bluuebunny/crossref_metadata_2025 huggingface dataset:
Cotyledonary Storage Proteins in Pisum Sativum. II. Hereditary Variation in Components of the Legumin and Vicilin Fractions
Authors: Thomson JA , Schroeder HE
Published: January 2006

Gel electrophoresis has been used to investigate genetically controlled variation in storage-protein constituents forming five series of bands (LA-LE) derived from legumin fractions, and three series of bands (VA-VC) from vicilin fractions, of pea seeds. In each variant system, the phenotypes of the storage-protein polypeptides from F1 seeds were additive with respect to the band patterns of the parental lines, and identical in reciprocal crosses. Neither dominance nor formation of new interaction products was observed.
Variation in the three systems involving vicilin polypeptides and two of those involving legumin components was found to be based on allelic alternatives at single loci designated Vicilin A (Vca), Vicilin B (Vcb), Vicilin C (Vcc), Legumin A (Lga) and Legumin C (Lgc). For each of these variant systems, the gene products involved and the basis of the phenotypic variation have been discussed. Variants of the VC band complex, in which mobility of two bands both composed of 12 and 14 kdalton polypeptides is altered, appear likely to correspond to vicilin variants described previously. Type lines are specified for each of the variant phenotypes analysed, and for the genes designated.
Interrelation Between Low Temperature and Anaerobiosis in the Induction of Germination of Cocklebur Seed
Authors: Esashi Y , Tsukada Y , Ohhara Y
Published: January 2006

Non-dormant upper cocklebur (Xanthium pensylvanicum Wallr.) seeds germinated bimodally, in response to low temperature as well as to high temperature. At low temperature, the process was aerobic. Increase in germination potential by pre-exposure to low temperature was termed 'chilling induction'. Similarly to anaerobic induction of cocklebur seed germination, chilling induction required a certain time of presoaking to be effective. The germination pattern was identical in both cases, the seed coat being broken at the axial end.
In contrast to anaerobic induction, however, chilling induction was not affected by exogenous ethylene and the effect of chilling was cumulative within 3-4 days, but decreased with increasing duration of chilling beyond these times. The effect of anaerobic induction was enhanced by a pre- ceding chilling, as described in a previous paper and, similarly, the effect of chilling induction for fully presoaked seeds was additively increased by a preceding period of anaerobiosis. However, the effect of the chilling was decreased by a subsequent anaerobiosis.
Salinity Damage to Norfolk Island Pines Caused by Surfactants. II. Effects of Sea Water and Surfactant Mixtures on the Health of Whole Plants
Authors: Dowden HGM , Lambert MJ , Truman R
Published: January 2006

A disorder of Norfolk Island pines, Araucaria heterophylla (Salisb.) Franco, has occurred on certain urbanized parts of the coast of New South Wales. Observation and survey work suggested that the disorder was due to excessive foliar uptake of salt, induced by surfactants derived from sewage discharged into the sea. The work described in this paper was part of a programme of studies designed to test this hypothesis.
Glasshouse experiments were carried out to test the effects of distilled water and deep-sea water both with and without added surfactants sprayed onto the foliage of young potted Norfolk Island pines. Whereas the distilled water effects were minimal, some needle and shoot necrosis occurred in all plants sprayed with sea water and this effect was markedly accentuated when surfactant was present. Shoot necrosis was highly significantly correlated with the concentration of sodium and chloride taken up by the foliage, and the foliar salt levels were very similar to those found in deteriorating trees located by the seaside. The results showed that a commonly used surfactant, when sprayed in a sea-water solution onto Norfolk Island pine foliage, caused damage similar to that observed in affected seaside trees.
Effect of Sulfur Supply on the Seed Globulin Composition of Various Species of Lupin
Authors: Gillespie JM , Blagrove RJ , Randall PJ
Published: January 2006

The protein level in seeds of six species of lupin, grown either under sulfur deficiency or with adequate sulfur fertilization, is marginally affected by sulfur supply. However, the ratio of total sulfur to total nitrogen in the seed is greatly decreased under sulfur deficiency. This large change in sulfur-to-nitrogen ratio is accompanied by suppression of the synthesis of conglutins α and γ, which contain a significant amount of cyst(e)ine and methionine. The level of protein is maintained by increased synthesis of conglutin β, which normally contains no methionine and a low proportion of cyst(e)ine. These changes in the proportions of the proteins are reflected in the amino acid analyses for the globulin extracts.
The changes in protein subunit composition which accompany the differences in the proportions of the proteins have been studied using sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The results emphasize the differences in subunit composition between lupin species in terms of the number of components, their molecular weights and the importance of disulfide bonding. Two-dimensional electrophoresis, using cellulose acetate and SDS-polyacrylamide gradient gels, has been used to compare the subunit composition of the individual globulins for Lupinus angustifolius and L. elegans at both sulfur levels.
Foliar Absorption in Prunus domestica L. I. Nature and Development of the Surface Wax Barrier
Authors: Leece DR
Published: January 2006

