bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of the photosystem I and II reaction center chlorophyll‐protein complexes, CP‐a1 and CP‐aII with photosystem activity and low temperature fluorescence emission properties in mutants of Scenedesmus
Authors: BISHOP NORMAN I. , ÖQUIST GUNNAR
Published: April 2006

Abstract Comparative studies on the low temperature fluorescence emission of whole cells, purified chlorophyll‐protein (CP) complexes and on patterns noted in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) for chlorophyll‐protein complexes and chloroplast membrane polypeptides of Scenedesmus obliquus with several distinct mutant classes has allowed further correlation between the fluorescence emission bands seen at 77K and the known chlorophyll‐protein complexes. In mutants deficient in photosystem II (PS‐II; total loss of the reducing side) the fluorescence emission spectra showed only two peaks, i.e., 686 and 718 nm, but in the wild type, in mutants lacking the oxidizing side of PS‐II and in phenotypes missing the CP‐a1 complex (and P‐700 activity) all three emission bands at 686, 696 and 718 nm were present. In a mutant lacking the light‐harvesting CP‐a/b complex the emission peak at 686 nm was strongly reduced and the longer wavelength emissions predominated. Gel electrophoresis studies showed that the PS‐II (reducing side) mutants lacked the polypeptides of apparent molecular weight 54 and 51 kilodaltons and the chlorophyll‐protein complex, CP‐aII, of apparent molecular weight 32 kilodaltons. Contrarily, the loss of the oxidizing side of PS‐II did not result in any alteration of these components. Genetic deletion of CP‐a1 did not alter significantly the long wavelength emission even though the isolated CP‐a1 shows the low temperature‐dependent long wavelength emission comparable to that seen in the whole cell. It was deduced that remaining PS‐I antennae chlorophylls must account for the emission seen at 718 nm. The absence of the CP‐a/b complex and the strong simultaneous decrease of the 686 nm emission strengthens the concept that this complex is the primary emitter of fluorescence at room temperature. Its absence facilitated the detection of the CP‐aII complex in SDS‐PAGE and enhanced the in vivo fluorescence by the two photosystems. Parallel experiments with two mutants which green and develop, one to the wild‐type and the other to the CP‐a/b deficient phenotype, provided additional evidence for the source of the low temperature emission bands.
Functional organization and plasticity of the photosynthetic unit of the cyanobacterium Anacystis nidulans
Authors: VIERLING ELIZABETH , ALBERTE RANDALL S.
Published: April 2006

Anacystis nidulans grown under high and low light, 100 and 10 μE m−2 s−1, respectively, was analyzed with respect to chlorophyll/P700, phycobiliproteins/P700, chlorophyll/cell, and oxygen evolution parameters. The photosynthetic unit sizes of this cyanobacterium, measured as the ratio of total chromophores (chlorophyll and bilin) to P700, were shown to be similar to those of higher plants and green algae. High light grown cells possessed a photosynthetic unit consisting of a core of 157 ± 6 chlorophyll a molecules per P700 associated with a light harvesting system of 95 ± 3.5 biliprotein chromophores. Low light grown cells had substantially more biliprotein chromophores per P700 (125 ± 3.1) than high light cells, but showed no significant difference in the numbers of chlorophyll a molecules per P700 (149 ± 4). Analyses of aqueous biliprotein extracts indicate that low light grown cells produce proportionately more phycocyanin relative to allophycocyanin than high light cells. Calculations of the molecular weight of biliproteins per P700 suggest that there is less than one phycobilisome per reaction center I under both growth conditions.

Differences in chlorophyll/cell ratios and oxygen evolution characteristics were also observed. High light cells contain 6.3 × 10−12 mg chlorophyll cell−1, while low light grown cells contain 12.8 × 10−12 mg chlorophyll cell−1. Photosynthetic oxygen evolution rate vs. light intensity curves indicate that high light grown cells reach maximal levels of oxygen evolution at higher light intensity than low light grown cells. Maximal rates of oxygen evolution were 16.6 μmol oxygen min−1 (mg chlorophyll)−1 for high and 8.4 μmol oxygen min−1 (mg chlorophyll)−1 for low light cells. Maximal oxygen evolution rates per cell were equivalent for both cell types, although the amount of P700 per cell was lower in high light cells. High light grown cells are therefore capable of producing more oxygen per reaction center I than low light grown cells.
The influence of kinetin on the endogenous content of indoleacetic acid in swelling seeds of Phaseolus, Zea and Pinus and young plants of Phaseolus
Authors: SALEH ADIRUKMI NOOR , HEMBERG TORSTEN
Published: April 2006

Treatment of different plant materials, seeds of Phaseolus vulgaris, Zea mays and Pinus silvestris and young plants of Phaseolus, with kinetin increased the level of extractable IAA. For seeds this increase was most pronounced in bean seeds, which contained the lowest amount of endogenous IAA and cytokinins, and lower in maize seeds with high endogenous content of IAA and cytokinins. – For young bean plants the kinetin treatment significantly increased the extractable amounts of IAA from all parts of the plant, hypocotyls, cotyledons, epicotyls and primary leaves, when the cut plants were placed for 24 h in kinetin solution. For plants sprayed with kinetin solution only the primary leaves showed a significantly higher level of extractable IAA, which could be explained by the fact that the plants were growing very close together, so that the primary leaves received most of the kinetin during spraying.
Promotion of flowering in the Pinaceae by gibberellins
Authors: PHARIS RICHARD P. , ROSS STEPHEN D. , McMULLAN ELEANOR
Published: April 2006

