bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-aggressive Strains of the Blackleg Fungus, Leptosphaeria maculans, Are Present in Australia and Can Be Distinguished From Aggressive Strains by Molecular Analysis
Authors: Plummer KM , Dunse K , Howlett BJ
Published: December 2005

Isolates of the pathogenic ascomycete Leptosphaeria maculans have been cultured from blackleg-affected oilseed rape (Brassica napus) stubble from Horsham, Victoria. These isolates are indistinguishable on the basis of morphological characters, but can be classified as either aggressive or non-aggressive by their ability to infect B. napus cultivars Midas and Westar. These aggressive and non-aggressive isolates of L. maculans can be distinguished by molecular techniques including electrophoretic karyotyping, Southern analysis of the ribosomal RNA gene repeat, Random Amplified Polymorphic DNA (RAPD) marker analysis, and pigment production. The presence of aggressive and non-aggressive strains of L. maculans in North America and Europe has been previously described. This is the first report of non-aggressive L. maculans strains isolated from B. napus in Australia.
Genetic-Relationships as Assessed by Molecular Markers and Cross-Infection Among Strains of Colletotrichum gloeosporioides
Authors: Hayden HL , Pegg KG , Aitken EAB , Irwin JAG
Published: December 2005

Morphological characterisation allows isolates of Colletotrichum gloeosporioides, Colletotrichum musae and Colletotrichum acutatum to be identified only to species level. Pathogenicity tests and random amplified polymorphic DNA (RAPD) markers distinguished a mango biotype of C. gloeosporioides from eight other isolates of C gloeosporioides obtained from five different fruit species. Using these procedures, it was also possible to distinguish C. acutatum and C. musae both from each other, and from the C. gloeosporioides isolates. In cross-infectivity studies, isolates of C. gloeosporioides displayed a wide host range with the exception of isolates from mango, which were highly virulent on mango only. Teleomorphic isolates of C. gloeosporioides were clustered together by RAPD analysis. This work has demonstrated the existence of a biotype of C. gloeosporioides which shows specialisation to mango.
Resistance of Xanthium occidentale to Colletotrichum orbiculare, a Pathogen of X. spinosum
Authors: Auld BA , Talbot HE , Radburn KB
Published: December 2005

Colletotrichum orbiculare (syn. C. lagenarium), a common pathogen of the weed Xanthium spinosum in eastern Australia, is a potential mycoherbicide for that weed. Related Xanthium spp. are resistant to the fungus, A comparison of experimental infections of X. spinosum and X. occidentale indicated that resistance in leaves of the latter included surface morphology, hypersensitive cell death and formation of lignin-like substances around leaf infections indicated by staining. Infection of stems and fruits occurred in X. occidentale through wounds but lesions continued to grow only on fruits.
Reduced Susceptibility of Roots of Safflower to Phytophthora cryptogea After Prior Adaptation of Roots to Hypoxic Conditions
Authors: Atwell BJ , Heritage AD
Published: December 2005

Safflower (Carthamus tinctorius L. cv. Gila) was grown in solution culture; the roots were inoculated with zoospores of Phytophthora cryptogea 28 d after sowing. The period for which roots were subjected to hypoxia prior to inoculation (5%(v/v) O2 in the gas stream) had a profound influence on the degree of hyphal damage to roots 8 d after inoculation. Roots exposed to hypoxia for 7 d prior to inoculation were not more than 20% necrotic 8 d after inoculation and the shoots were fully hydrated, presumably through sustained water transport by the root. Plants which were exposed to hypoxia for just 1 d after inoculation, on the other hand, developed almost total necrosis of the root system and the shoots wilted severely subsequent to infection. We propose that while short periods of hypoxia pre-dispose safflower roots to hyphal infection, a longer period of adaptation to hypoxia reverses this susceptibility. The mechanism for this protective effect, while not known, could reside in root aerenchyma formation, phytoalexin synthesis, or other metabolic and ultrastructual changes characteristic of roots exposed to low O2 conditions.
Postfire Flowering Patterns in Blandfordia nobilis (Liliaceae)
Authors: Johnson KA , Morrison DA , Goldsack G
Published: December 2005

Blandfordia nobilis Smith (Liliaceae) is a small herbaceous monocotyledon that resprouts from a rhizomatous corm after fire. The complex pattern of flowering shown in the five years following a fire in January 1987 was investigated for five populations near Sydney. This pattern was then related to concurrent changes in soil chemistry. Most (60%) plants flowered in the first post-fire flowering season (November-January), but this dropped to fewer than 20% of the plants flowering by the third or fourth season. Most plants flowered only once, but almost all plants did flower. Consequently, 35% of the flowering events were by plants that flowered only within the first year. Flowering in the first season produced more flowers per plant in that season, and was also correlated with increased chance that a plant would flower again. Repeat flowering produced fewer flowers per plant in the subsequent seasons, but multiple flowering did increase the total number of flowers produced per plant. This form of pulse flowering and short secondary juvenile period after fire seems to be typical of resprouting monocotyledons in Australia, but is much less common among resprouting dicotyledons. The pulse of flowering appears to be closely associated with changes in the soil chemistry during the post-fire period. Many of the soil attributes measured show either a characteristic decrease or increase during the 3-4 years following the fire, with a subsequent reversal in the trend. The plants thus flower prolifically during these changing soil conditions, but almost cease flowering when these changes are reversed, thereby taking advantage of soil conditions that are not available throughout most of the inter-fire period.
Inter-Specific Competition Between Seedlings of Pinus radiata, Eucalyptus regnans and Acacia melanoxylon
Authors: Bi H , Turvey ND
Published: December 2005

