bluuebunny/crossref_metadata_2025 huggingface dataset:
Does gregariousness function as an antipredator mechanism in the Mediterranean slipper lobster, Scyllarides latus?
Authors: Lavalli Kari L. , Spanier Ehud
Published: September 2002

The possible antipredation benefits of group living have been difficult to
study in species where the size and incidence of groups are beyond the
investigator’s control. A field test with tethered Mediterranean slipper
lobsters, Scyllarides latus, revealed that attack and
capture rates for solitary individuals did not differ significantly from those
for grouped individuals after either 3 or 24 h of exposure to potential
predators. Although predator attack rates on grouped and solitary lobsters
also did not differ after 3 h, they were significantly higher on groups than
on solitary lobsters after 24 h. Differences in fish behaviour during the
first hour of lobster exposure suggest that confusion effects played a role
only initially and, presumably, conferred a short-lived advantage on clumped
prey. Confusion effects were represented by a higher frequency of passes and
reapproaches for fish concentrating on grouped lobsters and a lower frequency
of bites. Attacks were more directed for fish concentrating on solitary
lobsters. With increasing exposure time, however, groups may have served to
facilitate predation because triggerfish
(Balistes carolinensis) were equally successful at
capturing grouped and solitary lobsters.
The spiny lobster fishery in the WECAFC region - an approach to responsible fisheries management
Authors: Cochrane K. L. , Cochrane K. L. , Chakalall B. , Chakalall B.
Published: September 2002

The Caribbean spiny lobster Panulirus argus is widely
distributed in the western central Atlantic and supports important fisheries
in many of the countries within this area. Total reported landings have been
between 27000 and 30000 tonnes per annum over the last decade. However, recent
assessments undertaken under the auspices of the Western Central Atlantic
Fisheries Commission (WECAFC) have indicated that the resource is being fully
or over-exploited over much of its range. The results also revealed widespread
deficiencies in the data available, which create problems in undertaking
reliable assessments and in the subsequent provision of management advice. The
studies, undertaken with full regional participation, suggested that in most
countries the need is urgent to control and frequently to reduce fishing
effort for the species and that in some countries both spawner biomass and
potential yield would benefit from increases in the minimum size of the
lobsters caught. This paper describes the fisheries for Caribbean spiny
lobster, including their socio-economic importance in the region. It provides
an over-view of the results of the 1997 and 1998 WECAFC workshops on the
species and of the implications of those results for management for
sustainable use. Finally, the need for regional, or, at least, subregional,
management of the fisheries is discussed, with reference to the conclusions of
the WECAFC 2000 workshop.
Numerical modelling of tide-induced residual circulation in Sydney Harbour
Authors: Das Pritha , Marchesiello Patrick , Middleton Jason H.
Published: September 2002

Tide-induced residual circulation and
dispersion in Sydney Harbour has been studied with a vertically integrated,
two-dimensional, primitive equation model. The tide-induced residual
circulation consists of a series of recirculating gyres that are due to the
interaction of the tidal current with the complex coastal geometry and
bathymetry of the harbour. Inclusion of the S2 tide and
homogeneous wind stress in the input forcing does not significantly change the
residual circulation pattern. Residuals are produced mainly by the
M2 tide and there is no significant nonlinear
interaction between the M2 and the
S2 tide. Tracer simulations show that tidal mixing is
limited in the vicinity of the entrance and the flushing rates of different
segments of the harbour vary significantly. Lack of similarity between the
Eulerian and Lagrangian residual fields demonstrates that the net displacement
of material released during a particular phase of the tide has little
connection with the mean current observed at fixed locations and is extremely
sensitive to the timing and location of release.
Algal motility measured by a laser-based tracking method
Authors: Vladimirov V. A. , Denissenko P. V. , Pedley T. J. , Wu M. , Moskalev I. S.
Published: September 2002

The velocities of individual actively swimming cells of the green alga
Chlamydomonas nivalis can be measured with the use of
spatial displacements of their successive images (by a ‘tracking’
method). This paper proposes a new tracking method based on the use of laser
light; it is common for the tracking of passive particles, but the case of
actively swimming cells presents specific problems. The first problem is the
potential influence of the laser light on the behaviour of the cells. A key
result of the study is that for carefully chosen parameters the effect of the
laser light on the algal swimming is negligible (below the measurement error).
Hence, the self-swimming velocities can be measured; sample results are given.
The proposed method permits a large measurement volume, and thus allows the
velocities of several hundreds of cells to be measured simultaneously. From
these data an approximation for the probability distribution function of the
velocities of the cells can be derived; this function is crucial for the
construction of mathematical models of algal motility. The laser-based
tracking method is applicable and useful for measurements of algal motion in
still fluid. The method thus presents new opportunities in this area of
research.
Influence of climate,geology and humans on spatial and temporal nutrient geochemistry in the subtropical Richmond River catchment, Australia
Authors: McKee Lester J. , Eyre Bradley D. , Hossain Shahadat , Pepperell Peter R.
Published: September 2002

