bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromatography of acid phytohormones on columns of Sephadex LH‐20 and insoluble poly‐N‐vinylpyrrolidone, and application to the analysis of conifer extracts
Authors: Sandberg Göran , Dunberg Arne , Odén Per‐Christer
Published: April 2006

The chromatographic behaviour of abscisic acid (ABA), indole‐3‐acetic acid (IAA), phenylacetic acid (PAA), and gibberellins A1, A4, A8, A9, A13 and A20 on columns of Sephadex LH‐20 and insoluble poly‐N‐vinylpyrrolidone (PVP) eluted with buffers of different pH values is described. PVP shows considerable batch differences that must be carefully checked. Chromatography of acidic ethyl acetate‐soluble fractions of Scots pine (Pinus sylvestris L.) extracts at pH 4.5 resulted in great losses of phytohormones, due to poor solubility of the extracts. If the extracts were applied to the column dissolved in buffer of pH 7.5, subsequent elution at pH 4.5 was possible with only small losses. The performance of the chromatographic column was strongly affected by the application volume. A combined PVP/Sephadex LH‐20 column eluted at pH 4.5 allows remarkable purification of pine and spruce (Picea abies (L.) Karst.) extracts, collection of IAA in a fraction that can be directly analyzed by e.g. the indolo‐α‐pyrone method, and collection of another fraction containing ABA, PAA and probably most of the known C19‐gibberellins; whereas the C20‐gibberellin A13 is eluted later (with IAA).
Characterization of glutamine synthetase in the apple
Authors: Kang Seong‐Mo , Titus John S.
Published: April 2006

Glutamine synthetase (l‐glutamate: ammonia ligase, ADP‐forming, EC 6.3.1.2) in bark tissue of the apple (Malus domestica Borkh. cv. Golden Delicious) was partially purified and characterized. The Mn2+‐ and Mg2+‐dependent activities were maximal at pH 7.2 and 7.5, respectively. The enzyme was almost completely inactivated within two weeks at 0°C. Both Mg2+ and β‐mercaptoethanol were effective in stabilizing the enzyme during storage. The enzyme was protected from thermal inactivation at 60°C by the addition of Mg2+ and ATP. One‐tenth mM phenylmercuric acetate inhibited the Mg2+‐dependent activity by 50%. Equimolar dithiothreitol protected the enzyme from this inactivation. The Km values of the enzyme were 0.27, 7.35, and 0.69 mM for ATP, glutamate, and NH2OH, respectively. The constant for NH+4 was an order of magnitude higher in the presence of Mn2+ than Mg2+.

When the amino acids were externally added to the reaction mixtures, the measurement of Pi exhibited a higher degree of enzyme inhibition than the measurement of γ‐glutamyl monohydroxamate (GHA). Ten mM histidine inhibited the Mg2+‐ and Mn2+‐dependent activities by 26 and 45% respectively. Twenty mM aspartate (d,l‐form) inhibited the enzyme 30% in the presence of either Mg2+ or Mn2+. Aspartate (Mg2+‐dependent) and histidine (Mn2+‐dependent) inhibited the enzyme competitively with respect to glutamate, the estimated inhibition constants being 17.6 and 1.6 mM, respectively. At 10 mM, amino acids such as tryptophan, arginine, alanine and citrulline inhibited enzyme activity from 1 to 18%. Glutamine stimulated the Mg2+‐dependent activity 25% at 25 mM when GHA was measured. Glutamine above 32 mM inhibited the enzyme.
In vivo protection of urease of Evernia prunastri by dithiothreitol
Authors: Cifuentes Blanca , Estévez M. Pilar , Vicente C.
Published: April 2006

Urease is induced by urea in Evernia prunastri (L.) Ach. thallus, but the enzyme becomes inactive from the fifth hour of culture, this process being more complete when the thallus is incubated in white light than when the thallus is aging in darkness. Dithiothreitol prevents this inactivation to some extent by reduction (or protection) of ‐SH groups in the protein. In vivo inactivation, in darkness as well as in the light, is accompanied by increase in the molecular mass of the enzyme; this pattern is not greatly changed by dithiothreitol.
Cytokinins in germinating maize caryopses
Authors: Van Staden J.
Published: April 2006

The transport and metabolism of 8[14C]t‐zeatin applied to the endosperm of Zea mays L. caryopses was studied. The applied zeatin was rapidly metabolised to a stable compound which co‐eluted between adenine and dihydrozeatin on a Sephadex LH‐20 column eluted with 10% methanol. This metabolite which was active in the soybean callus bioassay persisted in the endosperm tissue and was not transported in significant amounts to the embryonic axis during imbibition and early germination. Indications are that it can be exported during seedling establishment when nutrient mobilisation from the endosperm is more rapid. The results obtained indicate that Cytokinins susceptible to oxidation apparently do not play a major role in the germination process of the maize kernel. If cytokinins are at ail involved in the germination process of these propagules it would seem that their effect is more likely to be mediated by the dihydro derivatives of these hormones. These compounds do occur in mature maize fruits.
Effect of salicylic acid on nitrite reductase and glutamate dehydrogenase activities in maize roots
Authors: Jain Abha , Srivastava H. S.
Published: April 2006

