bluuebunny/crossref_metadata_2025 huggingface dataset:
Light‐induced linear dichroism in photoreversibly photochromic sensor pigments. – V. Reinterpretation of the experiments on in vivo action dichroism of phytochrome
Authors: Björn Lars Olof
Published: April 2006

Experiments by several authors on the effects of polarized light on phytochromemediated responses in fern gametophytes and in the green alga Mougeotia have earlier been interpreted as showing that the transition moment of phytochrome in the Pr form is parallel to the plasmalemma, but perpendicular to the plasmalemma for the Pfr form of phytochrome. It is now shown that the experimental results can be interpreted differently, and that they are also consistent with a chromophore rotation of about 30° (instead of 90°), as found for immobilized phytochrome molecules in vitro. Thus there is no evidence for a rotation of the whole phytochrome protein. For the gametophyte of Adiantum it is calculated that the Pr transition moment is inclined 17° to the plasmalemma, and the Pfr transition moment ca 50°, corresponding to an in vivo chromophore rotation of ca 33°; however, these values are very approximate.
Impaired chlorophyll formation in etiolated cucumber cotyledons following prolonged dark incubation after red light pretreatment
Authors: Cohen Lila , Arzee Tova
Published: April 2006

Red light (R) pretreatment of etiolated cucumber seedlings (Cucumis sativus L. var. Elem) followed by prolonged dark incubation prior to white light (WL) exposure, had an adverse effect on the greening of the cotyledons. The effect was photoreversible by far‐red (FR) light. Cotyledons which were dark incubated for 24 h following the R pulse greened more rapidly when exposed to WL than did the controls, while total chlorophyll (Chl) accumulation after 24 h in the light was about the same in both. However, after 48 h post‐R dark incubation greening of the treated cotyledons was delayed, and their amount of Chl which accumulated after 24 h WL was about one half of that in non‐treated seedlings. As the length of the post‐R dark incubation period was extended Chl production became slower, so that after 96 h post‐R dark incubation the Chl level in the treated cotyledons after 24 h WL was approximately 20% of the controls. No significant differences in amounts of protochlorophyll could be detected between seedlings preilluminated with R or R followed by FR. Seedlings 4‐, 5‐ and 6‐days‐old at the time of R treatment showed similar degrees of impaired Chl synthesis following prolonged post‐R dark incubation.
Low temperature spectroscopy of phytochrome: Pr, Pfr and intermediates
Authors: Rüdiger W. , Thümmler F.
Published: April 2006

Phytochrome (120 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa, München). Low temperature spectra between −17°C and −160°C are recorded for Pr, Pfr, and irradiated phytochrome samples. The temperature‐dependence of the Pr and Pfr absorption spectra is described. Difference spectra of such temperature effects can erroneously be interpreted as difference spectra of intermediates. Probable absorption spectra of intermediates are calculated from the spectra of irradiated Pr or Pfr, respectively. The calculated spectral data are compared with published data on phytochrome intermediates.
Phytochrome‐mediated accumulation of free amino acids in radicles of germinating watermelon seeds
Authors: Thanos Costas A.
Published: April 2006

The total free amino acid pools in radicles of watermelon seeds, investigated during imbibition of water at 25°C, were higher under the most (darkness) than under the least (continuous broad spectrum far‐red light) favourable light regime for germination. When seeds were imbibed in an appropriate osmotic solution of PEG‐6000 (fully suppressing germination), in darkness or under continuous red or far‐red light, the biochemical analyses of the radicles after 1,2,3 and 4 days from the onset of imbibition show that while the total soluble sugar content remains rather constant in all treatments, significant changes are observed in the total free amino acid pools. After the first day, a considerable increase characterizes the “darkness” pool in contrast to a moderate one under red, while the “far‐red” pool remains constant. Ultimately, at 4 days, the three pools are 190,142 and 123% of the 0 day radicle one. The qualitative free amino acid determination of the 4 day darkness and far‐red pools shows a considerably increased percentage contribution of glutamic acid, arginine and citrulline in the “darkness” pool. The free amino acid increase in non‐illuminated radicles may be correlated to germinability; moreover, it is evidently a phytochrome‐mediated, pre‐germinatory event, probably due to the hydrolysis of proteins (known to be rich in glutamic acid and arginine), stored in the radicle.
The perception of dusk signals in photoperiodic time‐measurement
Authors: Lumsden Peter J. , Vince‐Prue Daphne
Published: April 2006

A critical duration of darkness must be exceeded for the photoperiodic induction of flowering in short‐day plants. This requires detection of the light/dark transition at dusk and the coupling of this information to a time‐measuring system.

Lowering the Pfr/Ptot, ratio photochemically at the end of the day did not accelerate the onset of dark timing in Pharbitis nil Choisy cv. Violet. Time‐measurement was initiated when, with no change in spectral quality, the irradiance fell below a threshold value. Thus, if the light/dark transition at dusk is sensed by a reduction in Pfr, this reduction can be achieved as rapidly through thermal reactions as through photochemical ones. When given at hourly intervals during a 6‐h extension of a 24‐h main light period in white light, pulses of red light were as effective as continuous red light in delaying the onset of timing; pulses every 2 or 3 h were less effective. The effectiveness of intermittent red light indicates that phytochrome is the photoreceptor and the requirement for frequent exposures suggests that Pfr is lost rapidly in the dark. However, the red light pulses could not be reversed by far‐red light, which argues against this hypothesis. An alternative explanation is that the perception of light as being continuous occurs only when “new” Pfr is regenerated sufficiently frequently.

