise for utilising this underrated medium for assessment of vegetation dynamics.
Changes in the density of woody vegetation in arid and semiarid rangelands have the potential to dramatically reduce productivity as well as adversely affect ‘natural’ ecosystem processes. Many parts of Australia are believed to have experienced thickening of woody vegetation since European occupation and the associated changes to fire and grazing regimes that followed. Unfortunately there is little empirical evidence to support a widely held perception of thickening. This study analyses the available historical aerial photographic coverage for the mulga lands bioregion of south-western Queensland, Australia; a record spanning the second half of the twentieth century. Changes in woody vegetation canopy cover were assessed for 190 sites. More than half of the sites had no evidence of mechanical disturbance and thus reflected general, or background trends in woody vegetation cover. The region-wide average extent of change on these undisturbed sites was estimated to be approximately a 3.6% increase in canopy cover over the study period. Thus, a trend toward vegetation thickening was detected. However, large variation was observed depending on the land systems and rainfall zone where sites were located. The results are discussed in the context of century scale climate variability and perceptions of vegetation change and a tentative explanatory model is presented to account for the observed data.
Shoot biomass and lignotuber size of seedlings of three eucalypt species, Eucalyptus acmenoides Schauer, E. siderophloia Benth. and Corymbia variegata [syn. E. maculata (F. Muell.)K. D. Hill and L. A. S. Johnson], were measured for glasshouse-grown seedlings established under two water and nutrient regimes. Seedlings were subjected to shoot removal (clipping) at ages from 9 to 19 weeks, and transferred to the high water treatment for a further 8 weeks to assess shoot emergence from lignotubers. Seedling shoot biomass was greater in both the high than the low nutrient and water treatments, but lignotuber diameter was not affected significantly. C. variegata seedlings had the largest lignotuber diameters, followed by E. siderophloia and E. acmenoides, respectively. Although growth of shoots was influenced by nutrient availability, results suggest that species differences in the growth of lignotubers was less affected. It is suggested that lignotuber growth was strongly influenced by genotype. More than 70% of C. variegata seedlings clipped at 9 weeks sprouted, compared with only 5 and 10% of seedlings of E. siderophloia and E. acmenoides, respectively. All C. variegata seedlings sprouted after being clipped at 19 weeks, but < 80% of E. siderophloia and < 60% of E. acmenoides sprouted when clipped at the same age. It was concluded that seedlings forming part of the regeneration stratum in dry sclerophyll forests need to be protected from damage for at least 4 months (for C. variegata) or at least 6 months (for E. siderophloia and E. acmenoides) if they are to survive by sprouting from lignotubers.
A glasshouse experiment was designed to determine whether the terrestrial bladderwort species Utricularia uliginosa Vahl. gained any growth advantage from carnivory at different levels of nitrogen enrichment of the substrate. Three organism treatments were used: a control, a protist-only treatment (Euglena spp.) and a protist + meiofauna treatment (Euglena spp. plus nematodes, copepods, ostracods, cladocerans and Acarina). The organism treatments were factorially combined with three nitrogen levels (N0, N1, N2). Populations of Euglena were successfully established in the substrate of pots in the protist, and meiofauna + protist treatments, and were found in the traps of plants growing in these treatments. Populations of the meiofauna from the inoculating cultures were successfully established in the meiofauna + protist treatment, and were trapped by plants in these treatments. A background contamination of the control and protist-only treatments by Acarina occurred over the course of the experiment; however, numbers of Acarina in these treatments were at least an order of magnitude lower than numbers of meiofauna in the meiofauna + protist treatment. Non-acarinid meiofauna were restricted solely to the meiofauna + protist treatment. Organism treatment interacted significantly with the nitrogen level of the substrate to affect growth of Utricularia. Plants trapping Euglena (+ Acarina) had significantly less dry weight than control plants at the N0 base level of nitrogen; this negative effect of trapping Euglena on plant growth disappeared at the two higher nitrogen levels. The dry weight of plants trapping the full range of meiofauna at the N0 level was comparable with control plants. Plants trapping the full range of meiofauna + Euglena at the N1 level had significantly more dry weight than plants trapping Euglena only, and the highest dry weight of any treatment; the benefit of trapping the full range of meiofauna + Euglena was non-significant at the N2 level. Dry weight of plants was not significantly affected by nitrogen in any organism treatment. These results suggest that carnivory was overcoming a nitrogen deficiency induced by Euglena at the N0 level, but was overcoming deficiencies of other nutrients at the N1 level.
