bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence des racines sur le développement végétatif ou floral des bourgeons cotylédonaires chez le Scrofularia arguta: role possible des cytokinines
Authors: MIGINIAC EMILE 
Published: April 2006

Abstract Influence of roots on the vegetative or floral development of cotyledonary buds of Scrofularia arguta Sol.: A possible cytokinin role. This study shows that the presence of “nonabsorbing roots” insures a vegetative development of cotyledonary buds cultured in vitro whereas buds growing without roots produce flowers early. In the same way, roots suppress floral expression of axillary meristems of the same cotyledonary buds and induce these buds to vegetative functioning. Various trophic modifications in the culture medium are ineffective on non‐rooted buds as also are gibberellin As and adenine. On the contrary, several cytokinins (kinetin, benzyladenine and zeatin) exert the same influence as roots. These results suggest that roots regulate meristematic functioning through cytokinins.
Changes in the Cytokinins of Radish Roots during Maturation
Authors: RADIN J. W. , LOOMIS R. S. 
Published: April 2006

AbstractThe cytokinins of developing radish roots were extracted, partially purified, and separated by thin‐layer chromatography into three distinct bands of activity. One band was identified chromatographically as zeatin ribonucleotide and another was indistinguishable from a mixture of zeatin and zeatin ribonucleoside. The third band was not identified, but it was not a derivative of zeatin or of isopentenyladenine.The unidentified cytokinin had physiological properties quite different from those of the zeatin derivatives. The zeatin‐based cytokinins increased in radish roots with the onset of cambial activity, and reapplication of these cytokinins to cultured primary roots stimulated cambial activity. The unidentified cytokinin became abundant only after extensive secondary thickening had occurred, and it was localized almost entirely in the xylem. It did not stimulate cambial activity in cultured roots. The evidence indicates that zeatin and its derivatives regulate cambial activity in radish, and that the unidentified cytokinin may be synthesized in the roots and transported to the shoot.
Photosynthetic Uptake of Free CO2, by the Roots of Lobelia dortmanna
Authors: WIUM‐ANDERSEN S. 
Published: April 2006

Abstract Lobelia dortmanna L. is probably unable to utilize HCO3−and uses only free CO2 for photosynthesis as shown by the Winkler method. A 14C technique was used to show that if CO2 is added to the water around roots, photosynthesis increases 3–5 times more than when the corresponding amount of CO2 is added to the water surroundings the leaves. As the CO2 content in lakes where Lobelia grows is very limited, Lobelia must absorb CO2 from the sediment, and the carbon dioxide will have to diffuse from the roots up into the leaves through the intercellular system of the plant. In conjunction with Lobelia's CO2 uptake from the sediment O2 is liberated. The plant, therefore, acts as an oxygen pump, which oxidizes the sediment down to a depth of 20 cm.
The Effect of Cyclopropane on Ion Uptake and Protoplasmic Streaming in Barley Roots
Authors: JACOBSON L. , YOUNG L. C. T. 
Published: April 2006

AbstractIncreasing concentrations of cyclopropane up to about 95 % C3H6—5 % O2 caused an increasing inhibition of uptake by excised barley roots from KC1 solution, much more so for Cl than K. No inhibition of K uptake from K2SO4 occurred under similar conditions. It is suggested that the small decrease in K uptake from KC1 is related to the large decrease in Cl uptake and that C3H6 primarily inhibits Cl uptake with little or no effect on K uptake. Time curves of uptake in 80 % C3H6 20 % O2 revealed no indication of cumulative injury in either KC1 or K2SO4 for periods up to 3 hours.The amount of organic acid production associated with K uptake from K2SO4 was about the same in 80 % C3Hg— 20 % O2 as in air. Oxygen consumption in K2SO4 was unaffected by the gas mixture and only slightly affected in KC1.Protoplasmic streaming in epidermal cells was rapidly stopped at C3H6 concentrations of 20 % or higher. In 80 % C3H6–20 % O2 the effect on streaming was confined mostly to the outer two or three layers of root cells. A connection between the cessation of streaming and the inhibition of Cl uptake appeared to exist but very little if any relationship between streaming and K uptake was observed.
Luminescence Induced in Intact Leaves and Isolated Chloroplasts by Alcohols and Other Substances
Authors: BJöRN L. O. , SIGFRIDSSON BJöRN 
Published: April 2006