The nature of the coupling of the dusk signal to the time‐measuring system is discussed and it is suggested that the effect of each red light pulse is to delay the phase of the photoperiodic rhythm by 1–3 h.
Control of root and shoot‐bud formation from potato tuber tissue cultured in vitro
Authors: Kikuta Yoshio , Okazawa Yozo
Published: April 2006

Comparative studies on the control of root and shoot‐bud formation and plant regeneration have been undertaken in discs (1 × 6 mm in diameter) excised from tubers of potato (Solanum tuberosum L. cv. Irish Cobbler) cultured in vitro. The results clarified that the optimal culture conditions for shoot‐bud formation were quite different from those for root formation and, in conclusion, that (1) shoot‐buds were produced when cultured in modified White's medium containing 0.25 M mannitol with 2.3 μM zeatin and 0.57 μM indole‐3‐acetic acid (IAA) at 20°C under relatively high light irradiation, while (2) roots were readily formed when cultured in modified White's medium containing 29 mM sucrose with 4.7 μM kinetin plus 1.7 μM IAA at 30°C in darkness.
Degradation of pectic polysaccharides extracted from suspension cultures of carrot by purified exo‐polygalacturonase
Authors: Konno Haruyoshi , Yamasaki Yoshiki , Katoh Kenji
Published: April 2006

Highly purified exo‐polygalacturonase was obtained from suspension cultures of carrot (Daucus carota L. cv. Kintoki) by dialysis at pH 5.2, chromatography on DEAE‐Sephadex A‐50 and on Sephadex G‐150, and preparative polyacrylamide disc gel electrophoresis. The enzyme did not attack the isolated carrot cell walls directly, but it had some effect on pectic polysaccharides extracted from the walls. The extracted polysaccharides were fractionated by DEAE‐Sephadex A‐50 column chromatography yielding four carbohydrate fractions. The major fraction (P‐3) was then reacted with the exo‐polygalacturonase. The enzyme treatment resulted in hydrolysis of approximately 18% of the glycosyl linkages of fraction P‐3 with the release of galacturonic acids. The molecular size estimated by Bio‐Gel A‐5m gel filtration was not markedly affected by the enzyme action, but the percentage of galacturonosyl residues was clearly reduced. The specific activity of exo‐polygalacturonase changed during the growth cycle, in relation to the cell growth.
Relationships between auxin‐ and acid‐induced growth in Vigna radiata hypocotyl segments
Authors: Prat Roger , Goldberg Renee
Published: April 2006

The H+‐ and IAA‐induced growth responses of isolated Vigna radiata (L.) Wilczek hypocotyl segments were investigated concurrently with IAA‐induced H+ excretion. The effects of external pH on these reactions were also studied. Experiments were performed with intact, peeled and abraded segments. Only abraded segments reacted to H+ and to IAA. In short‐term experiments, the cuticle prevented proton efflux and influx; however, it allowed gradual ion movements which become measurable after 1 h. Both phases of the IAA growth response reacted to external pH. The interactions between these two phases and their pH dependencies are discussed.
Tensile characteristics of collenchyma cell walls at different calcium contents
Authors: Jarvis M. C. , Logan A. S. , Duncan H. J.
Published: April 2006

Collenchyma fibres from celery (Apium graveolensL.) were extracted with detergent and phenol‐acetic acid‐water to leave the intact cell walls, free from active enzymes. Under a small, constant stress the cell wall fibres showed elastic and plastic extension and viscoelastic deformation, but viscous flow was observed only at high stresses close to the breaking stress. After complete removal of calcium ions with cyclohex‐anediamine tetraacetic acid (CDTA) and incubation for 18 h, comparable levels of these extensibility components were observed at much lower stresses. However, partial removal of calcium ions with citrate did not increase the plastic, elastic or viscoelastic components even when the residual calcium was reduced to 3.5% of the exchange capacity. The breaking stress of the fibres was rather more sensitive to calcium removal, being reduced by 50% at 7% calcium saturation. CDTA‐extracted fibres broke by cell separation at very low stress. These characteristics did not appear compatible with removal of calcium ions, or their displacement by protons, as a mechanism for auxin‐induced growth in this material: however such mechanisms are not excluded in other tissues or under other conditions. Strong chelating agents which remove enough calcium to weaken cell walls should be avoided in experiments on other mechanisms of auxin‐induced growth.
The influence of carbon source on the growth and development of asexual embryos of Theobroma cacao
Authors: Kononowicz Andrzej K. , Janick Jules
Published: April 2006

Asexual embryos of Theobroma cacao L. cultured in a liquid medium on a rotary drum apparatus were induced to produce storage lipids, anthocyanin, and alkaloids by increasing concentration of sucrose but not glucose, and only slightly by fructose or fructose + glucose at the same osmolarity. Glucose combined with sucrose or alternating with sucrose reduced lipid concentration as compared to sucrose alone. The concomitant development of lipids, anthocyanin, and alkaloids suggests that sucrose at high concentration regulates the initiation of embryo development.
Gas and ion exchanges in wheat roots after nitrogen supply
Authors: Barneix Atilio J. , Breteler Hans , van de Geijn Siebe C.
Published: April 2006