The effects of 0.01 to 5 mM salicyclic acid on the increase in nitrite reductase or glutamate dehydrogenase activities in maize roots by nitrate or ammonium respectively, were examined. Nitrite reductase activity was inhibited by the highest concentration of the acid. The activity of NADH‐glutamate dehydrogenase was stimulated slightly (but consistently) by the lowest concentration and was inhibited by higher concentrations. Total protein content was also inhibited at high concentrations. When the crude enzyme extract was stored at 25°C in light, the glutamate dehydrogenase activity in the control decreased after 4 h of incubation. Low concentrations of the acid had no effect on this decrease but higher concentration accelerated the process. The divalent cations Caz2+, Mn2+, Mg2+ and Zn2+ protected against loss of enzyme activity during storage, both in the absence and presence of the acid. The inhibitory effect of 5 mM salicylic acid on glutamate dehydrogenase activity is apparent due to interference with the activity of the enzyme rather than with its synthesis.
The rooting ability of shoots raised ‘in vitro’ from the apple rootstock A2 in juvenile and in adult growth phase
Authors: Welander Margareta , Huntrieser Inger
Published: April 2006

The apple rootstock A2 can be readily propagated in vitro both in the juvenile and in the adult growth phase. Shoots were produced by meristem tip culture from the apple rootstock A2 in different growth phases. The influence of growth phases and different concentrations of PG and IBA was investigated as to rooting percentage, survival percentage, number of roots per rooted shoot, root length, shoot length and formation of callus. IBA at 15 μM without PG gave a significantly lower rooting percentage than 5 and 10 μM IBA. PG together with IBA stimulated rooting, the optimum concentrations of PG being, however, not the same for the different growth phases. For the adult growth phase, 10−4M PG promoted rooting, whereas 10−3M PG markedly inhibited rooting. In the juvenile growth phases, both 10−4 and 10−3M PG stimulated rooting. PG at 10−4M also increased the number of roots. The longest roots were obtained at 10−3M PG and 5 μM IBA. PG at 10−3M reduced callus formation at all IBA concentrations used. Neither shoot length nor root length influenced the survival percentage.
Heterotrophic tobacco cell cultures during greening
Authors: Nato A. , Mathieu Y. , Brangeon J.
Published: April 2006

Nicotiana tabacum L. (cv. Xanthi) suspension cultures initially grown in the dark and then exposed to continuous light followed a developmental pattern divided into a lag phase (T0–T2), a growth phase (T3–T9) and a stationary phase (T10–T21). The onset of chloroplast differentiation during the active cell division phase was associated with a rapid chlorophyll synthesis, a high rate of respiratory activity (400 μmol h−1 g−1 dry weight) and a four‐fold increase in soluble protein content compared to that of the initial inoculum. Oxygen evolution was nil until T3. It increased regularly up to a value of 30 μmol h−1 g−1 dry weight at the beginning of the stationary phase, higher values (80 μmol) being reached later in this phase. An inverse relationship between phosphoenolpyruvate carboxylase (PEPCase) and ribulose 1,5‐biphosphate carboxylase (RUBPCase) was shown during cell growth. The PEP‐Case capacity expressed on a soluble protein basis rose from an initial day 0 value of 3.5 μmol to a maximum of 7.0 μmol at T5 and then returned to the initial value during the post‐exponential and stationary phases. In contrast, RUBPCase activity was minimal (0.1 μmol) from T0 to T3 of greening, increasing to a maximum (1.7 to 2.0 μmol) at T8. The 20 fold stimulation of this enzyme capacity was related to a de novo protein synthesis.

Immunodiffusion tests revealed the presence of RUBPCase molecules in soluble crude extract of dark‐grown cells. The SDS‐get densitometric profile of soluble protein extract from dark‐grown cells was qualitatively similar to that obtained with crude extract of green cells. The 56,000 Da polypeptide co‐migrating with the large subunit (LSU) of RUBPCase appeared reduced in dark‐grown cells compared to the peak height of the same polypeptide present in green cells. In both preparations, the 13,000 Da polypeptide co‐migrating with the small subunit (SSU) was equally present. The current hypothesis is that the synthesis of RUBPCase at the time of greening would concern the preferential synthesis of the LSU of the enzyme.
Basic properties of the circadian leaf movements of Oxalis regnellii, and period change due to lithium ions
Authors: Johnsson A. , Johnsen P. I. , Rinnan T. , Skrove D.
Published: April 2006

The circadian leaf movement of Oxalis regnellii Mig, has been investigated. The three leaflets of a stalk were normally synchronized, and under the experimental conditions chosen they showed a period of 26.2 ± 0.1 h. Cutting off one or two leaflets led to a successive decrease of the period length (25.7 ± 0.1 and 25.1 ± 0.3 h resp.). It was possible to phase shift the leaf movements by mechanical means (advance of 1.6 ± 0.3 h).

Lithium ions, added permanently to the transpiration stream, increased the period length of the leaf movements by more than one hour (with 10 mM Li+). A 24 h pulse of 20 mM LiCl caused a permanent 2–3 h phase delay of the circadian rhythm. Four‐h pulses, on the other hand, provoked only transient phase delays, the magnitude being dependent on the phase of application. Lithium concentrations were determined for different regions of leaves and pulvini. It was shown that leaf segments had considerably lower concentrations than pulvini. No significant difference in the lithium concentration was observed between the upper and lower part of pulvini.

In the light leaf position was strongly correlated with water uptake and the consequences for applications of substances to the circadian system via the transpiration stream is discussed. A simple model of the oscillatory system and reactions connected to it is discussed.
Sterol content, fatty acid composition of phospholipids, and permeability of labeled ethylene glycols in relation to salt‐tolerance of yeasts
Authors: Adler Lennart , Liljenberg Conny
Published: April 2006

Two yeasts, the salt‐tolerant Debaryomyces hansenii and the non‐tolerant Saccharomyces cerevisiae were grown in basal media (4 mM NaCl) and also a high salinities that produced a similar salt stress in the two species in terms of growth rate reduction (i.e., 1.4 M NaCl for S. cerevisae and 2.7 M NaCl for D. hansenii). A study was made of the sterol content, the fatty acid composition of the phospholipids, and the permeation of a series of tritiated ethylene glycols of graded molecular weights. On the basis of cell dry weight the amount of total and free sterols increased in both species when cultured at high salinity. Irrespective of growth medium salinity, the molar ratio of free sterols to phospholipids was higher in D. hansenii than in S. cerevisiae. Increased salinity produced only minor changes in the fatty acid composition of the phospholipids in D. hansenii, whereas in S. cerevisiae there was a marked decrease of linolenic acid with a concomitant increase of linoleic acid.