Surface wax concentration, distribution, ultrastructure and wettability, as affected by developmental temperature, physiological age and seasonal changes, were studied on leaves of Prunus domestica. Surface waxes covered both leaf surfaces in an amorphous sheet, which extended over the guard cells on the abaxial surface. This sheet may have been thin or discontinuous above adaxial anticlinal walls. A secondary structure of wax ridges was superimposed on the amorphous sheet. Neither surface was readily wetted by water or by solutions of standard organic surfactants. The critical abaxial surface tension was estimated as 22-25 mNm-1 by Zisman plot, confirming that close-packed, oriented, methyl groups are exposed at the wax surface.
Surface wax concentration was inversely proportional to temperature during leaf development. At any time, surface waxes differed little among leaves of different physiological ages, but wax concentration increased during the season on leaves of similar physiological age reaching a maximum on the abaxial surface in mid-summer and thereafter remaining constant. Results are discussed in terms of polar pathways through the cuticle, stomatal penetration and spray application strategies.
Effect of Chloride on Nitrate Accumulation in Pawpaw (Carica papaya L.)
Authors: Menary RC , Allan P
Published: January 2006

An accumulation of chloride in leaves and fruits of the papaw is associated with high levels of nitrate in these tissues. High chloride levels in tissues did not affect plant growth, protein synthesis or the level of endogenous nitrate reductase acitvity. The amount of nitrate in the non-metabolic pool of leaves and fruits was significantly increased in the presence of chloride.
The Carbohydrate of Storage Glycoproteins From Seeds of Pisum sativum: Characterization and Distribution on Component Polypeptides
Authors: Davey RA , Dudman WF
Published: January 2006

Storage proteins were extracted from isolated protein bodies from mature seeds of Pisum sativum and separated into one legumin and four vicilin fractions. A comparative study was made of the glycosylation of each fraction and all were found to contain covalently attached carbohydrate at a level of between 0.9 and 1.4% of the protein weight. The carbohydrate composition of the legumin fraction was different from that of the vicilin fractions: the major sugar in legumin was glucose (Glc) with some mannose (Man) and glucosamine (GlcN) while, for all vicilin fractions, Man was the major sugar wlth GlcN, Glc and galactose (Gal) in lesser amounts. There were minor differences in carbohydrate composition between vicilin fractions. Each of the vicilin fractions was further separated by concanavalin A (Con A)-Sepharose 4B chromatography into two fractions. The protein which bound to Con A always contained more carbohydrate than the unbound fraction and, in one vicilin fraction, the unbound protein was not glycosylated. No legumin bound to Con A. Both the 20 and 40 kdalton polypeptides of legumin are glycosylated while the 14 kdalton polypeptide was the major site of glycosylation for all vicilin fractions. One vicilin fraction also has a similar amount of carbohydrate associated with a 50 kdalton polypeptide. Some other polypeptides in the vicilins were glycosylated but to a much lesser extent. These findings are compared to those for other legume storage proteins and their significance in storage protein biosynthesis is discussed.
Arsenic Uptake by Barley Seedlings
Authors: Asher CJ , Reay PF
Published: January 2006

Arsenate uptake consists of a rapid, apparently irreversible, initial phase followed by a less rapid 'steady state' phase, both of which are temperature sensitive and strongly inhibited by phosphate. By comparison, 'steady state' uptake of phosphate was only weakly inhibited by arsenate. The initial and 'steady state' phases of arsenate uptake were highly correlated (R = 0.958, P < 0.001). Arsenite also appeared to exhibit initial and 'steady state' uptake phases but uptake was slower by a factor of 3-4 than for arsenate at the same concentration. The results are discussed in relation to recent work on a DNP-sensitive initial binding step in the uptake of other elements.
An Open-Circuit Infrared Gas Analysis System for Measuring Aquatic Plant Photosynthesis at Physiological pH
Authors: Browse JA
Published: January 2006

A temperature-controlled assimilation chamber and gas circuit are described which allow steady-state measurement of photosynthesis by aquatic plants in media containing bicarbonate ions. Gas entering the assimilation chamber is divided into fine bubbles by passage through a sintered glass disc which forms the chamber floor. Rapid achievement and subsequent maintenance of chemical and phase equilibria are ensured by sustaining a high gas flow through the chamber via a recirculating loop in the gas circuit. Incorporation of this unit in a conventional open infrared gas analysis system allowed accurate and sensitive measurements to be made over wide ranges of pH and CO2 concentration.
Kernel Number Per Spike in Wheat (Triticum aestivum L.): Responses to Preanthesis Shading
Authors: Fischer RA , Stockman YM
Published: January 2006

Several cultivars of wheat, grown in pots in a controlled environment, were subject to single shading periods of 8-11 days within the interval from 36 days before anthesis until anthesis. The aim was to confirm sensitivity of kernel number to reduced irradiance as observed in the field and to investigate its causes.
Shading periods centred 10-13 days before anthesis had biggest effects on kernel number per spike through effects on kernels per spikelet. This was associated with greatest reductions in the spike dry weight at anthesis and with reductions in the number of competent florets (florets with full anther development) per unit spike dry weight; floret fertility (kernels per competent floret) was unaffected. Approximately 30% of the total dry weight increment of the plant was being allocated to the spike at the stage of greatest sensitivity to shading, but shading did not alter this partitioning. Maximum water soluble carbohydrate (WSC) content of the spike (30-40% on a dry basis in unshaded plants) occurred at 15 days before anthesis. Shading at the most sensitive period reduced temporarily WSC concentration in the spike, reduced stainable starch in carpels of florets of central spikelets, and reduced floret survival by increasing degeneration of distal florets. Shading before or after this period reduced kernel number less, reducing spike dry weight but not competent florets per unit spike dry weight. Reduced assimilate supply is probably the cause of these responses in the spike.
Molecular Weight of Legumin From Pisum sativum
Authors: Blagrove RJ , Lilley GG , Davey R
Published: January 2006

