bluuebunny/crossref_metadata_2025 huggingface dataset:
Establishment and growth characterization of suspension culture of cells from the moss, Sphagnum imbrication
Authors: Kajita Miyuki , Takio Susumu , Takami Shinji , Hino Seiichi
Published: May 2006

A green‐pigmented callus of the moss, Sphagnum imbricatum Hornsch. ex. Russ., was induced and a chlorophyllous cell suspension culture was established using a modified Murashige and Skoog's medium without plant hormones. Cell growth in the light in the presence of glucose started after a short lag and was exponential for 12 days. The chlorophyll level was about 15 μg (mg cell dry weight)−1 and photosynthetic activity ca 20 to 50 μmol O2 (mg chlorophyll)−1h−1. Cell growth in the light was negligible in the absence of glucose under ordinary air, but photoautotrophic growth was possible under elevated CO2 concentrations. In the dark, the moss cells grew heterotrophically and continued to synthesize chlorophyll, although at a much reduced rate. The suspension‐cultured cells redifferentiated protonemata and shoots when transferred to solid Knop's medium. In contrast to the callus cells, which could not assimilate nitrate, redifferentiated plantlets could use nitrate as the sole nitrogen source.
Fluorescence properties of plasma membranes from oats and cauliflower in relation to blue light physiology
Authors: Widell Susanne , Sundqvist Christer
Published: May 2006

Fluorescence properties of plasma membranes from dark‐grown oat shoots (Avena saliva L. cv. Sol II) and from cauliflower inflorescences (Brassica oleracea L.) were investigated. Along with a flavin (with a possible connection to blue light physiology), a blue fluorescing component was present. The effect of NaN3, phenyl acetic acid (PAA), KI (flavin inhibitors) and salicylhydroxamic acid (SHAM; inhibitor of e.g. the blue light‐induced cytochrome b reduction) were followed with regard to the fluorescence properties of the two components as well as with regard to the light‐induced cytochrome b reduction (LIAC). A change in flavin fluorescence and LIAC occurred at about the same concentration of PAA and SHAM, while LIAC was much more sensitive to KI and NaN3 than was the fluorescence. Rapid freezing and thawing did not change the relative fluorescence emission from the flavin and blue fluorescing component, respectively, but storage at ‐20°C for one or two days increased the fluorescence, especially from the latter. There did not seem to be a tight coupling between the fluorescence properties of the blue fluorescing component (spectrally similar to a pteridine) and the flavin. Therefore, no conclusions could be drawn concerning their connection in blue light physiology, i.e. in processes such as phototropism.
Hydroxamate‐activated peroxidases in potato tuber callus. Interaction with the determination of the cytochrome and the alternative pathways
Authors: van der Plas Linus H. W. , Gude Henk , Wagner Marijke J.
Published: May 2006

In potato (Solatium tuberosum L. cv. Bintje and Doré) callus a very active hydrox‐amate‐stimulated NADH‐dependent O2‐uptake develops during the growth of the callus, which is caused by a peroxidase. More than 95% of the peroxidase activity is found in the 40000 g supernatant. The total activity may be as high as 1000 times the respiratory acitivity of the callus tissue. At least two fractions, obtained by Sephadex gel filtration, can be distinguished showing this peroxidase activity, one of about 15 kDa and one > 50 kDa.

The main properties of both fractions are:

a) Hydroxamate at 0.2–0.5 mM gives half‐maximal stimulation. Maximal stimulation is observed with 1–3 mM benzhydroxamate (BHAM) and 1–15 mM salicylhydroxamate (SHAM). Higher concentrations, especially of BHAM, give less or no stimulation.

b) Hydroxamates are not consumed during the reaction.

c) Both NADH and NADPH can serve as the electron donor for the reaction. The affinity for NAD(P)H is very low (Km near 10 mM). In the absence of hydroxamates NAD(P)H is only slowly oxidized, with an even lower affinity.

d) The peroxidase can carry out two reactions: an O2‐consuming and a H2O2‐consuming reaction. In both reactions one NAD(P)H is consumed. In the first reaction H2O2 is formed which can be consumed in the second reaction, resulting in an overall stoichiometry of 2 NADH consumed for each O2 molecule and in the production of H2O.

e) The reaction is completely blocked by cyanide, superoxide dismutase (EC 1.15.1.1) and (excess) catalase (EC 1.11.1.6), but not by antimycin A or azide. This peroxidase‐mediated O2‐uptake might interfere with respiratory measurements. In experiments with isolated mitochondria this interference can be prevented by the addition of catalase to the reaction mixture. The use of high concentrations of hydroxamate is not allowed because of inhibitory effects on the cytochrome pathway. In intact callus tissue hydroxamates only stimulate O2‐uptake in the presence of exogenous NADH. In vivo the peroxidase does not appear to function in O2‐uptake, probably because of its localization (at least partly in the cell wall) and/or its low affinity for NADH. The use of hydroxamates in the determination of cytochrome and alternative pathway activity is discussed.
Phytochrome‐mediated development of glycine oxidation by mitochondria in cucumber cotyledons
Authors: Morohashi Yukio
Published: May 2006

The development of glycine oxidation activity in mitochondria in etiolated cucumber (Cucumis sativus L., cv. Shinfushinari) cotyledons is regulated by phytochrome. This conclusion is based on two lines of evidence. 1. The oxidation activity was increased by continuous illumination of far‐red light. 2. It was also increased by brief red light pulses, the effect of which was reversed by brief far‐red light pulses. The light‐induced increase in glycine oxidation and in glycine decarboxylase (EC 2.1.2.10) activity in the cotyledons was inhibited by cycloheximide, but not by chloramphenicol. While glycine oxidation activity continued to increase during light‐illumination for 20 h, malate oxidation activity increased for 6 to 8 h after illumination and decreased thereafter. This transient increase in the activity of malate oxidation was also induced by red light pulses and the effect of the red light was reversed by far‐red light pulses.
Stimulation by thioredoxin of shikimate kinase from spinach chloroplasts
Authors: Schmidt C. L. , Schultz G.
Published: May 2006

