bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow variability and the ecology of large rivers
Authors: Puckridge J. T. , Sheldon F. , Walker K. F. , Boulton A. J.
Published: August 2004

Ecological processes in large rivers are controlled by their flow variability.
However, it is difficult to find measures of hydrological variability that
characterize groups of rivers and can also be used to generate hypotheses
about their ecology. Multivariate analyses of the hydrographs of 52 rivers
worldwide revealed distinctive patterns of flow variability that were often
correlated with climate. For example, there were groups of rivers that
corresponded broadly with ‘tropical’ and ‘dryland’
climates. However, some rivers from continental climates occupy both extremes
of this range, illustrating the limitations of simple classification.
Individual rivers and groups of rivers may also have different hydrographic
‘signatures’, and attempts to combine measures of hydrological
variability into indices mask biologically significant information. This paper
identifies 11 relatively independent measures of hydrological variability that
help categorize river types and are each associated with aspects of fish
biology. Ways are suggested by which the Flood Pulse Concept can be expanded
to encompass hydrological variability and accommodate differences among groups
of rivers from different climatic regions. Such recognition of the complex
role of hydrological variability enhances the value of the concept for river
conservation, management and restoration.
Determination of the sources and distribution of sewage and pulp-fibre-derived pollution in the Derwent Estuary, Tasmania, using sterol biomarkers
Authors: Leeming Rhys , Nichols Peter D.
Published: August 2004

A geographical survey of sediments in the Derwent Estuary, near Hobart
(Tasmania), for sterol biomarkers of faecal pollution has established the
extent, distribution and severity of sewage pollution in the estuary. Analysis
of biomarkers for terrestrial plants has also determined the distribution of
pulp fibre discharged from a paper mill at Boyer in the upper estuary.
Contributions from other sources of extractable organics, such as hydrocarbons
and terrestrial plant and animal faecal matter from stormwater and creeks were
qualitatively evaluated. On the basis of the distribution of the faecal
biomarker coprostanol, the mid estuary and parts of the upper estuary (from
Newtown Bay to Taroona) are severely contaminated by sewage. Pollution from
pulp fibre is worst in the upper estuary and concentrations of pulp-fibre
biomarkers decrease downstream. Sediments of the lower estuary (south of
Taroona) have biomarker distributions more typical of open marine systems with
little evidence of pulp fibre. There is, however, evidence of low
concentrations of faecal pollution in the lower estuary.
Implications of sublethal predation, autotomy and regeneration: pigment bands on their spines can not be used to determine the ages of adult specimens of the corallivore Acanthaster planci
Authors: Souter David W. , Cameron Ann M. , Endean R.
Published: August 2004

Attempts to determine the ages of five adult specimens of
Acanthaster planci from the pigment bands on the aboral
spine ossicles were unsuccessful because there was little coincidence in the
number and arrangement of the bands on different spines obtained from the same
starfish. Hence, different spines often yielded markedly different putative
ages. Spines along the midline of an arm usually possessed more bands than did
those from the edge; the further from the central disc the location of an arm
spine, the fewer bands it carried; and the numbers of bands on spines from the
regenerating portions of arms were always significantly fewer than those on
spines from intact portions of arms. Spines from intact portions of different
arms from the same starfish yielded different putative ages, and the mean
putative age of arm spines was greater than, similar to, or less than that of
spines from the central disc. It was concluded that the putative age derived
from the banding patterns on the aboral spines of a starfish bears no
relationship to the actual age of the starfish but reflects its recent history
of spine autotomy, sublethal predation and regeneration.
Rates of retained and discarded catches from demersal fish trawling off the north-eastern United States
Authors: Kennelly S. J. , Drew S. C. , Gagnon C. D. Delano
Published: August 2004

The retained- and discarded-catch rates of fish, crustaceans and molluscs
caught by demersal fish trawlers were quantified in a large-scale observer
survey of fleets working off the north-eastern United States. The data
presented come from catches sampled from 7757 tows on 1010 fishing trips
during the four-year period from July 1990 to June 1994 and are summarized as
the weights retained and discarded (per hour of trawling) for many of the
important commercial and recreational species in the region. Problems with the
spatial and temporal design of the programme restricted statistical analyses
of the data and prevented summaries across all statistical areas and months.
However, separate summaries for individual areas (over all months) and
individual months (over all areas) identified several spatial and temporal
patterns in retained- and discarded-catch rates for individual species and
combinations of species. Noticeable increases and decreases in catch rates
during the four-year period provided information on the relative health of
certain stocks, and overall discard percentages indicated relative
selectivities of the trawling operations sampled.
Seasonal growth and reproduction of Enhalus acoroides (L.f.) Royle in a shallow bay in the western Gulf of Carpentaria, Australia
Authors: Kenyon R. A. , Conacher C. A. , Poiner I. R.
Published: August 2004

Seasonal growth of Enhalus acoroides, a tropical
seagrass, was measured at Groote Eylandt (14˚S,136˚30′E) by
the hole-punch method. Over the one-year study period, only the three youngest
leaves of each shoot grew faster than 10 mm leaf-1
day-1 . The second-youngest leaf grew the fastest, with
peak growth in January when water temperature was highest (33˚C). As a
proportion of total leaf length, the youngest leaf grew fastest
(3·5% day-1 ). Leaf growth was highest
(13·0–17·0 mm leaf -1 day
-1 ) from September to March, when the water temperature
exceeded 30˚C, but significantly less (about 6 mm leaf
-1 day -1 ) in June and July, when
water temperatures were 23–24˚C. Leaf growth was positively
correlated with water temperature and mean minimum water depth. Leaves were
longest in November and shortest in July and August. Leaf length was
positively correlated with water temperature, and leaves were longest when
their growth rate was high. The production of new shoots was greatest during
September–November, as water temperature increased. Shoots decayed and
flowers were produced throughout the year.
Thermocline climatology of the Arabian Sea - a review
Authors: Radhakrishnan K. G. , Mathew Basil , Kumar P. V. Hareesh , Kumar N. Mohan
Published: August 2004

