bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and temporal variations in abundance and distribution of juvenile and adult jackass morwong, Nemadactylus macropterus, in south-eastern Tasmania
Authors: Jordan Alan R.
Published: September 2002

Depth-stratified random demersal trawl surveys of the shelf of southern and
eastern Tasmania from summer 1993 to summer 1995 showed seasonal variations in
abundance of N. macropterus in all depth strata,
although the trend varied between years, with abundance peaking in summer 1993
and winter 1994. This variation is attributed to the seasonal movement of fish
from south-eastern Tasmanian shelf waters, although some seasonal change in
size composition is also evident. Catch rates were highest on the outer shelf
and lowest on the inner shelf, reflecting the distinct size-structuring, with
juveniles concentrated on the inner and mid shelf and mature fish on the outer
shelf. Size compositions differed among shelf regions, with few mature fish on
the mid shelf of Storm Bay compared with the same stratum on the east coast,
indicating that the bay is primarily a nursery area for the species.
Settlement from the pelagic post-larval phase occurred in spring and early
summer at 7–9 cm, with evidence of movement between inner-and mid-shelf
strata by autumn. Abundance of 0+ fish was highest in 1993 and 1994 and a
considerable decrease in the abundance in both regions in 1995. The influences
of local hydrography and the large size at settlement are discussed.
Estimating gill-net selectivity for five species caught in the South East Fishery, Australia
Authors: Cui Gurong , Bax Nicholas J. , Punt André E. , Knuckey Ian A.
Published: September 2002

A formal approach to estimating selectivity patterns that allows for
variability additional to Poisson sampling variability is outlined. This
approach, which involves assuming that the catch of fish by a particular size
of gill-net in a given size-class is distributed according to a negative
binomial distribution, is applied to data for five of the species caught by
experimental gill-nets in Australia’s South East Fishery. The data for
two of these species (blue warehou and dogfish) are not compatible with the
conventional assumption that the size of fish corresponding to maximum
selectivity is linearly proportional to mesh size. Selectivity and population
size-structure are found to depend on depth and habitat type for some of the
species. It is necessary therefore to target future experiments to depth
zones/habitat types in which the bulk of the catch is taken to estimate
selectivity patterns for use in stock assessments.
Indicators of the effectiveness of quota markets: the South East Trawl Fishery of Australia
Authors: Connor Robin , Alden Dave
Published: September 2002

This paper presents some results of an investigation into potential indicators
for the assessment of markets for individual transferable fishing quota where
price data do not exist. The economic logic for implementing such markets and
how they are expected to work is used as a basis for asking questions about
how well they are performing, and what might comprise evidence of problems.
Given data on quota ownership, transfer and leasing, and associated catches,
but no quota price data, indicators are suggested for monitoring and analysing
market activity. These are applied to data from the Australian South East
Trawl Fishery. Results are discussed in terms of the utility of the methods
and the implications for management policy for the fishery.
Trawl operations in the South East Fishery, Australia: spatial distribution and intensity
Authors: Larcombe James W. P. , McLoughlin Kevin J. , Tilzey Richard D. J.
Published: September 2002

Trawl areas and intensities were mapped at coarse (22 km 1986–99)and
fine (1 km 1995–99)scales, and statistics reported by area and depth
stratum. Total effort in hours was relatively stable to 1992, then increased
substantially to 1999. The total distance trawled from fine-scale analysis
showed a similar trend for the 1995–99 period. Coarse-scale analysis
from 1986–99 indicated effort increases in north-east Bass Strait in
particular, and also off western Tasmania and west of Bass Strait. There was
little change in the total area of the fishery from 1995 to 1999, but grid
cells on the periphery showed considerable interannual variation in the
presence or absence of fishing. Increased or redistributed effort tended to
further concentrate in the relatively small high-effort areas, rather than
increasing equally across the grounds, or spreading to new grounds. In the
total management area, a small proportion of the 1 km grids was fished.
However, in 200–1000 m depth strata, ≥50%of the grids were
fished with some intensity. The consequences and compromises of spatial scale
are discussed in terms of data quality, the use of trawl effort as a surrogate
for marine disturbance, and the interpretation of catch rates.
Changes in relative abundance of sharks and rays on Australian South East Fishery trawl grounds after twenty years of fishing
Authors: Graham K. J. , Andrew N. L. , Hodgson K. E.
Published: September 2002

Upper continental slope trawling grounds (200–650 m depth) off New South
Wales were surveyed with the same vessel and trawl gear and similar sampling
protocols in 1976–77 (during the early years of commercial exploitation)
and in 1996–97. The 1996–97 mean catch rate of sharks and rays,
pooled for the main 15 species (or species groups), was ~20% of the
1976–77 mean. Individual catch rates were substantially lower in
1996–97 for 13 of the 15 species or species groups. The greatest decline
was observed for dogsharks of the genus Centrophorus,
which were most abundant in 1976–77 but rarely caught 20 years later. In
contrast, 1996–97 catch rates of spiky dogshark
(Squalus megalops) and, to a lesser extent, whitefin
swell shark (Cephaloscyllium sp. A) were similar to
those in 1976–77. Trawling during 1979–81 provided data for nine
species, albeit not corrected for larger gear size, and the pooled mean catch
rate for sharks and rays in the depth range 300–525 m was ~28% of
the mean for 1976–77. The results suggest that the biomass of most
species of sharks and rays declined rapidly as the fishery developed and is
now at very low levels.
History of Australia's South East Fishery: a scientist's perspective
Authors: Tilzey R. D. J. , Rowling K. R.
Published: September 2002

