bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Greening of Etiolated Seedlings II. Leaf Greening by Phytochrome Action in the Embryonic Axis
Authors: DE GREEF J. A. , CAUBERGS R.
Published: April 2006

We could demonstrate that greening of primary bean leaves in etiolated seedlings of Phaseolus vulgaris cv. Limburg can be controlled by a selective light‐pretreatment of the embryonic axis. This light‐induced interorgan synergism proved to be a phytochrome‐mediated process. The red/farred photoreversible effect on the embryonic axis seems to be primarily linked to changes in the energy metabolism of the primary leaves. Phototransformation of the protochlorophyll present and pigment synthesis are very dependent upon an adequate supply of biochemical energy. When the embryonic axis is selectively pre‐exposed to red light for a short time, respiration is markedly enhanced in the leaves and photosynthesis starts immediately upon illumination of the etiolated leaves after an incubation period of optimal length in the dark. The stimulatory effect of the red pretreatment on leaf respiration and photosynthetic capacity could be abolished to the level of the dark controls by a subsequent far‐red irradiation on the embryonic axis. It is therefore postulated that phytochrome plays a regulatory role in interorgan cooperation. The metabolic changes involved in photomorphogenesis of etiolated seedlings are closely related to changes in energy production. Our data indicate that the primary act of phytochrome becomes operative at the biochemical level by its directional influence on the energy balance of the cell and coordinates the use of metabolic energy within a tissue and between organs.
Induction of Thermosensitivity in Wheat Roots: Salt Sensitivity and Effects of Chloramphenicol and Ethanol
Authors: SKOGQVIST INGRID
Published: April 2006

Thermosensitivity was induced through a heat shock in wheat roots. Chloramphenicol and ethanol decreased the induced sensitivity to a degree where all roots were alive. The heat sensitized wheat roots were more sensitive to high salt concentrations than untreated roots.
Identification of a Cytokinin, 6‐(3 Methyl‐2‐butenylamino) purine, in Sea Water and the Effect of Cytokinins on Brown Algae
Authors: PEDERSEN MARIANNE
Published: April 2006

Using combined gas chromatography and mass spectrometry a growth‐promoting, organic component of sea water has been quantitatively estimated and identified as the cytokinin 6‐(3 methyl‐2‐butenylamino) purine. Additions of this cytokinin, kinetin or sea water from the Fucus‐Ascophyllum zone increased the growth of Ectocarpus confervoides and Pylaiella litoralis in artificial sea water. Additions of kinetin to bacteria‐free cultures of Ectocarpus fasciculatus also initiated the production of upright ectocarpoid filaments.
Effects of Daylenth on Endogenous Gibberellins in Solanum andigena
Authors: RAILTON I. D. , WAREING P. F.
Published: April 2006

When tritiated gibberellin A1 was fed to intact potato plants growing under different daylength conditions it was converted to a more polar acidic metabolite. The rate of metabolism was the same under both long and short day conditions.

Attempts were made to obtain information about the possible sites within the cell where gibberellin metabolism took place.
Cytochemical Localization of Peroxidase in Plant Cells
Authors: RAA J.
Published: April 2006

Plant cells were stained for peroxidase by exposing them to a mixture of p‐phenylene diamine and hydrogen peroxide. Peroxidase activity is shown to be associated with chromosomes, nucleoli, cell walls and cytoplasm. Possible physiological roles of peroxidase bound to different structures are discussed.
Phase Shift Effects in the Kalanchoë Petal Rhythm due to Two or More Light Pulses
Authors: JOHNSSON A. , KARLSSON H. G. , ENGELMANN W.
Published: April 2006

The circadian petal rhythm of Kalanchoë blossfeldiana Poellniz was studied theoretically and experimentally. Results of experiments in which (i) two light pulses and (ii) repeated light pulses were given to the flowers are compared with predictions based on a previously published feedback model. In this model both the amplitude and the phase of the rhythm are affected by light pulses. Results from the present phase shift studies are shown to be in good agreement with the model.

The results are also discussed in relation to a constant amplitude model like that suggested by Pittendrigh for the eclosion rhythm of Drosophila.
Trypsin Inhibitors during Germination of Vigna sinensis Seeds
Authors: FILHO JOSE XAVIER
Published: April 2006

The trypsin inhibiting activity of cotyledonary extracts of serido beans (Vigna sinensis) falls continuously during germination to a value which represents 5 % of the value for the dry seed. The specific activity is constant over the first three days and then decreases, reaching a level at the seventh day of germination which represents 20 % of the initial value. It is also shown that the axial parts control the disappearance of the trypsin inhibiting activity of the cotyledons. The results presented here seem to indicate a role for these substances in the process of germination.
Movement of Amyloplasts in the Statocytes of Geotropically Stimulated Roots. The Pre‐Inversion Effect
Authors: IVERSEN TOR‐HENNING , LARSEN POUL
Published: April 2006

Previously inverted Lepidium roots were placed in a horizontal position and the amyloplasts in the statocytes of the root cap allowed to fall through their entire range of movement across the cell. Under these conditions the amyloplasts first follow a mainly downward course for 6 to 8 min at a speed between 0.5 and 0.8 μm per min. For the next 10 min they move slightly more slowly in a direction away from the apical end of the cell, still sinking somewhat, but without reaching the plasmalemma along the lower wall.