A replacement series experiment was carried out to determine the competitive aggressiveness of three
species, P. radiata, E. regnans and A. melanonylon towards each other at seedling stage. Seedlings of
the three species were grown at an overall density of six plants per pot for each species combination,
providing all combinations of two species from 0:6 to 6:O. In addition, seedlings were grown in pure
stands from one plant to six plants per pot for the three species. The relative crowding coefficient, the
relative yield total, the relative effects of intra- and inter-specific competition on the yield of each
species were the four indices calculated. Acacia melanoxylon was the most aggressive species,
followed by P. radiata then E. regnans. In comparison with their corresponding monoculture,
A. melanonylon in mixtures showed the smallest decrease in shoot/root ratio, whilst P. radiata had a
greater decrease and E. regnans showed the greatest reduction. The average relative yield total of
E. regnans and A. melanoxylon was close to 1 for both shoots and roots, indicating an almost complete
overlap in resource use between the two native species. The relative yield total of P. radiata and
E. regnans was 1.27 for shoots and 1.48 for roots, suggesting a possible difference in resource use between
them. The results of this experiment provide a valuable qualitative insight into the relative magnitudes of
the effects of inter- and intra-specific competition between the seedlings of the three species.
Fire and Environmental Heterogeneity in Southern Temperate Forest Ecosystems: Implications for Management
Authors: Williams JE , Whelan RJ , Gill AM
Published: December 2005

Fire is a natural part of most Australian landscapes and has an important influence on the biological productivity and biotic composition of many ecosystems. Although fire is commonly used as a management tool, the precise nature of the way it may influence productivity and biotic composition is often poorly understood and, as a consequence, its use is controversial. This paper considers the use of fire for the management of ecosystems. Specifically, the influences of fire on environmental heterogeneity and the effects these have on shaping biological productivity and biotic patterns are discussed. Heterogeneity that affects biotic response includes variation in biophysical attributes of landscapes such as topography, fire regimes and the spatial attributes of fire. Examples are used to address the interplay between fires, environmental heterogeneity and biological patterns: (1) the effects of frees on plant resource availability; (2) crown scorch in eucalypt forests; and (3) the effects of spatial variation (patchiness) within a fire on species composition. Heterogeneity should be considered explicitly in management because prescriptions devised elsewhere may not be able to be imported with confidence to all sites and the responses of the biota to fires may differ from available information. Ecological monitoring and research into the ecological effects of heterogeneity are required to provide a predictive understanding of natural systems and provide information to aid decisions about the use of fire as a management tool.
Cold-Induced Photoinhibition and Design of Shelters for Establishment of Eucalypts in Pasture
Authors: Holly C , Laughlin GP , Ball MC
Published: December 2005

Juvenile Eucalyptus polyanthemos Schau. which had been established in an open pasture, were surrounded by individual shelters made of different materials: chicken wire, white translucent plastic, and three types of shade cloth transmitting 30, 50 or 70% of incident sunlight. Air temperatures within white plastic shelters were up to 6°C above ambient air temperatures, whereas air temperatures in other shelters differed little from ambient. Irradiance was the main factor which varied between shelters. Leaves were photoinhibited over winter as shown by depression in pre-dawn Fv/Fm. The extent of that decrease in Fv/Fm was directly proportional to irradiance. Pre-dawn Fv/Fm recovered in all treatments during spring. Growth, as measured by stem elongation. occurred to a limited extent during winter, but primarily during spring. During both seasons, stem elongation was greatest in plants sheltered by 50% shadecloth. However, treatment-induced variation in stem elongation during spring was correlated with pre-dawn values for Fv/Fm measured during the previous winter. Reducing sunlight by 50% thus appeared to effect the best compromise between conflicting demands for protection from cold-induced photoinhibition during winter and for absorption of sufficient light for growth during spring.
Effects of Burning and Grazing on Sustainable Utilization of Upland Snow Tussock (Chionochloa spp) Rangelands for Pastoralism in South Island, New Zealand
Authors: Mark AF
Published: December 2005

The upland (800-2000 m) snow tussock (Chionochloa spp.) rangelands of South Island, New Zealand
have a long history of burning that pre-dates human occupation during the last millennium. Their present
extent in part reflects their ability to displace a range of woody vegetation, including forest, through
tolerance of periodic fne. Research has confirmed the general tolerance of these grasslands to fire, though
recovery of some features (e.g. biomass and flowering potential) may take more than 14 years.
Mammalian grazing, by contrast, is a recent phenomenon, associated with European settlement and
pastoralism over the last 150 years, on these mostly Crown (i.e. public-owned) lands. Such grazing,
particularly when combined with regular burning, has usually resulted in prolonged reductions in
tussock biomass, vigour and stability, as well as in the control and yield of water, potentially the most
valuable product for humans from the upland grasslands. Fire promotes vegetative growth, flowering
and seed germination within 2 years of burning. It also increases the palatability of these long-lived
dominant grasses which are vulnerable to severe grazing by introduced ruminants, especially in the
immediate post-fire recovery period when nutrients are reallocated from roots to leaf tissue.
Management constraints, particularly restriction of grazing during the post-fie recovery period, have
been inadequate to prevent continued degradation of the grasslands through weakening or displacement of
the dominant tussock grass cover and a consequent loss of stability in many areas. Under pastoralism, the
productive potential of the grasslands, together with their water, soil and nature conservation values have
generally declined. Existing pastoral practices in many areas clearly represent non-sustainable utilisation of
the rangelands for pastoralism. Recovery will be difficult and costly, both economically and socially. Some
representative areas have been formally reserved and are being monitored to serve as baseline references.
Regulation of Germination of Seed of Anigozanthos manglesii
Authors: Sukhvibul N , Considine JA
Published: December 2005

