bluuebunny/crossref_metadata_2025 huggingface dataset:
Phytochrome in Pharbitis nil during and after de‐etiolation
Authors: Rombach J. , Bensink J. , Katsura N.
Published: April 2006

Phytochrome (P) was measured by in vivo spectrophotometry in the cotyledons of Pharbitis nil Choisy cv. Violet. In etiolated plants exposure to red light (R) results in a rapid fall in P content by destruction of the far‐red absorbing form of phytochrome (Pfr). In continuous R or white light the P content falls as a result of destruction to a stable 3% of that originally present. In Norflurazon‐treated white light de‐etiolated plants, Pfr undergoes reversion in darkness to the red absorbing form of phytochrome (Pr) with a half life of 4 h at 19°C, while total P remains constant. Synthesis of Pr after de‐etiolation occurs at a slow rate and is enhanced by terminating the de‐etiolation light treatment with far‐red light. The results are discussed in relation to the P control of flowering.
Le transport basipète de l'AIA‐5‐3H dans le coléoptile de blé
Authors: Perbal Gérald , Driss‐Ecole Dominique , Leroux Yves
Published: April 2006

Basipetal transport of [5‐3H] IAA in the wheat coleoptile

3H‐IAA was applied to the tips of intact wheat coleoptiles (Triticum sativum L., var. Capitole) for 30, 60 or 120 min. The quantity of label per segment (1.5 mm), determined by liquid scintillation counting, was a decreasing exponential function of distance from the source of radioactivity. Chromatographic analysis showed that 3H‐IAA was transported more rapidly than its tritiated metabolites. Antoradiographs of semi‐thin sections were performed after application of 3H‐IAA during 2 h and after treatment by DCC [1‐(3‐dimethyl‐aminopropyl)‐3‐ethycarbodiimide hydrochloride]. The quantity of label per tissue and per cell was determined at 1.5, 3.0 and 4.5 mm from the tip. Tritiated IAA was estimated to account for 70 to 100% of the label, depending on the distance from the tip. The amount of auxin transported basipetally was greatest in the parenchyma, with lesser amounts transported in the inner and outer epidermis. Tissues of the vascular bundles did not contain more than 10% of total radioactivity of the coleoptile sections. The rate of auxin transport was greater in xylem and parenchyma than in epidermis and bundle sheath. Movement was very slow in procambium and phloem. In parenchyma and epidermis the quantity of label per cell as a function of distance from the tip agreed with the model of exponential regression. These results support the theory of polar diffusion of auxin.
Translocation of selenium in the bean plant (Phaseolus vulgaris) and the field bean (Vicia faba)
Authors: Arvy Marie‐Pierre
Published: April 2006

Selenium distribution in the bean plant (Phaseolus vulgaris L. cv. Contender) was studied using autoradiographs of the whole plant and of sections of organs. A few hours after the incubation of the roots with (75Se) selenate, a major part of the selenate accumulates in the roots, while the fraction conveyed towards the aerial organs is unevenly distributed, resulting in accumulation of 75Se in the young leaves, the buds and the epicotyl. This distribution results from a general translocation of selenium through the xylem. A secondary process of redistribution is then immediately linked to the transport of 75Se labeled products (such as seleno‐amino acids) in the phloem from the mature leaves. A similar pattern of translocation of selenium was found in the field bean (Vicia faba L. cv. Aguadulce) by using aphids that insert their stylets into the sieve tubes. Measurement of the radioactivity of these insects shows that the 75Se content of the phloem sap was reduced to low levels when all the mature leaves were excised. The mature leaves thus serve as relaying organs, redistributing the selenium which is carried in by the movement of water through the xylem.
Effect of abscisic acid pretreatments on stomatal reopening in Vicia faba
Authors: Wardle Keith , Dobbs Elizabeth B. , Short Keith C.
Published: April 2006

After a pretreatment of 2 h exposure to a solution containing 2 × 10−4M ABA, reopening of stomata occurred in epidermal strips of Vicia faba L. cv. Cavalier on an ABA‐free incubation solution. After pretreatment with exogenous ABA stomatal apertures were greater when higher levels of KCl were incorporated into the solution used for reopening. Prolonged exposure to exogenous ABA (14 h) did not prevent stomatal reopening upon transfer to ABA‐free solutions. However, for both ABA and ABA‐free pretreatments, prolonged incubation (1 day after removal of epidermis) resulted in enhanced stomatal apertures when the epidermal strips were exposed to light. This effect was lost 2 days after removal of the epidermis and opening did not occur after 3 days. Epidermal strips containing endogenous ABA were obtained from wilted leaves. Reopening was greatly reduced by the endogenous ABA treatment, and variation of KCl concentration in the incubation solution had little effect on stomatal aperture. It is postulated that during wilting endogenous ABA becomes reversibly bound without loss of activity for a longer period than is obtained using exogenous ABA. The presence of other unidentified compounds may be involved in this process.
Synthèse et hydrolyse du saccharose dans l'œillet alimenté avec une solution glucosée
Authors: Paulin André , Droillard Marie‐Jo
Published: April 2006

Sucrose synthesis and sucrose hydrolysis in cut carnations (Dianthus caryophyllus) supplied with glucose solution.

