bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apical control of lateral bud development and shoot growth in mulberry (Morus alba)
Authors: Suzuki Takeo 
Published: May 2006

Measurements of changes in the degree of dominance by upper laterals over lower ones in coppice shoots (1‐year‐old stems) of 12‐year old low‐ pruned stumps of mulberry (Morus alba L. cv. Shin‐ichinose) were made by removal of upper stem sections (pruning) or of lateral buds (debudding.) before spring bud burst, as part of a study of the factors involved in dominance relationships between the developing buds and elongating shoots. Besides inhibition of lower laterals by the upper, leading shoots, there was evidence for mutual inhibition (competition) of neighboring laterals along the stem. Thus in stems in which every other bud, or 4 out of every 5 buds were removed, there was a delay in growth cessation of lower laterals and their greater elongation than in controls. Such competition was seen to exist even between the uppermost and sub‐terminal laterals, since the former elongated more in the absence of the latter.In contrast to high and middle pruned stems, the delay in sprouting of the buds in low‐pruned stems resulted in limited elongation of the shoots from such buds. This inhibition was removed when all the stems on a stump were pruned to the same length, suggesting that it was associated with intact stems with actively growing laterals. Patterns of regrowth of the short shoots (lower laterals) after summer pruning (middle‐pruned) depended on the extent of removal of other stems with vigorously growing, upper laterals. These results demonstrate that both acropetal and basipetal influences are important in bud and shoot dominance relationships.
Changes in osmotic pressure and cell wall properties during auxin‐ and ethylene‐induced growth of intact coleoptiles of rice
Authors: Hoson Takayuki , Maeda Sumiko , Sakaguchi Keiko , Onishi Iliroko , Ohta Hisashi 
Published: May 2006

Indole‐3‐acetic acid and 1‐aminocyclopropane‐1‐carboxylic acid, the precursor of ethylene, stimulated elongation of coleoptiles of seedlings of intact rice (Oryza sativa L. cv. Sasanishiki) submerged in buffer solution with constant air‐bubbling. The osmotic pressure of the cell sap decreased during elongation of coleoptiles. In the presence of 30 μM aminooxyacetic acid, an inhibitor of ethylene biosynthesis, in‐dole‐3‐acetic acid at 30 μM accelerated the decrease in the osmotic pressure in the early stage of growth. 1‐Aminocyclopropane‐1‐carboxylic acid at 30 μM did not influence the decrease in the osmotic pressure.Both indole‐3‐acetic acid and 1‐aminocyclopropane‐1‐carboxyIic acid decreased the minimum stress‐relaxation time and the relaxation rate of the cell wall, suggesting that both auxin and ethylene induce elongation of rice coleoptiles by stimulating cell wall loosening. These growth regulators caused an increase in the level of glucose in hemicelluloses in the early stage of growth and a decrease in the level in the subsequent last growth phase. Indole‐3‐acetic acid decreased the hydroxyproline and glucosamine levels per unit dry weight of the cell wall. These changes in the level of cell wall components may be associated with the changes in the mechanical properties of the cell walls caused by auxin and ethylene.
Aluminium interactions with K+(86Rb+) and 45Ca2+ fluxes in three cultivars of sugar beet (Beta vulgaris)
Authors: Lindberg Sylvia 
Published: May 2006

Three cultivars of sugar beet (Beta vulgaris L.), which are sensitive to aluminium (Al) in the order Primahill > Monohill > Regina, were grown in water culture for 2 weeks. Nutrients were supplied at 15% increase of amounts daily, corresponding to the nutrient demand for maximal growth. The 2.4‐dinitrophenol (DNP)‐sensitive (metabolic) and DNP‐insensitive (non‐metabolic) uptake of aluminium, phosphate. 45Ca2+ and K+(86Rb+) in roots were measured as well as transport to shoots of intact plants. All 3 cultivars absorbed more aluminium if DNP was present during the aluminium treatment than in its absence. It is suggested that sugar beets are able to extrude aluminium activity or that they possess an active mechanism to keep Al outside the cell.The presence of Al in the medium during the 1‐h experiment affected the metabolic and non‐metabolic fluxes of 45Ca2+ and K+(86Rb+) in different ways. In the presence of DNP, the influx of both 45Ca2+ and K+(86Rb+) and the efflux of 45Ca2+ were inhibited by Al in a competitive way. At inhibition of 45Ca2+ influx, 2 Al ions are probably bound per Ca2+ uptake site in cv. Regina (Al‐tolerant), but in cvs Primahill and Monohill only one Al ion is bound (more Al sensitive). Aluminium competitively inhibited the active efflux of 45Ca2+ (absence of DNP) in almost the same way in the 3 cultivars. In contrast, aluminium stimulated the influx of K+(86Rb+) in cvs Primahill, Monohill and Regina in the absence of DNP. Thus, the Al effects on active and passive K+(86Rb+) influx are different. The total influx of K+(86Rb+) increased in the presence of Al and might be connected to an active exclusion of Al. Regina is the least Al‐sensitive cultivar, probably because Al interferes less with the Ca2+ fluxes and because this cultivar actively excludes phosphate in the presence of Al. Thus Al‐phosphate precipitation within the plant could be avoided.
Characterization of a Ca2+‐translocating ATPase from corn root microsomes
Authors: Brauer D. , Schubert C. , Tsu S.–I. 
Published: May 2006