Abstract Elodea leaves and spinach chloroplasts emit red light when treated with alcohols or certain other solvents for chlorophyll. The intensity of the light, the lag phase and the threshold concentration vary considerably between different alcohols.Light emission from a leaf starts a few seconds to a few minutes after the addition of alcohol to the medium, reaches a maximum after 2–45 minutes (sometimes more) and then continues for many hours. Despite the faintness of the glow, the total number of photons given off from a leaf after addition of alcohol may exceed the number of photons given off from the same sample as long‐lived afterglow after saturating irradiation with far‐red light. The maximum yield of photons per chlorophyll molecule is a little more than 10–5. The alcohol‐induced luminescence is not influenced by a decrease in the oxygen tension to one fifth of the normal.Electron micrographs of treated leaves reveal that the thylakoid lipids contract to drops at the edges of the grana. Treatment of isolated chloroplasts with ethanol results in light emission when the concentration is high enough to dissolve the chlorophyll. It is estimated that the surface free energy in the thylakoid lipid‐aqueous interface, due to ordinary interfacial tension, is large enough to account for the light emission observed when the interfaces contract or disappear.
Effects of Some Chemical Compounds on the Slow, Far‐red Induced Afterglow from Leaves of Elodea and the Lack of Effect of N‐methyl Phena zonium Methosulfate on Far‐red induced Glucose Uptake in Chlorella
Authors: BJöRN L. O. 
Published: April 2006

AbstractN‐methyl phenozonium methosulfate,3–(3,4‐dichlorophe‐nyl)–l, l‐dimethylurea and carbonylcyanide‐m‐chlorophenyl hydrazone have similar effects on the slow, far‐red induced afterglow component in intact Elodea leaves as has previously been shown for Chlorella. The first compound increases the rate constant for emission. Contrary to the case with Chlorella, it also markedly increases the total amount of light emitted from 10 sec. to infinity (maximally by 50 percent). The second compound decreases the rate constant and the amount of light, and the third compound increases the rate constant and decreases the amount of light. Electron micrographs are compared with the hypothetical units that can be deduced from the afterglow experiments, and it is found that the small thylakoids (“grana thylakoids”) have a size of the same order of magnitude as that expected for the afterglow units.The afterglow from Elodea, in contrast to that from Chlorella, is not affected by desaspidin except at extremely high concentrations.Far‐red induced glucose uptake in Chlorella is not affected by 10–7M N‐methyl phenazonium methosulfate, which was previously shown to have a large effect on afterglow kinetics in the same organism.
Stress‐relaxation Properties of the Avena Coleoptile Cell Wall
Authors: YAMAMOTO RYOICHI , MASUDA YOSHIO 
Published: April 2006

AbstractChanges in the cell wall properties of Avena coleoptile segments were studied under various conditions by stress‐relaxation analysis. Rheological models consisting of four or an infinite number of Maxwell viscoelastic components were used. The stress‐relaxation parameters of these models, t1, to, T, Gi and stress/strain ratio, were determined. The following results were obtained.1. The 1/T1 increased and stress/strain ratio decreased with the age of the coleoptiles. Decapitation caused a decrease in l/t1.2. Auxin increased I/T1 but decreased to and stress/strain ratio within 5 minutes after application.3. Treatment with a fungal β‐l,3‐glucanase increased 1/T1 both in living and methanol‐killed, pronase‐treated coleoptiles. Cellulase did not cause the changes observed in the parameters of the isolated cell wall of the coleoptile segments. This held true for all treatments (with and without auxin, killed and pronase‐treated).The results obtained suggest that auxin primarily causes a partial degradation of the non‐cellulosic physaccharide components of the cell wall.
Studies on Ectomycorrhizae of Pine II. Growth Inhibition of Mycorrhizal Fungi by Volatile Organic Constituents of Pinus silvestris (Scots Pine) Roots
Authors: MELIN ELIAS , KRUPA SAGAR 
Published: April 2006