Germination of seed of Anigozanthos (Haemodoraceae) species is usually low and unreliable which hinders the propagation of sexually generated progeny, impedes plant breeding activities and their use in horticulture. This study was undertaken to investigate the basis of these germination problems. Seeds of cultivated Anigozanthos manglesii D. Don. were shown to possess two mechanisms for regulating seed germination, both of which were external to the embryo. Embryos germinated freely on excision and culture on nutrient agar. This first barrier is a physico-chemical barrier and can be eliminated by a brief treatment with 5 M KOH and less effectively by physical abrasion with 50% H2SO4 or 0.7% NaOCl. Release of this barrier was correlated with permeability to fluorescein diacetate (FDA) and this proved to be a more useful indicator of seed viability than 2,3,5-triphenyl tetrazolium chloride (TTC). The other barrier was physiological and could be eliminated by treatment with GA3 or KNO3. Treatment of A. viridis Endl., A. humilis Lindley and A. flavidus DC. with KOH or H2SO4 with or without GA(3) elicited a small, a nil or negative response showing that mechanisms of control of germination may differ between taxa. Observations on the effects of temperature and duration of storage suggest mechanisms which may be significant in natural systems: moist stratification at 5°C caused reduced germination but sustained viability (as assessed by FDA) while dry seed stored at room temperature, showed increased germination with increasing duration of storage. The chilling response may indicate the capacity to initiate secondary dormancy under unfavourable germination conditions.
Morphological Responses of Geraldton Wax to Transient Soil-Water Deficit
Authors: Akilan K , Considine JA , Joyce DC , Marshall JK
Published: December 2005

Changes in leaf angle and flower diameter of Geraldton wax (Chamelaucium uncinatum) in response to declining shoot water potential (ψshoot)) were assessed as indicators of plant water status. Leaves and petals in Geraldton wax moved vertically as ψshoot decreased. In cv. Purple Pride, the leaf angle of recently-matured, fully-expanded leaves and the diameter of fully developed flowers showed strong linear correlations with declining ψshoot (r2 = 0.90 and 0.94 respectively). The relationships were less strong when applied to almost fully expanded leaves (r2 = 0.51) and young flowers (r2 = 0.64). Older leaves showed no consistent correlation between leaf angle and ψshoot (r2 = 0.01). Similar results were observed in cvv. Alba and Lady Stephanie, but the change in orientation for a given change in ψshoot was smaller in cv. Alba than those observed in cvv. Purple Pride and Lady Stephanie. Vertical orientation of leaves and flower petals in droughted plants could be used as indicators of level of water deficit.
Environmental Control of Flowering of Boronia megastigma (Rutaceae) and Hypocalymma angustifolium (Myrtaceae)
Authors: Day JS , Loveys BR , Aspinall D
Published: December 2005

The flowering responses of Boronia megastigma Nees (Rutacae) and Hypocalymma angustifolium Endl. (Myrtaceae) to different photoperiod and temperature regimes were similar despite the fact that these species are from different families. No flowers reached anthesis in a temperature regime of 25°C day/17°C night but flowering of both species occurred in a cool temperatures (17°C day/9°C night). Photoperiod had no effect on flowering at the temperatures tested. Ten weeks of cool temperatures (17°C day/9°C night) were required for a maximum number of flowers to reach anthesis on H. angustifolium plants whereas B. megastigma plants required 15 weeks. Flower development in both species was inhibited by a large difference between day and night temperature (21°C day/5°C night) and promoted if the day/night difference was reversed (9°C day/17°C night). The temperature of the aerial parts of the plant controlled flowering, whereas vegetative growth was controlled by root temperature. Therefore, while a reduction in vegetative growth naturally coincides with the production of flowers, these events are not necessarily linked.
An Embryological Study of Kava, Piper methysticum
Authors: Prakash N , Brown JF , Wang YH
Published: December 2005

An embryological study of Piper methysticum Forster f. (Piperaceae), undertaken to identify the probable cause for the absence of fruits in cultivated varieties, has revealed that the majority of plants in all the cultivars examined bore only male flowers. The anthers are tetrasporangiate and the anther wall comprises a well-developed endothecium with fibrous thickenings, two middle layers and a glandular tapetum. Meiosis is normal and simultaneous cytokinesis leads to tetrahedral microspore tetrads. Pollen degeneration was observed but was of very rare occurrence. The pollen grains are released when they are 2-celled and appear to be healthy and capable of germination. The unilocular ovary contains a single basal ovule which is orthotropous, bitegmic, and crassinucellar. Both integuments contribute to the formation of the micropyle. The development of the female gametophyte conforms to the tetrasporic Fritillaria-type. No abnormalities were noticed either in meiosis of the megaspore mother cell or in subsequent development leading to the formation of the mature embryo sac. Occasional parthenocarpy was observed but without viable seeds being present inside. It is suggested that, although the lack of fruit formation in this species is not because of any deficiencies in its embryological development, it may be due to a simple self-incompatibility mechanism.
Regeneration and Survival of Indigenous Dry Sclerophyll Species in the Brisbane Ranges, Victoria, After a Phytophthora cinnamomi Epidemic
Authors: Weste G , Ashton DH
Published: December 2005