The activity of shikimate kinase (EC 2.7.1.71) from spinach (Spinacia oleracea L.) chloroplasts was increased up to 8.5‐fold by addition of thioredoxin and dithio‐threitol.
Effects of pressure on germination of seeds of wheat (Triticum aestivum cv. Barqai) in saline and in non‐saline media
Authors: Malki E. , Waisel Y.
Published: May 2006

The effects of an increase in the absolute environmental pressure (air, N2, O2 or hydrostatic), up to 1 MPa, on the germination of wheat seeds and the survival of wheat seedlings were studied. Seeds were exposed to saline and non‐saline media, in Petri dishes, on a double layer of filter paper. They were then introduced for different time periods into a pressure chamber and pressurized by the addition of N2 to the chamber in the range of ambient to 1 MPa. Subsequently the seeds were left to germinate under normal atmospheric conditions. Seed germination and subsequent growth decreased during the first 6 h and then regained the control levels. Nevertheless, application of similar pressures to seeds which had been submerged under water was highly inhibitory. Such effects of pressure seem to be the result of flooding with water of some crucial intercellular spaces and a consequent disturbance of O2 supply to the germinating embryo. The additional flood‐water comprised only 1–3% of the total water content of 24‐h‐old seedlings. Sensitivity of the submerged seeds and the germinating seedlings to pressure varied with age and developmental stage. Highest sensitivity to pressure was obtained with 12 to 72‐h‐old submerged seedlings. Removal of the excess water after the pressure treatment restored the germinability of the seeds.
Effects of NaCl, pH and Ca2+ on autolysis of isolated tomato fruit cell walls
Authors: Rushing James W. , Huber Donald J.
Published: May 2006

Cell walls isolated from ripening tomato (Lycopersicon esculentum Mill. cv. Rutgers) fruit released pectic polymers when incubated under conditions that allow activity of wall‐bound polygalacturonase (EC 3.2.1.15). Autolysis was optimally stimulated by 150–300 mM NaCl at either pH 2.5 or 4.5. This stimulation was negated by exposure to pH 6.5 or higher and by pretreatment of walls with boiling 80% ethanol. Five mM CaCl2 did not affect autolysis at pH 2.5, but significantly inhibited at pH 4.5 or higher. Inclusion of 1 M NaCl at selected steps in the extraction scheme did not inhibit subsequent autolysis of isolated walls. Exposure of isolated walls to 1 M NaCl at pH 2.5–8.5 also did not inhibit autolytic activity compared to walls that received no ionic treatment. These data support the concept that cell wall hydrolysis during tomato fruit softening is regulated by pH, Ca2+ levels and ionic strength of the apoplast.
Phytochrome involvement in stomatal movement in Pisum sativum, Vicia faba and Pelargonium sp.
Authors: Roth‐Bejerano Nurit , Itai Chanan
Published: May 2006

Red and blue light triggered the opening of isolated stomata of Pisum sativum L. cv. Peleg Alvador, Vicia faba L. (unknown cultivar) and Pelargonium sp. The stimulatory effect of short irradiation with red or blue light was reversed by a subsequent short irradiation with far‐red light. In Pisum the stimulatory effect of a continuous irradiation with red or blue light was also abolished by a concomitant far‐red light. In leaf pieces of P. sativum blue light was more effective than red, but not in isolated guard cells. In the presence of mesophyll, DCMU inhibited stomatal opening in red light more than in blue, and thus increased the relative response to blue light. This was less evident in isolated guard cells.
In vivo nitrate reductase activities in different organs of lucerne plants: Effects of combined nitrogen during first vegetative growth and after shoot harvest
Authors: Deroche Marie‐Esther , Babalar Mesbah
Published: May 2006

Nitrate reductase (EC 1.6.6.1–3; NR) activity was evaluated in nodulated lucerne (Medicago sativa L. cv. Europe) grown aeroponically in both the presence and absence of applied nitrogen. Determination of in vivo NR activity was done with organ pieces in 0.1 M K+‐phosphate, pH 7.5, 0.1 M KNO3 and 1%n‐propanol. NR activity was detected in all plant parts. Leaves accounted for 40% of the whole plant activity. Root activity was as high as leaf activity. Stem NR activity accounted for 14 to 20% of the total plant activity. NR activity was also detected in symbolically dependent plants grown without combined nitrogen. Nodule NR in symbolically dependent plants accounted for 17% of the tolal plant aclivity. When nitrate was present in the nulrienl medium, NR increased 5‐fold as compared lo N2‐dependenl plants. Varying levels of nitrale (1.65 to 4 mM) had no influence on leaf or stem activities. However, root NR activity seemed to be related to the nitrale concentration in the nulrient medium. Throughoul inilial vegelative growth, in vivo NR and nitrogenase (acelylene reduction) increased simultaneously. After shoot harvest, nitrogenase (acetylene reduction) aclivity drastically decreased with reduction of photosynthate supply, whereas NR increased in all organs, especially in N2‐dependenl plants.
Ca2+ and peroxidase derived from cultured peanut cells
Authors: Hu Chunfang , Lee David , Chibbar Ravindra N. , van Huystee Robert B.
Published: May 2006

