bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of fruit load and environmental factors on nitrate reductase activity and on concentration of nitrate and carbohydrates in leaves of eggplant (Solanum melongena)
Authors: Claussen W.
Published: April 2006

Both the in vivo (+ nitrate) nitrate reductase (NR) activity (leaf disks incubated in the presence of KNO3) and the in vivo (− nitrate) NR activity (leaf disks incubated without KNO3) in leaves of eggplant (Solanum melongena L. cv. Bonica) were affected by rapidly growing fruits. Plants with a fruit load showed more pronounced diurnal variation in (+ nitrate) NR activity and higher (− nitrate) NR activity than plants without fruit. The higher (− nitrate) NR activity was accompanied by higher nitrate and lower sucrose and starch contents of leaves. The more pronounced diurnal changes in (+ nitrate) NR activity were paralleled by more pronounced diurnal variation in carbohydrate content of leaves. Fruit removal led to a decrease in both (− nitrate) NR activity and nitrate concentration in leaves, while the carbohydrate content increased. Plants supplied with ammonium instead of nitrate showed only slightly lower (+ nitrate) but no (− nitrate) NR activity. As for plants treated with nitrate, diurnal changes in (+ nitrate) NR activity were most pronounced in leaves of plants with fruit and this again was paralleled by a more pronounced diurnal variation in the carbohydrate concentration in the leaves.

Increasing the oxygen level of the atmosphere to 50% led to a dramatic decrease in the (+ nitrate) NR activity and to an increase in both (− nitrate) NR activity and nitrate concentration, which was accompanied by decreasing carbohydrate contents of the leaves. Low light intensities and extended dark periods caused similar changes in NR activity and nitrate and carbohydrate concentrations in leaves. Increasing the nitrate concentration in the nutrient solution led to a rise in (+ nitrate) and (− nitrate) NR activity, but only the (− nitrate) NR activity paralleled the nitrate concentration in the leaves. This increase in the nitrate concentration was accompanied by a decrease in the carbohydrate content of the leaves.

It is concluded that the level of and the diurnal changes in both (+ nitrate) and (− nitrate) NR activity and the concentration of nitrate in the leaves are dependent upon their carbohydrate status.
Drought stress‐induced changes in the composition and physical state of phospholipids in wheat
Authors: Vigh László , Huitema Hans , Woltjes Jan , van Hasselt Philip R.
Published: April 2006

Seedlings of winter wheat (Triticum aestivum L. cv. Jubilejnaja 50) were grown under normal and dry conditions. Frost resistance (LT50) of 10‐day‐old control seedlings was −6°C. LT50 of the subsequently drought‐stressed leaves shifted to −16°C. In plants of the same physiological age (28 days) but grown without stress, LT50 was −12°C. Phosphatidylcholine accumulated and phosphatidylethanolamine decreased in drought‐stressed leaves. Fatty acid unsaturation of these phospholipids increased with leaf age, independently of water supply. Both ageing and drought stress produced a decrease in the apparent phase separation temperature of isolated total phospholipids as determined by electron spin resonance. The possible role of dehydration‐induced structural changes in the bilayer matrix in triggering adaptive alterations in membrane composition, similar to those observed during cold hardening, is discussed.
Relations between uptake and utilization of NO−3 in Pisum growing exponentially under nitrogen limitation
Authors: Oscarson P. , Larsson C.‐M.
Published: April 2006

The utilization and translocation of nitrogen was investigated in exponentially growing, nitrogen‐limited Pisum sativum L. cv. Marma. The plants were given N daily at exponentially increasing, although suboptimal, relative nitrogen addition rates (RN) calculated to yield a relative increment in N of 0.06 day−1 and 0.12 day−1. After 10 days of NO−3 additions (26 days after sowing), the relative growth rate more or less equaled RN. Uptake of NO−3 was several‐fold higher than the N requirement for the growth rate set by RN. The daily addition of NO−3 was taken up after 7 to 8 h, resulting in a cyclic behaviour in the NO−3 utilization. During the phase of net NO−3 influx, the filling phase (0 to 8 h), in vitro nitrate reductase activity (NR activity) and intracellular levels of soluble N in the root increased. In the phase of no net influx of NO−3 the depletion phase (8 to 24 h), the plants were entirely dependent on stored N. During this phase both in vitro NR activity and intracellular levels of soluble N decreased. Also the calculated actual rate of NO−3 reduction was high in the filling phase, while it was close to zero in the depletion phase. The pattern of these fluctuations indicates that the regulation of NO−3 utilization involves an interplay between transmembrane fluxes of NO−3, the cytosolic NO−3 concentration and NR activity. Cyclic fluctuations in N‐containing compounds were also found in the xylem. Nitrogen was mainly transported as amino acids. The pattern of NO−3 transport in the xylem and the fluctuations in the shoot of in vitro NR activity indicate that a reasoning similar to that for the regulation of NO−3 assimilation in the root also applies for the shoot. The results also indicate a substantial supply of amino acids to the xylem through recirculation from the shoot.
Spectral properties and chromophore rotation of phytochrome bound to substituted Sepharose
Authors: Sundqvist Christer , Ekelund Nils G. A.
Published: April 2006

Brushite purified phytochrome from Avena sativa L. cv. Sol II was bound to phenyl Sepharose, octyl Sepharose, CNBr‐activated Sepharose and to anti‐phytochrome immunoglobulins immobilized on Sepharose. The spectral properties of phytochrome bound to anti‐phytochrome immunoglobulins and to phenyl Sepharose were similar to phytochrome in solution. Phytochrome bound to CNBr‐activated Sepharose or to octyl Sepharose showed reduced Pfr formation after red irradiation. The reversal to Pr with far‐red light was only partial but a further increase at 667 nm took place slowly in the dark. A peak at 657 nm was seen in the difference spectrum between CNBr‐activated Sepharose‐bound phytochrome kept in darkness and the identical sample immediately after a far‐red irradiation.

