bluuebunny/crossref_metadata_2025_split huggingface dataset:
The inhibition of exogenous NAD(P)H oxidation in plant mitochondria by chelators and mersalyl as a function of pH
Authors: Möller Ian M. , Palmer John M. 
Published: April 2006

The oxidation of exogenous NADH by Jerusalem artichoke (Helianthus tuberosus L.) tuber mitochondria was strongly inhibited at pH 7.2 by EDTA, EGTA and mersalyl and by chlorotetracycline in the presence of Ca2+. This inhibition disappeared at pH 5.5 where about 50% activity was found as compared to controls at pH 7.2. The rate of oxidation of NADPH at pH 5.5 was the same as for NADH but it was inhibited by 50% by both EDTA and mersalyl.Mitochondria from Arum maculatum spadices oxidised NADH and NADPH with pH optima of 7.2 and 6.5, respectively. In the presence of EDTA the optima shifted to 6.7 and 5.9, respectively, due to an inhibition at higher pH and a lack of inhibition at lower pH. At pH 6.7 NADH oxidation was completely insensitive to both EDTA and mersalyl whereas the oxidation of NADPH was inhibited by more than 50%. The inhibition of NAD(P)H oxidation by chelators at neutral pH was due to the removal of Ca2+ from the membranes in both types of mitochondria. The differences observed in the properties of NADH and NADPH oxidation suggest that two different dehydrogenases are involved. Because of the strong pH‐dependence and the changes in chelator‐sensitivity in the physiological pH‐range 6–8 it is suggested that the properties of NAD(P)H oxidation provide the cell with important means of metabolic regulation.
Role of β‐amylase in starch metabolism during soybean seed development and germination
Authors: Hildebrand D. F. , Hymowitz T. 
Published: April 2006

Differences in starch metabolism during seed development and germination of two soybean [Glycine max (L.) Merrill] genotypes with normal seed β‐amylase activity [‘Williams’ (Sp1b and ‘Altona’ (Sp1b)] and two soybean genotypes with undetectable seed β‐amylase activity [‘Chestnut’ (Sp1au) and ‘Altona’ (Sp1)] were investigated. Starch and soluble sugar profiles were essentially the same during seed development and germination. Total amylase activity of Williams and Altona (Sp1b) peaked just prior to seed maturity and then dropped off slowly; whereas, the total amylase activity of Chestnut and Altona (sp1) was very low throughout seed development and germination. The differences in amylase activity between Altona (Sp 1 b) and Altona (sp 1) was also seen in leaves. α‐Amylase activity was similar in the four genotypes when β‐amylase was inhibited with Hg2+ but was higher in the two genotypes with normal β‐amylase activity when β‐amylase was inhibited with heat plus Ca2+. Low levels of starch phosphorylase activity were detected throughout seed development and germination, and the activity was similar in three of the genotypes and higher in Altona (sp 1).The protein, oil and oligosaccharide contents of mature seeds of the four genotypes were similar. Altona (sp 1 b) and (sp 1), which appear to be near isogenic lines, were not different in any morphological character or yield.Altona (Sp 1 b) showed greater hydrolysis of soybean seed starch than Altona (sp 1), but the evidence indicates that the mutation resulting in greatly reduced or missing β‐amylase activity has no effect on starch metabolism of developing and germinating soybean seeds.
Brassinolide, a growth‐promoting steroidal lactone
Authors: Mandava N. Bhushan , Sasse Jenneth M. , Yopp John H. 
Published: April 2006

Brassinolide (BR), a naturally‐occurring steroidal lactone was compared with GA3 and kinetin for activity in a number of bioassays. BR was highly active in elongation bioassays employing the dwarf pea epicotyl and etiolated bean hypocotyl that are responsive to GA3 but not IAA (at 0.01 to 10 μM). The elongation of the cucumber hypocotyl elicited by BR and GA3 was reduced far more than that elicited by IAA, following removal of the cotyledons. BR, like GA3 also inhibited betacyanin accumulation in Amaranthus seedlings and prevented adventitious root initiation in hypocotyls of mung bean, dwarf bean and cucumber. Application of BR promoted rather than retarded senescence of Rumex leaves.While almost half as effective as kinetin in promoting expansion of cucumber cotyledons, BR was ineffective in cytokinin bioassays involving expansion of dwarf pea epicotyl hooks, dark synthesis of betacyanin in Amaranthus and retardation of Xanthium leaf disc senescence. Unlike the case with IAA, BR does not interact synergistically with GA3. BR has proven active in promoting stem elongation in plant bioassays responsive to either IAA or GA3, or to both phytohormones. This effect, coupled to its effect on adventitious root formation, qualifies BR as a unique plant growth substance.
Interaction of Ancymidol and benzyladenine in control of growth of juvenile Hedera helix
Authors: Clark James R. , Hackett Wesley P. 
Published: April 2006

