bluuebunny/crossref_metadata_2025 huggingface dataset:
Fusarium oxysporum f. sp. cubense inoculation and hypoxia alter peroxidase and phenylalanine ammonia lyase activities in nodal roots of banana cultivars (Musa sp.) differing in their susceptibility to Fusarium wilt
Authors: Aguilar E. A. , Turner D. W. , Sivasithamparam K.
Published: December 2005

The impact of O2 deficiency on the interaction of banana
roots and the Fusarium wilt pathogen, Fusarium oxysporum
f. sp. cubense (Foc), was determined on the basis of
changes in the activities of enzymes involved in phenol metabolism
(phenylalanine ammonia lyase, PAL, and peroxidase, PER). The root systems of
banana cultivars differing in their known field resistance to Fusarium wilt
were either inoculated with Foc or not and either continuously aerated,
continuously exposed to hypoxia, or exposed to hypoxia for 48 h and then
reaerated.
Hypoxia stimulated PAL and PER activities in nodal roots of bananas and Foc
inoculation stimulated PER activity. Hypoxia, in the presence of Foc, affected
PAL activity among cultivars in a manner consistent with their observed field
resistance to Fusarium wilt. Foc inoculation increased PER activity in all
cultivars over and above that caused by hypoxia alone. Foc inoculation,
followed by hypoxia, affected the cultivars differently, with the
corresponding changes in PER activity seemingly correlated with their
resistance to Fusarium wilt.
The resistant cultivar Goldfinger has an inherently higher capability of
stimulating the production of PAL and PER enzymes than cv. Williams (normally
resistant to Fusarium wilt but succumbs when waterlogged) or cv. Gros Michel
(susceptible). While Williams could respond to hypoxia by increasing PAL and
PER activities more than Gros Michel, the elicited level of activity may not
be enough to prevent disease development under waterlogged conditions. While
hypoxic treatment might be a way to stimulate the root’s defence
mechanism, it has to be at a level, duration and timing that would enhance PER
and PAL activities without causing irreparable damage to root functions.
Postanoxic injury, for example, could impair host resistance to wilt.
The differences in rapidity and degree of increase in PAL and PER activities
under Foc inoculation, followed by hypoxia, appear to be associated with
resistance to Fusarium wilt. The breakdown in resistance of Williams (a
Cavendish cultivar) observed during waterlogging, needs further investigation,
especially if PAL is synthesised in the more aerated parts of the root, away
from the stele where the defence mechanism needs to operate.
What determines the number of seed produced in a flowering event? A case study of Calyptrogyne ghiesbreghtiana (Arecaceae)
Authors: Cunningham Saul A.
Published: December 2005

Calyptrogyne ghiesbreghtiana Linden ex. H. Wendl. is an
understorey palm that occurs at La Selva Biological Station, Costa Rica. In
this paper I combine analysis of natural variation and results of experimental
manipulations to ask (1) what limits seed production? and (2) what processes
cause variation in seed production by
C. ghiesbreghtiana? The number of seed produced per
inflorescence ofC. ghiesbreghtiana was limited
substantially by the loss of female flowers to floral herbivores. Much
variation in the number of seed produced perinflorescence of
C. ghiesbreghtiana was due to losses of developing
fruits to predators. Together these phenomena illustrate the influential role
of natural enemies in the reproductive success of this plant. Seed-set
efficiency (number of seeds/number of female flowers) was highly variable
in this species, and such high levels of variation appear to be common in
other species. For species with highly variable seed-set efficiency, the role
of resource allocation to flower production in determining differences in seed
production among individual plants is likely to be relatively small.
Quantitative genetic evidence that the timing of vegetative phase change in Eucalyptus globulus ssp. globulus is an adaptive trait
Authors: Jordan Gregory J. , Potts Bradley M. , Chalmers Paula , Wiltshire Robert J. E.
Published: December 2005

Quantitative genetic analysis of six field trials suggests a complex pattern
of adaptive significance for the timing of the abrupt change in leaf form in
Eucalyptus globulus Labill. spp.
globulus. Data from one small trial demonstrated a
genetic basis to a steep local cline in habit, in the size of plants flowering
and in the height of the change in foliage type. Thus, slow growth, early
phase change and precocious flowering appear to be maintained in exposed
coastal environments by current selection. This contrasts with results from
five large trials that contained open-pollinated progeny from across the whole
geographic range of this taxon. On this broad scale, early phase change
appears to promote growth, a fitness surrogate, in two trials but not the
others, implying differential selection for the timing of phase change. In
these cases, early phase change may have been favoured in warm, wet
environments by reducing damage by leaf fungi. There was marked genetic
variation in the timing of vegetative phase change among broad regions,
consistent with either adaptation to broad-scale environmental variation or
historical differentiation.
The Distributions, Dynamics and Ecological Differentiation of Callitris Species in Tasmania
Authors: Harris S , Kirkpatrick JB
Published: December 2005