The monthly evolution of the thermocline characteristics for the Arabian Sea
based on temperature profiles averaged over 2° × 2° grid cells
is presented. During the pre-monsoon period, the entire Arabian Sea is
characterized by a shallow thermocline (30–40 m) due to strong surface
heating. Upwelling in the coastal regions and downwelling in the central
Arabian Sea result in large variations in the thermocline topography during
the south-west monsoon. This pattern reverses during winter when the surface
currents reverse direction. The thermocline gradient is between 0.04°C
m-1 and 0.14°C m-1 . An
interesting result is the large variability in thermocline gradient (from
0.04°C m-1 near the coasts to 0.12°C
m-1 in the central Arabian Sea) during
July–September throughout the Arabian Sea. Weak gradients noticed in the
northern Arabian Sea are due to the interaction of two different warm-water
masses (the Arabian Sea and Persian Gulf water masses). The decrease in
gradient in the equatorial Arabian Sea from January to June is attributed to
the equatorial undercurrent which causes spreading of isotherms in the
thermocline.
Above- and below-ground biomass of mangroves in a sub-tropical estuary
Authors: Saintilan N.
Published: August 2004

Above- and below-ground biomass of five species of mangroves was estimated for
the Mary River, south-eastern Queensland. Below-ground : above-ground biomass
ratios of species in the upstream reaches
(Avicennia marina,
Aegiceras corniculatum and
Excoecaria agallocha) averaged <0.5, and those of
species in the saline conditions of the mouth
(Avicennia marina,
Rhizophora stylosa) ranged between 0.9 and 1.5. Within
the estuary mouth, above-ground biomass of
Avicennia marina and Ceriops tagal
decreased between frontal saline and upper-intertidal hypersaline
environments, and this was reflected in the below-ground : above-ground
biomass ratios, which increased to approximately 3.5 for both species.
Temperature stratification in the lower River Murray, Australia: implication for cyanobacterial bloom development
Authors: Bormans Myriam , Maier Holger , Burch Michael , Baker Peter
Published: August 2004

The relationship between temperature stratification of the water column, river
discharge and meteorological forcing was examined for the lower River Murray
by using a combination of field measurements and a simple mixing criterion.
Wind was found to be the dominant variable affecting the degree of temperature
stratification under low flow conditions typical of summer. The results of a
three-month intensive study were used in conjunction with six years of
historical data to determine the stratification potential of the lower River
Murray and its implication for water quality and cyanobacterial bloom
development. The physical characteristics and therefore stratification
behaviour of the water column in the river section studied are not conducive
to sustained blooms at any time of the year because of a combination of strong
winds and sufficiently high river discharges.
Association between the ghost shrimp Trypaea australiensis Dana 1852 (Crustacea : Decapoda) and a small deposit-feeding bivalve Mysella vitrea Laserson 1956 (Mollusca : Leptonidae)
Authors: Kerr Geoff , Corfield Jamie
Published: August 2004

The deep-burrowing species Trypaea australiensis and
Mysella vitrea inhabit intertidal sediments of the
Richmond River, northern New South Wales. Laboratory experiments indicated
that a facultative commensal association may exist between the two organisms,
because although the bivalves survived independently, their vertical
distribution in sediment was significantly different in the presence of
T. australiensis. Field observations indicated that
redox potential and bivalve abundance in sediment are weakly correlated.
However, the absence of strongly reducing conditions in the first metre of the
sediment, due to T. australiensis burrow irrigation, may
increase potential niche size for M. vitrea. Tank
observations revealed no aggregation of M vitrea around
the burrows. Feeding observations suggested that
M. vitrea can feed either by collecting particles off
the sediment surface or by interstitial pedal feeding; the latter feeding mode
would allow use of shrimp burrows for feeding.
T. australiensis alters organic carbon distribution in
the sediment profile, concentrations being significantly higher in the
lowermost regions where T. australiensis was present
than in controls. Thus, enrichment resulting from the activities of
T. australiensis may provide some reward for the
energetic cost to M. vitrea of burrowing deeply.
Pelagic elasmobranchs caught by longliners off southern Brazil during 1974 - 97: an overview
Authors: Amorim A. F. , Arfelli C. A. , Fagundes L.
Published: August 2004