In both yeasts there was an energy linked component in the uptake of ethylene glycol, which component could be inhibited by sodium azide and N‐ethylmaleimide. The passive permeability for ethylene‐, diethylene‐ and triethylene glycol increased for both species at increased salinity. This increase was more pronounced for S. cerevisiae than for D. hansenii. Polyethylene glycol of M, 200 as well as higher polyethylene glycols appeared to be excluded or very slowly admitted by the yeasts.
Release of nucleotide‐cleaving acid phosphatase from carrot cells grown in suspension culture
Authors: Ciarrocchi G. , Cella R. , Nielsen E.
Published: April 2006

Carrot (Daucus carota L. cv. Lunga di Amsterdam) cells grown in suspension culture release into the culture medium a phosphatase capable of converting deoxyribo‐ as well as ribonucleoside triphosphates into nucleosides. The enzyme activity requires acidic pH and allows a prompt utilization of phosphorylated DNA precursors as measured by tritiated dTTP incorporation. Such utilization is partially inhibited by inorganic phosphate and completely inhibited by ATP.
Sucrose‐mediated regulation of fatty acid composition in asexual embryos of Theobroma cacao
Authors: Pence Valerie Creaser , Hasegawa Paul Michael , Janick Jules
Published: April 2006

Asexual embryos of Theobroma cacao L. cultured in vitro grew to a size and fresh weight equal to mature zygotic embryos in vivo when cultured in liquid medium on a rollodrum apparatus. Changes in the fatty acid composition in the asexual embryos, similar to those which occur in the zygotic embryo during normal maturation, were stimulated as the sucrose concentration in the medium was increased to an optimum at 27% sucrose (w/v). As the sucrose concentration increased, there was a shift in the fatty acid composition from predominantly polyunsaturated to saturated and monounsaturated fatty acids characterized by an increase in the mole percents of stearic (18:0) and oleic (18:1) acids and a decrease in the mole percents of linoleic (18:2) and linolenic acids (18:3).
Effet du refroidissement local de la tige sur le transport du AIA exogène en provenance du bourgeon apical et sur la croissance des bourgeons axillaires
Authors: Everat‐Bourbouloux Andrée
Published: April 2006

Effect of local cooling of the stem on exogenous 1AA transport from the apical bud and on the growth rate of axillary buds.

Local cooling (1.5°C) of the stem (on 2 or 4 cm) of Vicia faba L. cv. Aguadulce for 15 h stops the exogenous IAA transport from the apical bud and causes a high accumulation of tracers above and at the level of the cooled zone. This clamping effect is reversed after removal of the cooling system. If the cooling system is maintained for 48 h, about 25% of the exported radioactivity passes the cooled zone. However, the percentage IAA transmitted decreases to about 6.6% if the cooled zone is sufficiently wide (4 cm) and the temperature lowered to 0.7°C±0.3°C. Using a cooling system of 4 cm (0.7±0.3°C) partially releases the lowermost axillary buds (ax1 and ax2) from apical dominance. Yet, the rate of growth of the axillary buds is generally lower than the growth rate after decapitation of the plant.
Light dependency of the cytokinin‐induced bud initiation in protonemata of the moss Funaria hygrometrica
Authors: Simon Patrice E. , Naef Jaques B.
Published: April 2006

Protonemata of the moss Funaria hygrometrica (Hedw.) are grown in large amounts in a liquid culture system, allowing repetitive dry weight measurements for growth control. Ten‐day‐old protonemata are submitted to various light conditions, in the presence of a cytokinin (iP), which is known for its activity in bud initiation in the moss protonema. The hormone has no influence on the growth rate. Growth and budding are shown to be tightly related. Light is necessary for the initiation of buds but not for their development (to some extent). Identical protonematal growth can be obtained in white, Ted or blue light, but not budding, which is reduced in red or blue light. The early morphological changes in red light, known as nutations, and the presumed inhibitor in blue light could be responsible for the reduced budding. Bud initiation in the dark on an organic medium is greatly enhanced if red light pulses are given at regular intervals. When the latter are followed immediately by far‐red light pulses, the stimulating effect is partly suppressed, suggesting a phytochrome‐controlled process.

Experiments with DCMU showed a peculiar effect of this herbicide, which inhibited the use of exogenous sugar in the light but not in the dark.
Proteinase activities in resting and germinating seeds of Scots pine, Pinus sylvestris
Authors: Salmia M. Aulikki
Published: April 2006