Previous experiments have shown that conditions assumed to allow the amyloplasts to slide parallel to the longitudinal cell walls are those that give rise to the largest geotropic curvatures. Such conditions are for instance (1) stimulation at 135° (root tips pointing obliquely upward) and (2) inversion of roots for 16 min followed by stimulation at 45°. Treatments assumed not to permit extensive sliding of the amyloplasts produce smaller geotropic curvatures, namely (3) stimulation at 45° without pre‐inversion and (4) inversion followed by stimulation at 135°. The location of the amyloplasts after these four kinds of treatment has now been determined on photomicrographs and the assumptions concerning the paths and extent of sliding of the amyloplasts confirmed.

Observations on electron micrographs showed that under all conditions the amyloplasts are separated from the plasmalemma by other organelles, such as ER, nucleus or vacuoles.

In roots rotated for 15 min parallel to the horizontal axis of the klinostat at 2 rpm, the amyloplasts are not clumped together as densely as in normal, inverted or stimulated roots, but they are not scattered over the entire cell volume.

The statolith function of the amyloplasts is discussed in view of these and other observations.
Translocation and Metabolism of Picloram and 2,4‐D in Populus tremula
Authors: ELIASSON LENNART , HALLMÉN ULF
Published: April 2006

Translocation and metabolism of 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) and 2,4‐dichlorophenoxyacetic acid (2,4‐D) in small plants of aspen (Populus tremula L.) were studied. In most experiments 14C‐carboxyl‐labelled herbicides were used. Considerable quantities of both herbicides were retained in the treated leaf. Translocation was mainly upwards into the growing shoot tip. Only minute quantities were found in the roots. Injection of the herbicides through a cut stem surface increased the translocation into the roots very little. One of the reasons for the limited downward translocation is considered to be a ready transfer of the herbicides between the phloem and the xylem.

Both herbicides were incorporated into complexes from which the active herbicides could be released. However, this complex formation can only partly account for the retention of the herbicides in the treated leaves. The differences in metabolism found between 2,4‐D and picloram cannot explain the considerable difference in toxicity between the compounds.
Growth Substances Isolated from Tubers of Cyperus esculentus var. aureus
Authors: TAMÉS R. SÁNCHEZ , GESTO M. D. V. , VIEITEZ E.
Published: April 2006

A methanolic extract of tubers of Cyperus esculentus Ten. var. aureus Richt. contains compounds which inhibit growth of oat coleoptile sections and germination of Beta vulgaris L., Lotus corniculatus L., Lolium perenne L., Pisum sativum L., Trifolium repens L., Lactuca sativa L. and Lycopersicum esculentum Ludwig.

p‐Hydroxybenzoic acid, vanillic acid, syringic acid, ferulic acid and p‐coumaric acid were identified. Four other active compounds which could not be identified were also isolated.
Rubidium and Potassium Absorption by Bean‐leaf Slices Compared to Sodium Absorption
Authors: JACOBY B. , ABAS S. , STEINITZ B.
Published: April 2006

At salt concentrations of 0.1 mM as well as of 5.0 mM, the 22Na+ absorption capacity of bean (Phaseolus vulgaris L. cv. ‘Brittle Wax’) leaf tissue increased during the period of leaf expansion and decreased rapidly after leaf maturation. The absorption capacity for 86Rb+ and 42K+ was highest in very young leaves and decreased continuously in expanding and in mature leaves. The 86Rb+ absorption capacity of mature leaves was not increased by detopping the plants; this senescence‐retarding treatment more than doubled 2Na+ absorption.

The absorption of 22Na+ by bean‐leaf slices was not enhanced by light, whereas 86Rb+ and 42K+ absorption was much affected.

Previously absorbed 86Rb+ and 42K+ were more available for exchange than 22Na+.
Seasonal Changes in Auxin Effect on Rooting of Douglas‐Fir Stem Cuttings as Related to Bud Activity
Authors: ROBERTS A. N. , FUCHIGAMI L. H.
Published: April 2006

The relation of seasonal bud activity to the periodicity of rooting in Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, stem cuttings was studied in combination with auxin and cold storage treatments. Cuttings were collected in all months except April and May, for 3 years.

Rooting was least in September and October when bud dormancy was most pronounced, greatest in December and January if exogenous auxin was applied, or in February and March if no auxin was used. The buds contributed significantly to rooting from January to April, and were responsible for differences in rooting of terminal and lateral cuttings during this period. Auxin did not enhance rooting in September and October, but at other times it replaced or supplemented the role of vegetative buds in promoting rooting. Auxin also removed the differences in rooting between lateral and terminal cuttings. Cold treatment in October and November removed bud dormancy and enhanced rooting. After November the need for auxin or cold treatment diminished and rooting without either treatment reached a maximum in February and March. Auxin did not change the seasonal pattern of rooting but broadened and enhanced the rooting response in favor of earliness.

These results are discussed in relation to the effect of bud activity on auxin response and root initiation. The hypotheses are proposed that cambial dormancy or auxin deficiency is not the limiting factor during bud dormancy, and that cold treatments have the effect of bringing inhibitors and promoters into proper balance for optimum rooting response.
Changes in Endogenous Cytokinins of Lettuce Seed during Germination
Authors: VAN STADEN J.
Published: April 2006

Using the soybean callus bioassay it has been shown that dormant lettuce seeds (Lactuca sativa L. cv. Grand Rapids) contain large amounts of water soluble cytokinins and small amounts of butanol soluble ones. When the seeds are irradiated with red light, or imbibed with 5 mg/1 gibberellic acid in the dark, the total cytokinin content of the seeds decreases, the level of water soluble cytokinins decreases, and the level of the butanol soluble cytokinins increases. Far‐red light does not reverse this effect completely although cytokinin activity in the butanol extracts decreases following such irradiation.