Wheat (Triticum aestivum L. cv. Sicco) was grown for 10 days on CaSO4 (0.5 mmol dm−3) and then exposed for 2 days to various nitrogenous salts in an apparatus designed to measure the exchange of O2 and CO2, at constant pH and pNO3. Nitrate salts (KNO3 at 0.5 and Ca(NO3)2 at 0.25 and 1 mmol dm−3) caused a transient increase (40–50%) in both O2uptake and CO2 release by the roots. The rate of gas exchange was nearly doubled by (NH4)2SO4 (0.25 mmol dm−3). Respiration was constant in roots kept on CaSO4 or given KCl. In CaSO4 the content of water‐soluble sugars in roots fell by about 15% day−1. The pletion of soluble sugars was higher with NO3− and NH4+(40 and 30% day−1, respectively). At most 10 to 20% of the released CO2 is involved in HCO3N−NO3− exchange and this fraction represents at most 10% of the total carbon imported or 30% of the net carbon gain by the roots. The contribution of the non‐phosphorylating “alternative” route to total root respiration was 15% in CaSO4and over 40% with NH4+ In NO3− the roots respired exclusively via the cytochrome route. Increased respiration at decreased efficiency in roots of NH4+plants may be due to an overproduction of NADH. Our data support the contention that excess NADH as a “by‐product” of the formation of carboxylates in the citrate cycle can be disposed of in an alternative respiratory pathway during NH4+nutrition.
Thigmomorphogenesis: The relationship of mechanical perturbation to elicitor‐like activity and ethylene production
Authors: Takahashi Hideyuki , Jaffe Mordecai J.
Published: April 2006

An extracellular solution obtained from bean (Phaseolus vulgaris L. cv. Resistant Cherokee Wax) stems induced phytoalexin‐like substance and ethylene production in a soybean [Glycine max (L.) Merr. cv. Wayne] cotyledon bioassay. The elicitor‐like activity for phytoalexin formation and ethylene production was increased by mechanical perturbation of bean stems. Moreover, the application of extracted or known elicitors to bean plants mimicked the effect of mechanical perturbation (i.e., inhibition of stem elongation and enhancement of radial growth). The effects of extract when applied exogenously, on elicitor‐like activity in the bioassay as well as stem thickening were decreased by aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis. These results suggest that elicitor‐like substances which are formed in response to mechanical perturbation contribute to the thigmomorphogenesis.
l‐Myo‐inositol‐1‐phosphate synthase from lower plant groups: Partial purification and properties of the enzyme from Euglena gracilis
Authors: Gupta Sarmila Das , Adhikari Jukta , Majumder Arun Lahiri
Published: April 2006

A survey for the enzyme L‐myo‐inositol‐1‐phosphate synthase (EC 5.5.1.4) has been conducted among various members of the lower plant groups, mainly algac, bryophytes and fungi; some properties of the partially purified enzyme from Euglena gracilis Z. are presented. The enzyme was detected in Chloropycean algae, Marchantiales and the Basidiomycetous fungi. The enzyme from Euglena had a pH optimum at 7.5. The Km for glucose‐6‐P was 2.1 mM and for NAD+ 80 μM. When assayed in the absence of added NAD+, the enzyme showed a basal activity suggesting the presence of bund NAD+ in the system. NH4Cl increased the enzyme activity two‐fold, altough the enzyme was inactivated by (NH4)2SO4.
Nitrogen accumulation and mobilization in Citrus leaves throughout the annual cycle
Authors: Moreno Joaquin , García‐Martinez José L.
Published: April 2006

The changes of protein and amino acid contents of young and old leaves from field citrus trees [Citrus sinensis (L.) Osbeck cv. Washington Navel] were studied throughout the year. the total protein content of old leaves decreased during the spring and summer growths, whereas in young developing leaves it increased rapidly. The end of the spring and summer flushes was followed by a quick recovery of the initial protein content due to a process of reversible senescence. The evolution of SDS‐PAGE proteinograms indicated that most of the foliar proteins contributed to the nitrogen mobilization during the spring and summer growth periods. A protein band of molecular weight ca 55,000, probably containing the large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase, decreased relatively more than the others. The amino acid content of the leaves increased during winter time due to the accumulation of proline, which was mobilized during the spring flush. The possible nitrogen storage function of proline is discussed.
Possible evidence for novel metabolism of nitrogen gas by a green alga
Authors: Weathers Pamela J. , Danielli James F. , Bradley Peter M. , Hebb Diane M. , Miller Judith E. , Pesano Rick L.
Published: April 2006

We report the isolation of a cukaryotic green alga (Chlorella, strain WPI‐2) which accumulates large stores of nitrogen (N) during growth in N‐free medium and seems to incorporate14N2, yet does not reduce acetylene to ethylene. Total N accumulation during growth on N‐free medium and in gases free of combined N was measured by three methods: Kjeldahl, oxidative pyrolysis via chemiluminescence (Antek N analyzer), and Dumas (Coleman N analyzer). Increases in N ranging from 22–64%± 1% were observed. Isotope dilution studies using cells labelled with 15NO 3‐ and then shifted to 14N2 in N‐free medium showed dilution of the 15N isotope by 14N from 5.67 to 5.32%± 0.05%. Using a variety of conditions, we were unable to demonstrate the reduction of acctylene to ethylene by WPI‐2, although diazotrophic cyanobacteria gave positive results. Although the data on WPI‐2 are not conclusive in establishing this alga as a diazotroph, the data do suggest that within the Chlorophyceae there may exist a novel form of nitrogen gas metabolism.
Variation in the lag phase and uniformity of the length of the rooting phase prior to adventitious root production in cuttings of Agathis australis
Authors: White Julie , Lovell Peter H.
Published: April 2006