A 5% increase of Ca2+ content of the incubation medium for cultured peanut (Arachis hypogaea L.) cells caused a rise of peroxidase (EC 1.11.1.7) activity in the medium, which could be abolished by the addition of the chelator EGTA [eth‐yleneglycol‐bis‐(β‐aminoethyl ether)‐N,N,N',N'‐tetraacetic acid]. However, the determination of in vivo peroxidase synthesis in these cells showed that Ca2+ had a direct effect on the biosynthesis rather than on transport alone. This concept was re‐enforced by the lack of effect by the ionophore A23187 on the transport. The Ca2+ content was 2 and 5 mol (mol protein−1) for the cationic and anionic peanut peroxidase, respectively. The latter is different from the value reported for the anionic peroxidase from horseradish.
Endogenous polyamines in apple and their relationship to fruit set and fruit growth
Authors: Biasi Rita , Bagni Nello , Costa Guglielmo
Published: May 2006

The distribution of free and bound polyamines was investigated from blooming until harvest on flower, fruitlets and fruits of Malus domestica Borkh cv. Golden Delicious, Relationships between polyamines and fruit set and growth were also investigated. The level of free polyamines was high only during the first weeks after full bloom and then decreased gradually. The amount of bound trichloroacetic acid‐insoluble polyamines was much higher than free polyamines. Bound spermine in particular showed a high value for almost 40 days after full bloom, while spermidine and putrescine were no longer detectable even a few days after full bloom.

In relation to fruit set, it was possible to observe that abscission peaks took place when free polyamine levels were low or decreasing. Insofar as fruit growth is concerned, the most substantial variations in polyamine levels occurred very early in the season when fruit dry weight and protein amount were also changing rapidly and fruit diameter was almost impossible to measure.
Effects of low temperature acclimation upon photosynthetic induction in barley primary leaves
Authors: Sicher Richard C. , Sundblad Lars‐Göran , Öquist Gunnar
Published: May 2006

Oxygen evolution and chlorophyll fluorescence were measured in cold‐hardened and unhardened leaves of barley (Hordeum vulgare L. cv. Asa) during the induction period of photosynthesis. The lag phase of light‐saturated photosynthesis was increased and steady‐state rates of photosynthesis were higher in cold‐hardened than in unhardened barley leaves. Fluorescence was quenched more rapidly during the first minutes of induction in hardened than unhardened leaves, largely because of greater energy‐dependent quenching (qE). Also, slow fluorescence transients through the M peak were delayed and less pronounced in cold‐hardened than in unhardened leaves. Based upon the combined fluorescence and oxygen evolution data it was concluded that cold‐hardening delayed light activation of the energy consuming carbon reduction cycle, thereby delaying the use of ATP and NADPH formed in the light reaction. Measurements of oxygen evolution and fluorescence kinetics during photosynthetic induction under oxygenic and anoxygenic conditions suggest that oxygen photoreduction is important for additional ATP generation during both the onset of photosynthetic carbon assimilation and during steady‐state photosynthesis.
The regular ultrastructure of isolated prolamellar bodies depends on the presence of membrane‐bound NADPH‐protochlorophyllide oxidoreductase
Authors: Ryberg Margareta , Sundqvist Christer
Published: May 2006

Light‐induced alterations of isolated prolamellar bodies (PLBs) were studied in flash‐irradiated suspensions of a PLB‐enriched fraction and a mixed membrane fraction isolated from dark‐grown seedlings of wheat (Triticum aestivum L. cv. Walde). The mixed membrane fraction consisted of PLB fragments and membrane vesicles originating from the prothylakoids. Ultrastructural and spectral properties, as well as pigment and protein composition of non‐irradiated and of flash‐irradiated suspensions were studied. The addition of 0.3 mM NADPH prevented spectral shifts towards shorter wavelengths in irradiated as well as in non‐irradiated PLB‐fractions. as measured by fluorescence emission at – 196°C. In non‐irradiated PLB‐fractions the amount of phototransformable protochlorophyllide (PChlide) as compared to nonphototransformable PChlide decreased when NADPH was not added. The emission maximum due to chlorophyll(ide) shifted from 696 nm to 680 um in the flashirradiated fractions where no NADPH was added. The amount of chlorophyllous pigments, as well as the amount of NADPH‐protochlorophyllide oxidoreductase, decreased during the experimental period of 4 h in the suspensions without added NADPH. especially in the irradiated ones. The ultrastructure of the pelletable material in the different suspensions was analyzed by transmission and scanning electron microscopy. The non‐irradiated PLBs appeared as cottonball‐like structures in the scanning electron microscope. Without NADPH added more PLBs with an irregular tubular appearance were seen. After irradiation and storage for 1 h in darkness the surface was covered with vesicles. These vesicles were still present after 4 h. In the presence of NADPH no vesicle‐formation occurred and the regular network of the PLBs was preserved also after an irradiation which caused transformation of PChlide to chlorophyllide. Thus, the regular structure seems to depend on an ample supply of NADPH. which in turn may be necessary to stabilize the pigment‐protein complex in the lipid moiety of the PLB membranes. The formation of vesicles may thus be caused by a loss of this pigment‐protein complex in suspensions with a low level of NADPH. The possible significance of an NADPH‐dependence in vivo is discussed.
Photoautotrophic growth in suspension culture of cells from the moss, Barbula unguiculata
Authors: Takami Shinji , Nishikawa Shinji , Takio Susumu , Hino Seiichi
Published: May 2006