Resting seeds of Scots pine contained a moderate amount of acid proteinase activity, about 90% of which was inhibited by pepstatin A and about 10% by p‐hydroxymer‐curibenzoate. In gel chromatography on Sephacryl S‐200 the proteinase activity showed a complex elution pattern with poorly separated peaks at positions corresponding to mol. wts. 100,000 and 30,000 and several shoulders. The results suggested that pine proteinases I and II, which are the main proteinases in the endosperms of germinating seeds (Salmia 1981: Physiol. Plant. 51: 253–258), were not present in the resting seeds.—Seedling extracts showed a low level of acid proteinase activity, which separated into several peaks in chromatography on Sephacryl S‐200. As none of the peaks had the catalytic properties of proteinase I or II, it seems that these endospermal enzymes are also lacking in the seedling tissues.—In the endosperms of germinating seeds the activity of the pepstatin‐sensitive acid proteinase(s) remained at a constant level throughout the period of reserve protein mobilization (lasting up to the stage when the length of dark‐grown seedlings was 60 mm). Proteinases I and II were absent from resting seeds, showed a small increase up to the 20‐mm stage, and then increased rapidly up to the 60‐mm stage.—Resting embryos contained relatively higher acid proteinase activity than resting endosperms, and again about 90% of it was inhibited by pepstatin A and about 10% by p‐hy‐droxymercuribenzoate. During germination the former activity decreased, the latter activity remained at approximately the same level, and the activity of the other acid proteinases increased continuously with the growth of the seedling.—It is concluded that the pepstatin‐sensitive proteinase(s), which is not affected by endogenous proteinase inhibitors, plays a central role in the initiation of reserve protein mobilization in both the embryo and the endosperm. Proteinases I and II, on the other hand, seem to account for the greater part of reserve protein breakdown in the main protein storage tissue, the endosperm.
Temperature induced changes of the ultrastructure and lipid composition in green and senescent leaves of Dicranum elongatum
Authors: Karunen Pirjo , Liljenberg Conny
Published: April 2006

Fatty acid content of the triglycerides in subarctic Dicranum elongatum Schleich was 4 times higher in low (1°C) than in high (23°C) temperature treated green tissue. The respective value was 3 times higher in low than in high temperature treated senescent portions of the shoot. Differences in the triglyceride concentration were corroborated with both light and electron microscopic observations. In addition, low temperature treatment resulted in thick cell walls and in an increase in dry weight of the tissue, whereas the opposite effects were caused by high temperature. Senescence of leaf tissue was accompanied by an over‐all decrease in membraneous cell structures. In senescent leaf cells an inner wall‐like layer, less electron dense than the thick secondary wall, was particularly well developed in low temperature treated material. Characteristic of the senescent leaf cells were cytoplasmic structures, which were described as dormant endospores.
Aryl hydroxylation: A selective mechanism for the herbicides, diclofop‐methyl and clofop‐isohutyl, in gramineous species
Authors: Gorecka K. , Shimabukuro R. H. , Walsh W. C.
Published: April 2006

Esters of substituted phenoxy‐phenoxy propionic acid constitute a new class of herbicides that are effective against gramineous weed and crop species. Slight changes in chemical structure alter drastically the spectrum of weeds controlled by this class of herbicides. Wheat (Triticum aestivum L.) is resistant to diclofop‐methyl (methyl 2‐[4‐(2′,4′‐dichlorophenoxy)phenoxy] propanoate) (DM) and clofop‐isobutyl (iso‐butyl 2‐[4‐(4′‐phenoxy)phenoxy] propanoate) (CI), oat (Avena sativa L.) and wild oat (Avena fatua L.) are susceptible to DM but resistant to CI, and corn (Zea mays L.) is susceptible to both compounds. The antagonism of IAA‐induced elongation in the coleoptile straight growth test was determined to measure biological activity of the herbicides. The basis for the differential responses by gramineous species was related to the metabolism and deioxication of the herbicides in coleoptiles. Growth of wheat coleaptiles was relatively unaffected by both compounds, oat coleoptile growth was inhibited by DM but not by CI. but corn coleoptile growth was inhibited equally by both compounds. Coleoptiles and excised shoots of the three species rapidly hydrolyzed both compounds to their respective acids (diclofop, clofop). The acids were conjugated to a water‐soluble ester conjugate or they were hydroxylated in the chlorine‐substituted phenyl ring and conjugated as a phenolic conjugate. Aryl hydroxylation is a detoxication mechanism in resistant plants. Plants resistant to DM or CI contained low concentrations of the parent ester and the free or bound (ester conjugate) acid and a high concentration of free or bound (phenolic conjugate) aryl hydroxylated acid in coleoptile and shoot tissues, Differential responses by the three gramineous species to DM and CI axe due apparently to differences in their detoxication mechanism. The enzyme for aryl hydroxylation in oat appears to have a higher affinity for the 4‐chloro‐ than for the 2,4‐dichloro‐substituted moiety. Therefore, oat hydroxylated clofop rapidly and was tolerant to CI but the limited ability of oat to hydroxylate diclofop resulted in oat being extremely susceptible to DM.
Electric field‐induced fusion of isolated vacuoles and protoplasts of different developmental and metabolic provenience
Authors: Vienken J. , Ganser R. , Hampp R. , Zimmermann U.
Published: April 2006

Using an electric field pulse technique, we induced fusion between vacuoles and protoplasts of Kalanchoë daigremontiana, between protoplasts from etiolated and green leaf mesophyll, and between mesophyll protoplasts from plants of different physiological properties (Avena sativa: C3 mechanism of photosynthesis, Kalanchoë daigremontiana: crassulacean acid metabolism). Close membrane contact amongst protoplasts or between protoplasts and vacuoles (as required for fusion) was achieved by the application of an alternating, non‐uniform electric field to the suspension. Due to the dielectrophoresis effect the cells attach to each other along the field lines. The fusion process is initiated by the injection of an electric field pulse of high intensity and short duration (μs range). The field intensity has to be sufficiently high to induce reversible breakdown in the area of close membrane contact. After the application of the field pulse, the fusion process is initiated and completed within seconds to a few minutes, depending on the material investigated.