Cuttings of Agathis australis (D. Don) Lindl passed through a well‐defined series of morphological changes prior to root emergence. These phases were incorporated into a morphological index which can be used as a guide for the selection of cuttings at known developmental and anatomical stages. After a variable period (lag phase) during which no external change occurred there was an increase in stem diameter a few milimetres above the cut base. This swelling gradually increased in size and isolated bulges developed. Longitudinal splits then arose in the epidermis over the bulges, followed by root emergence through the splits. Root initiation occurred shortly after the sub‐basal swelling commenced in cuttings that eventually rooted. Removal of the basal 8 mm of a rooted cutting (which included the roots) usually led to re‐rooting of the cuttings. However, if the roots were merely trimmed off, the cutting never formed new roots and always died. The basal region apparently has the capacity to produce only one set of roots. Occasionally the stem diameter continued to increase and the swelling extended to include the basal region. Such cuttings never formed isolated wellings and never rooted.

In general the younger the plant from which the cutting was taken, the shorter the lag phase and the higher the final percentage rooting. Cuttings taken from older plants had a lower rooting percentage and a more variable lag phase, which was related to the time of year the cuttings were taken since root emergence always occurred in spring. Irrespective of the age of the original material there was a constant time period (3–4 weeks) from root initiation to root emergence.
Stimulation par la lumière rouge lointain de la synthèse de la δ‐aminolévulinate déshydratase des cotylédons de radis
Authors: Huault Claude , Balangé Philippe Bruyant et Alain Pierre
Published: April 2006

Stimulation of de novo synthesis of δ‐aminolevulinate dehydralasc of radishes grown under far‐red light.

Density labelling studies of δ‐aminolevulinate dehydratase (ALAD) in cotyledons of radish (Raphanus sativus L. cv. Longue Rave Saumonée) seedlings demonstrate that far‐red light stimulates de novo synthesis of ALAD and that the turn‐over of this enzyme is very poor. Cycloheximide reduces considerably both the increase of ALAD activity and the incorporation of deuterium in ALAD, which indicates that ALAD synthesis depends upon cytoplasmic ribosomes.
Light‐cytokinin interaction in shoot formation in cultured cotyledon explants of radiata pine
Authors: Villalobos Victor M. , Leung David W. M. , Thorpe Trevor A.
Published: April 2006

Previous studies utilizing cotyledon explants of radiata pine (Pinus radiata D. Don) revealed that cytokinin was required for shoot formation. This was confirmed and extended in the present study, which also showed that light was required. As little as three days of exposure to 16 h photoperiod light at a photon fluence rate of ca 80 μmol m−2 s−1 was sufficient to give some meristematic tissue formation. Longer exposure to light increased this formation. While cytokinin must be present during the first three days in culture for shoot formation, the exposure of the cotyledons to light could be delayed at least until day 10, but after 21 days in darkness, transfer to light did not permit shoot formation. Anatomical examination of the cotyledons confirmed the morphogenetic interactions of light and cytokinin in shoot formation. The data suggest that cytokinin is directly involved in the induction of shoot initiation and both light and cytokinin are required for the development of meristematic tissue and subsequent shoot formation.
Nutritional and root development factors affecting growth of tissue culture plantlets of loblolly pine
Authors: McKeand S. E. , Allen H. L.
Published: April 2006

Tissue culture plantlets of loblolly pine (Pinus taeda L.) were compared to seedlings to quantify growth and developmental differences. The two plant types were grown in containers in a greenhouse and sampled periodically for twenty weeks. Dry weights and nitrogen and phosphorus concentrations of the shoots and roots were determined every two weeks.

During the twenty weeks in the greenhouse, seedlings grew to a greater size than the plantlets, but the relative rates of growth were approximately equal. Plantlets had significantly lower concentrations of nitrogen and phosphorus per g of shoot dry weight. Seedlings were much more efficient at nutrient uptake per g of dry weight of root. Plantlets had thick, unbranched roots, which were inefficient at nitrogen and phosphorus uptake. Nutrient uptake based on an index of root surface area was equal in the plantlets and seedlings.

The main differences between plantlets and seedlings apparently were related to root system morphology rather than physiological processes. The uptake of nutrients showed the greatest difference between the plant types.
RNA and protein metabolism during adventitious root formation in stem cuttings of Phaseolus aureus
Authors: Jarvis B. C. , Yasmin S. , Coleman M. T.
Published: April 2006

Indole‐3‐butyric acid (IBA, 10−4M), spermine (7 × 10−5M) and vitamin D2 (6.3 × 10−5M), all of which enhance rooting in mung bean cuttings (Phaseolus aureus Roxb. cv. Berkin), influence RNA metabolism. Total and poly (A)+‐RNA synthesis within the hypocotyl is inhibited by each of these chemicals within 24 h. These changes precede induced cell division and are therefore associated with the so‐called inductive period of regeneration during which some cells in the hypocotyl undergo dedifferentiation. However, following subsequent transfer of cuttings to borate, which is an essential prerequisite for development of root primordia in these cuttings, RNA synthesis is enhanced by pretreatments with IBA, spermine or vitamin D2. Furthermore, IBA inhibits synthesis and turnover of protein within the hypocotyl.
Genotypic variation in tissue water relations of leaves and roots of black walnut (Juglans nigra) seedlings
Authors: Parker W. C. , Pallardy S. G.
Published: April 2006

Genetic variation in the drought response of leaf and root tissue water relations of seedlings of eight sources of black walnut (Juglans nigraL.) was investigated using the pressure‐volume technique. Tissue water relations were characterized at three stages of a drying cycle during which well‐watered plants were allowed to desiccate and then were reirrigated.