It is proposed that the interconversion of cytokinins initiated by red light, or gibberellic acid in the dark, is one of the primary events leading to radicle elongation in light‐sensitive lettuce seed.
The Quantitative Yield in Purification of Cytokinins. Model‐experiments with Kinetin, 6‐Furfuryl‐amino‐purine
Authors: HEMBERG TORSTEN , WESTLIN PER ERIK
Published: April 2006

Model‐experiments with kinetin, 6‐furfuryl‐amino‐purine, to determine the quantitative yield in purification of cytokinin extracts have been performed. If kinetin in acidic water solution is partitioned three times with equal volumes of ethyl ether, about 50 per cent of the kinetin passes into the ether phases. In similar experiments with ethyl acetate more than 90 per cent of the kinetin goes over to the ethyl acetate phases. Accordingly, use of these two solvents in purification of cytokinin extracts leads to very large losses. Use of petroleum ether or n‐hexane on the other hand leads to none or very small losses.

Partitioning of alkaline kinetin solutions three times with equal volumes of 1‐butanol results in an almost quantitatitve extraction of the kinetin from the water solution.

About 7 per cent of the original amount of kinetin follows the acid auxin, when a saturated ether solution of kinetin is extracted according to a common method for acid auxins. Kinetin may thus interfere in later analyses for auxins.

The dangers involved when cytokinins are “purified” according to normal practice are pointed out.
The Relationship Between Rooting of Dahlia Cuttings and the Presence and Type of Bud
Authors: BIRAN I. , HALEVY A. H.
Published: April 2006

Dahlia cuttings with actively growing buds are relatively hard to root as compared with those having non‐growing or inhibited buds. In cuttings containing buds which sprouted during the rooting period, an inverse relationship was found between rooting percentage and growth rate of buds. Reproductive buds suppress rooting more than vegetative ones. Removing the growing terminal, parts of the cuttings (vegetative or reproductive) increased rooting percentage of cuttings. It is suggested that growing buds may affect rooting of cuttings in two opposed directions. The first is inhibition of rooting by competing with the roots for metabolites and the second is promotion of rooting by enhancing cambial activity.
Growth Retardants and the Germination of Light Sensitive Lettuce Seed
Authors: BERRIE ALEX M. M. , ROBERTSON JAMES
Published: April 2006

The effect of the dwarfing compounds chlormequat, B995, and Phosphon D on the germination of lettuce seed in darkness was found to be a depression which could be overcome in part by red light, GA, and kinetin. There was a marked statistical interaction between the growth retardants and all the mitigating treatments except B995 and GA, and light, at 30°C and GA and Phosphon D at 20°C and this implies a biological interaction at the site of action of the growth retardant. It is suggested that the action of the compounds considered is in the establishment of an ordered system since it is unlikely that there would be a common binding site for kinetin and GA.
Étude par électrophorèse en gel de polyacrylamide de I'évolution enzymatique des tissus de Poire Passe‐Crassane pendant la maturation du fruit cueilli
Authors: HARTMANN C. , DROUET A.
Published: April 2006

Evolution of different enzymes (glucose 6‐phosphate dehydrogenase EC 1.1.1.49, fructose 1–6 diphosphate aldolase EC 4.1.2.1.3, malic enzyme EC 1.1.1.40, pyruvic decarboxylase EC 4.1.1.1) was followed by polyacrylamide gel electrophoresis and specific staining during the maturation of the pear (cv. Passe‐Crassane) harvested and stored at +15°C. During the increase of the respiration rate, the glucose 6 P dehydrogenase activity declines while the three other enzymes activity increases. Results obtained are discussed.
On the Nature of the Heat Stabilizing Effect of Inorganic Ions on Escherichia coli
Authors: LJUNGER CLAES , LARSSON KERSTIN
Published: April 2006

The growth lag of Escherichia coli at 45°C was reduced by the addition of sodium, potassium, magnesium and calcium ions to the growth medium. A method to quantitatively determine the lag‐reducing effect of these ions was developed. The results obtained showed that equivalent amounts of the ions produced the same reduction of the growth lag. According to the results of plasmolysis experiments cells of E. coli suspended in peptone broth were permeable to all four ions. The course of plasmolysis and subsequent deplasmolysis was registered as changes in the cells' ability to scatter light. The heat stability of catalase from E. coli was increased by addition of the four ions. This was observed in experiments with intact cells and with a crude cell‐free preparation of catalase. The results of our experiments are most easily explained by assuming a stabilizing effect of the ions tested on the intracellular bacterial proteins.
Multiphasic Uptake in Plants I. Phosphate and Sulfate
Authors: NISSEN PER
Published: April 2006

Uptake of phosphate and sulfate is shown by reanalysis of available data to be mediated by single, multiphasic mechanisms which may be fundamentally similar in a variety of plants and tissues.
Pool Control of Uracil Uptake by Synchronous Chlorella
Authors: KNUTSEN GJERT
Published: April 2006

Experiments with autospores of Chlorella fusca showed that the uptake rate of uracil was reduced as much as 40 % as the result of formation of soluble pools of uracil and its metabolites from exogenous uracil.