Water quality was monitored on a spatial and temporal basis in the subtropical
Richmond River catchment over two years. Nutrient concentrations varied
seasonally in a complex manner with highest concentrations (maximum
=3110 µg N L – 1 and 572 µg P L
–1 ) associated with floods. However, median (444
µg N L – 1 and 55 µg P L
– 1 ) concentrations were relatively low compared
with other parts of the world. The forms of nitrogen and phosphorus in streams
varied seasonally, with greater proportions of inorganic nitrogen and
phosphorus during the wet season. Minimum nutrient concentrations were found
2—3 months after flood discharge. With the onset of the dry season,
concentration increases were attributed to point sources and low river
discharge. There were statistically significant relationships between geology
and water quality and nutrient concentrations increased downstream and were
significantly related to population density and dairy farming. In spite of
varying geology and naturally higher phosphorus in soils and rocks in parts of
the catchment, anthropogenic impacts had the greatest effects on water quality
in the Richmond River catchment. Rainfall quality also appeared to be related
both spatially and seasonally to human activity. Although the responses of the
subtropical Richmond River catchment to changes in land use are similar to
those of temperate systems of North America and Europe, the seasonal patterns
appear to be more complex and perhaps typical of subtropical catchments
dominated by agricultural land use.
Geochemistry of deep-sea sediment cores and their relationship with polymetallic nodules from the north-eastern Pacific
Authors: Rosales-Hoz L. , Carranza-Edwards A.
Published: September 2002

Eight sediment cores from the oceanic area close to Clarion Island in the
Mexican Economic Exclusive Zone were studied to evaluate their metal content
and their relationship to the nodules present in the area. The cores from
closer to the East Pacific Rise near 21ºN showed high concentrations of
organic matter and Zn, and the lowest concentrations of Fe and Mn. The cores
from the Mimar Depression, 166 nmiles south-west of Clarion Island, showed the
highest concentration of Fe, Mn, Cu, Ni, and Co in sediments and the highest
nodule abundance;this may be related to slower bottom currents. Cores 18 and
20 showed significant correlation of Mn with Cu, Ni, and Co, suggesting that
these metals are precipitated with the Mn oxides. Core 25 showed a strong
correlation of Fe with Mn, indicating different chemical processes. The MnO:
Al2O3 ratio was used to evaluate
the different sediment sources, and this allowed differentiation of the areas
affected by the hydrothermal discharges. Factor analysis of the compositional
data produced four major factors—diagenetic, hydrothermal, biogenic and
detritic—that together account for 74. 3%of the sample variance.
Resumen. Se estudió el contenido de metales y su
relación con nódulos polimetálicos presentes en ocho
núcleos de sedimentos localizados en el área oceánica
inmediata a la isla Clarión en la Zona Económica Exclusiva de
México. Los núcleos cercanos a 21ºN de la Dorsal del
Pacífico Oriental muestran altas concentraciones de materia
orgánica y zinc y los valores más bajos de Fe y Mn. Los
núcleos localizados en la Depresión Mimar, 166 mn al SW de la
Isla Clarion, tienen los valores más altos de Fe, Mn, Cu, Ni y Co en
sedimentos así como la mayor abundancia de nódulos en el
área, esto puede deberse a menor velocidad de las corrientes de fondo.
Los nucleos 18 y 20 muestran correlaciones estadisticamente significativas de
Mn con Cu, Ni y Co, lo que sugiere que estos metales se precipitan con los
óxidos de Mn. El nucleo 25 muestra una fuerte correlación entre
Fe y Mn lo que sugiere comportamientos químicos diferentes en
éste nucleo. A través de la relación
MnO:Al2O3 se infiere el origen de
los sedimentos, y se puede reconocer el área afectada por las descargas
hidrotermales. El análisis de factores señala la existencia de
cuatro factores: diagénetico-hidrotermal-biogénico-detritico,
los cuales explican 74. 3%de la variancia de la muestra.
Utilization of nitrogen and carbon by phytoplankton in Moreton Bay, Australia
Authors: O'Donohue M. J. , Glibert P. M. , Dennison W. C.
Published: September 2002

Water samples were collected within river mouths, at river plume sites and at
well flushed ocean-influenced sites within Moreton Bay, a shallow subtropical
embayment in south-eastern Queensland. Rates of inorganic nitrogen
(NH+4 and NO-3) and carbon
uptake were determined across temporal and spatial scales by use of
15N and 14C incorporation.
Phytoplankton productivity, measured as CO2 uptake, was
highest at the river mouths. Rates of NH+4 uptake
exceeded rates of NO-3 uptake at all sites at all times.
Relative preference indices demonstrated a consistent preference by
phytoplankton for NH+4 uptake, and
NH+4 uptake rates were higher at ocean-influenced
sites than at river-mouth sites. Inorganic nutrient and chlorophyll
a concentrations were highest at river mouths; however,
the greatest NH+4 uptake occurred at the
ocean-influenced sites, reflecting a greater dependence on
‘recycled’ N than on ‘new’ N. Biomass-independent
NH+4 uptake increased with increasing water
temperature; however, NO-3 uptake increased with
decreasing water temperature, reflecting the lower temperature optimum for
nitrate reductase. The range of NH+4 and
NO-3 uptake rates was greater than ranges reported for
other coastal waters, reflecting the strong temporal and spatial gradients
within Moreton Bay. This trend of strong gradients in C and N dynamics from
oligotrophic to river-influenced waters with seasonal flows is likely to exist
in many tropical and subtropical coastal waters of Australia.
Reproductive biology of the Australian herring Arripis georgiana
Authors: Fairclough D. V. , Dimmlich W. F. , Potter I. C.
Published: September 2002