Callitris oblonga and C. rhomboidea are the only gymnosperms found in the drier parts of Tasmania, where they have marginally overlapping and internally highly disjunct distributions. There is virtually no overlap in their periods of pollen production. Consequently, apparent hybrids are extremely rare. C. oblonga, a Tasmanian endemic, is largely confined to riverine vegetation in the dry cast and centre of the State. C. rhomboidea occupies well drained sites along parts of the east coast, where it is capable of regenerating continuously without major disturbance, or phasically after fire or other major devegetating events. Areas topographically, edaphically and climatically well within the ranges of the two species have no populations of either suggesting that neither species occupies its potential range in Tasmania. Morphological and physiological characters, such as form and frost resistance, reflect the local and regional environment occupied by the two species.
Effects of Fuel-Reduction Burning on a Eucalyptus obliqua Forest Ecosystem in Victoria
Authors: Hamilton SD , Lawrie AC , Hopmans P , Leonard BV
Published: December 2005

An autumn fuel-reduction burn of low intensity (200-250 kW m-1) was performed in a Eucalyptus
obliqua forest near Gembrook, Victoria. The aim of the study was to evaluate the effect of a single
burn on floristics, biomass, N content and N2 fixation. The fire burnt 50% of the area in a mosaic
pattern, significantly reducing understorey vegetation cover (by 90%) and plant density (by 70%) in
burnt areas immediately after the fire. Understorey cover was restored to 40% of the original value
1 year later, but 33% of the understorey species were still absent from burnt areas. In the whole site
mosaic, biomass declined by 30 t ha-1 (3 kg m-2) (10%) and N content by 100 kg ha-1 (10 g m-2)
(18% excluding soil N, 2% including soil N). These losses were due to significant losses of biomass
and N from the understorey only (88%, 85%), standing dead trees (57%, 62%), fallen wood (73%,
60%) and litter (69%, 70%). One year later, there was no significant increase in either biomass or
N content. Burnt areas had five times the total nitrogenase activity of unburnt areas, owing to significantly
greater specific nitrogenase (C2H2 reduction) activity, three times the nodule weight and 20 times the
plant density of unburnt areas for the dominant legume (Pultenaea scabra). Using a calibration ratio
for C2H2:N2 of 2.68 :1 derived from glasshouse growth studies, N2 fixation for P. scabra was estimated
as 15 g ha-1 year-1 in burnt areas and 3 g ha-1 year-1 in unburnt areas, with a mean of 9 g ha-1
year-' for the whole site mosaic. Adding superphosphate to burnt areas increased estimated N2 fixation
significantly by 14%, mainly by increasing nodulation. Losses of N due to the burn (100 kg ha-1)
were considerably greater than gains from increases in N2 fixation (6 g ha-1 year-1) one year after
the burn. Even allowing for N2 fixation by other, infrequent legumes and greater N2 fixation in subsequent
years, these data suggest that the N lost in the burn is more likely to be replaced by inputs from
soil reserves and rainwater than from N2 fixation by legumes.
Temperature and Light Effects on the Germination of Seven Native Forbs.
Authors: Willis AJ , Groves RH
Published: December 2005

Seeds of seven native herbaceous species common in natural grasslands and woodlands of south-eastern
Australia were tested for germination over a range of alternating temperatures (15/5-35/25°C) with
and without light. Seeds were also exposed to low (4°C) and high (50/40°C) temperatures and the
addition of gibberellic acid. Tests were conducted on seeds stored for 0-15 months at room temperature.
The optimum temperature for germination differed among species, with only Helipterum albicans
germinating maximally over all temperatures. Germination of Bulbine bulbosa seed was the most strongly
temperature-dependent. Light and cold treatments promoted germination in Helipterum albicans and
Vittadinia muelleri only. Short-term dormancy (3-4 months) was shown to occur in fresh seeds of
Stylidium graminifolium, Helichrysum apiculatum and Wahlenbergia stricta, but not in seeds of the
other species; addition of gibberellic acid to seeds of the two last-named species did not overcome
that dormancy. Seeds of all species remained germinable after 15 months of storage. Seeds of most
species germinated maximally at 20/10°C. Storage at high alternating temperatures for 1 month inhibited
subsequent germination at 30/20° in Leptorhynchos squamatus and S. graminifolium but increased
it in V. muelleri, H. albicans and H. apiculatum. In the last species, exposure of 1-month-old seeds
to high temperature broke dormancy.
These results show that germination and dormancy of seeds of a range of native forbs vary with
temperature and light regime; they provide an initial basis on which to test and interpret the effects
of seasonal factors on germination and field establishment.
Secondary Pollen Presentation in the Chamelaucium Alliance of the Myrtaceae: a Compact Substigmatic Ring in Chamelaucium
Authors: Slater AT , Beardsell DV
Published: December 2005

In Chamelaucium uncinatum (Geraldton wax), the flowers are protandrous and pollen is presented to potential pollinators on a compact ring of stylar hairs. The anthers dehisce in the bud, and the pollen which is suspended in a lipidic fluid adheres to the stylar hairs as the stamens uncurl. The style elongates after anthesis to present the stigma and pollen. The period of stigmatic receptivity and pollen viability and the developmental changes in the flower are described. The stylar hairs present the pollen, then remove it from the vicinity of the stigma prior to the period of stigmatic receptivity. The methods of pollen presentation in other species of Chamelaucium are also investigated. Stylar elongation is compared in long- and short-styled species of Chamelaucium, Darwinia, Homoranthus and Actinodium. The previous accounts of the breeding system of C. uncinatum are discussed.
Cytogenetic and Pollination Studies in the Genus Verticordia DC
Authors: Tyagi AP , Mccomb J , Considine J
Published: December 2005