Fusion occurs between protoplasts and vacuoles as well as between protoplasts of different species. Both tonoplast and plasma membranes completely intermingled, indicating that in contrast to suggestions in the literature these membranes are compatible. Furthermore the cytoplasms of etiolated and green protoplasts obviously do not mix after fusion is completed, as etioplasts and chloroplasts kept separated from each other. In all experiments the volume of the fusion product equalled the sum of the compartments that underwent fusion. The wide spectrum of possible applications resulting from these fusion experiments in relation to metabolic problems is discussed.
Determination of 4‐chloroindoleacetic acid methyl ester in Vicieae species by gas chromatography‐mass spectrometry
Authors: Engvild Kjeld C. , Egsgaard Helge , Larsen Elfinn
Published: April 2006

The natural chlorinated auxin, 4‐chloroindoleacetic acid methyl ester, was identified in immature seeds of Lathyrus sativus L., Lathyrus maritimus (L.) Bigel and Lathyrus odoratus L. by thin layer chromatography and gas chromatography‐mass spectrometry. In immature seeds of Vicia sativa L. and Lens culinaris Medik. the hormone was identified by selected ion monitoring. The hormone was determined quantitatively using pentadeuterated 4‐chloroindoleacetic acid methyl ester as internal standard. Contents varied from 1 mg/kg fresh weight in Lathyrus sativus to 0.02 mg/kg in Lens culinaris. Lathyrus maritimus also contained indoleacetic acid methyl ester (0.3 mg/kg) besides the chlorinated analogue.
Reversal of the inhibitory action of abscisic acid by benzyladenine in excised watermelon cotyledons
Authors: Longo Giovanna P. , Stopelli Bruna , Rossi Gianfranca , Longo Claudio P.
Published: April 2006

Cotyledons of watermelon (Citrullus vulgaris Schrad. cv. Fairfax) were excised from the embryo after 24 h of imbibition and cultured for several days on filter paper with water or abscisic acid (ABA) solution. In some experiments the cotyledons were pretreated with benzyladenine (BA) for times ranging from 5 min to 2 h before transfer to ABA.

A treatment with 10−5M ABA blocked all developmental parameters examined (growth and increase in appropriate markers for glyoxysome, peroxisome and plastid development). This blocking can be prevented by an initial treatment with 10−4M BA for 2 h. This pretreatment with BA overrides the action of ABA: the final developmental responses are not just restored to the level of the water control, but they are almost as high as those obtained by treating the cotyledons with BA only. If BA is administered for three days together with ABA the reversal of inhibition is much less efficient.
Characterization of glutamine‐synthetase from Beta vulgaris
Authors: Nesselhut Thomas , Harnischfeger Götz
Published: April 2006

Glutamine‐synthetase (GS) from Beta vulgaris seedlings, purified 150‐fold, was characterized with regard to its physiological substrate NH3. The data were compared to the unphysiological substrate NH2−OH frequently used in the assay (both synthetase and transferase reaction). The pH‐optimum was found at pH 7.5 for the synthetase and at pH 6.3 for the transferase reaction. Through plots of pKm vs pH, the pKe values for dissociable groups in the reaction center were found to be in the range from pH 7–8. Mg2+‐ion serves as an allosteric effector with a Hill coefficient of 4.2. The results are discussed in relation to the control of nitrogen metabolism in Beta.
Lipoxygenase activities of young wheat leaves
Authors: Douillard Roger , Bergeron Edith
Published: April 2006

Lipoxygenase activity has been measured in various sections of the growing first leaf of wheat (Triticum aestivum L. cv. Florence Aurore). Weight, chlorophyll and lipoxygenase activity have been determined during the growth of the coleoptile and of the first and second leaf. Lipoxygenase activity variations are correlated with the growth of each organ. It seems that this enzyme has to do with chloroplast growth rather than with chloroplast division.
α‐1,4‐Glucan phosphorylase forms in the green alga Eremosphaera viridis
Authors: Steup Martin , Melkonian Michael
Published: April 2006

In extracts of the unicellular green alga Eremosphaera viridis DeBary (Chlorococcales, Chlorophyceae) the average specific activity of α‐1,4‐glucan phosphorylase (E.C. 2.4.1.1) was 200 nmol glucose 1‐phosphate formed per min and mg protein. Using continuous and discontinuous electrophoresis on polyacrylamide gels, three phosphorylase forms were found. When the log of the relative mobility of the three enzyme forms was plotted versus the acrylamide gel concentration (Ferguson plot) parallel lines were obtained, indicating that the three enzymes were indiscernible with respect to molecular weight. Electrophoresis on density gradient gels resulted in three activity zones lying close to each other. The relative molecular mass (Mr) of the three enzymes was estimated to be around 180,000 with a difference of less than 7,000 between the small and the large forms.
Metabolism of tritiated gibberellin A1 in seedlings of Norway spruce, Picea abies
Authors: Dunberg Arne
Published: April 2006

Five‐week‐old seedlings of Norway spruce, Picea abies (L.) Karst., metabolized 1,2‐/3H/‐gibberellin A1 into a single major compound chromatographically similar to gibberellin A8. The conversion rate exceeded 10% within the 24‐h incubation period.
Changes in the rooting inhibitory effect of chestnut extracts during cold storage of the cuttings
Authors: Gesto M. D. V. , Vazquez A. , Vieitez E.
Published: April 2006

Extracts of cold stored chestnut cuttings (Castanea sativa Mill.) were examined for the inhibitory effect on the stimulation of rooting by 1AA which has been detected previously in extracts from freshly collected cuttings. The extracts were fractionated by paper chromatography and the different zones of the chromatograms were bioassayed together with 1AA by the bean rooting test. The bean rooting test showed that the inhibitory effect decreased with the length of cold storage period, so that after 5 months of storage, the inhibitory effect had disappeared, and a root promoting zone was found on the chromatograms. A comparative study of phenolics in this zone, before and after cold storage, revealed the formation of vanillyl and salicyl alcohols in the chilled material. Vanillyl and salicyl alcohols are rooting stimulators and increase the effect of 1AA on rooting in bean cuttings.
Separation of presumptive plasma membranes from mitochondria by partition in an aqueous polymer two‐phase system
Authors: Widell S. , Larsson C.
Published: April 2006