Sources varied both in the capacity for and degree of leaf and root osmotic adjustment, and in the mechanism by which it was achieved. A decrease in osmotic potential at the turgor loss point (ψπp) of 0.4 MPa was attributable to increased leaf tissue elasticity in seedlings of four sources, while seedlings of an Ontario source exhibited a 0.7–0.8 MPa decline in ψπpas a result of both increased solute content and increased leaf tissue elasticity. Seedlings of a New York source showed no detectable osmotic adjustment.

In roots, decreased ψπp(osmotic potential at full hydration) and ψπpwere observed under drought. Sources that exhibited significant leaf osmotic adjustment also generally showed a similar response in roots. Tissue elasticity and ψπpof roots were higher than those of shoots, whereas ψπpof the two organs was similar for most sources. Because of greater elasticity, roots exhibited a more gradual decline in turgor and total water potential than did leaves as tissue relative water content decreased.
Physiological and structural responses of the cyanobacterium Anabaena cylindrica to aluminium
Authors: Pettersson Annette , Hällbom Lars , Bergman Birgitta
Published: April 2006

When adding aluminium (3.7–370 μM) as AlCl3–6H20 to cultures of the nitrogen‐fixing cyanobacterium Anabaena cylindrica, strain 1403/2a (CCAP), the following responses were observed: The effects of aluminium were dependent on pH. being most drastic at pH 6.0. At this pH the growth of A. cylindrica was significantly reduced by 3.7 μM aluminium and completely inhibited by 370 μM. The content of chlorophyll a and phycocyanin decreased after treatment with aluminium. Also, aluminium lowered the rates of both CO2‐fixation and N2‐fixation with total inhibition of both processes by 370 μM. At the lower concentrations used the nitrogenase activity started to recover after about 100 h. The aluminium content in the cells increased with increasing concentration and with time. At 190 μM the aluminium concentration in the cells represented 2.4 and 3.3% of the dry weight after 6 and 24 h, respectively. Clogging of filaments and lysis of vegetative cells were apparent at higher aluminium concentrations while the frequency of heterocysts increased in all concentrations used. The most pronounced ultrastructural changes included accumulation of cyanophycin granules and degradation of the thylakoids. The ultrastructure of the heterocysts was however not affected. It is concluded that major reasons for the toxicity are interactions with membranes and phosphate deficiency.
The effect of Cd2+ on photosynthetic reactions of mesophyll protoplasts
Authors: Weigel H. J.
Published: April 2006

Photosynthetic CO2‐fixation of mesophyll protoplasts of lambs lettuce [Valerianella locusta (L.) Betcke] was inhibited by short time exposure to Cd+. Inhibition was due to uptake of the metal ion into the protoplasts and increased with increasing Cd2+ concentrations and the time of preincubation. A 10 min pretreatment at 2 mM Cd2+ reduced CO2‐fixation by 40–60%. Inhibition of photosynthesis was independent of the light intensity to which the protoplasts were exposed. Measurement of the lightinduced electrochromic pigment absorption change at 518nm and chlorophyll fluorescence studies revealed that primary photochemical reactions associated with the thylakoid membranes were not affected by the metal ion. Also, light activation of the ribulose‐1,5‐bisphosphate carboxylase (EC 4.1.1.39) was not inhibited by Cd2+. Under rate‐limiting CO2 concentrations, inhibition of CO2‐fixation was smaller than at Vmax of CO2 reduction indicating that the carboxylation reaction of the Calvin cycle is not susceptible to Cd2+. Cd2+ treatment of protoplasts significantly extended the lagphase of CO2‐supported O2‐evolution and partly inhibited light activation of the glyceraldehyde‐3‐phosphate dehydrogenase (EC 1.2.1.13) and the ribulose‐5‐phosphate kinase (EC 2.7.1.19). Measurement of relative concentrations of [14C]‐labeled Calvin cycle intermediates showed that Cd2+ caused a decrease in the 3‐phosphoglycerate/triose phosphate ratio and an increase in the triose phosphate/ribulose‐1,5‐bisphosphate ratio. It is concluded that in protoplasts Cd2+ affects photosynthesis mainly at the level of dark reactions and that the site of inhibition may be localized in the regenerative phase of the Calvin cycle.
Continuous measurement of oxaloacetate in purified mitochondria from the leaves of Kalanchoë blossfeldiana
Authors: Rustin Pierre , Rötig Agnès , Alin Marie‐Françoise
Published: April 2006

A new method for the continuous assay of oxaloacetate released or taken up by plant mitochondria during malate oxidation is described. It is based on the continuous spectrophotometric recording of the reduction level of externally added NAD+ (0.4 mM) to a mitochondrial preparation. In the presence of 20 mM malate and of externally added malate dehydrogenase (EC 1.1.1.37), an equilibrium is reached instantaneously, bringing about a partial reduction of NAD+ and the production of a proportional amount of oxaloacetate (OAA). Owing to the presence of a very active OAA carrier on the inner mitochondrial membrane, the concentration at the equilibrium position of the reactants of the external MDH is permanently displaced by the OAA released or taken up by the mitochondria. Therefore, changes in OAA concentration can be followed from the measurement of the reduction level of the external NAD+. This method appears as sensitive as the classical enzymatic method, but is much more rapid and requires much less mitochondrial protein. The proposed method was applied to Percoll‐purified mitochondria from the leaves of a CAM plant, Kalanchoë blossfeldiana Poelln. cv. Tom Thumb. The simultaneous recording of the change in OAA concentration and of oxygen uptake during malate oxidation emphasizes the major control exerted by OAA on the rate of malate oxidation.
Protective mechanisms in photosynthesis of Anabaena cylindrica
Authors: Laczkó Hona
Published: April 2006