Sucrose synthesis and hydrolysis in cut carnations supplied with a glucose solution have been investigated using both entire floral branches and floral branches without any of their organs (petals, non‐petaloid pieces, leaves) and isolated organs. – The flower is a more active sink that the leaves. The transformationn of glucose into sucrose is essential for the ability of the flower to use the exogenous glucose. All organs of the floral branch (petals, ovaries and sepals, leaves, stem) are able to form sucrose. The hydrolysis of the obtained sucrose occurs nearly exclusively in the petals.
The isolation, culture and division of protoplasts from citrus cotyledons
Authors: Burger David W. , Hackett Wesley P.
Published: April 2006

High yields (2.3 × 105 to 1.3 × 106 protoplasts/g.f.wt.) of isolated protoplasts were obtained from cotyledons of Cirus sinensis (L.) Osb. ‘Valencia’. Osmotic potential of the medium and enzyme concentrations were important in obtaining high viability of preparations as indicated by FDA fluorescence. Adding malt extract to a Murashige‐Tucker basal medium increased plating efficiencies somewhat, but not the rate or duration of cell division. However, modifying the NAA and kinetin concentration optimized plating efficiencies (up to 20%) of protoplasts and also the rate or duration of cell division. The highest plating efficiency and number of cells per colony were obtained on a defined medium containing NAA (15 μM). and kinetin (4.6 μM). Coincidence of percentage protoplast viability after 13 days (assessed by FDA fluorescence) with plating efficiency after 21 days indicates that FDA fluorescence is an accurate indicator of citrus protoplast viability.
Effects of phloridzin, metavanadate and oligomycin on membrane bound (Na++ K++ Mg2+)ATPase activity in sugar beet roots
Authors: Wingstrand Göran , Lindberg Sylvia
Published: April 2006

To clarify the reaction mechanism of a (Na++ K++ Mg2+)ATPase activity in sugar beet roots (Beta vulgaris L. cv. Monohill) phloridzin, oligomycin (inhibitors of animal ATPases) and metavanadate (NH4VO3) have been used. Kinetic studies showed that: 1) Phloridzin inhibition is uncompetitive with respect to MgATP and not influenced by Na+ or K+. 2) This inhibition is only found in preparations made in the absence of sucrose. 3) Oligomycin and vanadate inhibit the ATPase in different ways. Omission of sucrose from the preparation medium favours vanadate inhibition but suppresses oligomycin inhibition. 4) The kinetic pattern of the Na+ activation of the ATPase differs in preparations made in the absence and presence of sucrose, but that of K+ activation is the same. – These results indicate that inclusion as against omission of sucrose from the preparation medium causes a conformational change of the membrane fragments/vesicles, which then expose different surfaces to the surrounding medium.
Tracer studies of gas circulation in Nuphar: 18O2 and 14CO2 transport
Authors: Dacey J. W. H. , Klug M. J.
Published: April 2006

A flow‐through ventilation system operates in the yellow waterlily (Nuphar luteum ssp. macrophylla Beal). The flow of air into the youngest emergent leaves and down their petioles to the rhizome is confirmed by 18O2 and 2H2 tracer experiments conducted in the field, showing that most of the O2 in the rhizome originated in the atmosphere. This flow of air into the rhizome forces a simultaneous gas flow from the rhizome up the petioles of the older emergent leaves to the atmosphere. Radiolabelled CO2 was used to demonstrate that CO2 present in the gas moving up these petioles was fixed before reaching the atmosphere.
Levels of free and conjugated indole‐3‐acetic acid in ethylene‐treated leaves and callus of olive
Authors: Epstein Ephraim
Published: April 2006

Changes in levels of free and conjugated indole‐acetic acid (IAA) resulting from ethylene treatment were examined in leaves and callus of olive (Olea europea var. Manzanillo) by electron capture gas chromotography and by isotope dilution analysis. In both olive leaves and olive tissue cultures, the level of free IAA did not change much after the exposure to ethylene, but the levels of bound IAA increased almost three times in comparison with untreated controls. This is the first report of changes in endogenous, bound auxin accompanying ethylene treatment.
Agrobacterium adherence involves the pectic portion of the host cell wall and is sensitive to the degree of pectin methylation
Authors: Rao Sukanya S. , Lippincott Barbara B. , Lippincott James A.
Published: April 2006

Cell walls isolated from dicotyledon tissues compete with natural plant host sites for Agrobacterium tumefaciens (strain B6) when co‐inoculated with infectious bacteria, thereby reducing tumor initiation. Removal of the pectic fraction from the cell walls results in loss of inhibition and the soluble pectic fraction is inhibitory. On treatment with pectin methyl transferase plus S‐adenosyl‐L‐methionine these cell walls become less inhibitory and this change is reversible by pectinesterase. Cell walls isolated from monocotyledons, crown gall tumors or embryonic dicotyledons do not compete for Agrobacterium in the infection assay. These cell walls become inhibitory on treatment with pectinesterase and this is partially reversed by pectin methyl transferase. These data indicate that the pectic portion of the host cell wall is involved in the Agrobacterium‐host adherence which is essential for tumor initiation and that the degree of methylation of polygalacturonic acid is critical to this adherence.
High‐frequency plant regeneration from hypocotyl‐ and leaf‐derived tissue cultures of the tropical pasture legume Stylosanthes humilis
Authors: Meijer E. G. M.
Published: April 2006