Light‐induced absorbance changes (LIAC), indicating the reversible reduction of a b‐type cytochrome, and with a possible connection to blue light photomorphogenesis, have been found in a presumptive plasma membrane rich centrifuge fraction from LIAC could be due to plasma membrane vesicles turned inside out or to cytochromes localized in other organelles. Phase partition proved to be a rapid method (results technique membrane particles are separated according to differences in surface properties rather than size and density. LIAC could be separated into two fractions: one partitioning into the polyethylene glycol rich upper phase and another preferring the dextram rich lower phase. Mitochondria (cytochrome c oxidase) were recovered in the lower phase. A dual distribution of LIAC was found with all materials tested: corn coleoptiles, corn shoots, barley shoots and cauliflower inflorescences. About 80–90% of the cytochromes in the upper phase were related to LIAC, whereas only 10–15% of those in the lower phase were of this kind. The LIAC preferring the upper phase was probably bound to the plasma membrane, since plasma membrane vesicles are known to have a high partition in these phase systems. The lower phase LIAC could be due to plasma membrane vesicles turned inside out or to cytochromes localized in other organelles. Phase partition proved to be a rapid method (results within one hour after the initial pelleting) for purification of presumptive plasma membranes, yielding a preparation which contained five times less mitochondrial contamination than the preparation obtained with sucrose gradient centrifugation (the 33/45% w/w sucrose interface fraction).
Analysis of the initial stages of plant protoplast development using 33258 Hoechst: reactivation of the cell cycle
Authors: Galbraith David W. , Mauch Teri J. , Shields Barbara A.
Published: April 2006

A microfluorimetric procedure, employing the fluorescent stain 33258 Hoechst, has been developed for the investigation of the process of DNA synthesis during the initial stages of culture of tobacco (N. tabacum cv. Xanthi) leaf protoplasts.

In this system, the freshly‐isolated protoplasts exhibited a unimodal distribution of nuclear DNA content characteristic of the diploid state. The almost immediate onset of DNA synthesis during culture resulted in a doubling of nuclear DNA levels prior to the first mitoses. Although the majority of the protoplasts subsequently entered into synchronous mitosis and cell division, a proportion of the remainder developed into large polyploid cells. Upon further culture, the polyploid cells became subdivided into clusters of small diploid cells. Measurement of total cell protein and cell volumes during culture indicated that a relationship existed between these parameters and the initiation of mitosis. The significance of these observations is discussed.
The lag‐phase of potassium translocation from the root to the shoot of low‐salt barley plants. Kinetic and localization studies
Authors: Van Iren Frank , Joolen M. Lonlou , Gerritsen Anton F. C. , Noordervliet Marcel A. W. , der Sluijs F. Pinie Boers‐Van
Published: April 2006

In roots of low‐salt barley (Hordeum vulgare L.), translocation of K+, as well as of several other ions, from the root to the shoot starts after a lag‐time. Its length is independent of external concentration. The onset of upward translocation can be remarkably abrupt. Three hypotheses that could explain the lag‐phase were tested:

It is the result of successive loading of the concentric root cell layers centripetally from the epidermis.

It is the result of successive loading of the root basipetally from the apex.

It is the result of induction of the mechanism(s) responsible for upward translocation.

All three hypotheses are rejected. Within the whole root radial as well as longitudinal equilibration appears to be very rapid. The simple model of compartmentation is rejected. A more complex compartmentation of the cytoplasm (symplasm) in which the endopiasmic reticulum could play a predominant role is suggested. The mechanisms of vacuolar accumulation and upward translocation appear biochemically related.
Sulfate transport of excised roots as an index of genotype response to herbicides
Authors: Ferrari G. , Nardi S. , Cacco G. , Dell'Agnola G.
Published: April 2006

The inhibitory action of four herbicides (atrazine, dalapon, moiinate, propanil) on the membrane transport of sulfate by excised roots was evaluated in tolerant (Oryza saliva) and susceptible (Pisam sativum, Hordeum vulgare) cultivated species, and in a tolerant and susceptible variety of a weed (Brassica rapa). A parallelism between the response of the root transport activity and the general response of the genotype was ascertained, irrespective of the metabolic target of the herbicide. The inhibition mechanism of sulfate uptake was either competitive, non competitive, or uncompetitive, but this aspect was not correlated with the response of the genotype to the herbicide. The kinetics of absorption 14C atrazine by excised roots and by chloroplasts of Brassica rapa were strictly related: the amount of atrazine binding to roots and to chloroplasts was higher in the susceptible than in the resistant variety. The Sevel of atrazine inhibition of sulfate transport in roots was correlated to that of the Hill reaction; both were higher in the susceptible variety. The membrane transport within the roots appears to summarize and anticipate the metabolic response of genotypes to herbicides.
Synthesis and release of cyclic adenosine 3′:5′‐monophospliate by aquatic macrophytes
Authors: Francko David A. , Wetzel Robert G.
Published: April 2006

Tissues from the aquatic macrophyte species Scirpus subterminalis, Najas flexilis, Ceratophyllum demcrsum, Potamogeton zosteriformis, and Nuphar advena contain cAMP in quantities similar to those reported in algae. Scirpus, Najas, and Ceratophyllum released cAMP into the extracellular media in quantities which varied interspecifically and intraspecifically in differing media. Macrophytic release of cAMP may be an important source of dissolved cAMP in lakewater.
Effects of salinity and replacement of K+ by Na+ on lipid composition in two sugar beet inbred lines
Authors: Stuiver C. E. E. , Kuiper P. J. C. , Marschner H. , Kylin A.
Published: April 2006

