bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of dietary protein source and protected methionine (Lactet) on wool growth and microbial protein synthesis in Merino wethers
Authors: White C. L. , Young P. , Phillips N. , Rodehutscord M.
Published: September 2002

With increasing awareness of the importance of controlling tender wool, there
is a need to describe supplementary feeds in terms of their effects on wool
growth. Since wool growth is largely a function of the quantity and quality of
absorbed protein, the aim of this experiment was to compare the protein
quality of different diets in relation to their ability to promote wool
growth. An additional aim was to compare observed responses with those
predicted using feeding models based on metabolisable protein. Sixty-four
Merino weaner wethers were allocated to 8 treatment groups in a factorial
design consisting of 4 diets each at 2 levels of protected methionine. The 4
roughage-based diets consisted of different protein sources:
Rumentek®-protected canola meal (at 33% of
the diet), oats plus urea (oats at 46% and urea at 2.6%),
Lupinus angustifolius (at 36%), and
L. albus (at 36%). The 2 levels of protected
methionine were 0 or 3 g/day as Lactet. The diets were formulated to be
isonitrogenous and isoenergetic and were fed at 1.5 × maintenance
metabolisable energy. The experiment lasted 13 weeks, which included a 3-week
balance collection period in which faeces and urine were collected. Wool
growth in sheep fed the protected canola meal diet was 37% greater than
in sheep fed oats (1.37 v. 1.0
mg/cm2 per day), and 73% greater than in
sheep fed L. angustifolius (P <
0.001). Wool growth from the oat diet was 26% greater than from the
L. angustifolius diet (P <
0.05). There was no effect of diet on rumen volatile fatty acid
concentrations. Lactet increased wool growth by 18% across all diets
(P < 0.001), representing an additional 0.17
mg/cm2 per day or 1.7 g/head per day. There were
no significant differences in liveweight gain between the diets unless Lactet
was added. When Lactet was added, lupins produced a significantly higher
liveweight gain than oats or protected canola meal. Lactet increased mean
liveweight gain by 22% across all diets (P <
0.05). Lactet also increased the concentration of plasma albumin, decreased
plasma α-amino nitrogen, and increased urinary excretion of creatinine
and purine derivatives (P < 0.05). The findings
highlight the need to evaluate feed sources in terms of protein degradability
and sulfur amino acid composition, particularly when assessing effects on wool
growth. The inability of current feeding models to incorporate differences in
amino acid flows, particularly sulfur amino acids, is an impediment to
evaluating supplement quality in terms of wool growth.
Regrowth of prairie grass (Bromus willdenowii Kunth) and perennial ryegrass (Lolium perenne L.) in response to temperature and defoliation
Authors: Slack K. , Fulkerson W. J. , Scott J. M.
Published: September 2002

This glasshouse study was undertaken to determine the effect of temperature
and defoliation on the regrowth of prairie grass
(Bromus willdenowii Kunth cv. Matua) in comparison with
perennial ryegrass (Lolium perenne L. cv. Dobson).
Individual plants of prairie grass and perennial ryegrass were grown in 2
mini-swards with one half as prairie grass and the other as ryegrass. From
H0 (13 weeks after sowing) to the completion of the
experiment at H3, one sward was maintained at a
day/night temperature of 18/10˚C and the other at
25/15˚C. From H0 to H1,
prairie grass was defoliated 4 times at the time taken to regrow 1 new leaf
per tiller (1-leaf stage), 2 times at the 2-leaf stage, or once at the 4-leaf
stage to 60, 90, or 120 mm stubble height. Similarly, ryegrass was defoliated
3 times at the 1- leaf stage, once at the 1-leaf stage then once at the 2-leaf
stage, or once at the 3-leaf stage to 30, 60, or 90 mm stubble height. Plants
were subsequently harvested at H1,
H2, and H3, being the
commencement, mid-point, and completion of the full regrowth cycle (4- and
3-leaf stage for prairie grass and ryegrass, respectively).
Prairie grass was more adversely affected by frequent defoliation than
ryegrass. The combination of high temperature and frequent defoliation reduced
growth rates by 66 v. 54%, stubble dry matter
(DM) by 50 v. 11%, root DM by 62
v. 45%, and stubble water-soluble carbohydrate
(WSC) by 52 v. 21% for prairie grass and
ryegrass, respectively.
In contrast, ryegrass was more affected by defoliation height than prairie
grass, particularly at the higher temperature. Close defoliation and high
temperature reduced growth rate by 35 v. 25%,
root DM by 18 v. 0%, and stubble WSC by
84% v. 36% for ryegrass and prairie grass,
respectively. The number of tillers per plant was reduced by close
defoliation, more so at the high temperature in ryegrass but not in prairie
grass.
Defoliating prairie grass to 90 mm stubble height at the 4-leaf per tiller
stage compared with the 1-leaf per tiller led to maximum restoration of
stubble WSC reserves as well as maximising leaf and root growth. The higher
stubble WSC and greater root DM of prairie grass, together with its ability to
maintain growth rates and tillering under high temperature, are attributes
which explain why prairie grass appears to be more productive and persistent
than ryegrass in a subtropical environment.
Effect of liveweight and pasture height on cattle bite dimensions during progressive defoliation
Authors: Cangiano C. A. , Galli J. R. , Pece M. A. , Dichio L. , Rozsypalek S. H.
Published: September 2002