Callus cultures were established from seedling hypocotyls of the tropical pasture legume Stylosanthes humilis H.B.K., and from leaves of in vitro‐grown regenerated plantlets and glasshouse‐grown plants. Callus was induced on Murashige and Skoog medium, supplemented with 1.0 mg/1 each of benzyladenine and naphthaleneacetic acid, and subcultured on the same medium with 0.5 mg/1 each of the same plant growth regulators. Induction of shoot formation occurred with a number of benzyladenine/naphthaleneacetic acid combinations. With 1.0 mg/1 benzyladenine (no auxin) all hypocotyl‐derived calli and 78% (in vitro‐grown plantlets) and 56% (glasshouse‐grown plants) of the leaf‐derived calli could be induced to form shoots. Morphogenetic potential was maintained during five subcultures. The process of induction of shoot formation took generally longer in leaf‐derived calli than in those derived from hypocotyls. Most regenerated plants survived transfer to soil and all tested plants nodulated if inocculated with Rhizobium. No morphological abnormalities were observed.
Gas exchange in a 20‐year‐old stand of Scots pine
Authors: Troeng E. , Linder S.
Published: April 2006

Net photosynthesis of current and one‐year‐old shoots in Scots pine (Pinus sylvestris L.) was measured during a two‐year period (1977–1978). The measurements were carried out in Central Sweden using a system that allowed in situ measurements throughout the year. The photosynthetically active period, defined as months with a positive carbon dioxide balance, was nine months per year for one‐year‐old shoots and six months for current shoots. The daily rates of net photosynthesis were low in spring and late autumn and 95% of the annual photosynthetic production occurred from May to October. In spring net photosynthesis was limited by a low photosynthetic capacity and a restricted access to water caused by the frozen ground. It took more than three months in spring and early summer to restore full photosynthetic capacity in the one‐year‐old shoots, but the rate of recovery varied considerably between the two years. In late autumn the rates of photosynthesis were mainly limited by low photon flux densities.

The seasonal patterns of photosynthesis were similar between the two years, and even though there were pronounced differences for individual months, the total annual photosynthetic production of the two years only differed by 1.4% for the one‐year‐old shoots. The differences in photosynthetic production for current shoots were much higher as an effect of different rates of needle development and differences in photosynthetic capacity during the two years. An estimate of the carbon balance of the current shoots showed that the shoots had not photosynthesized their own weight in terms of carbon until late August (1978) or early September (1977), which means that their photosynthetic production was of minor importance for the formation of stem wood.
Improvement of anther culture technique: Activated charcoal bound in agar medium in combination with liquid medium and elevated CO2 concentration
Authors: Johansson Lars , Andersson Barbro , Eriksson Tage
Published: April 2006

Anthers of different species of the genera Anemone, Clematis, Papaver and Nicotiana were cultured by floating on a liquid medium which overlay an agarified charcoal medium. This technique proved to be superior to conventional methods i.e. culture on either solid or liquid media. Cold treatment of Anemone anthers for 7 days after inoculation on the double layer medium gave about the same frequency of embryos per anther as corresponding cultures cold treated before inoculation. An elevation of the CO2 concentration to 2% stimulated embryogenesis in anther cultures of Anemone canadensis, Anemone vitifolia, Papaver setigerum and Papaver radicatum. Cold treatment of cultures of Anemone canadensis inhibited embryogenesis if the ensuing culture was performed in 2% CO2. On the other hand, cold treatment was stimulating, with an optimum of about 20 days, if the cultures were maintained in normal air. Chemical analysis of untreated anthers of Anemone canadensis showed the presence of abscisic acid (2.2 × 10−6 g/g anthers). Cold treatment reduced the concentration of abscisic acid to 0.6 × 10−6 g/g anthers. By use of assays with Lemna gibba as test organism, activated charcoal was shown to adsorb abscisic acid that was added to the medium. Medium treated with charcoal before inoculation of anthers of Anemone canadensis provided to inhibit embryo production.
Transcriptional activation and structural alteration of wheat chromatin during germination and seedling‐growth
Authors: Sugita Mamoru , Sasaki Kimiko
Published: April 2006

The chromatin was isolated from embryos or young seedlings of wheat, Triticum aestivum L. cv. Mukakomugi, and the template activity, the endogenous RNA polymerase activity, the susceptibility to DNase 11 and polylysine binding capacity were assayed. Both transcriptional activities of chromatin were very low for the first 12 h of germination, increased from 12 to 24 h, and then increased markedly during the next 48 h of post‐germination. During the 72 h of germination, the template activity and the endogenous RNA polymerase activity increased 10‐fold and 40‐fold, respectively, while they decreased from 72 h to 96 h of seedling growth. Seventy‐two h seedling chromatin was more susceptible to endonuclease and was bound with more polylysine than the germ chromatin. These results suggest that the structure of the chromatin available for transcription changes during seed germination and seedling‐growth.
Effects of temperature and drying rate during dehydration of celery seeds on germination, leakage and response to gibberellin and cytokinin
Authors: Biddington N. L. , Dearman A. S. , Thomas T. H.
Published: April 2006

A high temperature treatment of 32°C which prevents dehydration injury in celery seeds imbibed for 3 days at 17°C and then dried at 20°C, reduced leakage during rehydration, compared with seeds not given the high temperature treatment. Treatments which would normally release celery seeds from dormancy, such as low temperature imbibition or gibberellin (GA4/7) and benzyladenine (BA) applications had little effect on the germination of seeds exhibiting desiccation injury. However, GA4/7 did induce splitting of the seed coat and swelling of the endosperm, and this effect was enhanced by BA. It is suggested that in celery seeds high temperature prevents irreversible embryo damage, including membrane damage, caused by drying.
Effect of polythene covers, a flower inducing treatment, on the content of endogenous gibberellin‐like substances in grafts of Norway spruce
Authors: Chalupka Wladyslaw , Giertych Maciej , Kopcewicz Jan
Published: April 2006