Aspects of the genetic and physiological barriers to hybridisation have been assessed for the genus Verticordia which contains many species with significant potential for ornamental horticulture. The chromosome numbers of 52 species were analysed using flower buds and root tips. Previously published reports on chromosome numbers were confirmed for 21 species and new numbers reported in a further 31. Self compatibility was present in 20 species and only three species were shown to possess barriers to self pollination. Seed set occurred in two of six interspecific crosses carried out within sections. In 21 wider crosses the degree of pollen tube development was increasingly repressed with taxonomic distance. The chromosome counts also support the reclassification of the genus Verticordia into three subgenera: Chrysoma, Verticordia and Eperephes. Species within each section of a subgenus generally had the same chromosome number. Exceptions occurred in the subgenus Verticordia, sections Verticordia, Intricata and Micrantha. In species with one or two ovules, the chromosome number was also low (6, 7, 8 or 9) while species with six or more ovules had a higher chromosome number (11 or 22). There was, however, no relationship between chromosome number and chromosome size, nor between chromosome number and any observed feature which might be attributable to polyploidy or allopolyploidy. With the possible exception of V. grandis, which displayed loss of seasonality in flowering, all putative polyploids behaved developmentally as diploids and displayed a high level of male fertility.
Interaction of the Stigma With the Pollinium in Dendrobium speciosum
Authors: Slater AT
Published: December 2005

Pollination of D. speciosum is effected by the deposit of the pollinia from one flower into the stigmatic cup of a flower on another plant. The pollinia are submerged into the viscous liquid of the stigmatic cup. This liquid contains the detached stigmatic cells and mucilage. Post-pollination phenomena within this species include a more intense perianth colour and the closure of the perianth. This is followed by the swelling of the column and ovary and, after 4 days, cell division in the ovary. Following pollination the pollinia break apart as the tetrads dissociate from each other. The pollen grains progressively hydrate and germinate from the outside of a pollinium to the inside. The changes in the pollen grains associated with hydration and germination are described. The stigmatic mucilage is considered essential in the hydration and germination of the pollen. The detached cells of the stigma located near the entrance to the stylar canal are seen to lose the starch from the amyloplasts after the pollen tubes have passed. The structure of this stigmatic type is discussed in relation to its functions with the large pollen aggregate.
Distribution of Microlaena stipoides and Its Association With Introduced Perennial Grasses in a Permanent Pasture on the Northern Tablelands of New South Wales
Authors: Magcalemacandog DB , Whalley RDB
Published: December 2005

The distribution of Microlaena stipoides (Labill.) R.Br. and its association with introduced perennial grasses was studied in a 10.2-ha permanent pasture on the Northern Tablelands of New South Wales. There were 105 systematically arranged plots (2m × 2m quadrats) located in the field, and at each sampling location composition by basal cover of the perennial herbaceous species encountered was recorded using 100 points. Dominant perennial grasses identified in the field were the native M. stipoides and the introduced Lolium perenne L., Dactylis glomerata L. and Poa pratensis L. Trifolium repens L., sown in the field in 1961, was also widespread. M. stipoides was abundant throughout the paddock, although higher composition by basal cover was observed under tree canopies. Discriminant function analysis and hierarchical classification showed a tendency towards aggregation of plots dominated by M. stipoides, L. perenne and T. repens, which may indicate the stability of this combination of species. T. repens was present in almost all plots and had a similar distribution to M. stipoides; both species were quite close in the species ordination analysis and were found associated with other perennial grasses at different locations in the paddock. These species associations are probably stable and appear to be common in permanent pastures in the eastern parts of the Northern Tablelands.
The Potential of Fossil Mammal Middens as Indicators of Vegetation History in Central Australia
Authors: Berry SL
Published: December 2005

The plant macrofossil contents of two fossil mammal middens were investigated. Midden MS was collected from near Mt Swan, 200 km north-east of Alice Springs in central Australia. The vegetation in this region is predominantly grassland scattered with low trees. Midden KS was collected from Kathleen Springs, 240 km west-south-west of Alice Springs. The flora in this locality is dominated by forbs and chenopods. Midden KS had a radiocarbon age of 1700 years BP at the top and 3500 years BP at the bottom. Most of the plant taxa in each midden were components in the flora of the vegetation zones currently surrounding that midden. However, the two middens, collected from different vegetation zones, shared only 33% of taxa. Similarly, only 24% of species were common to the July 1987 vegetation at the two localities. A vertical slice of midden KS was cut into 25 subsamples. No progressive change of subsample plant macrofossil assemblage with depth could be detected by Principal Components Analysis. However, there was a weak tendency for subsamples from the same level in the midden to be similar. It was concluded that mammal middens are potentially useful indicators of the vegetation history of central Australia.
Use of Restriction Fragment Length Polymorphisms to Study Genetic Relationships Between Australian and Japanese Isolates of Phytophthora vignae
Authors: Liew ECY , Maclean DJ , Manners JM , Dawson D , Irwin JAG
Published: December 2005