AbstractThe effects of several monoterpenes and the sesquiterpene longifolene on the vegetative growth of two mycorrhizal fungi, Boletus variegatus and Rhizopogon roseolus, were studied in petri plate experiments on an agar medium. The test substances are natural constituents of Pinus silvestris (Scots pine) roots. Vapors from 20 μl of all the test substances, upon a 5 day exposure inhibited the growth of both the mycorrhizal fungi 55% to 86%. The two fungi, however, differed in their tolerance to individual compounds. It is suggested that the terpenes and the sesquiterpenes play an important role in the development of the symbiotic condition in ectomycorrhizae by restricting the growth of the mycorrhizal fungi within the host root.
Apparent Free Space of Germinating Pea Seeds
Authors: MOROHASHI Y. , SHIMOKORIYAMA M. 
Published: April 2006

AbstractThe apparent free space (AFS) of pea seeds was determined by measurement of the exodiffusion of solutes from the seeds previously equilibrated with radioactive solutions. AFS (per cent of volume of water taken up by dry seeds) varied with the kinds of solutes used, that is, values of 27–30% were obtained for mannitol or leucine and 12% for malonate, at pH 6. When the seeds were incubated in a radioactive solution at lower pH (3.5), higher AFS values were obtained, especially for malonate. The AFS of imbibing seeds showed a tendency to increase during the course of imbibition.
The Relationship between Stimulus Intensity and Oriented Phototactic Response (Topotaxis) in Chlamydomonas
Authors: FEINLEIB MARY ELLA HARMAN , CURRY GEORGE M. 
Published: April 2006

AbstractTwo techniques have been used to study the quantitative relationship between stimulus intensity and oriented phototactic response (topotaxis) in Chlamydomonas. The net response of a cell population was monitored photometrically and was recorded continuously against time. The responses of individual cells were observed through a microscope and their swimming tracks were recorded on film.The net response of the population is positive at low stimulus intensity and negative at high intensity. The direction of response can be reversed within two seconds by raising or lowering the intensity. The intensity‐response curve for phototaxis is similar to the dose‐response curve for phototropism. The net response has no distinct threshold; it increases linearly with log intensity; then it decreases and finally becomes negative.The individual‐cell studies reveal that the intensity‐dependent increase in net topotactic response is due primarily to an increase in the number of cells responding and in the directness of their swimming path. As stimulus intensity is raised, the swimming path becomes increasingly well‐aligned with the stimulus beam, whether net response is positive throughout the intensity range tested, negative throughout that range, or changing from positive to negative.Changes in swimming rate do not contribute significantly to the intensity‐dependent changes in net response. Swimming rate shows virtually no change throughout the intensity range of positive topotaxis and shows only a small increase in the negative range. However, a transient decrease in swimming rate (stop response) is often observed at the onset of stimulation. The implications of these results for the orientation mechanism are discussed.
Phytol Changes in Dark Grown Leaves of Barley after Varying Light Treatments
Authors: LILJENBERG CONNY 
Published: April 2006

AbstractGas chromatographic determinations revealed a certain amount of free phytol in dark‐grown barley leaves. When a short light impulse or continuous light is given to the leaves, the phytol pool is partly emptied due to esterification of chlorophyllide a. The regeneration is slow during the first 2–3 hours. A pretreatment with light flashes followed by a dark period accelerates the regeneration, which stops however after approximately 30 min. Some evidence points to the existence of an acceptor for excess phytol entering at this stage.Connections between phytol changes during irradiation and the lag phase of chlorophyll formation are discussed.
Regulators of Cell Division in Plant Tissues XII. A Cytokinin Bioassay Using Excised Radish Cotyledons
Authors: LETHAM D. S. 
Published: April 2006

AbstractA rapid bioassay for cytokinins is described. This is based on the ability of these compounds to promote markedly the expansion of radish cotyledons excised soon after seed germination. The response, which is due largely to a promotion of cell enlargement, is inhibited by abscisic acid. Gibberellins, certain amino acids and calcium salts, naturally occurring substances without cytokinin activity, induce small growth increments in the assay. Cytokinin structure‐activity relationships observed for the assay are very similar to those which apply in the tobacco‐pith tissue culture assay.
Imbibition and Germination: Influence of Hard Seed Coats on RNA Metabolism
Authors: BARTON KENNETH A. , ROE CATHY H. , KHAN ANWAR A. 
Published: April 2006