There have been many physicochemical studies of legumin, one of the major storage globulins isolated from pea seed. The more recent literature values for the molecular weight of this protein are in the range 390 000-420 000. These results are not consistent with the subunit molecular weight of legumin determined by dodecyl sulfate-polyacrylamide gel electrophoresis, if a hexameric model is assumed. We have measured the molecular weight of a highly purified sample of Pisum legumin by meniscus depletion sedimentation equilibrium and have found a value of 350 000 � 10 000. Since the oligomeric protein is homogeneous with respect to molecular weight, the heterogeneity reported for the subunit polypeptides, using various conditions of electrophoresis, presumably reflect differences in charge and amino acid composition. The molecular weight of legumin is significantly greater than the value of 325 000 found for cucurbitin, the equivalent crystalline protein isolated from pumpkin seed.
Cotyledonary Storage Proteins in Pisum sativum. V. Further Studies on Molecular Heterogeneity in the Vicilin Series of Holoproteins
Authors: Thomson JA , Schroeder HE , Tassie AM
Published: January 2006

The cotyledonary storage proteins of mature pea seeds were resolved by polyacrylamide gel electrophoresis in an acid buffer system as discrete bands comprising holoproteins referable to either the legumin or vicilin series. Three major and four less abundant vicilin holoproteins were detected in acid-gel separations after subfractionation of storage-protein extracts on the basis of differential solubility at specific pH values and ionic strengths, by electrophoresis in the alkaline pH range or by gel filtration. Acid-gel patterns were qualitatively consistent over a range of genotypes. Up to 12 polypeptides were found in varying proportions in reduced and dissociated eluates from fixed and stained vicilin bands separated on acid gels. Each vicilin holoprotein showed a distinctive quantitative, and in some cases qualitative, polypeptide composition.
Genetically determined size or charge variants of certain polypeptides used as markers were found in each of the major vicilin holoproteins. This observation, and the consistent appearance of the vicilin bands on acid gels after exposure to widely different treatments during subfractionation, indicate that these polypeptides are strictly subunits of the vicilins, rather than fortuitously associated components. Amongst the holoproteins of each band, some flexibility of subunit composition is indicated by evidence that the total of the molecular weights of the subunits exceeds the molecular weight of the corresponding holoprotein, and by the apparent relative abundance of certain subunits.
The observed complexity of subunit composition of the vicilins is consistent with previous findings of immunological similarities and differences amongst the holoproteins of this series, and with change during development in the subunit composition of these proteins.
Recovery After Water Stress of Leaf Gas Exchange in Panicum maximum var. trichoglume
Authors: Ludlow MM , Ng TT , Ford CW
Published: January 2006

Net photosynthesis of the last fully expanded leaf of P. maximum var. trichoglume was able to recover from leaf water potentials as low as -92 bar. The degree of stress experienced during the single drying cycle did not influence the maximum net photosynthetic rate attained during recovery, but the time taken to reach the maximum increased with the degree of stress experienced. During the first 24 h, the rate of recovery of net photosynthesis was mainly determined by the rate at which the water status improved. Leaves which experienced water potentials less than c. -40 bar had a slower rate of recovery of water potential than less stressed leaves. This was partially offset by higher rates of net photosynthesis. Furthermore, the relationship between leaf water potential and net photosynthesis recorded during the drying cycle was different from those measured during recovery. Thus different relationships must be used in models simulating behaviour during water stress and subsequent recovery.
Stomatal resistance exerted greater control than intracellular resistance over net photosynthesis in the recovery phase, irrespective of the water potential before rewatering or whether plants were preconditioned to stress. Although abscisic acid concentration was positively related to leaf water potential and stomatal resistance during the drying cycle, the relationship between abscisic acid concentration and stomatal resistance during recovery was poor or absent. Sucrose and amino-acid nitrogen accumulated during stress and decreased during recovery. However, the level of non- structural carbohydrates or nitrogen compounds in the recovery phase did not appear to influence net photosynthetic rate or its components. In fact, the reverse appeared to occur: the rate of photosynthesis and growth seemed to determine the levels of these compounds.
Changes in the Surface Characteristics of Capsules of Papaver somniferum L. During Maturation
Authors: Hofman PJ , Menary RC
Published: January 2006

Changes in the surface characteristics of capsules of P. somniferum and their effects on contact angle and water penetrability were monitored in a commercial crop during the 1978-79 season. The wax crystals on the surface of very immature capsules, and of mature capsules in which interplant abrasion was prevented by secure staking, were typically rod-shaped, at least 3 �m long and about 0.5 �m thick. However, under normal field conditions, damage to the wax structure and loss of wax from the capsule surface occurred. By week 11 after full bloom, approximately 80% of the capsule surface showed signs of damage, while at week 13 deep cavities had appeared which, coupled with fungal activity, resulted in severe damage to the external pericarp wall.
Associated with these changes, the contact angles of water droplets on the surface of the pericarp decreased and the apparent ability of water to penetrate the capsule increased as the capsule matured.
The disappearance of alkaloids from capsules is discussed in relation to wax damage, water penetration through the capsule wall and stigmatic rays, and fungal activity.
UV-B, red and far-red light regulate induction of the C4 isoform of NADP-malic enzyme in etiolated maize seedlings
Authors: Casati Paula , Drincovich María Fabiana , Andreo Carlos S. , Donahue Raymon , Edwards Gerald E.
Published: January 2006

