bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein synthesis during the transition from the resting to the growing state in suspension cultures of Paul's Scarlet rose cells
Authors: Fosket Donald E.
Published: April 2006

Cells derived from Paul's Scarlet rose (Rosa sp.) were grown in the chemically defined medium of Nesius. When a stationary phase culture was diluted with fresh medium, growth was initiated after a pronounced lag period. DNA replication, as revealed by thymidine labeling and autoradiography, did not begin until 36 h, and mitotic figures were not observed until 48 h after dilution. A 10–15 fold increase in the rate of protein synthesis occurred during the lag period. This was brought about by a 3.5 fold increase in the amount of ribosomal RNA per cell, plus a doubling of both the percentage of ribosomes that are present as polyribosomes and the average number of ribosomes per polyribosome. The spectrum of polypeptides synthesized by these cells during the lag and early log periods of growth was examined. Polyribosomes were extracted from the cells at intervals preceding and accompanying the initiation of proliferative growth. The polyribosomes were translated in a wheat germ cell‐free protein synthesizing system and the 35S‐methionine‐labeled translation products were separated on polyacrylamide slab gels and by 2‐dimensional gel electrophoresis. Comparatively few differences were observed between stationary phase, lag phase and log phase cells in terms of the spectrum of polypeptides synthesized in vitro. However, these various phases of the growth cycle could be characterized by a relatively high rate of synthesis of a few specific polypeptides. That is, while most proteins are synthesized throughout the growth cycle and even in non‐growing cells at approximately the same relative rates, there are a few variable proteins whose synthesis marks a particular phase of the growth cycle.
Genotype, ploidy and physiological state in relation to isoperoxidases in Nicotiana
Authors: Trinh T. H. , Gaspar Th. , Tran Thanh Van K. , Marcotte J. L.
Published: April 2006

Peroxidase and isoperoxidase patterns of tobacco have been comparatively analyzed in relation to parental origin and ploidy level (including hypohaploidy status) at different ages and physiological states. The interspecific hybrid N. sylvestris × N. tomentosiformis shows an additive pattern of parental peroxidases, which also resembles that of N. tabacum cv. Wisconsin and cv. Samsun. Enzyme activity (on dry weight and protein bases, decreases from the diploid to the hypohaploid forms of Wisconsin and Samsun with respective quantitative differences in the zymograms, when the plants are compared at the same chronological and vegetative stages. Abnormally vegetatively ageing hypohaploids recover all peroxidasic isoenzymes and reach an enzyme activity as high as those of haploids and diploids. Flowering hypohaploids, however, generally behave like haploids and diploids in changing their balance between acidic and basic peroxidases.
Effect of di‐n‐butylphthalate on the carotenoid synthesis in green plants
Authors: Virgin Hemming I. , Holst Ann‐Marie , Mörner Johan
Published: April 2006

Vapour of di‐n‐butylphthalate in light produces disturbances in the carotenoid synthesis of green plants (Raphanus, Browallia, a.o.), resulting in chlorophyll deficiency and in extreme cases completely chlorophyll free leaves having a white colour. Absorption spectra of hexane extracts of such leaves, show the presence in higher concentrations than in normal leaves of a pigment with peak positions matching those of phytoene. In such leaves carotenes and xanthophylls are more or less completely lacking. Electron micrographs of white leaves reveal deepgoing changes in the chloroplast structures. The membranes of the grana are irregularly spread over the section areas and the plastoglobules swollen.
Reliable plantlet formation from embryos and seedling shoot tips of radiata pine
Authors: Horgan Kathryn , Aitken Jenny
Published: April 2006

A method has been devised for the reliable production of plantlets from embryos and seedling shoot tips of Pinus radiata D.Don (radiata pine). Buds were induced on an agar or liquid Schenk and Hildebrandt (SH) medium containing 5.0 mg/l benzylaminopurine (BAP). Except for some abnormal buds, the buds grew into elongated shoots on an agar SH medium without cytokinin. The transfer of shoots from a SH medium to a Gresshoff and Doy (GD) medium was found to be an important pretreatment which increased the survival of the shoots when they were placed in a peat and pumice mix for root formation. Elongated shoots were induced to form roots under non‐sterile conditions in a humid environment with occasional misting. An intervening 5‐day treatment of shoots in an agar medium containing 2.0 mg/l indolebutyric acid (IBA) and 0.5 mg/l napthaleneacetic acid (NAA) significantly increased the percentage of shoots forming roots and the number of roots formed per shoot over control shoots placed directly in the peat:pumice mix. An enhanced level of CO2 during root formation had no effect on the time of root formation or on the percentage of shoots forming roots. These results concerning the elongation, growth and rooting of adventitious shoots are now being applied to the development of very large numbers of plantlets starting from cotyledons from partially germinated seeds.
Modulation of the oscillatory system involved in polar transport of auxin by other phytohormones
Authors: Wodzicki Tomasz J. , Wodzicki Alina B.
Published: April 2006