Changes in the distribution of both pathogen and flora provided data on pathogen decline and on survival, colonisation and regeneration of plant species in defined plots in open dry sclerophyll forests of the Brisbane Ranges 23-30 years after invasion by Phytophthora cinnamomi. The density of the stringybark eucalypts (Eucalyptus informal subgenus Monocalyptus) which dominate the overstorey was halved on some plots. The survivors now show vigorous crown growth but few seedlings are present. Regeneration of the understorey occurred in three stages. Firstly, resistant sedges and then seedlings of resistant opportunists rapidly colonised ground left vacant by the destruction of the dominant understorey species, Xanthorrhoea australis. In the second stage, moderately susceptible species such as Banksia marginata and Grevillea steiglitziana resprouted from old stumps and prostrate legumes increased their ground cover. In the third stage some highly susceptible species, such as X. australis, Dillwynia glaberrima, Hibbertia stricta and Monotoca scoparia have regenerated from seed on sites previously badly affected by the pathogen. Some plants of these species have survived for 10 years, despite the continued presence of scattered pockets infected with of P. cinnamomi. However, Isopogon ceratophyllus, frequent in the understorey of the plot prior to disease, has not regenerated.
DNA Markers Reveal Hybrids Between Two Diverse Background Genotypes in Australian Collections of the Bean Rust Fungus Uromyces appendiculatus
Authors: Braithwaite KS , Manners JM , Irwin JAG , Maclean DJ
Published: December 2005

Two classes of molecular markers, RFLPs (restriction fragment length polymorphisms) and RAPDs
(random amplified polymorphic DNA) were used to assess genetic diversity among Australian bean rust
isolates (Uromyces appendiculatus (Pers.) Unger var. appendiculatus) collected from diverse
geographic locations spanning the period 1973-1990. Initially we screened 22 isolates using WLPs
from five DNA probes. This was followed by analysis of a subset of 12 of these isolates using RFLPs
from 10 cDNA probes and RAPDs from 10 arbitrary primers for a comprehensive evaluation of
background genotype. Polymorphic bands revealed the existence of two divergent clusters of isolates,
representing genotypes designated A and B. The RFLP markers showed 30% band dissimilarity
between A and B, and RAPDs 16% dissimilarity. Isolates in a third cluster (genotype AB) exhibited
most of the polymorphic bands present in A and B, but no unique polymorphic bands of their own,
indicating that they had most probably arisen from recent hybridisation between isolates of genotype A
and B. The subset of 12 isolates included 10 race phenotypes, but no clear correlation between
background genotype (as assessed by RFLP and RAPD markers) and race phenotype was evident. We
suggest that Australian races of bean rust have most probably evolved by a combination of mutation to
virulence from common A and B background genotypes, and genetic recombination.
Nitrogen and Phosphorus Availability and the Role of Fire in Heathlands at Wilsons Promontory
Authors: Adams MA , Iser J , Keleher AD , Cheal DC
Published: December 2005

Analyses of carbon, nitrogen and phosphorus in heathland soils at Wilsons Promontory and on Snake Island show that the effects of fire, including repeated fires, are confined to the surface 2 cm. The uppermost soil in long-unburnt heathlands is rich in these elements and usually has a smaller C:N ratio compared with the soil below. Indices of N and P availability (C:N ratios, concentrations of potentially mineralisable N and extractable inorganic P, phosphatase activity) are similar to those in highly productive eucalypt forests-a finding in conflict with past assessments of nutrient availability in heathlands. Phosphatase activity and concentrations of carbon, nitrogen and potentially mineralisable N were less in soils from repeatedly burnt heathlands than in soils from long unburnt heathlands whereas there was a greater concentration of extractable inorganic P in soils from repeatedly burnt heathlands. The balance between nitrogen input and loss is dependent on fire frequency and present-day management of heathland (and other native plant communities with low nutrient capitals) should recognise that over- or under-use of fire will significantly alter soil nutrient pools and availability and that these changes may alter community species composition and productivity.
Patterns of Clonal Variation in Skeleton Weed (Chondrilla juncea), an Apomictic Species
Authors: Chaboudez P
Published: December 2005

Isozymes were used to discriminate clones of the apomictic plant, Chondrilla juncea L. (Asteraceae), a Eurasian species that has become a major weed of cereal cultivations in Australia. The sample that was screened consisted of the progeny of single plants from each of 123 sites in central Turkey. When used in combination, six polymorphic enzyme systems separated 91 distinct clones. Seventy-four percent of samples detected unique clones, none of these being widespread. Chromosome counts established that these clones are triploid. This pattern contrasted with that found in a survey of 23 populations in southeastern Australia. Apart from the narrow-leaf rust susceptible clone, the survey found two additional multilocus genotypes only, both of which are immune to the introduced strain of the rust.
Floristic Change on Heron Island, a Coral Cay in the Capricorn-Bunker Group, Great Barrier Reef
Authors: Rogers RW , Morrison D
Published: December 2005