Using synchronous cultures similar results were obtained with cells at other developmental stages.
Lipid Metabolism in Dehydrating Peanut Kernels
Authors: MOHAPATRA SUBHAS C. , PATTEE HAROLD E.
Published: April 2006

Metabolism of radioactive lipids in kernels from peant plants subjected to 14C2 under field conditions was studied during dehydration (curing) of the seeds at 22°C or 50°C. Synthesis of lipid was predominant during the first 6 to 12 hours of dehydration whereas degradation dominated between 12 to 24 hours of curing. These changes were related to the moisture content of the dehydrating kernels; a moisture range of 42 to 47% was found to be an important factor influencing the observed pattern of lipid metabolism. The results from the present study also indicate compartmentalization of lipid metabolism in dehydrating peanut kernels.
Oscillatory Transpiration and Water Uptake of Avena Plants
Authors: BROGÄRDH T. , JOHNSSON A.
Published: April 2006

Xylem vessels in the lower part of the leaf of young Avena plants have been exposed to deformation by application of an external pressure. In this way a resistance to the water flow at the deformation site has been achieved, inducing undamped oscillations in transpiration and water uptake, even after removal of the root system.
The Light Induced Protochlorophyll–Chlorophyll a‐Transformation and the Succeeding Interconversions of the Different Forms of Chlorophyll
Authors: VIRGIN HEMMING I. , FRENCH C. STACY
Published: April 2006

Curve resolution into Gaussian components of the absorption spectra during the varying stages of the Shibata shift in dark grown, irradiated leaves of barley indicates that the chlorophyll a forms formed after irradiation consist of the same main components which have been reported to be present in all hitherto investigated plant materials (peak values in the red region 662, 670, 677 and 683 nm, respectively) but in varying proportions. The spectra during the Shibata shift proper can be satisfied by a mixture of two single components gradually changing their proportions, although a four component system gives a still better fit to the measured absorption curves. It is also shown that curves taken before and after the shift and added together in the appropriate proportions will match the absorption spectrum measured with peak at the isosbestic point (after ca. 15 min at room temperature).
Nucleotide Metabolism during Pine Pollen Germination
Authors: NYGAARD PER
Published: April 2006

The metabolism of purine‐ and pyrimidine nucleotides in pine pollen (Pinus mugo) grown in suspension cultures have been examined.

In the ungerminated dehydrated pollen, the presence of ATP has been demonstrated. Incubation of the pollen in a germination medium leads to an exhaustion of the ATP pool, which is restored with the onset of oxygen uptake.

By labelling pollen cultures with 32P‐orthophosphate, it has been possible to quantitate the nucleotide components of the pollen, and thereby to measure changes in the nucleotide pattern at various growth stages. The most marked changes occur during the initial phase of tube growth when a large increase in the ribonucleoside triphosphate and the sugar nucleotide pools is observed. The contents of ATP and UDP‐glucose are further increased if starch synthesis is initiated by the addition of sucrose to the culture medium.

In order to determine whether nucleotides in pine pollen are synthesized from de novo pathways or via reutilization pathways, from breakdown products of nucleic acids, pollen was incubated with 14C‐labelled precursors of both the de novo and the reutilization pathways. Incorporation experiments established de novo synthesis of ATP and GTP from glycine, and de novo synthesis of CTP and UTP from orotic acid. The operation of pathways for the utilization of exogenous nucleosides was also demonstrated. While uridine, cytidine and adenosine are incorporated into nucleoside triphosphate to a great extent, only minor incorporation of inosine and guanosine is observed. These reutilization pathways might be of importance for the synthesis of nucleotides during tube growth in situ.

Addition of inhibitors of glycolysis and oxidative phosphorylation drastically reduces the level of ribonucleoside triphosphates, indicating a rapid turnover of the nucleotide pool.
Subcellular Distribution of Picloram
Authors: BAUR J. R. , BOWMAN J. J.
Published: April 2006

Gas chromatographic and radioisotopic analyses were made of cell wall, chloroplast, mitochondria and the remaining cytoplasm fractions of cowpea (Vigna sinensis Endl. cv. Southern Blackeye) trifoliates acropetal to primary leaves treated with the growth regulator 4‐amino‐3,5,6‐trichloro‐picolinic acid (picloram). The majority of picloram was recovered from the remaining cytoplasm. Concentrations in chloroplasts and mitochondria were consistently low.
Characteristics of the Uptake Mechanism of Chloride Ions in Excised Roots of a Woody Plant (Citrus)
Authors: ALTMAN A. , MENDEL K.
Published: April 2006

The characteristics of the uptake mechanism of chloride ions in citrus (Citrus spp.) were studied in excised, high‐salt, roots as to the nature of the isotherm at a wide range of uptake durations and Cl− concentrations. In addition, the effects of metabolic inhibitors, low temperature and various treatments were studied, and compared with Cl− uptake in excised roots of wheat (Triticum vlgare) under the same conditions.

It was found that the uptake mechanism in excised roots of citrus differs considerably from that in wheat: (1) the rate of active uptake from 10 mM NaCl in citrus is 2.0 to 4.3 umol Cl− per g dry weight and h (vs. 35.5 umol in wheat); (2) there is no saturation of the system even at high external concentrations (up to 90 mM), and uptake is continuous; (3) uptake in citrus is less sensitive to KCN and dinitro‐phenol. In addition, it was noted that the age of citrus seedlings and the initial chloride content of both citrus and wheat roots markedly affected Cl− uptake.

