bluuebunny/crossref_metadata_2025 huggingface dataset:
Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil
Authors: Lessa Rosangela , Santana Francisco M. , Batista Vandick , Almeida Zafira
Published: September 2002

Age and growth of the daggernose shark,
Isogomphodon oxyrhynchus, from northern Brazil were
determined from 105 vertebral sections stained with alizarin red-S
representing 46 males, 52 females and 7 specimens of unknown sex (58.4 to 141
cm-TL) and verified with length–frequency analysis of 1135 specimens
(632 females and 503 males, 58–160 cm ). Marginal increments did not
show significant differences throughout the year, and it was assumed that one
band is formed annually. Different tests provided varying results for growth
curve comparisons between sexes; the curves were similar, despite biological
differences. von Bertalanffy growth parameters estimated from back-calculated
mean lengths, observed mean lengths-at-age and length–frequency analysis
were of the same magnitude. Parameters generated from observed length-at-age
were chosen for describing growth for the species: L• 171.4 cm,
k 0.12 year –1 and
t0 –2.612 years. The largest
female aged from vertebrae was 12 years old, whereas the largest male was aged
at 7 years. Neonates, ~42.3 cm, showed one band in the vertebrae, formed at
birth, or soon thereafter. Males are mature at 103 cm or 5–6 years and
females at 115 cm or 6–7 years.
Resumo. A idade e o crescimento do cação
quati, Isogomphodon oxyrhynchus, do norte do Brasil foi
determinada usando 105 vértebras seccionadas e coradas com alizarina
vermelha-S de 46 machos, 52 fêmeas e 7 exemplares de sexo indeterminado
(58,4–141 cm-CT). Análise de distribuição de
frequência de comprimentos de 1135 indivíduos (632 femeas e 503
machos, 58–160 cm) foi utilizada como método de
verificação. Os incrementos marginais não mostraram
diferenças significativas ao longo do ano, assumindo-se que uma banda
é formada anualmente. Com diferentes testes, usados para comparar
curvas de crescimento entre os sexos, obteve-se resultados conflitantes; o
crescimento foi considerado idêntico entre os sexos, apesar das
diferenças biológicas entre machos e fêmeas. Os
parâmetros de von Bertalanffy estimados do retrocálculo,
comprimentos médios observados e da análise de comprimentos
foram semelhantes, tendo sido escolhidos para descrever o crescimento da
espécie: L• 8171,4 cm; k 0,12 year
–1 et
0 –2,612 years. Amaior fêmea cuja idade foi
estimada pelas vértebras tinha 12 anos enquanto o maior macho tinha 7
anos. Recém-nascidos de 42,3 cm apresentavam uma banda nas vertebras,
formada ao nascer, ou logo depois do nascimento. Machos estão maduros
em 103 cm ou 5–6 anos e fêmeas em 115 cm ou 6–7 anos.
Genetic subdivision of Roe’s abalone, Haliotis roei Grey (Mollusca : Gastropoda), in south-western Australia
Authors: Hancock Boze
Published: September 2002

Starch-gel electrophoresis was used to investigate population structure of the
commercially and recreationally exploited abalone,
Haliotis roei. The standardized variance in allelic
frequencies among 10 sites in south-western Australia indicated relatively
high levels of gene flow across the 3000 km range sampled (mean
FST 0.009). Sites showed no striking geographic trends
in allelic frequencies or apparent clustering, on the basis of
multidimensional scaling of GST as a measure of genetic
dissimilarity. A population structure of isolation-by-distance was evident
when pairwise measures of GST were related to geographic
distance (r = 0.45, P
<0.001). This relationship was evident beneath relatively high levels of
variability among pairwise comparisons of GST for sites
separated by small distances. The area of complete genetic mixing, or
neighbourhood size, was estimated to be less than the distance between the two
nearest sites, or 13 km. The apparent contradiction between relatively high
levels of gene flow across the species’ distribution, as indicated by a
low average FST, and substantial heterogeneity between
sites separated by 10s of kilometres, is discussed in the context of the
species’ biology, and management of the fishery.
Tidal mixing near the Kimberley coast of NW Australia
Authors: Cresswell G. R. , Badcock K. A.
Published: September 2002

A complex of reefs and islands atop raised topography that is 140 km long and
up to 35 km wide extends roughly westward from the Kimberley coast of NW
Australia. The surrounding seafloor has depths of 60–80 m. Satellite
images of sea surface temperature in spring, summer and autumn suggest that
tides commonly mix sub-thermocline waters to the surface along this ridge,
particularly along its western half, which includes Adele Island and
Churchill, Albert, Beagle and Mavis reefs. The cool surface waters (~3˚C
cooler than surroundings) are seen where the depths are less than ~50 m, such
that they closely reflect the bottom topography. The semi-diurnal tides have a
maximum daily range of ~10 m and it is when the range exceeds ~3 m that mixing
to the surface occurs. Thus, the mixing can cease during some neap periods.
Historical data from the shelf show the sub-thermocline water to be
nutrient-rich (nitrate concentrations of 6.0 µM), so the mixing is
likely to be important for the marine ecosystem. As winter approaches, the
distinctive cool mixed region around the Adele–Mavis banks is
overwhelmed by surface cooling, and historical ship data reveal that the
stratification on the surrounding shelf disappears.
Effect of coastal cities on surficial sediments mantling an adjacent high-energy continental margin - central New South Wales, Australia
Authors: Matthai C. , Birch G. F.
Published: September 2002