The South East Fishery is one of Australia’s oldest fisheries. Early
research on this trawl fishery centred on tiger flathead, the major target
species. In the 1970s, the Federal Government actively encouraged fishery
development and funded several trawl surveys. Profitable catch rates and
optimistic assessments of resource size caused a rapid expansion of the trawl
fleet. Separate jurisdictions hampered strategic approaches to SEF-wide
research until 1978. Most SEF research in the mid 1960s to mid 1980s was
conducted by State fisheries agencies, but federal involvement increased
thereafter. A management shift in 1992 to Individual Transferable Quotas saw
stock assessment become the major research priority. Industry involvement in
the stock assessment process has increased markedly over the past decade and
communication between scientists, managers and industry has improved.
Predictive models are still limited by poor biological data for most quota
species. Stock assessment uncertainty necessitates the increasing use of risk
assessments and management strategy evaluation. Assessment scientists are
frustrated by limited resources for research and the perceived reluctance of
managers to adopt more precautionary approaches to uncertainty. Since ITQ
management, fishing effort has risen significantly and concerns have been
expressed about the stock status of several SEF species. Recent federal
environmental legislation is now directing more attention towards effects of
fishing and resource sustainability issues.
Review of progress in the introduction of management strategy evaluation (MSE) approaches in Australia's South East Fishery
Authors: Punt André E. , Smith Anthony D. M. , Cui Gurong
Published: September 2002

The MSE approach provides a simulation-based framework within which harvest
strategies, stock assessment methods, performance indicators and research
programmes can be compared. This approach has been used in the Australian
South East Fishery (SEF) to assess harvest strategies for the over-exploited
eastern gemfish resource and to compare different levels of discard monitoring
for blue grenadier. The main challenges to use of the MSE approach in the SEF
are poorly specified management objectives and the lack of quantitative stock
assessments on which to build operating models for many of the species.
Endobiont infestation, shell strength and condition index in wild populations of New Zealand abalone, Haliotis iris
Authors: Dunphy Brendon J. , Wells Rufus M. G.
Published: September 2002

Anecdotal suggestions that abalone in northern New Zealand are more heavily
infested with endobiont sponges and polychaetes than those in the south led to
a comparison of populations in the two regions. Shells from wild populations
of Haliotis iris were examined by X-ray analysis to
evaluate the degree of infestation and penetration. The mechanical strength of
shells and condition index of the abalone were measured and compared with the
degree of endobiont infestation. There were no significant differences in
measured characteristics in abalone from the northeastern region of New
Zealand (36°16′–36°22′S) compared
with those from the South Island
(40°44′–41°11′S) nor among
populations within these regions. Shell strength, previously unknown for
abalone, was considerably weakened by bifacial porosis and was correlated with
condition index.
Isolation and expression of a cinnamyl alcohol dehydrogenase cDNA from perennial ryegrass (Lolium perenne)
Authors: McAlister Fiona M. , Lewis-Henderson Wendy R. , Jenkins Colin L. D. , Watson John M.
Published: September 2002

A perennial ryegrass (Lolium perenne L.) cDNA library
was screened with a PCR-amplified cad DNA fragment
generated from ryegrass cDNA template using degenerate oligonucleotide
primers. A full-length cDNA (LpeCad1) was isolated and
confirmed to encode a cinnamyl alcohol dehydrogenase (CAD) enzyme by
expression of activity in Escherichia coli. The
recombinant enzyme catalyses conversion of coniferaldehyde and sinapaldehyde
with similar efficiency, and apparent K
m values below 10 µM were determined for these
substrates, whereas weak substrate inhibition occurs above this concentration.
The predicted perennial ryegrass CAD was very similar (88–87percnt;
amino acid sequence identity) to the only other monocotyledonous plant CAD
sequences available, those of maize and sugarcane, respectively. Southern blot
hybridization analysis indicated that there may be two or three
cad genes, or alleles, in perennial ryegrass. The
ryegrass LpeCad1 gene resembles the maize
cadgene in showing strong expression in root and stem
tissues, but is also expressed at lower levels in shoot, leaf sheath, leaf
blade and floral tissues.
Costs of protein turnover and carbohydrate export in leaves of sun and shade species
Authors: Noguchi Ko , Go Chun-Sim , Miyazawa Shin-Ichi , Terashima Ichiro , Ueda Shingo , Yoshinari Tadashi
Published: September 2002

In mature leaves, adenosine triphosphate (ATP) provided by respiration is used
for maintenance of leaves and carbohydrate export (starch mobilisation and
phloem loading). The main maintenance processes of mature leaves include
turnover of existing structures (e.g. proteins and membranes) and the
trans-membrane transport of solutes. In order to mechanistically estimate
these costs in mature leaves and compare them between sun and shade species,
we measured the costs of protein turnover and carbohydrate export in mature
leaves of Alocasia odora (Lodd.) Spach., a
shade-tolerant species, and Phaseolus vulgaris L., a sun
species, in the night. We estimated the rate of ATP production from the rate
of O 2 uptake, taking account of the contribution of the
alternative respiratory pathway, assessed by the O 2
isotope fractionation technique. The energy consumption of protein turnover
was estimated from the decrease in the rate of ATP production in the presence
of an inhibitor of cytosolic protein synthesis. Examination of the anatomy of
the minor veins in the leaves revealed that A. odora
employs symplastic phloem loading, while P. vulgaris was
reported to employ apoplastic loading. Based on these phloem loading types and
the difference between the rate of carbohydrate decrease and the CO
2 efflux rate in the leaves, we calculated the ATP cost
for carbohydrate export. The costs estimated for two processes amounted to
about 40% of the ATP production rate in A. odora
and 80% in P. vulgaris. The absolute costs for
the two processes in the leaves of A. odora were much lower than those of P.
vulgaris. Both the cost of protein turnover per unit leaf nitrogen and that of
carbohydrate export per exported carbon were lower in the leaves of
A. odora. Low ATP consumption rates by these cellular
processes would explain the low respiratory rate in
A. odora.
Protective enzymes against reactive oxygen species during ripening of tomato (Lycopersicon esculentum) fruits in response to low amounts of UV-C
Authors: Barka Essaid Ait
Published: September 2002

