bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Water Stress on Enzyme Activities in Wheat and Related Wild Species: Carboxylase Activity, Electron Transport and Photophosphorylation in Isolated Chloroplasts
Authors: Mayoral ML , Atsmon D , Shimshi D , Gromet-Elhanan Z
Published: January 2006

Drought sensitivity of Triticum aestivum (cv. Sion) and two wild related species, T. longissimum and T. kotschyi was assessed by measuring the activity of ribulose-1,5-bisphosphate carboxylase (RuP2 carboxylase) and phosphoenolpyruvate carboxylase (PEP carboxylase), determination of total leaf soluble protein and chlorophyll content and by measuring the rates of electron transport and photophosphorylation in isolated chloroplasts. T. aestivum and T. longissimum showed relatively high drought sensitivity. The activity of the two carboxylating enzymes as well as chlorophyll and protein contents decreased with decreasing leaf water potential (Ψ). Rates of electron transport and photophosphorylation in isolated chloroplasts declined as soon as the Ψ value was reduced from - 0.8 MPa to - 1.0 MPa. In T. kotschyi, all the above activities remained stable down to a � value of about - 2 MPa. These results point to a clear correlation between the ability of T. kotschyi to grow in arid areas and its better performance in all the tests carried out under controlled water stress. In T. kotschyi an initial increase in PEP carboxylase activity was detected between Ψ values of -0.8 MPa and -2.1 MPa, followed by a sharp decline. No uncoupling of the chloroplasts by water stress was observed in any of the three species.
Effects of water stress and rewatering on turnover and gene expression of photosystem II reaction center polypeptide D1 in Zea mays
Authors: Hao Limin , Liang Houguo , Wang Zongling , Liu Xinmin
Published: January 2006

Photosystem II oxygen evolution capacity, the steady-state level of
photosystem II (PSII) reaction center polypeptide D1 and its transcript and
template levels inZea mays L. (Xinyu No. 4) under water
stress and rewatering were studied. The results indicated that PSII and
whole-chain electron transport capacities decreased slightly under moderate
water stress and appreciably under severe water stress, and could not recover
to control level upon rewatering. The results of western and northern blots
showed that the content of PSII reaction center polypeptide D1 changed as a
similar pattern to PSII and whole-chain electron transport capacities. Dot
blot analysis for DNA showed that there was no obvious response of the
template level of D1 to water stress or rewatering. From the results, it was
concluded that PSII was the major site affected by water stress, where the
functional loss of PSII could be attributed to the reduction of PSII reaction
center polypeptide D1, which may be caused by the decrease in its transcript
level. Rewatering could only ameliorate slightly under moderate water stress
but could not recover to control level under severe water stress.
Chemistry and Organization of Aleurone Cell Wall Components From Wheat and Barley
Authors: Bacic A , Stone BA
Published: January 2006

Methylation analysis and hydrolysis with specific enzymes indicates that aleurone cell wall preparations from wheat (Triticum aestivum cv. Insignia) and barley (Hordeum vulgare cv. Clipper) are composed of two main types of polysaccharides, heteroxylans and 1,3;1,4-β-glucans. Small amounts of glucomannan and cellulose are also present. Approximately 1% of a 1,3-β-glucan was also detected in the wall preparations using a specific 1,3-β-glucan exohydrolase. This material probably corresponds to the aniline blue-fluorescent deposits seen at the aleurone-endosperm interface. As isolated, the aleurone wall preparations are associated with protein, 10.5% in wheat and 16.0% in barley. Electron microscopic examination and amino acid analyses indicated that a major part of this protein arises from cytoplasmic protein deposited on the walls during isolation in organic solvents. Fractionation of the walls by conventional procedures showed that the heteroxylan and 1,3 ;1,4-β-glucan components were extracted by water, 8 M urea and alkaline solvents. Their differential solubility is discussed in terms of their structural organization and possible covalent interactions between polymers. Transmission electron microscopy of the walls at each stage of fractionation showed that the bilayered organization was retained after water and 8 M urea extraction but was lost following extraction in alkaline media.
Effect of Constant Temperature Treatments Followed by Fluctuating Temperatures on the Softening of Hard Seeds of Trifolium subterraneum L
Authors: Taylor GB
Published: January 2006

Three experiments are described in which the effects of constant temperatures ranging from 15 to 80°C, followed by diurnally fluctuating temperatures of 60/15°C were compared on seed softening in three cultivars of T. subterraneum. Constant temperature treatments alone produced relatively few soft seeds, but rapid seed softening ensued within a few days of subsequent fluctuating temperature treatment. The higher and the longer the constant temperature pretreatment, the more soft seeds were obtained. The rate at which this preconditioning of the seed took place was highest in the early stages of exposure to constant temperatures. Differences between cultivars and between temperature treatments were established mainly during this early period of constant temperature treatment. Rates of change of temperature in the 60/15°C fluctuation treatment were important in the final seed softening process: the slower the rate of temperature change the more soft seeds were produced.
It is suggested that two distinct temperature dependent processes are involved in seed softening. The first appears to be a thermal degradation process which probably results in weakening of the strophiolar region. Fluctuating temperatures bring about the second stage of softening in which the strophiole is rendered permeable to water.
Hormonal Physiology of Wood Growth in Pinus radiata D. Don: Effects of Gibberellin A4 and the Influence of Abscisic Acid Upon (3H) Gibberellin A4 Metabolism
Authors: Pharis RP , Jenkins PA , Aoki H , Sassa T
Published: January 2006