The induction of NADP-malic enzyme (NADP-ME) in maize
(Zea mays) etiolated seedlings as a function of
intensity and duration of exposure to UV-B radiation was investigated by
measuring changes in activity and protein, as well as by levels of NADP-ME
gene transcripts. Exposures to UV radiation from 2 to 60 min including photon
flux densities of UV-B of 0.5–2 mmol quanta m-2
s-1 which are well below levels which occur naturally
under full sunlight, caused an increase in Me gene mRNA
and NADP-ME protein, as well as in NADP-ME activity. A similar dosage of UV-A
radiation was ineffective. A low level of red light (10 µmol quanta
m-2 s-1) for only 5 min was also
effective in inducing increases in NADP-ME activity equivalent to that with
UV-B radiation. A 5 min exposure to far red light (100 µmol quanta
m-2 s-1) following UV-B or red
light treatment largely reversed the induction of NADP-ME, and this effect of
far-red could be eliminated by further treatment with UV-B or red light. These
results indicate that physiological levels of UV-B radiation have a positive
effect on induction of the synthesis of a photosynthetic enzyme which is
involved in C4 photosynthesis.
Simulated Response of Tobacco Crops to Irradiance and Defoliation
Authors: Whitfield DM
Published: January 2006

Simulated rates of CO2 exchange of tobacco crops in response to incident irradiance and to defoliation were compared with measured values from the field. Comparison of daily trends in net rate of CO2 exchange and its change with upward defoliation showed that rates were largely dependent on the interaction of solar position and input with features of the architecture of the crop. These included plant extent and the distribution of sunlit leaf area with respect to the leaf-beam angle.
The model satisfactorily simulated net rate of CO2 exchange of a range of different intensities of downward defoliation. However, comparisons of estimated and observed responses indicated differences in the structure and/or photosynthetic characteristics of a medium intensity of defoliation as compared with a non-defoliated control or a crop which experienced the most severe defoliation.
Carbohydrate partitioning in the leaves of Bromeliaceae performing C3 photosynthesis or Crassulacean acid metabolism
Authors: Christopher John T. , Holtum Joseph A. M.
Published: January 2006

Carbohydrate accumulation was measured in the leaves of 11 speciesrepresenting the three subfamilies of Bromeliaceae. In the Tillandsioideae the C3 species Vriesea carinata Wawra accumulated starch and sucrose while the Crassulacean acid metabolism (CAM)species Tillandsia tricolor Schlechtendal & Chamissoaccumulated mainly starch. In the Pitcairnioideae the C3species Pitcairnia paniculata Ruiz & Pavon and two CAM species Dyckia sp. andFosterella schidosperma Barker accumulated sucrose butnot starch. Of six CAM species in the Bromelioideae, threeCryptanthus zonatus (Visiani) Beer,Neoregalia spectabilis Moore andPortea petropolitana Wawra accumulated starch but notsoluble sugars while three (Ananus comosus Linnaeus,Orthophytum vagans M.B. Foster andNidularium bilbergioides Schultes filius) accumulatedstarch as well as soluble sugars. Carbohydrate accumulation patterns weresimilar for species within each subfamily in that the Pitcairnioideae speciesdid not accumulate starch but accumulated sucrose while species from theTillandsioideae and Bromelioideae all accumulated starch (some alsoaccumulated soluble sugars). Carbohydrate accumulation patterns were notsimilar for C3 species versus CAM species from thedifferent subfamilies. These data suggest that variations in carbohydratebiochemistry resulting from different evolutionary histories have a greaterinfluence on carbohydrate accumulation patterns in CAM bromeliads than theconstraints of the CAM pathway itself.
Errors Arising From Rapid Water Loss in the Measurement of Leaf Water Potential by the Pressure Chamber Technique
Authors: Turner NC , Long MJ
Published: January 2006

In rapidly transpiring leaves, the water potentials of uncovered leaves measured in a pressure chamber were 0.2-0.7 MPa lower than the water potentials of leaves that were covered with a plastic sheath from just prior to their excision to the completion of the measurement. The error in the water potential of uncovered leaves arose from rapid water loss in the first 30 s after excision. The degree to which the water potentials were lowered depended on the rate of transpiration, the leaf water potential at the time of excision, the species, and whether the plants were grown in the glasshouse or field. It is suggested that the variation between species and between glasshouse-grown and field-grown plants arises from differences in water retention characteristics of plant tissue as well as to differences in the rates of transpiration at excision. The size of the error induced by the rapid water loss on diurnal changes in leaf water potential is demonstrated and the effect of the error in the calculation of turgor potentials and in the resistances to water flow through the plant is discussed.
Stomatal Behaviour of Kenaf and Sorghum in a Semiarid Tropical Environment. II. During the Day
Authors: Muchow RC , Fisher MJ , Ludlow MM , Myers RJK
Published: January 2006