In previous studies with tomato (Lycopersicon esculentum
L.) exposed to a low level (3.7 kJ m –2) of UV-C
(λ: 254 nm) radiation, which is defined as a beneficial level, we
report a delay in fruit ripening by at least 1 week for treated fruit. In the
present study, we investigate the changes in the activities of different
enzymes involved in defense mechanisms, such as guaiacol peroxidase, ascorbate
peroxidase, catalase, superoxide dismutase, ascorbate oxidase, lipoxygenase
and phenylalanine ammonia lyase in tomato fruit in response to a beneficial
level of UV-C. The irradiation leads to an increase in the guaiacol peroxidase
and ascorbate peroxidase activities, whereas catalase activity remains similar
to the control. The activities of superoxide dismutase and ascorbate oxidase
were significantly reduced after UV-C exposure. In UV-C-treated fruit, an
increase of lipoxygenase and phenylalanine ammonia lyase activities occurred
within the first 5 d, followed by a second period in which these activities
were below those of the control. Our study suggests that the level of UV-C
used induced a rapid but moderate accumulation of photooxidation products, to
which plants react by stimulating their defence mechanisms against oxidation.
This activation may explain the delay observed in ripening and senescence of
irradiated tomato fruit.
Diurnal changes in non-structural carbohydrates in leaves, phloem exudate and fruit in ‘Braeburn’ apple
Authors: Klages Karin , Donnison Helen , Wünsche Jens , Boldingh Helen
Published: September 2002

Diurnal changes in carbohydrates in leaves, phloem exudate and within fruitwere determined in apple trees grown under high, low or no crop load. Inleaves, diurnal patterns of carbohydrate concentrations were most distinct inhigh-cropping trees and least so in non-cropping trees. In phloem exudate,sorbitol comprised about 65–70% of sugars and sucrose30–35%, with clear diurnal patterns in the amounts. Phloemexudates from stalks of sun and shade fruit were similar. Fruit carbohydratesshowed little diurnal variation. Crude fruit extracts showed little differencein sucrose synthase (SS, EC 2.4.1.13) activity between crop loads, whilesucrose phosphate synthase (SPS, EC 2.4.1.14) activity in high-cropping treespeaked at night and in low-cropping trees in the morning. SPS activity inshade fruit from high-cropping trees was only half of that in sun fruit (atmidday). Results indicate that the greater weight of individual fruit from lowcrop loads is primarily due to greater supply from the source, rather thanhigher metabolic activity in the sink, compared to fruit from high crop loads.In contrast, fruit size differences in sun and shade fruit of high-croppingtrees appear to be due to differences in sink metabolism rather than supplyfrom the source.
Carbon and water economy of Australian NAD-ME and NADP-ME C4 grasses
Authors: Ghannoum Oula , von Caemmerer Susanne , Conroy Jann P.
Published: September 2002

C4 grasses are grouped into three biochemical subtypes,NAD malic enzyme (NAD–ME), NADP malic enzyme (NADP–ME)and phosphoenolpyruvate carboxykinase (PCK), possessingcharacteristic leaf anatomy, biochemistry and physiology. This studyinvestigates the physiological implications of these differences by comparing growth, water use efficiency (WUE, dry matter gain per unit water transpired) and gas exchange characteristics of NAD–MEand NADP–ME C4 grasses belonging to threetaxonomic groups (main Chloroid assemblage, Paniceae and Andropogoneae). Wegrew 28 C4 grasses from seeds for 6 weeks in aglasshouse under ample water and nutrients in winter and summer. Theinter-specific variation in plant dry mass (30-fold) was much greater thanthat in WUE (2-fold). There was no significantdifference in average WUE between NAD–ME andNADP–ME grasses. Average plant dry mass andWUE were highest in the Paniceae (mostlyNADP–ME), lowest in the Andropogoneae (NADP–ME) and intermediate in the Chloroid (NAD–ME). CO2assimilation rate (A), stomatal conductance(g) and the ratio of intercellular to ambient CO2 partial pressure (pi/p a )were measured under standard conditions at high light. AverageA and g were slightly higher inNADP–ME than NAD–ME grasses, but pi/p awas similar for the two subtypes. A did not differbetween winter and summer experiments in spite of a 3-fold difference inmaximal daily irradiance. Dry matter accumulation correlated positively withleaf area ratio (LAR; plant leaf area per unit plant drymass) and specific leaf area (SLA; leaf area per unitleaf dry mass) in NAD–ME, but not NADP–ME, grasses.Variation in A (expressed on a per area basis) did notcorrelate with biomass accumulation or SLA. Whenexpressed on a dry mass basis, A correlated withSLA in all C4 grasses. This studyshows that there is large inter-specific variation in growth among the C4 grasses, but average WUE andA/g are similar forNAD–ME and NADP–ME species under well-wateredconditions.
Characterization of soluble calcium calmodulin-dependent and -independent NAD+ kinases from Avena sativa seeds
Authors: Gallais Stéphane , Crescenzo Marie-Anne Pou de , Laval-Martin Danielle L.
Published: September 2002