Chlorophyllous cells in suspension culture from the moss, Barbula unguculata Hedw., grown under photoheterotrophic conditions were transferred to photoautotrophic conditions. The cells started to grow photoautotrophically without selection. Maximum growth was observed under irradiances of more than 5 W m2 and in an atmosphere enriched with 1% (v/v) CO2. Under optimum growth conditions, dry weight and chlorophyll content in the culture had increased 20‐fold after 20 days of cell growth. High concentration of chlorophyll [10–20 μg (mg dry weight)−1] and high photosynthetic actively [30–70 μmol O2 evolved (mg chlorophyll)−1 h−1] were observed throughout the culture period. In sugar‐free culture medium, cell growth did not occur in the dark or in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) under light, although cell growth was observed in glucose‐containing medium under those conditions. When cells that were grown photoautotrophically for one year were transferred to glucose‐containing medium under ordinary air, they started to grow heterotrophically both in the light and in the dark.
Vigor and salt tolerance in 3 lines of tall wheatgrass
Authors: Weimberg Ralph , Shannon Michael C.
Published: May 2006

The F1 progeny of the cross of two salt‐tolerant lines of Thinopyrum elongatum [Host] D. R. Dewey grew better than either parent under non‐saline and saline growth conditions. Under non‐saline conditions, the hybrid produced 1.8 times as much vegetative tissue as one parent and 3.2 times more than the other parent in the same length of time. The relative growth rates of the 2 parental lines decreased equally as media osmotic potentials decreased. The relative growth rate of the hybrid did not decrease as rapidly as that of the parents; therefore, it was concluded that the greater growth of the hybrid was due to increased salt tolerance. Carbohydrate reserves and water‐soluble solutes believed to be involved in osmotic adjustment were assayed to determine if there were any differences between the hybrid and its parents in their abilities to accumulate these compounds. The concentrations of these constituents were measured at dawn and at dusk of the same day in plants grown in media at osmotic potentials ranging from –0.1 to –1.2 MPa. There were no differences in pool sizes of the organic compounds in the 3 lines. Starch increased 10–40 fold in leaves from dawn to dusk and sucrose increased 100‐fold. However, this pattern was unaffected by salinity. Conversely, betaine concentrations increased with increasing salinity but were the same at dawn and dusk. Na+ and K+ were affected by both light and salinity. Cl was one‐half (Na++ K+) on a molar basis under all conditions. Proline accumulated when (Na++ K+) exceeded 200 μmol (g fresh weight)−1. Since this amount of (Na++ K+) existed only in tissues harvested at dusk from severely saline‐stressed plants, only leaves from such plants harvested at dusk contained proline.
Lupin peroxidases. II. Binding of acidic isoperoxidases to cell walls
Authors: Barceló Alfonso Ros , Pedreño M. Angeles , Muñoz Romualdo , Sabater Francisco
Published: May 2006

Extracellular acidic isoperoxidases (EC 1.11.1.7), isolated from both the cell walls and intercellular spaces of lupin (Lupinus albus L. cv. multolupa) hypocotyls, bound to water‐insoluble pectins of wall fragments also isolated from the hypocotyls. The binding was sáturable by increasing the isoenzyme concentration in the assay medium and it was dependent on the pH; neutral pH (6.0–7.0) favoured release, while acidic pH (4.0–5.0) favoured the attachment to the cell wall. Binding of acidic isoperoxidases to wall fractions was correlated with the in vitro acid‐induced growth of hypocotyl segments, and both were modulated in the same direction by the Ca2+/H+ ratio in the incubation media, although the two responses were clearly separated when the Ca2+/H+ ratio varied. Binding of acidic isoperoxidases of cell walls could operate as a fine control of the activity of these cell wall enzymes, although its physiological role in the cell wall stiffening remains unclear. Some aspects of Ca2+ on the control of peroxidase activity at this level are also discussed.
The effect of daylength on photosynthate partitioning into leaf starch and soluble sugars in a gibberellin‐deficient dwarf mutant of Zea mays
Authors: Britz Steven J. , Saftner Robert A.
Published: May 2006

The possibility that gibberellins (GAs) mediate the photoperiodic regulation of photosynthate partitioning into stored leaf carbohydrates (starch and soluble sugars) was investigated with the dwarf‐5 mutant of Zea mays L., a single‐gene recessive mutant with greatly reduced endogenous GA content relative to tall maize. The mutant responded to daylength as did tall maize, with higher rates of carbohydrate accumulation observed under short daylength (8.5 h of light) than under long day‐length (14 h of light). Neither inhibitors of GA biosynthesis (CCC, [(2‐chloroethyl) trimethylammonium chloride], ancymidol[α‐cyclopropyl‐α‐(p‐methoxy‐phenyl)‐5‐pyrimidine methyl alcohol], and tetcyclacis [5‐(4‐chlorophenyl)‐ 3,4,5,9, 10‐penta‐azatetracyclo‐5,4,1,02.6,08.11‐dodeca‐3.9‐diene]) nor treatment with GAs further modified the response of partitioning to daylength even though biologically active GAs stimulated plant growth. The results indicate that photoperiodic modulation of endogenous GA titre is unlikely to be responsible for the photoperiodic response of photosynthate partitioning in Z. mays.
Growth and gibberellin relations of the extreme dwarf dx tomato mutant
Authors: Nadhzimov U. K. , Jupe S. C. , Jones M. G. , Scott I. M.
Published: May 2006

The extreme dwarf dx tomato (Lycopersicon esculentum Mill.) mutant has very short internodes which were found to contain shorter and fewer epidermal cells. The leaves are highly abnormal. The mutant showed a substantial stem growth response to GA3, without approaching normal stature or morphology. The active gibberellin GA1 and its precursors GA19 and GA20 were identified by coupled gas chromatography‐mass spectrometry (GC/MS) in dx shoots. Quantitative GC/MS revealed that GA20 accumulated to far higher levels than normal in stems and leaves of the mutant.
Changes in ribulose‐1,5‐bisphosphate carboxylase and its translatable small subunit mRNA levels during senescence of mustard (Sinapis alba) cotyledons
Authors: Kasemir Helga , Rosemann Detlef , Oelmüller Ralf
Published: May 2006