The data were analyzed in the light of the dual mechanism hypothesis of ion uptake, and it was concluded that only system 2 (high Km), is operating in the excised citrus roots studied. This is in accordance with the conditions prevailing in the field (whence the plant material was collected): high concentration of the soil solution in contact with the roots, and high salt status of the tissue. It is further suggested that the uptake of ions in citrus (and presumably in other perennial woody plants), is related to its growth habits and to the size and morphology of the root systems.
Passive and Active Components of Chloride Absorption in the Bark and the Wood of Citrus Roots
Authors: ALTMAN A.
Published: April 2006

The characteristics of chloride absorption by the tap root of citrus (Citrus spp.) seedlings were compared in isolated disks of the bark and in segments of the wood. Analysis of elution curves of the isotope following saturation of the tissue shows that there are at least two components of the chloride absorption system: one typical of the free space (“passive”) and the other of the non‐free space (“active”). These two components are present in the bark only, while the wood has essentially the characteristics of a free space absorption (the slow component of the efflux being less evident). The nature of the bark as an actively collecting tissue for chloride from 10 mM Na36Cl, in contrast to the wood, was established on the basis of uptake curves. Examination of the uptake in the bark of 3 citrus varieties revealed considerable differences with regard to the magnitude of the two components of chloride absorption. These findings are discussed in relation to the role of the cortex and the stele in the transport of ions.
On Extraction and Quantitation of Plant Peroxidase Isoenzymes
Authors: LEE T. T.
Published: April 2006

Peroxidase in tobacco callus tissue differed in extract‐ability depending on the subcellular distribution of the enzyme. Based on extractability it consisted of four fractions: freely soluble and less freely soluble in phosphate buffer, KCl‐soluble, and insoluble. The latter two fractions were un‐extractable by a phosphate buffer alone. The different fractions contained varied proportions of peroxidase isoenzymes. The extractability of indoleacetic acid oxidase was similar. A medium of high ionic strength is essential for quantitative extraction of peroxidase and indoleacetic acid oxidase isoenzymes.

For quantitation of isoperoxidase activity on polyacryl‐amide gel following electrophoretic separation, benzidine and o‐dianisidine were better hydrogen donors than guaiacol and pyrogallol. The optimum pH was 4.5, but a citrate buffer was inhibitory. The optimum conditions included an acetate buffer at pH 4.5, a substrate concentration of 0.03 %, benzidine as the hydrogen donor, and a 3‐minute treatment with 7 % acetic acid after staining. The color intensity of the bands remained unchanged for at least three days. With appropriate sample size and reaction time there was a linear relationship between enzyme concentration and activity.
Polyamines Bound to tRNA and rRNA of Eukaryotic Plant Organisms
Authors: BAGNI NELLO , STABELLINI GIORDANO , FRACASSINI DONATELLA SERAFINI
Published: April 2006

The occurrence of polyamines in different RNAs was investigated in view of the importance of these organic cations in RNA function. RNA was extracted at low ionic strength and separated on Sephadex columns.

tRNA and rRNA of plants (Spinacia oleracea leaves, etiolated epicotyls of Pisum sativum, and Neurospora crassa mycelia) contain polyamines although in a different ratio than they are found in a complete cell. Contrary to spermine and putrescine, spermidine is always present.

The binding of polyamines to tRNA and rRNA is discussed applying the Liquori model to the double stranded regions, where it was possible.

Polyamines were also detected in 5S RNA.
Seed and Embryo Germination in Syringa vulgaris and S. reflexa as Affected by Temperature during Seed Development
Authors: JUNTTILA OLAVI
Published: April 2006

Effects of controlled temperature conditions during seed development on seed and embryo germination of Syringa vulgaris were studied using vegetatively propagated mother plants. Seeds from mother plants grown at 18–24°C were partially dormant at low (15°C) but not at high (21°C) germination temperature, while seeds from outdoors or from plants grown at 12°C were not dormant at all. Seed dormancy at low temperatures was induced as well when branches from outdoor plants were kept at 18–24°C for the last two‐three weeks before harvesting. The dormancy induced by 24°C during seed development was not broken by keeping branches at 12°C for the last two‐three weeks. In most cases the induced seed dormancy was broken completely by gibberellic acid.

Embryo germination at 24 or 15°C was not affected by mother plant temperature. Part of the embryos from plants grown at 24°C were, however, dormant at 9°C. The ability of embryos to germinate in osmoticum was only slightly affected by mother plant temperature.

The mechanical resistance of the endosperm was significantly higher in the seeds from plants grown at 24°C than in seeds from 12°C.

Both the embryos and the seeds of S. reflexa were dormant at the time of termination of embryo elongation. Experiments with three seed‐propagated mother plants indicated that the water potential of embryos may be reduced by high mother plant temperature.
Cytokinin‐induced Pseudonodules on Alnus glutinosa
Authors: RODRIGUEZ‐BARRUECO C. , DE CASTRO F. BERMUDEZ
Published: April 2006

Alder root nodules are capable of atmospheric nitrogen fixation. A differential treatment with kinetin and 2IP (2‐isopentenyl adenine) was applied to the rooting medium of alder plants growing in test tubes containing Crone solution. The experiment led to the formation of a fair number of pseudonodules scattered on the root system of the plants treated with cytokinin levels higher than 0.6 μg/ml. Kinetin had a lowering effect on the overall growth of the plant, whereas the plants treated with 2IP showed no differences in growth as compared to the non‐treated control plants. Histological sections of the pseudonodules show an unorganized tissue originating from the parental root cortex, and the presence of groups of tracheids giving the aspect of unorganized vascular bundles.
Uptake, Cellular Distribution, and Metabolism of 14C‐picloram by Excised Plant Tissues
Authors: SHARMA M. P. , BORN W. H. VANDEN
Published: April 2006

Excised soybean (Glycine max (L.) Merr.) hypocotyls, barley (Hordeum vulgare L.) coleoptiles, barley leaf sections, and Canada thistle (Cirsium arvense (L.) Scop.) leaf discs continuously absorbed 14C‐picloram from a buffered solution over a 24 h period. After an 8 h uptake period excised sections released up to 30 % of the absorbed picloram into ‘clean’ buffer solution in a 4 h period. Leaf sections released less than did the other tissues. Uptake of 14C‐picloram by soybean hypocotyl and barley coleoptile sections increased with an increase in temperature from 5 to 35°C. Uptake was promoted by added ATP and sucrose but inhibited by actinomycin D, cycloheximide, and DNP.