Two NAD+ kinase isoforms were separated from
Avena sativa L. embryo extracts from dormant and
after-ripened seeds by size-exclusion chromatography: a 410-kDa
Ca2+–calmodulin (CaCam)-independent
NAD+ kinase was observed in both dormant and
after-ripened seeds and a 63-kDa CaCam-dependent isoform was found to be
abundant only in embryos of after-ripened Avena seeds.
The characterization of these two isoforms showed differences in
Michaelis–Menten constant
(Km) values and enzymatic
mechanisms, as well as distinct sensitivities to inhibitors, oxidants,
reductants and CaCam inhibitors. It is therefore proposed that the 410-kDa
isoform could be a ‘housekeeping’ enzyme with
Km values corresponding to the
intracellular concentrations of ATPMg and NAD+. We
speculate that the 63-kDa CaCam-dependent NAD+
kinase, possessing a low Km, would
be mainly involved in the adaptation and response of
A. sativa to environmental signals or stresses through
changes of redox potential and/or calcium signalling pathways.
Endogenous auxins and embryogenesis in Phaseolus coccineus
Authors: Picciarelli Piero , Ceccarelli Nello , Paolicchi Fabio , Calistri Gianni
Published: September 2002

The occurrence and the dynamics of free and bound indole-3-acetic acid (IAA)
in different parts of Phaseolus coccineus L. seeds were
investigated at various developmental stages. Results show that free and bound
IAA content in the single seed parts is quite different, and changes with
different patterns during seed growth. The highest concentration of total IAA
was found in early-heart stage embryos, while the total IAA concentration in
the suspensor at early-heart stage is much lower than in the embryos, and
remains almost constant in the later stages. Integuments have an intermediate
content at the first two developmental stages, while showing the highest
concentration of total IAA at the cotyledonary stage. Concerning the
percentage of free IAA in relation to the total pool, we found that in the
embryos free IAA accounts for 26–28% in the first two stages then
increases up to 44% at the cotyledonary stage. In suspensors, the
percentage of free IAA is much higher (90%) in all developmental
stages. We discuss the idea that the different level of auxin between embryos
and the suspensor might play an important role in the establishment of embryo
polarity.
Photoinhibition in indica and japonica subspecies of rice (Oryza sativa) and their reciprocal F1 hybrids
Authors: Jiao Demao , Ji Benhua
Published: September 2002

Photoinhibitory performance and its physiological basis have been studied in
Oryza sativa L. subspecies indica
and japonica, and their reciprocal
F1 hybrids. The results demonstrate that the
japonica ssp. was usually more tolerant to
photoinhibition, indicated by higher maintaining capacity of D1 protein (less
degradation), higher induced superoxide dismutase (SOD) activity and longer
duration of the activity. Compared with japonica, the
indica ssp. was more sensitive to photoinhibition, and
exhibited more degradation of D1 protein and a much larger xanthophyll pool. A
statistically significant positive correlation exists between D1 protein
content and
Fv/Fm,
PSII activity and Pn during
photoinhibition (r2 = 0.98,
0.93, 0.95, respectively, P < 0.01). This result
further supported the hypothesis that D1 protein encoded by plastid genes
might play an important physiological role in the mechanism of
photoinhibition. This hypothesis is also enhanced by the fact that the
capacity of D1 protein synthesis mediated the components and cycle of
xanthophyll and non-photochemical quenching in treatment with streptomycin, a
D1 protein synthesis inhibitor, while the xanthophyll cycle had a
photoprotective role for D1 protein and
Fv/Fm
in treatment with DDT, a xanthophyll cycle inhibitor. The photoinhibition of
reciprocal F1 hybrids between
japonica and indica is mainly
intermediate, but somewhat inclined to the maternal line. This demonstrates
that the basic feature of photoinhibition was controlled by the interaction of
an intrinsic factor, D1 protein encoded by plastid genes, with the xanthophyll
cycle, as well as SOD, controlled by nuclear genes. Since the response to
photoinhibitory treatment of indica–japonica
F1 hybrids seems to depend on female parents, we propose
to select and use photoinhibition-tolerant varieties as female parents for
generation of photoinhibition-tolerant hybrids.
Analysis of cell wall hardening and cell wall enzymes of salt-stressed maize (Zea mays) leaves
Authors: Cramer Grant R. , Schmidt Connie L. , Bidart Chad
Published: September 2002

It has been indicated that salinity inhibits maize
(Zea mays L.) leaf growth and leaf cell expansion by
increasing the apparent yield threshold of the cell wall. We tested whether
this increase in the apparent yield threshold was a physical property of cell
walls, using in vitro creep-type assays. Salinity had no
significant effects on cell wall structural properties based upon several
different in vitro assays. In support of these results,
there were no differences between control and salt-stressed plants in their
total apoplastic concentration of cell wall proteins, in the activity of
apoplastic peroxidases or xyloglucan endotransglycosylase. We conclude that
short-term salinity does not appear to inhibit maize leaf elongation by
hardening the physical structure of the cell walls of the growing zone.
Water deficit in combination with high solar radiation leads to midday depression of a-tocopherol in field-grown lavender (Lavandula stoechas) plants
Authors: Munné-Bosch Sergi , Schwarz Karin , Alegre Leonor
Published: September 2002