The introduced soil-borne pathogen Phytophthora cinnamomi Rands infects and kills a large number of species in the jarrah (Eucalyptus marginata Donn. ex Smith) forest of Western Australia, causing great floristic and structural change. Many of the floristic changes can be explained simply by the known susceptibility of species to infection. Some common species, however, are rarely found at infested sites but are thought to be resistant to infection. It has been postulated that such species may be affected by the change in habitat caused by the death of trees, and not by P. cinnamomi directly. If this were the case, such species should cluster around surviving trees at infested sites. The occurrence of a susceptible species in the vicinity of trees surviving at infested sites has also been reported. To investigate the spatial relationship between trees and understorey species, the positions of trees and selected perennial understorey species were mapped at two sites in jarrah forest long-affected by P. cinnamomi. Random sets of plants and trees were generated and used in simulations to test whether understorey species grew closer to trees than expected. Many understorey species, both resistant and susceptible to infection by P. cinnamomi, were found to grow closer than expected to trees currently growing at the sites and closer to the trees that would have been present at the time of infestation. This suggests that not only do these trees enable some resistant species to persist at infested sites but that they also offer protection to some susceptible species against damage by P. cinnamomi. The proximity of many understorey species to trees that are likely to have appeared at the study sites since the first infestation indicates that the maintenance and enhancement of tree cover at infested sites in the jarrah forest may limit the damage caused by P. cinnamomi and assist in the protection of biodiversity.
The history and nomenclature of Lenormandia prolifera are given. Observations are made on the structure of the vegetative fronds and the various reproductive organs. L. prolifera is compared with other members of the Amansieae. A description is given of carpospore development in L. prolifera.
Litter fall studies were used to assess phenologies and productivity of Sonneratia alba, S. caseolaris and their putative hybrid, S, x gulngai, in north-eastern Australia. Annual total litter falls (mean + s.d.) were 2.5 2 0.5, 2.6 f 1.4 and 3.2 g dry weight m-2 day-', respectively. Litter was partitioned into leaves (47, 61 and 50%), wood (12, 14 and 19%) and reproductive parts (41, 25 and 31%). In addition, monthly reproductive schedules were produced for each taxon. Differences between taxa were pronounced. For S. alba, flowering peaked in December and fruiting in February. For S. caseolaris, flowering peaked in late February and fruiting in June and July. S. x gulngai was characterised by an apparent combination of events described for the two putative parental forms. This observation, along with a low (a%fru)iti ng success, provides further support for the hybrid status of this taxon.
The presence of lysigenous cavities filled with terpenoid aldehydes (generically termed 'gossypol') in most tissues of cultivated cottons and their relatives imparts natural resistance to a variety of insect, fungal, and bacterial pests. Deposition of terpenoid aldehydes in cultivated cotton seed, however, tenders cottonseed oils and protein meals toxic to non- ruminant animals, including humans. Seeds of the so-called 'glandless seeded' Australian Gossypium L. species (Gossypium subgenus Sturtia (R.Br.) Tod.) reportedly lack terpenoid aldehydes, and thus may represent an important genetic resource in the development of cottonseed oils and protein meals free of these toxins. Information supporting this assertion, however, is fragmentary and contradictory. To resolve this, seeds of all known Australian Gossypium species were surveyed chemically and anatomically. Immature lysigenous cavities were present in seeds of all 18 species. Lysigenous cavities of sect. Sturtia and sect. Hibiscoidea Tod. seeds were unpigmented and invisible to the naked eye, while pigmented, macroscopically visible lysigenous cavities occurred in all the sect. Grandicalyx (Fryxell) Fryxell seeds. HPLC (high performance liquid chromatography) analysis revealed that sect. Sturtia and sect. Hibiscoidea seeds did not contain detectable levels of terpenoid aldehydes, but that sect Grandicalyx seeds contained gossypol.
The pericarp and aleurone layer of cereal grains are associated with the accumulation of anti-nutritional factors, vitamins, high-value proteins and trace elements. Variations in these tissues may be associated with important differences in the nutritional and functional value of cereals as human or animal feeds. Wild crop relatives (WCR) have been successfully utilised in breeding programs to improve agronomic traits such as dwarfism and pest and disease resistance. Australia’s undomesticated grass species (Poaceae) provide a unique and genetically diverse array of WCRs and therefore the grains of 17 Australian WCRs were examined by scanning electron microscopy (SEM). Aleurone of each WCR was compared with that of its nearest domesticated cereal relative, with little significant morphological variation observed to this structure. A novel subaleurone morphology was observed in the Sorghum WCRs which had the appearance of being a very dense protein matrix only sparsely embedded with small starch granules or completely lacking starch granules. Histochemical analysis of a subsample of the specimens confirmed that the described morphology was lacking starch granules and had a proteinaceous matrix. Such morphological variations within Australian wild crop relatives of commercial cereals may provide novel sources of genetic diversity for future grain improvement programs.