Trace metal (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) concentrations in the fine
fraction (<62.5 µm) of surficial sediments adjacent to the major
urban centres of Sydney, Newcastle and Wollongong on the central New South
Wales (NSW) continental margin, Australia, are elevated above regional
background. The nature of enrichment off these major urban centres is
distinct. The fine fractions of sediments adjacent to Newcastle are enriched
in Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn, associated with the disposal of dredged
harbour spoil in an offshore dumpsite, whereas adjacent to Sydney, enrichment
of Cu, Pb and Zn in the fine fraction of sediments results mainly from the
disposal of large volumes of sewage effluent. The source and regional
dispersion of trace metals on the central-NSW continental margin can only be
established from analysis of the fine fraction of the sediment, because total
sediment distributions of contaminants are confounded by a highly variable
sediment texture. Generally, low mud contents (<2%) and low
concentrations of trace metals in inner-shelf sediment are evidence of
efficient dispersal of fine material and associated contaminants on this
high-energy continental margin.
The limits of sodium/calcium interactions in plant growth
Authors: Reid Robert J. , Smith F. Andrew
Published: September 2002

The amelioration of Na toxicity by
supplementation of Ca in the growth medium was investigated in wheat with the
aims of (1) identifying the Ca-dependent processes that determine the growth
responses and (2) defining the limits to Ca effects on these processes. Growth
of wheat seedlings was strongly inhibited by 150 mM NaCl but improved as the
Ca concentration in the nutrient medium was increased up to 2.34 mM. Further
increasing Ca to 10 mM did not increase growth, nor did foliar application of
Ca. Even at high concentrations of Ca, the maximum growth was only
approximately 50% of the growth at low salinity. We conclude that the
main component of improved growth caused by Ca was via its apoplastic effects
on the transport of Na and K across the root plasma membrane, rather than by
increasing root or shoot Ca concentrations. There was no evidence that high
salinity inhibited Ca uptake to the shoot. The limits to improvement of growth
by Ca appear to relate to the fact that, although Ca is able to ameliorate the
toxicity caused by high intracellular Na, it is not able to overcome the
osmotic deficits associated with high salinity.
An improved method for the measurement of cell wall invertase activity in sugarcane tissue
Authors: Albertson Peter L. , Peters Kirrily F. , Grof Christopher P. L.
Published: September 2002

Extraction and assay methods were developed for the determination of both
soluble and cell wall invertase activity in sugarcane
(Saccharum sp.) from minimal (0.5 g) tissue. Cell wall
invertase (CWI) was measured using a pellet mix procedure and the pH optima
ranged between pH 3.2 and 3.6. The pH optima for the soluble invertases were
4.5 and 7.3 for soluble acid (SAI) and neutral (NI) invertase, respectively.
At low pH, acid hydrolysis of sucrose was observed and its spurious effect on
measured enzyme activity was removed by the inclusion of additional controls
run in parallel, which lacked crude plant extract. Invertase activity was
examined in sugarcane tissues of varying ages. In leaves and stem, the SAI
activity was greatly reduced in mature tissue extracts. Similarly, the CWI
activity was reduced in older leaves. In contrast, a less marked drop in NI
activity was observed in extracts from old leaves and activity from stem
extracts remained constant irrespective of tissue age. The role of SAI has
been linked to growth and differentiation and these observations suggest that
CWI may also be intrinsically involved in these processes. NI appears to have
a housekeeping role in maintaining hexose concentrations within the cytosol.
Identification of differentially expressed genes during early development of tomato fruit. Characterisation of a novel cDNA coding for a RAD23 protein.
Authors: Lemaire-Chamley Martine , Petit Johann , Causse Mathilde , Raymond Philippe , Chevalier Christian
Published: September 2002

Before the onset of ripening, tomato fruit development comprises three
distinct phases: fruit set, a cell division phase and a cell expansion phase.
In this study, we used the method of mRNA differential display in order to
isolate tomato genes specifically expressed during these early phases of fruit
development. Among 40 differen-tial bands, nine cDNAs were selected for
further investigations based on their identification after nucleotide
sequencing. We isolated the full-length cDNA corresponding to one of these
fragments, coding for RAD23, a protein involved in the excision repair system,
thus providing new sequence information on a poorly characterised protein in
plants. All the isolated cDNAs were mapped on the tomato genome and their
expression studied by northern blot and semi-quantitative RT–PCR during
early fruit development and in vegetative organs of tomato plants.

The sequence data are deposited in the GenBank under the accession numbers:
AJ270956 (mo5-3C11/1), AJ270957 (mo5-3G12/4), AJ270958 (mo5-3G17),
AJ270959 (mo5-3T12), AJ270960 (mo1-6A1), AJ270961 (mo1-6T1), AJ270962
(mo5-10G1), AJ270963 (mo6-20G1), AJ270964 (mo6-MGT2) and AJ243875 (LeRAD23-8
full-length cDNA).
Reduced cellular cross-sectional area in the leaf elongation zone of wheat causes a decrease in dry weight deposition under saline conditions
Authors: Hu Yuncai , Schmidhalter Urs
Published: September 2002