The change in linear dichroism at 660 nm and 730 nm, induced by plane polarized red or far‐red light, was measured. It was computed that the long‐wavelength transition moment of phytochrome had an average rotation angle of 31.5° or 180°–31.5°. The substrate used for immobilization had a limited effect on the rotation angle. Phytochrome immobilized on CNBr‐activated Sepharose gave an angle of 27.8° and phytochrome immobilized on phenyl Sepharose gave an angle of 32.6°.
Phosphatidylcholine and phosphatidylethanolamine content of partially synchronized rice cell suspension cultures
Authors: Sharpe F. T. , Hall Andrea C. , Schaeffer G. W.
Published: April 2006

Knowledge of phospholipids in relation to cell cycle phases would facilitate the manipulation of tissue culture cells for crop improvement. Rice cells, Oryza sativa L. introduction PI 353–705, were initiated from anther cultures and grown as liquid suspensions. Replicate cultures were harvested for analysis at various time periods up to 21 days. Phosphatidylcholine (PC) and phosphatidylethanolamine (PEA) content rapidly increased 2.5 fold by 3 days, follwed by a progressive decrease in both compounds to 15 days to below initial transfer levels. There was an increase in PC and PEA back to transfer levels from 16 to 21 days. Cells in the linear phase were transferrred 11 days after inoculation to media minus sucrose. Carbohydrate starvation of the cells and subsequent release from inhibition with 3% sucrose resulted in partially synchronized cultures as seen by rapid [3H]‐thymidine incorporation up to 24 h followed by a decrease to a minimum at 72 h. Phosphatidylcholine and phosphatidylethanolamine increased linearly throughout the DNA synthesis period in synchronized cells, reaching a maximum at 48 h and 60 h, respectively. The levels of both compounds 72 h after release from sucrose starvation are only 30% of non‐starved controls 72 h after transfer to fresh media.
Blue light regulation of stomata in wheat seedlings. I. Influence of red background illumination and initial conductance level
Authors: Karlsson Per Erik
Published: April 2006

A red background illumination synergistically increased the sensitivity of the stomatal conductance response to low intensity blue light in wheat seedlings (Triticum aestivum L. cv. Starke II, Weibull). It also saturated the photosynthesis dependent mechanisms so that they did not respond to the low quantum fluence rates needed to activate the blue light mechanism. Thus dual beam experiments provide a suitable experimental approach to study the blue light mechanism for stomatal regulation in the intact leaf. Time course studies indicated that in short time experiments the enhancement effect of the red background light was primarily a result of the increase in conductance level rather than a direct effect of the red light. This was confirmed with experiments where the stomatal blue light response was enhanced due to partial stomatal opening in CO2 free air as well as due to circadian rhythm. During long term experiments the response to blue light gradually decreased. It could then, however, be restored by a simultaneous red background light.
Thigmomorphogenesis: Anatomical, morphological and mechanical analysis of genetically different sibs of Pinus taeda in response to mechanical perturbation
Authors: Telewski Frank W. , Jaffe Mordecai J.
Published: April 2006

Twenty‐three open pollinated families (half‐sibs) and four controlled pollinated families (full‐sibs) of Pinus taeda L. (loblolly pine) were grown in a greenhouse and analyzed for changes induced by mechanical perturbation (MP). These changes included inhibition of stem and needle elongation, bracing of branch nodes, and increased radial growth in the direction of the MP. Inhibition of stem elongation was the least variable feature measured. Leaf extension and stem diameter were highly variable between half‐sibs. MP induced increased drag in greenhouse grown P. taeda in wind‐tunnel tests. In P. taeda, MP induced decreased flexibility and increased elasticity and plasticity of the stem. The increased radial growth of the stems overrode the increase in elasticity, resulting in an overall decrease in flexibility. MP trees had a higher rupture point than non‐MP controls. Increased radial growth is a result of more rapid cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decreased leader growth is partly due to a decreased tracheid length in response to MP.
Thigmomorphogenesis: The role of ethylene in the response of Pinus taeda and Abies fraseri to mechanical perturbation
Authors: Telewski Frank W. , Jaffe Mordecai J.
Published: April 2006

Ethylene production was monitored for 48 h in two half‐sibs of Pinus taeda L. grown in the greenhouse and given mechanical perturbation (MP) by flexing; and for 22 h in Abies fraseri (Pursh) Poir, grown in the field and exposed to wind‐mediated MP. Both species produced a peak of ethylene 18 h after MP. Seedlings of P. taeda exposed to MP for the duration of the growing season (preconditioned) produced less ethylene compared to non‐MP controls, with a peak production at 8 h. One half‐sib which responded to MP by an increase in radial growth produced 16 times more ethylene than another half‐sib which had no significant change in radial growth. Preconditioned A. fraseri produced no significant quantities of ethylene after MP. The production of wound ethylene appears to be different from MP‐induced ethylene. When an ethylene‐generating solution was applied to P. taeda seedlings, it mimicked many of the morphological and mechanical characteristics of MP seedlings. The putative role of ethylene in the thigmomorphogenetic response is addressed.
Light‐mediated changes in the plastidic phosphorylase patterns in shoots of Pisum sativum
Authors: Steup Martin , Schächtele Christoph , Melkonian Michael
Published: April 2006