Xylem cell radial growth of 1-year-old seedlings of P. radiata was significantly increased by application of gibberellin A4 (GA4), or of abscisic acid (ABA) plus a smaller, and non-significant, dosage of GA4. In 10 out of 15 additional tests throughout the growing season, ABA tended to increase radial growth, and only once (in mid-summer) did ABA significantly reduce xylem cell radial growth. Seedlings were grown under well watered, warm, long-day conditions. Where GA4 (22 �g) or ABA (20 �g) plus GA4 (2 �g) increased xylem cell radial growth, the metabolism of [3H]GA4 was followed. Although not characterized from P. radiata, GA4 is native to P. attenuata, a species which will hybridize with P. radiata. At low levels (2 �g) of carrier GA4, [3H]GA4 metabolism was rapid, and ABA (20 �g) enhanced metabolism, especially into acidic metabolites. One metabolite was definitively characterized as GA34 and other metabolites eluted in regions of a SiO2 partition column coincidental with GA1, GA2, GAB and GA4 glucosyl ester. At high levels (22 �g) of carrier GA4, [3H]GA4 metabolism was dampened, and ABA reduced the metabolism of [3H]GA4 even further.
Enhanced metabolism of [3H]GA4 in P. radiata by ABA is analogous to an earlier report [Nadeau et al. (1972). Planta 107, 315-24] where ABA enhanced the metabolism of [3H]GA1 in barley aleurone layers while reducing their GA1-stimulated amylase production. However, in P. radiata, ABA increased xylem cell radial growth while enhancing [3H]GA4 metabolism. If the metabolites of GA4 that were enhanced by ABA were highly active, a similar effect might also be exerted on endogenous GAs, thus explaining the modest tendency of ABA to promote radial growth through much of the year.
Isolation and Characterization of 1'-O-Abscisic Acid- β -D-Glucopyranoside From Vegetative Tomato Tissue
Authors: Loveys BR , Milborrow BV
Published: January 2006

A new, polar metabolite of abscisic acid (ABA) has been isolated from an aqueous extract of tomato plants. The compound is acidic, soluble in butanol and slightly soluble in acidic ethyl acetate. It is a major constituent of the products formed from (�)-[2-14C]abscisic acid and it occurs naturally.
The structure was determined by gas-liquid chromatography-mass spectrometry (g.l.c.-m.s.) and nuclear magnetic resonance (n.m.r.) spectrometry as the 1'-O-β-D-giucopyrairoside of abscisic acid (ABAGS). The glucosyl moiety was identified by g.l.c.-m.s. and a glucose oxidase test, the ABA by n.m.r. and g.l.c. Tests with α- and β-glucosidase proved inconclusive, but the signal of the anomeric proton in the �H n.m.r. spectrum showed the 8 Hz coupling of a β-glucoside. ABAGS can be methylated with redistilled diazomethane and, like the glucose ester of ABA (ABAGE), it is unstable in alkaline solutions.
Molecular cloning and expression of a cDNA encoding a microsomal w-6 fatty acid desaturase from cotton (Gossypium hirsutum)
Authors: Liu Qing , Singh Surinder P. , Brubaker Curt L. , Sharp Peter J. , Green Allan G. , Marshall D. R.
Published: January 2006

A cDNA (ghFAD2-1) encoding a seed-specific microsomal
ω-6 desaturase was isolated from a cotton
(Gossypium hirsutum L. cv. Deltapine-16) embryo cDNA
library. The deduced amino acid sequence showed substantial similarity to
other plant microsomal ω-6 desaturases. Northern blot analysis indicated
that the ghFAD2-1 transcript was specifically induced
during embryo development and expression of the transcript could not be
detected in leaves. Southern blot analysis using the coding region and
3′ untranslated region of ghFAD2-1 revealed that
microsomal ω-6 desaturase in cotton is encoded by a small multigene
family. There are at least two copies of ghFAD2-1 in two
tetraploid cotton species (G. hirsutum L. and
G. barbadense L.) and at least one copy in diploid
cotton species (G. herbaceum L.,
G. raimondii Ulbrich and
G. robinsonii Mueller).
The maize transcription factor Sn alters proanthocyanidin synthesis in transgenic Lotus corniculatus plants
Authors: Damiani Francesco , Paolocci Francesco , Cluster Paul D. , Arcioni Sergio , Tanner Gregory J. , Joseph Roslyn G. , Li Yu G. , de Majnik John , Larkin Philip J.
Published: January 2006

Lotus corniculatus L. plants were transformed with
Agrobacterium rhizogenes binary vector carrying the
maize Sn regulatory gene driven by the 35S promoter.
These plants showed modifications in the pattern of accumulation of
proanthocyanidin (PA). All the transformed plants but one showed an increase
in PA content in the root relative to control untransformed and control
gus gene transformed plants (C). With respect to the
PAaccumulation in leaves, Sn transgenic plants were
grouped in two classes: suppressed (S), that showed a consistent reduction of
foliar PAcontent, and unsuppressed (U) that did not differ significantly from
controls. Dihydroflavanol reductase (DFR) and leucocyanidin reductase (LAR)
enzyme activities in S and U plant leaves mirrored the changes seen with
foliar PA accumulation. LAR activity in the roots was consistent with the root
PA levels. Mature Sn mRNA accumulated in the leaves of U
plants, but not in leaves of S plants; however, leaves of both S and U plants
were able to initiate Sn transcription. All
Sn-transformed plants accumulated
Sn message in root tissue. A possible negative
interaction of Sn and an unidentified homologous
endogene is proposed for explaining the behaviour of S plants.
The multiple alternative oxidase proteins of soybean
Authors: Tanudji M. , Djajanegara I. N. , Daley D. O. , McCabe T. C. , Finnegan P. M. , Day D. A. , Whelan J.
Published: January 2006