The role of O2 photoreduction was studied in intact cells of normal and photobleached Anabaena cylindrica Lemm. strain PCC 7122. We found that O2 photoreduction represents a protective mechanism against over‐reduction of the photosyn‐thetic electron transport chain only in normal Anabaena cells. This protective mechanism was not functioning in photobleached cells in spite of the increased rate of photosynthetic electron flow. A new electron acceptor, the induced reversible hydrogenase, is suggested to be operating in photobleached Anabaena cylindrica.
Senescence of Hydrilla leaves in light and darkness
Authors: Kar R. K. , Choudhuri M. A.
Published: April 2006

Senescence of isolated leaves of Hydrilla verticillata (L.f.) Royle was studied in both darkness and light (20 μmol m−2 s−1). Senescence in the dark followed a general pattern of deterioration, i.e., gradual loss of cellular macromolecules like chlorophyll, protein and RNA with a concomitant rise in α‐amino nitrogen, protease activity and tissue permeability. In light, however, an accelerated loss of chlorophyll took place although protein loss and increase in protease activity were retarded. A higher level of α‐amino nitrogen in leaves in the light than in darkness could be correlated with lower leaching of free amino acids in light. Light decreased tissue permeability, as evidenced by lower conductivity of the incubation medium. In the light, RNA increased over the initial level. Both soluble and insoluble carbohydrates declined in the dark. The decline of insoluble carbohydrate was retarded by light, whereas soluble carbohydrate showed an initial rise and then declined sharply in the light.
Mechanism of Cd2+resistance inEuglena gracilis
Authors: Bariaud A. , Bury M. , Mestre J. C.
Published: April 2006

The characteristics of Cd2+accumulation byEuglena gracilisL. strain Z have been studied using sensitive and resistant cells. In both strains Cd2+is mainly absorbed by a temperature‐ and light‐dependent process. Resistance to Cd2+is associated with a lower accumulation of Cd2+and with a decreased affinity for Cd2+. Gel filtration on Sephadex G75 of the soluble fraction shows that resistance is not linked to an induction of metallothioneins.
Benzyladenine‐induced stimulation of 5‐aminolevulinic acid accumulation under various light intensities in levulinic acid‐treated cotyledons of etiolated cucumber
Authors: Dei Mitsuru
Published: April 2006

Benzyladenine (BA) stimulated 5‐aminolevulinic acid (ALA) accumulation in the presence of levulinic acid during illumination with 43 μmol m−2 s−1 light in excised etiolated cotyledons of cucumber (Cucumis sativus L. cv. Aonagajibai). A short dark‐pretreatment (6 h) with BA eliminated the lag phase of ALA accumulation. The rate of ALA accumulation during the steady‐state phase in cotyledons pretreated with BA for a long period (14 h) was considerably accelerated compared to that in cotyledons pretreated with BA for 6 h. The rate of ALA accumulation during the lag phase was saturated at a very low light fluence (<1.4 μmol m−2 s−1) in both BA‐pretreated and water‐control cotyledons. The steady‐state rate of ALA accumulation increased with increasing light fluence up to 43 μmol m−2 s−1 (parallel to that of Chl formation) in water‐control cotyledons. In contrast, in cotyledons pretreated with BA for either 6 or 14 h, the steady‐state rate reached a plateau at a very low light fluence. Based on the above results together with our finding that there are two components of Chl formation (M. Dei, 1984. Physiol. Plant. 62: 521–526) possible intermediate steps of Chl biosynthesis pathway affected by BA and light intensity are discussed.
Growth inhibition of crown‐gall tissues in relation to the structure and activity of DNA
Authors: Le Goff L. , Roussaux J. , Cunha M. I. Aaron‐da , Beljanski M.
Published: April 2006

The growth of crown‐gall cells cultured in vitro (Nicotiana tabacum L. cv. White Burley and Parthenocissus tricuspidata cv. Veitchii) is inhibited by alstonine (BG‐8), a plant alkaloid, the anti‐cancer effect of which has previously been demonstrated on animals and plants. The growth of normal cells is only slightly affected. The inhibitory effect of BG‐8 on crown‐gall cells is antagonized by indole‐3‐acetic acid (IAA) added to the culture medium. Kinetin associated with IAA does not prevent this inhibitory effect. BG‐8 present in the culture medium containing the two types of hormones seems to modify the later hormonal requirement of Parthenocissus crown‐gall tissues.

BG‐8 exhibits high binding affinity for crown‐gall DNA and, therefore, strongly inhibits its in vitro synthesis. The alkaloid has practically no effect on DNA from healthy cells. The inhibition by BG‐8 is dependent on the level of DNA strand separation and on the origin and nature of the tissues (crown‐gall DNA is more destabilized than healthy DNA; DNA from habituated tissues is intermediate). IAA and kinetin have opposite effects on the in vitro strand separation of the DNAs from crown‐gall cells and, consequently, antagonistic effects on DNA replication (IAA stimulates and kinetin inhibits). It is possible to establish a close relationship between in situ development of crown‐gall tissues of the two species studied (in the presence or absence of BG‐8 or cell‐growth factors), in vitro DNA synthesis and DNA strand separation.
Identification of jasmonic acid in Mimosa pudica and its inhibitory effect on auxin‐ and light‐induced opening of the pulvinules
Authors: Tsurumi Seiji , Asahi Yoshihiko
Published: April 2006