Brauer, D., Schubert C. and Tu, S,‐I. 1990. Characterization of a Ca2+‐translocating ATPase from corn root microsomes. ‐ Physiol. Plant. 78: 335‐344.The existence of a Ca2+‐translocating ATPase in microsomes from maize (Zea mays L. cv, WF9 × Mo17) roots was evaluated using assays to follow Ca2+‐stimulation of ATP hydrolysis and Ca2+ transport by changes in the fluorescence of chlorotetracycline, ATP hydrolysis by microsomes was stimulated by the addition of Ca2+ and further enhanced by the Ca ionophore A23187 and bovine brain calmodulin only in the presence of Ca2+, Stimulation by these agents was additive and sensitive to vanadate. These results were consistent with the presence of a Ca2+‐translocating ATPase in microsomal membranes. The fluorescence of chlorotetracycline in the presence of microsomes and Ca2+ increased upon the addition of ATP, indicating the transport of Ca2+, The initial rate and extent of change in fluorescence were stimulated by calmodulin and quenched by the addition of either A23187 or EGTA, but not by protonophores. Changes in chlorotetracycline fluorescence were prevented by vanadate. Therefore, results using chlorotetracycline also indicated the presence of a Ca2+‐translocating ATPase, Localization experiments indicated that the majority of the Ca2+‐translocating ATPase was on the endoplasmic reticulum.
Large‐scale purification procedure of spinach leaf mitochondria —isolation and immunological studies of the F1–ATPase
Authors: Hamasur Beston , Birgersson Ulf , Eriksson AnnaCarin , Glaser Elzbieta 
Published: May 2006

A large–scale purification procedure for mitochondria from spinach (Spinacia oteracea L, cv Medania) leaves is described. It involves differential centrifugation and density gradient centrifugation on a self–generating gradient of Percoll, From 3 kg of spinach leaves, 150 mg mitochondrial protein are obtained. The thylakoid contamination is lower than 0.2% on a chlorophyll basis. The mitochondria oxidize malate and glycine with state 3 rates of 108 and 140 nmol (mg protein)‐1 min‐1, with respiratory control ratios of 2,7 and 3,8 and ADP/O ratios of 2,0 and 2.1, respectively. The present large–scale purification procedure will facilitate further biochemical and molecular biological studies of leaf mitochondrial proteins.A pure and active catalytic moiety of the F1–ATPase (EC 3,6,1,3) was purified from the isolated mitochondria. The yield was 5 mg of F1–ATPase from 150 mg mitochondria. The F1–ATPase contained five polypeptides of apparent molecular mass 54 kDa (α), 52 kDa (β), 33 kDa (γ), 22 kDa (ω) and 11 kDa (ɛ). An additional component at 24 kDa was present in variable amounts in some preparations and was therefore not ascribed to the ATPase complex. The enzyme catalyzed ATP hydrolysis at a rate of 12.5 nmol (mg protein)‐1 min‐1. Antibodies against the spinach mitochondrial F1–ATPase cross–reacted only with the a and β subunits of F1–ATPases of spinach chloroplasts, photosynthetic bacteria Rhodospirillum rubrum and beef heart mitochondria.
Measurements of pH in the apoplast of sunflower leaves by means of fluorescence
Authors: Hoffmann Bernd , Flänker Rüdiger , Mengel Konad 
Published: May 2006