A wave‐like pattern of the basipetal efflux of natural auxin from the cambial region of a series of consecutive short sections of stems of Larix decidua Mill., Acer pseudoplatanus L. and Picea abies (L.) Karst. has been demonstrated as it was earlier reported for Pinus silvestris L. Apical application of ABA suppressed the IAA‐stimulated increase of the auxin‐wave amplitude, and zeatin or GA3 prevented this repression in stem segments of Pinus silvestris. All the exogenously applied substances were highly effective in physiological concentrations. Already 20‐min of exposure to IAA or ABA at the apical end produced modulations of the auxin‐wave along the whole 6.6 cm long stem segment. Application of 2, 3, 5‐triiodobenzoic acid (TIBA) caused suppression of the wave‐like pattern of auxin efflux similarly as ABA, supporting the association of the modulatory effects of ABA with the phenomena involved in polar transport of auxin. Abscisic acid applied to the basal end of the stem segment also reduced the auxin‐wave amplification caused by simultaneous supply of IAA to the apical end. This finding additionally confirms the hypothesis that: 1) the supracellular auxin‐wave generation is associated with the functioning of a system of oscillators coupled at the cellular level and 2) the auxin‐wave modulations can be propagated acropetally, that is against the main direction of the auxin molecular transport.
Does osmotic regulation of amylase activity in bean cotyledons exist?
Authors: Gepstein S. , Ilan I.
Published: April 2006

The hypothesis that the promotive effect of the embryo axis of the germinating bean seed on amylase activity in the cotyledons is mediated by an osmoregulative mechanism was examined. After 2 days of germination the action of the axis on amylolytic activity was already clearly revealed, whereas at the same time it did not have any influence on osmotic pressure in the cotyledons. When the axis was attached to one cotyledon during 4 days of incubation, osmotic pressure in the cotyledon was lower than its value in the cotyledons of the intact seedling, whereas amylolytic activity was similar in both treatments. It was concluded that the tested hypothesis is not valid in the case of the bean seedling. External osmotic agents brought about a decrease in the level of amylase in the cotyledons, but this does not prove that osmotic changes which are brought about by production of internal metabolites are involved in the regulation of amylase synthesis.
In vitro initiation of adventitious structures in relation to the abscission zone in needle explants of Picea abies: anatomical considerations
Authors: Jansson Eva , Bornman Chris H.
Published: April 2006

A comparison of the regeneration potential of needles of different ages in Picea abies emphasized the importance of taking into account the manner of explantation as well as the state of differentiation of the abscission zone. Generally, response in terms of initiation of adventitious structures decreased progressively not only with needle age (5 to 10 to 15 mm long) but also with the distance from the abscission zone towards the tip, that is, distally. On a bud‐induction medium adventitious shoot but primordia were produced proximally and distally (except for the very tip) of the weakly‐developed abscission zone in needles ca. 5 mm and shorter. In needles between 5 and 10 mm long the various cell types of the abscission zone commenced differentiation, and adventitious structures (shoot bud and other primordia) were formed proximal and immediately distal to it. In needles ca. 15 mm long, in which the abscission zone's hyaline, separation and protective layers became well‐developed and where senescence of the distal part commenced, response was limited to proximal tissues. Divisions giving rise to adventitious primordia distal to the abscission zone arose from epidermal cells proper and, in a more acropetal position, also from subsidiary cells of the stomata. Cells of the hypodermis contributed only in the near‐distal region of the abscission zone in younger needles, and before commencing differentiation into fibres.

When excised carefully, the explant consists of a leaf plus a peg‐like cushion of axillary, meristematic tissue proximal to the abscission zone and capable of ready regeneration. In view of the apparent relationship between age and the stage of development of the abscission zone, it was concluded that there exists a critical needle length which should not be exceeded when attempting in vitro induction of organ primordia.
Growth, photosynthesis and respiration in Plantago coronopus as affected by salinity
Authors: Blacquière Tjeerd , Lambers Hans
Published: April 2006

Plantago coronopus was grown in a non‐saline culture solution and in a culture solution containing 50 mM NaCl. The rates of dry matter accumulation in both roots and shoots were not affected by 50 mM NaCl. Photosynthesis, expressed per shoot, was also the same in both environments. Neither the rate of shoot respiration nor that of root respiration was affected by salinity. In both environments the alternative respiratory pathway contributed to the same extent in root respiration. The activity of the alternative pathway decreased with increasing age. Since the respiratory activities were the same in plants grown under both saline and non‐saline conditions and since the alternative respiratory pathway was also equally active in roots under both environmental conditions, it is concluded that respiratory costs involved in growth in 50 mM NaCl are negligible in terms of the plant's total energy costings.
Changes during light and dark osmotic treatment independently modulating germination and ribonucleic acid synthesis in Chenopodium bonus‐henricus seeds
Authors: Khan Anwar A. , Karssen C. M.
Published: April 2006

The content and synthesis of RNA in Chenopodium bonus‐henricus L. seeds in different physiological states were evaluated. A moist‐chilling treatment at 4°C removed the primary dormancy of seeds. A pretreatment of chilled seed in low osmotic potential (–8.6 bars) polyethylene glycol‐6000 solution at 15°C in light led to an advancement in subsequent germination time in water while a treatment in darkness induced a secondary dormancy. The synthesis of total RNA and poly A (+) RNA was correlated with the capacity of seeds to germinate. Cordycepin or α‐amanitin failed to inhibit the germination of unchilled seeds, chilled seeds or chilled seeds given a prior light osmotic treatment. Also, germination of chilled seeds was not affected by cordycepin applied during light osmotic treatment. However, cordycepin effectively depressed the synthesis of both total RNA and poly A (+) RNA in chilled seeds with or without a prior light osmotic treatment. These data suggest that germination per se may depend upon the activation of pre‐existing mRNA, which might be functionally different from the newly synthesized mRNA including poly A (+) RNA.
Habituation in sugarbeet callus: auxin content, auxin protectors, peroxidase pattern and inhibitors
Authors: Kevers C. , Coumans M. , De Greef W. , Hofinger M. , Gaspar Th.
Published: April 2006