Arripis georgiana was collected from along the Western
Australian and South Australian coasts at regular intervals between October
1996 and December 1998. The trends exhibited during the year by gonadosomatic
indices, gonadal maturity stages and oocyte stages demonstrate that spawning
is restricted to south-western Australian waters from at least as far north as
~28˚43′S to as far east as ~119˚24′E, and that it occurs
mainly during late May and early June. The simultaneous presence of
post-ovulatory follicles and hydrated and yolk-granule oocytes in some ovaries
during the spawning period indicates that A. georgiana
is a multiple spawner, i.e. females spawn more than once in a breeding season.
In south-western Australia, where all life-cycle stages are found, the overall
sex ratio in catches collected by netting was close to parity, whereas females
predominated in those obtained by anglers. The length at which 50% of
fish reached maturity was 197 mm for females and 179 mm for males, and just
over 50% of females and ~80% of males attained maturity at the
end of their second year of life. The implications of these data for
management of the fishery for A. georgiana are
discussed.
Anomalous current structure in the eastern equatorial Indian Ocean during the south-west monsoon of 1994
Authors: Unnikrishnan A. S. , Murty V. S. , Babu M. T. , Gopinathan C. K. , Charyulu R. J. K.
Published: September 2002

Analysis of hydrographic data collected along 80°, 84° and
88°E between 5 °N and 3 °S during peak south-west
monsoon (July–August) of 1994 in the eastern equatorial Indian Ocean
(EEIO) reveals thermohaline variability and anomalous current structure in the
upper ocean. A warm (28.4–28.8°C) and less-saline (33 to 34.8)
deep (60-75m) homogeneous layer characterizes the surface mixed layer. The
south-west monsoon current, advecting the Arabian Sea High Salinity Water
eastwards,appears as an eastward undercurrent (˜50 cm
s–1) below 125 m at 80 °E between 1
°and 1.5 °N and in the upper 100 m in the vicinity of the
equator with an eastward increase of core velocity between 75 and 100 m. This
undercurrent has a transport of 4 Sv at 80 °E. The westward flow in
the upper layers north of the equator is anomalous, as the surface winds have
an eastward zonal component. The associated westward transport is 44 Sv
between 84 °and 88 °E. This equatorial westward flow appears
to be influenced by the anomalously strong north-westward coastal current off
Sumatra and westward propagating Rossby waves.
Yellowfin tuna (Thunnus albacares) aggregations along the shelf break off south-eastern Australia: links between inshore and offshore processes
Authors: Young J. W. , Bradford R. , Lamb T. D. , Clementson L. A. , Kloser R. , Galea H.
Published: September 2002

In May 1996 the biological oceanography of the main yellowfin tuna longline
fishing waters off southern New South Wales, Australia, was examined in
relation to the catch by the fishery. A warm-core eddy was identified directly
east of Eden with a temperature at 250 m depth of 15˚C. At the western
edge of this eddy, relatively high levels of fluorescence (chlorophyll
a) were recorded together with pigments typical of
diatoms, a feature of upwelling communities. The biomass of zooplankton and
micronekton was also significantly higher at the western edge of the eddy.
Similarly, acoustic data showed relatively high concentrations of backscatter
at the margins of the eddy, particularly at the shelf break and slope. These
areas had the greatest potential prey biomass; a fact supported by the
presence of shelf-and slope-associated prey species in the stomachs of
yellowfin tuna caught at the same time. Fishery data for yellowfin tuna
(Thunnus albacares) captures showed that catch per unit
effort was highest along the shelf and shelf break. Examination of yellowfin
tuna catch records from 1988 to 1998 from south-eastern Australia showed
highest catches in 1996, ~75%of the catch coming from the western edge
of the eddy. We conclude that the presence of a warm-core eddy in the area at
this time provided a localized but productive area to which the yellowfin were
attracted.
Larval distribution of blue grenadier (Macruronus novaezelandiae Hector) in south-eastern Australia: further evidence for a second spawning area
Authors: Bruce Barry D. , Condie Scott A. , Sutton Caroline A.
Published: September 2002

Small numbers of blue grenadier,
Macruronus novaezelandiae, larvae were found in coastal
waters off eastern Victoria and southern New South Wales in August 1993. This
is the first record of larval blue grenadier from mainland Australian waters.
It is considerably further north than previous records of larvae and remote
from the single known spawning ground off western Tasmania. Larvae were aged
between 17 and 36 days and were largely confined to an inshore northward
flowing water mass. Back calculated spawning dates indicated that larvae from
eastern Victoria/southern NSW were spawned earlier than larvae collected
during the same period off western and southern Tasmania. Otolith increment
widths were significantly wider in larvae caught in eastern
Victoria/southern NSW suggesting that they experienced faster growth and
development conditions than the Tasmanian larvae. Three-dimensional modelling
of circulation and particle advection suggested that the source of eastern
Victoria/southern NSW larvae was most likely eastern Bass Strait. These
data suggest that there is a second, albeit limited, spawning area for blue
grenadier in south-eastern Australia.
Polymorphism in cyanogenic glycoside content and cyanogenic β-glucosidase activity in natural populations of Eucalyptus cladocalyx
Authors: Gleadow Roslyn M. , Woodrow Ian E.
Published: September 2002