A method was elaborated by which the pH in leaf apoplast can be measured. The technique is based on the pH dependent fluorescence of 5‐carboxyfluorescein (5‐CF) or fluorescein isothiocyanate (FITC). The fluorescein isothiocyanate is coupled with a macromolecular dextran molecule (FITC‐dextran). For eliminating the effect of the absolute dye concentration the dual excitation technique was applied. It was shown that the ratio of fluorescence excited by light of 491 nm and 463 nm was virtually independent of the concentration of 5‐CF and that this fluorescence ratio was related to the pH. The plasmalemma is practically impermeable to FITC‐dextran and in the test we carried out over a period of 6 h not the slightest indication was found that it may penetrate the plasma membrane. For 5‐CF this cannot be ruled out completely. It is possible that at pH values below 4.5 it may penetrate biological membranes at low rates.Experiments with leaves of sunflower (Helianthus animuscv. Erika) perfused with 5‐carboxyfluorescein and supplied with different nitrogen forms showed that NH+4application resulted in a decrease and NO+3application in an increase of the leaf apoplast pH. Leaf spraying with fasicoccin was followed by a pH decrease, while leaf spraying with the protonophoresp‐trifluoromethoxy carbonytcyanide phenylhydra‐zon (FCCP) or nigericin resulted in neutral apoplastic pH. These results provide evidence that the method is well suited for measuring the response of the leaf apoplast pH to changing physiological conditions.
An excision and squash technique for analysis of the cell cycle in the root quiescent centre of maize
Authors: Múller Mathias L. , Pilet Paul‐Emile , Barlow Peter W. 
Published: May 2006

The quiescent centre of primary roots of Zea mays L. (cvs LG 11 and Golden Bantam) consists of a population of slowly cycling diploid cells. These metabolically inactive cells may be triggered to synthesise DNA under specific conditions and constitute a good model for studying the regulation of the cell cycle. An excision and squash technique is described for the quiescent centre which, when coupled with Feulgen and fluorochrome staining, allows nuclear DNA contents to be determined by microdensitometry in less than a day. This technique was coupled with experiments in which excised quiescent centres were placed on solid culture medium into which hormones and radioactive DNA precursors were incorporated. In complementary and control experiments [methyl‐3H]thymidine was supplied to intact roots (with or without root caps) by means of fibre‐glass cubes as donors.Progression of the cell cycle was followed by microdensitometry and autoradiography. Distribution of DNA content was similar in excised and squashed quiescent centres and in histological sections. Labelling experiments showed that the quiescent centre is made up of cells that differ in their cycle time. While some labelled cells had reached mitosis after 8 h, others were still in G2 after 16 h of continuous labelling. Excision and culture of the quiescent centre resulted in a dramatic activation of the cell cycle as shown by the labelling index that increased from 15% in intact roots fed during 16 h with [methyl‐3H]thymidine to 31% in excised quiescent centres to which radioactive precursor was supplied during the same time. Supplying hormones (50 μM abscisic acid [ABA], 0. 1 μM zeatin, 1 μM zeatin riboside) to quiescent centres via the culture medium restored their inactivity (labelling indices dropped to 1% after ABA. and to 11% after zeatin and zeatin riboside treatments. respectively).
Nitrogen assimilation and transport in carob plants
Authors: Cruz C. , Lips S. H. , Martins‐Louçαo M. A. 
Published: May 2006

Most of the nitrate reductase activity (80%;) in carob (Ceratonia siliqua L. cv. Mulata) is localised in the roots. The nitrate concentration in the leaves is relatively low compared to that in the roots, suggesting that nitrate influx into the leaf may be a major factor limiting the levels of nitrate reductase in the shoot. Transport of nitrate from root to shoot appears limited by the entrance of nitrate into the xylem. In order to study this problem, we determined the nitrate concentrations and nitrate reductase activities along the roots of nitrate‐grown plants, as well as the composition of the xylem sap and the nitrate levels in the leaves. Some of the the bypocotyl, in order to bypass the loading of nitrate into the xylem of the roots. The results show that the loading of nitrate into the xylem is a limiting step.The cation and anion concentrations of nitrate‐ and ammonium‐fed plants were similar, showing almost no production of organic anions. In both nitrate‐ and ammonium‐fed plants, the transport of nitrogen from root to shoot was in the form of organic nitrogen compounds. The nitrate reductase activity in the roots was more than sufficient to explain all the efflux of OH− into the root medium of nitrate‐fed plants. In carob plants the K‐shuttle may thus be operative to a limited extent only, corresponding to between 11 and 27%; of the nitrate taken up. Potassium seems to be the cation accompanying stored nitrate in the roots of carob seedlings, since they accumulate nearly stoichiometric amounts of K+ and NO−3.
Effect of inhibitors on ammonium assimilation in Chlorella sorokiniana in light and darkness
Authors: Rigano Carmelo , Rigano Vittoria Di Martino , Vona Vincenza , Esposito Sergio , Martino Catello Di 
Published: May 2006