The influence of leaf water potential (Ψl), saturation deficit (δe), and temperature on stornatal conductance (gs) of kenaf and sorghum was determined at non-limiting quantum fluxes both at high and low soil water status in the field, and under controlled environment conditions. Sorghum stomata closed in response to Ψl in a manner consistent with the classical feedback control, while kenaf stomata responded directly to δe, independently of Ψl. The rate of decrease of gs of kenaf with increasing δe was greater at higher temperatures. Also the stomata of stressed kenaf were less sensitive to δe than those of the well-watered crop due to the limitation in degree of stomatal opening imposed by water stress.
The degree of stomatal adjustment in kenaf was also assessed. In the stressed kenaf, the Ψl at half the maximum gs was c. 0.17 MPa lower and gs was more sensitive to decreases in Ψl, than in the well watered control. However, there was little difference in the Ψl at 95% stomatal closure.
Development of Responsiveness to Gibberellic Acid in the Aleurone Layer of Immature Wheat and Barley Caryopses: Effect of Temperature
Authors: Nicholls PB
Published: January 2006

Immature wheat caryopses were dried at different temperatures ranging from 4 to 30°C and the kinetics of increase of α-amylase activities in endosperm halves treated with gibberellic acid were investigated. Over the duration of the experiments the kinetic curve comprised of lag, curvilinear and linear phases, and the curvilinear phase could be fitted by a quadratic expression. The square root of α-amylase activity due to gibberellic acid was linearly related to time and from this the acceleration rate of production of α-amylase and duration of lag phase could be calculated.
The calculated acceleration rate for the production of α-amylase was correlated with drying temperatures below 20°C but not above. The lag phase for dry endosperm halves was biphasic, consisting of a gibberellic acid insensitive phase (hydration phase) and a hormone sensitive phase, the only phase present in fully imbibed endosperm halves. Duration of the hydration phase was inversely correlated with drying temperatures below 15°C but not above, whereas the duration of the subsequent hormone sensitive phase was not correlated with drying temperature.
It was concluded that low drying temperatures modified the subsequent behaviour of the aleurone layer, delaying the onset and reducing the rate of gibberellic acid-induced processes, which culminate in the production of °-amylase.
Photosynthetic Formation of Glycerate in Isolated Bundle Sheath Cells and Its Metabolism in Mesophyll Cells of the C4 Plant Panicum capillare L
Authors: Usuda H , Edwards GE
Published: January 2006

In isolated bundle sheath cells of P. capillare, glycerate is a major product of 14CO2 fixation at low bicarbonate concentrations. After 6 min of CO2 fixation at 0.34 mM NaHCO3, about 20% of the labelled products was in glycerate and about 45% in glycine plus serine. Inhibitors of the glycollate pathway prevented incorporation of label into glycerate. After 6 min of CO2 fixation at high bicarbonate concentration (20 mM NaH14CO3), a large percentage of the label was incorporated in phosphate esters, insolubles, and sucrose, and little label was observed in metabolites of the glycollate pathway. The results indicate glycerate is primarily formed through the glycollate pathway in bundle sheath cells rather than through 3-phosphoglycerate phosphatase. Glycerate-dependent oxygen evolution in the light and 14C incorporation into phosphate esters from [1-14C]glycerate was observed with mesophyll chloroplasts and mesophyll protoplasts, respectively, but not with bundle sheath cells. This is consistent with our previously published results that glycerate kinase is localized only in C4 mesophyll chloroplasts. Both isolated bundle sheath cells and mesophyll chloroplasts exhibited 3-phosphoglycerate dependent O2 evolution in the light indicating that the reductive phase of photosynthesis is functional in both cells. The results suggest that, during C4 photosynthesis, glycerate is synthesized by the glycollate pathway in bundle sheath cells and subsequently metabolized in mesophyll cells without direct linkage to the reductive pentose phosphate pathway.
Inhibition of quantum yield of PS II electron transport in Spirulina platensis by osmotic stress may be explained mainly by an increase in the proportion of the QB-non-reducing PS II reaction centres
Authors: Lu Congming , Zhang Jianhua , Vonshak Avigad
Published: January 2006

Modulated chlorophyll fluorescence and fluorescence induction kinetics were
used to evaluate the PS II photochemistry in
Spirulina platensis exposed to osmotic stress
(0–0.8 M mannitol). Osmotic stress decreased the efficiency of
excitation energy capture by open PS II reaction centres
(Fv′/Fm′)
and more significantly, decreased photochemical quenching
(qP). Osmotic stress also
decreased the maximal efficiency of PS II photochemistry
(Fv/Fm).
There was no significant change in non-photochemical quenching
(qN), indicating that the
decreased
Fv′/Fm′
was not due to an increase in qN.
Analyses of the fast fluorescence induction kinetics indicated that osmotic
stress caused a significant increase in the proportion of the QB-non-reducing
PS II reaction centres. Based on the results in this study, we suggest that a
substantial increase in the proportion of the QB-non-reducing PS II reaction
centres may be responsible for the decrease in
qP and
Fv′/Fm′,
of which both resulted in the decrease in the quantum yield of PS II electron
transport (ΦPSII ).
Different leaf surface characteristics of three grape cultivars affect leaf optical properties as measured with fibre optics: possible implication in stress tolerance
Authors: Karabourniotis G. , Bornman J. F. , Liakoura V.
Published: January 2006