α-Tocopherol (vitamin E) is a lipophilic antioxidant, which protects
chloroplasts from oxidative damage. Diurnal variations in α-tocopherol,
chlorophylls and carbon dioxide assimilation rates were measured during two
consecutive summers to evaluate the photosynthetic response to drought and the
protective role of α-tocopherol in 2- and 3-year-old lavender
(Lavandula stoechas L.) plants grown under a
Mediterranean climate. Lavender plants showed one-peaked diurnal time courses
of photosynthesis and progressive decreases in the carbon dioxide assimilation
rates as drought progressed during the summer. In severe stress and when
photosynthesis was highly reduced, the chlorophyll content of leaves
decreased. Midday depressions of α-tocopherol were observed when high
solar radiation was superimposed on water deficit, indicative of the
susceptibility of lavender plants to oxidative stress. However, lavender
plants did not suffer from photoinhibitory damage throughout the experiment,
indicating the contribution of α-tocopherol (in addition to other
possible mechanisms) in the protection of chloroplasts from drought-induced
oxidative damage.
Effects of growth under UVA radiation on CO2 assimilation, carbon partitioning, PSII photochemistry and resistance to UVB radiation in Brassica napus cv. Topas
Authors: Savitch Leonid V. , Pocock Tessa , Krol Marianna , Wilson Kenneth E. , Greenberg Bruce M. , Huner Norman P. A.
Published: September 2002

The effects of growth of Brassica napus L. cv. Topas
under PAR or PAR+UVA radiation was assessed with respect to sensitivity
to subsequent exposure to UVB radiation. Despite the fact that growth under
PAR+UVA induced minimal effects in photosystem II (PSII) photochemistry,
growth under PAR+UVA inhibited the accumulation of the photosynthetic end
products, sucrose and starch. This was associated with a decreased capacity
for ribulose 1,5-bisphosphate (RuBP) regeneration, a decreased capacity for
light- and CO 2 -saturated rates of
CO2 assimilation, a decrease in the apparent quantum
yield for CO2 assimilation, an over-reduction of
chloroplast stroma, an increased susceptibility to the feedback effects on
photosynthesis and a stimulation of glycolysis compared to controls grown
under PAR. Subsequent exposure to UVB decreased the maximum Rubisco activity
in leaves of both PAR- and PAR+UVA-grown plants. However, the decrease in
the capacity for CO2 assimilation in PAR-grown plants
exposed to UVB did not appear to be associated with limitations at the level
of PSII linear electron transport, but rather with a decreased capacity for
sucrose biosynthesis, limited triose-P utilization and a decreased capacity
for RuBP regeneration. In contrast, the decreased capacity for CO
2 assimilation in PAR+UVA-grown plants exposed to
UVB was associated with an inhibition of PSII photochemistry and a decreased
supply of ATP. Thus, growth under UVA radiation appears to induce
feedback-limited photosynthesis and does not enhance resistance of
Brassica napus to UVB radiation.
Seasonal changes in photosynthetic pigments and antioxidants in beech (Fagus sylvatica) in a Mediterranean climate: implications for tree decline diagnosis
Authors: García-Plazaola José Ignacio , Becerril José María
Published: September 2002

Seasonal changes in all major and minor photosynthetic pigments and
antioxidants were studied in sun and shade in beech
(Fagus sylvatica L.) leaves and buds under Mediterranean
conditions. Both sun and shade leaves differed progressively in their
biochemical and morphological characteristics during the course of leaf
ageing. Sun leaves were 3-fold thicker, pigment content was highly reduced and
the leaves were protected by a much more powerful antioxidative system.
Pigment content decreased progressively during summer in sun leaves and
remained stable in shade leaves. From July to September, there was no
chlorophyll (Chl) biosynthesis, so photodegradation of Chl was not compensated
by production of new Chl. This reduction in Chl occurred in parallel with an
increment in tocopherols. Natural leaf senescence occurred first in sun
leaves. During this process, Chl was completely degraded, xanthophylls were
esterified with fatty acids, and violaxanthin was converted into zeaxanthin,
while carotenes remained stable. One of the main indicators of tree decline
and air pollution is accelerated leaf ageing, and this process is
characterised in beech leaves by tocopherol and pigment destruction, so we
have used these criteria to verify whether these parameters can be used as
early indicators of tree decline. All pigments and antioxidants (including
α -tocopherol) decreased with beech decline, except xanthophyll cycle
pigments. As reduction of these compounds is concomitant with a similar level
of Chl degradation, Chl determination is proposed as a simple method
sufficient to predict the early stages of beech decline at a biochemical
level.
Effects of environmental factors and endogenous signals on N uptake, N partitioning and taproot vegetative storage protein accumulation in Medicago sativa
Authors: Noquet Carine , Avice Jean-Christophe , Ourry Alain , Volenec Jeffrey J. , Cunningham Suzanne M. , Boucaud Jean
Published: September 2002