The growth of the juvenile form of Hedera helix L. was greatly suppressed by soil drench treatment with the growth retardant, Ancymidol. Treated plants were smaller in stature, had fewer nodes and shorter internodes, accumulated less dry weight, had reduced leaf area, and lowered shoot: root ratios than untreated plants. In contrast, shoot tip application of the cytokinin, benzyladenine, increased stem diameter and shoot:root ratio over that of controls.When Ancymidol and benzyladenine were applied together, reductions in plant growth were not evident – plants appeared as the untreated controls. The implications of this interaction are discussed.
Effect of chlorate, nitrogen source, and light on chlorate toxicity and nitrate reductase activity in soybean leaves
Authors: Harper James E. 
Published: April 2006

Growth chamber studies were conducted to assess the relationship between nitrate reductase (NR) activity and development of chlorate (KClO3) toxicity symptoms in leaflets of soybeans [Glycine max (L.) Merr.]. Fourteen day‐old soybean seedlings, grown in NO3 ‐ or urea‐nutrient solutions, were exposed to various KClO3 concentrations (0 to 2.0 mM) and light levels (100, 67, 33 and 0% of full light which was 750 μE m−2s−1) for 24 h. Visual KClO3 toxicity symptoms were noted and NR activity was measured.Toxicity symptoms (interveinal chlorosis) were evident within 24 h following addition of 0.5 mM KClO3 to the nutrient solution, regardless of N nutrition, and symptom severity increased with increased KClO3 concentration (up to 2.0 mM). Leaflet NR activity was lower following 24 h KClO3 treatments at concentrations of 0.5 mM and higher, indicating that ClO3 ‐ or some reduction product of ClO3 ‐ likely ClO2 ‐ was detrimental to enzyme functionality. The light study supported involvement of NR activity in KClO3 toxicity in that comparison of control and KClO3 treated plants exposed to decreased light levels revealed a decrease in NR activity of control plants parallel to a decrease in severity of KClO3 toxicity symptoms of treated plants. Urea‐grown plants, which have an apparent constitutive NR enzyme, were used to verify that the KClO3 toxicity symptoms were not simply N starvation symptoms due to competition of ClO3 ‐ and NO3 ‐ for uptake and reduction. In vivo NR assays also ruled out that ClO3 ‐ was decreasing NR activity through competition with NO3 ‐ for reduction sites. The close relationship between KClO3 toxicity symptoms and NR activity, in response to light treatments, suggested that KClO3 toxicity symptoms were associated with reduction of ClO3 ‐ to ClO2 ‐ by the NR enzyme. However, the possibility that a more direct photochemical reaction occurred in the presence of KClO3 to produce the toxicity symptoms could not be ruled out.
The photostability of different chlorophyll forms in dark grown leaves of wheat
Authors: Axelsson Lennart 
Published: April 2006

Formulae were developed for calculation of the relative amount of different pigment forms of dark grown leaves of wheat, present before and after photoreduction of the protochlorophyllide. Three pigment forms were calculated from in vivo absorption spectra: the photoreducible protochlorophyllide with absorption maximum at 650 nm and the two chlorophyll(ide) forms with absorption maximum at 684 nm and 673 nm, respectively. The formulae were used to study the changes of the pigment forms at repeated photoreduction of the protochlorophyllide, and at a repeated treatment involving photoreduction of the protochlorophyllide followed by partial photo‐decomposition of the chlorophyllide formed.Five consecutive photoreductions and reaccumulations of protochlorophyllide were carried out by high intensity irradiations of one second (red light, 700 W m‐2) given at intervals of 3 h. The results show that the pool size of reaccumulated protochlorophyllide decreased sharply with the number of photoreductions performed. The absorption spectrum of the chlorophyllide formed at each photoreduction proceeded through the Shibata shift (transformation of the 684‐form to the 673‐form) and the late red‐shift (transformation of the 673‐form to other pigment form(s) in the dark).High intensity irradiation for ten minutes (red light, 700 W m‐2) immediately after each phototransformation caused a photodecomposition of about three quarters of the newly formed chlorophyllide (which was in the 684‐form) while the earlier formed chlorophyll(ide) (in the 673‐form) appeared not to be decomposed. This partial photodecomposition of the chlorophyllide had no effect on further accumulation of protochlorophyllide in the dark, and the absorption spectrum of the remaining chlorophyllide proceeded through the Shibata shift. The partial photodecomposition caused an inhibition of the late red‐shift, and the accumulated chlorophyll(ide) remained in the 673‐form.
Mass propagation of globe artichoke (Cynara scolymus): Evaluation of different hypotheses to overcome vitrification with special reference to water potential
Authors: Debergh P. , Harbaoui Y. , Lemeur R. 
Published: April 2006