α‐1,4‐Glucan phosphorylase (EC 2.4.1.1) forms from light or dark grown shoots of Pisum sativum L. cv. ‘Kleine Rheinländerin’ have been studied using various electrophoretic techniques. The phosphorylase patterns of green and etiolated shoots differed. Etiolated shoots contained two enzyme forms, one residing inside and the other outside the etioplast; this was shown by electrophoresis of extracts of isolated etioplasts. Purity and intactness of the organelle preparation were ascertained by electron microscopy. Light‐grown shoots contained, in addition to these two enzyme forms, a third phosphorylase which appears to be chloroplast‐specific. The two plastidic phosphorylase forms differed slightly in their apparent molecular masses (as determined by non‐denaturing polyacrylamide gel electrophoresis) and in their affinities towards branched polyglucans (as revealed by affinity electrophoresis). The apparent affinity of the extrachloroplastic phosphorylase form to these polyglucans was orders of magnitude higher than that of the two plastidic enzyme forms. The development of the chloroplast‐specific phosphorylase pattern is under photocontrol. Investigations performed with red or far‐red illuminated wild‐type plants and with a pale mutant which has a highly reduced pigment and thylakoid content suggest that this photocontrol is mediated by phytochrome.
Isomers of zeatin and zeatin riboside in clubroot tissue: evidence for trans‐zeatin biosynthesis by Plasmodiophora brassicae
Authors: Müller Peter , Hilgenberg Willy
Published: April 2006

Cytokinin‐like substances in both healthy and infected (Plasmodiophora brassicae) Wor. strain S) roots of Brassica campestris L. ssp. pekinensis cv. Granat have been tentatively identified and quantified by HPLC. The isomers of the cytokinins could be seperated on a reversed phase column using a gradient elution with increasing amounts of methanol. Secondary plasmodia were isolated mechanically from Plasmodiophora brassicae infected roots. The time course of adenine uptake and its conversion to cytokinins were investigated. Evidence is presented for the incorporation of [U‐14C]‐adenine into trans‐zeatin by secondary plasmodia.
The use of colloid gold labelling in the detection of plasma membrane from symbiotic and non‐symbiotic Glycine max root cells
Authors: Ostrowski Elke D. , Mellor Robert B. , Werner Dietrich
Published: April 2006

Glycine max L. Merr. cv. Maple Arrow protoplasts were prepared from both tissue‐cultured root cells and symbiotically‐infected (fix+) nodule cells. Whilst both cell types showed glucan synthetase II (GS II; EC 2.4.1.29) activity, neither cell type, whole or gently disrupted, showed glucan synthetase I activity. After sucrose density gradient centrifugation one of the several GS II activity peaks co‐sedimented with the single radioactive particulate peak from [125I]‐labelled protoplasts at 1.14 g ml−1. This peak is presumed to be the plasma membrane peak because labelling of protoplasts with colloidal gold prior to disruption moved the 125I peak and the corresponding glucan synthetase II activity into denser regions of the gradient, leaving endoplasmic reticulum‐contaminating IDPase (EC 3.1.3.31) and other glucan synthetase II peaks unmoved. Results are discussed in relation to various strategies of plasma membrane isolation.
Action spectra for chlorophyll formation during greening of wheat leaves in continuous light
Authors: Virgin Hemming I.
Published: April 2006

The contents of Chl a and Chl b in dark‐grown leaves of wheat (Triticum aestivum L. cv. Starke II, Weibull) irradiated for 20 h with light of different wavelengths and intensities have been measured. The amount of Chl b formed revealed a higher maximum in the Chl b/Chl a ratio for light most strongly absorbed by the phytochrome system and giving a high [Pfr]/[Ptot] ratio. This indicates a stronger enhancing effect of Pfr on Chl b formation than on Chl a formation. Similarities between action spectra for Chl a and b formation indicate that Chl b originates from Chl a. A comparatively high effectiveness of light within the wavelength range 500–550 nm as compared to the action spectrum for PChl→Chl phototransformation shows that PChl636, in addition to PChl650, takes part in the greening process.
Senescence in oat leaf segments under hypobaric conditions
Authors: Veierskov Bjarke , Kirk Hanne Grethe
Published: April 2006

The physiological effects of storing plants under hypobaric conditions were studied using oat (Avena sativa L. cv. Victory) leaf segments as a test system. The segments from seven day old plants were floated on water and stored in darkness at 12°C, 1.6 kPa or at 25°C, 6 kPa. Low temperature or hypobaric conditions delayed senescence, whereas the combination arrested the syndrome at an early stage. One of the effects of low pressure was to force the stomata open. The hormones abscisic acid and kinetin, which affect the stomatal aperture and also senescence, did not show any effect in hypobarically stored plant material. The stomata were forced open in darkness when the pressure was lower than 77 kPa and opening time was 8 h. The senescence syndrome in hypobarically stored segments developed similar to those treated with kinetin at 101 kPa.
Fusarium‐induced vascular gels from banana roots — a partial chemical characterization
Authors: VanderMolen Gail E. , Labavitch John M. , DeVay James E.
Published: April 2006