The identity of the multiple alternative oxidase bands detected in various
soybean tissues was investigated to determine if any modification that can
alter the mobility on SDS-PAGE of the alternative oxidase occurs after
mitochondrial import other than removal of the presequence. Comparison of the
mature, in vitro imported products of AOX1, AOX2 and
AOX3 in soybean cotyledons and rat liver mitochondria indicated that they had
an identical apparent molecular mass to their in vitro
expressed mature forms. This suggests that no modification specific to plant
alternative oxidase altering the mobility on SDS-PAGE, took place. Changing
the –2 and/or –3 Arg residue resulted in the inhibition of the
generation of this mature form, suggesting that processing was most likely by
the general mitochondrial processing peptidase. Comparison of the
in vitro expressed mature forms to that detected by
immunoblots of soybean tissues, required the induction of AOX1. Treatment of
soybean cultured cells with antimycin A resulted in the induction of an
additional band cross-reacting to monoclonal antibodies against the
alternative oxidase. Comparison of the in vitro
expressed mature forms to the alternative oxidase detected by western blotting
indicated that they were identical in apparent molecular mass. These results
indicated that no modification other than presequence removal, which alters
mobility on SDS-PAGE, was required to generate the mature functional
alternative oxidase proteins.
Regulation of bud dormancy by manipulation of ABA in isolated buds of Rosa hybrida cultured in vitro
Authors: Le Bris Manuel , Michaux-Ferrière Nicole , Jacob Yves , Poupet Alain , Barthe Philippe , Guigonis Jean-Marie , Page-Degivry Marie-Thérèse Le
Published: January 2006

In vitro cultures showed that the proximal buds isolated
from a rose (Rosa hybrida L. cv. Ruidriko Vivaldi®)
stem were endodormant. Growth and a high percentage of bud break could be
observed when cultures were treated with fluridone, an inhibitor of carotenoid
synthesis. Flow cytometry determination of nuclear DNA content revealed that
cell cycle activity of endodormant buds was arrested in the G
1 phase. Upon culture, the large decrease in bud ABA
content was responsible for the progress from G1 to
G2 phase whatever the culture medium. However, in
control culture, neither cell division nor leaf primordium initiation could be
observed and cells appeared stably arrested in G2 . By
contrast, with fluridone, an additional ABA decrease was observed resulting
from an inhibition of its synthesis inside the bud. New leaf primordia were
initiated and many figures of mitosis could be observed, indicating that
intense activity of cell division occurred after DNA replication. Therefore,
the results indicate that, as long as ABA was synthesized inside the buds,
cell cycle was arrested in G2 phase and buds remained
dormant. Continued in situ ABA biosynthesis appears, therefore, to be required
for the maintenance of bud dormancy.
Variability in hydraulic architecture and gas exchange of common bean (Phaseolus vulgaris) cultivars under well-watered conditions: interactions with leaf size
Authors: Mencuccini Maurizio , Comstock Jonathan
Published: January 2006

In a greenhouse study, 12 common bean cultivars from a wide geographical range
were compared for their morphological, gas exchange and hydraulic architecture
characters. Cultivars bred for cultivation in hot and dry regions had
significantly smaller leaves and crowns, but higher stomatal conductances and
transpiration rates per unit of leaf area. Short-term variability in gas
exchange rates was confirmed using leaf carbon isotope discrimination. A
literature survey showed that, although previously unnoticed, the strong
inverse coupling between leaf size and gas exchange rates was present in three
other studies using the same set of cultivars. Several measures of
‘leaf-specific hydraulic conductance’ (i.e. for the whole plant
and for different parts of the xylem pathway) were also linearly related to
rates of water loss, suggesting that the coupling between leaf size and gas
exchange was mediated by a hydraulic mechanism. It is possible that breeding
for high production in hot regions has exerted a selection pressure to
increase leaf-level gas exchange rates and leaf cooling. The associated
reductions in leaf size may be explained by the need to maintain equilibrium
between whole-plant water loss and liquid-phase hydraulic conductance.
Auxin induction is a trigger for root gall formation caused by root-knot nematodes in white clover and is associated with the activation of the flavonoid pathway
Authors: Hutangura Pokkwan , Mathesius Ulrike , Jones Mike G. K. , Rolfe Barry G.
Published: January 2006

We studied the expression of the auxin responsive promoter (GH3) fused to the
gusA reporter gene in white clover (Trifolium repens cv.
Haifa) during the initiation of root galls by root-knot nematodes
(Meloidogyne javanica) to investigate whether nematode
infection affects auxin distribution in developing galls. In search for a
plant signal that would mediate changes in auxin location we studied the
induction of the flavonoid pathway because flavonoids can act as auxin
transport regulators. Three chalcone synthase (CHS1,
CHS2 and CHS3)
promoter:gusA fusions were examined in transgenic plants
and flavonoids were detected using fluorescence microscopy. Within 24 h post
inoculation CHS:gusA expression occurred around the
invading nematode. At 48 h post inoculation CHS:gusA
expression and flavonoids were detected throughout the infection site,
followed by high GH3:gusA expression in the gall
48–72 h post inoculation. Initially (48–72 h post inoculation)
high GH3:gusA expression in giant cell precursors was
followed by low expression in the enlarging giant cells (96–120 h post
inoculation), suggesting that auxin is needed as a trigger for giant cell
initiation but not for later enlargement. We suggest that nematodes control
auxin distribution in the root and that flavonoids could be responsible for
controlling auxin accumulation.
Rhizobium purine auxotrophs, perturbed in nodulation, have multiple changes in protein synthesis
Authors: Worland Simon , Guerreiro Nelson , Yip Lina , Djordjevic Michael A. , Weinman Jeremy J. , Djordjevic Steven P. , Rolfe Barry G.
Published: January 2006