The genetic relationships among 10 Australian accessions of Phytophthora vignae (Pv) isolated from cowpea, two Japanese accessions of Pv isolated from adzuki bean and one accession of Phytophthora megasperma f. sp. glycinea (Pmg) isolated from soybean were assessed using Restriction Fragment Length Polymorphisms (RFLPs). Using five high-copy probes derived from genomic libraries of Pv and Pmg, RFLP banding patterns used to calculate the genetic distance, d, between isolates, showed that Pmg was very dissimilar to Pv (d = 0.102). In contrast, a close similarity among different isolates of Pv was observed (maximum d = 0.0039), with most polymorphisms being detected using probe pPmgS63. A dendrogram showed that the Japanese and Australian isolates of Pv each belonged to different clusters, with a similar range of intracluster genetic variation between members of the Australian cluster (d range 0.0001-0.0019) compared to the Japanese cluster (d = 0.0022). Because the genetic distance separating the Australian and Japanese clusters (average d = 0.0033) was less than twice that of the intracluster distances, it is proposed that these two geographically isolated groups of P. vignae have recently been derived from a single (unknown) source, rather than each being indigenous pathogens of their respective hosts cowpea and adzuki bean.
Low-Dose Gamma-Irradiation Promotes Wheat Anther Culture Response
Authors: Ding XL , Luckett DJ , Darvey NL
Published: December 2005

This study examined the anther culture response of wheat to different doses of gamma radiation, and the interaction of radiation dose with a cold pretreatment of ears stored prior to culturing. The cultivars Grebe and Kite were chosen on the basis of their anther culture response, Grebe being highly responsive and Kite being non-responsive. Spikes of the two cultivars were exposed to various levels of gamma radiation (60Co source) ranging from 0 to 10 Gy (0.53 Gy min-1) before anthers were plated on an agarose-solidified medium. For Grebe, doses of 1, 3 and 5 Gy resulted in more embryoids, higher green plant regeneration, and a greater number of spontaneously doubled haploids (DH), than in the non-irradiated control. The response in Kite was similar but less pronounced. The higher doses of radiation (7 and 10 Gy), however, were detrimental in both cultivars and at 10 Gy no embryoids or regenerants were produced. Anthers subjected to a cold pretreatment prior to irradiation responded significantly less than those cultured fresh. This study indicated that low-dose gamma irradiation of fresh explants can significantly improve regeneration from anther cultures in wheat and may stimulate a low frequency of regeneration in an otherwise non-responsive cultivar.
Vegetative Variation of Myriophyllum variifolium in Permanent and Temporary Wetlands
Authors: Brock MA , Casanova MT
Published: December 2005

The responses of vegetative fragments of Myriophyllum variifolium J. Hooker to environmental variation in a field transplant trial are reported. Plant performance was measured as survival of plants, number of shoots and shoot length per surviving plant. Vegetative fragments from several lakes and different habitats within lakes were grown at three depths, in two regimes of disturbance by grazers and in two soils. The effect of depth was marked. Plants established and survived best on the shore (0-m depth) where their growth form was dominated by many shoots and prostrate spread. In contrast, plants in deeper water had low survival rates and surviving plants had single or few upright shoots. Separate analysis of the shore results indicated significant differences in plant performance between plants of various origin, between soil types and between regimes of disturbance by grazers. Plants originating from the deep water habitat consistently performed poorly whereas plants originating from the shore of the transplant site survived and grew well. Soil type had a major effect in the establishment phase of plant growth. Plants performed better on permanently wet basaltic soils (taken from the experimental transplant site) than on granitic soils from a temporary lagoon. The presence of grazing animals encouraged greater numbers and lengths of shoots on the shore. The role of flexibility in plant performance and vegetative reproduction in maintaining plant populations in lakes with unpredictable fluctuations of environmental conditions is discussed.
A Molecular Approach to Distinguish the Bean Rust and Siratro Rust Pathogens
Authors: Braithwaite KS , Manners JM , Maclean DJ , Irwin JAG
Published: December 2005

Rust disease on the tropical pasture legume Macroptilium atropurpureum (siratro) is caused by Uromyces appendiculatus var. crassitunicatus. This pathogen was believed to be closely related to the bean (Phaseolus vulgaris) rust pathogen Uromyces appendiculatus var. appendiculatus. The genetic relationship between these two fungi was investigated. Total DNA hybridisations indicated that little homology exists between the high copy genomic DNA of these two rust fungi. Random genomic probes cloned from the bean rust fungus detected extensive Polymorphisms between the two, with only one probe from 17 being monomorphic. The ribosomal DNA repeat unit was also distinguished by RFLPs. It was calculated from the RFLP data that the bean rust fungus and the siratro rust fungus share only 8-14% sequence homology. The results indicate that the two fungi, although morphologically very similar, are not closely related genetically.
Polyploidy and Ribosomal-DNA Spacer Variability in Poa labillardieri
Authors: May CE , Campbell MH
Published: December 2005