Xylem vessels often become occluded when plants are subjected to pathogen or abiotic stresses. The composition of these vessel‐obstructing gels has never been directly analyzed. Roots of wilt‐resistant (Valery) and susceptible (Gros Michel) cultivars of banana (Musa acuminata L.) trees were inoculated with Fusarium oxysporum Schlect f. sp. cubense Snyd. and Hans, and vascular gels were collected 5 days later. Gas chromatographic and colorimetric analyses indicate that the gels are rich in neutral sugars (arabinose, glucose and xylose) and uronic acids that are also found in the cell walls of the host. The idea that these vessel occlusions are composed, at least in part, of carbohydrates digested from the cell walls of the host is discussed.
Sucrose release from soybean leaf slices
Authors: Anderson James Michael
Published: April 2006

The release of photosynthate from leaf slices of soybean [Glycine max (L.) Merr. cv. Ransom II], to a bathing medium was studied to ascertain how p‐chloromercuribenzenesulfonic acid (PCMBS) can both stimulate and inhibit sucrose release. Soybean leaf slices released photosynthate to a bathing medium at a rate that was approximately linear with time. The photosynthate released was about 20% ionic and 80% non‐ionic, and sucrose represented about 75% of the total. Removal of Ca2+ from the medium increased the rate of release of all fractions, but amino acid release showed the largest increase. Sucrose was released at a rate estimated to be about 20% of the normal transport rate in intact leaves. The rate of sucrose uptake from 5 mM sucrose into soybean leaf slices was optimum at pH 6.3, and the rate of sucrose release was lowest at the same pH. However, sucrose uptake was found to be insignificant during release experiments. Sucrose release, but not amino acid release, was inhibited 75% by 1 mM PCMBS.

The data support two components of sucrose release in leaves. The first is insensitive to the addition of PCMBS. This component probably represents leakage from phloem tissue. The second component is inhibited by PCMBS and probably represents release from the mesophyll. By comparing sucrose release from leaf slices of 12 different species of plants, 2 groups were found. In the first group, sucrose release was inhibited between 60 and 80% by PCMBS, and in the second group between 0% and 40%. The difference in the two groups can be explained by a relative difference in the size of the two components of sucrose release for each species.
Effects of salinity on ultrastructure and ion distributions in roots of Plantago coronopus
Authors: Harvey Diana M. R. , Stelzer Ralf , Brandtner Regina , Kramer Detlef
Published: April 2006

Root cell structure and ion distributions have been examined in Plantago coronopus L. grown in the absence or presence of 110–125 mM NaCl. In both salt‐treated and control plants, the inner cortical cells often had membrane whorls projecting into the vacuoles. These structures appeared to be continuous with the endoplasmic reticulum. In roots grown in saline conditions, the parenchyma cells surrounding the xylem vessels showed very uneven wall thickenings and corrugations.

In control roots, X‐ray microanalysis of frozen hydrated bulk specimens showed that there were three levels at which discrete reciprocal changes in Na/K levels occurred: the outer‐middle cortex, the endodermis and the xylem vessels. The first two of these were associated with high Mg, and the last with high Ca percentages. In the salt‐treated roots, the overall Cl percentages were much lower than in the culture medium, being severely limited at the epidermis. Na and, to a lesser extent, Cl percentages decreased radially inwards, while those of K increased. The Na:Cl ratio decreased radially inwards across the cortex. The analytical validity of the data is discussed in relation to differential elemental losses during analysis, specimen topography and analytical spatial resolution. The results are interpreted in terms of the proposed involvement of Mg2+‐ and Ca2+‐ATPases in ion uptake and regulation of translocation in Plantago coronopus roots.
Phytochrome action and frost hardening in black spruce seedlings
Authors: D'Aoust A. L. , Hubac C.
Published: April 2006

Black spruce [Picea mariana (Mill.) B.S.P.] development is sensitive to photoperiod. To date the implication of photoperiod, and especially phytochrome, in the frost hardening process of black spruce has not been fully tested. Two light fluence rates, night interruption of darkness, and red vs far‐red radiation treatments were applied to black spruce seedlings, followed by freezing at –6°C. Parallel to the freezing test, growth measurements, bud formation and the xylem water potential estimates of the seedlings were done. While dry weight accumulation depends on the irradiation energy level, bud formation and freezing tolerance are photoperiodically sensitive. Furthermore, bud formation and frost hardening are dependent upon whether phytochrome is in the active form or inactive form, as demonstrated by the positive effect of short days, far‐red radiation and the reversal of the red effect by far‐red radiation. Also, xylem water potential appears to be influenced by short day and far‐red conditioning.
Ca2+ ‐dependent protein phosphorylation in germinated pollen of Nicotiana alata, an ornamental tobacco
Authors: Polya Gideon M. , Micucci Vito , Rae Anne L. , Harris Philip J. , Clarke Adrienne E.
Published: April 2006

The 40 000 g supernatant and 40 000 g pellet from extracts of germinated pollen of Nicotiana alata Link et Otto contain protein kinase activity which catalyzes the phosphorylation of histones, casein and a range of endogenous polypeptides. Phosphorylation of certain low‐molecular‐weight, casein‐derived polypeptides is activated at low (12–37 μM) and partially inhibited at higher (540 μM) concentrations of free Ca2+. Histone phosphorylation is largely Ca2+‐dependent and is activated by 540 μM free Ca2+. No activation of protein phosphorylation by micromolar concentrations of calmodulin is found, but phenothiazine‐derived calmodulin antagonists markedly stimulate protein phosphorylation.
Growth and accumulation of N, K+, Ca2+ and Mg2+ in barley exposed to various nutrient regimes and root/shoot temperatures
Authors: Jensén Paul , Perby Harald
Published: April 2006

Six cultivars of spring barley (Hordeum vulgare L. cvs Salve, Nümberg II, Bomi, Risø 1508, Mona and Sv 73 608) were grown in water culture for three weeks with various combinations of mineral supply and differential roots/shoot temperatures during the growth period. Most important for growth and accumulation of N, K+, Ca2+ and Mg2+ was the mineral supply, followed by the root temperature and the choice of cultivar. Treatments with low mineral supply or low root temperature induced a uniform reduction in growth and accumulation of the ions studied. The effects of low mineral supply and low root temperature on growth and N accumulation was additive, which indicates that these factors exert their influence independently of each other.