Cyanogenesis is the process by which plantsrelease hydrogen cyanide (HCN) from endogenous cyanide-containing compoundsand is thought to play a role in plant defence against generalist herbivores.Cyanogenesis is poorly understood in natural populations, and has been littlestudied in tree species. In this paper we present the first systematic surveyof cyanogenesis in the economically and ecologically important genusEucalyptus. We document variability in both theconcentration of the cyanogenic glycoside, prunasin, and the accompanyingdegradative b-glucosidase in a woody plant for the first time. Leaves of 96E. cladocalyx F. Muell. trees growing in naturalpopulations on Kangaroo Island, South Australia were analysed. All trees werecyanogenic, containing both cyanogenic glycosides and active b-glucosidase.Cyanogenic glycoside concentration varied by over two orders of magnitude. Theb-glucosidase activity varied widely as well, but plants high in cyanogenicglycosides did not necessarily have higher enzyme activity. A significantproportion of the variation in cyanogenic glycoside concentration can beaccounted for by the variation in leaf nitrogen. Most of the variation,however, appears to be the result of genetic polymorphism, which is inheritedindependently of the level of activity of the degradativeb-glucosidase.
Phenolic compounds and oxidative metabolism in green bean plants under nitrogen toxicity.
Authors: Sánchez Esteban , Soto Juan M. , García Pablo C. , López-Lefebre Luis R. , Rivero Rosa M. , Ruiz Juan M. , Romero Luis
Published: September 2002

The objective of the present work was to determine the effect of nitrogen
toxicity on the metabolism of phenolic compounds and of oxidative stress in
Phaseolus vulgaris L. cv. Strike. The nitrogen was
applied to the nutrient solution as
NH4NO3 at 5.4, 10.8, 16.2, 21.6
and 27 mM. The results indicate that the application of 27 mM N can be defined
as toxic, as it drastically depressed growth of the green bean plants in our
experiment. In addition, the abiotic stress from the application of this N
dosage inhibited the enzymes polyphenol oxidase, peroxidase and cata-lase, and
stimulated phenylalanine ammonia-lyase and superoxide dismutase activities.
The result was foliar accumulation of phenolic compounds and hydrogen peroxide
(H2O2). The accumulation of
H2O2 also apparently caused a
reduction in biomass production.
Commonality of root nodulation signals and nitrogen assimilation in tropical grain legumes belonging to the tribe Phaseoleae.
Authors: Dakora Felix D.
Published: September 2002

The tribe Phaseoleae (family Leguminosae) is home to many of the annual food
legumes cultivated in the tropics. Cowpea
(Vigna unguiculata (L.) Walp.), Bambara groundnut
(Vigna subterranea (L.) Verdc.), Kersting’s bean
(Macrotyloma geocarpum L.), mung bean
(Vigna radiata (L.) Wilczek) and common bean
(Phaseolus vulgaris L.), all belonging to subtribe
Phaseolinae, and together with soybean (Glycine max (L.)
Merr., subtribe Glycininae) and pigeon pea
(Cajanus cajan L., subtribe Cajaninae), are important
members of the tribe Phaseoleae. These legumes are unique in their use of
identical root chemical molecules to induce the expression of nodulation genes
in their respective homologous microsymbionts during nodule formation. Of
those studied so far, common bean, soybean, Bambara groundnut,
Kersting’s bean and cowpea all use the isoflavones daidzein, genistein
and coumestrol as root exudate signals to induce the expression of
nod genes in their rhizobial partners. Additionally,
members of the Phaseoleae tribe are easily recognised on the basis of their
tropical biogeographic origin, broad host nodulation habit, route of
Rhizobium entry into roots, chemotaxonomy and use of a
common isoflavone biosynthetic pathway, determinate nodulation phenotype and
internal nodule anatomy, xylem composition and transportable solutes of fixed
N, site of NO3– reduction
and metabolic response of N2-fed plants to
NO3– supply. These shared
traits and their potential application for agriculture are discussed in this
review.
Radiation and nitrogen use at the leaf and canopy level by wheat and oilseed rape during the critical period for grain number definition.
Authors: Dreccer M. Fernanda , Schapendonk Ad H. C. M. , van Oijen Marcel , Pot C. Sander , Rabbinge Rudy
Published: September 2002

During the critical period for grain number definition, the amount of biomass
produced per unit absorbed radiation is more sensitive to nitrogen (N) supply
in oilseed rape than in wheat, and reaches a higher value at high N. This
response was investigated by combining experimental and modelling work.
Oilseed rape and wheat were grown at three levels of N supply, combined with
two levels of plant density at high N supply. Canopy photosynthesis and
daytime radiation use efficiency
(RUEA) were calculated with a
model based on observed N-dependent leaf photosynthesis and observed canopy
vertical distribution of light and leaf N. In oilseed rape,
RUEA was higher than in wheat and,
in contrast to wheat, the sensitivity to canopy leaf N content increased from
the start to the end of the critical period. These results were partly
explained by the higher leaf photosynthesis in oilseed rape
vs wheat. In addition, oilseed rape leaves were
increasingly shaded by the inflorescence. Thus,
RUEA increased because more leaves
were operating at non-saturating light levels. In both species, the vertical
distribution of leaf N was close to that optimising canopy photosynthesis. The
results are discussed in relation to possibilities for improvement of N
productivity in these crops.
Duration of the stem elongation period influences the number of fertile florets in wheat and barley.
Authors: Miralles Daniel J. , Richards Richard A. , Slafer Gustavo A.
Published: September 2002