Five experiments each with a different forage species (wheat, oats, forage
sorghum, millet, and lucerne) were performed to determine the effects of
cattle liveweight and pasture height, created by progressive defoliation, on
bite dimensions and bite weight. In each experiment, 3 levels of liveweight
and 3 levels of initial sward heights were used. Sward height had a positive
effect on bite depth and bite area, although the effect on bite weight
differed among forage species. In general, the effect of liveweight on bite
dimensions was not significant. It is concluded that bite area and bite weight
are determined principally by pasture structure (e.g. height and bulk density)
rather than by mouth dimensions. According to our results, when forage intake
or ingestive behaviour are to be explained, pasture measurements should
describe successive horizons equal to 50% of pasture height to reflect
the bite depth measured in cattle. Also, the results indicate that lighter
animals could get a nutritional advantage since they may achieve a relative
high bite weight per kg liveweight.
Bean yellow mosaic potyvirus infection of alternative annual pasture, forage, and cool season crop legumes: susceptibility, sensitivity, and seed transmission
Authors: McKirdy S. J. , Jones R. A. C. , Latham L. J. , Coutts B. A.
Published: September 2002

Seven field and 5 glasshouse experiments were done during 1994–98 to
determine the relative susceptibilities and sensitivities of a wide range of
alternative annual pasture, forage, and crop legumes to infection with isolate
MI of bean yellow mosaic virus (BYMV). Seed harvested from some species was
also tested for seed transmission of the virus. Seven of 18 genotypes
belonging to 17 species of annual pasture and forage legumes evaluated in 2
replicated field experiments were ranked as highly susceptible to BYMV, 7 as
susceptible, 2 as moderately resistant, 1 as resistant, and 1 as highly
resistant. The most susceptible and sensitive were
Biserrula pelecinus,
Trifolium cherleri, T. incarnatum,
and T. spumosum.
Ornithopus sativus was resistant but sensitive, whereas
Hedysarum coronarium was highly resistant.
H. coronarium was not infected when manually inoculated
repeatedly with 3 different BYMV isolates. Seventy-three of the 94 genotypes
of 7 crop legume species tested in the same replicated field experiments were
ranked as highly susceptible, including 58/68 of
Lens culinaris. Of the remaining genotypes, 6 were
susceptible, 5 moderately resistant, 9 resistant, and 1 highly resistant. Five
other crop legumes were included in other field experiments in which these
species were ranked as highly susceptible (1) or resistant (4). Overall, the
most susceptible and sensitive crop legume species were
Lens culinaris (most genotypes),
Lathyrus cicera, L. ochrus, and
Vicia narbonensis.
Lathyrus sativus (3 genotypes only),
V. sativa (4 genotypes),
Cicer arietinum, Pisum sativum,
and V. faba were resistant to isolate MI, and
Lens culinaris ILL7163 was highly resistant. When
infected, C. arietinum was ranked as highly sensitive
but symptoms within the other resistant crop species varied in sensitivity
between genotypes. Extreme resistance was confirmed in
Lens culinaris ILL7163 when it was manually and
aphid-inoculated repeatedly with 3 different BYMV isolates.
When testing seedlings for seed transmission of BYMV, germination on moist
paper towels before testing usually proved more effective than growing in soil
in the glasshouse. Low rates of seed transmission of BYMV
(0.03–1%) were detected in 9 alternative pasture or forage and 3
alternative crop legume species. This is the first report of seed transmission
of BYMV in these species. The pasture or forage species with the highest seed
transmission rates were T. clypeatum and
T. spumosum (both 1%). The crop legume species in
which seed transmission was found were L. cicera
(0.1%), L. sativus (0.2%), and
V. sativa (0.5%).
The high susceptibility and sensitivity to BYMV in some alternative annual
pasture, forage, and crop legumes is a cause for concern, especially when they
are intended for sowing in BYMV-prone high rainfall zones. Seed transmission
of BYMV also leads to inadvertent introduction of the virus to new sites.
Measurement of decomposition and associated nutrient release from barrel medic (Medicago truncatula) hay and chickpea (Cicer arietinum) straw using an in vitro perfusion system
Authors: Villegas-Pangga Gina , Blair G. J. , Lefroy R. D. B.
Published: September 2002

Two in vitro laboratory experiments were conducted to
evaluate the effects of nutrient additions, soil inoculation, and sampling
times on the decomposition rates and nutrient release patterns of leguminous
crop residues. Cumulative CO2 evolution and the percentage nutrient release
from barrel medic hay (Medicago truncatula) and chickpea
straw (Cicer arietinum) were determined over a 6-week
period using a 0.005 M CaCl2 recycling system (UNE
in vitro perfusion apparatus). The decomposition study
was carried out at 25˚C in a controlled temperature laboratory. There
were no significant differences between the decomposition rates of the 2
residues. The percentage C release was not significantly affected by nutrient
addition or by soil inoculation. More than 50% of the total C that was
released from the residues occurred in the first 7 days with peak release at
3–4 days. Because of an accumulation of nutrients in a muscilaginous
substance in the apparatus, and adsorption of P to the plastic, it was not
possible to measure the release of nutrients from the residues by sampling the
perfusion solution. This had to be achieved by direct measurement of loss of
nutrients from the residues. Except for K, the nutrient released from residues
was not affected by residue or sampling time.
Germination response and viability of Orobanche crenata Forsk. seeds subjected to temperature treatment
Authors: Mauromicale G. , Restuccia G. , Marchese M.
Published: September 2002