Floristic change on islands is a matter of considerable theoretical and practical conservation interest. The vascular flora of Heron Island, a small coral cay on the Great Barrier Reef, Australia was, therefore, surveyed at 3 month intervals from September 1990 until December 1993. During this period 57 species were reported for the island, with the number of species present at one time varying from 40 to 53. Six alien species and two native species were reported from the island for the first time. Direct gradient analysis demonstrated a similarity between spring-summer samples and autumn-winter samples, with the pairs of samples being different from each other. Neither the total number of species present at one time nor the proportion of alien species in the flora has increased since 1984, suggesting that the flora has reached equilibrium with the disturbance caused by human activity on the island. A method for estimating the annual rate of species turnover (I1) is outlined, and I1 is calculated for Heron Island and four other islands in the Capricorn-Bunker Group. The low I1 reported for Heron Island is further evidence for floristic equilibrium being approached on this highly disturbed site.
Contrasting Morphology and Ecophysiology of Cooccurring Broad and Terete Leaves in Hakea trifurcata (Proteaceae)
Authors: Groom PK , Lamont BB , Kupsky L
Published: December 2005

We studied the morphology, anatomy, phyllotaxy and daily seasonal ecophysiology of the two leaf types (broad and terete) of Hakea trifurcata (Smith) R.Br., a widespread shrub in south-western Australia. Both leaf types may be present on the same branchlet, with one or two broad leaves forming first during the annual growth period (late winter) followed by many terete leaves in spring. Terete leaves were more xeromorphic than broad leaves, including greater thickness, denser tissues and fewer veins. Broad leaves fixed more carbon and transpired more water per unit mass than terete leaves, in a well ventilated leaf chamber, and had lower (more negative) xylem pressure potentials. Broad leaf temperatures only exceeded those of terete leaves under hot, dry conditions, with no relationship between transpiration rates and leaf temperature. Terete leaves possessed many structural and physiological characteristics commonly associated with drought-tolerant leaves, whereas broad leaves were characteristic of leaves which keep their stomates open during periods of water and heat stress. Both leaf types appear to increase the fitness of this species in a mediterranean climate, with broad leaves having the potential to supply extra photosynthates and nutrients to the new season's growth.
Effects of Safflower Sterility Genes on the Inflorescence and Pollen Grains
Authors: Carapetian J
Published: December 2005

Three interacting, unlinked, nuclear genes are reported to control the inheritance of male-female sterility in safflower (Carthamus tinctorius L.). In a cross between US-10 cultivar (genotype S(1)S(1)s(2)s(2)s(3)s(3)) and a geographically distant Indian line 57-147 (genotype s(1)s(1)S(2)S(2)S(3)S(3)), F-2 plants segregated 57 fertile:7 sterile. Sterile genotypes set no seed under natural conditions. This study reports the effects of sterility genes on the inflorescence and pollen grains. Floret elongation was limited in sterile plants at bloom. Lengths of florets in the sterile individuals showed a 17% and a 40% reduction one day before and on the day of anthesis, respectively. This resulted in a conspicuous pinched appearance of the capitula. Lack of seed development in sterile plants hindered the expansion of capitula and prevented the dried florets from lying against the imbricate bracts as in normal fertile plants. The percentage pollen stainability was 96.1 in US-10, 87.5 in 57-147, 91.3 in the F-1, 90.5 in fertile F-2, and 1.4 in sterile F-2 plants. However, none of the stainable pollen grains of the sterile F-2 plants was viable. The mean pollen diameter was 53.2 in US-10, 56.3 in 57-147, 53.9 in the F-1, 58.1 in fertile F-2, and 35.8 mu m in sterile F-2 plants. Sterile plants exhibited a greater variation in pollen diameter than the fertile plants. Light and scanning electron microscopy observations revealed the absence of normally sculptured and tricolpate pollen from the sterile plants. The results suggest that the sterility genes have their effects primarily on reproductive organs, but do not hinder vegetative development and growth of sterile plants before they bloom.
The Effect of Growth-Regulators, Source of Explants and Irradiance on in vitro Regeneration of Atemoya
Authors: Rasai S , Kantharajah AS , Dodd WA
Published: December 2005

