bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiology and Chemistry of Substances Accelerating Abscission in Senescent Petioles and Fruit Stalks
Authors: DÖRFFLING KARL , BÖTTGER MICHAEL , MARTIN DOROTHEA , SCHMIDT VOLKER , BOROWSKI DETLEF 
Published: April 2006

AbstractSenescent petioles of Coleus rehneltianus Berger. Phaseolus vulgaris L. cv. Saxa. Acer pseudoplatanus L., and senescent fruit stalks of Malus domestica Borkh. cv. Golden Delicious contain at least three abscission accelerating substances, which were isolated by extraction with methanol or with water and by diffusion into agar. They were purified by thin‐layer chromatography and bioassayed in a special abscission test using Coleus explants. Two of these abscission accelerators could be conclusively identified by thin‐layer chromatography and by gas chromatography as abscisic acid and xanthoxin. The third substance, which has acidic properties and is less polar than abscisic acid, could not be identified. The concentration and the absolute amount of abscisic acid in Coleus petioles were found to decrease during their development, young petioles having the highest concentration. No evidence was found that the three abscission accelerators or synthetic abscisic acid and xanthoxin affect the production of ethylene in Caleus explatns. The results obtained do not support the hypothesis that senescent petioles contain a specific “senescence factor”, which stimulates abscission via ethylene production.
Effects of Frost Hardening and Dehardening on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris
Authors: MARTIN BJÖRN , MÅRTENSSON OLLE , ÖQUIST GUNNAR 
Published: April 2006

AbstractPhotosynthetic electron transport and low‐temperature fluorescence emission properties have been analyzed in isolated chloroplasts during the course of frost hardening and dehardening of Pinus silvestris L. Both the partial electron‐transport reactions (H2O DPIP and Asc./DPIP NADP) and the overall electron transport (H2O — NAPD) showed decreasing capacities during the course of hardening. Upon exposing the plants to −5°C and high irradiance a block in the electron‐transport chain between the two photosystems developed, whereas the partial reactions still showed activities. The decrease in activity of PSl was accompanied by a decrease in P700 content, as determined by light oxidation of P700, which indicates a correlation between the two changes.Hardening also induced changes in the in vivo chlorophyll organization. During the course of hardening the fluorescence emission bands F692 and F726 decreased relative to F680. These changes were more pronounced if the plants were treated in high than in low irradiance. This suggests a greater destruction of the chlorophyll antennae in close association with the two photoreactions than in the so‐called light‐harvesting chlorophyll a/b antenna.During dehardening basically the reverse of the changes observed during hardening occurred. The recovery of secondary needles was complete, whereas primary needles only partly recovered.
Reassessment of the in vivo Assay for Nitrate Reductase in Leaves
Authors: HEUER BRURIA , PLAUT Z. 
Published: April 2006

AbstractThe in vivo assay procedure for nitrate reductase and its dependence on the concentration of nitrate and other ions were examined. It was found that high ion concentrations led to an increased release of nitrite to the reaction media which could be interpreted as a stimulated nitrate reductase activity. This phenomenon is not an osmotic effect, since equivalent concentrations of mannitol did not lead to identical results. The effect of ions on the enhanced nitrite production was attributed to changes in cell membrane permeability rather than to a supply of substrate. This conclusion is based on several findings: (a) in in vitro assays, the rate of nitrite production was not affected by ion concentrations: (b) the stimulation of nitrite production was obtained by various ions and not only by nitrate; (c) pretreatment of alfalfa leaves with nitrate did not increase the NO2− release rate to the external solution; and (d) nitrate and nitrite export from leaf discs to the solution was stimulated even in discs which were enzymatically inactive. Calcium ions in the presence of KNO3 inhibited the enhanced nitrite production, probably due to alteration of membrane stability.The effect of ions on the rate of nitrite production was reversible and the high rate of nitrite production was reduced to the control rate when discs were transferred to a solution of low concentration.
Oscillations in the Activities of Enzymes of Nitrate Reduction and Ammonia Assimilation in Glycine max and Zea mays
Authors: DUKE STANLEY H. , FRIEDRICH JAMES W. , SCHRADER LARRY E. , KOUKKARI WILLARD L. 
Published: April 2006