In fire-prone regions, assessing stand age of obligate-seeding species provides an estimate of time since last fire. If a relationship exists between tree age and diameter, measuring the stem diameter of trees is a simple field method for determining age-class distribution within a stand. In this study, we examined whether age of the obligate seeder Allocasuarina littoralis could be estimated from diameter by using dendrochronological applications. Analysis of radial samples established that A. littoralis puts down annual growth rings. The relationship between the number of growth rings and stem diameter was tested for both male and female stems by using regression analysis. For female plants, this relationship varied significantly between sites. In contrast, male stems provided a strong relationship between age (as a function of the number of growth rings) and diameter, regardless of site. A regression model estimating age from stem diameter, based on male trees only, was subsequently developed and tested with data collected from trees of known age. Predicted estimates from stem diameter were within 3.76 years of the true age. Field measures of stem diameters can therefore provide a tool for estimating the fire history, especially time since last fire, in areas where stands of this species occur.
Patterns in species density and richness per altitudinal interval have been found when sampling across plant community boundaries, including in the largest contiguous alpine area in Australia. To see if similar patterns occur within a single community, vascular plant composition was systematically sampled with replicate nested quadrats of increasing size (0.01, 0.06, 0.25, 1.00, 4.00, 25.00, 49.00 and 100-m2 size) sampled from ~1850 to 2100 m altitude in tall alpine herbfield, Australia. The only significant relationships with altitude were quadratic relationships for the density of herb and graminoid species, with peak density at mid-altitudes and a linear decline in total species richness with altitude for 0.06 m2 quadrats. The composition of 100 m2 quadrats was unrelated to altitude when tested using Analysis of Similarity for total composition, whereas the relationship was significant for growth-forms and the origin (local endemics, Australia endemics and weeds) of species. Location data from this, and 11 other studies were used to compare the species richness of more of the flora (183 species) using 50-m altitudinal bands. There were significant quadratic relationships for total species richness and the number of herb and shrub species with a peak in richness around 2000 m. Therefore altitude does affect species richness overall in this alpine region, but only has a weak effect on species density within the most common plant community. Yes Yes
This study investigated the interspecific amplification of 35 microsatellite loci developed for M. alternifolia across seven other species within the Myrtaceae. All the primers used gave successful amplification of loci in at least one of the species tested. The level of success varied between species; 88.6% of primers gave amplification products for Melaleuca spp., 74.3% for Callistemon salignus, 45.7% for Eucalyptus spp. and 25.7% for Backhousia citriodora. Sequencing of a number of amplification products confirmed the presence of microsatellites in those loci. This study shows that the development of species-specific microsatellite libraries might not always be necessary. Cross-species amplification could enable the application of microsatellite technology to studies with limited resources, a feature characteristic of conservation projects.
Annual totals of the components of litter fall (leaves reproductive parts, stipules, wood and residual debris) are presented for Rhizophora apiculata, R. lamarckii, R. stylosa, Sonneratia alba, Avicennia sp., Ceriops tagal, Bruguiera gymnorrhiza and B. parviflora from a large number of sites at Hinchinbrook Island, northeastern Australia. Total annual litter fall ranged among all species from 3.8 to 19.6 t ha-1. The mean value among the Rhizophora spp. was 9.6 t ha-1 yr-1. Leaves generally made up the most important component of all litter materials. The results are compared with records in the literature for tidal and non-tidal forests elsewhere in the tropics.
Seed persistence of Gymnocoronis spilanthoides (D.Don) DC.; Asteraceae (Senegal tea), a serious weed of freshwater habitats, was examined in relation to burial status and different soil moisture regimes over a 3-year period. Seeds were found to be highly persistent, especially when buried. At the end of the experiment, 42.0%, 27.3% and 61.4% of buried seeds were viable following maintenance at field capacity, water logged and fluctuating (cycles of 1 week at field capacity followed by 3 weeks’ drying down) soil moisture conditions, respectively. Comparable viability values for surface-situated seeds were ~3% over all soil moisture regimes. Predicted times to1% viability are 16.2 years for buried seed and 3.8 years for surface-situated seed. Persistence was attributed primarily to the absence of light, a near-obligate requirement for germination in this species, although secondary dormancy was induced in some seeds. Previous work has demonstrated low fecundity in field populations of G. spilanthoides, which suggests that soil seed banks may not be particularly large. However, high levels of seed persistence, combined with ostensibly effective dispersal mechanisms, indicate that this weed may prove a difficult target for regional or state-wide eradication.