Senescence of mustard (Sinapis alba L.) cotyledons was studied by monitoring the levels of ribulose‐1,5‐bisphosphate carboxylase (RuBP carboxylase, EC 4.1.1.39) activity, enzyme protein and translatable mRNA of the small subunit (SSU‐mRNA) of RuBP carboxylase. In continuous white light (cWL) RuBP carboxylase began to decline 6 days after sowing and the decrease in SSU‐mRNA preceded the drop in enzyme protein. The decline in RuBP carboxylase was more pronounced when the seedlings were transferred to darkness. This dark‐mediated senescence was affected by phytochrome (Pfr) primarily by retardation of enzyme degradation and to a lesser extent by the maintenance of gene expression. When seedlings were reirradiated with cWL or red light after being kept for 6–8 days in darkness the levels of enzyme protein and SSU‐mRNA again increased. Thus, even after long periods of darkness the seedlings retained their ability to respond to light with renewed gene expression which was affected by Pfr. Under short‐day conditions (8 h light/16 h dark), almost no decline of RuBP carboxylase occurred, whereas SSU‐mRNA decrease followed the same pattern as in cWL or darkness.
Phototactic responses of Chlamydomonas reinhardtii in electric fields
Authors: Ekelund Nils G. A. , Dolle Reiner , Nultsch Wilhelm
Published: May 2006

Chlamydomonas reinhardtii Dangeard strain Göttingen 11 – 32(+) responds both phototactically and galvanotactically. If electric fields and a light stimulus of 496 nm were applied simultaneously, phototaxis persisted but the response was modified. Field lines perpendicular to the phototactic direction of movement inhibited phototaxis. If the field lines were parallel to the light direction, the effect depended on the position of the poles. When the cathode faced the light, an increase of the phototactic reaction values was observed. In this case electric fields enhanced positive phototaxis with increasing voltages from 3 V up to 12 V. If the cathode was on the opposite side, positive phototactic movement was inhibited. The maximum inhibition was found at 12 V. At this voltage positive phototaxis was measured neither at low nor at high fluence rates, and positive phototaxis was shown only between 0.1 and 1.5 W m−1.
Application of growth analysis to physiological studies involving environmental discontinuities
Authors: Wickens Linda K. , Cheeseman John M.
Published: May 2006

In this report we consider the application of growth analysis techniques in environmental physiology, with particular concern for their ability to produce results which can be integrated with studies of short‐term metabolic responses at finer levels of organization. For purposes of illustration, we use responses of Spergularia marina (L.) Griseb. and lettuce (Lactuca sativa L. cv. Black‐seeded Simpson) to changes (environmental discontinuities) in the composition of a solution culture medium. Initial emphasis is on the use of cubic spline methods. It is concluded that while these may give apparently good fits to growth data, differentiation for determination of relative growth rate (RGR), and further transformation for such parameters as net uptake rate (NUR), are of questionable applicability. An alternative analysis based on the discrete estimation of RGR is considered.

In any study, the requirements for both statistical and physiological confidence must be reconciled. In practice, and in the absence of mechanistic frameworks to which the results can be modeled, this is best accomplished by strictly adhering to the mathematical guideline that no more elaborate a description be applied than can be statistically justified.
Regulation of respiration in roots of barley
Authors: Bingham I. J. , Farrar J. F.
Published: May 2006

The regulation of respiration in roots of barley [Hordeum distichum(L.) Lam. cv. Maris Mink] was examined in terms of the supply of carbohydrate and control by adenylates. The carbohydrate content of roots was modified by selective pruning and feeding sucrose (25 mM) and rates of O2uptake were measured 16–24 h later. Pruning roots to a single seminal axis increased the soluble sugar content of the sole remaining root by 30% and its rate of O2uptake by 24%: pruning shoots so that all but the second leaf was removed lowered the soluble sugar content of the roots by 39% and their rate of O2uptake by 34%. Changes in the rate of O2uptake were due largely to adjustments in activity of the cytochrome path (vcyt): these changes were accompanied by comparable adjustments in capacity of the path (Vcyt) so that it always operated close to full engagement (=90%). The capacity of the alternative path was unchanged and in no case was there any engagement. Since the alternative path failed to engage over a wide range of carbohydrate contents, we conclude that this path does not function as a simple energy overflow in barley roots. Irrespective of pruning treatment respiration appeared to be limited directly by the turnover of ATP since rates of O2uptake were stimulated by the uncoupler FCCP, but not by short‐term (< 1 h) feeding of sucrose. However, long‐term feeding of sucrose (16–24 h) to roots of leaf‐pruned and control plants resulted in an increase in both vcytand Vcyt. It is proposed that whilst the rate of O2uptake is regulated directly by the turnover of ATP, some energy‐consuming processes might be sensitive to the carbohydrate concentration: changes in supply of carbohydrate with selective pruning or sucrose feeding may alter rates of these processes and regulate vcytthrough changes in energy demand. The nature of adjustments in Vcytand the possible role of the alternative path are discussed.
The semidian rhythm in flowering response ofPharbitis nilin relation to dark period time measurement and to a circadian rhythm
Authors: Heide O. M. , King R. W. , Evans L. T.
Published: May 2006