From 1974 to 1997 elasmobranchs caught by longliners based in Santos City,
São Paulo State, Brazil, have been identified and the biology of some
of the species has been studied. The fleet has fished since 1968, and in 1996
comprised 16 boats operating in the area
17–35ºS,27–52ºW. Since 1977 yields of sharks have shown
an increasing trend, reaching ~60% of the longline total catch in 1993.
Blue shark (Prionace glauca) was the main species and
responsible for about 30% of the total catch of the Santos longliners.
The 33 shark and 2 ray species identified belonged to the following families
and genera: Alopiidae (Alopias), Carcharhinidae
(Carcharhinus, Galeocerdo,
Prionace) Hexanchidae
(Heptranchias, Hexanchus),
Lamnidae (Isurus, Lamna),
Megachasmidae (Megachasma), Odontaspididae
(Carcharias, Odontaspis),
Pseudocarchariidae (Pseudocarcharias), Rhincodontidae
(Rhincodon), Sphyrnidae (Sphyrna),
Squalidae (Squaliolus, Etmopterus,
Isistius), Dasyatidae (Dasyatis)
and Mobulidae (Mobula). Abundance, reproduction and
other biological aspects of some of the species are presented.
Resumo. Estudou-se os elasmobrânquios capturados
pelos atuneiros sediados em Santos. Esta frota, que utiliza o espinhel como
arte de pesca, vem pescando desde 1968 no sudeste e sul do Brasil, sendo que
em 1996 haviam 16 barcos, operando na área 17-35ºS,27-52ºW.
Desde 1977 a produção de tubarões apresentou
tendência crescente, atingindo 60% do total da captura em 1993. O
cação-azul (Prionace glauca) foi o
principal responsável pelo aumento das capturas de tubarões,
representando cerca de 30 % do total da captura dessa frota.
Identificou-se, no período de 1974 a 1997, 33 espécies de
tubarão e duas de raia, pertencentes às seguintes
famílias e gêneros: Alopiidae (Alopias),
Carcharhinidae (Carcharhinus,
Galeocerdo, Prionace) Hexanchidae
(Heptranchias, Hexanchus),
Lamnidae (Isurus, Lamna),
Megachasmidae (Megachasma), Odontaspididae
(Carcharias, Odontaspis),
Pseudocarchariidae (Pseudocarcharias), Rhincodontidae
(Rhincodon), Sphyrnidae (Sphyrna),
Squalidae (Squaliolus, Etmopterus,
Isistius), Dasyatidae (Dasyatis)
and Mobulidae (Mobula). Apresentam-se análises da
pesca, da reprodução e de outros aspectos biológicos de
algumas espécies.
Shark fisheries in Argentina
Authors: Chiaramonte Gustavo E.
Published: August 2004

In the Argentine Sea there are about 35 species of sharks. Three species are
subjected to directed fishing: the smoothhound
Mustelus schmitti, the school shark
Galeorhinus galeus and the copper shark
Carcharhinus brachyurus. Other species of elasmobranchs
with commercial importance are the angel shark Squatina
spp. and several species of skates and rays. The rise in chondrichthyan
declared landings registered from 1988 to 1996 is due to the increase in
landings of smoothhound and rays. The most important directed shark fishery in
the South-West Atlantic is the Necochea gill-net fishery for school shark,
which is carried out by the coastal fleet; details are given of the ships and
the gill-nets used in this area. The length frequencies of the catches by
gill-nets are presented for the school shark; fishing effort (length (km) of
net in the water per ship per day) and CPUE (number of sharks per fishing
effort) were found not to be good indicators of population trends in the
school shark fishery.
Resumen. En el Mar Argentino se han registrado 35
especies de tiburones. Tres de estas especies están sometidas a una
pesca dirigida; el gatuzo, Mustelus schmitti, el
cazón, tiburón vitamínico o trompa de cristal,
Galeorhinus galeus y la bacota,
Carcharhinus brachyurus. Otras especies de
elasmobranquios de importancia comercial son el pez ángel
Squatina spp. y algunas especies de rayas. El incremento
en los desembarcos de condríctios declarados a las autoridades
pesqueras entre 1988 y 1996 es debido principalmente al incremento del
desembarco de gatuzo y rayas. La pesquería dirigida a tiburón
más importante en el Atlántico Sudoccidental es la
pesquería costera de enmalle de Necochea para el cazón. Se
describen el largo de las embarcaciones y las redes utilizadas en el
área (la medida de malla, el calado y la operación del arte de
pesca). Se presenta la frecuencia del largo total de las capturas de
cazón en redes de enmalle. Se halló para la pesquería del
cazón que el esfuerzo pesquero (estimado como km de red en el agua por
embarcación por día) y la CPUE (estimada como
tiburones/esfuerzo de pesca) no son buenos indicadores de la tendencia en
la abundancia poblacional.
Estimating spatial variability in developing assemblages of epibiota on subtidal hard substrata
Authors: Glasby T. M.
Published: August 2004

A nested hierarchical sampling design was used to estimate the scales of
natural variability in developing assemblages of subtidal epibiota on rocky
reefs. The appropriate spatial scales were needed for sampling to test for
environmental impact in this habitat. Sandstone settlement plates were used to
mimic the natural substratum. They were designed and deployed in such a way
that the effects of any supporting structures were minimized. Differences in
recruitment of epibiota were found at all of the spatial scales examined (10s,
100s and 1000s of metres). When differences were found at the smallest spatial
scale, they were generally still detected at the two larger scales. The
results highlighted the need for adequate small- and large-scale spatial
replication for studies of environmental impact.
Selectivity for barramundi (Lates calcarifer) in the Fly River, Papua New Guinea: implications for managing gill-net fisheries on protandrous fishes
Authors: Milton David A. , Die David , Tenakanai Charles , Swales Stephen
Published: August 2004

Fishery-independent catch data from monofilament gill-nets (3.8–15.2 cm
stretched mesh) were used to estimate the selectivity of each mesh size for
the protandrous species barramundi, Lates calcarifer, in
the Fly River region of Western Province, Papua New Guinea. These results were
used with a range of life-history parameters to simulate the effects of
fishing with meshes of three sizes common to the local fisheries (8.9, 10.2
and 15.2 cm) on (1) number of sexually mature females
surviving to maximum age, (2) their total egg production
and (3) number of mature males surviving to fertilize
these eggs. Catches in most mesh sizes approximated a normal selection curve,
and the mean and standard deviation of each curve were linearly related to
mesh size. Juvenile and immature barramundi (<38 cm total length) were
fully selected by the common mesh sizes used in the coastal subsistence and
artisanal fisheries (7.6–10.2 cm) but these mesh sizes caught few
sexually mature females. Population simulations showed that the number of
females surviving to maximum age and their total egg production increased as
mesh size was reduced. Reducing the mesh size to increase adult female
escapement may be a better management strategy than increasing mesh sizes to
improve recruitment.
Seasonal Changes in Stable Carbon Isotope Ratios within Annual Rings of Pinus radiata Reflect Environmental Regulation of Growth Processes
Authors: Walcroft A. S. , Silvester W. B. , Whitehead D. , Kelliher F. M.
Published: August 2004