Acclimation of gas exchange to temperature and light was determined in 18-month-old plants of humid coastal (Gympie) and dry inland ( Hungry Hills) provenances of Eucalyptus cloeziana F. Muell., and in those of a dry inland provenance of Eucalyptus argophloia Blakely. Plants were acclimated at day/night temperatures of 18/13, 23/18, 28/23 and 33/ 28 degreesC in controlled-temperature glasshouses for 4 months. Light and temperature response curves were measured at the beginning and end of the acclimation period. There were no significant differences in the shape and quantum-yield parameters among provenances at 23, 28 and 33 degreesC day temperatures. Quantum yield [mumol CO2 mumol(- 1) photosynthetic photon flux density (PPFD)] ranged from 0.04 to 0.06 and the light response shape parameter ranged from 0.53 to 0.78. Similarly, no consistent trends in the rate of dark respiration for plants of each provenance were identified at the four growth temperatures. Average values of dark respiration for the plants of the three provenances ranged from 0.61 to 1.86 mumol m(-2) s(-1). The optimum temperatures for net photosynthesis increased from 23 to 32 degreesC for the humid- and from 25 to 33 degreesC for the dry-provenance E. cloeziana and from 21 to 33 degreesC for E. argophloia as daytime temperature of the growth environment increased from 18 to 33 degreesC. These results have implications in predicting survival and productivity of E. cloeziana and E. argophloia in areas outside their natural distribution.
Effects of soil water availability on transpiration efficiency (WUET), instantaneous water use efficiency (WUEi) and carbon isotope composition (delta(13)C) were investigated in 7-month-old plants of humid coastal (Gympie) and dry inland ( Hungry Hills) provenances of Eucalyptus cloeziana F. Muell. and in a dry inland provenance of E. argophloia Blakely (Chinchilla), supplied with 100 (W-100), 70 (W-70) and 50% (W-50) of their water requirements. At W-100, WUET of the three provenances were not significantly different but as available soil moisture decreased, E. argophloia produced greater biomass and demonstrated significantly higher WUET than either E. cloeziana provenance. Midday WUEi was not significantly affected by watering regime within each provenance but was lowest in E. argophloia. A decrease in soil water availability caused a consistent increase in delta(13)C values in all three provenances; however, delta(13)C values of E. argophloia in all three water regimes were significantly lower than those of E. cloeziana provenances, which did not differ significantly from each other. For all three provenances, delta(13)C was not correlated with WUEi but height and root collar diameter were negatively correlated to delta(13)C. There was little evidence of differences in delta(13)C, WUET and WUEi between E. cloeziana provenances but clear differences between E. cloeziana and E. argophloia. The high WUET, low WUEi and low delta(13)C for E. argophloia may have implications in the selection of Eucalyptus provenances for commercial forestry in low-rainfall regions.
The vegetation and environmental setting of permanent spring wetlands are described from a survey of 269 spring complexes throughout seasonally arid Queensland. Wetlands associated with springs in the western and southern discharge areas of the Great Artesian Basin are floristically distinct from other spring wetlands. Ordination analysis suggests that the biogeographic regions and the broad geological substrates that support spring wetlands provide a meaningful representation of floristic range. An existing classificatory system that defines ‘regional ecosystems’ on the basis of the biogeographic region and broad geological substrate is adopted to define 15 spring-wetland types in seasonally arid Queensland. The conservation value of the springs is assessed by a scheme that weights plant species populations on the basis of their endemicity and isolation from other populations, demonstrating that both Great Artesian Basin and non-Great Artesian Basin springs have similar conservation values. Australian Journal of Botany 52(5) 583–595
Organically preserved plant macrofossils, which accumulated during the period of late Neogene tectonic uplift, were documented from four localities in the South Island. These include Arapito Road (near Karamea), Waitahu River (near Reefton), Tadmor (south of Nelson) and Grey River (north of Christchurch). The assemblages from these localities were species-poor compared with older Cenozoic assemblages, but included a range of conifers and angiosperms. Of note was the presence of Acmopyle (currently extinct in New Zealand) and Cupressaceae in all four localities. At least two new species of Acmopyle were present, with leaf shapes distinctly different from any currently known. One of them (A. kirrileeae sp. nov.) had unflattened, awl-like foliage, whereas the other (A. biformis sp. nov.) had dimorphic foliage, including very distinct bilaterally flattened leaves with a mucronate apex. Both of these were distinct from the flattened foliage, which predominates on extant Acmopyle. Other conifers included Araucaria, Dacrycarpus, Dacrydium, Phyllocladus and Libocedrus. Angiosperms included Beauprea (now extinct in New Zealand) Beilschmiedia, Knightia sp., Metrosideros, Nothofagus and probably Pseudowintera, Pseudopanax and Cunoniaceae. The assemblages suggest temperate conditions.