When seedlings ofPharbitis nilChoisy, cv. Violet, are exposed to a single inductive dark period at 27°C, brief interruptions with red light (R) can be promotive after 2–3 h ofdarkness but increasingly inhibitoryto flowering up to the 8–9th h of darkness. This rhythmic response to R interruptions can be advanced in phase by > 1 h when the preceding light period is interrupted with far‐red (FR) 2 h before darkness (FR ‐2 h) or with FR – 15 h, whereas FR –8 h or FR–22 h retard the rhythm. These shifts in the R interruption rhythm are paralleled by equal shifts in the length of the dark period required for flowering. Brief FR interruptions of darkness displayed a similar rhythm which was also advanced by FR –2 h and retarded by FR –8 h. We conclude therefore that the semidian rhythm in the light, which we have previously described, continues through at least the first 12 h of darkness, is manifested in the R interruption rhythm, and determines the critical night length. A circadian rhythm with a marked effect on flowering was also identified, but several lines of evidence suggest that the circadian and semidian rhythms have independent additive effects on flowering and do not appear to show phase interaction.
Participation of the cyanide‐resistant pathway in respiration of winter rape leaves as affected by plant cold acclimation
Authors: Rychter Anna M. , CieásAla E. , Kacperska A.
Published: May 2006

Leaf slices sampled from winter rape plants (Brassica napus L., var. oleifera L., cv. GórczaánAski), grown in cold (5°C), showed an increase in the dark respiration rate (measured at 25°C) as compared to slices cut from control plants (grown at 20/15°C). The effect of low temperature was most pronounced after 4 days of plant growth in the cold. Oxygen uptake by control slices was 60% inhibited by 1 mM KCN and was insensitive to 2.5 mM salicylhydroxamic acid (SHAM). On the contrary, respiration of leaf slices from cold‐pretreated plants was more resistant to cyanide (35% inhibition after 4 days of cold treatment) and was 30% inhibited by SHAM. The patterns of cold‐induced changes in total respiratory activity and in the estimated activity of alternative pathway were similar. It seems that in leaf slices from plants grown in the cold, the cyanide‐resistant, alternative pathway participates in oxygen uptake. Cold treatment of plants also brought about a 4‐fold increase in the level of soluble sugars, which reached a maximum on day 4 of exposure to cold. Addition of sucrose to the incubation medium resulted in an immediate increase in oxygen uptake by slices with low endogenous sugar level. The respiration stimulated by sucrose addition was more resistant to cyanide than the basal respiration and it was inhibited by SHAM. It is concluded that the operation of the alternative pathway is responsible for the increased oxygen uptake by the cold‐grown winter rape leaves and it may be induced by an increased sugar supply for respiratory processes.
Cell enlargement and growth‐induced water potentials
Authors: Boyer John S.
Published: May 2006

Understanding the origin and role of growth‐induced water potentials helps to explain how cell enlargement is inhibited without a decrease in turgor when water is depleted in the soil or more rapidly lost by transpiration. In many cases, changes in growth‐induced water potentials probably cause the inhibition initially, but eventually the cell walls lose extensibility and specific proteins accumulate so that metabolic changes in the walls probably limit later growth.
Germination of annual celery (Apium graveolens) seeds: Inhibition by paclobutrazol and its reversal by gibberellins and benzyladenine
Authors: Pressman Etan , Shaked Rachel
Published: May 2006

Plants of annual celery (Apium graveolens L.) were treated with paclobutrazol during anthesis. Seeds collected from the treated plants showed a marked reduction in germination in light and failed to germinate in the dark. Application of GA4/7 to the imbibition solution reversed the inhibitory effect of paclobutrazol while gibberellic acid (GA3) was ineffective. Benzyladenine (BA) interaction with GA4/7 was light and concentration‐dependent. At relatively low concentrations in the dark there was a synergistic effect, but at higher concentrations, especially in the light, BA, antagonized the GA4/7 effect. Seedlings emerging from the seeds from paclobutrazol‐treated plants were only slightly shortened. It is suggested that paclobutrazol applied to the mother plants inhibited the biosynthesis of endogenous GAs, which normally enable the germination of annual seeds under unfavorable conditions. Exogenously applied GA4/7 fulfills the function of the absent endogenous GAs.
Isolation and enzymological characterization of infected and uninfected cell protoplasts from root nodules of Glycine max
Authors: Kouchi Hiroshi , Fukai Katsuhiko , Katagiri Hiroki , Minamisawa Kiwamu , Tajima Shigeyuki
Published: May 2006

Infected and uninfected cell protoplasts were isolated from soybean (Glycine max L. Merr. cv. Akisengoku) root nodules and purified by the use of nylon mesh filters and discontinuous Percoll gradients. Activities of the enzymes involved in carbon and nitrogen metabolism were measured in cytoplasmic fractions of purified protoplasts, as well as in the bacteroids isolated from infected cell protoplasts and in the cortical tissues after enzymatic digestion of the central zone of the nodules.

A high degree of purity of both infected and uninfected cells was demonstrated by microscopic observations and assays of β‐hydroxybutyrate dehydrogenase (EC 1.1.1.30) and uricase (EC 1.7.3.3) activities and leghemoglobin contents.

As a whole, higher specific activities of enzymes of glycolysis were found in the cortical and uninfected cells than in the infected cells. The activities of glycolytic enzymes were extremely low in the bacteroids. Invertase (EC 3.2.1.26) was highly localized in the cortex. However, activity of sucrose synthase (EC 2.4.1.13) was highest in the cytosol of infected cells. Alcohol dehydrogenase (EC 1.1.1.1) and lactate dehydrogenase (EC 1.1.1.27) activities were much higher in uninfected than in infected cells. Specific activities of enzymes for nitrogen assimilation, that is, glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.14), aspartate (EC 2.6.1.1) and alanine (EC 2.6.1.2) aminotransferase were several‐fold higher in uninfected cells than in the infected cells.