With changing agricultural practices, poa tussock (Poa labillardieri Steud.) has become a serious weed of Australian tableland pastures. To determine whether there are any genetic differences within the species that might have a bearing on this problem, accessions of P. labillardieri from seven localities in south-eastern Australia were grown in a field nursery at Bathurst for comparison of their morphological attributes. Seeds from plants grown in this nursery were collected, and a further generation of plants was grown in a glasshouse for cytogenetic and molecular genetic studies. In adult plants of this generation, there were three karyotypic groups with chromosome numbers varying from 2n = 4x = 28, in nonglaucous tussocks of the Upper Hunter Valley, to 2n = 8x = 56, in glaucous tussocks from the Central and Southern Tablelands, to 2n = 12x = 84, in a Victorian coastal tussock. Because the number of chromosomes present in some seedlings from Cooma parents varied from 35 to 49 to 56, diploid or hexaploid plants must also have been present in the Bathurst nursery and contributed to the odd-ploidy seedling chromosome numbers. Ribosomal spacer DNA fragments were investigated using the wheat probe pTa250.4 to label homologous DNA sequences in genomic DNA extracted from the leaves of individual plants of P. labillardieri. Although specific DNA fragments could not be linked to either localities or levels of ploidy, they did show evidence of cross-pollination between plants of the different accessions. These levels of cytogenetic and DNA sequence variability, and the evidence they provide of widespread outcrossing within plants of similar ploidy and of hybridisation between plants of differing ploidy, may well help to explain the success of this species as a weed and affect the control measures used to stop its spread.
Effect of Low Temperature on Floral Induction of Eucalyptus lansdowneana F. Muell. & J. Brown subsp. lansdowneana
Authors: Moncur MW
Published: December 2005

Transferring seedlings of Eucalyptus lansdowneana from a heated glasshouse (24/19°C) to a cold
glasshouse (15/10°C) for 5 or 10 weeks and back to the heated glasshouse was sufficient to induce
floral buds. Bud production was further enhanced when seedlings were transferred to cold conditions
during periods of high solar radiation. Under low levels of solar radiation and short duration of cold,
0-5 weeks, plants reverted to vegetative development, suggesting a low floral induction stimulus. Seedlings
that produced a visible floral inflorescence had fewer leaves than seedlings grown under similar conditions
that had not produced an inflorescence. This was more noticeable under high-radiation conditions.
Plants grown under outside conditions in Canberra and transferred to a heated glasshouse (25/
18°C) during winter initiated inflorescences 7-9 weeks earlier than plants grown continuously outside.
The early initiation enabled buds to develop and flower before the onset of the following winter. More
buds were initiated in plants transferred to the glasshouse in September compared with 16 June or
28 July. Plants transferred on 16 June initiated few buds or none at all. These plants may have been
in a juvenile or transitional stage of development, experienced insufficient cold for full induction or
been limited by the low winter irradiances.
Floral response occurred under both long days (phytotron) and short days under outside conditions
in Canberra, suggesting that E. lansdowneana may well be relatively insensitive to day length. These
results are discussed in relation to controlled breeding programs which aim to manipulate flowering
time and duration to decrease the generation interval.
Pericarp Anatomy and Systematics of the Simaroubaceae sensu lato
Authors: Fernando ES , Quinn CJ
Published: December 2005

Descriptions are given of the anatomy of the pericarp in representatives of 28 genera of the Simaroubaceae sensu lato, including Stylobasium, as well as the ontogeny of the endocarp in 9 of them. There is marked heterogeneity in the family in both pericarp structure and endocarp ontogeny. Eight different endocarp types are recognised, the distribution of which shows considerable correlation with the subfamilial classification of Engler. This study provides further evidence that the family in the broad sense is an artificial assemblage. Endocarp structure provides support for the inclusion of both Recchia and Stylobasium in the Surianoideae. Guilfoylia has no recognisable endocarp; the occurrence of periclinal divisions within the inner protoderm of young pericarps suggests that this is a derived condition. The inclusion of Allantospermum and Nothospondias within the Irvingioideae and Simarouboideae respectively is not supported by their pericarp structures.
Resource Allocation to Asexual Gemma Production and Sexual Reproduction in South-Western Australian Pygmy and Micro Stilt-Form Species of Sundew (Drosera spp, Droseraceae)
Authors: Karlsson PS , Pate JS
Published: December 2005

Proportional allocations of current total dry matter (DM), N and P to early season asexual gemma production and late-season flowering and seed production were compared for eight pygmy rosette form and three micro stilt-form perennial pygmy sundews (Drosera spp.) in native habitat in south-western Australia. Mean allocations to gemmae for the smaller rosette species were 22% for DM, 60% for N and 38% for P versus 8, 20 and 23% (DM, N, P) respectively for the micro stilt forms. Allocations to mature fully formed seeds were extremely low, 1-8, 4.0 and 5.4% (DM, N, P) for the rosette forms, 0.7, 3-0 and 2.3% respectively for the micro stilt forms. The above values reflect the heavy bias towards gemma production, (8-52 propagules per plant per season across the 11 species) as opposed to that for seed (0-8 fully formed seeds per plant per season). Comparable information for the annual nongemmiferous pygmy sundew D. glanduligera showed end of season allocation of 66, 37 and 29% (DM, N, P) of total plant resource to inflorescences minus seeds, and additional amounts equivalent to 30, 59 and 69% to the 60 seeds produced per plant of this species in the study season. A detailed phenology of resource allocation across a full season of growth in second, third and fourth season plants of the rosette perennial D. closterostigma showed net seasonal losses in the total vegetative resource of N and of P in older plants attributable to apparent over commitment to asexual reproduction during the season of study.
Patterns of Genetic Diversity and Nature of the Breeding System in Melaleuca alternifolia (Myrtaceae)
Authors: Butcher PA , Bell JC , Moran GF
Published: December 2005