A GC‐ECD titration of IAA in normal auxin (2,4‐D)‐requiring and auxin‐independent (habituated) sugarbeet callus revealed an equal amount in both tissues. A comparison of the content and pattern (through starch gel electrophoresis) of soluble, membrane and wall peroxidases indicated that normal tissues contained a higher level of isoperoxidases. Normal tissues also were found to contain higher levels of peroxidase inhibitors and auxin protectors. The hypothesized peroxidase‐mediated higher rate of auxin destruction in normal sugarbeet callus is supposed to be counterbalanced by the 2,4‐D‐controlled auxin protectors.
Relations entre production et localisation de mycosporine et morphogenèses reproductrices chez le Pyrénomycète Gnomonia leptostyla
Authors: Fayret Jacques , Vito Joël
Published: April 2006

Relations between production and localisation of mycosporin and reproductive morphogenesis in the Pyrenomycete Gnomonia leptostyla.

The production of mycosporin (P310) has been analysed in Gnomonia leptostyla (FT.) Ces. et de Not. during mycelial growth and reproductive morphogenesis (macroconidiogenesis, microconidiogenesis and differentiation of perithecia). Conidiogenesis is induced in illuminated cultures while darkness promotes perithecial development. At 20°C, the cultures produce either macroconidia or perithecia with abortive sporophyte. Microconidia differentiation and perithecia maturation require low temperature (10°C). Mycosporin is, at all times, present in the thallus. However, the concentration of mycosporin in highest in the conidiogenous thallus, intermediate in the perithecial thallus. and lowest in the vegetative mycelium. In the conidiogenous thallus, macroconidia and microconidia are both sites of mycosporin accumulation. On the contrary, in the perithecial thallus, mycosporin levels are not higher in perithecia than in mycelia, even during their maturation period. The quantitative variations of mycosporin during the thallus development and its accumulation inside conidia suggest translocation from sites of synthesis towards reproductive cells.
Oak seedlings grown in different light qualities
Authors: Axelsson Lennart , Klockare Birgitta , Sundqvist Christer
Published: April 2006

Oak seedlings (Quercus robur L.) were germinated in darkness for 3 weeks and then given continuous long wavelength far‐red light (LFR; wavelengths longer than 700 nm). A control group of seedlings was kept in darkness. After 2 additional weeks the chlorophyll formation ability in red light was examined in the different seedlings. The stability of the protochlorophyll(ide) and chlorophyll(ide) forms to high intensity red irradiation was also measured.

Oak seedlings grown in darkness accumulated protochlorophyll(ide) (6 μg per g fresh matter). Absorption spectra and fluorescence spectra indicated the presence of more protochlorophyll(ide)628–632 than protochlorophyllide650–657. The level of protochlorophyll(ide) was higher in leaves of plants cultivated in LFR light (13 μg per g fresh matter) than in leaves of dark grown plants. 12% of the protochlorophyll(ide) was esterified in both cases.

The level of protochlorophyll(ide)628–632 in LFR grown oaks varied with the age of the leaves, being higher in the older (basal) leaves, but also in the very youngest (top‐most) leaves. The ability of the leaves to form photostable chlorophyll in red light showed a similar age dependence, being low in rather young and in older leaves. A low ability to form photostable chlorophyll thus appears to be correlated with a high content of protochlorophyll(ide)628–632.

Upon irradiation only the protochlorophyllide650–657 was transformed to chlorophyllide. After this phototransformation the chlorophyllide peak at 684 nm shifted to 671 nm within about 30 min in darkness. This shift took place without any accompanying change in photostability of the chlorophyll(ide). Upon irradiation with strong red light a similar shift took place within one minute. This indicates that the chlorophyllide after phototransformation was rather loosely bound to the photoreducing enzyme. The development towards photostable chlorophyll forms consists of three phases and is discussed.
Influence of auxin on phosphate absorption and metabolism of phosphorylated compounds in aged potato tuber discs (Solanum tuberosum)
Authors: Poder Danielle , Hourmant Annick , Penot Michel
Published: April 2006

Ageing of potato tuber discs markedly increases the rate of phosphate uptake. This increase is partially prevented by the presence of indoleacetic acid (IAA: 50 μM) in the ageing medium. 32P distribution among the various phosphorylated fractions (P1, organic soluble phosphate, acid‐insoluble phosphate) was carried out after 24 h of ageing in the presence of IAA. An equal inhibition of the labelling rates of each of the different fractions is induced by the hormone. No important effect on respiration and ATP content was observed. Moreover, IAA neither changes the total phospholipid content nor the relative distribution of 32P between the components. These results support the hypothesis that IAA acts specifically on the development of uptake mechanisms during the ageing period.
Effectiveness of gibberellins and 6‐benzyladenine on flowering of Arabidopsis thaliana
Authors: Besnard‐Wibaut C.
Published: April 2006