Seasonal cycles in stable carbon isotope composition
(δ13C) were measured within annual rings of
Pinus radiata D. Don from trees in two plantation sites
which differ markedly in annual water balance. The amplitudes of seasonal
δ13C variation at the wet and dry sites were
1–2 and 4 respectively. Mean δ13C values
from the wet site were 3 more 13C depleted than those
from the dry site implying lower water-use efficiency (carbon assimilation per
unit transpiration). A process-based, leaf-level model of stomatal conductance
and CO2 assimilation was combined with a water balance
model to estimate the average daily intercellular CO2
concentration (ci). Over two
growing seasons at each site there was generally good agreement between mean
canopy-level ci derived from the
tree-ring δ13C data and modelled leaf-level
ci levels. Further, the ratio of
annual CO2 assimilation to transpiration estimated by
the model for each site correlated with the differences in water-use
efficiency between the sites. Carbon isotope discrimination of leaves in the
canopy was thus reflected directly in the stem wood, and its dynamic variation
within a site, as well as between sites, was driven principally by the
interaction of seasonally changing micrometeorological variables and soil
water availability.
Endogenous Biosynthetic Precursors of (+)-Abscisic Acid. V. Inhibition by Tungstate and its Removal by Cinchonine shows that Xanthoxal is Oxidised by a Molybdo-Aldehyde Oxidase
Authors: Lee H-S. , Milborrow B. V.
Published: August 2004

A cell-free preparation from avocado fruit incorporates
[14C]mevalonate into ABA. A number of specific
inhibitors have been used to probe the system and tungstate ions at 100
µM reduce the 14C in ABA by 80% The
inhibitory effect was overcome by the alkaloid cinchonine (2000 µM)
which binds tungstate strongly and selectively.
More 14C from mevalonate was present in xanthoxal (4600
dpm), less in ABA (340 dpm) when the cell-free system was inhibited by
tungstate (100 µM) than in controls (1810 dpm in xanthoxal, 1200 dpm in
ABA), which shows that xanthoxal is the substrate for the aldehyde oxidase.
Xanthoxic acid, therefore, is the next intermediate and AB-aldehyde is not a
normal precursor.
The potential for using the tungstate/cinchonine reaction to probe other
biosynthetic pathways which require a molybdate ion is discussed.
An Efficient Transformation System for the Australian Rice Cultivar, Jarrah
Authors: Abedinia M. , Henry R. J. , Blakeney A. B. , Lewin L.
Published: August 2004

A rapid and efficient transformation system for the generation of large
numbers of transformed, fertile, transgenic rice
(Oryza sativa L.) plants of the Australian rice
cultivar, Jarrah, is described. Embryogenic callus pieces derived from mature
seeds were bombarded with gold particles coated with DNA. Two plasmids were
used, one containing a gene encoding hygromycin phosphotransferase
(hph, conferring hygromycin resistance) as a selectable
marker and the other containing uidA
(gus) as a reporter gene. The calli were selected for
their resistance to hygromycin. DNA uptake, integration and expression of the
hph and gus gene in selected rice
were investigated by various PCR methods and dot blot and Southern analysis of
genomic DNA extracted from transformed rice plants. On average one
independently transformed hygromycin resistant plant was recovered from every
2.4 pieces of callus bombarded. Selection with Biolaphos using the
Bar gene as selectable marker was not successful in this
system.
Responses of Rainforest Understorey Plants to Excess Light during Sunflecks
Authors: Watling Jenny R. , Robinson Sharon A. , Woodrow Ian E. , Osmond C. Barry
Published: August 2004

Responses of Alocasia macrorrhiza (L.) G. Don,
Castanospora alphandii (F. Muell.) F. Muell. and
Alpinia hylandii R. Smith, growing in a tropical
rainforest understorey, to excess light during sunflecks were investigated
using chlorophyll fluorescence techniques and by analysing xanthophyll cycle
activity. A fourth species, the
pioneerOmalanthus novo-guineensis (Warb.) Schum.,
growing in a small gap, was also studied. In all three understorey species
there were large and rapid decreases in the proportion of open Photosystem II
(PSII) centres, as indicated by
qP, on illumination with
saturating light and a concurrent increase in non-photochemical quenching.
qP remained low (< 0.4)
throughout the period of illumination (~15 min), although it did increase
gradually, probably reflecting photosynthetic induction. Sustained declines
(up to 120 min) in quantum yield, indicated by
Fv/Fm,
occurred in all three understorey species following exposure to saturating
Photon flux density (PFD) during sunflecks. When ?PSII was monitored
during sunflecks it was found to be very sensitive to changes in PFD,
declining rapidly with even modest rises in the latter. There was rapid and
continuing net conversion of violaxanthin (V) to antheraxanthin plus
zeaxanthin (A+Z) on exposure of A. macrorrhiza and
C. alphandii to saturating sunflecks. On returning to
low light A. macrorrhiza retained its high levels of
A+Z for up to 60 min, while C. alphandii rapidly
converted back to V. O. novo- guineensis responded to
high light by changing its leaf angle to reduce interception and showed no
indication of photoinhibition during or after exposure.
Enhanced Root Production as a Feed-forward Response to Soil Water Deficit in Field-grown Tomatoes
Authors: Reid J.B. , Renquist A.R.
Published: August 2004