Significant male and female flowering (cone bud production) by girdled branches of 6‐year‐old Douglas fir (Pseudotsuga menziesii (Mirb. Franco) seedlings was promoted by applications (mid‐April to June) of 1.6 or 3.2 mg per branch (in total) of certain non‐polar gibberellins (GA's). Girdling alone was ineffective. When tested alone, a mixture of GA4/7 was most effective. GA9 less so, while GA5 and the more polar GA3 were essentially ineffective. For female cone buds GA4/7+ GA9 were synergistically effective, but for male cone buds GA4/7 alone was best. The auxin naphthaleneacetic acid (NAA) was not tested alone, but at low dosage (0.175 mg/branch in total) NAA enhanced the flowering efficacy of GA's for both sexes; at a high dosage (0.875 mg/branch in total) male cone bud production was further enhanced, but only at the expense of females. For female flowering the best treatment (90% frequency of flowering 6.8 cone buds/branch), was GA4/7+ GA9+ low NAA; for male flowering, it was GA4/7+ high NAA (30% frequency and 4.2 cone buds/branch. Frequency of flowering for controls was 18% and 0%, average number of cone buds/branch was 0.9 and 0, for females and males, respectively. The successful treatments did not affect promordia initiation, rather they caused the differentiation of previously initiated, but undetermined, lateral primordia into cone and latent buds at the expense of vegetative bud differentiation.

The lack of success reported by earlier workers in promoting flowering in Pinaceae species by GA's appears to be the unfortunate result of selecting GA3 for initial testing. The practical implications of this early and enhanced flowering by non‐polar GA's seedlings of a commercially important conifer are discussed in relation to accelerating the processes of tree improvement.
Morphactin transport and metabolism in tree bark tissues: comparative studies in vitro
Authors: BACKHAUS RALPH A. , SACHS ROY M. , PAUL JACK
Published: April 2006

Bark banding of morphaction is an effective means of controling stem elongation in Pinus radiata D. Don (Monterey pine) but not Juglans regia L. (English walnut). Diffusion coefficients of 14C‐labeled morphactin across excised disks of tree bark, measured in specially designed diffusion chambers, were 11 to 85 fold greater in pine than walnut. In seedlings of comparable age, the suberin layer of walnut bark is much thicker than that of pine; if the layer is removed, diffusion of 14C‐morphactin is enhanced 39‐fold in pine and 285‐fold in walnut.

Morphactin applied to the bark as an ester is rapidly hydrolyzed to its carboxylic acid derivative in both pine and walnut. This conversion occurs rapidly in the bark of both species and does not appear to limit the rate of morphactin movement across the bark.

These results suggest that diffusion across the suberin layer and not metabolism limits morphactin transport across the bark.
Distribution of labelled auxin and derivatives in stem tissues of intact and decapitated broad‐bean plants in relation to apical dominance
Authors: EVERAT‐BOURBOULOUX ANDREE , BONNEMAIN JEAN‐LOUIS
Published: April 2006

[3H]‐auxin (0.13 to 0.18 nmol) was applied to the apical bud of broadbean plants (Vicia faba L. cv. Aguadulce). After 24 h, the exportation from the donor organ was ended. After 48 h, i.e. 10–15 h after the passage of the [3H]‐auxin pulse into the root system, the distribution and the nature of labelled molecules located in the basal part of the stem and in the axillary buds were investigated. Chromatographic analyses concerned both intact plants and plants decapitated 12 h, 24 h or 42 h after the [3H]‐auxin application. In intact plants, there was no significant amount of [3H]‐auxin in the axillary buds, whose radioactivity was very low compared to the stem tissues. The labelled molecules with the Rf of auxin represented 50% or more of the whole radioactivity of the stem tissues. The distribution of [3H]‐auxin was not uniform along the stem. In particular, the cotyledonary node zone, bearing the most inhibited buds, which is known to be an important centre of label retention, contained the highest amounts of labelled auxin both in intact and decapitated plants. The decapitation was quickly followed by a decrease of the [3H]‐auxin amount in the stem base more than 15 cm away from the wound, particularly in the scale leaf nodes, whose axillary buds were mainly the ones to grow after relief from apical dominance. The induction of this early decrease was clearly distinct in plants decapitated when auxin exportation from the donor organ was ended.
Obtention d'épinastie des cotylédons de Sinapis alba en éclairement rouge Iointain continu.
Authors: BAUMGARTNER NICOLE , FONDEVILLE JEAN‐CLAUDE
Published: April 2006

Obtention of epinasty in the cotyledons of Sinapis alba under continuous far‐red illumination. Relation to the development of hypocotyl and cotyledons.

Treatment by far red light induces epinasty of the cotyledonary leaf. The effects of light treatments of different intensities were recorded for hypocotyl length, percentage of epinasty and the cotyledon leaf area. The percentage of epinasty increases as a function of treatment duration and light intensity. As from the second day of treatment a correlation is obtained between the percentage of epinasty and hypocotyl length when the seedlings are given far‐red light treatment of different durations.
Glycolate and glyoxylate stimulation of growth in Lemna gibba
Authors: TILLBERG ELISABETH
Published: April 2006

A 10 to 20% stimulation of growth in Lemna gibba L. G3 occurred following the addition of 0.5 to 3 mM glycolate or glyoxylate, although concentrations of 5 mM or higher were inhibitory. Glyoxylate gave a higher stimulation than glycolate. The stimulating effect on growth was obtained in media with or without 2% added sucrose. A higher stimulation was obtained when the plants were cultivated in open flasks in comparison to cultivation in flasks plugged with cellulose stoppers, which presumably retarded gas exchange.
Regulation of adenosine 5′‐phosphosulfate sulfotransferase by sulfur dioxide in primary leaves of beans (Phaseolus vulgaris)
Authors: WYSS HANS‐RUDOLF , BRUNOLD CHRISTIAN
Published: April 2006