After differential centrifugation of aqueous extracts of 14C‐picloram‐treated excised tissues more than 95 % of the radioactivity was in the soluble fraction.

In excised barley and Canada thistle leaf tissues, 3 days after treatment, part of the 14C‐picloram was conjugated with plant constituents, largely with sugar(s). After acid hydrolysis of ethanol extracts of such tissues only unaltered picloram was detected. In barley coleoptile and soybean hypocotyl sections no conjugation products of 14C‐picloram were detected.
The Inhibition by Cytokinin of Auxin‐Promoted Elongation in Excised Soybean Hypocotyl
Authors: VANDERHOEF LARRY N. , STAHL CATHERINE , SIEGEL NED , ZEIGLER ROBERT
Published: April 2006

The experiments characterize the inhibition by kinetin of auxin‐promoted elongation in excised hypocotyl sections of 3‐day soybean seedlings (Glycine max cv. Hawkeye 63). It was found that concentrations of kinetin above 4.2 μM did not further inhibit auxin‐promoted elongation. Kinetin is as potent an inhibitor of elongation as actinomycin D or cycloheximide. Tissue incubated for 3 or 5 h in the absence of auxin or cytokinin would, upon addition of auxin, exhibit a new growth rate similar to that of tissue grown in auxin for the entire incubation period. Similarly, tissue grown for 3 and 5 h in the presence of auxin would revert to the control rate of elongation upon addition of kinetin. A 10 to 30 min preincubation in kinetin yielded the tissue incapable, for the ensuing 6 h, of increasing its rate of elongation in response to auxin. Zeatin and isopentenyladenine were more potent than kinetin and benzyladenine in the inhibition of elongation. Levels of ethylene produced in the presence of auxin plus cytokinin indicated that it was not involved in this auxin‐cytokinin interaction. Kinetin by itself did not promote elongation; nor did it enhance auxin‐promoted elongation at low auxin concentrations.
Studies of the Biochemical Background to Differences in Glucosinolate Content in Brassica napus L. III. Further Studies to Localize Metabolic Blocks
Authors: JOSEFSSON EGON
Published: April 2006

To localize the metabolic block(s) in the biosynthesis of glucosinolates in the Brassica napus L. cv. Bronowski, 5‐methylthiopentanal oxime‐1‐14C was synthesized and fed to this cultivar and cv. Regina II, which has average levels of glucosinolates. The aldoxime was as efficient as a precursor of 3‐butenylglucosinolate in both cultivars, but less efficient as a precursor of 2‐hydroxy‐3‐butenylglucosinolate in Bronowski. These results suggest that there is a block in the biosynthesis of 3‐butenylglucosinolate in Bronowski that is situated before the synthesis of the intermediate 5‐methylthiopentanal oxime, as well as a block in the hydroxylation step.

The silique walls of Bronowski contained increased amounts of total sulphur and inorganic sulphate.
Ozone Alteration of Nitrate Reduction in Soybean
Authors: TINGEY DAVID T. , FITES ROGER C. , WICKLIFF CARLOS
Published: April 2006

Soybeans [Glycine max (L.) Merr.] were harvested at various periods after a 2 h exposure to determine the effects of ozone on nitrate reductase and selected metabolites related to nitrate reduction. Ozone initially depressed the concentrations of reducing sugars, amino acids, and nitrate reductase activity. On subsequent days following exposure, amino acid and protein levels were higher than the respective controls while the levels of reducing sugars and nitrate reductase activity returned to control levels. The ozone depression of nitrate reduction was not the result of a direct ozone reaction with the nitrate reductase protein but rather an interference with reactions that supplied the NAD(P)H needed for nitrate reduction.
Synergism between Gibberellin and Auxin in the Growth of Intact Tomato
Authors: GRUNWALD C. , LOCKARD R. G.
Published: April 2006

Gibberellin A4&7 was more effective than gibberellic acid in increasing shoot elongation when applied to the apex of intact Lycopersicum esculentum seedlings of Tiny Tim, a dwarf cultivar, and Winsall, a tall cultivar. After 14 days, gibberellic acid and gibberellin A4&7 stimulated growth of the dwarf more than the tall tomato. In tall tomato the application of indole‐3‐acetic acid alone (6.1 μg/plant) showed an inhibitory growth effect, but when applied with 17.5 μg per plant of gibberellic acid, it had a synergistic effect at 7 days but not at 14 days. When the auxin concentration was reduced to 0.61 μg per plant a synergistic effect was observed on tall plants at 7 and 14 days between indole‐3‐acetic acid and gibberellic acid. Application of gibberellin A4&7 with auxin did not give a synergistic response in tall or dwarf tomato.
X‐Ray Analysis of Microelements in Seeds of Crambe abyssinica
Authors: v HOFSTEN ANGELICA
Published: April 2006