In search of a technique for rapid clonal propagation and sanitation of Cynara scolymus L. we have been confronted with the problem of vitrification.We only succeeded in overcoming this problem by raising the agar concentration of our medium to 1.1% instead of 0.6%. By using the Chardakov‐method and direct measurement of the water potential with a thermocouple psychrometer we were able to prove that this result was attributable to the matric potential.
Characterization of glutamine synthetase in the apple
Authors: Kang Seong‐Mo , Titus John S. 
Published: April 2006

Glutamine synthetase (l‐glutamate: ammonia ligase, ADP‐forming, EC 6.3.1.2) in bark tissue of the apple (Malus domestica Borkh. cv. Golden Delicious) was partially purified and characterized. The Mn2+‐ and Mg2+‐dependent activities were maximal at pH 7.2 and 7.5, respectively. The enzyme was almost completely inactivated within two weeks at 0°C. Both Mg2+ and β‐mercaptoethanol were effective in stabilizing the enzyme during storage. The enzyme was protected from thermal inactivation at 60°C by the addition of Mg2+ and ATP. One‐tenth mM phenylmercuric acetate inhibited the Mg2+‐dependent activity by 50%. Equimolar dithiothreitol protected the enzyme from this inactivation. The Km values of the enzyme were 0.27, 7.35, and 0.69 mM for ATP, glutamate, and NH2OH, respectively. The constant for NH+4 was an order of magnitude higher in the presence of Mn2+ than Mg2+.When the amino acids were externally added to the reaction mixtures, the measurement of Pi exhibited a higher degree of enzyme inhibition than the measurement of γ‐glutamyl monohydroxamate (GHA). Ten mM histidine inhibited the Mg2+‐ and Mn2+‐dependent activities by 26 and 45% respectively. Twenty mM aspartate (d,l‐form) inhibited the enzyme 30% in the presence of either Mg2+ or Mn2+. Aspartate (Mg2+‐dependent) and histidine (Mn2+‐dependent) inhibited the enzyme competitively with respect to glutamate, the estimated inhibition constants being 17.6 and 1.6 mM, respectively. At 10 mM, amino acids such as tryptophan, arginine, alanine and citrulline inhibited enzyme activity from 1 to 18%. Glutamine stimulated the Mg2+‐dependent activity 25% at 25 mM when GHA was measured. Glutamine above 32 mM inhibited the enzyme.
Heterotrophic tobacco cell cultures during greening
Authors: Nato A. , Mathieu Y. , Brangeon J. 
Published: April 2006