Young leaves of three grape cultivars having different surface characteristics
(cv. Athiri, pubescent; cv. Soultanina, glabrous green; and cv. Fraoula,
glabrous red-brown) only during the early stages of their development, were
used to investigate the potential, differential effect of a trichome layer or
a pigmented epidermis on the light microenvironment within the mesophyll. The
penetration of forward propagated 310, 360 and 430 nm radiation into the leaf
tissues was monitored using a quartz fibre-optic microprobe. The mesophyll of
the young leaves of Athiri was much better protected from ultraviolet-A,
ultraviolet-B and high visible radiation compared to the other two cultivars.
Abaxial, as well as adaxial trichome layers attenuated almost all incident
radiation at 310 nm and 360 nm and a considerable part of the blue light (430
nm). No significant differences in light attenuation from epidermal and
mesophyll layers between the other two cultivars were observed. The adaxial
epidermis of young and dehaired leaves of cv. Athiri was largely ineffective
in absorbing the incident ultraviolet- B radiation. In addition, the dehaired
lamina of such leaves exhibited 80% lower relative concentration of
ultraviolet-absorbing compounds per leaf surface area, compared to leaves of
similar ontogenetic stage in the cv. Soultanina. It is proposed that the
occurrence of a dense trichome layer in young leaves, besides other proposed
functions, may play a protective role against not only ultraviolet radiation
damage, but also against high insolation. This protection could be
advantageous under stress conditions during leaf development.
Agrobacterium-mediated transformation of sugarcane using GFP as a screenable marker
Authors: Elliott Adrian R. , Campbell James A. , Brettell Richard I.S. , Grof Christopher P.L.
Published: January 2006

The use of the green fluorescent protein (GFP) and
in vivo screening for transgenic cells has enabled the
first visual selection of transgenic sugarcane
(Saccharum L. hybrid) transformed by
Agrobacterium-mediated techniques. Selection of
GFP-positive embryogenic callus transformed using
Agrobacterium tumefaciensstrain AGL0 was performed by
fluorescence microscopy for 6 weeks after transformation. The use of GFP as a
screenable marker aided the rapid segregation of individual transformation
events and facilitated the initial visual selection of transgenic sugarcane
callus without antibiotics, herbicides or an assay. The binary vector used in
transformation was pTO134, which contains a synthetic
gfp gene (sgfpS65T) and the
bialaphos resistance gene (bar) both controlled by CaMV
35S promoters. The appearance of GFP-expressing cells observed on embryogenic
callus was 5.3%. Subsequently, GFP-positive calli grew in the presence
of a level of the herbicide bialaphos, that was toxic to untransformed calli.
GFP-positive shoots were regenerated and one sugarcane plant expressed GFP in
the initial stages. Molecular analysis confirmed the presence of the
sgfpS65T coding region in the genome of regenerated
plants. Visual screening for Agrobacterium-mediated
transformation events using GFP was an efficient technique, which may be
applied for the transformation of other plants.
Physiology and histology of resistance to Striga hermonthica in Sorghum bicolor var. Framida
Authors: Arnaud Marie-Claire , Véronési Christophe , Thalouarn Patrick
Published: January 2006

Germination, attachment to host root and growth of
Striga hermonthica (Del.) Benth. seeds and seedlings
were studied in in vitro co-culture w ith
Sorghum bicolor (L.) Moench and in pot experiments. Two
varieties, the resistant Framida and the susceptible CK-60B, were used.
Histological, morphological and physiological studies revealed the key stages
of resistance mechanisms involved. Resistance of Framida to
Striga does not occur at the germination or the
attachment stages, since its roots do not support fewer
Striga than does CK-60B. As Framida roots support the
lowest number of young Striga stems with scale leaves,
its resistance appears to occur during the establishment of a functional
haustorium. Metabolite uptake by the haustorium and growth rate of the young
parasite were lower on Framida roots than on CK-60B roots, even when similarly
developed haustoria were compared. Furthermore, at a later stage of
infestation, significant accumulation of a coloured material likely to be rich
in phenolic compounds was observed in and around Framida conductive tissues,
but not CK-60B tissues. These features indicate the involvement of at least
three steps in development of resistance in Framida roots: the first is linked
to a partial inhibition of development of the young haustorium; the second
could play a role in the physiological events that decrease nutrient
translocation towards the haustoria; and the last seems to be associated with
the accumulation of a coloured phenolic-like material.
A tomato antisense 1-aminocyclopropane-1-carboxylic acid oxidase gene causes reduced ethylene production in transgenic broccoli
Authors: Henzi Maria X. , McNeil David L. , Christey Mary C. , Lill Ross E.
Published: January 2006