Roots grown at 10°C were smaller and Rb+(86Rb) influx was higher than in roots grown at 20°C. It is suggested that the control of Rb+(86Rb) influx is affected by the root temperature and the age of the plants. The higher 86Rb+ (86Rb) influx into the low temperature roots could not compensate for the smaller root size. However, the lower total mineral accumulation made up for the needs of the smaller plants and cannot explain the reduction in growth.
Variation in growth and accumulation of N, K+, Ca2+ and Mg2+ among barley cultivars exposed to various nutrient regimes and root/shoot temperatures
Authors: Perby Harald , Jensen Paul
Published: April 2006

Six cultivars of barley (Hordeum vulgare L., cvs Salve, Nürnberg II, Bomi, Risø 1508, Mona and Sv 73 608) were exposed for three weeks to combinations of high and low mineral supply and differential root/shoot temperature. For all the parameters tested [fresh and dry weights, contents and levels of N, K+, Ca2+ and Mg2+, and influx of Rb+(86Rb)] the cultivar differences were influenced by the mineral supply, the root temperature and the age of the plants.

The cultivar differences in N nutrition of three‐week‐old plants could partly be attributed to variation in root size, uptake of N and in use‐efficiency of the element. The cultivar variation in root‐shoot partitioning of N was small, except when low mineral supply was combined with a low root temperature. Similarly, cultivar differences in contents of K+, Ca2+ and Mg2+ were influenced by variation in uptake, use‐efficiency and root/shoot partitioning of the elements. Low root temperature increased cultivar variation in K+, Ca2+ and Mg2+ partitioning.

The modern cultivar Salve was compared with Nürnberg II, which is derived from a German land race. Nürnberg II performed better than Salve when low root temperature and restricted mineral supply were combined. Otherwise Salve grew better, partly due to a more efficient use of N.

Two high‐lysine lines, Risø 1508 and Sv 73 608, were compared with their mother lines Bomi and Mona. The differences obtained revealed no general effect of the high‐lysine genes on growth and mineral nutrition of up to three‐week‐old barley plants.
Isolation of ribulose bisphosphate carboxylase‐oxygenase from non‐hardened and hardened needles of Pinus sylvestris
Authors: Gezelius Kerstin , Widell Anna
Published: April 2006

Ribulose bisphosphate carboxylase‐oxygenase, RuBP carboxylase (EC 4.1.1.39), was purified from non‐hardened and hardened needles of Pinus sylvestris L. Needles were collected from pine seedlings cultivated in nutrient solution in a climate chamber from seedlings grown outdoors, and from a tree in a natural stand. The enzyme was isolated from crude extracts through quantitative precipitation in polyethylene glycol 4000 and MgCl2, followed by sucrose gradient centrifugation in a fixed angle rotor. The purified enzyme seemed homogeneous by the criterion of (sodium dodecylsulphate) polyacrylamide gel electrophoresis. Contamination by nucleic acids was negligible. The RuBP carboxylase protein content of the gradient fractions was estimated as A2801 cm× 0.61 mg ml−1. Carboxylase activities were determined in a radioactive assay at 25°C. The specific activity of RuBP carboxylase isolated from non‐hardened needles was approximately 1 μmol CO2 (mg protein)−1 min−1. For enzyme isolated from hardened needles collected during winter the specific activity was somewhat lower due to loss of enzyme activity during the preparation. The described two‐step procedure provides a means for quantitation of the RuBP carboxylase protein in pine needles during all seasons.
Changes in fatty acid and lipid content in callus and protoplasts of Parthenocissus tricuspidata and Petunia hybrida during culture
Authors: Passaquet C. , Teodorescu‐Ionescu N. , Zuily‐Fodil Y. , Pham Thi A. T.
Published: April 2006

Protoplasts isolated from callus cells of Petunia hybrida L. and Parthenocissus tricuspidata L. crown gall were used in order to correlate the fatty acid and lipid contents and composition during culture with the ability or unability of the cells to divide. Freshly isolated protoplasts were characterized by a decrease in fatty acids, galactoli‐pids and phospholipids, an increased saturation of the fatty acids of the phospholipids and higher weight percentages of neutral lipids and phosphatidic acid. During culture, fatty acids and phospholipid increased in dividing protoplast of Petunia but not in non‐dividing protoplasts of Parthenocissus. The findings may imply a two‐stage response to isolation stresses: the first step being lipid degradation and the second lipid biosynthesis.
Growth and competitive ability of a highly plastic and a marginally plastic genotype of Plantago major in a fluctuating environment
Authors: Poorter Hendrik , Lambers Hans
Published: April 2006