We investigated the infectivity, growth ability and the overall biochemical
status of Rhizobium purine auxotrophs to determine why
these strains show varied nodulation phenotypes on their host plants. Strains
ANU2861 (purM::Tn5) and ANU2866
(purY::Tn5), both derivatives of
ANU280, are unable to nodulate siratro plants. In contrast, strain L1
(purF::Tn5ssgusA40), a derivative
of ANU843, is able to induce fully-developed nodules and normal levels of
nodulation on several clover hosts. To our knowledge, strain L1 is the only
genetically-defined pur–
mutant capable of inducing fully-developed nodules on a legume host. None of
the pur– mutants are able to
grow at normal rates in vitro even in the presence of
purine pathway supplements including AICA-riboside. Further, the nodulation
ability of the strain ANU280
pur– mutants is unable to be
restored by the addition of AICA-riboside. Full growth and nodulation ability
can only be restored to the
pur– mutants by genetic
complementation. We confirmed that supplementation of
pur intermediates failed to fully restore wild-type
growth by using proteome analysis to examine the overall biochemical status of
the mutants. Proteome analysis demonstrated that the purine mutants possess
multiple changes in the protein species present. In addition, strain ANU2866
but not strains ANU2861 or L1 could not tolerate the effects of nutrient
step-up or step-down transitions, and failed to produce any colonies on
laboratory media. Collectively, these data show that purine auxotrophs suffer
pleiotropic effects at the level of protein synthesis and their overall
metabolism is compromised. Therefore, care should be exercised in concluding
that purine intermediates or by-products of this pathway are required
per se for nodule development.
Agrobacterium-mediated transformation of indica rice cultivars using binary and superbinary vectors
Authors: Khanna H. K. , Raina S. K.
Published: January 2006

The Agrobacterium-mediated transformation system was
extended to two indica cultivars: a widely cultivated breeding line IR-64 and
an elite basmati cultivar Karnal Local. Root tips and
shoot tips of seedlings, and scutellar-calli derived from mature seeds showed
high-efficiency Agrobacterium tumefaciens infection and
stable transformation. In addition to the superbinary vector pTOK233 in
Agrobacterium strain LBA4404, almost equally high levels
of transformation were achieved with a relatively much smaller (13.1 kb)
binary vector (pCAMBIA1301) in a supervirulent host strain AGL1. In both
cases, as well as in both cultivars, while 60–90% of the infected
explants produced calli resistant to the selectable agent hygromycin,
59–75% of such calli tested positive for GUS. A high level (400
µM) of acetosyringone in the preinduction medium for
Agrobacterium and a higher level (500 µM) in the
cocultivation medium was necessary for an enhancement in transformation
frequency of the binary vector to levels comparable to a superbinary.
Hygromycin-resistant calli could be produced from all the explants used.
Transformants could be regenerated for both cultivars using the superbinary
and binary vector, but only for calli of scutellar origin. In addition to the
molecular confirmation of hpt and
gus gene transfer and transcription, absence of gene
sequences outside the transferred DNA (T-DNA) region confirmed absence of any
long T-DNA transfer.
Movement of Water and Mass Transfer Into Developing Grains of Wheat
Authors: Jenner CF
Published: January 2006

A method was developed for measuring the net fluxes of water (Fw) and dry matter (Fdm) through the stalk attaching the grain to the rachis. After the removal of the bracts, the base of the grain was embedded in plastic material of low permeability, and a capsule containing water or solutions of known water potential was sealed over the grain. Fw and Fdm were measured gravimetrically as changes in weight of the grain and the contents of the capsule during 4 days. Fdm was independent of the water potential gradient between the rachis and the atmosphere within the capsule (surrounding the grain), and was not related either to the size of Fw, or to the direction of the flow of water. Besides, Fw was too small to be consistent with a mechanism for the transport of assimilates involving proportional unloading of solute and solvent into the apoplastic phase of the grain.
Association Between Concentration of Organic Nutrients in the Grain, Endosperm Cell Number and Grain Dry Weight Within the Ear of Wheat
Authors: Singh BK , Jenner CF
Published: January 2006

The present investigation was conducted to examine the association between the concentrations of sugars and amino acids in the grain, cell number in the endosperm and final dry weights of grains at various positions within the ear of wheat. Variation in the grain weight within a spikelet or between spikelets was dependent upon the number of cells formed in the endosperm. Concentrations of assimilates measured in the grain, however, showed either no relationship or an inverse relationship with the endosperm cell numbers. Variation in cell number in the endosperm between spikelets inserted at different positions on the rachis was not related to the carbohydrate concentration in the sections of rachis bearing the respective spikelets.
On the Relationship Between Carbon Isotope Discrimination and the Intercellular Carbon Dioxide Concentration in Leaves
Authors: Farquhar GD , O'Leary MH , Berry JA
Published: January 2006