Melaleuca alternifolia (Maiden & Betche) Cheel is harvested from natural stands and plantations for production of Australian tea-tree oil. Genetic variation was examined and outcrossing rates estimated to provide baseline information for breeding and selection programs. The overall genetic diversity (HT = 0.186) is comparable to other regionally distributed Australian tree species. There was a general trend for more isolated populations to have less genetic variation than populations from the centre of the species distribution. The level of differentiation among populations was low (12%), associated with a high outcrossing rate (93%) and high levels of gene flow. Geographic separation of Queensland and New South Wales populations corresponds with genetic distance measures.
Seed Production and Litter Fall in Some Eucalypt Communities in Central Queensland
Authors: Burrows DM , Burrows WH
Published: December 2005

Seed production and litter fall were studied for seven woodland communities, dominated by Eucalyptus spp., in central Queensland. Seed and capsule fall are usually completed between annual flowering periods, for each of the Eucalyptus spp. studied. A pattern of light and heavy seed production is common over different years. Annual seed yields up to 20 kg ha-1 (or c. 49 million seed ha-1) were estimated over the varying 1-3-year study periods. Litter fall followed expected trends, ranging from 900 to 2700 kg ha-1 year-1, with peak production in the warmer months. These litter yields, coupled with understorey grass production, could provide adequate fuel for a ground fire to occur in most years. The implications of these findings for woodland management under pastoral use are discussed.
CO2 × Nitrogen Interaction on Seedling Growth of Four Species of Eucalypt.
Authors: Wong SC , Kriedemann PE , Farquhar GD
Published: December 2005

Four eucalypt species were selected to represent two ecologically disparate groups which would be expected to contrast in seedling vigour and in the nature of growth responses to CO2 × nitrogen supply. Eucalyptus camaldulensis and E. cypellocarpa were taken as examples of fast-growing species with a wide distribution, that develop into large trees. By contrast, E. pauciflora and E. pulverulenta become smaller trees, and show a more limited distribution. Seedlings were established in pots (5 L) of a loamy soil and supplied with nutrient solution containing
either 1.2 or 6.0 mM NO3- in both ambient (33 Pa) and CO2-enriched (66 Pa) greenhouses. Analysis
of growth response to treatments (2 × 2 factorial) was based on destructive harvest of plants sampled
on four occasions over 84 days for E. carnaldulensis and E. cypellocarpa, and 100 days for E. pulverulenta
and E. pauciflora.
A positive CO2 × N interaction on plant dry mass and leaf area was expressed in all species throughout
the study period. In E. carnaldulensis and E. cypellocarpa, plant mass was doubled by high N at
33 Pa CO2, compared with a three to four-fold increase at 66 Pa to reach 34g by final harvest. In
E. pulverulenta and E. pauciflora, slower growth resulted in about 50% less mass at a given age, but
relative increases due to CO2 and N were of a similar order.
A distinction can be made between N and CO2 effects on growth processes as follows. When trees
were grown on low N, elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf and whole
plant levels. On high N, leaf NUE was increased in E. camaldulensis and E. cypellocarpa, but decreased
in E. pulverulenta and E. pauciflora. Whole plant NUE showed no consistent response to elevated
CO2 when plants were supplied high N.
Net assimilation rate (NAR) was increased by elevated CO2 in all species on either N treatment.
Moreover, high N increased NAR under either CO2 treatment in all species. There was a positive
N × CO2 interaction on NAR in E. carnaldulensis and E. cypellocarpa, but not in E. pulverulenta
and E. pauciflora.
Growth indices for E. carnaldulensis and E. cypellocarpa species, and especially E. carnaldulensis,
generally exceeded those for E. pulverulenta and E. pauciflora in terms of NAR, leaf NUE, N-enhancement
of CO2 effects on leaf area and biomass, and non-structural carbohydrate content of foliage.
A Functional Scheme for Predicting the Outbreak Potential of Herbivorous Insects Under Global Atmospheric Change
Authors: Landsberg J , Smith MS
Published: December 2005

There are many possible ways in which changes in the global atmosphere could influence the outbreak potential of herbivorous insects; we clarify these by developing a scheme for analysing insect populations in terms of functional attributes that are both important in population regulation and responsive to global change. This analysis shows that elevated CO2 is not likely to have a major influence on probability of insect outbreak, except possibly in systems in which nitrogen-based defensive compounds are produced by plants in response to herbivory. Systems that will have high potential to outbreak, if climatic conditions become more favourable for plant growth and responses are not constrained by other resources, include those in which both herbivorous insects and host plants have highly flexible growth patterns and activity cues. Global changes that increase environmental stress on host plants are most likely to favour sap-feeding insects. Critical enemy (predator or parasitoid) control of the dormant phase of herbivorous insects may be very important in preventing or allowing outbreaks, but is often poorly understood.
Modelling the Environmental Niche of Plants: Implications for Plant Community Response to Elevated CO2 Levels.
Authors: Austin MP
Published: December 2005