The hypothesis was tested that a physiologically highly plastic genotype is better adapted to a fluctuating environment than a marginally plastic genotype. For that purpose, two inbred lines of Plantago major L., which differ in their degree of physiological plasticity, were grown in tubes with quartz sand, either singly or in combination. Four treatments were applied with a different frequency of fluctuations in nutrient level. When grown singly, the relative growth rate of both genotypes reacted in the same way to the different treatments. The genotypes showed similar reactions when grown in monoculture with two plants per tube. In mixed culture (also two plants per tube) the response was different. With increasing frequency of fluctuations in nutrient level, the inbred line with the high plasticity grew faster at the expense of the marginally plastic line, whose growth was reduced.
Effect of SO2, on the activity of adenosine 5′‐phosphosulfate sulfotransferase from spruce trees (Picea abies) in fumigation chambers and under field conditions
Authors: Tschanz Andreas , Landoit Werner , Bleuler Peter , Brunold Christian
Published: April 2006

The effect of SO2 on adenosine 5′‐phosphosulfate sulfotransferase activity and various other parameters of needles from spruce (Picea abies L.) was studied using potted grafts in outdoor fumigation chambers and trees growing near a factory. In summer and autumn fumigation of grafted spruce, SO2, decreased the extractable activity of adenosine 5′‐phosphosulfate sulfotransferase to 12–50% of the controls, and reduced the amount of 35S from sulphate incorporated into protein by excised branches to a comparable degree. SO2 treatment in January and February inhibited the increase in adenosine 5′phosphosulfate sulfotransferase activity measured in the controls during this time. ATP‐sulfurylase activity was less affected by SO2. fumigation. In trees growing near a factory with high SO2. emission, the activity of adenosine 5′‐phosphosulfate sulfotransferase was about 35% of that of trees from a control area. The low enzyme activity was correlated with a high content of sulfate and compounds containing thiol groups.
Corn chloroplast development in weak fluence rate red light and in weak fluence rate red plus far red light
Authors: Eskins Kenneth , McCarthy Susan A. , Dybas Linda , Duysen Murray
Published: April 2006

Corn (Zea mays L. cv. OP Golden Bantum) was grown under various low irradiances of red light (Pfr/Ptot∼ 0.8) and under high irradiance far‐red light containing low amounts of red light (Pfr/Ptot∼ 0.05–0.15). Parameters of chloroplast development such as pigments, membrane polypeptides and infrastructure were compared among the various light sources. Results indicate that the requirement for phytochrome is saturated at low ratios of Pfr/Ptot (<5% Pfr). When the phytochrome requirement is saturated, pigment synthesis assumes major importance and chloroplasi development is directly related to red light irradiance.
Growth substance sensitivity: The need for clearer ideas, precise terms and purposeful experiments
Authors: Firn Richard D.
Published: April 2006

The idea that growth substance‐responsive cells might not have a fixed capacity to respond to a growth substance is not new, but it is an idea which has received much greater consideration in the last few years, largely as a result of a series of articles by Trewavas (1981a,b, 1982, 1983). Despite the fact that no thorough attempt has been made to explore this concept experimentally, it seems to have been accepted as a valid and useful one, even by some of Trewavas's critics (Cleland 1983). However, the term “change in growth substance sensitivity” can be shown to have several meanings, each with a very different underlying physiological mechanism. If the concept is to be developed into a productive model of the way in which plant growth and development are regulated under certain circumstances, it will be necessary to be more precise. New terms are proposed to describe some of the factors which could contribute to changes in the sensitivity of a cell to a growth substance. It is argued that much more purposeful experiments will be needed in order to establish whether changes in sensitivity do accompany some developmental processes and to probe the exact nature of these changes.
Photosensitivity of Rumex obtusifolius seeds for stimulation of germination: Influence of light and temperature
Authors: Kendrick Richard E. , Heeringa Gerda H.
Published: April 2006

A population of Rumex obtusifolius L. seeds imbibed for 24 h at 25°C exhibits a sigmoid logarithmic fluence‐response relationship for stimulation of germination by red light (R), 11.0 μmol m−2 being necessary for 50% of the response. After 24 h imbibition at 35°C the fluence‐response relationship for stimulation of germination by R is biphasic. For 50% response the very sensitive phase (very low fluence‐response) requires 4.7 − 10−2μmol m−2 whereas the less sensitive phase (low fluence‐response) requires 4.0 μmol m2. A few seconds of far‐red light (FR) satisfies the germination requirement of the sensitive seeds after 24 h at 35°C. However, a longer period of FR (2 h) results in low germination. The fluence‐response relationship for induction of these seeds by R is sigmoid, 4.8 μmol m−2 being necessary for 50% response, demonstrating that 2 h FR desensitizes the sensitive proportion of the seed population induced by 24 h at 35°C. A proportion of the seed population can be further sensitized by 60 min at 35°C following this desensitization.
Conditions of induction of secondary dormancy in apple after breaking of primary dormancy by anaerobiosis and low temperature
Authors: Bulard C.
Published: April 2006

Dormant embryos of Pyrus malus L. cv. Golden delicious, isolated from the fruits at harvest time or after a few months storage at 10 to 15°C, were kept under anaerobic conditions in order to eliminate primary dormancy. Germination tests were then carried out at different temperatures, using three modes of culture depending on the nature of the contact between the embryo and the medium. In CM the distal part of the two cotyledons was immersed in the medium. In RM only the embryonic axis was immersed. In C/2M the embryo was placed flat on the medium, the radicle and the external surface of one cotyledon being in contact with it.

Results showed that primary dormancy was released progressively depending on the duration of the anaerobic treatment. After a treatment of 11 or 13 days the last symptoms of primary dormancy were only apparent when germination tests were carried out at high temperatures (26–30°C) or in CM mode of culture.