AbstractThe activities of glutamate dehydrogenase (GDH), glutamine synthetase (GS), and nitrate reductase (NR) and the levels of soluble protein and NO‐3 were assayed in soybean (Glycine max [L.] Merr.) leaves over a 48‐h period with the initial 24 h under a light‐dark cycle (LD 16:8) followed by 24 h of continuous light (LL). Plants had been entrained for 30 days under the LD regime. Maize (Zea mays) leaves (10 days old) under a LD 15:9 cycle were assayed only for NR and nitrite reductase (NiR). Data were subjected to frequency analysis by the least squares method to determine probabilities for cosine function periods (τ's) between 10 and 30 h. NR activities for both soybean and Zea leaves had 24 h τ's with P values < 0.05 indicating circadian periodicity. GDH in soybeans had a 24‐h rhythm under LD conditions which lengthened under LL conditions. The 24‐h rhythm of GDH displayed maximal activity toward the end of the dark period of the LD cycle whereas the highest activity of NR was early in the light period. Total soluble protein displayed a rhythm with a best fitting τ of greater than 24 h under both LD and LL. GDH, GS, NR, NO3, and soluble protein in soybeans and NiR in Zea, all displayed that were ultradian (10–18 h), indicating that a τ of about one half a circadian periodicity may be a common characteristic of the enzymes of primary nitrogen metabolism in higher plants. These data also demonstrate that although both NR and GDH are circadian in their activity, the 24‐h rhythm may be greatly influenced by ultradian oscillations in activity.
Influence of CO2 on Reduction of Nitrate in Corn Seedlings
Authors: STULEN INEKE , LANTING L. 
Published: April 2006

AbstractThe influence of CO2 on the assimilation of nitrate in intact corn seedlings was measured with 15N labelled nitrate, 24 and 48 h after the dark‐grown seedlings were transferred to the light, either in normal air or in CO2‐free air. During the first 24 h CO2 had no influence on nitrate reduction in intact seedlings. Experiments with detopped seedlings showed that during this period the roots were the only site of nitrate reduction. After 48 h seedlings grown in normal air had reduced more nitrate than detopped seedlings, and seedlings grown in CO2‐free air had reduced the same amount of nitrate as detopped seedlings. During the whole 48 h period CO2 had no influence on the level of nitrate reductase of the leaves. It was concluded that in normal air corn leaves started to reduce nitrate after a lag period of 24 h and that in CO2‐free air they were incapable of nitrate reduction.
Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels
Authors: NAIR T. V. R. , GROVER H. L. , ABROL Y. P. 
Published: April 2006

AbstractUpper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.‐1) increased significantly due to soil N application (N30 over N0). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)‐1 revealed that two‐thirds of N is translocated by 28‐day stage and the rest between 28‐day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)‐1 at N0, N30 and N120‐ respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.
Degradation of Muskmelon Cell Wall by the Xylanases of Colletotrichum lagenarium
Authors: DOUX‐GAYAT A. , AURIOL P. , JOSELEAU J. P. , TOUZÉ A. 
Published: April 2006

AbstractXylose‐rich polysaccharide fractions were isolated from cell walls of muskmelon (Cucumis melo L. cv. Cantaloup Charentais) stems. A xylan with a (1 → 4) linked backbone has been characterized as a component of these fractions. Two xylanases excreted by the fungus pathogen Colletotrichum lagenarium were able to degrade this substrate both after extraction and when it was included in the crude cell walls. The results suggest that the xylanases are involved in the parasitism of this pathogen.
Optimum Conditions for Indoleacetic Acid Oxidase Extraction from Betula Leaves
Authors: HOYLE MERRILL C. 
Published: April 2006