Expansion and dry weight (DW) of wheat leaves are spatially distributed along
the axis and affected by salinity. The objective of this study was to evaluate
the effect of salinity on the spatial distribution of cellular cross-sectional
area and DW in the elongating and mature leaf zones of leaf 4 of the main stem
of spring wheat (Triticum aestivum L. cv. Lona) during
its linear growth phase. Plants were grown in illitic–chloritic silt
loam with 0 and 120 mM NaCl in a growth chamber. Cellular cross-sectional area
and DW contents of leaves were determined on the 5–20-mm scale along the
leaf axis. Spatial distribution of cellular cross-sectional area changed
slightly with distance within the elongation zone in both treatments. The
cellular cross-sectional area of the leaf at 120 mM NaCl was reduced by
32% at 5 mm, as compared with about 36% averaged from the region
between 5 and 30 mm from the leaf base, indicating that the reduction in the
cellular cross-sectional area by salinity occurred mainly at the leaf base
when the leaf initiates. A slight decrease in the DW per leaf length at a
given location in the elongation zone may be due to the strongly decreased
cellular cross-sectional area by salinity. This suggests that the limitation
of leaf growth by salinity may be due mainly to the effect of salinity on leaf
expansion, but not due to the effect on the synthesis of dry matter.
Agrobacterium tumefaciens-mediated transformation of an elite Australian barley cultivar with virus resistance and reporter genes
Authors: Wang Ming-Bo , Abbott David C. , Upadhyaya Narayana M. , Jacobsen John V. , Waterhouse Peter M.
Published: September 2002

Efficient transformation of barley cv. Schooner was achieved using
Agrobacterium delivery, hygromycin or bialaphos
selection and embryogenic callus. Using this system, transgenic plants were
generated that contained either the green fluorescent protein gene, or
transgenes derived from barley yellow dwarf (BYDV) and cereal yellow dwarf
(CYDV) viruses. Many of these plants contained 1–3 transgene copies
that were inherited in a simple Mendelian manner. Some plants containing BYDV
and/or CYDV derived transgenes showed reduced virus symptoms and rates of
viral replication when challenged with the appropriate virus. The ability to
transform Schooner is a significant advance for the Australian barley
industry, as this elite malting variety is, and has for the last 15 years
been, the most widely grown barley variety in eastern Australia.
Temporal variation of tannins (galloylglucoses), flavonols and anthocyanins in leaves of Eucalyptus nitens seedlings: implications for light attenuation and antioxidant activities
Authors: Close Dugald C. , Davies Noel W. , Beadle Chris L.
Published: September 2002

Leaves of Eucalyptus nitens (Deane & Maiden) Maidenwere sampled during establishment of seedlings that were deprived of nutrientsor fertilised at planting. Extracts were analysed for polyphenolic compoundsusing high pressure liquid chromatography (HPLC) in conjunction with UV diodearray and electrospray ionisation mass spectrometry (ESI-MS) with negative iondetection as well as direct MS injection. The presence of quercetin, rutin,sideroxylonal A and B andpenta-galloylglucose were confirmed by comparison with standards. Othergalloylglucoses were identified by first principles. Galloylglucoses comprisedabout 75% of polyphenolics. Quercetin and various quercetin glycosidescomprised ca 85% of flavonols. The anthocyanins,cyanidin-3-glycoside and cyanidin-3,5-diglycoside were identified from directinjection MS data. HPLC–ESI-MS was found to be a superior analyticaltechnique compared to conventional HPLC–UV diode array detection due toco-elution of peaks under UV. Temporal variation of anthocyanins may berelated to the severity of cold-induced photoinhibition. Changes ingalloylglucoses and flavonols were similar with time and related to levels offoliar nitrogen. The suitability of HPLC–ESI-MS for the study of foliarpolyphenolics, the phenolic constitution of E. nitensfoliage, and temporal variation of the phenolic constituents during a seedlingestablishment period of 29 weeks are demonstrated.
Membrane transport activity and ultradian ion flux oscillations associated with cell cycle of Thraustochytrium sp.
Authors: Shabala Lana , Shabala Sergey , Ross Tom , McMeekin Tom
Published: September 2002

Membrane transport activity associated with growth and nutritional status of a
marine microheterotroph Thraustochytrium sp. was studied
using non-invasive ion-selective slowly vibrating microelectrodes (the MIFE
technique). Net fluxes of H + , Ca
2+ and Na + underwent
regular changes as the cell progressed from the zoospore to sporangium stages
of development. The most pronounced change was a decrease in the net H
+ influx, which we suggest could be associated with
the changes in cytoskeletal organization required for cell cleavage and
zoospore release. As cell development progressed from the zoospore stage
towards maturity, non-damping endogenous ultradian oscillations (period range
of several minutes) became evident. At the sporangium stage, as many as
85% of cells possessed oscillatory membrane transport activity. It is
suggested that ultradian ion flux oscillations in
Thraustochytrium sp. may be causally linked with cell
developmental processes. Discrete Fourier transform and cross-correlation
analysis revealed a close association between oscillatory patterns of H
+ and Na + fluxes. The
possibility that these oscillations result from the rhythmical activity of a
Na + /H +
co-transporter located at the plasma membrane of
Thraustochytrium sp. is considered. Oscillations in net
Ca 2+ flux were apparently not linked to those in
H+ and Na + , and are
believed to be due to some other physiological processes. Periods of net H
+ and Na + flux
oscillations were strongly dependent on the external Na
+ concentrations in the bathing medium. As sodium
is considered to be an essential element in
Thraustochytrium sp., it is suggested that the
functional role of such ultradian oscillations may be their involvement in the
frequency-encoding mechanism that provides developing cells with information
about environment, and nutritional status in particular.
Effects of manipulation of pyruvate decarboxylase and alcohol dehydrogenase levels on the submergence tolerance of rice
Authors: Rahman Musrur , Grover Anil , Peacock W. James , Dennis Elizabeth S. , Ellis Marc H.
Published: September 2002