SO2 inhibited the light‐induced increase of extractable adenosine 5′‐phosphosulfate sulfotransferase in greening primary leaves of bean seedlings (Phaseolus vulgaris L. cv. Saxa (Radio) Stamm Vatter). In green primary leaves containing appreciable extractable adenosine 5′‐phosphosulfate sulfotransferase activity, SO2 treatment for 20 h decreased the activity of the enzyme to between 10 and 20% of the initial level. After removal of SO2 from the air, the extractable adenosine 5′‐phosphosulfate sulfotransferase activity increased after a lag, both in green and greening primary leaves, and was back to the control level after about 48 h. The sulfate concentration was increased about fourfold during SO2 treatment. An increase in sulfate sulfur accompanied by a decrease in adenosine 5′‐phosphosulfate sulfotransferase was also observed when bean seedlings, after excision of the roots, were transferred to nutrient solutions containing high sulfate concentrations, suggesting that sulfate is involved in the regulation of the enzyme.
Alterations in membrane transport properties by freezing injury in herbaceous plants:
Authors: PALTA JIWAN P. , LI PAUL H.
Published: April 2006

Leakage of ions from a thawed tissue is a common phenomenon of freezing injury. This leakage is usually assumed to be due to loss of membrane semipermeability or membrane rupture by freezing injury. Freeze injured, yet living, onion (Allium cepa L.) epidermal cells were used to study alterations in cell membranes that result in leakage of ions. In spite of a large efflux of ions, freeze injured cells could be plasmolysed and they remained plasmolysed for several days just like the unfrozen control cells. Injured cells also exhibited protoplasmic streaming.

Passive transport of KCl, urea and methyl urea across the cell membranes of injured and control cells was also studied. No difference could be detected for the transport rates of urea and methyl urea between control and injured cells. However, a dramatic increase in the transport rate of KCl was found for the injured cells.

Depending upon the extent of initial freezing injury, an increase or a decrease in injury symptoms was found in the post‐thaw period. During the progress of freezing injury, 10 days after thawing, a swelling of the protoplasm was seen in the irreversibly injured cells. In spite of this swelling, these cells could be plasmolysed. It appears that the high amount of K+ that leaks out into the extracellular water, due to freezing injury, causes protoplasmic swelling by replacing Ca2+ in the plasma membrane. We conclude that protoplasmic swelling is a sign of secondary injury.

The results presented in this study show that membrane semipermeability is not completely lost and membrane rupture does not occur during the initial stage of freezing injury. In fact, the cells have the ability to repair damage depending upon the degree of injury. Our results show there are specific alterations in membrane semipermeability (e.g., transport of K+) which could be repaired completely depending on the degree of injury. These findings suggest that ion leakage due to freezing injury is due to alteration in the membrane proteins and not in the membrane lipids.
Kinetic characterization of barley root plasma membrane‐bound Ca2+‐ and Mg2+‐dependent adenosine triphosphatase activities
Authors: CALDWELL CHARLES R. , HAUG ALFRED
Published: April 2006

A plasma membrane‐rich microsome fraction isolated from barley (Hordeum vulgare L. cv. Conquest) roots contained considerable divalent cation‐dependent ATPase activity when assayed at 16°C. The maximal divalent cation‐stimulation of the apparent basal ATPase activity varied as Ca2+ > Mg2+ > Mn2+= Zn2+ > Co2+ > Ni2+, with all other divalent cations tested being inhibitory. Double reciprocal plots of the Ca2+‐ and Mg2+‐dependent ATPase velocities as a function of substance concentration were nonlinear, suggesting the presence of multiple catalytic sites. Both MgATP2‐ and CaATP2‐ served as the true substrates and apparently bind to the same catalytic sites. Free ATP and Ca2+ could inhibitit the Ca2+‐ and Mg2+‐dependent ATPase. Increasing free Mg2+ levels enhanced the affinity of the Mg2+‐dependent ATPase for MgATP2‐, while slightly inhibiting the Vmax values. Other divalent cation‐nucleoside triphosphate complexes produced maximal enzyme velocities equal to or greater than those generated by CaATP2‐ and MgATP2‐. However, the ATPase had significantly higher affinities for CaATP2‐ and MgATP2‐, than for the alternative substrates. The high and low affinity components of the Ca2+‐ and Mg2+‐dependent ATPase exhibited optimal Vmax values at pH 5 and 6, respectively. Analysis of the pH‐dependence of the enzyme Km values indicated enzyme‐substrate binding with charge neutralization at neutral and alkaline pH's. Nonlinear double reciprocal plots were obtained at all assay temperatures. However, the complexity of the enzyme kinetics became less apparent at the higher assay temperatures. The kinetics of the barley root divalent cation‐dependent ATPase activities are discussed in terms of the kinetics of ATPases from other plants and the methods used to obtain them, and compared to the kinetics of ion transport ATPases from animal membranes.
Phytochrome mediated induction of nitrate reductase activity in etiolated maize leaves
Authors: RAO L. VIJAYA MOHAN , DATTA NEERAJ , SOPORY SUDHIR K. , GUHA‐MUKHERJEE SIPRA
Published: April 2006