AbstractThis report deals with total extraction and activation of soluble indoleacetic acid oxidase from Betula alleghaniensis leaves as affected by different buffers, varying pH, phenol binder, detergent, plus volume and time parameters. For all buffers and pH levels tested, only tris pH 8 gave a high activity. This result was not a pH effect, since a wide‐range, citrate‐phosphate buffer at pH 8 gave a very low activity. Addition of a neutral detergent, Triton X‐100, to all buffers gave considerable activity in every case. Most activity with Triton X‐100 occurred at pH 6 and least at pH 8 regardless of buffer composition. A phenol binder, polyvinylpyrollidone, increased activity also, but less than the detergent Triton X‐100. Both of these compounds in combination gave an additive effect and the highest measure of enzyme activity. Further increases in measurable indoleacetic acid oxidase activity were obtained by using the best combination of these factors to determine the optium tissue: buffer ratio and optimum soaking time. Increases in activity of 70 and 60%, respectively, were achieved.
Phycochrome d, a New Photochromic Pigment from the Blue‐Green Alga, Tolypothrix distorta
Authors: BJÖRN G. S. 
Published: April 2006

AbstractA new reversibly photochromic pigment, phycochrome d, has been found in extracts of the blue‐green alga Tolypothrix distorta. This phycochrome exhibits an absorbance increase in the red region (maximum at about 650 nm) when irradiated with 650 nm light, and a corresponding absorbance decrease when irradiated with 610 nm light. The absorbance difference spectrum and action spectra for in vitro conversions were determined.
Adenosine 3′:5′‐Cyclic Monophosphate in Normal and Habituated Helianthus Callus
Authors: TRUELSEN T. A. , WYNDAELE RITA 
Published: April 2006

AbstractA compound with properties identical to adenosine 3’:5′‐cyclic monophosphate (cAMP) has been isolated from callus of Helianthus annuus. The compound accompanied cAMP during an extensive purification procedure and co‐chromatographed with cAMP in three solvent systems. The compound stimulated cAMP‐dependent protein kinase and was active in a cAMP protein‐binding assay. Its activity was abolished by cAMP phosphodiesterase. It is concluded that the compound is cAMP.The variation in cAMP content in the callus during its development was determined. In 1974 when the stock callus was grown on auxin‐containing medium the content was c. 2 pmol cAMP/g when the cells were vigorously dividing and c. 125 pmol cAMP/g two weeks after the transfer. In 1976 the callus had attained hormone autotrophy. Its cAMP content was generally low during the whole developmental cycle.The results might indicate that cAMP played a role in the development of the normal callus of 1974, while it has no regulatory function in the tumour‐like tissues of 1976. The results are discussed on the basis of recent literature.
Variations dans ľexpression du pouvoir oncogène d'Agrobacterium tumefaciens
Authors: Le Goff L. , MANIGAULT P. 
Published: April 2006

Abstract Variations in the expression of the oncogenic power of Agrobacterium tumefaciens due to interactions between bacteria.The effects of the virulent strain A6 of Agrobacterium tumefaciens after co‐culture with non‐virulent variants of the same bacterium, or even with other bacterial species (e.g. Escherichia coli), showed that interactions between different strains of bacteria exist. These interactions are expressed as a phenomenon of either enhancement or inhibition, as shown by an increase or a decrease in the weights of tumors induced in decapitated stems of Pisum sativum L. cv. Annonay. These two phenomena depend on the contact time between the bacteria in mixed cultures (type I). With a short contact time between the two bacterial types (one or two generations), infections in decapitated pea stems produced by mixed inocula caused an increase in tumor weight compared with infections induced by inocula of virulent bacteria only. If the contact time was increased to the end of the log phase, a decrease in tumor weight was observed. Clarified supernatant fluids of spent media were also used as culture media (type II) for the virulent A6 bacteria. The stimulatory or inhibitory activity of (a) substance(s) present in these supernatant fluids depended on two variables: culture time of the bacteria A6 in the supernatant fluids and the “age” of the bacterial culture used to prepare them. Weight increase of the tumors was obtained if the proliferating time of the A6 bacteria in the supernatant fluids was short (4 h), or if the super natants were obtained from “young” cultures. Inhibition of the tumor expression occurred if the contact time of A6 bacteria in the supernatant fluids was increased or if the supernatants originated from bacterial cultures at the end of their growth. The in vitro interactions between the two bacterial strains in a mixed culture (type I or type II) were suppressed in the presence of pancreatic ribonuclease. Deoxyribonuclease had no effect. This provides indirect evidence for the action of a ribonucleic acid in the expression of the oncogenic power of a bacterial population of Agrobacterium tumefaciens.
Gibberellins and Inhibitors in Leaves of Tall and Dwarf Beans
Authors: GOTÔ NOBUHARU 
Published: April 2006