A transgenic approach was taken to manipulate the levels of pyruvate
decarboxylase (PDC) and alcohol dehydrogenase (ADH) in rice, in order to
investigate whether alteration of ethanol fermentation can affect anaerobic
tolerance. A line transformed with an antisense Adh1
construct had only 4–8% of the ADH activity of untransformed
plants. This line showed reduced ethanol production and coleoptile growth
under anoxia. Mature plants had reduced survival when submerged in water and
exposed to anoxia, suggesting that ADH plays an essential role in seed
germination and plant survival in the absence of O2. A transgenic line
transformed with a cotton Adh2 cDNA in the sense
orientation relative to a constitutive promoter, showed 3–4-fold more
ADH activity than either untransformed controls, or a flooding-tolerant rice
variety (FR13A), both in air and under hypoxia. However, ethanol production by
this line was only slightly higher than that of untransformed controls, and
there was no increase in survival following anoxia treatments.
Three independent transgenic lines containing the
ricePdc1 cDNA driven by an anaerobically-inducible
promoter (6XARE) showed an increase in PDC1 polypeptide
in shoots, but not in roots or endosperm. A moderate increase in PDC activity
and ethanol production was observed in shoots of these lines under anaerobic
conditions, as well as decreased survival of shoots when submerged and exposed
to anoxia. F1 plants containing both the PDC and ADH constructs showed levels
of anoxia-tolerance similar to those of untransformed plants. These results
suggest that over-production of PDC may be toxic to rice plants because of
increased acetaldehyde. Consistent with this view, acetaldehyde levels were
appreciably higher in plants over-producing PDC, compared with untransformed
plants, or hybrid lines containing both the PDC and ADH constructs.
Drought survival and dehydration tolerance in Dactylis glomerata and Poa bulbosa
Authors: Volaire Florence , Conéjero Geneviève , Lelièvre François
Published: September 2002

To analyse the contribution of dormancy and dehydration tolerance to drought
survival of perennial grasses, we compared Poa bulbosa
L., which is classified as a resurrection plant, with one of the most drought
resistant cultivars of MediterraneanDactylis glomerata
L. Comparing periods when dormancy was induced in Poa
(summer) and not induced (winter), we aimed to ascertain the presence of
differential plant responses between dormancy and dehydration tolerance and to
characterise water status, sugar and dehydrin accumulation in surviving organs
of Poa and Dactylis, in relation
to their ability to survive intense drought. Irrespective of the dormancy
status of Poa, the bulbs of this species had a final
water content lower than 10% and survived an extreme drought. This
could be associated with the accumulation of sucrose and the expression of a
high number (>10) of dehydrins that peaked when the water content of
the bulbs fell below 50%, whether this dehydration was due to
dormancy induction or increasing soil water deficit. The independence of
dormancy to dehydration tolerance was reinforced by the expression of a
specific dehydrin (approx. 28 kDa) found only in irrigated, but dormant,
tissues of Poa. The Dactylis
exhibited contrasting survival between experiments (46 and 0% after
a summer and winter drought, respectively). The mortality was associated with
a significantly higher rate of decrease of the membrane stability of leaf
bases of Dactylis in winter and with barely detectable
amounts of sucrose contents in droughted roots. However, neither the
water-soluble carbohydrate concentration in leaf bases nor the overall
accumulation of dehydrins could be related to the contrasting survival of this
Dactylis between the two seasons. Since in seeds of
Poa and Dactylis, the accumulation
of dehydrins was comparable with that found in droughted aerial tissues of the
same species, the expression of these proteins must interact with other
mechanisms to confer dehydration tolerance.
How characean cells have contributed to the progress of plant membrane biophysics
Authors: Tazawa Masashi , Shimmen Teruo
Published: September 2002