A 'multiple-constraints' model-data assimilation scheme using a diverse range of data types offers the prospect of improved predictions of carbon and water budgets at regional scales. Global savannas, occupying more than 12% of total land area, are an economically and ecologically important biome but are relatively poorly covered by observations. In Australia, savannas are particularly poorly sampled across their extent, despite their amenity to ground-based measurement ( largely intact vegetation, low relief and accessible canopies). In this paper, we describe the theoretical and practical requirements of integrating three types of data ( ground-based observations, measurements of CO2/H2O fluxes and remote-sensing data) into a terrestrial carbon, water and energy budget model by using simulated observations for a hypothetical site of given climatic and vegetation conditions. The simulated data mimic specific errors, biases and uncertainties inherent in real data. Retrieval of model parameters and initial conditions by the assimilation scheme, using only one data type, led to poor representation of modelled plant-canopy production and ecosystem respiration fluxes because of errors and bias inherent in the underlying data. By combining two or more types of data, parameter retrieval was improved; however, the full compliment of data types was necessary before all measurement errors and biases in data were minimised. This demonstration illustrates the potential of these techniques to improve the performance of ecosystem biophysical models by examining consistency among datasets and thereby reducing uncertainty in model parameters and predictions. Furthermore, by using existing available data, it is possible to design field campaigns with a specified network design for sampling to maximise uncertainty reduction, given available funding. Application of these techniques will not only help fill knowledge gaps in the carbon and water dynamics of savannas but will result in better information for decision support systems to solve natural-resource management problems in this biome worldwide.
In vitro propagated shoots of four-wing saltbush (Atriplex canescens, Pursh Nutt) showed severe symptoms of hyperhydricity. We show that the reversion of hyperhydric A. canescens shoots to normal shoots was significantly affected by the presence of inorganic nitrogen in the culture vessel. When the culture vessel was vented or when ammonium nitrate was deleted from Murashige and Skoog basal medium, rates of reversion were significantly higher. Although statistically significant differences were evident when comparing vented v. non-vented treatments for each medium, the modified culture medium with vented closures was consistently the best treatment, showing a total cumulative frequency of 39.7% reversion to normal morphology, compared with a total cumulative frequency of 7.1% observed in the control treatment. Resulting normal shoots also showed significant improvements in further manipulations, including rooting in vitro, transplantation to soil and survival in native sites.
Processes that are important for the recruitment of plants include aspects of the reproductive phenology, development and release of propagules, dispersal of propagules and the storage of mature seed ready for germination when conditions are suitable. This paper explores the relative importance of these mechanisms by examining the contents of the seedbank in the soil, the reproductive phenology of particular overstorey species, the importance of dispersal by water and the survival and longevity of seed on two contrasting rivers in Western Australia. Examination of the soil seedbank showed that regeneration of vegetation from this source is probably important for annual species of herbs and grasses but of only minor significance for perennial species. This is most likely due to high levels of disturbance and the unstable soils in the riparian zone. Reproductive phenology of the four overstorey species monitored in this study appears to be well-adapted to the hydrological regimes on the respective rivers. For the seed of riparian overstorey species examined, seed longevity was poor and seed predation rates were high. The occurrence of seed in floodwater debris indicated the importance of secondary dispersal of seed by water, particularly for the Ord River. For the two overstorey riparian species examined on the Ord River in the subtropical north of Australia, there is little storage of seed and plants are reliant on favourable conditions prevailing at the time of seed fall. The likelihood of seed finding a safe site for successful germination is enhanced by secondary dispersal in high river flows. For overstorey species on the Blackwood River in the temperate zone of south-western Australia there is some storage of seed in the canopy but dispersal of seed to safe sites is also enhanced by river flow. For riparian vegetation on these rivers, regeneration from seed can occur through several processes. The relative importance of these different mechanism varies for each river, reflecting their vastly different hydrology and climate.
This study examined the ability of foliar applications of the fungicide phosphite to contain colonisation of Phytophthora cinnamomi in a range of plant species growing in natural plant communities in the northern sandplain and jarrah (Eucalyptus marginata) forest of south-western Australia. Wound inoculation of plant stems with P. cinnamomi was used to determine the efficacy of phosphite over time after application. Colonisation by P. cinnamomi was reduced for 5–24 months after phosphite was applied, depending on the concentration of phosphite used, plant species treated and the time of phosphite application. Plant species within and between plant communities varied considerably in their ability to take up and retain phosphite in inoculated stems and in the in planta concentrations of phosphite required to contain P. cinnamomi. As spray application rates of phosphite increased from 5 to 20 g L–1, stem tissue concentrations increased, as did the ability of a plant species to contain P. cinnamomi. However, at application rates of phosphite above 5 g L–1 phytotoxicity symptoms were obvious in most species, with some plants being killed. So, despite 10 and 20 g L–1 of phosphite being more effective and persistent in controlling P. cinnamomi, these rates are not recommended for application to the plant species studied. The results of this study indicate that foliar application of phosphite has considerable potential in reducing the impact of P. cinnamomi in native plant communities in the short-term. However, in order to maintain adequate control, phosphite should be sprayed every 6–12 months, depending on the species and/or plant community.