Multiple shoot formation was induced on different media from excised hypocotyl and the nodal cuttings from 5 year old trees of atemoya (Annona cherimola Mill × A. squamosa L.) cv. African Pride. The highest number of shoots were obtained from the distal part (section near the root) of the hypocotyl cultured at a photosynthetic photon flux (PPF) of 36 μmol m-2 s-1 on Murashige and Skoog basal medium (MS) supplemented with 2% sucrose, 2 mg L-1 6-benzylaminopurine (BAP), 0.5 mg L-1 6-furfurylaminopurine (kinetin), 0.1 mg L-1 biotin, 0.1 mg L-1 calcium pantothenate and solidified with 0.8% agar. The number of shoots of mature nodal cuttings cultured on modified MS medium, supplemented with 1 g L-1 ammonium nitrate and the above mentioned growth regulators and addenda, was higher than MS basal or Woody Plant Medium. Increasing the kinetin level increased the number of shoots and fresh weight. Increasing the BAP level above 2 mg L-1 decreased the number of buds, length of shoots and fresh weight. The shoots were incubated in liquid MS medium containing 50 mg L-1 indole-3-butyric acid (IBA) in the dark and after 3 days were transferred to MS basal medium in the light, supplemented with 0.25% activated charcoal and solidified with 0.8% agar. Forty per cent of the shoots rooted. The rooted plantlets were successfully transferred to soil and planted in the glasshouse and 70 per cent of them showed rapid growth. Root induction was improved by pretreatment of shoots in liquid MS containing IBA. The effects of adding cytokinins, biotin and calcium pantothenate to the hypocotyl sections at different PPF and the effect of ammonium nitrate on multiple shoot production by nodal segments of in vivo grown plants are reported.
A Floristic Comparison of Vascular Species in Tasmanian Oldgrowth Mixed Forest With Regeneration Resulting From Logging and Wildfire
Authors: Hickey JE
Published: December 2005

About 20% of Tasmania's wet eucalypt forest is mixed forest, i.e. having a rainforest understorey and a eucalypt overstorey. While one-third of the mixed forest is formally reserved, much of the remainder is subject to logging on an 80-100 year rotation which is insufficient for the redevelopment of mature mixed forest. The routine silvicultural regeneration treatment for wet eucalypt forests is to clearfell, burn and sow with eucalypt seed. A comparison of the Vascular floristics of 20-30-year-old silvicultural and wildfire regeneration with oldgrowth mixed forest showed that most species common in oldgrowth mixed forest were represented in approximately similar frequencies in silvicultural regeneration and wildfire regeneration. The major floristic difference between the two regeneration types was the much lower frequency of oldgrowth epiphytic fern species in silvicultural regeneration and a higher frequency of a sedge species often associated with disturbed areas. However, after a single logging treatment, the vascular plant floristics of silvicultural regeneration were sufficiently similar to wildfire regeneration to assume that, in the absence of further logging or fires, the silvicultural regeneration could become mature mixed forest and eventually rainforest. Further work is required to determine whether regrowth mixed forest can be logged at 80-100 years and still retain sufficient rainforest elements to eventually return to mixed forest within the life span of the dominant eucalypts. The critical factor in the silvicultural perpetuation of mixed forest may be rotation length rather than regeneration treatment.
Culturally Induced Rarity? The Past and Present Distributions of Leucochrysum albicans in Tasmania
Authors: Gilfedder L , Kirkpatrick JB
Published: December 2005

Herbarium records indicate that the endangered straw daisy, Leucochrysum albicans (syn. Helipterum albicans), is less widespread and rarer in Tasmania today than in the past. Currently it has a sparse distribution within a relatively wide ecological range, which spans most of the climatic variation in Tasmania, hut which does not include poorly drained or infertile soils. There is evidence of recent local extinctions and invasions. These and the nature of the local environments in which the species occurs indicate that the species requires freedom from competition for the maintenance of its populations. Cultural activities, such as heavy stock grazing or bulldozing, promote its establishment and survival, whereas the establishment of healthy improved pasture or the exclusion of grazing from native pasture tend to lead to its exclusion or demise. The future of the species may thus largely depend on cultural activities that are usually regarded as antipathetic to nature conservation.
Climate, Grazing and Disturbance, and the Population Dynamics of Leucochrysum albicans at Ross, Tasmania
Authors: Gilfedder L , Kirkpatrick JB
Published: December 2005

A population of an endangered daisy, Leucochrysum albicans (syn. Helipterum albicans), was monitored monthly in grazed and ungrazed plots for several years in a paddock near Ross, Tasmania. The population declined dramatically during the extremely dry summer of 1987, and also experienced high mortality in the dry summer of 1988. Adult plants and germinates were more abundant in grazed than in ungrazed plots for most of the period after this decline. The development of axillary branches on adult plants was much more prominent outside than inside the exclosures. Seedling establishment preferentially occurred on ground dominated by herbs, with establishment being low and extremely brief on grass-covered ground. The frequently disturbed margins of the exclosures were the most favourable sites for establishment of new individuals. The future of this unpalatable rare species seems to be dependent upon management that maintains open and, preferably, disturbed ground.
Genecological Variation in the Germination, Growth and Morphology of Four Populations of a Tasmanian Endangered Perennial Daisy, Leucochrysum albicans
Authors: Gilfedder L , Kirkpatrick JB
Published: December 2005

Seed was obtained from four populations of an endangered perennial daisy, Leucochrysum albicans
(syn. Helipterum albicans), in Tasmania. These populations were from montane basaltic soils, montane
limestone soils, lowland basaltic soils and lowland soils derived from mudstone. All populations had
their highest percentage germination at 20°c, but the montane populations had lower germination rates
than the lowland populations, especially at lower temperatures. The low altitude populations exhibited
more rapid germination than the high altitude populations. In a glasshouse experiment droughting
decreased the growth of the provenances from limestone and mudstone, while having little effect on the
basalt provenances, mulching increased the growth of the lowland provenances relative to the highland
provenances, and the application of fertiliser depressed the growth of the montane basalt provenance.
Variations in leaf characteristics and flowering rates were evident between either provenance or
treatment. The marked geographic variation in germination, morphology and ecological responses
indicates that it is important to maintain the species over its full environmental range.
Amphicarpy in the Cyperaceae, With Novel Variation in the Wetland Sedge Eleocharis caespitosissima Baker
Authors: Bruhl JJ
Published: December 2005