In shoots of 12‐year‐old Norway spruce [Picea abies (L.) Karst.] grafts the content of endogenous gibberellin‐like substances was analysed. Covering the crowns with polythene on the turn of June and July stimulated induction of male strobiles and significantly increased the levels of gibberellins. Polar gibberellin (at Rf 0.0–0.2) increased immediately and the less polar ones after one day. After 2 weeks the increased level was maintained only at Rf 0.4–0.6 and 9 days later the differences between covered and not covered grafts disappeared. Removal of the covers did not affect gibberellin levels. It is suggested that covering with polythene stimulates floral induction through an increase in endogenous gibberellin levels.
Some physico‐chemical properties of a major cationic peroxidase from cultured peanut cells
Authors: van Huystee Robert B. , Maldonado Brian
Published: April 2006

A major cationic peroxidase had been isolated by CMC chromatography from protein isolate of suspension medium that had supported growth of cultured peanut cells. This major cationic peroxidase proved to be antigenically different from both the anionic and the minor cationic peroxidase. Affinity for Concanavalin A found earler for the anionic peroxidase could not be detected for the major cationic peroxidase. The carbohydrate content of the major cationic peroxidase is nearly 15%. The molecular mass of the overall molecule is close to 40,000. Amino acid analysis of the hydrolysate of this major peroxidase showed similarities to amino acids of the hydrolysates of the cationic horseradish peroxidases, but no immunological relatedness could be detected between the major peanut peroxidase and the horseradish peroxidase.
Lack of involvement of polyphenol oxidase in ortho‐hydroxylation of phenolic compounds in mung bean seedlings
Authors: Duke Stephen O. , Vaughn Kevin C.
Published: April 2006

Complete elimination of polyphenol oxidase activity in hypocotyls and leaves of developing mung bean (Vigna radiata L. Wilczek cv. Berkin) seedlings by tentoxin had no effect on the content of the ortho‐hydroxylated flavonoids delphinidin and rutin. Tentoxin completely eliminated polyphenol oxidase‐mediated ortho‐hydroxylation of p‐coumaric acid to caffeic acid. Despite this, tentoxin had no effect on caffeic acid derivative contents in the seedlings. High performance liquid chromatography profiles indicated that elimination of polyphenol oxidase had no effect on either the quality or the quantity of soluble phenolic compounds, These data strongly indicate that polyphenol oxidase is not involved in metabolism of phenolic compounds in developing plant tissues.
The accumulation of accessory pigments as a function of chlorophyll a. A comparison of development and genetic control
Authors: Eskins Kenneth , Kwolek William F. , Harris Leland
Published: April 2006

A comparison is made between pigment accumulation in pigment‐deficient genotypes of soybean (Glycine max) at any one sampling time (genotype control) and pigment accumulation for any one genotype as a function of development (development control). Plots of accessory chloroplast pigments against chlorophyl a show various linear and non‐linear relationships that are similar whether generated by genetic differences or by the development process. These relationships are related to the formation and development of pigment‐protein complexes especially the relationship of carotenoids to these complexes.
Increased drought resistance induced by pretreatment with abscisic acid in germinating embryos of Haplopappus gracilis
Authors: Galli Maria Grazia , Levi Marisa
Published: April 2006

Embryos of Haplopappus gracilis (Nutt.) Gray were prehydrated in water or under different conditions, all of them inhibiting or greatly reducing embryo elongation (abscisic acid, polyethylenglycol, cycloheximide, cordycepin, aminophylline, and at 4°C), dehydrated for 24 h and regerminated. All treatments resulted in improved drought resistance compared with water controls, but the best results were obtained with pretreatment with abscisic acid. In fact these embryos revealed in the rehydration phase, (a) the highest percentage of embryos able to resume germination, (b) the lowest leakage of ninhydrin reacting substances, and (c) the highest level of 14C‐leucine incorporation. Lengthening of the prehydration phase in abscisic acid up to 24–48 h improved the conditions of the embryos in the rehydration phase, with less damage to the cells of the radicle tip. A protective action of abscisic acid, possibly at the level of the cell membrane system, is hypothesized.
Arsenic metabolism in freshwater and terrestrial plants
Authors: Nissen Per , Benson A. A.
Published: April 2006

Freshwater and terrestrial plants differ markedly in their ability to metabolize arsenate. In experiments with higher terrestrial plants, e.g. tomato, Lycopersicon esculentum Mill. cv. Better boy, 74As‐arsenate was readily taken up and reduced to arsenite. Methylation and reduction to methanearsonic acid, methanearsinic acid (indicated for the first time) and dimethylarsinic acid were apparent only in phosphate deficient plants. Lower and higher freshwater plants, e.g. Nitella tenuissima Kütz. and Lemna minima Phill., not only methylated arsenic but also produced considerable amounts of an arsoniumphospholipid previously identified in marine algae. These differences indicate that freshwater but not terrestrial plants have evolved mechanisms for rapid detoxication of arsenate, arsenite and other toxic arsenic species.
Influence de l'intensité et de la longueur d'onde de la lumière sur le rendement des radicaux libres dans les semences de tomate et de carotte
Authors: Khoury A. , Dannaoui S. D. , Ouaida A. F. , Chetverikov A. G. , Stanko S. A.
Published: April 2006

Influence of light intensity and wavelength on the yield of free radicals in seeds of tomato and carrot.