The different phases of development of the apical meristem in two ecotypes of Arabidopsis thaliana (L.) Heynh. [one French (a quantitative long‐day plant), the other one Swedish (an absolutely cond‐requiring plant)] were established, under conditions either inductive or not inductive of flowering. Then the effects of gibberellins (GA3, GA4/7) and cytokinin (6‐BA) on these ecotypes were studied at different stages of their ontogenic development. The rate of plant growth was estimated by measuring the plastochron duration. The activities of the different apical zones were determined with cytochemical methods and by histoautoradiography after incorporation of 3H‐thymidine into DNA. When treated during the vegetative stage, i.e. at a young age (French ecotype) or in absence of cold treatment (Swedish ecotype) flowering was not induced. The tested chemicals had similar effects: at first a stimulation of the phylogenetic activity of the cells of the lateral zone and of the rib meristem and, after extended treatments, a differentiation of the axial cells of the meristem and, as a result, an inhibition of flowering. On the other hand, the different hormonal applications on meristems which have reached the intermediate stage, were effective in inducing the reproductive state. The activity of the central cells already in the process of dedifferentiation was increased and, by this, flowering was promoted.
Microdistribution of manganese in the leaf tissues of different plant species as revealed by X‐ray microanalyzer
Authors: Memon Abdul Razaque , Chino Mitsuo , Hara Kouichi , Yatazawa Michihiko
Published: April 2006

Microdistribution patterns of Mn in the leaf tissues of 9 plant species, Quercus mongolica Fisch. var. grosseserrata Rehd. et Wils., Lindera erythrocarpa Makino, Rhus trichocarpa Miq., Ilex crenata Thunb. var paludosa (Nakai) Hara, Acer sieboldianum Miq., Acanthopanax sciadophylloides Franch. et Savat., Clethra barbinervis Sieb. et Zucc., Pieris japonica (Thunb.) D. Don and Rhododendron semibarbatum Maxim. were studied by means of a wavelength dispersive type X‐ray microanalyzer in conjunction with cryostage. The results showed that Mn, in general, was highly concentrated in the epidermal, palisade and spongy parenchyma cells of the leaf tissues of the investigated plants with optimal Mn supply.
Phytochrome control of hypocotyl extension in light‐grown Chenopodium rubrum
Authors: Holmes M. G. , Wagner E.
Published: April 2006

The regulation of hypocotyl extension in light‐grown Chenopodium rubrum L. seedlings by light analogous to dense vegetation canopy shade has been monitored. Hypocotyl extension was controlled by both the quantity and quality of the actinic light. At the higher of the two background photon fluence rates which were used (10.0 μmol m−2s−1 in the 400–700 nm waveband), increasing the proportion of phytochrome calculated to exist as Pfr resulted in greater inhibition of growth. At the lower photon fluence rate (1.0 μmol m−2s−1 in the 400–700 nm waveband), a biphasic response was observed in which minimum inhibition was observed at intermediate photoequilibria. Although photosynthesis was not directly involved in the photomorphogenetic responses, it did play an indirect quantitative role in determining the response.
Activity and metabolism of 9‐substituted cytokinins during lettuce seed germination
Authors: Pietraface W. J. , Blaydes D. F.
Published: April 2006

The activities of N6‐benzyladenine (BA) and its 9‐substituted methyl, methoxymethyl, tetrahydropyranyl, cyclopentyl, and cyclohexyl analogs were determined for the promotion of lettuce seed (Lactuca sativa L. cv. Grand Rapids) germination. Cytokinin concentrations used were 10−4, 10−5, 10−6 and 10−7M. All seeds were incubated under total dark conditions at 28 ± 1°C. After 48 h the percentage of germination was recorded. A comparison of means based on Duncan's Multiple Range Test allowed for a ranking of cytokinin activities for the promotion of lettuce seed germination. The activities were: BA = 9‐tetrahydropyranyl BA > 9‐methyl BA > 9‐methoxymethyl BA > 9‐cyclopentyl BA > 9‐cyclohexyl BA. The results were significant at the 95% confidence level as determined by analysis of variance. In order to study the metabolism of a cytokinin, lettuce seeds were incubated with 9‐methyl‐BA‐methylene‐14C. The labeled cytokinin was prepared by refluxing benzylamine hydrochloride (methylene‐14C) with an equal molar ratio of 6‐chloro‐9‐methylpurine. Final cytokinin concentration was 10−5M. Incubation periods were 2, 4, 8, 12, 16 and 20 h at 28 ± 1°C under total dark conditions. At the end of the various time periods the seeds were extracted with 70 percent methanol. The resulting extracts were purified and radioactive metabolites identified by solvent fractionation, Sephadex LH‐20 column chromatography, and paper chromatography. Co‐chromatography with authentic standards in the appropriate solvent system revealed that the metabolites were 9‐methyl BA, N6‐benzyladenosine‐5′‐monophosphate, and N6‐benzyladenosine. The results lend support to the theory that the cytokinin ribonucleotide serves as a storage form which is converted to the active ribonucleoside as needed during lettuce seed germination.
Effects of in vitro treatment with ozone on the physical and chemical properties of membranes
Authors: Pauls K. P. , Thompson J. E.
Published: April 2006