Much research on the role of roots as ‘sensors’ of soil water
deficits (SWD) has been with plants growing in small volumes of soil. We
examined adaptive responses to SWD in processing tomatoes
(Lycopersicon esculentum Mill.) growing in the field.
The cv. Cannery Row was grown next to a rhizotron and trickle irrigated daily,
except when water was withheld for 7 or 14 days during flowering in two
deficit treatments. Rainfall was excluded.
Within 7 days of withholding irrigation, there was a substantial increase in
root production, particularly in the subsoil. However, predawn and midday leaf
water potentials did not differ between non-irrigated and control treatments
until around day 9. Even by day 14 the SWD had not affected stomatal
conductances, evapotranspiration, or plant dry mass. A rapid increase in root
death rate followed the re- irrigation of each deficit treatment. New root
production in the non-irrigated plots appeared sufficient to maintain an
adequate supply of water to the shoots. If so, this could be an even more
effective means of stress avoidance than reducing leaf and stem expansion
rates. Our results appear to be the first practical demonstration that root
systems may play such a feed-forward role.
Ultrastructural Changes in Root Cap Cells of Two Australian Native Grass Species Following Exposure to Aluminium
Authors: Crawford Simon A. , Wilkens Sabine
Published: August 2004

Transmission electron microscopy was used to investigate ultrastructural
changes in root cap cells of two aluminium-tolerant native grass species,
Danthonia linkii Kunth and
Microlaena stipoides (Labill.) R.Br., following exposure
to Al. Quantitative differences in root cap cells and organelles in response
to 0–10 ppm aluminium were determined using image analysis of electron
micrographs. Changes to the size of root cap cells due to exposure to Al were
similar in the two species with a low Al concentration (1–2 ppm)
resulting in larger cells, while higher Al levels (5–10 ppm) reduced
cell size. In peripheral cap cells of the more Al-tolerant
M. stipoides, the size of secretory vesicles was not
affected by exposure to Al, while in peripheral cap cells of the less
Al-tolerant D. linkii, exposure to Al resulted in
significantly smaller secretory vesicles being produced. Central root cap
cells from control plants of M. stipoides contained
90% more dictyosomes and had 50% larger amyloplasts than
D. linkii. Measurement of mucilage droplets showed that
roots of M. stipoides produced much more mucilage than
D. linkii. Exposure of roots of
M. stipoides to Al in the range 2–10 ppm had no
effect on the size of mucilage droplets produced. The possible role of
mucilage production in aluminium tolerance is discussed.
Stomatal Conductance and ABA Concentration in the Xylem Sap of Barley Lines of Contrasting Genetic Origins
Authors: Borel Ch. , Simonneau Th. , This D. , Tardieu F.
Published: August 2004

We investigated the controls of ABA concentration in the xylem sap and of
stomatal conductance in five barley (Hordeum vulgare L.)
lines of contrasting origins (Syrian or French), genetic backgrounds and
previously field-evaluated drought resistances. Controlled water deficits were
applied to young plants in a series of experiments in the greenhouse with
contrasting evaporative demands. There was a unique relationship between soil
water status and the concentration of ABA in the xylem sap measured at the end
of the night. This relationship applied to all experiments for a given line,
and was common between lines. Concentrations measured in the sap collected by
pressurising leaves were similar to those in the sap of pressurised roots.
Stomatal conductance was related to the concentration of ABA in the sap, with
relationships which were common for all experiments within each line. Response
curves of gs to concentration of
ABA in the sap differed among two groups of lines which slightly differed in
life cycle duration. Apparent stomatal sensitivity to ABAwas lower in earliest
anthesing lines. Both groups comprised lines of either Syrian or French
origins, and either ‘drought tolerant’ or ‘drought
susceptible’ lines. We conclude that stomatal control had a low genetic
variability in the studied range of lines, in spite of the large genetic
differences between lines.
Relationship between Starch Accumulation and Activities of the Related Enzymes in the Leaf Sheath as a Temporary Sink Organ in Rice (Oryza sativa)
Authors: Watanabe Yoshito , Nakamura Yasunori , Ishii Ryuichi
Published: August 2004

The starch stored temporarily in the leaf sheath of rice plants is
translocated to the grain, contributing to the grain yield. In this paper, the
relationship between starch accumulation and the activities of enzymes
involved in the starch biosynthetic pathway in the leaf sheaths of rice plants
was examined to elucidate the regulation mechanism of starch accumulation in
the temporary sink organ. When the starch content was compared between
different leaf sheath positions on the main stem, the 14th leaf sheath counted
from the bottom, which elongated just before anthesis, showed about a
four-fold higher value than the 10th leaf sheath. Among the enzymes involved
in carbohydrate metabolism, the activity of starch branching enzyme (BE,
EC2.4.1.18) was greatly higher in the 14th leaf sheath than in the 10th leaf
sheath, while that of ADPglucose pyrophosphorylase (EC2.7.7.27) was similar
between the two leaf sheaths. The starch content increased rapidly in the
period around anthesis in the 12th and 14th leaf sheaths, but did not in the
10th and 11th leaf sheath. In the higher leaf sheath position, the activity of
BE changed with noticeably similar trend to the starch content. Soluble starch
synthase (SSS, EC2.4.1.21), granule-bound starch synthase (GBSS, EC2.4.1.21)
and plastidial fructose- 1,6-bisphosphatase (FBPase, EC3.1.3.11) were also
significantly correlated with the starch content. These results suggest that
BE is involved in regulation of starch metabolism, possibly in collaboration
with other enzymes such as SSS, GBSS and plastidial FBPase in temporary sink
organs like the leaf sheath.
The Short-term Growth Stimulation Induced by External Supply of IAA in Internodes of Intact Pea Seedlings
Authors: Haga K. , Iino M.
Published: August 2004