Seeds of tomato (Lycopersicum esculentum L. cv. Gribovsky‐1180) and carrot (Daucus carota L. cv. Santanet) were irradiated by continuous light of different wavelengths (white, blue, green, red, far‐red and He‐Ne laser) and different power density. Free radical output was measured using Electron Spin Resonance spectra (ESR). The dependence of the content of free radicals (FR) on the light power density was established. The yield of FR in the seeds irradiated with monochromatic light of the same power density was inversely proportional to the wavelength. The ESR spectra showed maximum absolute number of FR for white light. Successive irradiations gave cumulative effects on the output of free radicals in both directions: increase by the action of white light and decrease by the action of red and far‐red light. The contact of irradiated seeds with steam decreased the amount of FR.
Metabolism of diclofop‐methyl in cell cultures of Avena sativa and Avena fatua
Authors: Dusky J. A. , Davies D. G. , Shimabukuro R. H.
Published: April 2006

The metabolism of the herbicide, diclofop‐methyl (methyl‐2‐[4‐(2′, 4′‐dichlorophenoxy) phenoxy]propanoate), in cell suspension cultures of Avena sativa L. (cv. Garry) and in callus of Avena fatua L. (transferred to liquid) was determined as a function of time (8 h to about 3 weeks) and was compared to previous metabolism data from intact plants. A. fatua metabolized 14C‐labeled diclofop‐methyl more rapidly than A. sativa, but the metabolites formed were similar if not identical. Within 2 days, approximately 50% of the total 14C recovered was in A. fatua cells whereas less than 15% was in A. sativa cells. In older cultures of A. fatua, the amounts of 14C in the cells and in the medium were about 45% each; 10 to 12% was in the non‐extractable cell residue. The 14C recovered from A. sativa cells increased to a maximum of about 35% at 7 days and then slowly decreased to about 18% by 21 days, whereas the 14C in the medium of A. sativa decreased to about 60% at 7 days and then increased to over 75% by 21 days. The nonextractable 14C residue was 5% or less even after 21 days. Major metabolites in methanolic extracts of cells of both A. sativa and A. fatua were diclofop (2‐[4‐(2′, 4′‐dichlorophenoxy)phenoxy] propanoate), diclofop hydroxylated at an undetermined position on the 2,4‐dichlorophenyl ring (ring OH‐diclofop), and conjugates of diclofop and ring‐OH diclofop.
An enzyme‐immunoassay for cis‐(+)‐abscisic acid
Authors: Weiler Elmar W.
Published: April 2006

A solid‐phase enzyme‐immunoassay for abscisic acid and abscisic acid conjugates in fmol amounts (detection limit ca 50–60 fmol) has been developed. Only little procedural effort is required for the assay which can be completed within 6 h. With this method, abscisic acid was detected in a range of heterotrophically growing plant suspension cultures. In addition, abscisic acid‐glucosyl ester was identified in a Lonicera prolifera Rehd. tissue culture. In this tissue, the level of free abscisic acid reaches ca 2 × 10−6M in the late log‐phase of growth.
Vegetative growth and frost hardiness of cloudberry (Rubus chamaemorus) as affected by temperature and photoperiod
Authors: Kaurin Åse , Stushnoff Cecil , Junttila Olavi
Published: April 2006

The effect of photoperiod and temperature on growth and induction and development of frost hardiness in cloudberry (Rubus chamaemorus L.) was examined in two experiments. The photoperiods were 8, 12 or 24 h and the temperatures were 18, 15, 12, 9, 4, 3, –3 or –4°C depending on the experiment. The level of hardiness was expressed as LT66 or LT50 (the lethal temperature for 66 or 50% of the plant material) for percentage of bud break and for the degree of coloring by triphenyltetrazolium chloride for rhizomes. The vegetative growth was clearly affected by daylength; petiole elongation, leaf growth, shoot dry weight and number of shoots per plant were all reduced under short days compared with long days. However, the photoperiod had no significant effect on hardening of buds or rhizomes. Hardening increased with successively decreasing temperatures. To get the maximum hardiness, plants had to be exposed to freezing temperatures.
A precursor of the reserve‐protein, phaseolin, is transiently associated with the endoplasmic reticulum of developing Phaseolus vulgaris cotyledons
Authors: Bollini Roberto , Van der Wilden Willem , Chrispeels Maarten J.
Published: April 2006

Developing cotyledons of Phaseolus vulgaris L. were labeled for 30 min with [3H] amino acids, homogenized, and the proteins fractionated on sodium dodecylsulfate (SDS) polyacrylamide gels. Fluorographs of these gels showed that the polypeptides of phaseolin, the major reserve protein of P. vulgaris, were synthesized as precursors which could be distinguished from the polypeptides of mature phaseolin by their slightly lower mobility.

When extracts of cotyledons labeled for 45 min with [3H] amino acids were fractionated on isopynic sucrose gradients, radioactive phaseolin banded at the same density (1.14 g cm‐3) as the endoplasmic reticulum (ER)‐marker enzyme NADH‐cytochrome c reductase. Fractionation in the presence of 3 mM MgCl2 indicated that the newly‐synthesized phaseolin was associated with the rough ER. Pulse‐chase experiments showed that phaseolin was transiently associated with the ER, and later accumulated in the protein bodies.