Orobanche crenata is a chlorophyll-lacking holoparasite
that subsists on the roots of plants, inflicting severe damage to legume crops
(broad bean, pea, lentil, vetch, grass pea, chickpea) in the Mediterranean and
Middle East regions. Laboratory studies were conducted to determine the
effects of high temperatures [20˚C (control), 38˚C, 40˚C,
42˚C, or 44 0.5˚C] on seed germination of
O. crenata in relation to different duration of
temperature treatments (12 or 24 h), seed age (57 or 94 months), and root
extracts (Vicia faba major cv. 45 NS and
V. faba minor cv. Sikelia). The seed viability response
to temperature (20–100˚C) in relation to 2 seed ages (57 or 93
months) was also investigated. The increase in temperature exposure of seed
from 20˚C to 30˚C, 40˚C, 42˚C, and 44˚C determined a
significantly progressive reduction in the germination percentage, which was
21, 13, 6, 0, and 0%, respectively. This reduction in germination was
due mainly to an increase in the secondary dormancy, since viability of the
same seed, checked by tetrazolium test, ranged between 60% and
99%. Seed viability linearly decreased with increasing seed exposure
temperature until reaching zero at 80˚C.
Quantifying the growth and development of commercial barley cultivars over two contrasting growing seasons in Western Australia
Authors: Kamali M. R. Jalal , Boyd W. J. R.
Published: September 2002

The relationships between growth, development, and grain yield were examined
in 3 phenologically different and commercially available barley cultivars over
2 growing seasons with very different weather patterns. Favourable conditions
for crop growth in 1994 were followed by intensifying soil moisture stress
over the second half of the season. In 1995, unfavourable conditions for crop
growth due to saturated soils over the first half of the season were followed
by favourable conditions and the growing season was extended by 1 month.
Floral initiation was delayed, and the duration of the vegetative phase
extended, when conditions were favourable for initial crop growth, but
durations from sowing to anthesis and maturity were advanced when conditions
for favourable crop growth were reversed. Differences in seasonal conditions
over different portions of the growing seasons were reflected in corresponding
differences in growth occurring over those periods. Favourable conditions up
to the time of awn appearance in 1994 resulted in higher maximum leaf area
indices than in 1995 (5.36 v. 2.59), higher shoot
numbers per plant (10.2 v. 5.7), and higher dry mass per
m2 (710 v. 462
g/m2). Favourable conditions after awn appearance in
1995 resulted in a higher proportional increase in dry mass over the grain
development phase than in the previous year (57%
v. 42%), higher grain numbers per spike (25
v. 23), greater grain size (41 v.
35 mg), and higher harvest indices (41% v.
38%). Final dry masses and grain yields, averaged over cultivars, did
not differ significantly with season.
Cultivars followed the same generalised patterns of growth and development,
with opportunistic interactions between differences in the timing of
developmental events and transient weather conditions determining the
amountof, and rate with which, dry matter accumulated and the manner in which
it was partitioned. Of the developmental differences recorded only one, the
timing of awn appearance (= heading), was considered a useful selection
criterion. The impact of transient and unpredictable variation in seasonal
weather has major implications for the interpretation of studies not
replicated over seasons and for early generation selection in barley breeding
programs. A methodology for minimising the confounding influences involved is
proposed.
LIGULE: An evaluation of indigenous perennial grasses for dryland salinity management in south-eastern Australia. 2. Field performance and the selection of promising ecotypes
Authors: Mitchell Meredith L. , Koen T. B. , Johnston W. H. , Waterhouse D. B.
Published: September 2002

This paper reports the results of an initial evaluation of a large collection
of Australian perennial native grasses. The overall aim of the research was to
identify accessions that may be useful for pastoral purposes and for
controlling land degradation on hill-lands in the high (>500 mm) rainfall
zone of south-eastern Australia. Accessions (807) representing 37 target
species were established in spaced plant nurseries at Rutherglen and Wagga
Wagga. Dactylis glomerata L. cv. Porto and
Eragrostis curvula (Schrad) Nees. Complex cv. Consol
were established as comparator (control) species.
A range of attributes was observed over a 2-year period (19900—1992),
including persistence, vigour, productivity, palatability, morphology, and
characteristics related to seed production. Accessions were initially culled
on the basis of their persistence. Data for a range of attributes were
separately analysed using pattern analysis to provide a broad overview of the
performance and characteristics of the remaining accessions. A number of
selection criteria were applied which resulted in selection of a promising
group of 20 accessions (12 species from 8 genera). The promising group of
accessions will be evaluated further at field sites typical of hilly
landscapes in the 500mp;mdash;600 mm rainfall zone of south-eastern
Australia.
Summer-autumn rainfall effects on wool staple strength and position of break. II. Rainfall simulations, with or without wind, on sheep on days of different ambient temperatures
Authors: Woodgate R. G. , Chapman H. M. , Robertson I. D. , Bell K. J.
Published: September 2002