The effects of NaCl and replacement of K+ by Na+ on the lipid composition of the two sugar beet inbred lines FIA and ADA were studied (a) with increasing additions of NaCl to the basal medium, and (b) with increasing replacement of K+ by Na+ at the same total concentration as in the basal medium. Direct relations were noted between NaCl concentration of the nutrient solution and the phospholipid concentration in the roots of FIA, the genotype characterized by a low K+/Na+ ratio, as well as between NaCl in the medium and the phospholipid concentration in the shoots of ADA, the genotype with a high K +/Na + ratio. The sulfolipid level in the roots of FIA was maintained at higher NaCl concentrations, while it was decreased in ADA. The glycolipid concentration in the shoots of ADA and the degree of unsaturation of the fatty acids of the total lipid fraction were decreased by salinity, indicating reduced biosynthesis of chloroplast glycolipids and/or accelerated oxidation of these lipids in the presence of NaCl.

In the Na+ for K+ replacement experiment a low content of K+ in the medium resulted in decreased levels of total lipids, phospholipids and sulfolipid in the roots of both genotypes, which did not relate to root growth. K+‐leakage from the roots at low K+‐level in the medium may be reduced by the increase in saturation of the lipids. In the shoots of ADA increased levels of total lipids, phospholipids and Sulfolipid were noted at a low K+‐concentration of the nutrient solution.
Genetic variability in charge microheterogeneity and polypeptide composition of phaseolin, the major storage protein of Phaseolus vulgaris; and peptide maps of its three major subunits
Authors: Bollini R. , Vitale A.
Published: April 2006

Molecular polymorphism of phaseolin, the major storage protein of Phaseolus vulgaris L., and structural homology of its subunits were investigated. A high degree of charge heterogeneity was evidenced by isoelectric focusing. Comparison among phaseolins isolated from seven different cultivars showed genetic variability both in isoelectric focusing pattern and subunit composition. However tryptic peptide maps of these phaseolins were very similar. The three phaseolin subunits isolated from cultivar Greensleeves were compared by peptide mapping after limited enzymatic digestion and had very similar primary structures.
Transport of Mg2+ and Ca2+, and Mg2+‐stimulated adenosine triphosphatase activity in oat roots as affected by mineral nutrition
Authors: Stok Bert P. , Tànczos Otto Gy. , Kähr Monika , Bep Stuiver C. E. E. , Kylin Anders , Kuiper Pieter J. C.
Published: April 2006

Mg2+‐ and Ca2+‐uptake was measured in dark‐grown oat seedlings (Avena sativa L. cv. Brighton) cultivated at two levels of mineral nutrition. In addition the stimulation of the ATPase activity of the microsomal fraction of the roots by Mg2+ was measured. Ca2+‐uptake by the roots was mainly passive. Mg2+‐uptake mainly active; the passive component of Mg2+‐uptake was accompanied by Ca2+‐efflux up to 60% of the Ca2+ present in the roots.

In general Mg2+ ‐uptake of oat roots was biphasic. The affinity of the second phase correspond well with that of the Mg2+‐stimulation of the ATPase activity, in low‐salt roots as well as in high‐salt roots and in roots of plants switched to the other nutritional condition. Linear relationships were observed when [phase 2] Mg2+‐uptake was plotted against Mg2+‐stimulation of the ATPase activity of the microsomal fraction of the roots. In 5 days old high‐salt plants 1 ATP (hydrolysed in the presence of Mg2+ J corresponded with active uptake of a single Mg2+ ion, but in older high‐salt roots and in low‐salt roots more ATP was hydrolysed per net uptake of a Mg2+ ion. The results are discussed against the background of regulation of the Mg2+‐level of the cytoplasm of root cells by transport of Mg2+ by a Mg2+‐ATPase to the vacuole, to the xylem vessels, and possibly outwards.
Pressure – volume curves and drought injury
Authors: Kyriakopoulos Elfrieda , Richter Hanno
Published: April 2006

Leaf hygrometers were used to establish pressure‐volume curves on detached leaves of four herbaceous species (Asarum europaeum, L., Hepatica nobilis, Mill., Phyteuma spicatum, L., Pulmonaria officialis, L.). Breakdown of leaf tissues due to drought injury was independently estimated. There was good agreement between the onset of visible symptoms and beginning deviations from the straight‐line portion of the pressure‐volume curve. Type I transformation of data (plots of water potential vs. reciprocal relative water content) is superior for recognizing deviating data points. The results are discussed in the context of pressure‐volume curve methodology; pressure‐volume curves are shown to provide a promising tool for estimating and displaying drought tolerance in plants.
The Glycine‐Glomus‐Rhizobium symbiosis
Authors: Bethemfalvay Gabor J. , Yoder Joseph F.
Published: April 2006

Soybean [Glycine max, (L.) Merr, cv. Lancer] plants were grown in a sterile rooting medium watered daily with a nutrient solution containing 4, 20, 100, or 500 μM, P. Plants were inoculated with Rhizobium japonicum, strain 61A118 and grown in the presence or absence of the endomycorrhizal fungus Glomus fasciculatus, Gerdemann et Trappe. Plants grown at the highest P regime had six times higher shoot dry weight than those grown in the lowest P regime. Nodulation did not occur at 4 μM P. Nodule dry weight increased 200‐fold from the 20 to the 500 μM P treatment. Percentage P in shoots and nodules differed significantly among all treatment levels. Acetylene reduction by nitrogenase increased logarithmically with increasing amounts of P. Hydrogen evolution was not detectable at the 20 μM P level. The relative efficiency of nitrogen fixation increased with increasing P stress. Infection by Glomus fasciculatus, at the 500 μM P level was negligible and did not affect the parameters measured. At all other treatment levels the mycorrhizal plants had significantly higher rates of N2 fixation, plant and nodule mass and P content.
Glutamate dehydrogenase in the first leaf of wheat
Authors: Lauriére C. , Weisman N. , Daussant J.
Published: April 2006