Nicotiana tabacum L. (cv. Xanthi) suspension cultures initially grown in the dark and then exposed to continuous light followed a developmental pattern divided into a lag phase (T0–T2), a growth phase (T3–T9) and a stationary phase (T10–T21). The onset of chloroplast differentiation during the active cell division phase was associated with a rapid chlorophyll synthesis, a high rate of respiratory activity (400 μmol h−1 g−1 dry weight) and a four‐fold increase in soluble protein content compared to that of the initial inoculum. Oxygen evolution was nil until T3. It increased regularly up to a value of 30 μmol h−1 g−1 dry weight at the beginning of the stationary phase, higher values (80 μmol) being reached later in this phase. An inverse relationship between phosphoenolpyruvate carboxylase (PEPCase) and ribulose 1,5‐biphosphate carboxylase (RUBPCase) was shown during cell growth. The PEP‐Case capacity expressed on a soluble protein basis rose from an initial day 0 value of 3.5 μmol to a maximum of 7.0 μmol at T5 and then returned to the initial value during the post‐exponential and stationary phases. In contrast, RUBPCase activity was minimal (0.1 μmol) from T0 to T3 of greening, increasing to a maximum (1.7 to 2.0 μmol) at T8. The 20 fold stimulation of this enzyme capacity was related to a de novo protein synthesis.Immunodiffusion tests revealed the presence of RUBPCase molecules in soluble crude extract of dark‐grown cells. The SDS‐get densitometric profile of soluble protein extract from dark‐grown cells was qualitatively similar to that obtained with crude extract of green cells. The 56,000 Da polypeptide co‐migrating with the large subunit (LSU) of RUBPCase appeared reduced in dark‐grown cells compared to the peak height of the same polypeptide present in green cells. In both preparations, the 13,000 Da polypeptide co‐migrating with the small subunit (SSU) was equally present. The current hypothesis is that the synthesis of RUBPCase at the time of greening would concern the preferential synthesis of the LSU of the enzyme.
Basic properties of the circadian leaf movements of Oxalis regnellii, and period change due to lithium ions
Authors: Johnsson A. , Johnsen P. I. , Rinnan T. , Skrove D. 
Published: April 2006

The circadian leaf movement of Oxalis regnellii Mig, has been investigated. The three leaflets of a stalk were normally synchronized, and under the experimental conditions chosen they showed a period of 26.2 ± 0.1 h. Cutting off one or two leaflets led to a successive decrease of the period length (25.7 ± 0.1 and 25.1 ± 0.3 h resp.). It was possible to phase shift the leaf movements by mechanical means (advance of 1.6 ± 0.3 h).Lithium ions, added permanently to the transpiration stream, increased the period length of the leaf movements by more than one hour (with 10 mM Li+). A 24 h pulse of 20 mM LiCl caused a permanent 2–3 h phase delay of the circadian rhythm. Four‐h pulses, on the other hand, provoked only transient phase delays, the magnitude being dependent on the phase of application. Lithium concentrations were determined for different regions of leaves and pulvini. It was shown that leaf segments had considerably lower concentrations than pulvini. No significant difference in the lithium concentration was observed between the upper and lower part of pulvini.In the light leaf position was strongly correlated with water uptake and the consequences for applications of substances to the circadian system via the transpiration stream is discussed. A simple model of the oscillatory system and reactions connected to it is discussed.
Sterol content, fatty acid composition of phospholipids, and permeability of labeled ethylene glycols in relation to salt‐tolerance of yeasts
Authors: Adler Lennart , Liljenberg Conny 
Published: April 2006

Two yeasts, the salt‐tolerant Debaryomyces hansenii and the non‐tolerant Saccharomyces cerevisiae were grown in basal media (4 mM NaCl) and also a high salinities that produced a similar salt stress in the two species in terms of growth rate reduction (i.e., 1.4 M NaCl for S. cerevisae and 2.7 M NaCl for D. hansenii). A study was made of the sterol content, the fatty acid composition of the phospholipids, and the permeation of a series of tritiated ethylene glycols of graded molecular weights. On the basis of cell dry weight the amount of total and free sterols increased in both species when cultured at high salinity. Irrespective of growth medium salinity, the molar ratio of free sterols to phospholipids was higher in D. hansenii than in S. cerevisiae. Increased salinity produced only minor changes in the fatty acid composition of the phospholipids in D. hansenii, whereas in S. cerevisiae there was a marked decrease of linolenic acid with a concomitant increase of linoleic acid.In both yeasts there was an energy linked component in the uptake of ethylene glycol, which component could be inhibited by sodium azide and N‐ethylmaleimide. The passive permeability for ethylene‐, diethylene‐ and triethylene glycol increased for both species at increased salinity. This increase was more pronounced for S. cerevisiae than for D. hansenii. Polyethylene glycol of M, 200 as well as higher polyethylene glycols appeared to be excluded or very slowly admitted by the yeasts.
Effet du refroidissement local de la tige sur le transport du AIA exogène en provenance du bourgeon apical et sur la croissance des bourgeons axillaires
Authors: Everat‐Bourbouloux Andrée 
Published: April 2006