Jasmonic acid was identified from Mimosa pudica L. plants by mass spectrometry, high performance liquid chromatography and thin layer chromatography. Effects of authentic jasmonic acid on pulvinule movement and transpiration of the pinnae were compared with those of abscisic acid. Jasmonic acid and abscisic acid each at 10−5M inhibited both auxin‐ and light‐induced opening of the pulvinules. A closure‐inducing activity of jasmonic acid at 10−4M was greater than that of abscisic acid at 10−4M. Pinnae transpiration was reduced by 10−5M abscisic acid but not by 10−4M jasmonic acid.
Effect of cold hardening, wilting and exogenously applied proline on leaf proline content and frost tolerance of several genotypes of Solanum
Authors: van Swaaij A. C. , Jacobsen E. , Feenstra W. J.
Published: April 2006

Frost tolerance and leaf proline content were examined in a number of potato hybrids selected for frost tolerance and in the cv. Astarte before and after hardening. Cold hardening (2°C for 20 days) in a dry environment (50/90% relative humidity, day/night) resulted in decreased water content, increased proline content and increased frost tolerance of the leaves of all genotypes. Frost tolerance before and after hardening was positively related to leaf proline content, but not to leaf water content. Drought stress alone, imposed by wilting excised leaves for 4 days, resulted in an accumulation of proline comparable to that after hardening in a dry environment, but the increase in frost tolerance was smaller. Cold hardening in a humid environment (90% relative humidity continuously) only caused a minor accumulation of proline and a small increase in frost tolerance, but the increase in frost tolerance was high in relation to the amount of proline accumulated. Proline, exogenously applied to one of the genotypes, was accumulated in the leaves of shoot cultures, resulting in an increase in frost tolerance. A possible role of proline in frost tolerance is discussed.
Induction of embryogenic callus in Cucurbita pepo hypocotyl explants by indole‐3‐ethanol and its sugar conjugates
Authors: Jelaska Sibila , Magnus Volker , Seretin Mira , Laćan Goran
Published: April 2006

Hypocotyl explants of pumpkin (Cucurbita pepo L.) were inoculated aseptically on solid media containing Murashige and Skoog (MS) macro‐ and micronutrients, organic supplements, glucose as a carbon source, and indoleacetic acid (IAA) or one of its possible metabolic precursors, i.e. indole‐3‐ethanol [3‐(2‐hydroxyethyl)‐indole, tryptophol], 2‐(indol‐3‐yl)‐ethyl α‐L‐arabinopyranoside (tryptophol arabinoside), and 2‐(indol‐3‐yl)‐ethyl β‐D‐glucopyranoside (tryptophol glucoside). Embryogenic callus and adventitious roots developed on the explants, the response depending on the source of auxin, its concentration, and endogenous, possibly genetic, factors. Hypocotyl sections did not form embryogenic tissues and did not survive on media which did not contain an auxin or auxin precursors. Fewer explants responded to IAA than to indole‐3‐ethanol. Its arabinopyranoside was even more effective, while only a few hypocotyl sections proliferated in the presence of the corresponding glucopyranoside. Embryogenic callus induced by any of the four above compounds could be subcultured on media containing the same source of auxin. Selected callus lines have been maintained for more than three years and have continued to form embryoids. Indole‐3‐ethanol and IAA were suitable for clonal propagation of regenerated plantlets by axillary and apical bud culture.
Adenine nucleotide contents in callus‐forming potato tuber discs with different respiratory characteristics
Authors: Hemrika‐Wagner Anneke M. , van der Plas Linus H. W.
Published: April 2006

ATP content (per g fresh weight) and energy charge were higher during incubation at 8°C than at 28°C in the early stages of callus induction of potato tuber discs (Solanum luberosum L. cv. Bintje). After a transfer from 28°C to 8°C, ATP content increased while a sharp decline in ATP content was observed after a transfer from 8°C to 28°C. ADP and AMP pools did not increase correspondingly. When the callus discs had entered the logarithmic growth phase, the energy charge was maintained within relatively narrow limits (0.77–0.80) at all culture temperatures.
Glycosylation is not needed for the intracellular transport of phytohemagglutinin in developing Phaseolus vulgaris cotyledons and for the maintenance of its biological activities
Authors: Bollini Roberto , Ceriotti Aldo , Daminati M. Gloria , Vitale Alessandro
Published: April 2006

Approximately 10% of the total protein contained in Phaseolus vulgaris L. cv. Greensleeves seeds is composed of the glycoprotein lectin, phytohemagglutinin. We have investigated whether the presence of N‐linked oligosaccharide side chains is a prerequisite for the correct intracellular transport of this protein and whether unglycosylated phytohemagglutinin maintains its biological activities. Excised developing cotyledons were incubated in the presence of tunicamycin to prevent glycosylation “in vivo”, and the fate of the unglycosylated protein synthesized in such cotyledons determined. It was found that unglycosylated phytohemagglutinin reaches its normal site of accumulation, the protein bodies, and maintains erythro‐agglutinating and mitogenic activities.
Comparison of K,MgATPases in purified plasmalemma from wheat and oat. – Substrate specificities and effects of pH, temperature and inhibitors
Authors: Sommarin Marianne , Lundborg Tomas , Kylin Anders
Published: April 2006