Treatment of isolated ER with proteinase K showed that phaseolin polypeptides were degraded only if Triton X‐100 was present, indicating that phaseolin was membrane‐protected, probably enclosed within the vesicles. ER‐associated phaseolin associated to an 18S form at pH 4.5 in the presence of 0.3 M NaCl and 100 mM sodium acetate. The polypeptides of ER‐associated phaseolin had a slightly lower mobility on SDS‐gels than polypeptides of protein body phaseolin. ER‐associated phaseolin had a carbohydrate content of 6.8%, while protein body‐derived phaseolin had a carbohydrate content of 6.2%. When cotyledons were labeled simultaneously with [14C] amino acids and [3H] glucosamine or with [14C] amino acids and [3H] mannose, the [3H]/[14C] ratio of ER‐derived phaseolin was similar to that of protein body derived phaseolin, indicating that the faster mobility on SDS‐gels was not due to the detachment of carbohydrate. Experiments in which the carbohydrate side chains were removed with endoglycosidase H, and the resulting polypeptides subjected to electrophoresis in SDS‐gels showed that the differential mobility of the glycopolypeptides of phaseolin resided in their polypeptide chains.
Kinetics of nitrate uptake by different species from nutrient‐rich and nutrient‐poor habitats as affected by the nutrient supply
Authors: Van de Dijk Siebren J. , Lanting Lineke , Lambers Hans , Posthumus Freek , Stulen Ineke , Hofstra Rinie
Published: April 2006

The species Urtica dioica L., Plantago major ssp. major L., Plantago lanceolata L., Hypochaeris radicata L. ssp. radicata and Hypochaeris radicata ssp. ericetorum Van Soest were grown under high and low nutrient conditions (1/4 Hoagland and 2% of 1/4 Hoagland further called the 100% and 2% treatment, containing 3.75 mM NO‐3 and 0.075 mM NO‐3, respectively). After a certain period half of the plants were transferred from low to high or high to low nutrients, yielding the 100%/2% and the 2%/100% treatments. The kinetics of nitrate uptake in the range of system I of the five species grown under the different nutrient conditions were measured during a three week experimental period. The nitrate uptake of all the species showed the characteristic features of Michaelis‐Menten kinetics. Under low nutrient conditions the apparent Vmax of U. dioica expressed per g dry root was lower than under high nutrient conditions. For H. radicata ssp. radicata and for H. radicata ssp. ericetorum the reverse was found. The Vmax values of P. major ssp. major were almost the same for the two treatments. The apparent Vmax in young plants of P. lanceolata was higher in the 100% treatment than in 2%; whereas the reverse was found in mature plants. The results are explained in relation to the relative growth rate, the shoot to root ratio and the natural environment of the species. The apparent Km values were not influenced by the different treatments. Differences in Km between the species, if any, were very small. It is suggested that the Vmax is a more important parameter for the distribution of plant species in the field than the Km. The rate of nitrogen accumulation was calculated from growth data and the contents of nitrate and reduced nitrogen. It is concluded that the Vmax of system I for nitrate uptake in most cases was sufficient to explain the observed growth rates.
Re‐evaluation of proposed C4 photosynthetic characteristics in the genus Larix
Authors: Richards J. H. , Teeri J. A.
Published: April 2006

It has been suggested previously that Japanese larch (Larix kaempferi) exhibits characteristics of C4 photosynthesis. To further evaluate this suggestion, stable carbon isotope ratios were determined for leaf and bark tissue of Larix gmelini, L. kaempferi, L. laricina, L. Iyallii, L. occidentalis, and L. sibirica. All δ13C values were more negative than –22‰. Short‐term labeling with 14CO2 showed that phosphoglyceric acid and other phosphorylated compounds were the first products of photosynthesis in L. sibirica. Both of these results strongly suggest that the initial fixation of atmospheric CO2 in these six Larix species is accomplished solely via the C3 photosynthetic pathway.
A mechanism for multiphasic uptake of solutes in plants
Authors: Sabater Bartolomé
Published: April 2006

A molecular mechanism is proposed for unitary multiphasic uptake in which the carrier has two binding sites for the substrate. The first site binds n‐1 molecules of substrate, and then one additional substrate molecule can become bound at the second binding site. Only this last molecule is transported in the operation of the carrier molecule. In the free state, the carrier can be activated to successive states with increasing affinities for the substrate in the two binding sites. The mechanism is resolved for the steady state conditions, obtaining a simple uptake rate equation, which fits the experimental data. Methods for determining the parameters of the equation are presented. Evidence other than kinetics is discussed for the mechanism. The mechanism also provides a physiological interpretation for multiphasic uptake: the active transport mechanisms (energy‐requiring mechanisms) are prevented from operating at high substrate concentrations, thus preventing a waste of energy by the cells.
Changes in abscisic acid and proline levels in maize varieties of different drought resistance
Authors: Ilahi Ihsan , Dörffling Karl
Published: April 2006

Four varieties of maize differing in drought resistance and geographical origin (Swabi White and Shaheen from Pakistan, Garbo and Goldprinz from Germany) were analyzed for their proline and abscisic acid (ABA) accumulation during a prolonged water stress period. Proline levels increased continuously during the stress period in all the four varieties, but to different amounts. The drought‐susceptible varieties Shaheen and Goldprinz produced higher levels of proline than the drought‐resistant varieties Swabi White and Garbo. A negative correlation was also found between maximal ABA contents and degree of drought resistance during prolonged stress of younger plants. ABA levels did not increase steadily, but reached a maximum long before the end of the stress phase, and then declined. The results are discussed in relation to the possibility of using proline and ABA levels as biochemical indicators of resistance against drought.
The inhibitory effect of gibberellic acid on flowering in Citrus
Authors: Guardiola J. L. , Monerri C. , Agusti M.
Published: April 2006