The geographic patterns of phenotypic variation in leaf morphology traits were studied in the mangrove Avicennia marina (Forsk.) Vierh. in tropical Queensland, Australia, to determine whether discrete subpopulations could be recognised in the field. Significant differences in the various leaf characters occurred among the sites, which were not explained by longitude or latitude, nor by inter-site distances. Hierarchical cluster analysis of the estimated site means showed no coherent geographical groupings of the sites, suggesting that site populations do not follow a differentiation by distance model. Principal component analysis showed that site groupings with consistent leaf morphological characteristics could be identified, suggesting the A. marina occurs as widely scattered discrete subpopulations, and that phenotypic structuring occurs over quite short (<100>km) distances. Evidence from other studies suggests this phenotypic structuring reflects underlying genetic diversity, and it implies that a conservative approach to sourcing plant material for mangrove restoration projects would be appropriate.
Fourier analysis was used to demonstrate distinctive seasonal patterns of leaf litter fall in the mangrove species Rhizophora apiculata, R. stylosa and R. lamarckii. Similar treatment of data for stipule fall was not successful, indicating that this process may be controlled by random events. The fall of leaves and reproductive parts appears to be correlated with climatic factors, notably rainfall, in a fashion that varies with species. Seasonal trends without Fourier analysis are described for Sonneratia alba, Bruguiera gymnorrhiza, B. parviflora, Avicennia sp. and Ceriops tagal in terms of leaves and reproductive parts, and for leaves only in Excoecaria agallocha, Xylocarpus granatum, Heritiera littoralis, Lumnitzera racemosa and L. littorea.
As part of the Global Observation Research Initiative in Alpine Environments program, the relative contribution of abiotic variables in explaining alpine vegetation was determined for five summits on a spur of Mount Clarke in the Snowy Mountains, Australia. The composition of vascular plant species and life-forms, and topography were determined, and soil nutrients and soil temperature were measured on each aspect of each summit by standardised methods. Ordinations were performed on the composition of vascular plant species and life-forms, topography, soil nutrients and soil temperature-derived variables. Abiotic variables were tested against the biotic dissimilarity matrices to determine which were best correlated with current plant composition. Summits differed in plant composition, with a decrease in the cover of shrubs, and an increase in herbs and graminoids with increasing altitude. Altitude was the main determinant of species composition, accounting for more than 80% of the variation among summits. Soil temperature variables accounted for more than 40% of the variation in composition among summits. Soils were not significantly different among summits, although certain soil variables, principally calcium, were important in predicting plant composition. Because temperature is correlated with current vegetation on these five summits, predicted increased temperatures and decreased snow cover are likely to affect future plant composition in this mountain region. Yes Yes
The effect of ongoing forest invasion on floristic composition of subtropical montane grasslands was considered by examining vascular plant species frequencies across 13 adjoining areas of grassland, invaded grassland (eucalypt forest <50 years old) and eucalypt forest (>50 years old) on the Bunya Mountains in subtropical eastern Australia. Tree invasion of grasslands over the last 50 years has had substantial facilitative or antagonistic net impacts on populations of many plant species. Increases in species frequency, indicating net facilitation, generally appear to occur earlier in forest development than do decreases in frequency, indicative of net antagonism. Although more than 20% of the flora showed substantial association with either grassland or forest, the dominant ground-stratum species in each habitat were quite similar and very few grassland species were not recorded in grassy forests. Forb species composition appears to change more rapidly after tree invasion than grass species composition. Relatively few forbs preferred forest to grassland, whereas shrubs, trees or lianes were substantially more frequent in forests. Replacement of grasslands by grassy forests would reduce landscape diversity and impact on other values in the Bunya Mountains. However, this study suggests that most, if not all, vascular plants that currently occur on the grasslands will persist in the area provided the grassy character of the eucalypt forests is maintained.
Although the salinisation of streams has long been recognised as one of Western Australia's most serious environmental and resource problems, there is very little published information on the effects of salinisation on riparian flora and fauna. We studied riparian vegetation in three experimental catchments on the Collie River in Western Australia. The catchments are situated within a 5-km area of state forest and are geologically and botanically similar, but differ in the extent of clearing, groundwater levels and stream salinity. In each catchment, transects were taken perpendicular to the direction of streamflow, and 4-m<sup>2</sup> quadrats taken along each transect. Within each quadrat, soil salinity was measured, all plants were identified to species level and percentage cover estimated. The catchments differed significantly in soil salinity, with salinity being greatest in the most extensively cleared catchment and increasing towards the floor of the valley. Plant-species richness, species diversity and species composition were significantly related to soil salinity, both among catchments and among quadrats within the most extensively cleared catchment. Plant-species richness and diversity decreased with increasing soil salinity, an effect that may be partly due to a decline in perennial herb and shrub species. This may have an impact on other components of the riparian ecosystem.