X‐Ray microanalyses were made by scanning electron microprobe on thin sections of seeds of Crambe abyssinica. Linear scan profile and multilinear scan image of X‐ray emissions for magnesium, calcium and sulphur were compared. It was also possible to detect these elements in point analyses in the globoid region in the protein bodies of the seed. Microanalyses were also made with the EDAX system and with EMMA analytical electron microscope.
The Effect of Oxygen on Endogenous Cytokinin Levels and Germination of Leucadendron daphnoides Seed
Authors: VAN STADEN J. , BROWN N. A. C.
Published: April 2006

The soybean callus assay was used to study the effect of high oxygen tensions on the cytokinin levels of Leucadendron daphnoides Meisn. seed, where dormancy is apparently due to the restricting effect of the seed coat on oxygen diffusion to the embryo. High oxygen tensions led to a six‐fold increase in germination compared to seed incubated in air and resulted in significant increases in butanol soluble cytokinins prior to visible germination. It is suggested that the primary effect of oxygen is to increase the rate of respiration and thus, to provide the energy required for the synthesis of butanol soluble cytokinins which leads to cotyledon expansion and subsequent radicle elongation. Present indications are that untreated seeds remain dormant due to low concentrations of butanol soluble cytokinins in their embryos.
Metabolism of Carbon‐14 Labelled Arginine, Citrulline and Ornithine in Intact Apple Stems
Authors: HILL‐COTTINGHAM D. G. , LLOYD‐JONES C. P.
Published: April 2006

A study was made of the absorption and metabolism of arginine‐guanido‐14C, citrulline‐carbamyl‐14C and ornithine 1‐14C which had been applied to apple stem internodes by a perfusion technique at intervals throughout the year.

The results showed that these amino acids were interconverted according to the Krebs‐Henseleit cycle always in the direction arginine‐ornithine‐citrulline‐arginine. In addition ornithine was degraded by another pathway with loss of CO2. This loss was particularly extensive during the period June to August when labelled proline and glutamic acid were also found. The evidence is consistent with the initial breakdown of ornithine taking place via glutamic semi‐aldehyde.
Auxin Stimulation of Cambial Activity in Pinus silvestris I. The Differential Cambial Response
Authors: CZKOWSKI STEFAN ZAJA
Published: April 2006

Isolated stem segments of Pinus silvestris L. produce new xylem in sterile culture for 5 weeks if sucrose and IAA are present in the medium. The response of cambium varies in the course of the season and along the tree stem. The cambium is more sensitive in spring and in the stem portion closer to tree apex than later in the season and closer to the stem base. Spring initiation of cambial activity in adult pine trees under natural conditions could not be correlated with any consistent concentration gradient of natural auxin extracted from the cambial region. Thus, the relation between concentration of auxin and the activity of cambium is complex and involves changes of cambial responsivity. Interaction with gibberellic acid or kinetin and changing concentration of sucrose were studied during the season, but none of these substances alone appeared to be responsible for the observed variation in cambial response to auxin.
Correlative Changes in Endogenous Hormone Levels and Shoot Growth Induced by Short Heat Treatments to the Root
Authors: ITAI CHANAN , BEN‐ZIONI ALIZA , ORDIN LAWRENCE
Published: April 2006

Heat treatments of two minutes at 46 to 47°C to root systems of Nicotiana rustica and Phaseolus vulgaris affected roots and shoots. Xylem exudate of Phaseolus was collected, and it was found that heat treatment reduced cytokinin levels and increased abscisic acid levels in the exudate. Shoot and root growth of both species was reduced. Root membrane integrity of Nicotiana was measured and was found to be impaired. It is suggested that the changes in hormone activity due to heat treatment regulate the reduction in shoot growth. Cell wall metabolism and glucosyl transferases making β‐glucans were investigated in Phaseolus leaves. Incorporation of 14C from 14CO2 into wall constituents was slightly inhibited but neither photosynthesis nor extracted β‐glucan synthetases were affected during the first 12 hours after treatment.
Citrate Synthase of Plants: Sensitivity to Sulfhydryl Reagents and Molecular Weight of the Enzyme
Authors: GREENBLATT GERALD A. , SARKISSIAN IGOR V.
Published: April 2006

Citrate synthase of wheat (Triticum aestivum L.), bean (Phaseolus vulgaris L.), cauliflower (Brassica oleracea L.), and a marine blue‐green alga (Coccochloris elabens) is inhibited by sulfhydryl binding reagents. The inhibitions are partially reversed by dithiothreitol. Pig heart citrate synthase is only slightly inhibited by the same reagents and this is completely reversed by dithiothreitol.

All citrate synthases in this study are inhibited by adenosine triphosphate. The inhibition is relieved by increasing the concentration of acetyl coenzyme A.

Citrate synthase of wheat, cauliflower, bean, and pig heart was estimated by gel filtration to have a molecular weight of 100,000 daltons. The Coccochloris citrate synthase was estimated to have a molecular weight greater than 250,000 daltons.

The evolutionary implications of these findings are discussed.

This enzyme is comparable in size to the 100,000 dalton mammalian enzyme (Singh et al. 1970) making it somewhat larger than the 65,000 dalton mango enzyme (Srere et al. 1971). The PHMB‐treated enzyme also shows changes in its electrophoretic properties (Greenblatt and Sarkissian unpublished).

The evidence presented here demonstrates that citrate synthase of various plants is sensitive to sulfhydryl reagents suggesting that sulfhydryl reactivity is a not unusual property of plant citrate synthase. In addition we show that molecular weight as large as or larger than that reported in microbial systems can occur in a blue‐green alga.
Incorporation of Uracil by Synchronous Chlorella
Authors: KNUTSEN GJERT
Published: April 2006

Light‐dark synchronized Chlorella fusca was used to study the incorporation of radioactive uracil into the trichloroacetic acid insoluble fraction.