Our objectives were to study the regulation of N partitioning within tissues
of non-nodulated alfalfa (Medicago sativa L.) and N
storage in taproots as vegetative storage proteins (VSP) of 15, 19, and 32 kDa
and β-amylase (57 kDa) by environmental (photoperiod, temperature, N
availability) and endogenous factors (methyl jasmonate). When compared to
long-day conditions (LD, 16 h day/8 h night), short-day (SD, 8 h
day/16 h night), exposure to low temperature (5˚C) or application of
methyl jasmonate (MeJA, 100 M ) for 35 d reduced the biomass shoot/ root
ratio and modified the source–sink relationships for N. SD and MeJA
treatments resulted in partitioning of N to taproots and a concomitant
accumulation of VSPs. In comparison with LD, SD treatment also stimulated
β-amylase gene expression 2.5-fold. Although low temperature increased the
N partitioning to root tissues and the accumulation of soluble proteins in
taproot, VSP concentration and β-amylase mRNA levels remained low.
Increasing N concentration from 1 to 5 mM KNO3 doubled
the total dry matter but did not affect the N partitioning within the plant,
VSP accumulation, or ‚ β-amylase expression. These results
suggested that short photoperiod can result in preferential N allocation
toward taproots with a concomitant induction of VSP accumulation.
Generation of selectable marker-free transgenic rice using double right-border (DRB) binary vectors
Authors: Lu Hui-Juan , Zhou Xue-Rong , Gong Zhu-Xun , Upadhyaya Narayana M.
Published: September 2002

Currently employed transformation systems require selectable marker genes
encoding antibiotic or herbicide resistance, along with the gene of interest
(GOI), to select transformed cells from among a large population of
untransformed cells. The continued presence of these selectable markers,
especially in food crops such as rice (Oryza sativa L.),
is of increasing public concern. Techniques based on DNA recombination and
Agrobacterium-mediated co-transformation with two binary
vectors in a single or two different Agrobacterium
strains, or with super-binary vectors carrying two sets of T-DNA border
sequences (twin T-DNA vectors), have been employed by researchers to produce
selectable marker-free (SMF) transgenic progeny. We have developed a double
right-border (DRB) binary vector carrying two copies of T-DNA right-border
(RB) sequences flanking a selectable marker gene, followed by a GOI and one
copy of the left border sequence. Two types of T-DNA inserts, one initiated
from the first RB containing both the selectable gene and the GOI, and the
other from the second RB containing only the GOI, were expected to be produced
and integrated into the genome. In the subsequent generation, these inserts
could segregate away from each other, allowing the selection of the progeny
with only the GOI. We tested this vector using two selectable marker genes and
successfully obtained progeny plants in which the second selectable marker
gene segregated away from the first. Using the DRB binary vector system, we
recovered SMF transgenic lines containing a rice ragged stunt virus
(RRSV)-derived synthetic resistance gene in the rice cultivars Jarrah and Xiu
Shui. Approximately 36–64% of the primary transformants of
these cultivars yielded SMF progeny. Among SMF Jarrah transgenic progeny
<50% of plants contained the RRSV transgene. Thus, we have developed
an efficient vector for producing SMF plants that allows straightforward
cloning of any GOIs in comparison with the published ‘twin T-DNA’
vectors.
Localisation and expression of zeaxanthin epoxidase mRNA in Arabidopsis in response to drought stress and during seed development
Authors: Audran Corinne , Liotenberg Sylviane , Gonneau Martine , North Helen , Frey Anne , Tap-Waksman Karine , Vartanian Nicole , Marion-Poll Annie
Published: September 2002

Abscisic acid (ABA) is involved in seed development and plant adaptation to
environmental stresses. ABA is synthesized from cleaved xanthophylls and
zeaxanthin epoxidase (ZEP) is the enzyme responsible for the conversion of
zeaxanthin to violaxanthin. In this study, we have characterized the
ABA1 gene (AtZEP) of
Arabidopsis thaliana L. and show that this complements
the aba1 mutant, defective in zeaxanthin epoxidation.
The molecular basis for two aba1 mutant alleles has been
determined and the reduction in their AtZEP transcript
levels correlates with the molecular defect identified. As
AtZEP mRNA abundance was not affected in two other
ABA-deficient mutants (aba2 and
aba3) and in two ABA-insensitive mutants
(abi1 and abi2), no feedback
regulation of ABA biosynthesis seems to occur at the level of
ZEP transcription. Steady state transcript levels
increased in roots during rapid water stress as well as progressive drought
stress, providing evidence that zeaxanthin epoxidation contributed to the
regulation of ABA biosynthesis in roots and consequently to the plant adaptive
response to hydric stress. In seeds in situ
hybridization analysis detectedAtZEP mRNA in the embryo
cells from the globular stage to desiccation phase. In contrast, expression of
AtZEP in maternal tissues was specific to the maturation
phase. These results are discussed in relation to the role of ABA both in
response to drought stress and in seed development.
Interaction between reactive oxygen species and nitric oxide in drought-induced abscisic acid synthesis in root tips of wheat seedlings
Authors: Zhao Zhiguang , Chen Guocang , Zhang Chenglie
Published: September 2002