Theory is developed to explain the carbon isotopic composition of plants. It is shown how diffusion of gaseous CO2 can significantly affect carbon isotopic discrimination. The effects on discrimination by diffusion and carboxylation are integrated, yielding a simple relationship between discrimination and the ratio of the intercellular and atmospheric partial pressures of CO2. The effects of dark respiration and photorespiration are also considered, and it is suggested that they have relatively little effect on discrimination other than via their effects on intercellular p(CO2). It is also suggested that various environmental factors such as light, temperature, salinity and drought will also have effects via changes in intercellular p(CO2). A simple method is suggested for assessing water use efficiencies in the field.
δ13 Values of C4 Types in Grasses
Authors: Hattersley PW
Published: January 2006

δ13 values were determined for leaves of C4 grasses (Poaceae) of different photosynthetic types. For plants grown in the same environment at the same time, mean δ13 values for the three C4 types were: NADP-ME-type, - 11.350 � 0.13 s.e. (11 spp.); PCK-type, - 11.950 � 0.19 s.e. (11 spp.); and NAD-ME-type, -12.70 � 0.21 s.e. (9 spp.). Although there is some overlap between the values for individual species of the three groups, the difference between any two means is highly significant [P(t) < 0.01] and is not due to taxonomic sampling bias at the subfamily level. The differences in means may suggest that C4 types differ in rates of leakage of CO2 and HCO3- from PCR tissue ('photosynthetic carbon reduction' tissue: equivalent to 'Kranz' tissue), and/or, using Farquhar's (Appendix) expression for plant δ values, that C4 types differ in their average intercellular CO2 concentrations (c1). It is also possible that differences between C4 types exist in some other, unknown, leaf fractionation process. Apoplastic CO2 leakage from PCR tissue in NAD-ME-type C4 grasses, which do not possess a PCR 'suberized lamella' as found in NADP-ME- type and PCK-type C4 grasses, may give these species the most negative δ13 values. Expressions for C4 plant δ13 values, and a model for the δ13 values of CO2 and HCO3- in various pools and fluxes in C4 plant leaves, are given.
Salt Tolerance of Trifolium alexandrinum L. II. Ion Balance in Relation to Its Salt Tolerance
Authors: Winter E
Published: January 2006

Detailed analysis of K+, Na+ and Cl- contents and the distribution of leaf-applied 22NaCl and Na36Cl in roots, stems, petioles and leaves of T. alexandrinum grown under a moderate salinity regime showed that this plant uses several mechanisms to cope with moderate salinity: (1) retranslocation of Na+ (and Cl-) out of young leaves, maintaining salt concentrations which are low compared to stems and petioles; (2) predominant basipetal movement of leaf-exported Na+ and its extrusion into the medium; (3) establishment of a gradient of K+ :Na+ ratios along the plant axis providing highest K+ :Na+ in youngest stem parts and leaves; and (4) restricted transfer of Cl- from roots to shoots leading to moderate Cl- contents distributed equally in stem tissues of different ages. The results are discussed with respect to the dynamic aspects of salt tolerance and the terminology of 'salt-includers' and 'salt-excluders',
Comparison Between Osmotic and Hydrostatic Water Flows in a Higher Plant Cell: Determination of Hydraulic Conductivities and Reflection Coefficients in Isolated Epidermis of Tradescantia virginiana
Authors: Tyerman SD , Steudle E
Published: January 2006

Hydraulic conductivity (Lp), volumetric elastic modulus (ε) and reflection coefficients (δ) have been determined for cells from isolated strips of the lower epidermis of leaves of Tradescantia virginiana using the pressure probe. Lp was (6.4 � 4.5) × 10-8 ms-1 Mpa-1 [(6.4 � 4.5) × 10-7 cm s-1 bar-1; mean � s.d., n = 15 cells] and was independent of the cell turgor pressure (P) and of osmotic pressure of the bathing medium. P in Johnson's solution (π° = 0.09 MPa) was 0.42-0.67 MPa (4.2-6.7 bar), which was somewhat larger than in the intact tissue. ε increased linearly with increasing P in the pressure range from zero to full turgor. Reflection coefficients of some non-electrolytes were determined by measuring the ΔP in response to a change in external osmotic pressure (Δπ°) after the addition of the solutes. The data were corrected for solute flow. For sucrose, mannitol, urea, acetamide, formamide, glycerol and ethylene glycol, δ was close to unity and the cells behaved like ideal osmometers. For the monohydroxyalcohols n-propanol ( δ = -0.58), isopropanol (δ = 0.26), ethanol (δ = 0.25) and methanol (δ = 0.15), rather low reflection coefficients were found which were even negative for some solutes and cells. Values of δ obtained from measuring the inital water (volume) flow were in agreement with those determined from the ΔP/Δπ° ratios. For the rapidly permeating substances, the changes in turgor after the addition of solute were transient and the equilibration of solutes between cell and medium could be measured using the probe. Although unstirred layers may affect the equilibration of solute it should, in principle, be possible to use the technique for the determination of permeability coefficients of membranes of higher plant cells.
Hydraulic Properties of Pine and Bean Roots With Varying Degrees of Suberization, Vascular Differentiation and Mycorrhizal Infection.
Authors: Sands R , Fiscus EL , Reid CPP
Published: January 2006