When the embryos were kept at 4°C during 3 months inside the fruits, subsequent germination was inhibited at high temperature and in CM mode of culture. When the embryos were kept under anaerobic conditions (7 days) after the chilling treatmem inside the fruits, germination was no longer inhibited. It is concluded that the inhibition of germination at high temperature and in CM mode of culture is due to the persistence of traces of primary dormancy. Therefore, these conditions do not seem to induce secondary dormancy in apple embryos.

After elimination of primary dormancy by anaerobiosis. only application of (±) abscisic acid (3.8 and 19 μM) inhibited germination. These results support the idea that ABA is an important factor in the induction of dormancy. However, the question remains whether this secondary embryo dormancy has the same characteristics as the original primary dormancy.
The joint action of phytochrome and alternating temperatures in the control of seed germination in Dactylis glomerata
Authors: Probert R. J. , Smith R. O.
Published: April 2006

The promoting effect of light and alternating temperatures on the germination of seeds of three contrasting populations of Dactylis glomerata L. was studied. Irradiation treatments using broad band low irradiance light sources resulted in red/far‐red reversible effects, demonstrating the involvement of phytochrome in germination control. Reduction of germination by far‐red below the level of a dark control indicated the presence of high pre‐existing levels of the active form of phytochrome (Pfr) in some individuals. The capacity for dark germination at 21/11°C (12 h/12 h) was shown to be dependent on Pfr. Although some individuals were capable of germination at constant temperatures following red irradiation, in most seeds germination was dependent on the presence of Pfr and alternating temperatures. Some individuals responded to a single red irradiation, although a large proportion of seeds required high levels of Pfr to be maintained for long periods. Previously published dose response curves for alternating temperatures and a measured dark reversion time of 48 h for Pfr established by a single 60 min red irradiation, provided firm evidence of a direct correlation between the requirements for repeated irradiation and number of alternating temperature cycles.
The effects of different soil water potentials, temperature and salinity on germination of seeds of the desert shrub Zygophyllum dumosum
Authors: Agami Moshe
Published: April 2006

The effects of different soil water potentials, temperature and NaCl concentration on seed germination of Zygophyllum dumosum Boiss., a common shrub in Israeli deserts, was investigated. Seeds had to be exposed to constant field capacity conditions (–0.0316 MPa) for a minimal period of two days before germination could start. Maximal germination under such conditions occurred after four days or more. Under simulated conditions of gradual dehydration of the soil, seeds were inhibited either at low soil water potentials (–0.10 to –10.00 MPa) or at high ones (–0.002 to –0.0398 MPa). Germination of Z. dumosum was independent of temperature in the range of 10–25°C, but strongly inhibited at 30 and 35°C. At 20°C germination was inhibited by salinity of the medium but still occurred (0.5%) even at a concentration of 0.5 M NaCl.
Polyadenylated RNA metabolism and loss of vigour and viability in germinating wheat embryos
Authors: Smith C. A. D. , Rushton P. , Bray C. M.
Published: April 2006

The quiescent wheat (Triticum aestivum L. cv. Hobbit) embryo contains polyadenylated RNA species (polyA+ RNA, presumptive mRNA species) which are rapidly degraded upon water imbibition by the embryo even when the embryo has lost viability. The level of polyA+ RNA species in the quiescent embryo does not reflect the vigour or viability rating of the seed lot. Embryos which have lost viability appear to have lost the capacity for de novo transcription of polyA+ RNA species during the hours following water imbibition by the embryo. Embryos from seed lots of differing vigour ratings can be distinguished by their very different patterns of polyA+ RNA metabolism during germination at a sub‐optimal temperature. In embryos of reduced vigour there is a delayed onset of degradation of polyA+ RNA species during germination at 10°C and a reduced rate of polyA+ RNA synthesis through the first 6 h of germination compared with these processes in high vigour embryos. However, at later germination stages embryos of reduced vigour synthesise polyA+ RNA species at rates similar to those found in high vigour embryos yet newly synthesised polyA+ RNA species accumulate in embryos of reduced vigour only to a level which is 50% of that found in high vigour embryos of comparable viability. Results suggest that additional lesions affecting the stability and/or turnover of the messenger ribonucleo‐protein complex containing polyA+ RNA are present in embryos of reduced vigour at later stages of germination at a sub optimal temperature.
Seed coat imposed dormancy: Histochemistry of the region controlling onset of water entry into Sida spinosa seeds
Authors: Egley Grant H. , Paul Rex N. , Lax Alan R.
Published: April 2006

Fresh Sida spinosa L. seeds do not imbibe water and germinate because the seed coat is impermeable to water. Seeds imbibe water when a portion of the coat in the chal‐azal area separates from an underlying layer of subpalisade cells. Thin‐walled subpalisade cells are limited to the area beneath the chalazal area. Palisade cells in the coat region that become permeable are tall, only lightly lignified, contain abundant hemicelluiose and have large cell lumena. Palisade cells in regions of the coat that remain impermeable to water are short, have heavily lignified thick walls, small cell lumena and are tightly packed. We propose that Sida spinosa seed coat dormancy is released when moisture eventually reaches the hygroscopic hemicellulose deposits in cell lumena in the lightly lignified palisade cells of the chalazal region. The subsequent expansion of the palisade cells causes the thin‐walled subpalisade cells to break, resulting in separation of palisade from subpalisade cells and free passage of water through the exposed surface to the embryo, culminating in germination.
Clover root exudate contains a particulate form of the lectin, trifoliin A, which binds Rhizobium trifolii
Authors: Truchet Georges L. , Sherwood John E. , Pankratz H. Stuart , Dazzo Frank B.
Published: April 2006