Treatment of microsomal membranes from cotyledons of Phaseolus vulgaris with ozone raises the liquid‐crystalline to gel lipid phase transition temperature and results in the formation of distinct domains of gel phase lipid in the membranes. Liposomes prepared from the total lipid extracts of ozone‐treated membranes undergo phase separations just a few degrees below the transition temperature for intact membranes, indicating that the formation of gel phase lipids is largely attributable to ozone‐induced alterations in the membrane lipids. Levels of unsaturated fatty acids as well as the sterol to phospholipid ratio are markedly reduced in the ozone‐treated membranes, and the neutral lipid fraction from treated membranes shows, an increased propensity to induce the formation of gel phase phospholipid when incorporated into liposomes of egg phosphatidylcholine. Since gel phase phospholipid also forms in naturally senescing plant membranes and appears to be attributable to changes in the neutral lipid fraction, the effects of natural senescence and ozone on membranes have been compared.
Soaking injury and its reversal with polyethylene glycol in relation to respiratory metabolism in high and low vigor soybean seeds
Authors: Woodstock Lowell W. , Taylorson Raymond B.
Published: April 2006

Germination and growth of unaged (high vigor) and accelerated aged (41°C and 100% RH for 4 days; low vigor) soybean [Glycine max (L.) Merr. cv. Essex] seeds were severely reduced by soaking the seeds under water at 25°C during the first 1 to 8 h of imbibition. Soaking in 30% polyethylene glycol (PEG) did not injure high vigor seeds and improved the performance of low vigor seeds. Soaking in water increased subsequent RQ values and acetaldehyde and ethanol levels. In high vigor seeds, the increase in RQ lasted only 1 h after transfer to aerobic conditions, whereas in low vigor seeds the increase persisted into the second h. Increases in ethanol and acetaldehyde after soaking were more pronounced in low than in high vigor seeds. The data indicate that relatively short periods under water can cause water uptake injury to imbibing soybean seeds and that this injury can be avoided by osmotically reducing the initial rate of water uptake. Seeds whose vigor has declined during accelerated aging show an additional injury which increases with soaking duration and involves alterations in respiratory metabolism including accumulation of acetaldehyde and ethanol to high, and possibly toxic, levels during imbibition.
Cytokinins in germinating maize caryopses
Authors: Van Staden J.
Published: April 2006

The transport and metabolism of 8[14C]t‐zeatin applied to the embryonic axis and radicle tip of Zea mays L. caryopses was studied. As in the endosperm side‐chain oxidation rather than side‐chain modification (glucosylation) was the predominant way in which applied zeatin was metabolised in the metabolically more active embryonic axis. Within this tissue there was also evidence for a second form of metabolism which involved modifications to the adenine ring. No clear evidence for an embryo‐endosperm interactions of cytokinins during the course of germination process could be found.
The directional control of sucrose and asparagine transport in lupin by abscisic acid
Authors: Porter N. G.
Published: April 2006

Injections of exogenous abscisic acid into the primary flowerhead of Lupinus luteus cv. Weiko III reduced the movement of 14C‐sucrose into the flowerhead from the uppermost leaves. Sucrose transported from below the lateral branches subtending the flowerhead, was diverted into the lateral branches by injection of the exogenous abscisic acid into the flowerhead. 14C‐sucrose was also diverted from a lateral branch injected with exogenous abscisic acid to all other parts of the plant, particularly the main stem and leaves, and the roots. Transport of 14C‐asparagine administered at the cotyledonary node was directed from the flowerhead into the subtending lateral branches by injection of abscisic acid into the flowerhead. Transport of both 14C‐sucrose and 14C‐asparagine into the flowerhead was reduced at least three fold at physiological levels of abscisic acid. No significant correlation was found between the amount of 14C‐asparagine entering a sink and the dry weight of the tissues of that sink. It is concluded that distribution of 14C‐sucrose and 14C‐asparagine between the flowerheads and lateral branches of L. luteus is actively and dynamically controlled and that abscisic acid levels play a significant part in that control. It is suggested that the relative levels of endogenous abscisic acid in plant organs could serve as an important factor in the directional control of assimilate transport in plants.
Growth and development of Citrus pistils and fruit explants in vitro
Authors: Gülsen Yücel , Altman Arie , Goren Raphael
Published: April 2006

Pistils and various fruit explants of Citrus limon L. Burm. f. and Citrus sinensis L. Osbeck were cultivated in vitro. Basal medium as well as medium supplemented with IAA, GA3 or benzylaminopurine, supported growth of all explants for more than one year. Pistils did not enlarge considerably, but gave rise to active callus growth; callus proliferation and viability was enhanced by all hormones. Culture of fruit slice explants resulted, in addition to peel hypertrophy and callus proliferation, in a marked growth of two distinct types of juice vesicles. The growth of juice vesicle explants was promoted by all three growth hormones. – It is suggested that the successfully prolonged in vitro culture of various fruit explants, and especially of juice vesicles, may aid in studies of fruit development and physiology.
Biosynthesis of stress ethylene in soybean seedlings: Similarities to endogenous ethylene biosynthesis
Authors: Hogsett W. E. , Raba R. M. , Tingey D. T.
Published: April 2006

The similarity of stress ethylene biosynthesis in whole plants to endogenous ethylene biosynthesis was investigated using two inhibitors of ethylene biosynthesis, aminoethoxyvinylglycine (AVG) and cobalt chloride (Co2+); and the intermediates, methionine, S‐adenosylmethionine (SAM), and 1‐aminocyclopropane‐1‐carboxylic acid (ACC), of basal ethylene biosynthesis. Stress ethylene production induced by ozone, cadmium, or 2,4‐dichlorophenoxyacetic acid was inhibited in hydroponically‐grown soybean seedlings in a concentration‐dependent manner by both AVG and CO2+. The ethylene intermediates evoked responses in intact seedlings similar to that described for endogenous ethylene production in isolated vegetative tissue. The addition of SAM to the hydroponic system relieved AVG inhibition of stress ethylene production. Feeding ACC to the seedlings resulted in increased ethylene production independent of stress application or prior AVG inhibition. Cobalt inhibition of stress ethylene production was relieved by increasing concentrations of ACC. A short lag period of 12–18 min was observed in stress ethylene production following a 30‐min ozone exposure. Addition of cycloheximide partially inhibited ozone‐induced ethylene production.