In this paper 11 transgenic broccoli (Brassica oleracea
L. var. italica) lines containing a tomato antisense
1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene from pTOM13 were
evaluated. Changes in respiration, ethylene production and ACC oxidase
activity were studied in mature flowers. Averaged across all ACC oxidase
transgenic lines, there was an initial increase followed by a substantial
decrease in ethylene production compared with the controls. Of the 11
transgenic lines, 10 lines showed a significant reduction in fethylene
production relative to the controls from 50 h after harvest. Green Beauty
flowers showed a significant reduction in respiration between the transgenics
and control and demonstrated how ethylene levels could control the stable, or
climacteric-like increase in respiration. ACC oxidase activity was higher in
transgenic plants, consistent with the initially higher ethylene production.
ACC oxidase activity did not, however, reflect the increase in ethylene
production found after 50 h for the controls. These results suggest that two
ethylene production systems may operate with only the second being inhibited
by the antisense ACC oxidase used and that the later system was not detected
by the ACC oxidase assay used. The results do show that post-harvest ethylene
synthesis and therefore possibly broccoli senescence can be regulated by using
an antisense ACC oxidase gene.
Persistence, Uptake and Translocation of [14C]Ethephon (2-Chloroethyl Phosphonic Acid) in Perlette and Cardinal Grapevines
Authors: Nir G , Lavee S
Published: January 2006

[14C]ethephon was applied to different organs of detached and intact shoots of some grapevine cultivars. Recovery of 14C-labelled compounds, 48 h after application indoors to detached leaves, was 53-61% of the amount applied. Recovery was between 58 and 72% of the amount applied 4 h earlier to different sites on young intact shoots of potted vines, in a greenhouse. Uptake of labelled compound was only 19-26% of the amount applied. Translocation of [14C]ethephon was very slight. Most of the applied labelled compound remained at the application sites for many hours. Translocation was mainly basipetal as confirmed also by autoradiography.
Contribution of Sugars to Osmotic Adjustment in Elongating and Expanded Zones of Wheat Leaves During Moderate Water Deficits at Two Light Levels
Authors: Munns R , Weir R
Published: January 2006

Water was withheld from wheat seedlings grown at two light levels, so that the soil water content was reduced by 50% and the leaf water potential of treated plants was about 0.5 MPa below that of controls. Growth was initially reduced but recovered after about 4 days of the water deficit treatment. Osmotic adjustment (calculated as the difference between the osmotic potential at 100% relative water content of the treated and controls plants) occurred in both the elongating and expanded zones of leaves. In plants grown at a very high irradiance, an increase in sugars accounted for 70-100% of the osmotic adjustment of 0.12-0.34 MPa in the elongating and expanded zones of leaves sampled both at dawn and at midday. The increased amounts of sugars were approximately equivalent to the decreased consumption of carbohydrate during the initial reduction in growth.
Glucose was the main component of the increase in sugars in the elongating regions, while sucrose was more important in the expanded laminae. During the morning, sugars increased to similar extents in controls and treated plants.
In plants grown at a moderate irradiance, sugars did not account for the osmotic adjustment of 0.10-0.21 MPa in the expanded laminae at dawn or at midday. At dawn, sugars were much lower in treated than in control plants but, during the morning, sugars accumulated more in the treated plants and sugar levels of the two groups at midday were similar. In contrast, sugar levels in the youngest elongating leaf of the treated plants were the same as in the controls at dawn, and were double those in the controls at midday.
Biosynthesis of Arabinogalactan-Protein in Lolium multiflorum Ryegrass Endosperm Cells. I. Hydroxylation of Peptidyl Proline
Authors: Pollard PC , Fincher GB
Published: January 2006

Suspension-cultured endosperm cells from L. multiflorum secrete into the medium an arabinogalactan-protein in which the protein moiety is rich in hydroxyproline. When cells are grown in the presence of proline labelled with 14C or 3H, the imino acid is rapidly removed from the medium and radio- activity can subsequently be detected in extracellular trichloracetic acid-soluble, ethanol-insoluble material. In this fraction, which contains the arabinogalactan-protein and other polysaccharides, radioactive label is distributed between proline and hydroxyproline. α,α'-Dipyridyl, a chelator of ferrous ion, has no effect on the total radioactivity secreted but markedly alters the distribution of radioactivity in favour of peptidyl proline. Although this inhibition of peptidyl proline hydroxylation can be reversed by ferrous or zinc ions, it is not possible to conclude that ferrous ion, which is required for hydroxylation in other systems, participates specifically in the reaction in ryegrass endosperm cells. Concomitant with the inhibition of proline hydroxylation, α,α'-dipyridyl suppresses the biosynthesis or secretion of extracellular arabinogalactan-protein and arabinoxylan.
Metabolism and Export of 14C-Labelled Photosynthate From Water-Stressed Leaves
Authors: Watson BT , Wardlaw IF
Published: January 2006

The effect of water stress on the translocation of 14C-labelled photosynthate from leaves was examined in four contrasting plant species, Sorghum sudanense (Piper) Stapf. (C4, monocot), Triticum aestivum L. (C3, monocot), Amaranthus caudatus L. (C4, dicot) and Helianthus annuus L. (C3, dicot). Water stress reduced the rate of loss of 14C from the leaves of all species following a pulse application of 14CO2, but the effects of stress were most apparent in sorghum and sunflower, the species with the highest control rates of export.
Slower labelling of sucrose, following the application of 14CO2, could explain the reduced rate of export of 14C from stressed wheat leaves, but this would not explain the response in sorghum. An examination of the products of 14CO2 fixation in wheat leaves suggests that the changes in metabolism of 14C under stress may be due to reduced CO2 levels, resulting from stomatal closure. In contrast the change in metabolism of 14C-labelled photosynthate due to water stress in sorghum was very different from that expected in response to reduced CO2 levels.
Prevention of translocation of photosynthate out of a leaf of either wheat or sorghum, by steam killing the tissue at the base of the blade, altered the pattern of labelling of metabolites with 14C following a pulse of 14CO2. However changes in translocation due to reduced export associated with a reduction in growth under water stress did not appear to play a part in the responses observed in these experiments.
Ion Relations of Apple Fruit Tissue During Fruit Development and Ripening. I. Cation Leakage
Authors: Ferguson IB , Watkins CB
Published: January 2006