AbstractThe contents of GAs and growth inhibitors were investigated in the dwarf (cv. Masterpiece) and tall (cv. Kentucky Wonder) varieties of bean (Phaseolus vulgaris L.). The comparison of active substances was carried out by parallel extraction and fractionation from leaves of the two varieties followed by paper chromatography, thin layer chromatography (TLC) and bioassay, using lettuce hypocotyl growth test. Five GA‐like activities and six growth‐inhabiting activities, in which xanthoxin. ABA and bound ABA might be included, were detected in both dwarf and tall varieties. The levels of all of these GAs and inhibitors were almost identical between the two varieties. In both varieties GA3 treatment caused two inhibitory activities to decrease. The expression of dwarfism in the vegetative growth stages of beans may have to be discussed also on the basis of another factor than that of the levels of endogenous GA inhibitors.
The Influence of Colchicine on Initiation and Early Development of Adventitious Roots
Authors: OPPENOORTH J. M. 
Published: April 2006

AbstractThe first sign of adventitious root formation in the petiole of the primary leaves of Phaseolus vulgaris after treatment with IAA was the dedifferentiation of mature parenchyma cells next to strands of sieve elements and companion cells. Colchicine strongly inhibited this dedifferentiation. Treatment with colchicine 3 days after treatment with IAA, caused the groups of meristematic cells formed to grow by cell enlargement only. Groups of more than about 30 meristematic cells changed into recognizable root primordia during this growth. Groups with a smaller number of meristematic cells extended also in size but did not form a recognizable root primordium.
Oscillatory Transpiration and Water Uptake of Avena Plants
Authors: KLOCKARE RUNE , JOHNSSON A. , BROGÅRDH T. , HELLGREN M. 
Published: April 2006

AbstractThe transpiration rate of oat plants, 6 days old, has been investigated. Dependent on the irradiance level of the white light used in the experiments, the transpiration rate oscillated with different period times. In darkness or at low irradiances the period was about 100–110 min. At higher irradiances the period was about 40 min. At intermediate irradiances autocorrelation analysis was used to find the period content of the transpiration rate. It was concluded that two oscillatory systems were present in the plants, characterized by their different periods.When plants cultivated in a light/dark cycle were used, the transpiration oscillations were influenced by a circadian rhythm. Oscillations in darkness were then most pronounced in the mornings. Plants cultivated in continuous light did not show such a circadian rhythm, but the oscillations died out after about 20 h.Kinetin induced transpiration oscillations in darkness and made them sustain for a longer time.
Thermodormancy in Celery Seeds and its Removal by Cytokinins and Gibberellins
Authors: BIDDINGTON N. L. , THOMAS T. H. 
Published: April 2006

AbstractImbibition of celery (Apium graveolens L.) seeds at 32°C for up to 96 h lowered the upper temperature limit for germination. If this high temperature treatment was given in the light, these seeds germinated slightly earlier than those treated in the dark although the final percentage germination was similar for both treatments. The inhibitory effect of the high temperature treatment was completely removed by allowing the seeds to imbibe in a mixture of the gibberellins A4 and A7 (GA4/7) and partially removed by the cytokinin N6‐benzylaminopurine (BA). GA4/7 was less effective when added before rather than after the high temperature treatment, whereas the opposite was true of BA. At constant temperatures more GA4/7 was required to promote germination as the temperature was raised but addition of BA reduced the concentration of GA4/7 required. A model is proposed for the control of celery seed germination by light and temperature through the action of endogenous cytokinins and gibberellins.
Movement of Cell Organelles and the Geotropic Curvature in Roots of Norway Spruce (Picea abies)
Authors: HESTNES ARNOLD , IVERSEN TOR‐HENNING 
Published: April 2006