Amphicarpy, the heterocarpic production of serial and basal fruits, occurs in the Cyperaceae in species of the primarily mesophytic genera Bulbostylis and Trianoptiles and in species of the helophytic genera Eleocharis and Schoenoplectus. There is a variety of breeding systems and growth forms across these amphicarpic species. Eleocharis caespitosissima is amphicarpic, with basal fruits buried by positively geotropic culms. The seeds of basal fruits in this species may arise asexually. The selective pressures likely to be important in the development of amphicarpy in the Cyperaceae are discussed.
Post-Zygotic Seed Abortion in Sexual Diploid × Apomictic Tetraploid Intraspecific Paspalum Crosses
Authors: Norrmann GA , Bovo OA , Quarin CL
Published: December 2005

In many species of Paspalum, diploid (2x) cytotypes are usually outbreeders due to a self incompatibility system, while tetraploid (4x) conspecific counterparts are pseudogamous self-fertile apomicts. Intraspecific crossability between 2x female and 4x male cytotypes was investigated using classical methods of crossing in P. almum, P. brunneum, P. rufum, P. intermedium and P. quadrifarium. Expected triploid BII hybrids were obtained in P. intermedium (crossability: 0.004%) and in P. brunneum (crossability: 0.015%). In P. rufum, only tetraploid BIII hybrids were achieved with a crossability of 0.025% Looking for a better performance, in vitro ovary rescue was attempted 5 days after pollination in intraspecific 2x × 4x crosses of P. almum, P. quadrifarium, P. intermedium and P. rufum. The method was useful to recover some triploid BII hybrids in P. almum (success rate: 0.49%) and in P. rufum (0.59%), but failed in P. intermedium and P. quadrifarium. Pollen tube growth was usually inhibited at the stigma or style levels after self-pollination in 2x plants, confirming that diploids are self-incompatible. Pollen of 4x cytotypes germinated and penetrated the pistils of diploid conspecific cytotypes. This indicated that no incompatibility system exists in these species to keep the 2x cytotypes from hybridising with 4x conspecific cytotypes as pollen donors. However, after pollination of 2x cytotypes with pollen of 4x counterparts, most ovules showed embryo and endosperm development, but a few days later, endosperms collapsed and embryos stopped their development. As a result of these processes, sexual self-incompatible 2x cytotypes of Paspalum species produced very few triploid hybrids when pollinated with pollen of their apomictic 4x counterparts. Thus, the low diploid-tetraploid crossability was due to the existence of a post-zygotic abortive system and not caused by pre-fertilisation barriers.
Embryo Rescue Culture Medium for Improved Synthesis of 4x Wheat × Rye Hybrids
Authors: Balatero CH , Darvey NL
Published: December 2005

The cross-incompatibility barrier between 4x wheat and rye has limited the genetic base for triticale breeding. Experiments designed to improve the synthesis of wheat-rye amphihaploids were conducted. The effects of 2,4-D on crossability and 3x hybrid embryo differentiation, and the influence of one-step and two-step media on the culture of immature 3x embryos in vitro, were investigated. Application of 10 mg L-1 2,4-D slightly improved seed set but significantly reduced the frequency of normal embryos. In contrast to the reported favourable effect of 2,4-D on haploid embryo formation in wheat × maize crosses, the application of 2,4-D in the present study offers no real advantage on amphihaploid embryo formation from 4x wheat × rye crosses. For small and immature wheat-rye hybrid (3x) embryos, optimum recovery in vitro was obtained via a two-step procedure consisting of a semi-solid MN medium followed by MS medium supplemented with IAA (1 mg L-1) and BAP (1 mg L-1). For bigger and well-differentiated embryos, the use of a one-step Gamborg's B5 medium was sufficient.
Interaction of Fire, Temperature and Light in the Germination Response of 16 Species From the Eucalyptus marginata Forest of South-Western Australia.
Authors: Bell DT
Published: December 2005

Germination responses to multiple conditions related to fire, temperature and light were examined and
interpreted in relation to the environment of the jarrah (Eucalyptus marginata Donn ex Sm.) forest and
the mediterranean-type climate of south-western Western Australia. Eight of the 16 selected
representatives required a boiling pre-treatment as a simulation of fire before subsequent germination
conditions were imposed. Trial conditions included a range of constant incubation temperatures and
either a constant dark or 12h light:12h dark illumination cycle. Species common to the understorey
tended to have narrow optima to temperature (13-18°C) with the greatest germination being achieved in
temperatures typical of winter. Eucalyptus calophylla, one of the canopy species, germinated over a
wider range of temperatures than the understorey species tested. Several species (e.g. Acacia pulchella
var. glaberrima, Calothamnus rupestris, Eucalyptus marginata, Trymalium ledifolium,
Xanthorrhoea gracilis and X. preissii) were not affected by the different light conditions at lower
incubation temperatures, but more seeds remained dormant under higher temperatures when exposed to
light. Most species, however, germinated best under continuously dark conditions, which related to
being buried under soil. Two species, Banksia grandis and Hakea amplexicaulis, showed much higher
germination under light exposure conditions compared to continuously dark conditions. These two
serotinous species are large seeded and their seed ecology favours large gap and soil surface
establishment. The multiple requirements of particular combinations of fire, temperature and light are
related to the ecology of these native Western Australian species.
Life-History Attributes of Plants in Grazed and Ungrazed Grasslands on the Northern Tablelands of New South Wales
Authors: Tremont RM
Published: December 2005