The fungicide phosphite was shown to affect pollen fertility in a range of perennial species from the south-west of Western Australia. Phosphite was applied to perennial species of the jarrah (Eucalyptus marginata) forest by spraying to run-off with 2.5, 5 and 10 g L<sup>-1</sup> phosphite in either autumn or spring. Pollen fertility of Dryandra sessilis was reduced by phosphite for up to 35 and 60 weeks after spraying in spring or autumn, respectively. Trymalium ledifolium pollen fertility was reduced by phosphite 38 and 61 weeks after spraying in spring or autumn, respectively. Lasiopetalum floribundum was less affected with a reduction in pollen fertility being observed for up to 3 weeks after spraying in spring. Other perennial understorey species of the jarrah forest, Adenanthos barbiger, Boronia cymosa, Hovea elliptica and Phyllanthus calycinus were also shown to have reduced pollen fertility after treatment in autumn or spring, as did Comesperma calymega, Eremaea astrocarpa and Hibbertia hypericoides, species of the northern sandplains when sprayed in summer.
The spatial distribution of Phytophthora cinnamomi Rands at seven dieback sites in the jarrah (Eucalyptus marginata Donn. ex Smith) forest of Western Australia was determined by the following two baiting techniques: in situ baiting with live Banksia grandis Willd. seedlings and ex situ baiting of sampled soil and root material. Four areas within each site were sampled, reflecting dieback age and position in the landscape. Approximate dieback ages of 50, 20 and 5 years were determined by aerial photography. The 50-year-old age class was divided into wet valley floor and dry gravelly slope. Phytophthora cinnamomi was recovered most frequently from the 5-year-old (dieback fronts) and wet 50-year-old areas by both baiting techniques. It was recovered from more than twice as many areas and about five times as many samples when in situ B. grandis baits were used compared with ex situ soil and root baiting. Almost all recoveries from in situ baits were made between October and December. From both methods, it appears that P cinnamomi has a patchy distribution within dieback sites in the northern jarrah forest. It is easily detected only on dieback fronts and wet valley floors. On dry gravelly sites affected 20 years or more ago, P. cinnamomi is rare and may even be absent at some sites. This makes confident detection of the pathogen difficult. In situ baiting at least allows a temporal component to the sampling and will be a useful method of detection in areas where P. cinnamomi is rare or transient.
Rainforest, ecotone and eucalypt forest species were grown for 22 weeks in glasshouse conditions under light, water and nutrient treatments. Plant biomass, leaf area and leaf biomass per plant increased in Eucalyptus sieberi, Eucalyptus fastigata, Pittosporum undulatum, Callicoma serratifolia, Elaeocarpus reticulatus, Backhousia myrtifolia and Ceratopetalum apetalum at high irradiance (1230-1670-mu-mol PAR m-2 s-1). Both E. sieberi and E. fastigata inhabit the relatively high light environments of northern aspects, upper southern aspects and ridge tops in the gully systems of south coastal New South Wales. Callicoma serratifolia, P. undulatum and E reticulatus are pioneer species of the ecotone around rainforest patches, and B. myrtifolia and C apetalum are rainforest canopy species. Mean plant biomass under high irradiance was ranked: eucalypt species > ecotone species and B. myrtifolia > C. apetalum. At low irradiance (200-530-mu-mol PAR m-2 s-1) the trend observed was reversed where rainforest canopy and ecotone species produced greater plant biomass. Plant response to different water and nutrient treatments under glasshouse conditions showed that, while the light environment primarily governed plant response, interaction between treatments occurred which resulted in maximum plant biomass at relatively high levels of soil moisture and nutrients. Carbon partitioning was used as an indication of relative response to light treatments. The proportion of plant mass partitioned to leaves did not change between experimental treatments. The magnitude of the response of leaf area ratio and specific leaf weight to light treatment, however, was ranked: eucalypt species > ecotone species > rainforest canopy species. This suggested that species naturally growing outside the rainforest canopy maximised leaf area in proportion to plant mass for a given irradiance, presumably to maintain high growth rates.
Recent global revisions have failed to resolve difficulties in identification of the Australian Rhizophora. Presented is a field key and detailed specific descriptions of the four species found in the north-east. Classificatory analyses revealed the distinct nature of the entities and some of their associations with each other.