The hydraulic behaviour of root systems of loblolly pine seedlings conformed to the model of Fiscus (1975) and Dalton et al. (1975). The average hydraulic conductance per unit of root surface area was 1.4 × 10-6 cm s-1 bar-1. The hydraulic conductance of various parts of pine root systems was determined using root severing experiments. The average hydraulic conductance of brown (older suberized) roots was 7.55 × 10-7 cm s-1 bar-1, and that of white (newly regenerated unsuberized) roots was 1.95 x 10-6 cm s-1 bar-1. Hydraulic conductance was independent of the amount of mycorrhizal infection. The mean maximum exudation rate from detopped seedlings at zero hydrostatic pressure difference was 1.31 × 10-7 cm s-1.
Axial conductance of nutrient solution by roots of bean plants and loblolly pine seedlings was measured at 25°C. Bean vessels and pine tracheids conducted at 0.4 and 0.55 times idealized Poiseuille conductance. Bean roots with differentiated vessels had 8 times more axial conductance per unit area of stele than pine roots, and 6.5 times more axial conductance than bean roots with undifferentiated vessels. Change in axial conductance of bean roots with temperature was completely explained by change in viscosity of the solution. Axial resistance was negligible in the experiments where the hydraulic conductance of whole root systems was measured.
Loading of Assimilates in Wheat Leaves. I. The Specialization of Vein Types for Separate Activities
Authors: Altus DP , Canny MJ
Published: January 2006

An autoradiographic study is reported of the movement of labelled assimilate into the vein network in the area of the leaf fed 14CO2, and in the zone of the leaf proximal to the fed area. In the fed area the labelled assimilate is concentrated first in the intermediate veins and transported via the transverse veins to the lateral veins in which it rapidly moves basipetally. The intermediate veins distribute the label up and down the leaf 1-2 mm to or from the nearest transverse vein. They appear to function primarily as loading, collecting and distributing reservoirs. Proximal to the fed zone, the labelled assimilate translocated in the lateral veins spreads into the network of transverse and intermediate veins. The vein types have therefore different primary functions and may differ in their transport mechanisms. Measurements of the cross-sectional area of phloem in the three types of veins along the leaf blade are consistent with the idea that the laterals are translocating veins and the intermediates are collecting reservoirs. Quantitative estimates are made of the fluxes of assimilate in the three vein types.
In vivo Changes in Chloroplast ThylakoidMembrane Activity during Viable and Non-viable Dehydration of a Drought-tolerant Plant, Borya nitida
Authors: Hethzerington SE , Smillie RM , Hallam ND
Published: January 2006

Expanded leaves of Borya nitida Labill. were detached and placed in atmospheres of 100, 96, 88, 53 or 13% relative humidity at 25°C. In vivo chlorophyll fluorescence induction kinetics and the photooxidation of cytochrome f were measured before and after dehydration and again after rehydration by floating on water. In contrast to slow dehydration at 96% R.H., which resulted in an initial stimulation of photosystem II activity, the slow development of a partial block on the photoreducing side of photosystem II and the eventual degreening of leaves to a yellow viable condition, fast dehydration at 13% R.H. induced rapid loss of photosystem I activity and a slower development of a block on the photooxidizing side of photosystem . Although the leaves remained green, photo- system activity did not recover upon rehydration. Charge separation in the photosystem II complex still took place in the dehydrated leaves but upon rehydration the photosystem II reaction centre appeared to be disassociated from the light harvesting system. Dehydration at intermediate relative humidities (88 and 53%) led to a partial block on the photoreducing side of photosystem II and, more slowly, inhibition of photosynthetic electron transfer on the photooxidizing side of photosystem II. Following rehydration there was partial recovery of reactions associated with photosystem I but the leaves were unable to return to their original condition.
Structural Aspects of Protein Accumulation in Developing Pea Cotyledons. Iv. Effects of Preparative Procedures on Ultrastructural Integrity.
Authors: Goodchild DJ , Craig S
Published: January 2006

The pea storage proteins legumin and vicilin have previously been shown to be deposited in the vacuoles of cells of young developing cotyledons. By electron microscopy, the appearance of vacuole contents, and in particular of the peripheral protein deposits, are known to vary even in controlled and reproducible conditions of plant growth. This observation suggests an influence of specimen preparation on appearance. Different fixative solutions used on developing pea-seed cotyledons affected the appearance of the cytoplasm and its contents only slightly. The appearance of vacuole contents was greatly modified by the type of buffer used as a fixative vehicle and by osmotic conditions induced by added sucrose, and less by the primary fixative used. From a comparison with living protoplasts from cotyledon cells, it was concluded that the non-membrane-bound peripheral protein deposits are not artefacts of preparation. It is suggested that sucrose may play a role in the transition of vacuoles to protein bodies.
Photosynthesis and Transpiration of Pinus Radiata D. Don Under Plantation Conditions in Southern Australia. Ii. First-Year Seedlings and 5-Year-Old Trees on Aeolian Sands at Rennick (South-Western Victoria).
Authors: Attiwill PM , Squire RO , Neales TF
Published: January 2006

Measurements of net CO2 assimilation and transpiration rates were made over 4 days in the field in February 1980, on first-year seedlings and 5-year-old trees of Pinus radiata growing in plantation conditions in SW. Victoria. Gas exchange, enclosure, methods were used. Very high needle temperatures (to 45�C) and vapour pressure differences (to 70 mbar) were encountered. Watering treatments allowed estimates to be made of the effect of existing soil water deficits.
The maximum rates of assimilation observed were 3.78 �mol CO2 m-� s-� in the watered seedlings and 3.15 �mol m-� s-� in the unwatered tree. These values are 40% less than has been recently reported for P. radiata in New Zealand but agree with other data for P. radiata and other conifers. The light saturation of net photosynthesis occurred at c. 350 W m-�.
Increase in needle-air vapour pressure difference reduced needle conductance. Decrease of needle temperature and of vapour pressure difference from very high values, due to a rapid drop in air temperature, was accompanied by an increase of assimilation rate and of needle conductance, confirming that needle temperatures above about 30�C are supraoptimal for P. radiata.
Watering increased assimilation rate, needle water potential and needle conductance. This was most apparent in the seedlings; the responses of the older trees were much less marked.
Effect of Pretreatment Temperature on Response of Photosynthesis Rate in Maize to Current Temperature.
Authors: Bennett KJ , Mcpherson HG , Warrington IJ
Published: January 2006