These results suggest a common pathway in whole plants for stress ethylene production and endogenous ethylene biosynthesis.
Shoot initiation in light‐ and dark‐grown tobacco callus: the role of ethylene
Authors: Huxter Terry J. , Thorpe Trevor A. , Reid David M.
Published: April 2006

Shoot‐forming tobacco (Nicotiana tabacum L. cv. Wisconsin 38) callus produces less endogenous ethylene than non‐shoot‐forming tissue cultured in the light (16 h photoperiod) or the dark. In shoot‐forming tissue more ethylene is produced early in culture (days 0–5) than later. Also dark‐grown tissue produces much more ethylene than light‐grown. On the basis of experiments in which (1) gaseous ethylene was added to or (2) CO2 removed from the flasks, (3) Ethrel (an ethylene releasing agent) and (4) 1‐aminocyclopropane 1‐carboxylic acid (an ethylene precursor) were added to the medium, it was determined that this gaseous phytohormone had two contrary effects on shoot initiation (shoot primordium formation). Early in culture (days 0–5) endogenous or exogenous ethylene inhibited organogenesis, but later (days 5–10) exogenous ethylene or increased endogenous ethylene production speeded up primordium formation.
Heterotrophic tobacco cell cultures during greening
Authors: Brangeon Judy , Nato Aimé
Published: April 2006

Structural changes in cells and plastids are described that occur during the greening of an initially dark‐grown cell suspension of tobacco (Nicotiana tabacum L. cv. Xanthi). The pattern of cell growth during greening, expressed in dry weight or cell number, showed a classical sigmoid curve with a lag phase (T0–T2), an exponential phase (T3–T9) and a stationary phase (T10–T21). Achlorophyllous vacuolated cells (T0), obtained after 3 culture cycles in the dark, contained amyloplasts devoid of lamellae. Exposure to light brought about an enrichment in cytoplasm and an amyloplast to proplastid transformation (starch loss) accompanied by chlorophyll synthesis. By T3, many cells appeared meristematic and contained dividing proplastids with rudimentary single lamellae typical of those in intact meristematic leaf cells. As cell division occurred (T3 to T9), plastids replicated and their internal membrane system developed progressively into defined grana‐intergrana thylakoids. By the stationary phase of cell growth (T14), the lamellar system had reached a highly structured grana‐intergrana network typical of higher plant chloroplasts. We have emphasized the analogies between the sequence of events (proplastid to chloroplast transition) during the greening of tobacco cells and that in developing intact leaves; in this respect the cell cultures provide a useful material for studies dealing with the biogenesis of structural or physiological events.
Heterosis and ion transport in hexaploid varieties of rye‐wheat (triticale) compared to the parental species
Authors: Jensén Paul , Jönsson Ann‐Sofie
Published: April 2006

Important winter and spring varieties of hexaploid rye‐wheat (triticale cvs. 6048 and 5004) were selected for study of heterotic effects on growth and ion transport in the hybrids compared to the parental species rye (Secale cereale L. cvs. MT 77 and Sv 6970) and wheat (Triticum aestivum L. cvs. Starke II and Sonett). After 3 days germination, seedlings were grown 11 days in water culture on a complete nutrient solution diluted to 1, 25 and 50%. Intracellular influx and transport to shoots of K+, Ca2+, sulphur and phosphate were determined by using radioactive tracers (86Rb (for K+), 45Ca, 35S and 32P). Varietal differences in the parameters studied were generally small compared to differences between species. The heterotic effect on growth of rye‐wheat was mainly localized to the shoots at high ionic strengths (25% and 50%). There were no heterotic effects on ion influx or transport to the shoots. Ion influx and transport characteristics in rye‐wheat appear to be inherited mainly from wheat. Growth of all species on 1% medium was severely reduced. At the low ionic strength ion influx was inhibited similarly for all species, except influx of K+ (86Rb) which was higher in rye‐wheat and wheat than in rye. Ion influx and transport in rye‐wheat and wheat and in rye differed especially for 25% and 50% media. Rye had the highest ion influx and transport and the highest shoot/root fresh weight ratio at the high ionic strengths. To feed a comparatively large shoot, rye may compensate for a relatively small root system by efficient ion transport mechanisms.
Rhythmic iron stress reactions in sunflower at suboptimal iron supply
Authors: Römheld V. , Marschner H.
Published: April 2006