Indole-3-acetic acid (IAA) mixed with lanolin was applied to a defined region
of the top elongating internode (third internode, initially 21–24 mm
long) of intact pea (Pisum sativum L. cv. Alaska)
seedlings, and the effects of applied IAA on growth of internode zones were
investigated. Experiments were conducted with plants grown in red light (R),
with supplementary use of plants grown in white light (W). Growth of the
internode was first characterised without IAA application. Internode zones
elongated at an identical and constant rate per unit length until each zone
sharply ceased elongation at a certain distance from the apex. The elongation
rate was similar even between R-grown and W-grown plants, the major difference
being an earlier cessation of zone elongation in W-grown plants. Following IAA
application, the growth rate of zones increased (maximally about two times)
but, after a few hours, it declined to the pre-stimulation rate. This
short-term growth stimulation (SGS) was observed when IAA was applied directly
to the zone monitored for growth and when IAA was applied to an apically
separated region. It was demonstrated that SGS was caused not because radial
growth was enhanced in place of elongation, nor because energy became
limiting. Based on the kinetic differences observed by applying IAA to
different regions of the internode and also on the data obtained by applying
IAA again at the post-stimulation phase, two independent regulatory elements
could be resolved for SGS: (1) reduction of the tissue responsiveness for IAA,
and (2) reduction of IAA supply to the target tissue. These regulations are
considered to operate in response to increases in the tissue content of IAA.
Analysis of Bundle Sheath Conductance and C4 Photosynthesis using a PEP-Carboxylase Inhibitor
Authors: Brown R. Harold
Published: August 2004

High [CO2] in bundle sheath cells (BSC) allows
high rates of CO2 assimilation (A)
and minimises photorespiration in C4 leaves. The
[CO2] in BSC is likely to be low when PEPcase
is inhibited by 3,3-dichloro-2-dihydroxyphosphinoylmethyl-2-propenoate (DCDP),
but Rubisco is still functional. The degree of C4
photosynthesis can be assessed by decreased A and the
conductance of BSC walls by the slope of A versus
[CO2] during application of DCDP. Inhibition
of A by 4.0 mM DCDP was 87-100% in
C4 species and was overcome by increasing
[CO2] to 2.0-2.5 kPa. In
C3 -C4 species in
Moricandia, Panicum and
Neurachne, A and its inhibition by
O2 were unchanged by DCDP, but in
C3 -C4 and
C4 -like species and interspecific hybrids of
Flaveria, A was reduced and its inhibition by
O2 was increased. Conductance of BSC walls was 1.13,
1.96, and 2.35 mmol m-2 s-1 in the
C4 species, Sorghum bicolor (L.)
Moench, Panicum miliaceum L., and
Panicum maximum Jacq., respectively. There was no effect
of O2 on A in DCDP-treated
C4 leaves, apparently because the low conductance of BSC
walls masks the influence of O2 on
CO2 exchange in these cells.
Control of Photosynthesis in Amaranthus edulis Mutants with Reduced Amounts of PEP Carboxylase
Authors: Dever Louisa V. , Bailey Karen J. , Leegood Richard C. , Lea Peter J.
Published: August 2004

Mutants of the NAD-ME plant have been created using sodium azide. These
contain reduced activities of PEP carboxylase ranging from 5 to 100% of
wild-type. Those with greater than 50% of the wild-type PEPC content
showed a lower maximum rate of photosynthesis and reduced carboxylation
efficiency compared to the wild-type plants. The PEPC from these heterozygotes
was less sensitive to malate inhibition than the PEPC of the wild-type plants
and also had an increased phosphorylation state.
Mutants containing 45 and 49% of wild-type PEPC exhibited a greater
Amax than was observed for the 55, 66 and 70%
mutants. We postulate that there is a compensatory mechanism that activates
PEPC when the PEPC protein is less than 55% of the wild-type.
Control coefficients were measured for PEP carboxylase from wild-type and
heterozygous (55%) plants. Results suggest that activation of PEPC by
phosphorylation and metabolites may be more an ‘on-off’ switch
than a means of fine adjustment of PEPC activity in response to varying
factors such as PEPC content, CO2 or temperature
changes.
Characterisation of Two cDNAs Encoding Carbonic Anhydrase in Maize Leaves
Authors: Burnell James N. , Ludwig Martha
Published: August 2004

Two distinct cDNAs encoding carbonic anhydrase (CA) were isolated from a maize
λgt 11 library. One of these cDNAs, CA1, which consists of a
5´-leader sequence, three repeat sequences and a 3´-non-coding
region, is predicted to encode an open reading frame for a polypeptide of 71.3
kDa. The other cDNA, CA2, which has a 5´-leader sequence containing a
276 bp insert compared to CA1, two repeat sequences and a 3´-non-coding
region, is predicted to encode an open reading frame for a polypeptide of 59.2
kDa. Nucleotide sequence alignment analysis indicates that the two repeat
sequences of CA2 are homologous with repeat sequences 1 and 3 of CA1,
respectively.
Four protein bands, with apparent molecular masses of 52, 47, 28 and 27 kDa,
were evident in western blot analyses of crude extracts of maize leaf tissue
prepared in the absence of Triton X-100 and two protein bands, with apparent
molecular masses of 27 and 28 kDa, were detected in western blots of crude
extracts prepared in the presence of Triton X-100. These results indicate
either that both CA1 and CA2 mRNAs are only partially translated, that the CA1
and CA2 proteins are processed, or a combination of both of these
alternatives. Two maize leaf CA1 and CA2 mRNAs detected on northern blots are
longer than any other plant CA mRNA reported to date. Possible roles for the
two CA isozymes in maize leaves are discussed.
Elevated atmospheric CO2 concentrations increase wheat root phosphatase activity when growth is limited by phosphorus
Authors: Barrett Damian J. , Richardson Alan E. , Gifford Roger M.
Published: August 2004