Maize plants (hybrid XL45) were exposed to three temperature treatments of different duration: a 'growth' temperature (extending from sowing to the day before photosynthetic measurements were made), an 'acclimation' temperature (exposure to a given temperature for 24 h) and a 'measurement' temperature (the temperature during the photosynthetic measurement, 30-45 min duration).
The measurement temperature had the greatest single effect on photosynthetic rate, which increased 2-3-fold between 16 and 35�C.
The highest rate of apparent photosynthesis was measured in plants grown at 25�C, acclimated at 35�C and measured at 35�C (2.1 mg m-� s-�).
The relative contribution of stomatal and residual resistances to the total resistance to CO2 uptake changed little with temperature treatment, but the absolute magnitude of these resistances was strongly affected by temperature. Stomatal resistances ranged from 200 to 700 s m-�. The stomatal resistance dominated, accounting for 65-80% of the total resistance to apparent photosynthesis.
Chlorophyll concentrations changed in response to both growth and acclimation temperatures. Those grown at 16�C had the lowest concentration, those grown at 35�C the highest. The chlorophyll concentration changed over a 24-h acclimation period in both expanding and fully expanded leaves, increasing when plants were transferred to higher temperature and decreasing when the transfer was to lower temperature.
Nitrate Reductase Activity During Ontogeny of the Fruit of Cashew (Anacardium occidentale L.)
Authors: Subbaiah CC , Balasimha D
Published: January 2006

The in vivo nitrate reductase (NR) activity was assayed in the pedicel (apple), the fruit wall (shell) and the ovule (kernel) of cashew at 5-day intervals after fertilization. The pericarp showed high rates of enzyme activity during fresh weight accumulation, but activity remained low in the pedicel during its development. Estimation, using a graphical integration method, of total nitrate reduced by individual parts of the fruit showed that the pericarp contributed the maximum (67.5%) and the pedicel the least (7.8%) to the total nitrate assimilated in the fruit.
The rate of NR activity varied with tissue nitrate content in any fruit part but was not related to the pattern of organic nitrogen accumulation except in the case of the ovule. However, NR activity of the true fruit (the nut) was accountable for about 3-4% of the total organic nitrogen present at maturity. Besides its major role in nitrate assimilation, there was evidence that the pericarp exports about 60% of its nitrogen to the seed.
Inhibition of CO2 Assimilation by Supraoptimal CO2: Effect of Light and Temperature
Authors: Woo KC , Wong SC
Published: January 2006

In cotton the rate of CO2 assimilation, at O2 partial pressures up to 200 mbar, increased to a maximum and then declined as the intercellular partial pressure of CO2 was increased. The specific intercellular partial pressure of CO2 at which rate of assimilation began to decline depended on the environmental conditions. At 19 mbar partial pressure of O2 the decline occurred at CO2 partial pressure >390 �bar. At 200 mbar partial pressure of O2 it occurred at CO2 partial pressure > 534 �bar. O2 increased the CO2 partial pressure required for inhibition but it did not appear to affect the steepness of the decline of rate of assimilation with further increase in partial pressure of CO2 once the decline became apparent. The decline was more readily observed at low temperature and low O2 partial pressure, and in plants grown at low light and NO3- levels. It was also observed in cowpea and sunflower. Changes in quantum efficiency in cotton at high and low CO2 concentrations were observed. At ambient CO2 concentration (300 �bar), the quantum yields measured at 19 and 200 mbar partial pressure of O2 were 0.072 � 0.0003 and 0.053 � 0.0060 mol CO2 per mol absorbed quanta, respectively. In contrast, at 900 �bar CO2 partial pressure the respective values were 0.050 � 0.0023 and 0.070 � 0.0006 mol CO2 per mol absorbed quanta. The nature of the inhibition of CO2 assimilation by high partial pressure of CO2 is discussed.
Salt Tolerance in the Wild Relatives of the Cultivated Tomato: Responses of Lycopersicon esculentum, L. cheesmanii, L. peruvianum, Solanum pennellii and F1 Hybrids to High Salinity
Authors: Tal M , Shannon MC
Published: January 2006

The performance of three wild relatives of the cultivated tomato (Lycopersicon cheesmanii, L. peruvianum and Solanum pennellii) and two tomato cultivars in control and saline media was compared. The parameters studied were elongation rate of the main stem, succulence, and accumulation of Na+, K+, and Cl- in the roots, stem, leaf, and shoot tip. The same parameters but in the leaf only were also studied comparatively in two of the wild species L. cheesmanii and S. pennellii, the same two cultivars, and F1 hybrids.
Under control conditions, the elongation rate of the stem of the two cultivars was higher than that of the wild plants, but under salinity it was relatively lower. Among all species, S. pennellii was the most succulent in all its major parts under both control and saline conditions. The wild species, especially S. pennellii, showed high accumulation of Na+ in the leaf and top and a greater decrease in K+ content under salinity as compared with the cultivated plants. In all three species, Na+ probably substitutes for potassium in, at least, some of its physiological functions.
Complete dominance of S. pennellii over the cultivated plants is indicated for the relative decrease of elongation rate and K+ level and for the increase of succulence under salinity. In contrast, L. cheesmanii seems to be completely dominant only for the relative decrease of K+ under salinity.
Control by Indole-3-Acetic Acid of Wood Production in Pinus radiata D. Don Segments in Culture
Authors: Sheriff DW
Published: January 2006