Plasmalemma from 8‐day old oat (Avena sativa L. cv. Brighton) and spring wheat (Triticum aestivum L. cv. Drabant), grown in the dark at 18°C, was prepared from the 10000 g (10 min) – 30 000 g (60 min) root homogenate by two‐phase separation in three steps with 6.5% (w/w) Dextran T 500 and 6.5% (w/w) polyethylene glycol 4 000. Biochemically and with respect to activation by Mg2+ as well as by (Mg2++ K+), the oat preparations clearly appeared as ATPase(s) in the pH range 5–8. They showed high specificity for ATP, temperature optima between 38 and 40°C, and were inhibited by vanadate, DCCD (dicyclohexylcarbodiimide) and SH‐reagents, but not by oligomycin, ammonium molybdate or ouabain. In contrast, the preparations from wheat contained more than one type of MgATPase/ nucleotidase, as revealed by complex dependence on both pH and temperature as well as by comparatively low specificity towards nucleotides. However, no unspecific phosphatase was present, and the effect of K+ over and above that of Mg2+ was almost as specific as in oat by all criteria used. The data available from this and earlier investigations from our group would indicate that the complex reactions of preparations of wheat plasmalemma may not be due to contamination but, rather, expressions of the many biological functions that must be associated with the plasmalemma in vivo and which may be located in sub‐units that are more firmly attached to wheat than to oat plasmalemma.
A gibberellin insensitive mutant of Arabidopsis thaliana
Authors: Koorneef M. , Elgersma A. , Hanhart C. J. , van Loenen‐Martinet E. P. , van Rijn L. , Zeevaart J. A. D.
Published: April 2006

A dwarf mutant of Arabidopsis thaliana (L.) Heynh. was found to be less sensitive to applied gibberellins than the wild type, and this character was controlled by one partially‐dominant gene (denoted Gai) located on chromosome 1. This mutant resembled gibberellin‐deficient mutants since not only stem growth, but also apical dominanace and seed germination were reduced. However, in contrast to the latter mutants, gibberellin does not reverse these effects in the Gai mutant. The insensitivity of the mutant could be quantified in much more detail in the recombinant of this mutation with the GA deficient mutant ga‐1/ga‐1. Endogenous gibberellins of the Gai mutant did not differ from the wild type either in quantity or composition. The data suggest that the gene controls a step involved in gibberellin action.
Flavanone glucosides in callus and phloem of Prunus avium: Identification and stimulation of their synthesis
Authors: Tretter D. , Galensa R. , Feucht W. , Schmid P. P. S.
Published: April 2006

The flavanone glucosides dihydrowogonin‐7‐glucoside, eriodictyol‐7‐giucoside and prunin (naringenin‐7‐glucoside) were isolated, identified and quantitatively determined in callus cultures and phloem of Prunus avium L. cvs. Sam and Schneiders. These substances were isolated from callus tissue, where they were most abundant. The identification included TLC, HPLC and spectrophotometry in conjunction with hydroxylation and benzoylation. Elevation of sucrose concentrations in the media from 1 to 4% (w/w) resulted in a 3‐ to 4‐fold increase in prunin. A similar response, although much less pronounced, was observed for eriodictyol‐7‐glucoside, while dihydrowogonin‐7‐glucoside was not enhanced under these conditions. Addition of benzyladenine to media of tissue cultures also caused an increase in prunin and eriodictyol‐7‐glucoside levels. Both of these flavanones also increased in phloem above and below a constriction of Prunus stems. Administration of benzyladenine into Prunus stems resulted in a 4‐fold increase of prunin in the phloem.
Nutrition and growth of coniferous seedlings at varied relative nitrogen addition rate
Authors: Ingestad Torsten , Kähr Monika
Published: April 2006

The growth of two provenances of Pinus sylvestris L. were compared with two provenances of Picea abies (L.) Karst. and with Pinus contorta Dougl. when grown in solution cultures with low nutrient concentrations. Nitrogen was added at different exponentially increasing rates, and the other nutrients were added at a rate high enough to ensure free access of them to the seedlings.

During an initial period of the culture (a lag phase), when the internal nutrient status was changing from optimum to the level of the treatment, deficiency symptoms appeared. The needles yellowed and the root/shoot ratio increased. The initial phase was followed by a period of exponential growth and steady‐state nutrition. The needles turned green again, and the root/shoot ratio stabilized at a level characteristic of the treatment. These patterns were the same as previously reported for other tree species.

The relative growth rate during exponential growth was numerically closely equal to the relative nitrogen addition rate. The maximum relative growth rates were about 6 to 7.5% dry weight increase day‐1. This is a much lower maximum than for broad‐leaved species (about 20 to 30% day‐1) under similar growth conditions.

The internal nitrogen concentrations of the seedlings and the relative growth rates were stable during the exponential period. Close linear relationships were found between these parameters and the relative addition rate up to maximum growth.

During steady state the relative growth rates of the different plant parts were equal. However, there were large differences between genotypes in absolute root growth rate at the same seedling size because of differences in root/shoot ratio. Lodgepole pine had the highest root growth rate, whereas that of Norway spruce, especially the southern provenance, was remarkably low. Yet, Norway spruce had a high ability to utilize available nutrients. In treatments with free nutrient access, growth allocation to the shoot had a high priority in all genotypes, but there was still a marked tendency for luxury uptake of nutrients. Nitrogen productivity (growth rate per unit of nitrogen) was lower than in broadleaved species and highest in lodgepole pine. The relevance of the dynamic factors, i.e. maximum relative growth rate, nutrient uptake rate, nitrogen productivity, growth allocation and root growth rate, are discussed with regard to conifer characteristics and selection value.