Seeds of the endemic Western Australian species Diplopeltis huegelii Endl. were successfully germinated after the presence of combinational dormancy was identified, following the observation of selected seed characteristics. D. huegelii seeds were found to have large, fully developed, peripheral coiled embryos (with no endosperm) that are 7–8 mm long when uncoiled. Seed-coat dormancy was overcome by dipping seeds in hot water for ≥15 s, but seeds also required a period of after-ripening before they would germinate readily. After-ripening occurred while intact seeds were stored dry at ambient laboratory conditions for 13 months or when scarified (hot-water treated) seeds were stored at 13, 23 or 50% RH at 23°C for 6 weeks. Scarified 13-month-old seeds germinated readily at 7/18, 13/26 and 18/33°C in a 12-h photoperiod and in constant darkness, whereas scarified 1-month-old seeds germinated to ≤43%. Thus, seed dormancy in this species is caused by a water-impermeable seed coat (physical dormancy, PY) and a (non-deep) physiologically dormant embryo (PD), i.e. combinational dormancy (PY + PD). This is only the second report of combinational dormancy in seeds of Sapindaceae and the first report in this family of the PD component of (PY + PD) being broken during dry storage.
Natural variation in longevity among populations of the same species, and between species and genera was investigated to inform seed-collection strategies. Seed longevity for 30 wild Australian populations was measured with a controlled ageing test. The populations were represented by eight species from three genera, namely Minuria (Asteraceae), Wahlenbergia (Campanulaceae) and Plantago (Plantaginaceae), each collected from up to eight different locations. Seedsurvival curves were fitted by using the equation v =Ki + p/s, which allowed comparison of the initial population viability (Ki), the population distribution of seed life spans (s), and mean seed longevity (P50, calculated as Kis). At a genus level, the average P50 indicated that M. integerrima (DC) Benth. is the longest-lived, Wahlenbergia is intermediate and Plantago is the shortest-lived. However, there was also variation in P50 values among populations of most species. Some species had the same s value for all populations, e.g. all eight populations of W. communis Carolin had the same s value, with the differences in Ki causing the variation in P50. This consistency in s existed even though seedlots were collected from diverse locations, with mean annual rainfall ranging from 180 to 840 mm. In comparison, for the six seedlots of W. gracilis (G.Forst.) A.DC., a large difference in s as well asKi led to the variability in P50, with some indication of a possible correlation between annual rainfall and P50 or s in some species. A relationship between variation in s and the breeding system is proposed for Wahlenbergia. The data show that it can be risky to expect accurate prediction of seed longevity for a wild species on the basis of survival data from a single collection.
Nothofagus moorei (F. Muell.) Krasser has a disjunct and narrow distribution in south-eastern Australian cool temperate rainforest. To assess the conservation-genetic priorities for this species, the genetic diversity of 20 populations sampled from the largest remnant patches at northern and southern distributional extremes, the McPherson and Barrington ranges (a total of 146 individuals), was investigated by using inter simple sequence repeats (ISSR). Regeneration in northern regions of N. moorei has been documented to be predominantly by vegetative means, but our results indicate little evidence of clonality outside the multi-stemmed rings of trees. In addition, genetic diversity was considerably higher in the northern (McPherson, h = 0.1613) than in the southern range (Barrington, h = 0.1159), and genetic differentiation was significantly positively correlated with geographic distance in the former region, but not the latter. Total intraspecific variation was moderate, as measured by Shannon's diversity index, I = 0.2719, and Nei's gene diversity, h = 0.1672, and is considered at the high end of spectrum for estimates of narrow endemic species. An analysis of molecular variation indicated that the majority of genetic variation is partitioned among individuals within population (60%; P < 0.001), rather than among populations within regions (10%; P < 0.001). However, a large and significant component of the measured diversity was partitioned between northern and southern regions (29%; P < 0.001). Several hypotheses are outlined to explain these differences and management implications are discussed. However, given the narrow range, poor dispersal mechanism and restriction to cool temperate rainforest, the continued existence of N. moorei is most threatened by environmental instability and habitat loss resulting from global climate change. In this context the northern regions of the species are most at risk and extinction of such populations would lead to a significant loss of genetic variation for the species as a whole.
An efficient regeneration protocol based on organogenesis from cotyledon explants and suitable for gene delivery has been developed for an Australian passionfruit hybrid. Multiple shoots were regenerated from 30-day-old cotyledon explants on Murashige and Skoog (MS) medium containing 6-benzylvaminopurine (BAP) and coconut water. Media pulsing experiments were conducted to investigate the effect on organogenesis of exposure time of the explants to MS containing 10 mu M BAP and 10% (v/v) coconut water, i.e. passionfruit regeneration medium (PRM). Continuous exposure of these explants to PRM maximised the number of shoots produced to 12.1 per explant. However, periods on hormone-free medium improved the appearance of the shoots and increased the number of explants with shoots from 75 to 84.6%. Further, shoots exposed for 7 days to half-strength MS supplemented with 10 mu M NAA (1-napthalene acetic acid) produced twice as many plantlets than those on half-strength MS alone. Transient GUS histochemical assays indicated delivery of the uidA gene via Agrobacterium tumefaciens.