In autospores the incorporation measured in darkened cells usually started immediately after uraci addition, and the time course showed three distinct linear phases with abrupt transitions between them. Chromatographic analyses of the radioactive pool components showed that the total amounts of monophosphate, diphosphate and triphosphate nucleotides of uracil did not limit the incorporation and thus did not cause the abrupt rate shifts.

In autospores, 5, 9 and 14 h old cells, the initial incorporation rate increased with increasing initial uracil concentration to reach a constant value above 0.5 μ.M. Addition of glucose to the cells increased the incorporation rate over the whole uracil concentration range tested with autospores, but did not influence the rates of the other cells.

The incorporation rate varied during the synchronous cycle in a manner which closely resembled the pattern for uptake and degradation rates, with the most pronounced similarity from 9 h onwards.
Cytokinins in Populus×robusta: Qualitative Changes during Development
Authors: HEWETT E. W. , WAREING P. F.
Published: April 2006

Qualitative changes of cytokinins in leaves of different ages from Populus x robusta (Schneid.) have been determined, together with seasonal changes in cytokinin activity in mature leaves and xylem sap. Chromatography on Sephadex LH‐20 has shown that total cytokinin activity and diversity are at a maximum in expanding leaves. As leaves age, the amount and number of cytokinins decrease, with yellow senescent leaves having only one detectable cytokinin, thought to be a glucoside.

Seasonal changes were followed by chromatography of the extracts on paper in butan‐2‐ol: 25 % NH4OH (4:1). Maximum cytokinin levels, due to Fraction Z (Rf 0.5–0.8), in leaves and xylem sap were found in mid‐summer. Prior and subsequent to cessation of shoot elongation growth, fraction Z decreased and fraction N (Rf 0–0.2) increased to predominate in senescent leaves. Removal of the apex resulted in an increase of fraction N in leaves from decapitated plants when compared to similar leaves from intact plants. It is suggested that, once apical sink activity has ceased, cytokinins in the xylem sap are diverted into leaves and converted to a cytokinin glucoside, possibly a storage form of the hormone.
Effect of Water Quality on Relationships Between Cationic Species and Leaf Lipids at Two Different Development Stages in Cotton
Authors: TWERSKY M. , FELHENDLER R.
Published: April 2006

Lipid and phospholipid content of cotton leaves were measured in plants irrigated with fresh water and brackish water. The correlation between K+ and Na+ in leaf tissue and the changes in total lipids and phospholipids was determined at the vegetative and fruiting stages. Data demonstrated that total lipids and phospholipids can be associated with changes in the K/Na ratio and with the two developmental stages of the cotton plant. Plants irrigated with brackish water had more total phosphate incorporated into the phospholipids in the fruiting stage.
Changes in Polysomes of Black Locust Seedlings during Dehydration‐Rehydration Cycles
Authors: BRANDLE JAMES R. , SCHNARE PAUL D. , HINCKLEY THOMAS M. , BROWN GREGORY N.
Published: April 2006

Net assimilation, dark respiration and xylem pressure potential were followed through dehydration‐rehydration cycles in black locust seedlings (Robinia pseudoacacia L.). Sucrose gradient profiles indicated the retention of polysomes during stress. RNase activity declined during dehydration but returned to pre‐stress levels upon irrigation. Comparisons of black locust and corn polysomes during water stress are made.
Role of Pressure in Xylem Transport of Coconut and Other Palms
Authors: MILBURN JOHN A. , DAVIS T. ANTONY
Published: April 2006

The significance of root pressure in the transport of xylem sap has been investigated in Cocos nucifera L. and a few other palms. Despite the fact that excised palm roots can generate considerable pressures in situ, the quantity of water transported is only a small fraction of the demand resulting from transpiration. Most water transport is induced by negative pressure gradients, as in other higher plants. The development of considerable negative pressures has been demonstrated both directly and indirectly.

Acoustic detection was used for the first time to monitor cavitation in water‐stressed Cocos leaves. Its detection implies the ready disruption of xylem sap under these tensions. We suggest that root pressure might serve to refill cavitated xylem conduits when water is abundantly available and transpiration practically zero. However, little or no positive pressure could be demonstrated in intact palms subjected to low water stress: experimentally.
The Influence of Varying Light Intensities on the Photo‐transformation of Protochlorophyllide636 in Dark Grown Wheat Leaves Treated with δ‐Aminolevulinic Acid
Authors: SUNDQVIST CHRISTER
Published: April 2006

Leaves treated with δ‐aminoievulinic acid accumulate protochlorophyllide636 in large amounts. Due to a continuous conversion of protochlorophyllide636 (nonphototransformable) into protochlorophyllide650 (phototransformable) in weak red light, the photoreduction of protochlorophyllide to chlorophyllide can proceed for at least 20 minutes and results in a chlorophyllide content of the leaves three times higher than that in untreated leaves. The half time for this chlorophyllide accumulation is 55 seconds. A photodestruction of the pigments takes place at high light intensities or if the content of protochlorophyllide636 is high. The conversion of protochlorophyllide636 to chlorophyllide is dependent on the light intensity used for phototransformation of protochlorophyllide550 The conversion of PChlide646 was not limiting for chlorophyllide formation within the range of the light intensity used. The extrapolation of a double reciprocal plot of chlorophyllide formation, rate versus light intensity gives a maximal value of 8.7 μg chlorophyllide per g fresh weight and min. The conversion of protochlorophyllide363 to protochlorophyllide650 is believed to depend on the available sites of an apophotoenzyme.