Glutamate dehydrogenase extracted from wheat leaves (Triticum aestivum L. cv. Capitole) taken at two different physiological stages was analysed by electrophoretic and immune‐chemical techniques. Two NAD‐dependent antigens were identified which bear the balk of the glutamate dehydrogenase activity in the two extracts. The first enzyme was found in much larger amounts in young than in senescent leaves and the reverse situation was observed for the second antigen. The possible relationships between this antigenic polymorphism and the heterogeneity detected by isoelectric focusing from the two extracts were investigated. A charge heterogeneity (isoelectric points about 5.7 and 4.8) was found for the first antigen in both extracts. The second antigen appeared homogeneous (isoelectric point about 5.7) at least in senescent leaves. The last result indicates that two quite different antigens appear in the same isoelectric focusing zone.
Glutamate dehydrogenase in the first leaf of wheat
Authors: Laurière C. , Weisman N. , Daussant J.
Published: April 2006

The activity of glutamate dehydrogenase and the amounts of two antigens, bearing the bulk of this activity, were determined in wheat leaves (Triticum acstivum L. cv. Capitole) at different ages. These results were compared to those obtained with leaves deprived of light (darkness‐stressed) during three days, at different stages of leaf life. The glutamate dehydrogenase activity increased in the leaves during normal senescence of the whole plant. De novo synthesis of one of the glutamate dehydrogenase proteins was shown, which correlated with this, increase in activity. The considerable differences between She effects of darkness‐stress, according to the leaf age, may characterize three steps in the leaf life: a first step during which leaves were not affected by stress, a second one for which the stress effect was partially reversible, and a final one during which stress impact was irreversible.
Translocation of 14C‐assimilates in roses
Authors: Mor Yoram , Spiegelstein Hanna , Halevy Abraham H.
Published: April 2006

The upper shoot on decapitated rose branches (Rosa hybrids cv. Marimba) grows faster than lower shoots on the same branch. Transport of radioactive assimilates to the upper shoot is higher than to the lower ones. Darkening of the uppermost shoot resulted in the reduction of growth and I4C‐assimilate accumulation in the darkened shoot as well as the promotion of growth and 14C transport to the lower 2 shoots, thereby rendering dominance to the second shoot. Benzyladenine treatment to the uppermost shoot reversed the effect of darkening and restored the apical control of this shoot.
5‐Oxo‐prolinase in Nicotiana tabacum: catalytic properties and subcellular localization
Authors: Rennenberg Heinz , Stcitikamp Reinhard , Kesselmeier Juergen
Published: April 2006

5‐Oxo‐prolinase of cultured tobacco cells is a soluble enzyme predominantly localized in the cytoplasm. To get optimal enzyme activity, the presence of the monovalent cation ammonium and the divalent cations Mg2+ and Mn2+ in the assay mixture is necessary. The enzyme has an extremely alkaline pH—(9.5–10.5) and a high temperature ‐ optimum (55°C). In contrary to the 5‐oxo‐prolinase from animal cells, where heat‐stabilization by 5‐oxo‐proline is observed, the high temperature optimum of the tobacco enzyme is due to stabilization by ATP. High 5‐oxo‐prolinase activity in tobacco cell homogenates was not only shown with the co‐substrate ATP, but with other purine‐nucleotides, too, although ATP was the best co‐substrate of the compounds tested. Substrate affinity of the tobacco enzyme (Km 5‐oxo‐proline = 30.5 μM) is similar to that demonstrated for wheat germ 5‐oxo‐prolinase. Competitive inhibition by the 5‐oxo‐proline analogues 2‐imidazolidone‐4‐carboxylic acid(K1= 14.5 μM) and dihydroorotic acid (K1=2 mM) revealed a much higher sensitivity of tobacco 5‐oxo‐prolinase to these compounds than observed for the mammalian enzyme.
Lipoxygenase‐ mediated cleavage of fatty acids in plant mitochondria
Authors: Dupont J.
Published: April 2006

Incubation of cauliflower bud mitochondria in the presence of 5 mM CaCl2 results in a rapid hydrolysis of the main membrane phospholipsds. Under the action of phospholipase D, phosphatidic acid is produced and forms, within the membranes, a very labile complex with Ca2+ and HPO42‐ions present in the incubation medium. With time, one observes a first step characterized by the formation of phosphatidic acid, followed by a second step linked to the breakdown of this phospholipid. The enzyme responsible for the disappearance of phosphalidic acid has been identified as lipoxygenase. In the presence of molecular oxygen, this enzyme acts on the polyun‐saturated fatty acids of phosphatidic add (mainly C18:2 and C18:3) yielding small water‐soluble molecules, one of them being identified as malondialdehyde (1, 3‐propanedial). Experiments involving inhibitory conditions of the breakdown of phosphatidic acid indicate that lipoxygenase acts directly on membrane‐bound phosphatidic acid without previous, involvement of a lipolytic acyl hydrolase activity. In addition, the lipoxygenase activity is fully sensitive to hydroxamate derivatives. It is proposed that the lipoxygenase activity may account for a part of the mitochondrial alternative electron pathway that is insensitive to cyanide.