The results are discussed in relation to the possible cellular organization of carbon and nitrogen metabolism in soybean root nodules.
Combined effect of light and temperature on triacylglycerol accumulation in Dicranum elongatum
Authors: Karunen Pirjo , Hakala Kaija , Mikola Heikki
Published: May 2006

In the subarctic moss Dicranum elongatum Schleich & Schwaegr., the level of total lipids and triacylglycerols (TAG) was high in late winter and spring and low in autumn and winter. Four‐week exposure of field material to continuous light (135μmol m−2s−1) at 1°C resulted in a considerable increase in the amount of TAG in the autumn material acclimated to low temperatures and rhythmic light in the field. In contrast, the same treatment did not cause any increase in TAG in the spring material, acclimated to low temperatures and continuous light in the field. Results from experiments, in which moss cultivated for 4 months at 9°C on 12‐h photoperiods (135μmol m−2s−1) was kept for 3 weeks at low temperatures (9°C and −3°C) either in continuous light (135 or 70 μmol m−2s−1) or with 12‐h photoperiods (135 μmol m−2s−1), indicated that the TAG level was higher at higher light intensity. At 9°C it was also higher in continuous light of both intensities than in rhythmic light. These results strongly suggest that decreasing irradiance and decreasing daylength limits the accumulation of TAG in D. elongatum during autumn in the subarctic.
Identification and quantitation of gibberellins in fruits of Lycopersicon esculentum, and their relationship to fruit size in L. esculentum and L. pimpinellfolium
Authors: Bohner J. , Hedden P. , Bora‐Haber E. , Bangerth F.
Published: May 2006

GA1, GA8, GA17, GA19, GA20 and GA29 were identified by combined gas chromatography‐mass spectrometgry (GC‐MS) in immature seeds and pericarp of Lycopersicon esculentum Mill. (tomato). Higher levels of these GAs were present in the seeds than in the pericarp; seeds in addition contained GA15, GA24, GA25, and GA44. Fruits of the Lycopersicon pimpinellifolium Mill. mutant I were smaller and contained lower GA1 concentrations, but higher GA20 concentrations, than those of mutants III and IV. In contrast, differences in fruit size in L. esculentum due to position on the truss did not correlate with GA1 concentration in either the pericarp or seeds.
Auxin‐induced delay of abscission: The involvement of calcium ions and protein phosphorylation in bean explants
Authors: Poovaiah B. W. , Friedmann M. , Reddy A. S. N. , Rhee J. K.
Published: May 2006

Treatment with Ca2+ channel blockers such as lanthanum chloride and verapamil promoted abscission in pulvinar explants of bean (Phaseolus vulgaris L. ev. Pirate). In addition, auxin‐induced delay of abscission was markedly reduced in the presence of Ca2+ channel blockers. In vitro phosphorylation studies were performed using membrane preparations (130000 g pellet) from freshly excised as well as auxintreated and control (minus auxin) pulvinar sections. Auxin‐treated sections showed a 66 kDa phosphoprotein as well as Ca2+ ‐dependent phosphorylation that were not observed in control explants.

Coomassie blue stammg of soluble proteins (130000 g supernatent) separated on SDS‐PAGE revealed the presence of 62. 55 and 47 kDa polypeptides only in the freshly excised pulvini. However. no distinct changes were observed in soluble protein profile between auxin‐treated and control explants. When soluble proteins were phosphorylated in vitro, Ca2+ promoted the phosphorylation of 92, 55. 40 and I7 kDa polypeptides only in freshly excised pulvmi. Ca2+‐dependent phosphorylation of soluble proteins was not observed in either the control or auxin‐treated explants. In addition. in vivo phosphorylation studies were performed using freshly excised. auxrn‐treated and control explants. Freshly excused segments and auxin‐treated ex‐plants showed similar phosphoproteins, which were different from those observed mcontrol.
Induction of secondary dormancy in sunflower seeds by high temperature. Possible involvement of ethylene biosynthesis
Authors: Corbineau F. , Rudnicki R. M. , Côme D.
Published: May 2006

High temperature (45°C) inhibits seed germinition and seedling sunflower (Helianthus annuusL. cv. Mirasol). Treatment of imbibed seeds at 45°C for more than 48 h induces a secondary dormancy, which is associated with progressive decrease of germination ability at optimal temperature (25°C) as well as with abnormal seedling growth. Ethylene (55μl l−1) and 2‐chloroethylphosphonic acid (ethephon) (2.5 mM) improve germination of thermodormant seeds at 25°C. but the abnormal growth of the seedlings remains. O2‐enriched atmosphere and dry storage improve germination and normal seedling growth. The induction of thermodormancy in sunflower seeds seems associated with loss of their ability to convert 1‐aminocyclopropane‐1‐carboxylic acid (ACC) to ethylene. Possible effects of high temperature on membranes and ethylene forming enzyme (EFE) are discussed.
Effect of oxygen concentration on the senescence and energy metabolism of cut carnation flowers
Authors: Trippi Victorio S. , Paulin André , Pradet Alain
Published: May 2006

The effect of O2 concentration on energy metabolism and senescence has been studied in cut flowers of Dianthus caryophyllus L. cv. Scania. As compared to the control (21% O2), 5% O2 delays flower senescence as well as decay of nucleotide level and AEC (adenylate energy charge). An atmosphere of 100% O2 accelerates senescence as well as the decrease of nucleotide level and AEC. While anoxia brings about a faster decrease of ATP and AEC than of total nucleotides, hyperoxia brings about a faster decrease in adenyl nucleotides than in ATP and AEC values. Petal oxygen uptake is over 90% of the maximal value under 4% O2 and saturates at 10% O2. The development of senescence is dicussed as a two phase process (first phase‐progressive and second phase‐catastrophic) triggered by the action of hyperoxia, first on the system for energy utilization and later on the system for energy production, the degradation of which seems to be linked with increase in membrane permeability and withering.
Identity of cytokinins in Begonia leaves and their variation in relation to photoperiod and temperature
Authors: Hansen C. E. , Kopperud C. , Heide O. M.
Published: May 2006