Previous small-scale field work failed to show any influence on staple
strength from various different rainfall simulations, other than those where
sheep grazed germinating green pasture following rainfall. The present study
was designed to incorporate variables such as ambient temperature and the
influence of wind into rainfall simulations onto Merino sheep.
Different treatments did not show any effect on staple strength despite sheep
being subjected to simulated rainfall events on warm and cool days, with or
without additional wind. This lack of effect on wool quality was despite
significant treatment effects on sheep rectal and skin temperatures.
Water content of a red-brown earth subjected to a range of agronomic vegetation options in south-eastern Australia
Authors: Whitfield D. M.
Published: September 2002

The management of ground water recharge in south-eastern Australia relies on
the formulation of agricultural practices that utilise rainfall before it
moves below the root-zone. Annual cycles of soil water content were therefore
measured in a red-brown earth subjected to 5 fallow-free crop sequences, to 2
crop sequences that included fallow, and to 3 pastures. Changes in soil water
content induced by wheat, barley, lupin, pea, safflower, canola, and fallow
were compared with those of annual pasture and 2 monocultures of the
deep-rooted perennials phalaris and lucerne in 3 years of study.
Mean minimum soil water content (0–1.6 m) seen in December and May was
approximately 355 mm in lucerne and phalaris, 410 mm in annuals (crops and
pasture), and 475 mm in fallow. Corresponding soil water deficits appropriate
to lucerne, annuals, and fallow were 185, 135, and 65 mm, respectively.
Lucerne and annuals both removed approximately 85 mm water from the upper 0.6
m of the soil profile. Differences arose in the subsoil below 0.6 m, where
lucerne, annuals, and fallow produced soil water deficits of approximately
100, 50, and 25 mm, respectively. The difference in soil water deficit of
deep-rooted perennials and annuals was therefore caused by the extra 50 mm of
water extracted by lucerne and phalaris below 0.6 m in the period
September–December. The dry subsoil endured through summer to promote
the storage, by soil, of rainfall in winter.
The data suggest that the spatial utility of an agronomic recharge control
option in south-eastern Australia depends on the magnitude of the soil water
deficit associated with the vegetation. The soil water deficit, relative to
winter (May–August) rainfall, discriminates between areas where annuals
suffice for recharge control, where lucerne and phalaris are required for
recharge control, and where agronomic annuals and perennials are both
conducive to high rates of drainage.
Do Angular Momentum Induced Ellipticity Correlations Contaminate Weak Lensing Measurements?
Authors: Natarajan Priyamvada , Crittenden Robert G. , Pen Ue-Li , Theuns Tom
Published: September 2002

Alignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear field. Weak gravitational lensing can also induce ellipticity correlations since the images of neighboring galaxies will be distorted coherently by the intervening mass distribution. Comparing these two sources of shape correlations, it is found that for current weak lensing surveys with a median redshift of zm = 1, the intrinsic signal is a contaminant on the order of 1–10% of the measured signal. However, for shallower surveys with zm ≤ 0.3, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors.
Could We Detect O2 in the Atmosphere of a Transiting Extra-solar Earth-like Planet?
Authors: Webb John K. , Wormleaton Imma
Published: September 2002

Although the extra-solar planets discovered so far are of the giant, gaseous type, the increased sensitivity of future surveys will result in the discovery of lower mass planets. The detection of O2 in the atmosphere of a rocky extra-solar planet would be a potential indicator of life. In this paper we address the specific issue of whether we would be able to detect the O2 A-band absorption feature in the atmosphere of a planet similar to the Earth, if it were in orbit around a nearby star. Our method is empirical, in that we use observations of the Earth's O2 A-band, with a simple geometric modification for a transiting extra-solar planet, allowing for limb-darkening of the host star. We simulate the spectrum of the host star with the superposed O2 A-band absorption of the transiting planet, assuming a spectral resolution of ~8 kms−1(typical of current echelle spectrographs), for a range of spectral signal-to-noise ratios. The main result is that in principle we may be able to detect the O2 A-band of the transiting planet for host stars with radii R≤ 0.3Rʘ. However, using existing instrumentation and 8m telescopes, this requires target M-stars with m(V) ≈ 10 or brighter for integration times of ~10 hours or less. The number of such stars over the sky is small. Larger aperture telescopes and/or improved instrumentation efficiency would enable surveys of M-stars down to m(V) ≈ 13 and greatly improve the chances of discovering life elsewhere.
Reconnection in Pulsar Winds
Authors: Kirk J. G. , Lyubarsky Y.
Published: September 2002

The spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the ‘termination shock’ itself must be responsible for dissipating the wave.