Basic knowledge on plant membranes has been greatly indebted to internodal
cells of charophytes, which are aquatic cryptogams mostly growing in fresh
water and some in brackish water. The huge size of the internodal cell enables
us to study water and ion transport in a single cell. Furthermore, the cell
can be subjected to various kinds of cell operations such as preparation of
cells having abnormal osmotic pressures, effusion of the steaming endoplasm,
perfusion of the vacuole with artificial solutions, preparation of
tonoplast-free cells and plasma membrane-permeabilised cells. Taking advantage
of the large cell size and the cell operation techniques, various aspects of
characterisations of plant membranes (plasma membrane, tonoplast,
endomembranes) have been achieved using characean cells. The present article
intends to depict unique contributions of characean cells to membrane
physiology and biophysics in the last century, focusing on several topics and
with historical perspectives.
Enhanced maize productivity by inoculation with diazotrophic bacteria
Authors: Riggs Patrick J. , Chelius Marisa K. , Iniguez A. Leonardo , Kaeppler Shawn M. , Triplett Eric W.
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
The objective of this work over the last 3 years was to identify
maize–endophyte associations with increased plant productivity compared
with uninoculated controls. We have used a collection of endophytes isolated
by several groups. The experiments were done under field and greenhouse
conditions in the presence or absence of added fixed nitrogen (N). Significant
yield enhancements of N-fertilized maize were obtained with bacterial
endophytes that we have isolated from N-efficient lines of maize (such as
Klebsiella pneumoniae 342) or switchgrass
(Pantoea agglomerans P101 and P102). Several other
strains from other groups were also tested with our best yield enhancements
from two Brazilian strains,
Gluconacetobacter diazotrophicus PAl5
andHerbaspirillum seropedicae Z152. Field experiments in
Wisconsin were conducted in 1998, 1999 and 2000 and in an additional four
states (Illinois, Iowa, Indiana and Nebraska) in 2000, with a minimum of two
elite lines of maize at each site, each year. No strains were capable of
relieving the N-deficiency symptoms of unfertilized maize in either the field
or the greenhouse.
Denitrification within the genus Azospirillum and other associative bacteria
Authors: Kloos Karin , Mergel Alexander , Rösch Christopher , Bothe Hermann
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
Different Azospirillumstrains and some other plant
growth-promoting rhizobacteria (PGPR) were screened for the occurrence of
genes coding for denitrification and nitrogenase reductase
(nifH) using polymerase chain reaction (PCR)-based
techniques. All PGPR examined were nitrogenase-positive.
Azospirillum strains were remarkably dissimilar with
respect to denitrification capabilities, in particular with respect to genes
of the dissimilatory nitrite reductase. A. brasilense,
A. lipoferum and A. halopraeferens
strains possess a cytochrome
cd1-containing nitrite reductase
with low sequence similarities among them. A. irakense
and A. doebereinerae have a Cu-containing nitrite
reductase and A. amazonense is unable to denitrify. The
molecular data were corroborated by activity measurements. The current results
indicate that the inability to perform denitrification is unlikely a selective
advantage for Azospirillum spp. and other associative
bacteria for forming an association with plant roots.
Niches for bacterial endophytes in crop plants: a plant biologist's view
Authors: McCully Margaret E.
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
Currently proposed means of entry of bacterial endophytes into roots of
field-grown crop plants, as well as niches available for their successful
colonization of living tissues, are evaluated from a plant biology perspective
and the following conclusions drawn. (1) Opportunities for passive
‘crack entry’ into healthy, undisturbed roots in the field may not
be as available as studies with laboratory-grown plants have suggested.
Consistent entry of endophytes into living root tissues in the field probably
requires bacterial capability to hydrolyse the hydrophobic incrustations of
the walls of epidermal, hypodermal, endodermal and other cortical cells. (2)
Xylem lumen apoplast is an unsuitable niche for endophytes, especially in the
grasses, because of the reduced fitness such colonization imposes on plants
subjected to field stresses. (3) The intercellular space apoplast is the most
suitable niche for endophytes. More data about the environment of this
apoplast are urgently needed so that plant varieties can be tailored to
provide an optimal environment in these spaces for particular endophytes. It
is suggested that many bacterial ‘endophytes’ may not have
colonized living tissues, but are living in protective niches in dead surface
tissues or closely adhering soil of rhizosheaths. Selection of strains of
beneficial bacteria adapted for colonizing these external niches may be
desirable.
Impact of solar UV-B radiation on seedling emergence, chlorophyll fluorescence, and growth and yield of radish (Raphanus sativus)
Authors: Zavala Jorge Alberto , Botto Javier Francisco
Published: September 2002

We report the impact of present-day solar UV-B radiation on seedling emergence, its association with the accumulation of UV-absorbing compounds, and the growth and yield of radish (Raphanus sativus L.). Two field experiments were conducted at intermediate latitudes in South America (Buenos Aires, Argentina) using two cultivars of radish (`Scarlet Globe' and `Sparkler National'). Solar UV-B reduced the emergence of seedlings by nearly 20% for the Scarlet radish cultivar, and delayed emergence for both cultivars by least one day. Using a chlorophyll fluorescence method to estimate the degree of UV penetration into photosynthetic tissue, we found significant differences in the levels of UV-B-absorbing compounds between seedlings grown under contrasting levels of solar UV-B. The increase of specific UV-absorbing compounds in the cotyledons required an initial lag period of 4 d after the emergence of seedlings. We could not detect any relationship between the accumulation of UV-B-screening compounds in cotyledons and leaves of the same plant, suggesting that solar UV-B induced a localized response in green tissues. Ambient UV-B affected the biomass partitioned to tubers, resulting in an increase of at least 17% in tuber diameter and 26% in tuber fresh weight at the end of the life cycle. Our results indicate that the early effects of UV-B on seedling development involve a cost for young plants, but it appears to be advantageous to increase the carbon partitioning to the tubers at harvest. These findings suggest ways to improve the yield of radish crops.
Photoinactivation and recovery of photosystem II in Chenopodium album leaves grown at different levels of irradiance and nitrogen availability
Authors: Kato Masaharu C. , Hikosaka Kouki , Hirose Tadaki
Published: September 2002

Involvement of photosynthetic capacity and D1 protein turnover in the susceptibility of photosystem II (PSII) to photoinhibition was investigated in leaves of Chenopodium album L. grown at different combinations of irradiance and nitrogen availability: low light and high nitrogen (LL-HN); high light and low nitrogen (HL-LN); and high light and high nitrogen (HL-HN). To test the importance of photosynthetic capacity in the susceptibility to photoinhibition, we adjusted growth conditions so that HL-HN plants had the highest photosynthetic capacity, while that of LL-HN and HL-LN plants was lower but similar to each other. Photoinhibition refers here to net inactivation of PSII determined by the balance between gross inactivation (photoinactivation) and concurrent recovery of PSII via D1 protein turnover. Leaves were illuminated both in the presence and absence of lincomycin, an inhibitor of chloroplast-encoded protein synthesis. Susceptibility to photoinhibition was much higher in plants grown in low light (LL-HN) than those grown in high light (HL-HN and HL-LN). Susceptibility to photoinhibition was similar in HL-LN and HL-HN plants, suggesting that higher photosynthetic energy consumption alone did not mitigate photoinhibition. Experiments with and without lincomycin showed that high-light-grown plants had a lower rate of photoinactivation and a higher rate of concurrent recovery, and that these rates were not influenced by nitrogen availability. These results indicate that turnover of D1 protein plays a crucial role in photoprotection in high-light-grown plants, irrespective of nitrogen availability. For low-nitrogen-grown plants, higher light energy dissipation by other mechanisms may have compensated for lower energy utilization by photosynthesis.
Functionally distinct NAD(P)H dehydrogenases and their membrane localization in Synechocystis sp. PCC6803
Authors: Ohkawa Hiroshi , Sonoda Masatoshi , Hagino Natsu , Shibata Mari , Pakrasi Himadri B. , Ogawa Teruo
Published: September 2002