The effect of indole-3-acetic acid (IAA) on stem radius growth, tracheid lumen diameter, and tracheid wall thickness in P. radiata was investigated. Stem segments from trees that normally produce high-density wood and from trees that normally produce low-density wood were grown in vitro at a number of IAA concentrations between 0 and 20 mg l-1. Maximum increase in stem radius and maximum tracheid lumen diameter were found at IAA concentrations of 6-10 mg l-1. Tracheid wall thickness increased approximately linearly as IAA concentration was increased up to 20 mg l-1. Absolute differences in radial stem increase and in cell lumen diameter between the high- and the low-density stems were greatest at IAA concentrations of 4-10 mg l-1. At low or high IAA concentrations, absolute differences between the clones in their stem radial increase and in their tracheid lumen diameter were small. Proportional differences between the clones in these two factors were greatest at IAA concentrations of 10 mg l-1. Clonal differences in the tracheid wall volume per unit stem volume could account for the differences in wood density only at IAA concentrations of 4-10 mg l-1.
Distribution of Copper and Other Elements in Ryegrass Roots, Determined With a Scanning Proton Microprobe
Authors: Mazzolini AP , Jeffery JJ , Uren NC , Legge GJF
Published: January 2006

A scanning proton microprobe has been used to determine the distribution of Cu and other elements in Wimmera ryegrass roots grown in solution cultures. Cu was found to be localized on or near the surface of the roots, in randomly distributed discrete zones. The distribution of Cu was partially correlated with those of Fe, P and Ca and possibly indicates some form of association; coprecipitation in a precipitate of Fe(III) phosphate or hydroxyoxide is favoured.
Respiratory Properties of Developing Bean and Pea Leaves
Authors: Azcon-Bieto J , Lambers H , Day DA
Published: January 2006

The rate of O2 uptake in the dark in bean leaves and leaf slices decreased during development. The use of inhibitors of the cytochrome and alternative pathways and the uncoupier carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) indicated that this decline was largely due to a decline in the activity and capacity of the cytochrome path. However, the capacity of the alternative path remained more or less constant with leaf expansion, and thus percentage cyanide resistance of respiration increased with leaf expansion. The activity of the alternative path was small in bean leaves and leaf slices, and decreased during development. Respiration, mainly the cytochrome pathway, of bean leaf slices was stimulated by FCCP at all ages, the stimulation being more pronounced in young leaves. The rate of overall respiration, the activities of the cytochrome and alternative paths, and the extent to which FCCP stimulated respiration in bean leaf slices were positively correlated with endogenous free sugar levels during aging. Similar trends were observed with mitochondria isolated from pea leaves. Leaf mitochondria from older plants had lower cytochrome path capacity, but the capacity of the alternative path remained much the same as that in leaf mitochondria from seedlings.
Jojoba: Temperature Adaptation as Expressed in Growth and Leaf Function
Authors: Wardlaw IF , Begg JE , Bagnall D , Dunstone RL
Published: January 2006

The adaptation of jojoba [Simmondsia chinensis (Link) Schneider] to temperature was studied under controlled conditions. Shoot extension and leaf area development reflected the very low rate of growth of this species, even under favourable conditions, and were stable with an increase in temperature from 20 to 30°C. However growth was markedly reduced at temperatures below 20°C and at 6°C there was no net gain in dry weight over a 42 day period. Root: shoot ratios were near unity and showed a small drop in response to increasing temperature. Leaves adapted to low temperature by an increase in thickness, specific leaf weight and starch content. Chlorophyll formation was retarded in young leaves developing at 15/10°C, but there was no sign of photodestruction of previously formed chlorophyll in mature leaves. Young leaves developing at 30/25°C had a very high chlorophyll a/b ratio of 9.5, but otherwise leaf chlorophyll was apparently normal (2.3-3.4) over a wide range of temperatures.
Light saturation of net CO2 exchange (NCE) occurred at about 1000 �E m-2 s-1 for leaves grown over a wide range of temperatures and the maximum NCE of approximately 16 mg CO2 dm-2 h-1 (0.45 mg m-2 s-1) occurred between 19 and 25°C. Pulse labelling with 14CO2 indicated that low temperature (18°C) reduced the rate of transfer of 14C from the primary products of fixation to sucrose. The rate of movement of 14C-labelled photosynthate out of the leaf was negligible at 18°C, and reached only about 3% h-1 at 30°C. In the stems, shortly after 14CO2 uptake by the leaf, 86% of the 14C activity was in sucrose, indicating that this was the preferred form of translocate in the vascular system. However glucose was more abundant in the leaves than sucrose, particularly at low temperatures. Starch accumulated in the leaves at low temperatures, reaching nearly 30% of the dry weight at 18/13°C.
Photosynthetic stability rather than active adaptation appears to form the basis of resistance to temperature stress in jojoba. With low rates even under optimal conditions this is essentially one of adaptation for survival rather than adaptation for production.