The effects of red and far‐red light on the enhancement of in vitro nitrate reductase activity and on nitrate accumulation in etiolated excised maize leaves were examined. Illumination for 5 min with red light followed by a 4‐h dark period caused a marked increase in nitrate reductase activity, whereas a 5‐min illumination with far‐red light had no effect on the enzyme activity. The effect of red light was completely reversed by a subsequent illumination with the same period of far‐red light. Continuous far‐red light also enhanced nitrate reductase activity. Both photoreversibility by red and far‐red light and the operation of high intensity reaction under continuous far‐red light indicated that the induction of nitrate reductase was mediated by phytochrome. Though nitrate accumulation was slightly enhanced by red and continuous far‐red light treatments by 17% and 26% respectively, this is unlikely to account for the entire increase of nitrate reductase activity. The far‐red light treatments given in water, to leaves preincubated in nitrate, enhanced nitrate reductase activity considerably over the dark control.

The presence of a lag phase and inhibition of increase in enzyme activity under continuous far‐red light‐by tungstate and inhibitors of RNA synthesis and protein synthesis‐rules out the possibility of activation of nitrate reductase and suggests de novo synthesis of the enzyme affected by phytochrome.
Effects of caffeine on germination and differentiation in spores of the fern, Onoclea sensibilis
Authors: MILLER JOHN H. , BASSEL ALIX R.
Published: April 2006

During spore germination in the fern, Onoclea sensibilis L., the nucleus moves from a central position to one end, and an asymmetrical cell division partitions the spore into two cells of greatly unequal size. The smaller cell differentiates directly into a rhizoid, whereas the larger cell and its derivatives give rise to the prothallus. In the presence of 5 mM caffeine, the nuclei of most of the spores undergo mitotic replication, whereas cell wall formation is blocked. Multinucleate single cells are produced, which are capable of growth, but no rhizoid differentiation occurs. In some cases a partial cell wall is produced, but the nucleus moves through the discontinuity back to the center of the spore, and the enucleate, incompletely partitioned small “cell” fails to differentiate into a rhizoid. In less than 1% of the spores a broad protuberance, whose wall is yellow‐brown, is formed in a multinucleate single cell. The color, staining reaction to ruthenium red, and ultrastructural appearance of the protuberance resemble that of the rhizoid wall. It appears that infrequently in the caffeine‐treated spores, a feature which is characteristic of rhizoids is expressed, in the absence of asymmetric cell division, in a cell which otherwise is unable to produce a rhizoid. The results are interpreted to mean that the spore has a highly localized, persistent differentiated region. For rhizoid differentiation to occur, a nucleus must be confined in that region – a confinement which normally is accomplished by the geometrically asymmetric first cell division of germination.
Seasonal changes of the different components of the inhibitor β complex in potato tubers
Authors: FRANKLIN JEEVALATHA , HEMBERG TORSTEN
Published: April 2006

Seasonal changes of the inhibiting substances in the inhibitor β complex were studied in diethyl ether and methanol extracts of peelings from potato tubers, cv. Majestic, prepared during dormancy and cessation of dormancy. In both extracts the acidic ether soluble substances were investigated. From the methanol extracts also non‐ether soluble but butanol soluble substances were studied. At each extraction time experiments were performed to determine the stage of rest in the tubers.

Four different inhibitory zones were found with the Avena straight growth test of thin layer chromatograms. One of these was probably an artefact formed during chromatography. The level of all these substances decreased when rest ceased. – Thin layer chromatograms of the butanol fraction of methanol extracts, which should have contained the bound forms of the inhibitors, showed the same inhibitory zones as the ether fractions. This probably resulted from hydrolysis of the bound inhibitors when the extracts were chromatographed in an alkaline solvent system during purification.
Isolation of active ribulose 1,5‐bisphosphate carboxylase from glanded cotton (G. hirsutum)
Authors: QUAYLE THOMAS J. , KATTERMAN FRANK R. , JENSEN RICHARD G.
Published: April 2006

Ribulose, 1,5‐bisphosphate carboxylase has been isolated from leaves of glanded cotton, (Gossypium hirsutum L. cv. TM1), by techniques described. A yield exceeding 4.5 mg enzyme per gram leaf tissue has been obtained by utilizing a sodium homogenizing buffer without the addition of any reducing agent. Sodium dodecylsulfate gel electrophoresis of the enzyme shows the fraction to be relatively free of contaminants. Enzymic assays of the isolate give a specific activity of 1.1 μmol CO2 fixed (min‐mg protein)−1 at 30°C.
Action de la proline exogène sur l'activité de la voie du glycolate chez Nicotiana tabacum cv. Xanthi n.c.
Authors: VALLEE J. C. , VANSUYT G. , PREVOST J.
Published: April 2006

The effect of exogenous proline on the activity of the glycolate pathway in Nicotiana tabacum cv. Xanthi n.c.