AbstractRNA metabolism of Indian rice grass seeds was studied in relation to imbibition and germination. These seeds germinate only after scarification of the seed coats. The hard seed coats restrict germination but not water intake or changes in the quantity and quality of RNA formed during early hours of soaking. These changes differ markedly from those in scarified (H2SO4 treated) seeds which are able to germinate. Gibberellic acid hastens germination of scarified seeds and causes changes in the population of RNA transcribed.
Studies on the Physiology of Host‐parasite Relationship in Orobanche. II. Growth and Mineral Nutrition of Host and Parasite
Authors: SINGH JAI N. , SINGH JAGDISH N. , RAI T. B. 
Published: April 2006

AbstractThe effects of Orobanche infection on the growth and mineral compostition of the host were studied. Parallel observations were made in host and parasite.Orobanche infection reduces the height of main shoot, the length of root, the number of branches, and the number and total area leaves per plant. Consequently the fresh and dry weight of the host is also decreased. Infection affects NAR and LAR only slightly but reduces RGR and RLGR at a later period of infection. The retardation in the growth of host seems to be due mainly to a continuous extraction of metabolites and inorganic nutrients. Infection increases the nitrogen, calcium and magnesium content in the host, especially in the leaves. This fact is connected with the retarded growth in the host. The process of absorption is probably not changed. The phosphorus and potassium contents diminish in the infected host, a fact related to the higher translocation to the parasite.The Orobanche plants grow faster during early stages and accumulate 88 % of total dry matter before flowering, The growth stages of Orobanche do not coincide with those of the host suggesting that the parasite is capable of synthesizing its own growth substances. Studies with 32P show that the flow of minerals is mainly in the direction from host to parasite. The major part of the requirement of the parasite is met by the host. Orobanche maintains a higher phosphorus and potassium content in its tissues than the host, while the nitrogen, calcium and magnesium content is lower.
Growth and Organogenesis in Tissue Cultures of Allium cepa var. proliferum
Authors: FRIDBORG GUNNAR 
Published: April 2006

AbstractCallus isolated from aerial bulbs of Allium cepa var. proliferum was grown in agar and liquid cultures on a synthetic medium containing 5 × 10−6M 2,4‐D. Root formation occurred in the absence of 2,4‐D and was highly stimulated by 5 × 10−6M NAA. Cytokinin was not necessary for growth and organ formation but slightly stimulated the formation of leafy buds. Combinations of NAA or IAA and cytokinin stimulated growth and root formation to a greater extent than anyone of these substances added alone. Pieces of callus in liquid culture developed roots in one week in root‐inducing medium, but bud or embryo formation was not observed in liquid cultures.
Iwanoff Effect in Leaves of Cotton (Gossypium hirsutum)
Authors: BRITTAIN E. G. , NAGARAJAH S. 
Published: April 2006

AbstractWhen a leaf is excised from a plant by cutting the petiole in air, the stomata sometimes exhibit an “Iwanoff effect” or temporary increase of aperture before entering the phase of hydroactive closure. Simultaneous and separate measurements of transpiration from upper and lower leaf surfaces, derived from thermocouple psychrometers, photosynthesis measurements from either or both surfaces obtained with an Infrared Gas Analyser and measurements with a nitrous oxide diffusion porometer have been made on leaves of Gossypium hirsutum (cotton) before and after severing the petiole. The effect of previous illumination of the plant on the occurrence of the Iwanoff effect has been studied. The results obtained are consistent with the suggestion that an Iwanoff effect is observed when there is little or no water stress, but fails to appear if water stress has developed, even though it may not yet have reached the level at which hydroactive stomatal closure would occur. Furthermore the Iwanoff effect appears to be limited to the stomata of the upper surface in cotton leaves. This seems to be due to the greater accessibility of the upper than the lower epidermal cells, to the water demand of the internal tissues which follows excision. Evidence is also presented to show that the adaxial stomates do not necessarily close completely in the dark.
Cytokinin Function: Increase in [Methyl−14C] Metabolism to Phosphatidylcholine and a Decrease in Oxidation to Carbon Dioxide−14C
Authors: SCHAEFFER G. W. , SHARPE F. T. 
Published: April 2006