This paper is dedicated to Don Melrose on his 60th birthday.
Single Dish Polarisation Calibration
Authors: Johnston Simon
Published: September 2002

Using the formalism of Hamaker, Bregman & Sault (1996), I derive a method for the polarisation calibration of observations made with a single radio telescope. This method is particularly appropriate for observations of pulsars, where the sign and magnitude of the circular polarisation are useful for understanding the emission processes at work. I apply the method to observations of PSR J1359–6038 made using the multibeam receiver on the Parkes radio telescope.
Annual Modulation in the Variability Properties of the IDV Source 0917+624?
Authors: Fuhrmann L. , Krichbaum T. P. , Cimò G. , Beckert T. , Kraus A. , Witzel A. , Zensus J. A. , Qian S. J. , Rickett B. J.
Published: September 2002

There is new evidence which identifies seasonal changes of the variability time scale in intraday variable (IDV) sources with refractive interstellar scintillation effects. Such a RISS model takes the annual change of the Earth's velocity relative to the scattering medium into account. In September 1998 we found a remarkable prolongation of the variability time scale in the IDV source 0917+624 with only small variations in flux density during a period of 5 days. This was explained as a seasonal effect, in which the velocity vector of the Earth and the interstellar medium nearly cancelled. In order to further investigate the applicability of the model for 0917+624, we performed an Effelsberg 6 cm-flux monitoring program over the course of one year. Since September 2000, the source appears to be remarkably inactive and yet (May 2001) no return to its normal, faster and stronger variability pattern is observed. Here, our observational results and a possible explanation for the current quiescence are presented.
The Size of IDV Jet Cores
Authors: Beckert T. , Krichbaum T. P. , Cimò G. , Fuhrmann L. , Kraus A. , Witzel A. , Zensus J. A.
Published: September 2002

Radio variability on timescales from a few hours to several days in extragalactic flat spectrum radio sources is generally classified as intraday variability (IDV). The origin of this short term variability is still controversial and both extrinsic and intrinsic mechanisms must be considered and may both contribute to the observed variations. The measured linear and circular polarisation of IDV sources constrains the low energy end of the electron population. Any population of cold electrons within sources at or above the equipartition temperature of 1011 K depolarises the emission and can be ruled out. Intrinsic shock models are shown to either violate the large fraction of sources displaying IDV or they do not relax the light travel time argument for intrinsic variations. From structure function analysis, we further conclude that interstellar scintillation also leads to tight size estimates unless a very local cloud in the ISM is responsible for IDV.
A Very Rapid Extreme Scattering Event in the IDV Source 0954+658
Authors: Cimò Giuseppe , Beckert T. , Krichbaum T. P. , Fuhrmann L. , Kraus A. , Witzel A. , Zensus J. A.
Published: September 2002

Extreme scattering events (ESEs) are dramatic variations of the flux density at gigahertz frequencies caused by ray path distortions within an isolated inhomogeneity (‘plasma lens’) in the interstellar medium. These events are characterised by a deep flux density minimum in the light curve with, in some cases, surrounding maxima. The variability time scales range from weeks to months. These phenomena show a strong frequency dependence, in which the variability amplitudes increase with wavelength. During an intraday variability (IDV) monitoring project (March 2000), a feature resembling an ESE-like event appeared in the variable light curve of 0954+658, however with a time scale of less than two days. We will discuss this effect and its implications for a better description of the interstellar medium.
New Results from an ATCA Study of Intraday Variable Radio Sources
Authors: Bignall H. E. , Jauncey D. L. , Kedziora-Chudczer L. L. , Lovell J. E. J. , Macquart J.-P. , Rayner D. P. , Tingay S. J. , Tzioumis A. K. , Clay R. W. , Dodson R. G. , McCulloch P. M. , Nicolson G. D.
Published: September 2002

We are undertaking an observational program using the ATCA to monitor the intraday variability (IDV) of a sample of sources at 4.8 and 8.6 GHz. The sources were selected to include the known strong southern IDV sources plus a number of sources whose IDV was recently discovered. The present monitoring program will extend over a full year in order to search for any annual cycle that may be present in the long-term IDV characteristics of these sources. In this paper we discuss the observing strategy and data analysis, and present the first results from our observations.
Brightness Temperature Constraints to Compact Synchrotron Source Radiation Obtained from IDV and VLBI Observations
Authors: Kellermann K. I.
Published: September 2002

We discuss the observational and theoretical constraints on the brightness temperature of compact opaque synchrotron sources. We consider the implication of observed apparent velocities on the amount of Doppler boosting and compare this with values deduced from directly measured brightness temperatures from ground and space based VLBI observations, as well as the implications of intraday variability. We also discuss the maximum rest frame brightness temperature expected under conditions of both inverse Compton cooling and equipartition conditions.
Broad-band Radio Spectra Variability of 550 AGN in 1997-2001
Authors: Kovalev Y. Y. , Kovalev Yu A. , Nizhelsky N. A. , Bogdantsov A. B.
Published: September 2002