Leakage of calcium, magnesium and potassium from discs of cortical apple fruit tissue was followed through fruit development and ripening. Leakage of potassium always exceeded that of calcium and magnesium and was little affected by the external presence of the divalent ions. Calcium and magnesium leakage was markedly increased by the external presence of either ion.
In tissue from both freshly picked fruit and that taken from storage, potassium and magnesium leakage increased when the fruit was in an advanced state of senescence, but calcium leakage decreased. During fruit development, leakage of all cations was closely related to availability as expressed in tissue concentration.
There was a marked increase in potassium leakage in association with the respiratory climacteric.
Growth and Developmental Responses of Perennial Ryegrass Grown at Constant Temperature. I. Influence of Light and Temperature on Growth and Net Assimilation
Authors: Hunt WF , Halligan G
Published: January 2006

Perennial ryegrass (Lolium perenne L. cv. 'Grasslands Ruanui') plants were grown spaced in nutrient golution under six levels of irradiance at six constant temperatures (7-33°C) to provide growth response curves to light and temperature over a range of growth conditions. Measurements were restricted to the exponential growth phase.
Plants showed saturation-type growth kinetics with irradiance but the shape of the light response curve was temperature dependent and, conversely, the shape of the temperature response curve was irradiance dependent.
Growth analysis revealed that, at 7, 10, 17 and 20°C, changes in leaf area ratio compensated for changes in net assimilation rate over a range in irradiance for which growth rate was maintained near maximum. At 30 and 33°C, the compensating effect of changes in leaf area ratio was insufficient to maintain near maximum growth at intermediate irradiances. Ontogenetic drifts in specific leaf area and leaf area ratio were compensated for by changes in net assimilation, so that relative growth rate remained constant.
The maximum growth at 20°C resulted from a greater partitioning of dry weight to leaf than at lower temperatures, as well as higher net assimilation than at all other temperatures.
Proteolytic Activity and Nitrate Reductase Inactivation in Maize Seedlings
Authors: Wallace W , Shannon JD
Published: January 2006

The main proteinase in the maize root (proteinase I) has been characterized by its degradation of azocasein, inactivation of nitrate reductase and inhibition by phenylmethylsulfonyl fluoride. An enzyme with these properties has been found only at low activity in the maize shoot. Two other proteinase fractions were identified in the maize shoot by degradation of haemoglobin. These enzymes were inhibited by both p-chloromercuribenzoate and phenylmethylsulfonyl fluoride and are similar to a second proteinase fraction (proteinase II) in the maize root.
Root proteinase II, unlike root proteinase I, does not attack azocasein, but both degrade casein in addition to haemoglobin. The highest activity of proteinase II on casein was in the pH range 5.0-6.0, while high activity of proteinase I on this substrate occurred between pH 5.5 and pH 8.0. The endopeptidase substrate α-N-benzoyl-L-arginine-p-nitroanilide was hydrolysed by proteinase II, but not by proteinase I.
Increase in maize root age from 4 to 14 days was accompanied by a rise in the activity per gram fresh weight of proteinase I and carboxypeptidase I, the increase in the former accounting for the accumulation of nitrate reductase inactivating activity. By contrast, a marked decrease in the activity of proteinase II and carboxypeptidase II occurred in the same period of seedling growth.
Genetic Effects on the Proportions of Conglutin γ and a Subunit of Conglutin β in the Storage Proteins of Lupinus angustifolius L. Seeds
Authors: Oram RN , Gillespie JM , Blagrove RJ
Published: January 2006

The genetic variability in the proportions of conglutin β and γ components of lupin seed storage proteins was explored in F1, F2 and F3 families generated from a cross between two genotypes of Lupinus angustifolius cv. Uniharvest and a white-seeded selection from CPI 47644. The levels of conglutin γ differed by a factor of two in these parents, but varied continuously in the F2 and F3 families, indicating that the parental difference is due to several genes. These parents also differed in the level of a major conglutin β subunit, with a molecular weight of 30 000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the storage globulins from individual F1, F2 and F3 seeds showed that the high level in cv. Uniharvest is controlled by an incompletely dominant allele, Bsc, at one locus, whereas the low level in CPI 47644 (white-seeded) is due to homozygosity for the recessive allele, bsc. The partial dominance of the Uniharvest gene suggests that the locus has a regulatory or processing function, so it has been designated beta subunit controller. F3 families differed significantly in the level of the conglutin β subunit in Bsc/- seeds, indicating that other loci with smaller effects also influence the proportion of this subunit. The proportion of the β subunit in any seed depends largely on its own genotype, and not on the genotype of the maternal plant. The proportion of conglutin γ in the storage proteins varied inversely with the proportion of the β subunit. The implications of these results for the genetic improvement of the biological value of lupin protein are discussed.