The composition, diversity and structure of unfertilised temperate grassy communities were compared, after adjacent areas had been grazed or left ungrazed for 16 years. Life-history attributes of species in the two communities were also compared. Most species in both treatments were forbs, but these generally occurred with low frequencies and grasses formed the vegetation matrix. Native and perennial species predominated, reflecting pre-European conditions. Long-term, continuous grazing by sheep had opened the grass and litter canopy, promoted species richness and favoured a suite of morphological plant characteristics. Thus, species with dormant meristematic tissue at or below ground level, forbs of low stature and small tufted grasses were relatively common. The ungrazed treatment was densely vegetated, relatively species-poor and plants tended to have morphological attributes opposite to the above. A later, double-peaked flowering period in the ungrazed community was explained by the greater proportion of native perennials, versus the more common early-flowering exotic annuals in the grazed community. The larger proportion of vegetatively reproducing forbs in the ungrazed treatment reflected the density of the vegetation and the possible absence of appropriate sites for regeneration by seed, or the heterogenous distribution of resources available to interstitial plants.
Factors Limiting the Recruitment of Eucalyptus salmonophloia in Remnant Woodlands .I. Pattern of Flowering, Seed Production and Seed Fall
Authors: Yates CJ , Hobbs RJ , Bell RW
Published: December 2005

Woodlands dominated by Eucalyptus salmonophloia F. Muell. occur throughout the fragmented landscape of the Western Australian wheatbelt. In most of these remnant woodlands, there is no regeneration of E. salmonophloia and this has become a concern for the conservation of biodiversity in the region. This study examined seed production, seed viability and pattern of seed fall in four remnant populations of E. salmonophloia in the central wheatbelt of Western Australia, to determine whether these factors are limiting recruitment. Surveys of flowering, seed production and seed fall were conducted over a two-year-period which included three potential flowering seasons. Individual trees flowered once over this period and the intensity of flowering and the proportion of flowers which set seed varied greatly between remnants. Seed from up to two consecutive flowering seasons was stored in the canopy, thus, E. salmonophloia formed substantial canopy seed stores. Seeds were released from this store throughout the year and seed fall showed only a weak winter decline. The viability of seeds released from the canopy store in each remnant population was high. These results indicate that the availability of viable seed is unlikely to be responsible for the lack of E. salmonophloia recruitment in remnant woodlands.
Early Seedling Growth of Three Species of Danthonia as Affected by Depth of Sowing and Nutrient Supply
Authors: Lodder MS , Groves RH , Muller WJ
Published: December 2005

In an experiment in a controlled environment, seedling emergence of three species of Danthonia
(D. linkii var. fulva, D. tenuior and D. richardsonii) was measured in response to sowing depth.
Seedlings of all three species did not emerge if seeds were buried deeper than 25 mm. At lesser depths,
D. linkii var. fulva showed greatest tolerance to increasing sowing depth, whilst D. tenuior was
intermediate and D. richardsonii was least tolerant of seed burial. In a separate experiment, seedlings
of Danthonia linkii var. fulva and two geographically distinct populations of D. richardsonii emerged
earlier, grew faster and had a higher biomass than those of D. tenuior in response to nutrient supply.
The latter population grew more slowly than the others, but by day 54, the number of emergents of
D. tenuior had equalled those of the other populations. Nutrient addition had little effect on seedling
development, except that by day 54, four times normal nutrient level reduced root growth in all four
populations. No population by nutrient interactions were found for either time to emergence or for
seedling biomass up to 54 days from sowing. Increases in shoot biomass and the reversal of shoot to
root ratios occurred between 41 and 54 days after sowing, by which time seedling establishment of
Danthonia was complete. Some practical recommendations for field sowings are given based on the
results of this and other studies.
Somatic Embryogenesis From Styles of Different Cultivars of Citrus limon (L.) Burm
Authors: Pasquale FD , Carimi F , Crescimanno FG
Published: December 2005

Plants were regenerated from styles of three cultivars of lemon (Citrus limon (L.) Burm.),
'Monachello', 'Lunario' and 'Femminello Santa Teresa'. Styles and stigmas were excised from flowers,
and cultured on Murashige and Skoog (MS) basal medium. Callus formation occurred from the style
base 2 weeks after culture initiation and was significantly (P < 0.01) greater in immature flowers
growing on BAP supplemented medium. Somatic embryos appeared 8 weeks later. The addition of
BAP in the culture medium increased significantly (P < 0.01) the embryogenic response of the style,
and the best regeneration occurred on MS basal medium supplemented with 13.3 μM
6-benzylaminopurine (BAP) and 146 mM sucrose. Once embryos were transferred to MS medium
supplemented with 500 mg L-1 malt extract and 0.27 μM α-naphthaleneacetic acid (NAA), they
developed into plantlets. After 5 or 6 months of continuous subculturing, the embryogenic callus
became habituated and new embryos were still arising.