AbstractAxillary buds of Nicotiana tabacum L. cv. Maryland Catterton normally suppressed by apical dominance are released from dormancy with 6‐benzylaminopurine. This work was done to determine the change in the [methyl−14C] metabolism from methionine during bud stimulation with cytokinin. Dormant buds metabolize [methyl−14C] ‐methionine to 14CO2 more effectively than buds released from dormancy. This oxidation of the methyl group is inhibited with benzylaminopurine. On the other hand, the methylation of polar membrane components, including phosphatidylcholine, is enhanced by the cytokinin during the period preceding the increase in bud weight. The interpretation is presented that the enhanced synthesis of membrane components, as well as the preservation of the methyl groups, are mechanisms for the cytokinin release of bud dormancy with 6‐benzylaminopurine.
14C‐Studies on Apple Trees. VII. The Early Seasonal Growth in Leaves, Flowers and Shoots as Dependent upon Current Photosynthates and Existing Reserves
Authors: HANSEN POUL 
Published: April 2006

AbstractThe young leaves' consumption proper of photosynthates and their contribution to the growth of flowers, fruits and shoots by exposing spurs and shoots to 14CO2 at the earliest stages of the growth period in apple trees (Malus X domestica) were studied. By a parallel determination of the growth intensity in various organs an attempt is made to evaluate their relative dependence on current photosynthates and on reserves from inside the tree.The proper fixation of 14C by growth in the exposed leaves is high in the earliest phases of growth. The fixation of 14C is considerable in the flowers, including the petals, immediately prior to flowering, in intensely growing fruits, and in the woody parts of the current year's shoots, when the main part of the terminal growth has been completed. Under conditions of high intensity of growth in an organ, the total fixation by growth in the parts studied may amount to as much as 80–90% of the 14C absorbed.Only in the very earliest phases of development does the growth of flowers and shoots appear to be based to a greater extent on materials supplied from reserves than from current photosynthesis. Quantitatively the greater part by far of the total new growth in fruits and shoots appears to be based on materials from current photosynthesis.
Studies on Auxin Protectors X. Protector Levels and Lignification in Sunflower Crown Gall Tissue
Authors: STONIER TOM , YANG HSIN‐MEI 
Published: April 2006

AbstractThe lignification and differentiation of phloem fibers in sunflower stems is inhibited by growing crown gall tumors. Crown gall tumor tissue has previously been shown to contain large quantities of auxin protectors. Since auxin protectors are antioxidants which inhibit peroxidase‐catalyzed reactions, and since the formation of lignin is known to involve a peroxidase‐catalyzed reaction, an investigation was undertaken to examine the relationship between auxin protectors and lignification in sunflower crown gall tissue.Sunflower crown gall tissue placed into media low in mineral content, rapidly lignifies. In the low mineral media, protectors appear in the medium within an hour or two, implying that endogenously‐synthesized protectors rapidly leak out of the tissue. In control media, the tissue neither lignified appreciably, nor did it exhibit an excessive amount of protector release. The addition of Ca2+ to the low mineral medium markedly slowed, but did not entirely prevent lignification; similarly Ca2+ markedly slowed the release of protector into the low mineral medium. Auxin protectors added to the low mineral medium did not inhibit lignification apparently because, in the medium, the protectors are rapidly oxidized to quinones. The addition of catechol, a substance which mimics protector, also failed to inhibit lignification and also formed a colored compound in the medium suggesting o‐qui none formation. In contrast, dithiothreitol, a strong anti‐oxidant which upon oxidation does not form a strong oxidant (such as o‐quinone), when added to the low mineral medium does inhibit lignification.It is suggested that in the in vitro situation lignification and senescence occurs in low mineral media because the protectors leak out rapidly causing the cell's metabolism to favor peroxidase‐catalyzed oxidations including those leading to lignification, while in the in vivo situation the excess protectors produced by crown gall tumor tissue diffuse into surrounding tissue, maintaining a reduced state in such tissues and thereby inhibiting differentiation and lignification. The synthesis of large quantities of protectors by the tumor tissue therefore could account for the anaplasia of the bundle caps observed in sunflower internodes in the vicinity of growing crown gall tumors.