An exogenous proline supply in the light provokes an increase in free glycine concentration in apical tissues or in leaf disks of vegetative Nicotiana tabacum L. cv. Xanthi n.c. This does not occur in the equivalent tissues of tobacco plants after floral induction, these being naturally rich in proline. In vegetative tobacco, we have tried to determine this specific action of exogenous proline. With 14C glycine, 14CO2 experiments (Pulse‐chase) and glycine decarboxylase activity determinations, we observed that glycine‐serine transformation was inhibited by proline supply. Presently it is important to determine if endogenous proline acts on the same reaction.
Cell wall polysaccharidase activities and growth processes: a possible relationship
Authors: GOLDBERG RENEE
Published: April 2006

In Vigna radiata (L.) Wilczeck hypocotyl, the maximal growth zone is located right under the hook and moves 5 mm lowe exogenous auxin. A good correlation has been obtained between the magnitude of the growth response and the cell wall β 1→3 endoglucanase activities. In cell walls from segments with different growth potentials, the kinetic constants of the β 1→3 endoglucanases are not identical. When the enzymes are rendered soluble, their behaviors become almost similar. These data indicate a relationship between the kinetic behavior of the immobilized enzymes and the structure of their support, i.e. the cell wall organization, which is modified during cell elongation. The possible involvements of these enzymes in some pathways of growth processes are discussed.
Extraction of tracheal sap from Citrus and analysis of its nitrogenous compounds
Authors: MORENO JOAQUIN , GARCÍA‐MARTINEZ JOSÉ L.
Published: April 2006

Tracheal sap was extracted from sections of stems (0.5 to 1.5 cm in diameter and 7.5 to 15.0 cm in length) of orange trees (Citrus sinensis (L.) Osbeck cv. Washington Navel) by using a combination of the vacuum and liquid displacement methods. The volume of sap obtained and its concentration of nitrogenous compounds were dependent on the volume of displacing liquid used for the extraction. Four ml of water‐saturated 1‐butanol extracted essentially all of the xylem fluid present in the stem sections without apparent production of artifacts.

The time of sampling affected the nitrogen concentration of the tracheal sap, but not the content of xylem nitrogen per volume of stem material. The orientation of the stems in the tree and the diameter of the stems had an effect on their contents of xylem nitrogen, with southeastern orientation and thinner stems showing higher concentrations.

We could not detect the presence of ammonium, nitrites or proteins in the tracheal sap of orange trees. Most of the nitrogen was present as amino acids and about 2% of the total in the form of nitrates. The qualitative composition of amino acids, as determined by TLC, was the same both in winter and spring tracheal sap. The main components of the sap were proline and arginine in winter, and these amino acids together with asparagine and aspartic acid in spring.
Efficiency and regulation of root respiration in a legume: Effects of the N source
Authors: LAMBERS HANS , LAYZELL DAVID B. , PATE JOHN S.
Published: April 2006

A comparison was made of energy metabolism of nodulated N2 fixing plants and non‐nodulated NO3‐fed plants of Lupinus albus L. Growth, N‐increment, root respiration (O2 uptake and CO2 production) and the contribution of a SHAM‐sensitive oxidative pathway (the alternative pathway) in root respiration were measured. Both growth rate and the rate of N‐increment were the same in both series of plants. The rate of root respiration, both O2 uptake and CO2 production, and the activity of the SHAM‐sensitive pathway were higher in NO3‐fed plants than in N2 fixing plants. The rate of ATP production in oxidative phosphorylation was computed also to be higher in NO3‐fed plants. It is concluded that both carbohydrate costings and ATP costings for synthesis + maintenance of root material were lower in N2 fixing than in NO3‐fed plants.

The respiratory quotient of root respiration was 1.6 in N2‐fixing plants and 1.4 in NO3‐fed plants. These values were slightly higher than the values calculated on the basis of CO2 output due to N‐assimilation and the experimental values of O2 uptake, but showed the same trend: highest in N2 fixing plants.

Root respiration of NO3‐fed plants showed a diurnal pattern (both O2 uptake, CO2 production and the activity of the SHAM‐sensitive pathway), whilst no diurnal variation in root respiration was found in N2 fixing plants. However, C2H2 reduction did show a diurnal rhythm, which is suggested to be related to the diurnal variation in transpiration.

Addition of NO3 to N2 fixing plants increased the rate of root respiration and the activity of the alternative pathway. This treatment did not decrease C2H2 reduction and H2 evolution within 4 days.

Withdrawal of NO3‐supply from NO3‐fed plants decreased the rate of root respiration but had no effect on the relative activity of the alternative pathway.

It is suggested that the higher rate of root respiration and the higher activity of the SHAM‐sensitive pathway in NO3‐fed plants is due to a larger supply of carbohydrates to the roots, partly due to a better photosynthetic performance of the shoots and partly due to a higher capacity of the roots to attract carbohydrates.
Transcription products associated with developing pea chloroplast membranes
Authors: STUMMANN BJARNE M. , KAUFMANN UWE , HENNINGSEN KNUD W.
Published: April 2006

RNA fractions from leaves of pea (Pisum sativum L.) were labelled by placing dark‐grown shoots in 32P‐phosphate for 1 h in darkness and 3 h in light. Membrane‐associated RNA and soluble RNA was isolated from an organelle fraction containing plastids and mitochondria. A cytoplasmic RNA fraction was also isolated. These RNA fractions were hybridized to nuclear, chloroplast or mitochondrial DNA isolated from fully green leaves. The organelle RNA fractions hybridized significantly only to chloroplast DNA. This result suggests that at early stages of greening, light initiates transcription of part of the chloroplast DNA. Some of the newly transcribed RNA species are associated with the developing plastid membranes.
Substrate‐dependent modulation of ATPase activity by Na+ and K+ in roots of Plantago species
Authors: ERDEI LÁSZLÓ , KUIPER PIETER J. C.
Published: April 2006

The separate and combined effects of Na+ and K+ on ATPase activity of microsomal fractions from the roots of the halophytic Plantago maritima and the less salt‐tolerant Plantago coronopus were investigated in the presence of Mg+ATP or Ca+ATP (at equimolar ratios) as substrate. The ATPase activity in the presence of Mg+ATP was stimulated by Na+ and by K+ when they were added separately, but their combination reduced the enzyme activity. In the presence of Ca+ATP, however, the enzyme activity was stimulated by the combined addition of Na++ K+ as well, and their action was qualitatively additive, but experimentally lower. The two complexes as substrate probably served as allosteric effectors and induced different types of enzyme responses to monovalent cations.