Yield increases in temperate cereals have been associated with increases in
grain number. An experiment was conducted to investigate whether altering the
duration of the stem elongation period in wheat and barley increases floret
fertility and thereby grain number. A photoperiod-responsive spring wheat
(UQ189) and spring barley (Arapiles) were grown in a naturally lit phytotron.
Plants were grown at constant (9, 13 and 19 h) and reciprocally interchanged
photoperiod [at terminal spikelet (TS, wheat) or triple mound (TM,
barley)] to alter the duration of the stem elongation period. An
increased duration of the late reproductive phase from TS to heading in wheat
resulted in more fertile florets per spike. A similar relationship was
observed in barley but only for a limited range of duration of the stem
elongation period. Shorter photoperiods reduced the rate of floret development
and extended the time to reach the fertile floret stage. The fact that the
duration of the late reproductive phase during which the spike and stem
competing for assimilates was associated with the number of fertile florets
per spike suggests that extending the stem elongation period in cereals could
be a way to reduce assimilate competition and thereby increase the number of
fertile florets and grain yield.
Sensitivity of field-grown soybean to future atmospheric CO2: selection for improved productivity in the 21st century.
Authors: Ziska Lewis H. , Bunce James A.
Published: September 2002

Although genotypic differences among soybean
(Glycine max (L.) Merr.) cultivars in their response to
future CO2 partial pressures have been observed in the
glasshouse, it is unclear if similar responses would occur among cultivars
when grown under field conditions at normal stand densities. To determine
variation in the sensitivity of soybean growth and seed yield to
CO2, we grew two contrasting cultivars of the same
maturity group, Ripley (semi-dwarf, determinate) and Spencer (standard,
indeterminate), to reproductive maturity at ambient and elevated (30 Pa above
ambient) CO2 partial pressures for two field seasons.
Spencer had been previously selected in glasshouse trials as responsive to
increased CO2. Significant cultivar x
CO2 interaction was observed for both vegetative biomass
and seed yield, with Spencer demonstrating a consistently greater yield
enhancement at elevated CO2 than Ripley (60
vs 35%, respectively). Differences in CO2
sensitivity between cultivars were not evident in measurements of single leaf
photosynthesis taken during anthesis, nor early or late pod-fill. Analysis of
reproductive characteristics indicated that the sensitivity of the seed yield
response to CO2 in Spencer was associated with the
ability to form additional seed on axillary branches in response to elevated
CO2. Data from this experiment suggest that screening of
soybean germplasm at the glasshouse level, when combined with field trials,
may be an effective strategy to begin selecting soybean lines that will
maximize yield in a future, higher CO2 environment.
Assimilate transport and partitioning. Integration of structure,
physiology and molecular biology
Authors: Offler Christina E. , Thorpe Michael R. , Patrick John W.
Published: September 2002

The papers in this Special Issue of AjPP were submitted by
keynote speakers who participated in the International
Conference on Assimilate Transport and Partitioning
(ICATP�99) held at Newcastle Convention Centre,
Newcastle, Australia during 15�20 August, 1999. ICATP�99
was co-convened by Tina Offler, The University of
Newcastle and Michael Thorpe, HortResearch, New
Zealand. It was the sixth in a series of International
Conferences since 1974 and was attended by 220 delegates
from 21 countries. ICATP�99 opened with a pre-conference
dinner at which an aboriginal elder and custodian of the
Mimaga Wajaar (Mother Earth) culture, Uncle Bill Smith,
warmly welcomed delegates to the Awabakal tribal lands of
local indigenous ancestors with a message to freely share
knowledge. This point was further developed in an afterdinner
speech by Don Geiger (Dayton, USA), a founding
member of this series. Delegates transformed these sentiments
into effect throughout the scientific program, rendering
ICATP�99 a rewarding and valuable experience for all.
The next conference will be convened in Germany during
2003.
Polyphenol oxidase is induced by chilling and wounding in pineapple
Authors: Stewart Richard J. , Sawyer Brett J. B. , Bucheli Carolyn S. , Robinson Simon P.
Published: September 2002

Polyphenol oxidase (PPO) activity was found to be low in the leaves, roots,
inflorescence tissues and developing and mature fruit of pineapple
(Ananas comosus L.). In fruit affected by the
chill-induced internal browning disorder known as Blackheart, PPO activity was
10-fold higher than in unaffected fruit, and there was a direct correlation
between PPO activity and the severity of Blackheart symptoms. Degenerate
oligonucleotide primers were designed to conserved regions of plant PPO genes,
and used to amplify two distinct pineapple PPO cDNAs, designated PINPPO1 (2181
bp) and PINPPO2 (1319 bp), which share 81% sequence identity at the DNA
level and show a high degree of homology to other plant PPO genes. PINPPO1
encodes a peptide of 604 amino acids, including a putative transit peptide of
95 amino acids and two copper-binding regions, CuA and CuB, which are highly
conserved in plant PPOs. Southern analysis suggested the presence of at least
four PPO genes in pineapple. Expression of PINPPO1 and PINPPO2 was low in
roots, leaves, inflorescence tissues and developing fruit, but was strongly
up-regulated in response to chilling and wounding. These results indicate that
PPO is synthesised de novo in response to chilling of
pineapple fruit, and implicate a role for the enzyme in the development of
Blackheart disorder.
Iron resupply-mediated deactivation of Fe-deficiency stress responses in roots of sugar beet
Authors: López-Millán Ana Flor , Morales Fermín , Gogorcena Yolanda , Abadía Anunciación , Abadía Javier
Published: September 2002