A particulate form of the lectin, trifoliin A, has been isolated from the root exudate of axenically grown seedlings of white clover (Trifolium repens L. cv. Louisiana Nolin). The majority of trifoliin A active in binding to R. trifolii 0403 was sedimented from root exudate by centrifugation at 15 000 g for 30 min, indicating that it was particulate. Immunofluorescence, electron and immunoelectron microscopy using antibody prepared against trifoliin A from seeds, suggested that trifoliin A was associated with the particles in root exudate that bound specifically to the acidic capsular polysaccharides of Rhizobium trifolii 0403. Electron microscopic examination also showed that trifoliin A‐colloidal gold conjugates bound to these same particles, indicating that they also have affinity for the lectin. The particles could be dislodged from intact seedlings by vigorous shaking in isotonic plant growth medium. Isolated particles fractionated by ultracentrifugation through a metrizamide gradient had a mean density of 1.12 g cm‐3. These isolated particles retained the ability to bind to R. trifolii 0403 as shown by immunofluorescence using anti‐trifoliin A antibody. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the isolated particles are a mixture of proteins including one with an approximate molecular weight of trifoliin A. The protein which electrophoretically comigrated with trifoliin A also reacted with anti‐trifoliin A antibody by western blot analysis, confirming that it was trifoliin A. The protein composition of the isolated particles did not reflect the total protein composition of the root exudate, which was far more complex. These studies indicate that the majority of trifoliin A which can bind to R. trifolii in root exudate of white clover seedlings is associated with electron‐dense particles, and that a major early interaction between R. trifolii and clover roots involves the binding of these particles containing trifoliin A to acidic polymers on the bacterial cell surface.
Lipid and pigment composition of a chlorophyllb‐deficient mutant ofChlamydomonas reinhardii
Authors: Eichenberger Waldemar , Boschetti Arminio , Michel Hans Peter
Published: April 2006

Lipids and pigments of the chlorophyllb‐deficient mutant pg‐113 and the parent strain (ps) ofChlamydomonaswere analysed and compared. Monogalactosyldiglyceride, digalactosyldiglyceride, diacylglyceryl(N, N, N‐trimethyl)homoserine, sulfoquinovosyldiglyceride, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol were found as major lipid components. While the lipid patterns were qualitatively and quantitatively almost the same in the two strains, the C16/C18fatty acid ratios were different, 0.85 in the mutant and 1.11 in the parent strain. Furthermore, the relative amounts of C16‐ and C18‐monoene fatty acids were slightly enhanced and the C18‐trienes slightly reduced in the mutant. In the parent strain, chlorophyllsaandb, α‐ and β‐carotene, lutein, violaxanthin, neoxanthin and loroxanthin were detected by HPLC. In the mutant, similar pigments were found, except that only traces of chlorophyllband a reduced amount of neoxanthin were present. Since no chlorophyll‐protein complex CP II could be detected in the mutant by electrophoresis, the possible interrelationships between pigment deficiency and alteration of chlorophyllprotein complexes are discussed.
Promotory and inhibitory effects of activated charcoal on microspore embryogenesis in Datura metel
Authors: Babbar Shashi B. , Gupta Shrish C.
Published: April 2006

Activated charcoal (AC, 0.25–1%) added to Murashige and Skoog medium supplemented with coconut milk (CM, 15%), inhibited the androgenic response of Datura metel anthers excised from fresh as well as cold pretreated buds (3 days at 3±2 °C). The inhibitory effect of AC was directly proportional to its concentration for fresh as well as cold pretreated explants. This indicated that either AC itself is toxic or reduces the response by adsorbing some substance(s) from explants and/or from the medium. It was thought that AC is probably reducing the response by adsorbing some active component(s) of CM. This possibility was tested by studying the effect of different concentrations of CM in the presence (1%) and absence of AC. It was found that AC reduced the response only in the presence of CM, which was below the level recorded for anthers incubated on basal medium alone. Individually, both CM and AC enhanced the plantlet yield.
Ethylene production from 1‐aminocyclopropane‐1‐carboxylic acid in vitro: A mechanism for explaining ethylene production by a cell‐free preparation from pea epicotyls
Authors: Stegink Steven J. , Siedow James N.
Published: April 2006

The generation of ethylene from 1‐aminocyclopropane‐1‐carboxylic acid (ACC) added to a cell‐free preparation from etiolated pea (Pisum sativum L. cv. Alaska) epicotyls was found not to be due to a specific ACC oxidase or to oxygen radicals. Rather, endogenously produced H2O and manganese ions are coupled in a reaction sequence which produces ethylene from ACC. In a model system, H2O and Mn2+ converted ACC to ethylene under conditions similar to those in the pea preparation. Ultrafiltration of the pea preparation inhibited ethylene production, but it could be reconstituted either by adding an H2O2‐generating system to the ultrafiltrate or Mn2+ to the retentate. H2O2‐generating systems could reconstitute ethylene formation in a heat‐inactivated cell‐free sample while the loss of ability to produce ethylene upon dialysis of the pea preparation correlated with the loss of Mn2+ from the sample. Studies using cell‐free preparations to investigate ethylene synthesis should take care to exclude the possible involvement of H2O2 and Mn2+.