Uptake and translocation of labelled iron were studied in sunflower (Helianthus annuus L. cv. Sobrid) grown in nutrient solution with low FeEDDHA concentrations during preculture. In contrast to conditions for plants adequately supplied with iron, suboptimal iron supply leads to temporary Fe stress with rhythmic rates of uptake and translocation of iron (period 2–4 days). This rhythmic behaviour of iron uptake is associated with corresponding changes in morphology (thickening of root tips) and physiology (increase in reducing capacity) of the roots. Iron stress is alleviated within less than one day if sufficient iron is available. This is indicated by normalisation of root morphology, reducing capacity and rate of iron uptake and translocation. This rhythm in iron uptake stresses the importance of rhythmic patterns of biochemical behaviour in complex biological systems. It is suggested that phytohormones are involved in the transformation of the iron nutritional status of the shoot apex into a “signal” for the uptake sites of iron in the roots. Preliminary experiments with sunflower in calcareous soil indicate an ecological importance of this fine regulation mechanism for plants on soil with a low iron availability, manifested in rhythmic iron stress reactions.
Iron deficiency stress induced morphological and physiological changes in root tips of sunflower
Authors: Römheld V. , Marschner H.
Published: April 2006

Typical morphological and physiological changes were observed in iron deficient sunflower (Helianthus annuus L. cv. Sobrid) roots. These changes, or so‐called iron stress reactions, are exclusively confined to the root tips. Typical morphological changes included additional cell division in the rhizodermis layer and enhanced formation of root hairs, leading to an increase in root diameter (“swollen root tips”). These morphological changes were correlated with physiological changes such as increased release of protons, accumulation of phenols in the rhizodermis, and an increased ability of the roots to reduce iron‐III compounds (“reducing capacity”). A marked increase in ability of the root tips to take up and translocate iron occurred simultaneously with these changes. There is good evidence that these morphological and physiological changes are reflections of an effective regulatory mechanism for enhanced mobilization of sparingly soluble iron‐III compounds in the rhizosphere and for iron uptake by sunflower plants.
Isolation and characterization of cytoplasts and miniprotoplasts derived from protoplasts of cultured cells
Authors: Lörz H. , Paszkowski J. , Dierks‐Ventling C. , Potrykus I.
Published: April 2006

We have isolated and partially characterized subprotoplasts containing nuclei, i.e. miniprotoplasts, and enucleated subprotoplasts, i.e. cytoplasts, from freshly isolated protoplasts of cultured cells from Hyoscyamus muticus, Nicotiana tabacum and especially Zea mays. Protoplasts were fragmentated by centrifugation through discontinuous iso‐osmotic density gradients containing colloidal silaca gel (Percoll), calcium chloride and mannitol. Using this method metabolically active miniprotoplasts and highly purified cytoplast fractions with less than 4% contamination with nucleated protoplasts were obtained. The cytoplasts prepared by our method are suitable for use in fusion experiments aimed at transferring nuclear and cytoplasmic genetic information separately.
Cytokinin interaction with free radical metabolism and senescence: Effects on endogenous lipoxygenase and purine oxidation
Authors: Leshem Y. Y. , Wurzburger J. , Grossman S. , Frimer A. A.
Published: April 2006

A typical system comprising xanthine‐xanthine oxidase, which produces superoxide free radicals, significantly increased endogenous levels of the senescence‐associated lipoxygenase enzyme while cytokinin reversed this effect. It is suggested that in its interaction with free radicals cytokinin may have a dual effect: a) it may inhibit purine oxidation by the formation of a 2,8 dihydroxy purine which lowers the substrate affinity of xanthine oxidase; b) it may act as a direct free radical scavenger by virtue of H abstraction from the α‐carbon atom in the amine bond.
Response of 19 cultivars of soybeans to ultraviolet‐B irradiance
Authors: Biggs R. H. , Kossuth S. V. , Teramura A. H.
Published: April 2006

Nineteen soybean cultivars were grown for four weeks in controlled environmental chambers with artificial daylight supplemented by five UV‐B irradiance regimes to determine the range of growth and development responses of seedlings. Data from nine plant characteristics were assessed: leaf area, dry weight of leaves, stems and roots, total plant dry weight, height, ratio of roots to shoots and leaf area to weight and rating of leaves for damage. Significant differences were observed in the responses noted. Stunting, leaf chlorosis and loss of apical dominance were three general symptoms apparent on all cultivars which received UV‐B irradiance. Varying degrees of reduced leaf area and dry weight of the plants and altered ratios of weights of leaves per unit area and weight of roots to shoots were also found. It was concluded that different soybean cultivars demonstrate a marked difference in sensitivity to UV‐B radiation under the artificial conditions of controlled environmental growth chambers and this may indicate a genetic basis for variability in sensitivity of soybean cultivars to this waveband. However, the sensitivity to UV‐B radiation was increased by the lower than normal photon fluence of photosynthetically active radiation (225 μE m−2 s−1).
Low‐molecular‐weight carbohydrates in some salt‐stressed plants
Authors: Gorham J. , Hughes Ll. , Wyn Jones R. G.
Published: April 2006