Different root zones with or without increased Fe-reducing activities have
been studied in Fe-deficient sugar beet (Beta vulgaris
L.) plants after Fe resupply to the nutrient solution. The subapical regions
of roots from Fe-deficient plants decreased by 19 and 88% their
capacity to reduce ferric chelates after 24 and 96 h of Fe resupply,
respectively. Iron resupply caused 52 and 96% decreases in
phosphoenolpyruvate carboxylase activity in root
extracts after 24 and 96 h, respectively, and also caused general decreases in
other enzyme activities involved in carboxylic acid metabolism. The large
pools of carboxylic acids in Fe-deficient roots decreased by 9 and 48%
after 24 and 96 h of Fe resupply, respectively. The activities of pyruvate
decarboxylase and lactate dehydrogenase, enzymes related to anaerobic
metabolism, decreased by 88% after 24 h of Fe resupply. The
mitochondrial quinone and pyridine nucleotide pools became more oxidised in
the Fe-deficient root tips after Fe resupply. Iron resupply caused a
70% decrease in root oxygen consumption rates 96 h after Fe resupply.
Results indicate that deactivation of the Fe deficiency stress responses of
sugar beet roots upon Fe resupply occurs in a progressive manner in a time
scale of several days.
Influence of high temperature during pre- and post-anthesis stages of floral development on fruit-set and pollen germination in peanut
Authors: Vara Prasad Pagadala V. , Craufurd Peter Q. , Kakani Vijay G. , Wheeler Timothy R. , Boote Kenneth J.
Published: September 2002

Peanut (Arachis hypogaea L.) crops are often exposed to
day temperatures > 35°C for short periods duringflowering,
resulting in lower yields. Research was conducted to study and quantify the
effects of short episodes (1– 6 d) of high temperatures during the pre-
and post-anthesis stages of floral development on fruit-set, pollen viability,
germination and tube growth. Plants of peanut cv. ICGV-86015 were grown in
controlled environments at 28/22°C (day/night). High daytime
air temperature treatments ranging from 28 (control) to 48°C were
imposed at different times between 6 d before anthesis (DBA) and 6 d after
anthesis (DAA) for 1, 3 or 6 d. Floral buds or flowers were tagged at
different stages to determine fruit-set. Exposure to bud (tissue) temperature
≥ 39°C for 1 d significantly reduced fruit-set compared to the
control at 28°C, and the magnitude of the reduction varied with stage
of floral development. Floral buds were most sensitive to high temperature at
4 DBA and at anthesis, coinciding with micro-sporogenesis and pollination or
fertilisation, respectively. The critical bud temperature at these stages was
33°C, above which fruit-set was reduced by 6% °C
–1 . Lower fruit-set due to high temperatures at
pre-anthesis and anthesis stages were due to pollen sterility and retarded
pollen tube growth, respectively.
The effect of rht genotype and temperature on coleoptile growth and dry matter partitioning in young wheat seedlings
Authors: Botwright Tina , Rebetzke Greg , Condon Tony , Richards Richard
Published: September 2002

Coleoptile length in wheat (Triticum aestivum L.) can be
affected by several factors, including genotype, height-reducing genes and
environmental factors, including temperature. There is little information on
how these factors influence rate and duration of coleoptile growth to
determine final coleoptile length in wheat. Coleoptile growth was determined
for eight genotypes representing four different height-reducing genes:
gibberellic acid (GA)-sensitive, standard height (rht),
GA-sensitive semidwarfs (Rht8); and GA-insensitive,
semidwarfs (Rht2). These were grown in the dark at three
temperatures (12, 16 and 20˚C) and coleoptile lengths measured every
12˚Cd. Logistic growth curves were fitted to coleoptile growth data for
each genotype with thermal time as the explanatory variable. Differences in
final coleoptile length were largely attributable to differences in rate of
coleoptile elongation although there were small differences in duration of
growth between genotypes. The longer coleoptile of the
rht wheats was achieved through the fastest rate of
coleoptile elongation. Coleoptiles of Rht8 wheats were
equivalent in final length to rht wheats at 107 mm, but
achieved this through a slower growth rate (2.10 mm
˚Cd–1) combined with an increased duration of
growth (57˚Cd). In contrast, the shorter coleoptiles of
Rht2 wheats resulted from 25% slower rates of
elongation than either Rht8 or
rht. There were no interactions between the components
of coleoptile growth and temperature, although a longer duration and a fast
rate of growth combined to increase coleoptile length at 12˚C compared
with either 16 or 20˚C. In a second experiment, dry matter partitioning
and length of coleoptile, subcrown internode (SCI), shoot and roots were
determined after 200˚Cd. In Rht2, the SCI and shoot
were short while roots were longer than either Rht8 or
rht. Reduced dry matter (DM) partitioning to the
coleoptile and SCI and DM retention in the seed reduced the endosperm-use
efficiency (EUE) of Rht compared with
rht. EUE was poor also in Rht8,
apparently through increased respiratory losses. Reduced partitioning of dry
matter to coleoptiles and the SCI in Rht2 increased the
root : shoot ratio compared with rht or
Rht8. We conclude that either increased rate or duration
of coleoptile growth could be targeted in a breeding program that aims to
increase coleoptile length in wheat.
Germination inhibitors in bracts surrounding the grain of Triticum tauschii
Authors: Gatford Keith T. , Eastwood Russell F. , Halloran Gerald M.
Published: September 2002