AbstractThe geotropic development in roots of Norway spruce [(Picea abies (L.)] H. Karst, has been followed by light and electron microscopy and compared with the movement of cell organelles (statoliths) in the root cap cells. The geotropic curvature develops in two phases: (a) an initial curvature in the root cap region, which results in an asymmetry in the extreme root tip and which appears after about 3 h stimulation in the horizontal position; and (b) the geotropic curvature in the basal parts of the root tip, which after 8 h is distributed over the entire elongation zone. A graphic extrapolation, based on measurements of the root curvatures after various stimulation periods, indicates a presentation time in the range of 8 to 10 min.The root anatomy and ultrastructure have been examined in detail in order to obtain information as to which organelles may act as gravity receptors. The root cap consists of a central core (columella) distinct from the peripheral part. The core contains three to four rows of parenchymatic cells each consisting of 15 to 18 storeys of statocyte cells with possibly mobile cell organelles. Amyloplasts and nuclei have been found to be mobile in the root cap cells, and the movement of both types of organelles has been followed after inversion of the seedlings and stimulation in the horizontal position for various periods of time at 4°C and 21°C. Three‐dimensional reconstructions of spruce root cap cells based on serial sectioning and electron microscopy have been performed. These demonstrate that the endoplasmic reticulum (ER)‐system and the vacuoles occupy a considerable part of the statocyte cell. For this reason the space available for free movement of single statolith particles is highly restricted.
Changes in the Activity of Acetyl CoA Carboxylase in Germinating and Ripening Sunflower Seeds
Authors: BHATIA I. S. , AHUJA K. L. , SUKHIJA P. S. 
Published: April 2006

AbstractActivity of acetyl CoA carboxylase was determined in germinating and maturing sunflower (Helianthus annuus L.) cv. Rum Sun Record seeds. A constant decrease was observed in germi nating embryos. Exposure of etioplasts to light intensity of 500 (74 mW . cm−2) lux for different time intervals decreased the activity of the enzyme in the embryos. A reverse trend was observed in ripening embryos where the ATP‐Pi exchange rate was found to be directly correlated to the activity of acetyl CoA carboxylase.
The Influence of Ambient Nitrate, Temperature, and Light on Nitrate Assimilation in Sudangrass Seedlings
Authors: HALLMARK W. B. , HUFFAKER R. C. 
Published: April 2006

AbstractSeedlings of Sundangrass (Sorghum Sudanese [Piper] Stapf.) were grown 10 to 13 days of age in a nutrient solution containing nitrate and then placed under treatment conditions for 24 h before assays of nitrate assimilation were begun. Nitrate uptake was determined by its disappearance from the ambient solution. In vivo reduction of nitrate was determined by the overall balance between the amount taken up and the change in tissue concentration of nitrate during the experiments. Nitrate reductase activity was determined from tissue slices. In vivo reduction was strongly regulated by uptake in response to time and ambient nitrate concentration, temperature and light. Nitrate reduction responded to the concentration of nitrate supplied by uptake and by a storage pool, since reduction often exceeded uptake. Nitrate reductase activity in tissue slices was exponential in initial response to increasing temperature. After a 24‐h equilibration period at each temperature, the activity was lower at higher temperatures. In contrast, actual reduction of nitrate increased linearly with increasing temperature between 15 and 24°C in the plants equilibrated 24 h at each temperature. Nitrate uptake and reduction were greatly inhibited under low light conditions, with reduction inhibited more than uptake., The effect of ambient nitrate, temperature, and light on the nitrate assimilatory processes help to explain observations reported on nitrate accumulation by Sudangrass forage.