A study was made of the effects of salinity on the concentrations of free sugars, glycinebetaine, proline and other chemical components of Aster tripolium L., Daucus carota L., Honkenya peploides (L.) Ehr. and Plantago coronopus L. (Dicotyledones); and Carex extensa Good., Eleocharis uniglumis (Link) Schutt., Juncus maritima Lam. and Schoenoplectus tabernaemontani (C. C. Gmel.) Palla (Monocotyledones) grown in the laboratory. In Plantago coronopus the level of the polyol sorbitol increased when the plants were subjected to NaCl stress, while in Honkenya peploides the cyclitol pinitol accumulated. No consistent pattern emerged with respect to the changes in free sugar contents in either the monocotyledonous or dicotyledonous plants, though the monocotyledonous plants generally had higher sugar contents.
The dynamics of indole‐3‐acetic acid in Acer platanoides seeds during stratification and germination
Authors: Tillberg Elisabeth , Pinfield Neville J.
Published: April 2006

During stratification at 5°C indole‐3‐acetic acid (IAA) levels in embryos of Acer platanoides decreased during the early stages but subsequently increased again throughout the remainder of a 144 day period. The reduction in IAA levels in embryos of fruits stored at 17°C was even more pronounced, and in addition, no increase was observed after longer storage periods at this temperature, the levels of IAA remaining very low. Germination in seeds maintained at 5°C was not observed until after 120 days or longer, but germination potential increased at an earlier stage, as shown by the fact that seeds transferred to 20°C gave appreciable increases in germination after much shorter chilling periods. Endogenous IAA levels in embryos from seeds transferred to 20°C after a chilling period, long enough to break dormancy, increased within 24 h, i.e. before visible germination, to levels similar to those observed in embryos from seeds chilled continuously for 144 days. Embryos from seeds chilled for 120 days, i.e. when the samples already showed visible germination and when the endogenous IAA content was already high, showed no further increase in endogenous IAA during a three day incubation at 20°C. None of the treatments employed was effective in inducing germination of seeds or embryos from fruits stored at 17°C.
Biosynthèse de la sticticine chez le lichen Lobaria laetevirens
Authors: Bernard T. , Goas G.
Published: April 2006

Biosynthesis of sticticin in the lichen Lobaria laetevirens (Lightf.) Zahlbr.

Sticticin is the most important soluble nitrogenous compound in the thallus of L. laetevirens from which it was isolated for the first time. As its concentration can exceed 1 M when thallus water content reaches 10–12%, it might play an efficient role in osmoregulation. Its biosynthesis was investigated by supplying the lichen with L‐[U‐14C]tyrosine, DL‐3,4‐dihydroxyphenyl [3‐14C]alanine and L‐[methyl‐14C]me‐thionine. The main pathway involves, first, N‐methylations of tyrosine, then a hydroxylation of the ring and finally an esterification of the acid function.
Effect of pollination or treatment with growth regulators on levels of extractable hormones in tomato ovaries and young fruits
Authors: Sjut Volkert , Bangerth Fritz
Published: April 2006

Levels of extractable free indolyl‐3‐acetic acid (IAA), gibberellin‐like substances (GA's), and abscisic acid (ABA) were analysed in tomato ovaries (Lycopersicon esculentum Mill.) before pollination as well as in fruits 5 and 10 days after pollination or treatment with growth regulators to induce parthenocarpic fruit development. Growth regulators applied were a naphthoquinone (bendroquinone), an auxin (4‐CPA), a morphactin (CME), and a benzothiadiazole (DU).

The initial high levels of ABA (2.7 μg/g dry weight) in unpollinated ovaries decreased to one third or less after 5 and 10 days. In contrast levels of IAA increased from 80 up to 180 ng/g dry weight. Activity of GA's could be detected only in young fruits but not in unpollinated ovaries.

The possible relevance of these findings for tomato fruit‐set is discussed.
Effect of cycloheximide and renewal of phosphorus supply on surface acid phosphatase activity of phosphorus deficient tomato roots
Authors: Boutin Jean‐Pierre , Provot Madeleine , Roux Louis
Published: April 2006

Changes in surface phosphatase activity of tomato root (Lycopersicon esculentum L. cv. Marmande) have been studied in relation to its P status. Experiments were performed either with excised roots cultured in vitro or with entire plants (split root method) grown in various conditions (P deficiency, renewal of P supply). In some experiments different parts of the root were separated according to their P status during their primary growth.

The surface phosphatase in different root parts depends first of all on P status during their primary growth. Moreover the cell wall phosphatase of tomato root is stable in vivo. Thus the changes in the surface phosphatase of a root system result mainly from the growth of new roots, which bear an enzyme activity that is either high if they are P deficient or low if they are P provided. The control of the cell wall phosphatase synthesis appears to be a repression‐derepression process mediated by the root cell concentration in some P compound, probably orthophosphate. Cycloheximide stops or alters the growth of excised roots, so that this inhibitor was found unsuitable to study the synthesis of cell wall phosphatase under in vivo conditions. Split root experiment shows that the increase in surface phosphatase activity may occur locally, i.e. only in the parts of the root system which are P deficient. Agricultural and ecological aspects of these findings are pointed out.
The effects of root decapitation on lateral root formation and cytokinin production in Pisum sativum
Authors: Forsyth Clare , Van Staden J.
Published: April 2006

Decapitation of the primary roots of Pisum sativum L. resulted in a significant increase in the initiation of lateral root primordia within 12 h of the surgical treatment. Although this increase occurred both in the light and in the dark, lateral root initiation and development was much more rapid in the dark. The formation of lateral root primordia was accompanied by increased levels of endogenous cytokinins suggesting that newly formed root primordia start producing cytokinins very soon after being initiated. The significance of the present results in terms of possible sites of synthesis in vegetative tissue is discussed.