Pre-harvest sprouting of bread wheat is a cause of considerable economic losses for the Australian wheat industry. In this study, we have used Triticum tauschii (Coss.) Schmahl., the donor of the D-genome to bread wheat, and identified water-soluble germination inhibitors in its bracts. Germination of non-dormant T. tauschii grains was significantly delayed by imbibition in undiluted leachate (crude extract) from the bracts, whereas any dilution of the crude extract (1/10, 1/100 or 1/1000) resulted in no inhibition. Removal of proteins larger than 10 kDa from the crude extract resulted in increased germination inhibition compared with the crude extract. When purified, free phenolic compounds present in the crude extract were found to inhibit germination, but to a lesser extent than the crude extract, possibly due to losses during purification. HPLC of the free phenolic fraction indicated the presence of more than 30 compounds. Peak fractions were collected and tested for inhibitory properties. Two fractions significantly inhibited grain germination for 3 d, with one fraction, determined to contain vanillic acid, continuing to inhibit germination after 5 d. Exogenously applied vanillic acid at a concentration of 0.2 mg mL-1 was shown to significantly inhibit germination compared with water-imbibed grains. The germination inhibitor mechanism detected in the bracts surrounding the grain of T. tauschii in this study has the potential to provide protection against pre-harvest sprouting in bread wheat.
Antioxidant system response of different wheat cultivars under drought: field and in vitro studies
Authors: Lascano Hernán R. , Antonicelli Gerardo E. , Luna Celina M. , Melchiorre Mariana N. , Gómez Leonardo D. , Racca Roberto W. , Trippi Victorio S. , Casano Leonardo M.
Published: September 2002

The participation of the antioxidant system in the drought tolerance of wheat
cultivars (Triticum aestivum L.) was studied under field
and in vitro conditions. Under field conditions, drought
tolerance was evaluated by the capacity to maintain the grain yield under
drought, which was higher in cvv. Elite and La Paz than in the sensitive cvv.
Oasis and Cruz Alta. Tolerant cultivars showed lower relative water content
(RWC) and lower above-ground vegetative biomass than sensitive cultivars.
Field assays did not show a clear correlation between water-stress tolerance
and antioxidant system behaviour. However, when leaves of cvv. with
contrasting drought tolerance were subjected to osmotic stress
in vitro, clear differences in the antioxidant system
activity and oxidative damage between cvv. were observed. In the tolerant
cultivar Elite, it was possible to observe an increase in ascorbate peroxidase
(APX), superoxide dismutase (SOD) and glutathione reductase (GR) activities, a
higher glutathione (GSH) and ascorbate content and less oxidative damage than
in the sensitive cultivar Oasis, which showed no changes or only slight
decreases in the enzyme activities. These results indicate that water stress
tolerance is in part associated with the antioxidant system activity, and
suggest that the behaviour of the antioxidant
systemin vitro assays can be used as an early selection
tool.
Biological nitrogen fixation associated with tropical pasture grasses
Authors: Reis Veronica M. , Jr Fábio B. dos Reis , Quesada Diego M. , Oliveira Octávio C. A. de , Alves Bruno J. R. , Urquiaga Segundo , Boddey Robert M.
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
The semi-humid or humid tropics are ideal for the production of large
quantities of biomass from fast-growing C4 grasses, but
high yields normally require large quantities of fertiliser, especially N,
which has a very high input from fossil fuels (natural gas). A program has
been started recently to use elephant grass
(Pennisetum purpureum Schum.) to substitute firewood as
a fuel and also to make charcoal for iron production. In this case, any large
N fertiliser additions would mean that the yield of bio fuel per unit of
fossil fuel invested would be detrimentally affected. In this study, we report
on the potential for the selection of genotypes of fast-growing
C4 tropical grasses of the genera
Pennisetum and Brachiaria for
their capacity to obtain N inputs from plant-associated biological nitrogen
fixation (BNF). Fourteen genotypes each of Brachiaria
and Pennisetum were screened for BNF contributions by
growing them in 15N-labelled soil. In the case of the
Pennisetum, after a suitable cutting height for the crop
had been selected, there were large differences in dry matter production, N
accumulation and 15N enrichment. The differences in
15N enrichment between genotypes were statistically
significant and BNF inputs were estimated as high as 41% of accumulated
N. In the study on Brachiaria genotypes, potential
inputs of BNF seemed lower. Only one or two genotypes of
B. brizantha and B. ruziziensis
obtained more then 20% of their N from BNF. The
N2-fixing bacteria that were most commonly associated
with shoots and roots the Pennisetum genotypes were of
the genus Herbaspirillum, but predominantly of a
recently described new species. The Brachiaria spp. from
three different sites (Rio de Janeiro, Goânia, Bahia) were predominately
colonised by Azospirillum spp., most of the isolates
being of the species Azospirillum amazonense. Very few
Herbaspirilla were isolated from these plants.
Review: Unravelling the functional relationship between root anatomy and stress tolerance
Authors: Maggio Albino , Hasegawa Paul M. , Bressan Ray A. , Consiglio M. Federica , Joly Robert J.
Published: September 2002