Abscisic acid accumulation and oxidative stress are two common responses of
plants to environmental stresses. However, little is known about their
relationships. The purpose of this article is to investigate the effects of
reactive oxygen species and nitric oxide on the plant hormone abscisic acid
synthesis in root tips of wheat (Triticum aestivum L.)
seedlings under drought stress. Detached root tips were subjected to drought
stress by naturally evaporating until 20% of their fresh weights were
lost. The activities of superoxide synthases and nitric oxide synthase (EC
1.14.13.39) increased after 20 min of treatment and abscisic acid began to
accumulate 60 min later. The induction of abscisic acid by drought was
strongly blocked by pretreating the root tips with reactive oxygen species
eliminators tiron or ascorbate acid, and with nitric oxide synthase inhibitor
Nω-nitro-L-arginine or nitric oxide eliminator
2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide. Consistent with these
results, reactive oxygen species generators diethyldithiocarbamic acid,
xanthine–xanthine oxidase and triazole or nitric oxide donor sodium
nitroprusside can also induce abscisic acid accumulation in root tips of wheat
seedlings. While potentiated by reactive oxygen species, the effect of sodium
nitroprusside on abscisic acid accumulation was blocked by
2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide. Based on these
results, we suggest that reactive oxygen species and nitric oxide play
important roles in drought-induced abscisic acid synthesis in plant, they may
be the signals through which the plant can ‘sense’ the drought
condition.
Photosynthetic and fluorescence light responses for kiwifruit (Actinidia deliciosa) leaves at different stages of development on vines grown at two different photon flux densities
Authors: Greer Dennis H. , Halligan Elizabeth A.
Published: September 2002

Potted kiwifruit, Actinidia deliciosa [(A.Chev.)
C.F.Liang et A.R.Ferguson], vines were grown at two controlled photon
flux densities (PFD) of 250 and 1100 mol m–2
s–1 for 110 d to examine ontogenetic and PFD
responses of photosynthesis. Oxygen evolution of detached leaf disks and PFD
responses of both photosynthesis and chlorophyll fluorescence of attached
leaves were measured. A range of leaves, at different nodal positions on the
vines, were used and measurements were repeated over time on the same leaves
as they expanded. Results showed that PFD responses of photosynthesis of the
high- and low-PFD-grown vines are typical for sun/shade differentiation in
Pmax and in the PFD for light
saturation. The low-PFD-grown vines saturated at a PFD of 680 mol
m–2 s–1 and had a mean
maximum rate of 12.0 mol m–2
s–1 while high-PFD-grown vines saturated at 960
mol m–2 s–1, with a
mean maximum rate of 15.2 mol m–2
s–1. There were similar differences between the
two growth regimes in the electron transport rate (ETR) but non-photochemical
quenching (NPQ) was higher in the low than in the high-PFD-grown vines. Young
expanding leaves were characterised by low efficiency of both photochemistry
and photosynthesis, low capacity for both electron transport through
photosystem II and CO2 fixation capacity but by high
respiration and a high capacity for non-radiative thermal dissipation. When
the leaves had fully expanded, there were marked shifts towards higher photon
yields, ETR and Pmax and low
respiration and NPQ. In comparison with the effects of growth PFD, ontogenetic
effects on development of photosynthetic competence had greater influences on
the PFD responses of photochemistry and photosynthesis.
Colonisation by arbuscular mycorrhizal fungi changes the relationship between phosphorus uptake and membrane potential in leek (Allium porrum) seedlings
Authors: Ayling Sarah M. , Smith Sally E. , Smith F. Andrew
Published: September 2002

The effect of colonisation by arbuscular mycorrhizal (AM) fungi on the
relationship between phosphorus (P) uptake and root membrane electric
potential difference (p.d.) was investigated in leek
(Allium porrum L.). Plants were grown, with or without
the AM fungus Scutellospora calospora (Nicolson and
Gerdemann) Walker and Sanders, in soil. P uptake and root p.d. were
correlated; plants with the highest P concentration in the shoot had the most
negative p.d. This relationship was strong in non-mycorrhizal leeks
(r2 = 84–98%),
but weaker in mycorrhizal leeks
(r2 = 55–64%),
consistent with the idea that in mycorrhizal roots the fungal hyphae are the
principal site of P uptake.
The efficiency of boron utilisation in canola
Authors: Stangoulis James C. R. , Brown Patrick H. , Bellaloui Nacer , Reid Robert J. , Graham Robin D.
Published: September 2002

Boron (B) deficiency is a common abiotic stress in many countries and is known
to reduce canola yields. Growing B-efficient canola cultivars on deficient
soils can reduce the impact of this deficiency, but to date little is known of
the mechanisms associated with the efficiency trait. This work investigated
the factors underlying the observed genotypic variation in the ability of
different cultivars of canola (Brassica napus L.) to
grow under low B supply. Previous studies have identified the cultivars
Huashuang-2 and Dunkeld as B-efficient and the cultivar Barossa as
B-inefficient. It was found that in Huashuang-2, efficiency was not related to
uptake of B to the shoots, possibly indicating efficiency in B utilisation. A
correlation was established between B efficiency and the ratio of the B
concentration in the younger relative to the older leaves. Comparison of the
distribution of B in young and old leaves under deficient and adequate B
conditions showed that when B was limited, the concentration of B in the older
leaves decreased with plant age, whereas when sufficient B was supplied, the
concentration in these leaves continued to increase with age. The loss of B
from mature leaves under deficient conditions suggested retranslocation to
other tissues. Experiments in which boric acid enriched with
10 B was applied to mature leaves showed that in only
one of the efficient cultivars, Huashuang-2, was B retranslocated to younger
leaves. In the other two cultivars, the sink for the 10
B exported from the older leaves was not identified. It was concluded that
there exist multiple mechanisms for B efficiency in canola.
K+ transport by Arabidopsis root hairs at low pH
Authors: Babourina Olga , Hawkins Barbara , Lew Roger R. , Newman Ian , Shabala Sergey
Published: September 2002