The Na+‐stimulation and K+‐stimulation of the ATPase activity could be separated by growing the plants under saline conditions. The Na+‐stimulation of the ATPase was lowered while the K+‐stimulation remained unchanged. The corresponding Na+ influx of the roots could also be blocked without influencing K+ influx of the roots. This kind of separation of ion fluxes and ATPases presumes a transport system model which possesses several units and which is accessible for regulation by hormones, lipids and divalent cations.
Influence of the excision of cotyledons on the content of indole‐3‐acetic acid, growth and flowering of Lupinus albus plants
Authors: ELKINAWY MAHASEN
Published: April 2006

Excision of both cotyledons of Lupinus albus L. (L. termis Forssk.) seedlings at different morphological stages during the first 8 days after sowing, retarded significantly the growth of 16‐day‐old seedlings and decreased the content of IAA in the shoots. The effect was more obvious at the early excision (4 days after sowing). A pattern similar to that of control plants with intact cotyledons was attained when cotyledons were excised later than 8 days after sowing. It is believed that the cotyledons control the IAA content of the shoot during the early stages of development. At day 36 flower primordia were observed in controls but not in cotyledon‐less plants. At this time the IAA content of the shoot apices and the growth of cotyledon‐less plants were the same as in controls except for plants that lost cotyledons 4 days after sowing, which showed similar values at week 11, but did not produce flower primordia. The other cotyledon‐less plants produced flower primordia 4–11 days after controls. It is postulated that the cotyledons convey certain factor(s) to the developing axis at an early stage of the development which promote flowering.
Effect of vitamins on sprouting of purple nutsedge tubers
Authors: HUSAIN S. M. , AL‐ALI FAIZA AZIZ , SHAMSI S. R. A.
Published: April 2006

Vitamins of the B group and vitamin C were applied to purple nutsedge (Cyperus rotundus L.) tubers to study their effect on the sprouting rate, initiation and establishment of sprouts, growth of plantlets and development of orthotropic rhizomes in comparison with the corresponding effects of kinetin. Ascorbic acid up to 100 mg I−1 hastened sprouting, whereas vitamins of the B group and kinetin retarded sprouting; 100% tubers sprouted in all treatments within 10 days.

Unlike kinetin, none of the vitamins resulted in the establishment of more than one sprout per tuber. Riboflavin and pyridoxine promoted root and shoot growth of the plantlets, whereas kinetin produced short, thick shoots and inhibited root growth, with increasing concentration.

Ascorbic acid was only second to kinetin in the induction of orthotropic rhizomes, but the former resulted in an increase in rhizome length.
Ethylene evolution from various developing organs of olive (Olea europaea) after excision
Authors: Lavee S. , Martin G. C.
Published: April 2006

Ethylene evolution from leaves, stems, inflorescences and fruits of the olive plant (Olea europaea L.) cv. Manzanillo was studied at various stages of their development. Mature non‐growing organs, particularly leaves, have a constant, low, and uniform rate of ethylene evolution. Ethylene evolution from detached mature olive leaves was constant during the first 12 h after excision. Leaves on shoots maintained in vitro kept a constant rate of ethylene evolution for at least the first 5–6 days. Leaf injury significantly increased ethylene evolution. Ethylene evolution from injured and non‐injured control leaves could be markedly inhibited aminoethoxyvinylglycine (AVG) applied to the leaves or fed to the shoot. The use of excised olive shoots and leaves as an in vitro model system for studies of induced metabolic processes such as abscission and developing water stress was suggested.
Stem pithiness in tomato plants: The effect of water stress and the role of abscisic acid
Authors: Aloni Beny , Pressman Etan
Published: April 2006

The pith parenchyma in tomato (Lycopersicum esculentum) stems was found to be disrupted in response to water stress (stem pithiness). The process of the degradation starts at the upper part of the stem and proceeds downwards as the stress is prolonged. The damage to the stem tissue was found to be irreversible upon rehydration of the stressed plants. Scanning electron microscopy revealed that the protoplast of the affected cells is disrupted first, followed by degradation of the cell wall.

Application of abscisic acid (ABA) induced pithiness in non‐stressed plants and also enhanced the effect of a short period of dehydration. Kinetin, although causing severe wilting, did not induce pithiness. However, when given after a short period of water stress or within the period of stress, kinetin enhanced pithiness development.

In the course of the stress, ABA levels in the upper part of the stem and in the young leaves were higher than the levels found in the lower parts of the plant shoot. The increase in ABA levels was detected before any sign of pithiness.