Salinity is a major environmental constraint limiting the yield of crop plants
in many semi-arid and arid regions. A recently developed biophysical model for
plant growth in saline environments confirms a critical role for root
morphology and hydraulic properties in salinity and soil water deficit
tolerance. The identification of genes based on correlations between exposure
to salt stress and gene expression in roots and other organs has to date
proved to be only marginally successful as a strategy for improving plant salt
tolerance. Recently, the identification of genes that function in stress
tolerance has advanced considerably by using genetic mutation analysis.
However, the power of a genetic approach to understanding the specific
mechanisms of root adaptation to saline and osmotic stress environments has
not been fully exploited. A review of the available, yet still incomplete,
collection of root mutants in Arabidopsis and other
species demonstrates the potential usefulness of such mutants as tools in the
genetic dissection of root function under osmotic stress. Identification of
genes responsible for changes in root morphology that might also be
advantageous in the presence of salt stress may open new avenues towards the
elucidation of critical mechanisms for plant salt tolerance.
Enhanced shoot regeneration in nine Australian wheat cultivars by spermidine and water stress treatments
Authors: Khanna Harjeet K. , Daggard Grant E.
Published: September 2002

The regeneration potential of ageing calli initiated from isolated scutella of
immature embryos was increased in nine elite Australian cultivars (QT7208,
QT9685, QT7709, Kennedy, Lang, Sunvale, Giles, Petrie and Veery) of wheat
(Triticum aestivum L.). Firstly, the effects of
4–32 h of dehydration stress on regeneration of 4- to 20-week old calli
were evaluated. Cultivars such as Veery, Kennedy and Sunvale showed
significant improvement in regeneration from calli up to 12-weeks old that had
undergone 16 h of dehydration stress. Secondly, 4- to 20-week old callus
cultures were treated with 0.05–5 mM spermidine to evaluate its effect
on regeneration. While spermidine had a negative effect on regeneration from
4-week old calli at all tested concentrations (as compared with untreated
controls), there was a 3–50% improvement in the regeneration
ability of older calli (16- to 20-week old) of all cultivars. Finally,
exogenous application of 1 mM spermidine to 16-week old cultures, in
combination with 16 h dehydration stress, improved plant regeneration by
10–65% in all nine cultivars.
Root growth inhibition by low temperature explains differences in sugar accumulation between spring and winter wheat
Authors: Equiza María A. , Tognetti Jorge A.
Published: September 2002

Exposure to low temperatures is associated with an increased concentration of
carbohydrate (mainly sugar) in tissues of cool temperate species. Within a
species, carbohydrate concentration is usually much higher in winter cultivars
than in spring ones, frequently correlates well with winter survival, and is
also related to the expression of several genes. It has been proposed that
either a smaller reduction in carbon assimilation, or greater growth
inhibition by cold in winter cultivars, might explain this differential
increase in carbohydrate concentration. However, little experimental support
for these hypotheses is available. In this work, carbon assimilation and
growth, as related to the cold-induced increase in carbohydrate concentration,
are analysed in contrasting wheat (Triticum aestivum L.)
genotypes. No significant differences in the degree of cold-induced reduction
of carbon assimilation between cultivar types were found. Also, shoot growth
was similarly inhibited by cold in both winter and spring cultivars. However,
root growth rates were lower in cold-treated winter cultivars than in spring
ones, which led to much larger root systems in the latter. A simple method for
quantitatively estimating the contribution of cold-induced changes in carbon
fixation and growth to changes in carbohydrate concentration was developed.
This analytical framework suggests that the degree of root growth inhibition
by cold was the main factor in determining differences in carbohydrate content
between cultivars.
Characteristic patterns of chronic and dynamic photoinhibition of different functional groups in a Mediterranean ecosystem
Authors: Werner Christiane , Correia Otília , Beyschlag Wolfram
Published: September 2002

To analyse characteristic patterns of dynamic and chronic photoinhibition within a plant community, a new technique is proposed, which is based on the long- and short-term recovery time of maximum photochemical efficiency of PSII (F
v/F
m) after environmental stress. Chronic photoinhibition was determined as a sustainable decrease in predawn F
v/F
m, occurring during periods of prolonged stress, whereas dynamic photoinhibition was assessed from the fully reversible diurnal decline in F
v/F
m. Applied to a Mediterranean macchia ecosystem, this definition allowed the characterization of typical annual patterns of chronic and dynamic photoinhibition. Both types of photoinhibition were highest during summer drought. However, differences emerged among the ten dominant macchia species regarding their susceptibility to chronic photoinhibition during different seasons. Chronic and dynamic photoinhibition were dependent on leaf orientation. Semi-deciduous species avoided enhanced chronic photoinhibition through a reduction of excessive light interception by vertical foliage orientation during summer, whereas evergreen sclerophylls did not exhibit pronounced structural photoprotective mechanisms. Chronic and total photoinhibition were significantly correlated with predawn and midday water potentials, respectively, and a grouping of the macchia species into three functional groups is proposed according to this relationship.
Research note: Activity of granule-bound starch synthase is an important determinant of amylose content in rice endosperm
Authors: Umemoto Takayuki , Terashima Kazuo
Published: September 2002

Effects of temperature on amylose synthesis in rice endosperm were investigated using 13 cultivars known to differ in amylose contents in endosperm. Both amylose content and granule-bound starch synthase (GBSS) activity was increased when endosperms were developed under lower temperature in low- and medium-amylose cultivars, while this was not the case for high-amylose cultivars. Amylose content in high-amylose cultivars was stable under different temperature, with varying GBSS activity. A nearly linear correlation between GBSS activity and amylose content was observed as far as activity levels about 250 nmol min-1 g-1 DW. These results suggest that GBSS activity is an important determinant of amylose content in endosperm of low- and medium-amylose cultivars, while factors other than the enzyme activity limit amylose synthesis in the high-amylose cultivars.