In N‐sufficient cells of Chlorella sorokiniana Shihira and Krauss strain 211/8K (CCAP of Cambridge University), assimilation of ammonium was strictly dependent on light and CO2, and was severely inhibited by 100 μM atrazine or 10 μM 3‐(3,4‐dichlorophenyl)‐1, l‐dimethylurea (DCMU). In N‐limited cells, assimilation of NH4+ took place at similar rates in both light and darkness, which were 1.6‐fold higher than the rate of light‐dependent assimilation by N‐sufficient cells. Assimilation by N‐limited cells was inhibited by l‐methionine‐dl‐sulfoximine (MSX), but not by atrazine or DCMU.The rate of photosynthetic O2 evolution was 2.9±0.9 mmol ml−1 packed cell volume (PCV) h−1 in N‐sufficient cells, and 0.64±0.12 mmol ml−1 PCV h−1 in N‐limited cells. In the latter resupply of ammonium resulted in a rapid activation by 22%;, followed by a time‐dependent increase of the photosynthetic O2 evolution, which after 12 h reached the same rate as in N‐sufficient cells.Respiratory consumption of oxygen in darkness in N‐sufficient and N‐limited cells was 0.10±0.03 and 0.11±0.02 mmol ml−1 PCV h−1, respectively. Addition of ammonium was without effect on respiration of N‐sufficient cells, but resulted in a 4‐fold stimulation of respiration of N‐limited cells. Such stimulation took place also in cells treated with DCMU, atrazine, or MSX, and it was also promoted by methylammonium. The stimulation of respiration lasted for several hours.
Seed and fruit abortion as a process of self organization among developing sinks
Authors: Ganeshaiah K. N. , Uma Shaanker R. 
Published: May 2006

Fruit and seed abortion in plants have been traditionally attributed to limiting factors such as resources or to chemically mediated dominance hierarchy among the developing sinks. These hypotheses however do not satisfactorily explain the observed patterns of seed and fruit abortion and have also not withstood the test of critical experimentation. In this paper, we propose an alternative model based on the process of self organization used in physics to explain the flow of liquids etc. As proposed here, the model assumes one simple rule, that the probability of any given sink getting a resource molecule is a function of (a) the sink‐drawing ability of each unit of the tissue and (b) the amount of resource molecules already moved to that sink. Accordingly, any resource molecule moving to a sink, autocatalytically increases the probability of the latter getting further resources.We show that starting from a set of identical sinks, all with equal sink‐drawing ability, the differential development of sinks and thence their abortion might occur purely as a consequence of the autocatalytic or feedback movement of the resource molecules to the developing sinks. We also show that, such a process can lead to abortion even under resource‐abundant conditions, though resource limitation aggravates the extent of abortion. Further, the extent of abortion is shown to be highly dependent on the sink‐drawing ability of the species. We offer the test of this prediction in two ways: (a) in Derris indica the extent of abortion increases with the sink drawing ability of the fertilized ovules and (b) treatments involving growth regulators that increase the sink‐drawing ability result in increased abortion of seeds and fruits. Based on these, we argue that self organization could be the basic process regulating resource flow to sinks and factors such as resource limitation and chemical inhibition might be additionally aggravating the asymmetry among the developing sinks.
Isolation of the rotenone‐sensitive NADH‐ubiquinone reductase (complex I) from red beet mitochondria
Authors: Rasmusson Allan G. , Mendel‐Hartvig Janet , Møller Jan M. , Wiskich Joseph T. 
Published: May 2006

Complex 1 of the respirator) chain (EC 1.6.531, measured as NADH‐duroquinone and NADH‐ubiquinone, reductase activities, was isolated from purified red beetroot (Beta vulgaris L.I mitochondria. The mitochondria were disrupted by freeze‐thawing and inner membrane vesicles were pelleted. After solubilization of the vesicles with Triton X‐100, the enzyme complex was purified 11‐fold (compared to the activity in the inner membrane vesicles) by size‐exclusion chromatography on a Sephacryl S‐400 HR column and then by ion‐exchange chromatography on a DEAE‐Sepharose CL‐6B column. Triton X‐100 was present throughout the purification procedure. Tire purified complex showed approximately 30 bands on SDS‐PAGE and about 15 polypeptides including those at 80. 54, 53. 51. 27. 25 and 22 kDa cross‐reacted with polyclonal antibodies raised against complex I from Neurospora crassa. This is similar lo the pattern obtained with complex I from Neurospera crassa.Analysis by nativc‐SDS 2‐dimensional PAGE revealed the existence of several molecular mass forms of the purified complex.After reconstitution of the purified complex into phosphatidylcholine vesicles, the NADH‐ubiquinone reductase activity had a Km (NADH) of about I μM and was inhibited by both rotenone and dicyclohexylcarbodiimide.
Oscillatory growth movements of roots in weightlessness
Authors: Antonsen F. , Johnsson A. , Perbal G. , Driss‐Ecole D. 
Published: May 2006