Effect of local cooling of the stem on exogenous 1AA transport from the apical bud and on the growth rate of axillary buds.Local cooling (1.5°C) of the stem (on 2 or 4 cm) of Vicia faba L. cv. Aguadulce for 15 h stops the exogenous IAA transport from the apical bud and causes a high accumulation of tracers above and at the level of the cooled zone. This clamping effect is reversed after removal of the cooling system. If the cooling system is maintained for 48 h, about 25% of the exported radioactivity passes the cooled zone. However, the percentage IAA transmitted decreases to about 6.6% if the cooled zone is sufficiently wide (4 cm) and the temperature lowered to 0.7°C±0.3°C. Using a cooling system of 4 cm (0.7±0.3°C) partially releases the lowermost axillary buds (ax1 and ax2) from apical dominance. Yet, the rate of growth of the axillary buds is generally lower than the growth rate after decapitation of the plant.
Light dependency of the cytokinin‐induced bud initiation in protonemata of the moss Funaria hygrometrica
Authors: Simon Patrice E. , Naef Jaques B. 
Published: April 2006

Protonemata of the moss Funaria hygrometrica (Hedw.) are grown in large amounts in a liquid culture system, allowing repetitive dry weight measurements for growth control. Ten‐day‐old protonemata are submitted to various light conditions, in the presence of a cytokinin (iP), which is known for its activity in bud initiation in the moss protonema. The hormone has no influence on the growth rate. Growth and budding are shown to be tightly related. Light is necessary for the initiation of buds but not for their development (to some extent). Identical protonematal growth can be obtained in white, Ted or blue light, but not budding, which is reduced in red or blue light. The early morphological changes in red light, known as nutations, and the presumed inhibitor in blue light could be responsible for the reduced budding. Bud initiation in the dark on an organic medium is greatly enhanced if red light pulses are given at regular intervals. When the latter are followed immediately by far‐red light pulses, the stimulating effect is partly suppressed, suggesting a phytochrome‐controlled process.Experiments with DCMU showed a peculiar effect of this herbicide, which inhibited the use of exogenous sugar in the light but not in the dark.
Electric field‐induced fusion of isolated vacuoles and protoplasts of different developmental and metabolic provenience
Authors: Vienken J. , Ganser R. , Hampp R. , Zimmermann U. 
Published: April 2006

Using an electric field pulse technique, we induced fusion between vacuoles and protoplasts of Kalanchoë daigremontiana, between protoplasts from etiolated and green leaf mesophyll, and between mesophyll protoplasts from plants of different physiological properties (Avena sativa: C3 mechanism of photosynthesis, Kalanchoë daigremontiana: crassulacean acid metabolism). Close membrane contact amongst protoplasts or between protoplasts and vacuoles (as required for fusion) was achieved by the application of an alternating, non‐uniform electric field to the suspension. Due to the dielectrophoresis effect the cells attach to each other along the field lines. The fusion process is initiated by the injection of an electric field pulse of high intensity and short duration (μs range). The field intensity has to be sufficiently high to induce reversible breakdown in the area of close membrane contact. After the application of the field pulse, the fusion process is initiated and completed within seconds to a few minutes, depending on the material investigated.Fusion occurs between protoplasts and vacuoles as well as between protoplasts of different species. Both tonoplast and plasma membranes completely intermingled, indicating that in contrast to suggestions in the literature these membranes are compatible. Furthermore the cytoplasms of etiolated and green protoplasts obviously do not mix after fusion is completed, as etioplasts and chloroplasts kept separated from each other. In all experiments the volume of the fusion product equalled the sum of the compartments that underwent fusion. The wide spectrum of possible applications resulting from these fusion experiments in relation to metabolic problems is discussed.
Reversal of the inhibitory action of abscisic acid by benzyladenine in excised watermelon cotyledons
Authors: Longo Giovanna P. , Stopelli Bruna , Rossi Gianfranca , Longo Claudio P. 
Published: April 2006

Cotyledons of watermelon (Citrullus vulgaris Schrad. cv. Fairfax) were excised from the embryo after 24 h of imbibition and cultured for several days on filter paper with water or abscisic acid (ABA) solution. In some experiments the cotyledons were pretreated with benzyladenine (BA) for times ranging from 5 min to 2 h before transfer to ABA.A treatment with 10−5M ABA blocked all developmental parameters examined (growth and increase in appropriate markers for glyoxysome, peroxisome and plastid development). This blocking can be prevented by an initial treatment with 10−4M BA for 2 h. This pretreatment with BA overrides the action of ABA: the final developmental responses are not just restored to the level of the water control, but they are almost as high as those obtained by treating the cotyledons with BA only. If BA is administered for three days together with ABA the reversal of inhibition is much less efficient.