Wheat seedlings were grown in solution culture under adequate and limited
phosphorus treatments at current ambient and elevated (approximately 2×
ambient) CO2 concentrations. Acid phosphomonoesterase
(‘phosphatase’) activity of root segments was measured using
p-nitrophenyl phosphate as substrate. When plant growth
was P-limited, elevated CO2 concentrations increased
phosphatase activity more than at ambient CO2. This
result (1) was evident when expressed on a unit root dry weight or root length
basis, indicating that increased root enzyme activity was unlikely to be
associated with CO2-induced changes in root morphology;
(2) occurred when plants were grown aseptically, indicating that the increase
in phosphatase activity originated from root cells rather than root-
associated microorganisms; (3) was associated with shoot P concentrations
below 0.18%; (4) occurred only when wheat roots were grown under P
deficiency but not when a transient P deficiency was imposed; and (5) suggest
that a previously reported increase in phosphatase activity at elevated
CO2 by an Australian native pasture grass (Gifford,
Lutze and Barrett 1996; Plant and Soil 187,
369–387) was also a root mediated response. The observed increase in
phosphatase activity by plant roots at elevated CO2, if
confirmed for a wide range of field pasture and crop species, is one factor
which may increase mineralisation of soil organic P as the anthropogenic
increase of atmospheric CO2 concentrations continues.
But, whether a concomitant increase in plant uptake of P occurs will depend on
the relative influence of root and microbial phosphatases, and soil
geochemistry in determining the rate of mineralisation of soil organic P for
any given soil.
Inhibition of Rust-induced Hypersensitive Response in Flax Cells by the Microtubule Inhibitor Oryzalin
Authors: Kobayashi Issei , Kobayashi Yuhko , Hardham Adrienne R.
Published: August 2004

Interactions between the flax rust fungus
Melampsora lini and flax
Linum usitatissimum L. are governed by a gene-for-gene
relationship which determines pathogen virulence or avirulence and host
resistance or susceptibility. The present study demonstrates differential
sensitivity of M. lini and flax to the microtubule
depolymerising drug, oryzalin, such that microtubule depolymerisation in flax
cells but not in fungal cells could be obtained. Normally, in an incompatible
interaction, a rapid hypersensitive response about 24 h after inoculation
inhibits fungal development and invasion. However, in an incompatible
interaction in the presence of oryzalin, the occurrence of hypersensitive cell
death was delayed and its frequency reduced. This allowed a normally avirulent
race of M. lini to form haustoria in living host
mesophyll cells at a rate and efficiency similar to that achieved by a
virulent race in a compatible interaction during the first 36 h after
inoculation. After that time, the incidence of hypersensitive cell death
increased and further development of the pathogen was arrested. The results
indicate that microtubules play a role in effecting rapid and efficient
hypersensitive response in the race–cultivar specific interaction
between flax and the flax rust fungus.
Metabolic Changes and Susceptibility to Chilling Stress in Capsicum annuum Plants Grown at Suboptimal Temperature
Authors: Mercado José A. , Reid Michael S. , Valpuesta Victoriano , Quesada Miguel A.
Published: August 2004

Pepper plants (Capsicum annuum L.; hybrid Latino) were
grown at temperature regimes of 29/20 and 25/14 (˚C,
day/night) and the variables previously related to the cold acclimation
process in temperate plants were studied. After 60 days of treatment, plants
cultivated at the low temperature regime showed a 50–70%
reduction in shoot length, leaf number and shoot dry weight in comparison with
the high temperature regime. Root dry weight was not different between the two
sets of plants, and the plants grown in the cold regime showed an increased
number of axillary shoots. Analysis of the leaves at four different positions
in the canopy (below the first bifurcation of the plant and in the first,
second and third bifurcation) showed that chlorophyll and soluble protein
content decreased with plant age at both temperature treatments, but absolute
values were higher in the leaves of plants grown at low temperature,
especially in the two upper leaves. The difference in the protein content
could be explained by different leaf content of soluble Rubisco enzyme. Total
nitrogen content was slightly higher in the leaves of plants grown at low
temperature, but the percentage of the nitrate form was lower in this
condition. In relation to carbohydrates, the sucrose content was lower in the
leaves of the cold regime plants, except in the youngest one, whereas the
starch was higher in the leaves of these plants, specially in the two upper
leaves. Finally, plants grown at the lower night temperature showed an
improved chilling resistance when exposed for 4 nights at 6˚C, as
estimated by visual rating and measurement of leaf electrolyte leakage. The
level of cold tolerance observed was similar to the level obtained in plants
grown at optimal temperature treated with paclobutrazol, a plant growth
regulator that ameliorates chilling stress symptoms. Differences in carbon and
nitrogen metabolism are discussed in relation to the cold acclimation process
of pepper plants.
A comparison of CO2 and O2 exchange patterns and the relationship with chlorophyll fluorescence during photosynthesis in C3 and CAM plants
Authors: Maxwell Kate , Badger Murray R. , Osmond C. Barry
Published: August 2004