The gravitropic curvature of lentil roots (Lens culinarisL. cv. Verte du Puy), grown in near weightlessness and stimulated on a 1‐g centrifuge for 5 to 60 min was followed by time lapse photography. The experiment was carried out in the frame of the IML 1 Mission of Spacelab. Due to the applied acceleration field, the tip of the roots bent and reoriented with respect to the acceleration vector. However, visual inspection of the data could indicate an oscillatory movement superimposed on the gravitropic reorientation.We applied two signal processing techniques, fast Fourier transform (FFT) and maximum entropy spectral analysis (MESA), to provide quantitative data about the oscillatory movements of the lentil roots under gravity free conditions. In the case with very few data points in the time series the MESA method is superior to the conventional FFT. In the lentil root movements, the Fourier analysis could not extract and resolve the oscillatory signals present in the time series. The MESA approach revealed oscillations with periods around 35 and 50 min for the present lentil roots.Circumnutations are, therefore, present in roots also in weightlessness.
Mechanisms of potassium absorption by higher plant roots
Authors: Maathuis Frans J. M. , Sanders Dale 
Published: May 2006

Potassium, as a plant macronutrient, is accumulated in plant cells from relatively dilute soil solutions and is indispensable for many vital processes. Studies characterising potassium uptake by roots stretch back over many decades. However, it is only with the introduction of modern electrophysiological and molecular techniques that investigations have been possible at a molecular level. Such approaches have confirmed the existence of discrete high and low affinity uptake systems at the root plasma membrane and have greatly enhanced our understanding of the underlying molecular nature of these uptake systems.High affinity K+ uptake from micromolar external K+ levels is coupled to H+ transport as demonstrated independently by patch clamping of single root protoplasts and by studying the transport system after expression in Xenopus oocytes. The measured coupling ratio between the two ions is 1:1 and is sufficient to account for an accumulation ratio in excess of 106, a value which encompasses experimental observations on K+ accumulation.Low affinity K+ uptake activates at relatively high external K+ levels in the millimolar range and is ‘passive’ i.e. down the electrochemical gradient for potassium. In two higher plant species single cell inward potassium currents have been identified which are associated with low affinity potassium uptake. Furthermore, specific ion channels which underlie these potassium influxes and form a major constituent of the low affinity potassium uptake pathway have been identified and characterised.
Growth, membrane potential and endogenous ion currents of willow (Salix viminalis) roots are all affected by abscisic acid and spermine
Authors: Fromm Jörg , Meyer Andreas J. , Weisenseel Manfred H. 
Published: May 2006

Growth measurements of hormone‐treated roots from willow cuttings were combined with electrophysiological recordings to study hormone‐induced changes in membrane potential and in endogenous ion currents. The mean growth rate of roots was 10 ± 2 μm min−1 in regular nutrient solution. It increased to 13 ± 2 μm min+1 after application of spermine and decreased to 0.07 ± 0.01 μm min−1 after treatment with abscisic acid (ABA). Transient depolarizations were elicited in root cortex cells by spermine, while ABA caused a transient hyperpolarization. All changes in membrane potential were accompanied by transient responses of the endogenous current. These responses suggest that first anions, then cations leave the root during spermine‐induced depolarizations. From the changes of the endogenous current an apparent efflux of anions (presumably Cl−) and cations (presumably K+) of 200 to 700 pmol cm−2 per depolarization was calculated.To further investigate a possible relation between endogenous ion currents, growth and the growth regulators ABA and spermine, long‐lasting extracellular vibrating‐probe measurements were performed. Control roots showed an inward current of about 1.5 μA cm−2 at the apical elongation zone and an outward current with a maximum density of 1.3 μA cm−2 at the central and basal elongation zone. The addition of ABA and spermine (final concentration 0.1 mM) to the bathing medium affected the endogenous current in opposite ways: ABA caused a reduction of inward and outward current, while spermine stimulated both. Since protons are a major component of the endogenous current, and sucrose can be taken up by root cells from the apoplast via symport with H+, a role of the endogenous current in growth regulation is indicated.