The application of gibberellic acid (GA3) at any time from early November until bud sprouting, resulted in a significant inhibition of flowering in the sweet orange [C. sinensis (L.) Osbeck] and the Satsuma (C. unshiu Marc.) and Clementine (C. reticulata Blanco) mandarins. Two response peaks were evident: the first occurred when the application was timed to the translocation of an unknown flowering signal from the leaves to the buds. The second occurred during bud sprouting, at the time the flower primordia were differentiating. From the pattern of flowering, it appears that the mechanism of inhibition was similar irrespective of the timing of GA3 application. There was an initial reduction in bud sprouting affecting selectively those buds originating leafless inflorescences. An additional inhibition resulted in a reduction in the number of leafy inflorescences with an increase in the number of vegetative shoots, suggesting the reversion of a floral to a vegetative apex. The inhibited buds sprouted readily in vitro but invariably vegetative shoots were formed. A continuous influence of the sustaining branch is necessary to keep the flowering commitment of the buds; irreversible commitment occurs when the petal primordia are well differentiated.
Promotion of hypocotyl elongation in loblolly pine (Pinus taeda L.) by indole‐3‐acetic acid
Authors: Carpita Nicholas C. , Tarmann Kathleen M.
Published: April 2006

Elongation of excised loblolly pine (Pinus taeda L.) hypocotyls was promoted by indole‐3‐acetic acid and the fungal metabolite, fusicoccin. Gibberellic acid, kinetin, zeatin, or zeatin‐riboside were either without effect or promoted elongation only slightly. The most auxin‐responsive tissue was just below the cotyledonary node, and elongation was confined to sections excised from the upper 2 cm of the hypocotyl. Indole‐3‐acetic acid induced elongation rates in the hypocotyl sections equal to those of intact hypocotyls when the sections were excised from young seedlings. Elongation rates decreased in intact hypocotyls before the excised tissues lost responsiveness to the auxin. Hypocotyl elongation in loblolly pine is discussed in relation to hypocotyl elongation in angiosperm species.
Characterization and comparison of membrane‐bound Na, K, Mg‐ATPase from tissues of Hordeum vulgare L. and Halocnemum strobilaceum L.
Authors: Vakhmistrov D. B. , Tikhaya Natalia I. , Mishustina Natalia E.
Published: April 2006

The effect of Mg2+, Na+, K+, ouabain and pH on ATPase activity of purified membrane fractions enriched in plasmalemma fragments from Hordeum vulgare L. (glycophyte) and Halocnemum strobilaceum L. (halophyte) was studied. Membrane ATPases from both plants were synergistically activated by K+ and Na+ in the presence of Mg2+. The maximum activity of the enzymes were observed at the ratio Na/K = 2–3. Ouabain (10‐4 M) almost completely eliminated the (Na++ K+)‐stimulated component of the ATPase activity. The Na, K, Mg‐ATPase of Hordeum had a single pH optimum (pH 8), but that of the Halocnemum had two optima(pH 6 and 8). It appears that similar enzymes operate in the cells of both plants studied. The higher Na, K, Mg‐ATPase activity of the halophyte compared to that of the glycophyte suggests the involvement of the enzyme in the extrusion of Na+ from the cytoplasm of cells of both plants.
On the possible site of inhibition of photosynthetic electron transport by ultraviolet‐B (UV‐B) radiation
Authors: Noorudeen A.M. , Kulandaivelu G.
Published: April 2006

In Amaranthus chloroplasts that are exposed to ultraviolet‐B (UV‐B) radiation, the electron flow from water to dichlorophenol indophenol (DCPIP) was inhibited, but the electron flow from reduced DCPIP to methyl viologen remains unaffected. Diphenylcarbazide was ineffective in restoring the activity of DCPIP Hill reaction in UV‐B irradiated chloroplasts. Electron flow from water to ferricyanide or dichloro‐dimethoxy‐p‐benzoquinone was inhibited to a degree similar to that of the DCPIP Hill reaction.

The rate of carotenoid photobleaching in the presence of carbonyl cyanide‐m‐chlorophenylhydrazone, an indicator of the photochemical reaction near the vicinity of reaction centre of photosystem II, was suppressed and paralleled with the inhibition of the DCPIP Hill reaction.

In the UV‐B treated chloroplasts, the variable part of the fluorescence transient was diminished. Though the fluorescence yield was lowered by the UV‐B radiation, addition of 3‐(3,4‐dichlorophenyl)‐l, l‐dimethylurea (DCMU) and/or sodium dithionite increased the emission markedly. With the increase in the dosage of UV‐B irradiation, the time required to reach the steady state fluorescence level became longer in the absence of DCMU and shorter in the presence of DCMU. The kinetics of 520 nm absorbance change was markedly unaltered by the UV‐B irradiation but its dark decay was prolonged. It is concluded that UV‐B irradiation inactivates the photosystem II reaction centre.
Dynamics of extractable carbohydrates in Pisum sativum. III. The effect of IAA and temperature on content and translocation of carbohydrates in pea cuttings during rooting
Authors: Veierskov B. , Andersem A. Skytt
Published: April 2006

The number of roots formed in cuttings of pea (Pisum sativum L. cv. Alaska) was regulated both by the temperature and by IAA, whereas the time to the appearance of the first roots was regulated only by the temperature. Cuttings treated with 10‐3M IAA had a smaller content of extractable carbohydrates than the control ones irrespective of the temperature. In the bases of cuttings rooted at 25°C the content of extractable carbohydrates was lower than in those rooted at 15°C. Cuttings treated with IAA showed up to elevenfold increase of extractable carbohydrates in the bases at day 3. This increase of soluble sugars was not correlated with the number of roots formed or the speed of rooting. It is concluded that IAA affects the accumulation of carbohydrates, and this is not connected with the rooting ability of the cuttings.
Physiological studies on pea tendrils. XII. Effects of temperature on contact coiling and uncoiling
Authors: Riehl T. E. , Jaffe M. J.
Published: April 2006