Patterns of CO2 and O2 exchange
coupled to chlorophyll fluorescence were examined in the CAM plants
Kalanchoe daigremontiana Hamet et Perr. and
Hoya carnosa (L.f.) R.Br., and compared with the
C3 species Sonchus oleraceus L.
Patterns of CO2 assimilation during phase IV of CAM were
as predicted for Rubisco-mediated atmospheric CO2 uptake
in both CAM plants. The high energetic demand during decarboxylation (phase
III) was reflected in a high, CO2-insensitive rate of
gross O2 evolution. Uptake of external
CO2 was significant during phase III and was not
saturated at 1.5% CO2. Gross oxygen uptake in the
light was CO2 sensitive in
H. carnosa during phases III and IV, which suggests
Rubisco oxygenase activity. Oxygen consumption comprised around 33%
linear electron transport in K. daigremontiana during
phase III (7.5 µmol O2 m-2
s-1 at saturating CO2), but we
cannot yet distinguish whether this involves the Mehler reaction or TCA cycle
and oxidative phosphorylation during deacidification.
CO2 assimilation was saturated at 0.2%
CO2 when the epidermis was removed in
K. daigremontiana, suggesting a large stomatal and
mesophyll resistance to CO2 diffusion. A linear
relationship was obtained between the quantum yield of gross
O2 evolution and the quantum efficiency of PSII.
Light- and dark-grown Potamogeton pectinatus, an aquatic macrophyte, make no ethylene (ethene) but retain responsiveness to the gas
Authors: Summers Jacky E. , Jackson Michael B.
Published: August 2004

Plants of Potamogeton pectinatus L., growing rapidly
from small tubers in the dark or from 12-week-old light-grown plants,
contained high concentrations of the ethylene precursor 1-amino-cyclopropane-
1-carboxylic acid (ACC) (4.8 – 25.6 nmol g-1 fresh
weight). However, ethylene (ethene) production was either completely absent or
too small to raise concentrations significantly above background when measured
by flame ionization gas chromatography sensitive to <0.04 µmol
m-3. Seedlings of pea
(Pisum sativum L.) of similar size produced ethylene in
readily detectable amounts although concentrations of endogenous ACC
concentrations were much smaller than in P. pectinatus.
Large amounts of exogenous ACC (10 mM) supplied for 4 h or 15 h failed to
induce ethylene production in dark-grown P. pectinatus
but raised it marginally above background levels in light-grown shoots. In
contrast, a substantial effect was seen in pea shoots. When 25 mM ACC was
supplied, a small amount of ethylene was released by dark-grown
P. pectinatus but the rate was less than 0.5% of
that measured from pea plants treated similarly. An absence of ACC oxidase
enzyme activity in extracts of P. pectinatus showed that
the last step in the ethylene biosynthetic pathway is constitutively arrested
in mature plants grown in the light and in young plants regenerating from
tubers in the dark. Despite an inherent inability to synthesise ethylene,
P. pectinatus remained responsive to applied ethylene.
Leaf extension and adventitious rooting from stem nodes were promoted strongly
by 0.41 mmol m-3 ethylene, whereas applications of ACC
had no effect on growth or development.
Soil erosion and nutrient loss. III.¤ Changes in the enrichment ratio of total nitrogen and organic carbon under rainfall detachment and entrainment
Authors: Palis R. G. , Ghandiri H. , Rose C. W. , Saffigna P. G.
Published: August 2004

Experiments to investigate the enrichment mechanisms of organic carbon,
nitrogen, and fine particles in eroded sediment were carried out on 2
contrasting soils under simulated rainfall with and without runon. Sediment
samples for concentration measurement were collected at different sampling
intervals and fractionated into various size fractions using sets of sieves.
The fractionated sediment samples and original (uneroded samples) were
analysed for total nitrogen and organic carbon to obtain the enrichment ratio
(ER) for both elements.
For both soils, sediment concentration, total nitrogen and organic carbon
(ER), and concentration ratios of
nitrogen and organic carbon changed considerably under the different dominant
erosion mechanisms in the experiments. For experiments on both 0·1 and
3% slopes, sediment concentrations of the smaller fractions (<53 and
53–500 µm) were higher than those of the original soil and
remained so throughout the duration of the experiment. At the higher slope
(3%) and thus lower water depths, a process described as raindrop
peeling apparently was more pronounced, since stable soil aggregates were
exposed to raindrop impact. The concentration of the smaller size fraction
increases with time resulting in an increase in total nitrogen and organic
carbon relative to the original soil. This leads to an
ER greater than unity in the
eroded sediment.
Rilling was observed in experiments with both rainfall and runon. During the
relatively short period prior to the establishment of active rilling, the
proportion of larger aggregates increased with time. After this proportion had
stabilised, the concentrations of total nitrogen and organic carbon were
similar to those in the original soil. Thus,
ER was close to unity, sometimes
being slightly below unity.
The presence of significant depths of water greatly influenced both the
breakdown of soil aggregates and the size or settling velocity distribution of
the eroded sediment. In these circumstances, the size-selected process of
deposition can lead to enrichment. With a negligible depth of water on the
soil surface, raindrop peeling was the dominant mechanism, producing fine
particles richer in organic carbon and total nitrogen than the original soil.
As depth of water increases, the effect of the highly varied settling velocity
particles on the size characteristics of eroded sediment becomes more evident,
and the effect of raindrop stripping diminishes. With a thin layer of water on
its surface, both of these mechanisms seem to be operative.