Results are presented of long-term monitoring at the radio telescope RATAN–600 and a model interpretation of instantaneous 1–22 GHz spectra at six frequencies for a sample of 550 compact extragalactic radio sources. The sources are selected from the Preston et al. (1985) VLBI survey and are located in the declination range from −30° to +43°. Dependence of the index of variability on frequency is analysed for different subsamples. Factors of flux density variations range from 1 to 15. A typical behaviour of spectra evolution during strong radio outbursts in various objects is recognised suggesting a common physical nature of the variability. Invoking VLBI observations in spectra–structure analysis, we find that usually more than 70% of the total emission is coming from the mas scale at frequencies higher than 5 GHz. The observed variability can be explained in the model with a relativistic jet of parsec scale in the longitudinal magnetic field or in the shock-in-jet model.
The Effect of Radiation Drag on Relativistic Bulk Flows in Active Galactic Nuclei
Authors: Luo Qinghuan
Published: September 2002

The effect of radiation drag on relativistic bulk flows is re-examined. Highly relativistic bulk flows in the nuclear region are subject to Compton drag, i.e. radiation deceleration as a result of inverse Compton scattering of ambient soft photon fields from emission from the accretion disk, broad line region, or dusty torus. Possible observational consequences of X-/γ-ray emission produced from Compton drag are specifically discussed.
Helium-star Mass Loss and Its Implications for Black Hole Formation and Supernova Progenitors
Authors: Pols Onno R. , Dewi Jasinta D. M.
Published: September 2002

Recently the observationally derived stellar-wind mass-loss rates for Wolf-Rayet stars, or massive naked helium stars, have been revised downwards by a substantial amount. We present evolutionary calculations of helium stars incorporating such revised mass-loss rates, as well as mass transfer to a close compact binary companion. Our models reach final masses well in excess of 10 M⊙, consistent with the observed masses of black holes in X-ray binaries. This resolves the discrepancy found with previously assumed high mass-loss rates between the final masses of stars which spend most of their helium-burning lifetime as Wolf-Rayet stars (˜3 M⊙) and the minimum observed black hole masses (6 M⊙). Our calculations also suggest that there are two distinct classes of progenitors for Type Ic supernovae: one with very large initial masses (35 M⊙), which are still massive when they explode and leave black hole remnants, and one with moderate initial masses (˜12–20 M⊙) undergoing binary interaction, which end up with small pre-explosion masses and leave neutron star remnants.
Morphological, evolutionary and taxonomic aspects of Australian and New Zealand Microseris (Asteraceae)
Authors: Vijverberg Kitty , Lie Louis , Bachmann Konrad
Published: September 2002

The Australian and New Zealand Microseris is supposed to
have evolved from one or a few diaspores after a unique event of long-distance
dispersal from western North America. At present, the plant group includes two
species, M. lanceolata (Walp.) Sch.-Bip. and
M. scapigera (Forst.) Sch.-Bip., each with two
morphologically and ecologically divergent ecotypes. In spite of this
classification, the morphological variation within and among ecotypes is not
entirely consistent, and molecular investigations show evidence for the,
possibly recent, occurrence of hybridisations between plants of different
ecotypes. The present study investigates the overall morphological
similarities among 1–4 plants of each of 54 Australian and New Zealand
Microseris populations. The aim of the study was to gain
further insights into the delimitation of species and ecotypes, the placement
of populations that could thus far not be assigned to an ecotype and the
adaptive radiation of the plant group. The results confirm the previously
defined ecotypes and assign all but two of the questionable populations to
ecotypes. They show that a broad range of character states rather than a few
'diagnostic' ones are specific for the ecotypes. The data confirm
our earlier conclusion from molecular results, indicating that ecotype
characteristics are maintained or reestablished by selection or adaptation,
after dispersal or hybridisation between ecotypes. Despite (incidental)
genetic exchange among populations of different ecotypes, the process of
adaptive radiation is progressing. The combined morphological and molecular
results are not incongruent with the present species delimitation. However,
they also may support the split up of M. scapigera into
two species and other phylogenetic solutions.
Habitat preference and reproductive traits of a major Australian riparian tree species (Casuarina cunninghamiana)
Authors: Woolfrey A. R. , Ladd P. G.
Published: September 2002

The population structure and reproductive biology of the river oak
(Casuarina cunninghamiana) were studied along the
Murrumbidgee River on the Southern Tablelands of eastern Australia. The
species has cone-like infructescences but is not serotinous, with samaras
released when they are mature. Samaras were mostly distributed by wind close
to female trees but were also carried by water. The first year of study (1985)
appeared to be a mast year for seed production with much lower seed fall in
the following year. Seedling establishment was spatially very variable, mostly
under female canopies and appeared earlier on soil within the river channel
than on the bank. Turnover was high and seedlings in the river channel
generally died after being inundated. Most trees were within 3 m of the mean
river level. However, the total distribution of adults was within the envelope
of maximum floods in the area but establishment was not dependent on floods.
The population structure was the result of yearly recruitment, although
episodic events (floods, drought) may enhance or decrease establishment.
Pot-trial results paralleled the field situation with substrate and
water-table level not affecting germination of seed but strongly influencing
seedling growth. Plants grew best on cobble substrates under a low water-table
regime and poorly on cobbles with high water and sandy substrate under all
water-table levels. Cobble banks seemed the best substrate for growth within
the river channel and establishment may be prolific. Less-abundant seedling
establishment occurred upslope but controls over this were not investigated.
CO2 and land-use effects on Australian vegetation over the last two centuries
Authors: Berry Sandra L. , Roderick Michael L.
Published: September 2002