When excised tendrils of pea (Pisum sativum L. cv. Alaska 2B) are mechanically perturbed and allowed to coil at different constant temperatures, the greatest amount of coiling occurs between 27°C and 33°C. Coiling of tendrils continues for about 2 h after mechanical perturbation at which time uncoiling usually begins. The temperature at which the rate of uncoiling is greatest appears to be influenced, at least in part, by the temperature at which the tendrils coiled. For example, when tendrils coil at 20°C their rate of uncoiling at 20°C is less than if they had coiled at 23°C. Estimated activation energies for the uncoiling process are greater than for coiling, with 35 J/mol × s and 97 J/mol × s for uncoiling in the temperature ranges 18°C to 23°C and 10°C to 18°C, respectively. The estimated activation energy for coiling is 5.4 J/mol × s. It is suggested that the process of tendril uncoiling, as well as tendril coiling, might be an active, energy requiring process.

When mechanically perturbed tendrils are placed in the cold (5°C) they do not coil. But this interruption of the coiling process with a cold (5°C) treatment, either immediately after mechanical perturbation or after coiling has begun, does not prevent coiling from continuing after tendrils are again given a more suitable temperature. It is concluded that the cessation of coiling during the cold period may be due to a slowdown in metabolism. It is suggested that there may be a factor which is responsible for the motor response and which is retained during the cold treatment.
Physiological studies on pea tendrils. XIII. Respiration is necessary for contact coiling
Authors: Riehl T. E. , Jaffe M. J.
Published: April 2006

When 9 day old light grown pea (Pisum sativum L. cv. Alaska 2B) plants are irrigated for 4–6 days with 50 μM 4‐chloro‐5‐(dimethylamino)‐2‐(α, α, α‐trifluoro‐m‐totyl)‐3(2H)‐pyridazinone, designated San‐6706, the new leaves and tendrils grow morphologically normal, but with neither chlorophyll nor the ability to carry out photosynthesis. Excised tendrils from these plants coil in response to rubbing as well as those from water irrigated controls. Tendrils from San‐6706 irrigated plants, which have been dark adapted for 2 or 3 days, proceed to coil when illuminated, just as do those from water irrigated plants. Rubbing of dark adapted tendrils results in an increased respiration rate over the first hour or two, when most of the coiling response occurs. Inhibitor studies indicate that blockage of oxidative phosphorylation, but not of the alternative, cyanide‐insensitive, path of respiration, results in a failure of tendrils to coil in response to mechanical perturbation. It is concluded that the normal path of respiration, perhaps via ATP production, may be necessary for thigmosensory perception leading to contact coiling in pea tendrils.
Inhibition of the amino‐acid co‐transport carrier of Lemna gibba by incorporation ofp‐fluorophenylalanine
Authors: Jung K.‐D. , Lüttge U.
Published: April 2006

In Lemna gibba L. a 2 h pretreatment with the amino‐acid analogue p‐fluorophenylalanine p‐FPA inhibited subsequent uptake of L‐alanine and reduced the transient depolarization of the plasmalemma caused by L‐alanine. Uptake of 3–0‐methylglucose was less affected. There was no effect of p‐fluorophenylalanine on the resting potential or on the fusicoccin‐ or light‐dependent hyperpolarization of the cells. Furthermore, fusicoccin‐stimulation of uptake of L‐alanine and 3–0‐methylglucose was also unaffected. The results suggest that p‐FPA pretreatment selectively acts on the H+‐amino‐acid co‐transport carrier, that the H+‐hexose co‐transport carrier is much less affected, and that the proton pump appears to be unaffected by p‐FPA.
The prevention of dehydration injury in celery seeds by polyethylene glycol, abscisic acid, dark and high temperature
Authors: Biddington N. L. , Brocklehurst P. A. , Dearman A. S. , Dearman Jane
Published: April 2006

Celery seeds (Apium graveolens L.) given a germination induction period (3 days imbibition at 17°C in the light) could be prevented from germinating by up to 14 days subsequent exposure to high temperature (32°C), polyethylene glycol (PEG), abscisic acid (ABA) or dark (22°C). When the seeds were returned to 17°C in the light, germination occurred and, except for the high temperature treatment, was more rapid compared to seeds given a germination induction period only.

Celery seeds incubated for 3 days at 17°C in the light and then air‐dried at 20°C germinated slowly when re‐sown at 17°C in the light, and achieved only 19% germination after 21 days. Exposing the seeds to high temperature, PEG, ABA or dark for up to 14 days before drying maintained seed viability and subsequent germination was faster. The longer treatment periods gave increased benefit, and PEG was the most effective treatment. It is suggested that the effectiveness of the treatments in inducing dehydration tolerance relates to their ability to inhibit germination possibly via their prevention of cell expansion.
Effect of water deficits on transpiration, photosynthesis and leaf conductance in cassava
Authors: Ike I. F.
Published: April 2006

Transpiration, net photosynthesis and leaf conductance decreased when leaf water potential dropped below ‐0.30 MPa. Both transpiration and net photosynthesis rates were considerably reduced before the leaves were visibly wilted at ‐0.95 MPa. Consequently, visual symptoms are unlikely to provide a useful index for characterizing water deficits in cassava (Manihot esculenta Crantz cv. Llanera). Decreases in net photosynthesis closely followed decreases in transpiration and this suggests that stomatal closure controls both processes.