No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant communities in response to elevated CO2. However indirect effects of CO2 via temperature increases can be tested by reference to natural analogues. Physiologists, vegetation modellers of climate change and community ecologists assume very different temperature responses for plants. Physiologists often assume a skewed non-monotonic curve with a tail towards low temperatures, forest modellers using FORET type models, a symmetric curve, and community ecologists a skewed response with a tail towards high temperatures. These assumptions are reviewed in relation to niche theory, and recent propositions concerning the continuum concept. Confusion exists between the different approaches over the shape of response curves to temperature. Distinctions need to be made between responses due to growth (physiological response), potential fitness (fundamental niche) and observed performance (realized niche). These types of response should be quantified and related to each other if process-models are to be tested for predictive success by reference to naturally occurring communities and temperature gradients. An example of a statistical method for quantifying the realized environmental niche response of a species to temperature is provided. It is based on generalised linear modelling (GLM) of presence/absence data on Eucalyptus fastigata for 8377 sites in southern New South Wales, Australia. Seven environmental variables or factors are considered: mean annual temperature, mean annual
rainfall, mean monthly solar radiation, topographic position, rainfall seasonality, lithology, and soil
nutrient status. The temperature response is modelled with a β-function, logy = a + α log ( t - a ) + δ log
( b - t), where t is temperature and letters are parameters. The probability of occurrence is shown to be a
skewed function of mean annual temperature. Any process-models of climate change for vegetation
incorporating temperature changes due to elevated CO2 must be capable of generating such realised
environmental niche responses for species.
Potential CO2-Enhanced Carbon Storage by the Terrestrial Biosphere
Authors: Polglase PJ , Wang YP
Published: December 2005

Geochemical models that deduce latitudinal source/sink relationships of atmospheric CO2 suggest that, in tropical regions, there is almost zero net exchange of CO2 between the atmosphere and the terrestrial biosphere. The implication is that CO2-enhanced carbon storage (CO2-ECS) by tropical biomes is negating the output of CO2 from deforestation. We describe here a 10-biome model for CO2-ECS, in which carbon accumulation in living vegetation is coupled to the Rothamsted soil carbon model. A biotic growth factor (β) was used to describe the relationship between literature estimates of net primary production (NPP) and atmospheric CO2 concentration. Using β = 0.3 as a reference state, CO2-ECS by the global biosphere in 1990 was 1.1 Gt. When more appropriate values of β were used (derived from a theoretical response of vegetation to increasing temperature and CO2), CO2-ECS was 1.3 Gt, of which tropical biomes accounted for 0.7 Gt. There are many uncertainties in this (and other) models; total CO2-ECS is particularly sensitive to changes in NPP. Unless published surveys have underestimated tropical NPP by a factor of about 2, then it is unlikely that CO2-ECS could have negated the 1.5-3.0 Gt of carbon that are estimated to have been emitted by tropical deforestation in 1990.
Challenges in Linking Atmospheric CO2 Concentrations to Fluxes at Local and Regional Scales
Authors: Raupach MR , Denmead OT , Dunin FX
Published: December 2005

We describe relationships between atmospheric CO2 concentration variations and CO2 source-sink distributions, at two important scales between the single plant and the whole earth: the vegetation canopy and the atmospheric planetary boundary layer. For both these scales, it is shown how knowledge of turbulence and scalar dispersion can be applied to infer CO2 source-sink distributions or fluxes from concentration measurements. At the canopy scale, the turbulent transfer of CO2 and other scalars is non-diffusive close to any point source or sink in the canopy, but diffusive at greater distances. This distinction leads to a physically tenable description of turbulent transfer, and thence to an 'inverse method' for finding the vertical profiles of sources and sinks in the canopy from measured concentration profiles. The method is tested with data from a wheat crop. At the scale of the planetary boundary layer, we consider the daily CO2 concentration drawdown (the depression of the near-surface CO2 concentration below the free-atmosphere value) of typically 20-40 ppm. This is determined by both the regionally averaged CO2 uptake at the surface and the growth of the daytime convective boundary layer (CBL). It is shown that, for a column of air which fills the CBL and is moved across the landscape by the mean wind, the net cumulative surface CO2 flux (in mol m-2) is given to a good approximation by h(t)[Cm(t) - C+]/V, where h(t) is CBL depth, Cm(t) the CO2 concentration in the CBL column in mol mol-1, C+ the concentration above the CBL, V the molar volume and time t is measured from the time at which Cm = C+ in the morning, typically about 0800 hours local time. The resulting CO2 flux estimates are regionally averaged over the trajectory followed by the column. This 'CBL budget method' for inferring surface fluxes is compared with direct measurements of CO2 fluxes, with satisfactory results. The technique has application to scalars other than CO2.
EXE: a Climatically Sensitive Model to Study Climate Change and CO2 Enhancement Effects on Forests
Authors: Martin P
Published: December 2005