The type I NAD(P)H dehydrogenase complex (NDH-1) in cyanobacteria is involved
in both respiratory and photosynthetic electron transport processes. NDH-1 is
also essential for inorganic carbon transport. It has been postulated that
NDH-1-dependent cyclic electron flow around PSI energizes
CO2 uptake. The genome information of
Synechocystis sp. PCC6803 has enabled us to provide an
integrative view of the CO2 concentrating mechanism in
this organism. In an attempt to dissect the role of the NDH-1 complex, we have
constructed single and double mutants of Synechocystis
6803 by disrupting highly homologous ndhD genes in pairs,
and have analysed the growth, CO2 uptake activities, and
redox levels of P700 and the plastoquinone pool in these mutants under various
conditions. We have also determined the membrane localization of this membrane
protein. Our studies have revealed that: (i) mutations in
ndh genes lead to inhibition of
CO2 uptake, rather than HCO3– uptake; (ii) NDH-1 complexes are localized only
in the thylakoid membrane; (iii) there are functionally distinct NDH-1
complexes in Synechocystis #6803. Based on these data, we
propose a schematic view of the roles of different NDH-1 complexes in
cyanobacteria.
Inorganic carbon utilization in marine angiosperms (seagrasses)
Authors: Beer Sven , Bjork Mats , Hellblom Frida , Axelsson Lennart
Published: September 2002

The mechanisms by which marine angiosperms, or seagrasses, utilize external
inorganic carbon (Ci) include, in addition to uptake of
CO2 formed spontaneously from
HCO3–: (i) extracellular
carbonic anhydrasemediated conversion of
HCO3– to
CO2 at normal seawater pH, or in acid zones created by
H+ extrusion, and (ii)
H+-driven utilization (direct uptake?) of
HCO3–. The latter mechanism
was recently indicated for Zostera marina,
Halophila stipulaceaand
Ruppia maritima, and manifested itself as a sensitivity
of photosynthesis to buffers, as well as a relative insensitivity to
acetazolamide under buffer-free conditions, especially at high pH.
Seagrasses have until recently been viewed as having Ci utilization systems
that are less ‘efficient’ than macroalgae, and this has, for
example, led to the thought that future rises in atmospheric and thus
dissolved CO2 would have a stronger effect on seagrasses
than on macroalgae. However, most of the experiments leading to such
conclusions were carried out in the laboratory on detached leaves, and buffers
were used to keep
HCO3–/CO2
ratios stable during Ci additions. The revelation that seagrass photosynthesis
is sensitive to buffers as well as to physical perturbations, has led to new
experiments in which initial pH values are set by appropriate
HCO3–/CO32–ratios,
and/or O2 measurements on leaf pieces are replaced
with pulse amplitude-modulated fluorometry on whole, attached leaves, often
in situ. Under such conditions, the photosynthetic
responses of seagrasses to Ci match those obtained for macroalgae. Thus, the
paradigm of ‘inefficient’ Ci utilization by seagrasses as compared
with macroalgae may no longer be valid. Consequently, it seems that the
generally observed high productivity of seagrass beds may have its background
in very efficient, H+-driven, means of
HCO3– utilization.
Analysis of Chlamydomonas mutants with abnormal expression of CO2 and HCO3- uptake systems
Authors: Thyssen Christoph , van Hunnik Eddy , Navarro Marie Teresa , Fernández Emilio , Galván Aurora , Sültemeyer Dieter
Published: September 2002

Eukaryotic microalgae such as
Chlamydomonas reinhardtii possess an inducible
CO2 concentrating mechanism that operates as a very
close interaction between pyrenoid-based Rubisco, various carbonic anhydrases
(CAs), and inorganic carbon (Ci) transport systems. While external and
internal CAs have been characterised to the molecular level, the biochemistry
and molecular biology of Ci uptake mechanisms have not been elucidated. Both
Ci species, CO2 and
HCO3-, are taken up by the cells
and chloroplasts during steady-state photosynthesis. After acclimation to
limiting Ci, CO2 and
HCO3- transport, measured in whole
cells or chloroplasts, change their kinetic characteristics from a
constitutive low-affinity state to an inducible high-affinity state. In order
to learn more about the genes involved in the signal transduction pathway and
in the Ci transport systems, we performed insertional mutagenesis using the
arg7 gene as a selectable marker. Application of aqueous
membrane inlet mass spectrometry allowed discrimination between
CO2 and
HCO3- uptake. Data is presented on
two mutants, M46 and M21, which show severe damage to the constitutive Ci
uptake systems and which are unable to induce a high-affinity state. The
mutations might be either in the signal transduction pathway or in the
transporters themselves. In addition, we present data that shows a very close
connection between high-affinity
HCO3- uptake and high-affinity
NO3- uptake in cells of
C. reinhardtii.
Dinoflagellate symbioses: strategies and adaptations for the acquisition and fixation of inorganic carbon
Authors: Leggat William , Marendy Elessa M. , Baillie Brett , Whitney Spencer M. , Ludwig Martha , Badger Murray R. , Yellowlees David
Published: September 2002