Coincident with major changes in land use and management in Australia over the past 200 years, there has been a 20% increase in the concentration of carbon dioxide ([CO2]) in the atmosphere. We investigate the way in which these two factors have modified the natural vegetation at the continental scale. We describe landscapes in terms of the abundance of three leaf functional types, 'turgor' (T), 'mesic' (M) and 'sclerophyll' (S). We have previously shown that continental-scale estimates of the TMS composition can be made from climatic and satellite data. In this study, we extend those results by estimating the TMS composition for the 'natural' vegetation (i.e. the present vegetation if there had been no change in land use and management). By comparing those estimates with the existing vegetation, we show that changes in land use have resulted in a large increase in the abundance of T leaves (seasonally green leaves of annual and ephemeral herbaceous plants) and there is a corresponding decline in plants with M and S leaves (evergreen trees, shrubs and perennial grasses). We then use a water use efficiency model to estimate the natural vegetation cover 200 years ago when the [CO2] was about 280 μmol mol–1. According to the model, 200 years ago the seasonally green (T) vegetation cover was similar to that at the present (excluding cultural vegetation cover), but there was lower evergreen cover. The increase in evergreen cover with increasing [CO2] could have been expressed as an increase in trees, shrubs or grasses having M and S leaf forms, depending on soil moisture and nutrient availability. According to our model, while 'woody vegetation thickening' may have been exacerbated by the increase in [CO2], other changes associated with European settlement are also important.
Distribution of Phytophthora cinnamomi in the northern jarrah (Eucalyptus marginata) forest of Western Australia in relation to dieback age and topography
Authors: McDougall K. L. , Hardy G. E. St J. , Hobbs R. J.
Published: September 2002

The spatial distribution of Phytophthora cinnamomi Rands
at seven dieback sites in the jarrah
(Eucalyptus marginata Donn. ex Smith) forest of Western
Australia was determined by the following two baiting techniques: in situ
baiting with live Banksia grandis Willd. seedlings and
ex situ baiting of sampled soil and root material. Four areas within each site
were sampled, reflecting dieback age and position in the landscape.
Approximate dieback ages of 50, 20 and 5 years were determined by aerial
photography. The 50-year-old age class was divided into wet valley floor and
dry gravelly slope. Phytophthora cinnamomi was recovered
most frequently from the 5-year-old (dieback fronts) and wet 50-year-old areas
by both baiting techniques. It was recovered from more than twice as many
areas and about five times as many samples when in situ
B. grandis baits were used compared with ex situ soil
and root baiting. Almost all recoveries from in situ baits were made between
October and December. From both methods, it appears that
P. cinnamomi has a patchy distribution within dieback
sites in the northern jarrah forest. It is easily detected only on dieback
fronts and wet valley floors. On dry gravelly sites affected 20 years or more
ago, P. cinnamomi is rare and may even be absent at some
sites. This makes confident detection of the pathogen difficult. In situ
baiting at least allows a temporal component to the sampling and will be a
useful method of detection in areas where P. cinnamomi
is rare or transient.
Morphometric, genetic and ecological studies clarify the conservation status of a rare Acacia in Western Australia
Authors: Elliott Carole P. , Yates Colin J. , Ladd Phillip G. , Coates David J.
Published: September 2002

Acacia species 'Dandaragan' is known from
one population confined to the Dandaragan–Badgingarra area in
south-western Western Australia and is classified as critically endangered.
Morphological and allozyme studies show that A. sp.
'Dandaragan' has close affinities with
Acacia microbotrya Benth.
sens. lat. and warrants taxonomic recognition at
subspecies rank. A combination of floral and phyllode characters clearly
separated A. sp. 'Dandaragan' and
A. microbotrya s. l. by the presence of a discrete
morphological boundary in the canonical variates plot and the high percentage
of correct re-substitution classifications of individuals into pre-defined
taxa. UPGMA and maximum likelihood analyses of allozyme data distinguished
A. sp. 'Dandaragan' and
A. microbotrya s. l. Levels of genetic diversity were
lower in A. sp. 'Dandaragan' than in
A. microbotrya s. l. The size-class and lifestage
structure of the A. sp. 'Dandaragan'
suggests that the population is stable and possibly increasing in size
predominantly by vegetative spread. The presence of a soil seed reserve and
the ability to reproduce from root suckers suggests that
A. sp. 'Dandaragan' is resilient to fire.
Levels of innate seed dormancy were lower and tolerance to thermal shock
higher in A. sp. 'Dandaragan' compared with
A. microbotrya s. l. The population size, structure and
germination ecology suggest that A. sp.
'Dandaragan' does not appear to have any immediate management
requirements, apart from continued monitoring of adult plant health and
recruitment. The study confirms that A. sp. Dandaragan
should be recognised as Declared Rare (threatened) Flora and we recommend that
the taxon's conservation status be reviewed.
Anatomical variation in juvenile eucalypt leaves accounts for differences in specific leaf area and CO2 assimilation rates
Authors: Sefton Christine A. , Montagu Kelvin , Atwell Brian J. , Conroy Jann P.
Published: September 2002