It is suggested that ABA might be the triggering agent of the cellular degradation process initiated by water stress.
Formation of photosynthetic pigments and quinones and development of photosynthetic activity in barley etioplasts during greening in intermittent and continuous white light
Authors: Grumbach Karl H.
Published: April 2006

The appearance and development of photosynthetic activity, and the accumulation of chlorophylls, carotenoids and quinones, was investigated in etiolated barley shoots (Hordeum vulgare L. cv. Villa) during greening in flash light, periodic light‐dark cycles, and continuous white light. Greening and the development of photosynthetic activity was delayed in flash and periodic light compared to continuous white light. Photosystem II activity occurred after 6 light‐dark cycles and increased continuously during greening. After 3 h greening in continuous white light, photosystem II activity appeared with a very high rate and decreased to that of a green leaf after 50 h greening. Parallel to the development of photosynthetic activity, light stimulated the biosynthesis of prenyllipids. Moreover, chlorophylls and those carotenoids and quinones that are contained in etioplasts in relatively small amounts, were particularly enhanced in their biosynthesis. Chlorophyll a was synthesized without a lag phase during greening in flash light, whereas a 2 h lag phase occurred in continuous white light. In all three modes of illumination the formation of chlorophyll a exceeded that of chlorophyll b. After 4 flashes and 2 light‐dark cycles, chlorophyll b could be detected with a very high initial a/b ratio. Higher chlorophyll a/b ratios were reached after 200 flashes (a/b=10.9) and 50 light‐dark cycles (a/b=6.6) than after 50 h continuous white light (a/b=3.3). The formation of carotenes, lutein, violaxanthin and neoxanthin was also enhanced by light. This was also confirmed for plast‐ouinone‐9. ş‐tocopherol,α‐tocoquinone and phylloquinone. A comparison of the carotenoid and quinone composition of the differentiating thylakoid membrane before and after onset of photosynthesis, reveals that the photosynthetic membrane is already equipped with photosynthetic pigments and quinones before the appearance of photosystem II activity. It is concluded that during development of the photo‐synthetic apparatus the thylakoid membrane with its structural and functional constituents is formed first. In a second and slower process the water splitting enzyme system and enzymes of the Calvin cycle are activated.
Interactions between osmoregulation and the alternative respiratory pathway in Plantago coronopus as affected by salinity
Authors: Lambers Hans , Blacquière Tjeerd , Stuiver Bep (C. E. E.)
Published: April 2006

Plantago coronopus L., a species from the coastal zone, was grown in culture solution with and without 50 mM NaCl. In addition it was transferred from a non‐saline solution to a solution containing 50 mM NaCl. Short term effects of NaCl on growth and various aspects of energy metabolism, including photosynthesis, shoot dark respiration, root respiration and the contribution of the SHAM‐sensitive alternative pathway to root respiration were investigated. The concentrations of soluble and insoluble non‐structural carbohydrates and of sorbitol a compatible osmotic solute in Plantago, in both shoots and roots were also determined.

Growth of shoots and roots was largely unaffected by addition of 50 mM NaCl. Net photosynthesis, shoot dark respiration and the concentration of non‐structural carbohydrates in both shoots and roots were also unaffected by salinity. The rate of root respiration immediately decreased upon addition of 50 mM NaCl. This decrease was almost exclusively attributed to a decreased activity of the SHAM‐sensitive alternative pathway. The concentration of sorbitol in the roots increased quickly after addition of 50 mM NaCl, whilst the increase in sorbitol concentration in the shoots started later. The time course of the increase of sorbitol concentration was similar to that of the decrease in activity of the alternative pathway. During the first 12 h after exposure to 50 mM NaCl, the amount of carbohydrates which was saved in respiration, due to the decreased activity of the alternative pathway, was the same as that used for sorbitol synthesis in the roots. It is concluded that the activity of the alternative pathway decreased due to increased utilization of carbohydrates for sorbitol synthesis, according to a proposed ‘energy overflow model’.

After 24 h, the sorbitol concentration in the cytoplasm of the root cells of plants transferred to a saline solution reached a level that was sufficient to compensate for 50 mM NaCl, assuming a cytoplasmic volume of ca. 10% of the total cell volume. The sorbitol concentration in roots of plants grown in a saline environment for several weeks was lower than that in roots of plants transferred to a saline environment for c. 24 h. It is suggested that sorbitol accumulated in roots of Plantago coronopus as an immediate reaction upon salinity, whilst other adaptations may occur thereafter.
Energy metabolism of Plantago lanceolata as dependent on the supply of mineral nutrients
Authors: Lambers Hans , Posthumus Freek , Stulen Ineke , Lanting Lineke , van de Dijk Siebren J. , Hofstra Rinie
Published: April 2006

Plantago lanceolataL., a grassland species from a relatively nutrient‐poor habitat, was grown in nutrient‐rich and in nutrient‐poor culture solutions. Half of the plants were trensferred from high to low or from low to high nutrient conditions. Shoot growth was immediately reduced upon transfer to low nutrient conditions, whilst it reacted more slowly upon transfer of plants to high nutrient conditions. Root growth was less dependent on the supply of nutrients, but it was slightly reduced upon transfer of plants to high nutrient conditions.

Photosynthesis was largely independent of the nutrient supply, apart from an initial increase upon transfer of plants to low nutrient conditions. Photosynthesis decreased with age in all treatments, and this decrease was not due to mutual shading. The decrease of photosynthetic rate was not accompanied by a decreased relative growth rate: it was compensated by a more efficient root respiration, since the activity of the alternative nonphosphorylating pathway continuously decreased in plants grown in a high nutrient environment.

It is concluded that the alternative pathway was of significance in removal of carbohydrates, which could not be utilized for growth, energy production,etc., due to a temporary or structural imbalance between assimilate production and requirement. The alternative pathway also appeared to allowP. lanceolataplants to adapt to a changed environment as regards mineral nutrition.