Dinoflagellates exist in symbiosis with a number of marine invertebrates
including giant clams, which are the largest of these symbiotic organisms. The
dinoflagellates (Symbiodinium sp.) live intercellularly
within tubules in the mantle of the host clam. The transport of inorganic
carbon (Ci) from seawater to Symbiodinium
(=zooxanthellae) is an essential function of hosts that derive the
majority of their respiratory energy from the photosynthate exported by the
zooxanthellae. Immunolocalisation studies show that the host has adapted its
physiology to acquire, rather than remove CO2, from the
haemolymph and clam tissues. Two carbonic anhydrase (CA) isoforms (32 and 70
kDa) play an essential part in this process. These have been localised to the
mantle and gill tissues where they catalyse the interconversion of
HCO3- to
CO2, which then diffuses into the host tissues. The
zooxanthellae exhibit a number of strategies to maximise Ci acquisition and
utilisation. This is necessary as they express a form II Rubisco that has poor
discrimination between CO2 and O2.
Evidence is presented for a carbon concentrating mechanism (CCM) to overcome
this disadvantage. The CCM incorporates the presence of a light-activated CA
activity, a capacity to take up both
HCO3-and
CO2, an ability to accumulate an elevated concentration
of Ci within the algal cell, and localisation of Rubisco to the pyrenoid.
These algae also express both external and intracellular CAs, with the
intracellular isoforms being localised to the thylakoid lumen and pyrenoid.
These results have been incorporated into a model that explains the transport
of Ci from seawater through the clam to the zooxanthellae.
Structure, function and regulation of the cyanobacterial high-affinity bicarbonate transporter, BCT1
Authors: Omata Tatsuo , Takahashi Yukari , Yamaguchi Osamu , Nishimura Takashi
Published: September 2002

The cmpABCD operon of the cyanobacterium
Synechococcus sp. strain PCC7942, which is transcribed
specifically under CO2-limited growth conditions,
encodes an ATP-binding cassette (ABC) transporter involved in
HCO3–uptake (designated BCT1). The
product of the cmpA gene is a 42-kDa protein anchored to
the plasma membrane, which binds
HCO3– with high affinity
(Kd= 5 µM) and acts as the
substrate-binding protein of the transporter. The apparent
Km(HCO3–)
of BCT1 is 15 µM. BCT1 has the highest affinity for
HCO3– among the
HCO3– transporters of the
Synechococcus strain and is essential for competitive
utilization of HCO3– under
CO2-limited conditions. BCT1 is closely related to the
cyanobacterial nitrate/nitrite transporter (NRT) encoded by the
nrtABCD genes. The BCT1 and NRT transporters, together
with the putative cyanate transporter of cyanobacteria, comprise a monoanion
transporter subfamily in the family of ABC importers. BCT1 and NRT are present
in most fresh-water strains of cyanobacteria but seem to be absent in marine
cyanobacterial strains. The low CO2-responsive induction
of thecmp operon requires a LysR family protein CmpR,
which is similar to CbbR (RbcR), the activator of the
CO2 fixation operons of chemoautotrophic and purple
photosynthetic bacteria.
Seasonal changes in tissue elasticity and water transport efficiency in three co-occurring Mediterranean shrubs under natural long-term CO2 enrichment
Authors: Tognetti Roberto , Raschi Antonio , Jones Mike B.
Published: September 2002

Seasonal changes in hydraulic properties and tissue elasticity were evaluated in Erica arborea L., Myrtus�communis L. and Juniperus communis L., three Mediterranean shrubs that differ in adaptations to drought. These parameters were analysed over 12 months under field conditions, by comparing plants grown in the proximity of a natural CO2 spring (about 700 μmol mol–1 atmospheric CO2 concentration, [CO2]) with plants in ambient conditions. Plants at the CO2-spring site have been growing for generations at elevated [CO2]. At both sites, stem hydraulic and structural properties followed the prevailing climatic constraints. However, these shrub species co-occurring in the same environment differed in their capacity to tolerate water deficits, in xylem efficiency, and in strategies for regulating water movement between plant compartments. Either an increase or a decrease in tissue elasticity was effective in promoting resistance to drought stress, depending on the species. Long-term elevated [CO2] influenced all the studied parameters. Species-dependent differences existed in hydraulic architecture between the CO2-spring plants and control plants of E. arborea and M. communis, while J. communis plants rarely showed differences between sites. Less distinct differences between sites were observed for wood structure. The three species showed somewhat lower tissue elasticity under elevated [CO2], in particular during stress periods. The effects of elevated [CO2] on stem hydraulic pathway and structure and shoot elastic properties persist in the long term, but differ in absolute values and sign among the studied species and with the seasonal course, and thus might alter competitive relations between these shrubs.
The complexity of oxidative cross-linking of phenylpropanoids — evidence from an in vitro model system
Authors: Stobiecki Maciej , Buśko Maciej , Marczak Łukasz , Bednarek Paweł , Piślewska Mariola , Wojtaszek Przemysław
Published: September 2002