Vegetation plays a significant role in determining the local and regional hydrology of ice-free
continental surfaces and the dynamics of the atmosphere above it. Vegetation also influences
the global climate directly by affecting atmospheric chemistry. In particular, it partially
controls the carbon cycle. In turn, vegetation is influenced by climate and changes in the
ambient concentration of CO2. This may have important consequences for agriculture and
natural resource exploitation. A formal recognition of atmosphere/biosphere interrelationships
is crucial but insufficient. Systematic investigations of the interactions between climate, plant
physiology and ecology are badly needed. In this spirit, this paper presents the results
of numerical simulations performed with the Energy, water and momentum eXchange, and
Ecological dynamics (EXE) model at a local scale over periods of 400-800 (simulation) years.
EXE constitutes a first attempt to couple a physiologically based water budget and an explicit
treatment of ecological dynamics. In principle, EXE could be forced by the output of an
atmospheric general circulation model (GCM). Within this context, the paper demonstrates
through the examples it analyses that both potential stomata1 response to CO2 and the possible
range of changes in atmospheric relative humidity are likely major factors in determining the
ecosystem response to greenhouse warming. Consequently, they should be considered in future
studies of this kind. The paper also provides explanations regarding the movement of ecotones,
defined as the transition zones between different vegetation assemblages. Taking the North
American forest/prairie boundary as a case study, the analysis of the results shows how, in a
greenhouse warmed world, St Paul, MN, might look like North Platte, NE. Finally, building
on the previous example by using two different models, this study illustrates that results can
be strongly model dependent and encourages extreme caution in their interpretation.
Leaf Demography, Sclerophylly and Ecophysiology of Two Banksias With Contrasting Leaf Life Spans
Authors: Witkowski ETF , Lamont BB , Walton CS , Radford S
Published: December 2005

Leaf demography, sclerophylly and ecophysiology were assessed on Banksia petiolaris (ground
creeper, large vertical leaves) and B. baueri (shrub, smaller horizontal leaves) in the dry mediterranean
scrub-heath of Western Australia. Leaves survived for up to 13 and 5 years respectively (50% survival
was 5.9 and 2.0 years). Leaf specific mass increased with age for both species, due to increase in leaf
density. Shading was negligible for 1-year-old B. baueri leaves but increased sharply with age, whereas
shading was moderate and similar for leaves of all ages in B. petiolaris. Transpiration rates and
stomatal conductance during cloudy autumn weather were higher in B. petiolaris, whereas
photosynthesis was lower. Stomatal conductance, transpiration and photosynthesis declined with leaf
age in both species, but more steeply in B. baueri. Dawn and midday xylem pressure potentials and
hydraulic conductance decreased with leaf age and were higher and declined more gradually in B.
Petiolaris. Water-use efficiency declined slightly with age. The water potential at zero turgor, osmotic
potential at 100% relative water content and bulk elastic modulus values were closer to zero in B.
Petiolaris and changed little with age, while the relative water content at zero turgor and bound water
were higher in older leaves of B. petiolaris. No trends in chlorophyll concentrations or fluorescence
kinetics were observed with aging except that the oldest leaves of B. baueri had lowest activity. Area based
leaf N decreased in B. baueri with leaf age, but was unchanged in B. petiolaris up to 10 years. K
and Mg did not vary with leaf age, but P decreased and Ca increased in both species. P levels were
extremely low, yet 70% resorption prior to leaf death was apparent. Photosynthetic-N and -P use
efficiencies were high in the 1-year-old relative to the 2-year-old leaves, and declined gradually with
further aging, but more steeply in B. baueri. We conclude that the exceptionally long-lived leaves of B.
Petiolaris are consistent with the substantial investment they represent (large surface area, mass and
total nutrient store) and low levels of physiological activity associated with low soil nutrient and
moisture availability and moderate illumination at all leaf ages.
Impact of Elevated Atmospheric CO2 on Biodiversity: Mechanistic Population-Dynamic Perspective
Authors: Possingham HP
Published: December 2005

Biodiversity is characteristically defined on three levels: genetic diversity, species diversity and ecosystem diversity. In this paper I consider the impact of elevated CO2 and associated climate change on the biodiversity of terrestrial systems at the species level. I attempt to understand the impact of a rapidly changing physical environment mechanistically. The direct impact of elevated CO2 is emphasised. A changing physical environment will cause behavioural and physiological responses in organisms that will affect population dynamics and interspecific relationships. In the short term, extinctions will occur via the direct interaction of species with their changing environment. Species exposed to new diseases, and species dependent on mutualists or keystone species that become extinct or change geographical range, may become extinct rapidly through interactions with other species. I hypothesise that the effect of environmental change on competitive interactions will play a minor role in causing declines in biodiversity. Existing literature on the impact of climate change on terrestrial ecosystems emphasises the way in which ecosystems and species should track suitable climates across the landscape. Here I argue that each species will be affected in one, or a combination, of the following ways: range change to track shifting climate zones, tolerating the environmental change, microevolutionary change, and extinction.