The experimental value for root growth respiration ofP. lanceolatagrown under high nutrient conditions was compared with a theoretical value, calculated from the biochemical composition of plant dry matter and the known energy costings for biosynthetic and transport processes. A good correlation between the experimental and theoretical value of root growth respiration was found if it was assumed that ion uptake requiredc. 1.0 molecule of ATP per ion per membrane passage.
Action of bicarbonate and Photosystem 2 inhibiting herbicides on electron transport in pea grana and in thylakoids of a blue‐green alga
Authors: van Rensen Jack J. S. , Vermaas Wim F. J.
Published: April 2006

Bicarbonate (or carbon dioxide) is required for electron transport in isolated broken pea chloroplasts. The site of action of the bicarbonate ion is between the primary electron acceptor of Photosystem 2, Q, and the plastoquinone pool. After trypsin treatment the Hill reaction with ferricyanide does not require bicarbonate. Photosystem 2 inhibiting herbicides act also at this site. Therefore, a possible interaction of bicarbonate and these herbicides in their effect on photosynthetic electron transport was studied.

The reciprocal of the Hill reaction rate in CO2‐depleted chloroplasts was plotted against the reciprocal of added bicarbonate concentration in the absence and in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), 2‐methoxy‐4,6‐bis (ethylamino)‐1,3,5‐triazine (simeton) or 4,6‐dinitro‐o‐cresol (DNOC). From these Lineweaver‐Burk plots we concluded that DCMU and simeton inhibit both bicarbonate binding and Vmax. There is a purely competitive inhibition of bicarbonate binding by DNOC. We suggest that DNOC may exert its inhibition of electron transport by removing bicarbonate from its binding site.

In isolated thylakoid membranes of Synechococcus leopoliensis we did not find a bicarbonate effect nor inhibition by DNOC after Q, indicating that in the thylakoids of this blue‐green alga the binding site for bicarbonate and DNOC between Q and plastoquinone is absent.
Coleoptile growth‐inducing capacities of exo‐β‐(1→3)‐glucanases from fungi
Authors: Yamamoto Ryoichi , Nevins Donald J.
Published: April 2006

An exo‐β‐(1β3)‐glucanase derived from Selerotinia libertiana induced growth of Avena sativa coleoptiles and degraded hemicelluloses and β‐(1→4):(1→3) mixed linked glucan. However, neither endo‐β‐(1→4)‐ nor endo‐β‐(1→3)‐glucanase activity could be detected in the enzyme preparation. Nojirimycin inhibited the glucan degradation caused by the enzyme but glucono‐1,5‐lactone did not. Another exo‐β‐(1→3)‐glucanase derived from Basidiomycete QM 806 did not induce coleoptile growth and did not degrade the glucan. Growth‐inducing properties of exo‐β‐(1→3)‐glucanases are discussed.
Phloem differentiation in Coleus pith explants
Authors: Comer Alan E. , Leonardo Lois
Published: April 2006

A simple tissue culture protocol was used to examine phloem differentiation. Sieve tube elements differentiated from Coleus blumei Benth. pith parenchyma when pith blocks were explanted on to an agar medium containing sucrose and indole acetic acid. Growth regulator concentration had surprisingly little influence on the production of phloem cells. Increasing the availability of sucrose, however, resulted in an enhancement of phloem differentiation. Evidently phloem and xylem differentiation began at the same time in this system, and the concentration of sucrose determined the relative production of phloem cells.
Prevention of imbibitional injury in low vigor soybean embryonic axes by osmotic control of water uptake
Authors: Woodstock Lowell W. , Tao Kar‐Ling James
Published: April 2006

Deterioration of soybean [Glycine max (L.) Merr. cv. Essex] seeds during accelerated aging at 41°C and 100% relative humidity predisposes the embryonic axis to injury during the initial period of imbibition. This injury was prevented or greatly reduced in severity when excised axes were imbibed on blotters containing 30% polyethylene glycol which slowed the rate of water uptake and when axes were pre‐equilibrated to a high moisture level. Rates of water uptake by “high”(no treatment) and “low vigor”(accelerated aged) excised axes were identical. However, high vigor axes tolerated rapid water uptake during early imbition, whereas low vigor axes did not. Leakage of electrolytes during early imbibition was nearly six times greater in low than in high vigor axes. Polyethylene glycol significantly reduced the leakage of electrolytes from both low and high vigor axes. The data are in agreement with the hypothesis that seed deterioration in soybeans involves membrane changes which may predispose embryonic tissues to injury during imbibition. Reduction of the rate of water uptake during the initial period of imbibition would allow extra time for membrane repair or rearrangement, thus permitting the tissues to develop in a more orderly manner. The data indicate that deterioration in soybean seeds involves, at least in part, a decrease in ability of seed axes to tolerate rapid water uptake at the start of imbibition and that this weakness may be compensated by osmotic control of water uptake.
Some physiological responses of cotton leaves to foliar applications of potassium 3,4‐dichloroisothiazole‐5‐carboxylate and S,S,S‐tributyl phosphorotrithioate
Authors: Cathey G. W. , Elmore C. D. , McMichael B. L.
Published: April 2006

The effects of foliar application of potassium 3,4‐dichloroisothiazole‐5‐carboxylate (TD‐1123) and S,S,S‐tributyl phosphorotrithioate (DEF) on some physiological events that occur in cotton (Gossypium hirsutum L.) leaves are reported. Transport of 14C from cotton leaves was significantly reduced as soon as 1 day after treatment with DEF. In addition the DEF‐treated leaves exhibited reductions in water potential recovery values (predawn measurements), stomatal conductance, specific weights, soluble N content, and an alteration in free amino acid distribution. Little change in any of these parameters was noted in leaves treated with TD‐1123 alone. A sequential treatment of TD‐1123 followed in 10 days with DEF had an apparent synergistic effect in that the effect on most parameters measured was more pronounced and occurred earlier in such leaves than in those treated with either chemical alone.