The development of an in vitro model system to study the process of dimerization of hydroxycinnamic acids is reported. Model compounds ferulic acid (FA) or methyl ferulate were reacted with H2O2 in the presence of horseradish peroxidase (HRP) or peroxidases from Lupinus albus L. apoplastic fluids. Following solid-phase extraction, the reaction products were analysed using gas chromatography-mass spectrometry. Major analytical and biochemical parameters of model reactions were determined and optimized. Six ferulic dimers were identified and quantified.
With the use of this model system we found methyl ferulate to be a better substrate for lupin and horseradish peroxidases than FA. Use of various peroxidases did not influence the qualitative composition of reaction products although it affected the rate of substrate utilization and the quantitative output of reactions. Various isoforms of lupin apoplastic peroxidases revealed differentiated specificity towards hydroxycinnamic acids or their methyl esters. The potential of isoflavonoids (major phenolic components in white lupin cell walls) to influence peroxidase-catalysed formation of ferulic dehydrodimers was also tested. Genistein (5,7,4'-trihydroxyisoflavone) and genistin (genistein-7-O-β-glucoside) did not affect the qualitative composition of the reaction products. However, genistein inhibited the rate of ferulic substrate oxidation, while genistin showed the opposite effect, stimulating both utilization of ferulic substrate by HRP and subsequent polymerization and / or degradation of dehydrodimers formed. To our knowledge, this is the first indirect evidence that isoflavonoids might play a regulatory role in the oxidative formation of intermolecular cross-links in cell walls.
Oxygen isotope ratio of leaf and grain material correlates with stomatal conductance and grain yield in irrigated wheat
Authors: Barbour Margaret M. , Fischer R. Anthony , Sayre Ken D. , Farquhar Graham D.
Published: September 2002

Theory (Craig and Gordon 1965; Dongmann
et al. 1974; Sternberg et al.
1986; Farquhar and Lloyd 1993) suggests that the oxygen isotope ratio (d
18 O) of plant material should reflect the evaporative
conditions under which the material was formed, so that differences in
stomatal conductance should show up in plant d 18 O. To
test this theory we measured the oxygen isotope ratio of organic matter from
flag leaves at anthesis and grain at harvest from eight cultivars of spring
wheat (Triticum aestivum L.) grown under irrigation in
each of three seasons in Mexico. The cultivars ranged widely in stomatal
conductance and in average grain yield, with which conductance was positively
correlated. Supporting theory, the oxygen isotope ratio of flag leaves (d
18 Ol) was found to correlate
negatively with stomatal conductance for two of the three seasons. The
significant correlations are consistent with high conductance cultivars having
lower leaf temperatures and kinetic fractionation factors, and higher vapour
pressure fractionation factors and Péclet numbers, all of which combine
to result in less enriched d 18
Ol. Yield (grain weight per square meter) was also found
to be significantly negatively correlated with d
18Ol in two of the three seasons.
d 18 Ol was as good a predictor of
yield as stomatal conductance, and significantly better than carbon isotope
discrimination. Correlations between grain d 18 O (d
18 Og) and physiological
parameters were less clear. Significant negative correlations between d
18 Og and stomatal conductance,
leaf temperature and yield were found only during the first season. By
measuring the oxygen isotope ratio of cellulose extracted from leaf samples,
the difference in fractionation factors (ecp) for
cellulose and whole leaf tissue was assessed. ecp was
found to be variable, and more negative when d 18
Oc and d 18
Ol were lower. Cultivar means for d
13 C and d 18 O of whole leaf
material were found to be significantly positively related, and the factors
required to produce such a relationship are discussed.
Surprising implications of the optimality hypothesis of stomatal regulation gain support in a field test
Authors: Hari Pertti , Mäkelä Annikki , Pohja Toivo
Published: September 2002

Our previous reformulation of Cowan and Farquhar’s optimality hypothesis
of stomatal reg-ulation has resulted in models for photosynthesis and
transpiration which have been readily testable against field data. When
analysing the water use efficiency implied by our previous reformulation of
the optimality hypothesis of stomatal regulation, we discovered an unexpected
property: when stomatal reg-ulation is active, a linear relationship could be
found between transpiration and a term involving water vapour deficit and
photosynthesis. This prediction gives rise to a novel test which requires no
parameter estimation. We conducted such a test in Scots pine, utilising
ca 10 000 measurements of CO2
exchange, transpiration, temperature, PAR, and water vapour concentration,
taken at the SMEAR I measuring station in Finnish Lapland. As predicted, on
clear and sunny days the correlation coefficient of the linear relationship
was as high as 0.99, corroborating our formulation of the optimality
hypothesis.
Relationship between the suppression of photosynthesis and starch accumulation in the pod-removed bean
Authors: Nakano Hiromi , Muramatsu Shinichi , Makino Amane , Mae Tadahiko
Published: September 2002

Effects of pod removal on the photosynthetic rates and their under lying
biochemical properties were examined in leaves of bean
(Phaseolus vulgaris L.). Pod removal led to decreases in
the photosynthetic gas- exchange rate, stomatal conductance and intercellular
CO2 pressure. H owever, these decreases in
photosynthesis were not asso-ciated with changes in the amounts of
ribulose-1,5-bisphosphate carb oxylase (Rubisco) and other several
photo-synthetic components, but were associated with an increase in starch
content. In addition, such a decrease in the photosynthetic rate was not
observed when measured with O2 evolution under
conditions of saturating CO2. Similarly, although a
decrease in CO2-limited photosynthesis for a given
Rubisco content was found in depodded plants, neither the speci fic activity
nor activation state of Rubisco decreased . The decrease in the photosynthetic
gas-exchange rate by pod removal was rec overed by shading the plants.
CO2-limited photosynthesis per unit of Rubisco protein
was also completely recovered at the same l evel in the plants with pods. At
the same time, starch accumu-lation was also decreased by shading. From these
results, we concluded that the suppression of photosynthesis observed in
depodded beans was caused by the hindrance of CO2
diffusion due to starch accumulated in the chloroplast.