Mechanisms underlying changed K + uptake by plantsat low pH need to be deciphered. One possibility is that K+ acquisition is under the strict control of plasmamembrane potential (E m ), which,in turn, is affected by external pH. To test this hypothesis, we used themicroelectrode ion flux measurement (MIFE ) technique tostudy net K + and H +fluxes near Arabidopsis root hairs at different externalpH, KCl concentrations and clamped Em . Lowering the solution pH led to strong H+ influx, K + efflux andsignificant E m depolarisation.Addition of K + to the bathing media causedsignificant net K + uptake when external pH wasover the range 5.5–6.0. At external pH below 5.0, however, correlationbetween K + availability and net K+ uptake was negative. To explain this apparentparadox, measurements of net K + and H+ fluxes from the root hair surface were performedconcurrently with E m clamped at different values above and below the restingpotential (approx. –180 mV). Our data revealed a strong dependence ofnet K + flux on the clamping voltage. Clamping atvalues more negative than the resting potential caused a significant increasein K + uptake into the root hair; clamping at lessnegative values (–20 and 0 mV) caused significant net K+ efflux from the cell. Qualitatively similarresults were observed for net H + flux. Ourobservations indicate direct control of K + flux bychanging E m , and suggest thatE m depolarisation could be themain reason for the observed K + efflux at low pH.
On the use of thermodynamic methods to describe water relations in plants and soil
Authors: Roderick Michael L.
Published: September 2002

Both the existing theory as well as the measurements that have traditionally
been used to describe the water relations of plants in thermodynamic terms are
not consistent with standard thermodynamic theory. In this article, three main
errors are identified: (1) the assumption that the internal energy of a system
includes the gravitational potential energy, when it does not; (2) the
assumption that water spontaneously moves along gradients of chemical
potential, when the Gibbs theory predicts that it would spontaneously move
across phase boundaries, so that the chemical potential would be equal in
adjacent phases; and (3) the assumption that plants and soil are single-phase
systems, when they are in fact multi-phase systems. Examples are used to
demonstrate the above errors. Measurements which can be used to separate plant
and soil systems into bulk phases (i.e. solid, liquid and gas), which have
long been used by wood and soil scientists, are shown to be ideal for the
purpose of describing plant and soil systems using thermodynamic methods.
Polyamines as potential regulators of nutrient exchange across the peribacteroid membrane in soybean root nodules
Authors: Whitehead Lynne F. , Tyerman Stephen D. , Day David A.
Published: September 2002

The effect of cytoplasmic polyamines on peribacteroid membrane transport
processes in soybean (Glycine max L.) was investigated.
The concentration of free polyamines in soybean nodule cytoplasm has been
estimated by others to be in the micromolar range. The
H+ -ATPase was inhibited by 37 and 54% by
200 µM spermidine and putrescine, respectively. Spermine applied to the
cytoplasmic face of the peribacteroid membrane was found to inhibit both
inward and outward currents through a non-selective cation channel permeable
to ammonium (K d 2.1 µM at
–100 mV). Malate transport into intact symbiosomes was reduced by
15–30% by 15 mM spermidine, cadaverine and putrescine. A
non-specific stimulation of malate transport by polycations was found to occur
at concentrations in the micromolar range. The results suggest that polyamines
can affect all the peribacteroid membrane transport processes tested. In
particular, we conclude that the combined inhibitory effects of polyamines on
the ATPase and the ammonium channel have the potential to reduce nitrogen
supply to the plant in vivo. The possibility of
competing polyamine and ureide synthesis in the nodule is discussed.
Oscillations in proton transport revealed from simultaneous measurements of net current and net proton fluxes from isolated root protoplasts: MIFE meets patch-clamp
Authors: Tyerman Stephen D. , Beilby Mary , Whittington John , Juswono Unggul , Newman Ian , Shabala Sergey
Published: September 2002

Proton fluxes were measured non-invasively on patch-clamped protoplasts
isolated from wheat roots using an external H +
electrode to measure the electrochemical gradient in the external solution.
Under voltage clamp in the whole-cell configuration, the H
+ fluxes across the plasma membrane could be
measured as a function of voltage and time and correlated with the
simultaneous measurements of membrane current. Protoplasts could exist in
three states based on the current–voltage
(I–V) curves and the
flux–V curves. In the
pump-state where the membrane voltage
(Vm) was more negative than the electrochemical
equilibrium potential for potassium (E
K ), a net efflux of H +
occurred that was voltage-dependent such that the efflux increased as
Vm was clamped more positive. In the K-state, where
Vm was close to E
K , similar flux–V curves
were observed. In the depolarised state where Vm was
greater than E K the proton flux
was characterised by a net influx of H +
(H +
-influx state) that reversed direction at more positive
values of Vm. The inhibitory effect of DCCD and
stimulatory effect of fusicoccin were used to correlate current and H
+ flux through the H +
-ATPase for which there was reasonably good agreement within the limits of the
flux measurements. Some protoplasts were kept in the whole-cell configuration
for up to 3 h revealing slow sustained oscillations (period about 40 min) in H
+ flux that were in phase with oscillations in
free-running Vm. These oscillations were also observed
under voltage clamp, with membrane current in phase with H
+ flux, but which became damped out after a few
cycles. The oscillations encompassed the pump-state, K
+ -state and H +
-influx-state. The H +-
flux–V curves and
I–V curves were used to
model the electrical characteristics of the plasma membrane with H
+ -ATPase, inward and outward K
+ rectifiers, a linear conductance, and a passive H
+ influx possibly through gated proton channels.