Specific leaf area (SLA) is an important leaf attribute representing a compromise between the capture of light and CO2 and the limitations imposed by leaf structure, herbivore resistance and the mitigation of water loss. We examined three Eucalyptus L'Her. species to determine whether variation in CO2 assimilation rate was related to SLA and leaf anatomy. Seedlings were grown in a naturally illuminated glasshouse with adequate water and nutrients. Light-saturated rates of photosynthesis were measured on the youngest fully expanded leaves. Mesophyll characteristics were measured from sections thick of the interveinal leaf lamina. Significant interspecies variation in SLA corresponded to clear trends in anatomy and photosynthesis. Low-SLA leaves were thicker, having increased thickness of palisade mesophyll because of a greater number of palisade layers. E. occidentalis, E.camaldulensis and E. grandis had 3.7, 2.0 and 1.0 layers of palisade cells which corresponded to an SLA of 14.8, 17.6 and 21.8 m2 kg-1, respectively. High investment of dry mass in photosynthetic tissue was associated with higher leaf N (area and mass) concentration, chlorophyll concentration and photosynthetic capacity per leaf area. Leaf morphology affected use of the resources N, water and CO2. In contrast to the thin leaves of E. grandis, thick leaves of E. occidentalis had low N-use efficiency and high instantaneous water-use efficiency. Differences in leaf structure of these species appear to reflect the most limiting resource experienced in the environments to which they have adapted.
Self-incompatibility in Eucalyptus globulus ssp. globulus (Myrtaceae)
Authors: Pound L. M. , Wallwork M. A. B. , Potts B. M. , Sedgley M.
Published: September 2002

Controlled pollinations with self- and cross-pollen were applied to individual flowers of five mature Eucalyptus globulus Labill. ssp. globulus trees to investigate the site of action of the self-incompatibility mechanism. Growth of pollen tubes in styles at 2 weeks after pollination and ovule penetration by pollen tubes at 2 and 4 weeks after pollination were investigated by fluorescence microscopy. Some pollinated flowers were left to develop to seed maturity, then harvested to quantify the level of self-incompatibility of each tree. Trees ranged from 76 to 100% self-incompatible. There was no significant difference in the number of pollen tubes in the style between treatments although variation was present between trees. The number of pollen tubes present was similar to the number of ovules present within flowers. Penetration of ovules by pollen tubes over all five trees combined revealed no difference between treatments at 2 weeks after pollination; however, there was slightly greater penetration by cross-pollen tubes at 4 weeks after pollination. This difference was not large enough to account for the near complete lack of selfed-seed production, suggesting late pre- or post-zygotic arrest of selfed ovules.
Regeneration by three species of Banksia on the south coast of Western Australia in relation to fire interval
Authors: Wooller S. J. , Wooller R. D. , Brown K. L.
Published: September 2002

The regeneration strategies of three Banksia species in relation to fire were studied over 20 years in a mediterranean heathland-shrubland on the south coast of Western Australia. Banksia baueri and B. nutans are both bushes 1–2 m high, while B. baxteri is a shrub 4 m high. All three species regenerated only from seed released from the canopy seed bank after fire. They did not start to flower until 6 years after fire and seed set took even longer. Differences between the species in age-related intensity of flowering were related to the rate at which each species accumulated seed in the canopy. Even plants over 40 years old were still increasing their overall canopy seed bank or replacing seeds that had been released or were no longer viable. The vegetation studied appeared to be little affected by humans historically and to have burnt only at intervals of 30–60 years or more. Consequently, although all three species needed fire to regenerate, management of fire regimes needs to allow adequate intervals between fires for the replacement of their canopy seed banks. Indeed, all three Banksia species studied were extinguished from one area burnt twice at an interval of 9 years. Models developed with Banksia species from the northern sand plains of Western Australia, where fires appear more frequent, may need modification to be applicable to all south-coastal species.
An embryo-rescue protocol for Vigna interspecific hybrids
Authors: Palmer J. L. , Lawn R. J. , Adkins S. W.
Published: September 2002

A successful embryo-rescue and culture protocol was developed for use with several indigenous Vigna species and mungbean cultivars grown in Australia. Germination of Vigna immature embryos and their subsequent development into plants was influenced by the time at which the embryos were isolated and by which medium additives were placed in the embryo-rescue medium. A medium containing MS basal nutrients with sucrose (88�mM), casein hydrolysate (500 mg L-
1) and agar (8 g L-
1) but devoid of plant-growth regulators was found to be the best for germination of immature embryos for all four Vigna species investigated. The protocol for successful germination of non-hybrid immature embryos was applied to the recovery of interspecific hybrids involving mungbean and five native Vigna species that had previously been found difficult to hybridise. Several putative hybrid plants were obtained including a confirmed interspecific cross between V. luteola (Jacq.) Benth and V. marina (Burm.) Merrill.