The identity of cytokinins extracted from leaves of Begonia×cheimantha Everett cv. Nova has been studied by purification and fractionation on Dowex 50 H’ and Sephade× L.H 20 columns followed by reverse‐phase HPLC separation and determination by enzyme immunoassay. The following four cytokinins were identified: trans‐zeatin, trans‐zeatin riboside, isopentenyladenin and isopentenyladenosin. At least three other compounds, possibly glucosides, were detected by activity in the tobacco callus bioassay but not yet identified. The quantity of the identified cytokinins was several times higher at 15 than at 24°C, the former temperature being optimal for regeneration of adventitious buds. At 15°C there was no clear effect of photoperiod whereas short days at 24°C increased the activity several‐fold compared with long day conditions.
Triadimefon stimulates rooting in bean hypocotyl
Authors: Fletcher R. A. , Asare‐Boamah N. K. , Krieg L. C. , Hofstra G. , Dumbroff E. B.
Published: May 2006

Triadimefon, a broad spectrum fungicide and an inhibitor of gibberellic biosynthesis, whitened, thickened, and shortened the roots of bean (Phaseolus vulgaris L. cv. Spring Green) seedlings and stimulated the development of root primordia along the hypocotyl. In a comparative study, triadimefon, IAA, spermidine, putrescine and spermine all stimulated adventitious root growth, but triadimefon was more effective than the other 4 compounds. Equimolar concentrations of gibberellic acid (GA3) completely eliminated the stimulatory effect of triadimefon. Stimulation of root development by triadimefon was accompanied by inhibition of ethylene biosynthesis followed by removal of basal dominance and an increase in polyamine levels, both of which occurred after rooting had begun. Although triadimefon was effective in stimulating rooting, its mechanism of action is apparently not mediated via the control of ethylene and polyamine biosynthesis.
Effects of cyanide and cold treatment on sugar catabolism in apple seeds during dormancy removal
Authors: Bogatek Renata , Lewak Stanislaw
Published: May 2006

The ratio of glycolysis to the pentose phosphate pathway (PPP, C6/C1 ratio), and the activities of glucose 6‐phosphate dehydrogenase (EC 1.1.1.49) and pyruvate kinase (PK, EC 2.7,1.40) were determined in apple seeds (Malus domestica Borb, cv. Antonówka) submitted to cold and warm stratifications. Our results indicated that the elimination of embryonal dormancy in apple seeds was connected with a change from domination of PPP to domination of glycolysis in sugar catabolism during cold stratification. Cyanide pretreatment affected the C6/C1 ratio and the activities of the enzymes under study in such a manner that the maxima of PPP and glycolysis appeared earlier during stratification. We suggest a regulatory role of cyanide in removal of dormancy.
Air pollution by SO2 amplifies the effects of water stress on enzymes and total soluble proteins of spruce needles
Authors: Pierre Michèle , Queiroz Orlando
Published: May 2006

Measurements of soluble protein levels and catalytic capacity (maximum extractable activity) of isocitrate, glucose‐6‐phosphate and glutamate dehydrogenases were performed in needles of Picea abies L. Karst. under phytotron‐controlled conditions in filtered or SO2 polluted (0.08 ppm, 3.1 μmol m−3) air. In watered plants, pollution had no significant effects, although sulphur accumulated in the needles. Water deprivation (1 or 2 weeks depending on the experiments) of non‐polluted plants decreased protein concentration and modified enzyme capacity, particularly for isocitrate and glucose‐6‐phosphate dehydrogenases. These effects were amplified in the polluted plants. Visible damage occurred only in plants subjected to both pollution and water stress. The results indicate that in spruce needles vulnerability of cell metabolism to the effects of a drought period is increased when water deprivation occurs under SO2 pollution.
Comparison of the effects of epibrassinolide and steroidal estrogens on adventitious root growth and early shoot development in mung bean cuttings
Authors: Guan Ming , Roddick James G.
Published: May 2006

Concentrations of 24‐epibrassinolide as low as 0.1 μM consistently inhibited adventitious root formation and elongation in both hypocotyl and epicotyl cuttings from mung bean (Phaseolus aureus L.). Similar, but less pronounced, inhibitory effects on root elongation were also observed with estrone sulphate and estradiol sulphate. With regards to root number, estrone sulphate enhanced this in both types of cutting, whereas estradiol sulphate was stimulatory in hypocotyl cuttings but inhibitory in epicotyl cuttings. Brassinolide caused a marked stimulation of epicotyl (but not hypocotyl) elongation and a swelling and splitting of the epicotyl in both types of cutting, whereas estrogens varied in their effect from inhibition of epicotyl growth to no effect. Root‐applied brassinolide and estrogen sulphates brought about similar morphological abnormalities in shoots viz. epinasty and inrolling of primary leaves and delayed expansion of the first trifoliate leaf.
Response of net photosynthesis in bean (Phaseolus vulgaris) leaves to the elevation of the partial pressures of oxygen and carbon dioxide
Authors: Maleszewski Stanislaw , Kamińska Zofia , Kondracka Agnieszka , Mikulska Maria
Published: May 2006

Bean (Phaseolus vulgaris L. cv. Golden Saxa) plants were grown under low artificial light or under natural daylight. The rate of net photosynthesis (PN) was measured at: CO2 partial pressure, p(CO2), of 0.03, 0.09 or 0.15 kPa; O2 partial pressure, p(O2), of 2, 21 or 31 kPa and at light intensities of 350 or 1000 μmol m−2 s−1 (photosynthetically active radiation). In plants which had been grown under natural light, stimulation of PN at 21 kPa p(O2) was found only at elevated p(CO2) and high light. It is proposed that this phenomenon is dependent on a high capacity of the photosynthetic apparatus to regenerate ribulose 1.5‐bisphosphate.