bluuebunny/crossref_metadata_2025 huggingface dataset:
Proline accumulation: A parameter for evaluation of sensitivity of tomato varieties to drought stress?
Authors: Aloni Beny , Rosenshtein Gila
Published: April 2006

The pattern of proline accumulation and the growth response were followed in several tomato (Lycopersicon esculentum Mill.) varieties which were exposed to 7 days of drought stress followed by a 15‐day period of rewatering. During dehydration, water potential and leaf elongation rates decreased more in var. ‘Hosen’ and ‘S‐5’ than in ‘LX‐11’, ‘1970’, ‘Pakmor’, ‘Faculty‐16’, ‘Alcobaca’ and ‘475’. Proline accumulation during stress was greatest in the first two varieties. In ‘Hosen’ and ‘S‐5’ rewatering resulted in a decrease of proline to control levels, whereas in the other varieties accumulation of proline continued long after turgor had been regained. The extent of this continued accumulation was not correlated with the degree to which each variety was dehydrated. Upon rewatering of the plants the rate of leaf elongation was increased, but the final leaf size as well as whole shoot and root fresh weight of the recovered plants were not colated with the degree of “suffering” that each variety experienced during the drought period. Incubation of detached young tomato leaves in polyethylene glycol solution for 48 h resulted in a substantial accumulation of proline. The varietal differences observed under these conditions were reminiscent of the differential responses in proline accumulation obtained in the intact plants. It is concluded that proline accumulation at the time of dehydration signals drought stress in tomato plants but does not correlate with the overall varietal sensitivity to transient dehydration in recovered plants.
γ‐Glutamyl‐transpeptidase in tobacc suspension cultures: Catalytic properties and subcellular localization
Authors: Steinkamp Reinhard , Rennenberg Heinz
Published: April 2006

γ‐Glutamyl‐transpeptidase activity (EC 2.3.2.2) was found in ammonium sulfate precipitates of extracts from cultured cells of Nicotiana tabacum L. var. Samsun. Specific activity up to 3.2 nmol (mg protein)−1 min−1 was achieved, using the artificial substrate γ‐glutamyl‐p‐nitroanilide (Km 0.6 mM) instead of glutathione. Optimal enzyme activity was obtained at pH 8.0–8.5 and 45°C. The enzyme reaction was inhibited competitively by γ‐glutamyl analogs (6‐diazo‐5‐oxo‐L‐norleucine: Ki 0.76 μM; L‐azaserine: Ki 0.23 mM) or the inorganic ion m‐periodate (Ki 0.43 mM). Cell fractionation and in vivo experiments revealed that 77% of the γ‐glutamyl‐transpeptidase activity is localized in the soluble cytoplasmic fraction, while 20–23% of the enzyme is found on the outer surface of the plasmalemma.
Phénolamides et induction florale de Cichorium intybus dans différentes conditions de culture en serre ou in vitro
Authors: Martin‐Tanguy Josette , Margara Jacques , Martin Claude
Published: April 2006

Phenolamides and floral induction of Cichorium intybus in different conditions of culture in glass‐room or in vitro.

Three complexes between phenols and amines (phenolamides) have been found in Cichorium intybus L., a plant with an absolute requirement of vernalisation followed by long days for flowering. Upon hydrolysis, these complexes (A, B and C) liberate aromatic amines whose exact identification is in progress, but which are closely related to dopamine, tyramine and serotonin, respectively.

In a first series of experiments, phenolamides were studied in the buds of plants grown in the greenhouse under varying conditions. Only buds from plants which flower in long days contained large amounts of these compounds. Much smaller amounts were found in buds at the end of vernalisation (at 2–4°C) before long‐day treatment as well as in buds kept in the vegetative state after vernalisation by being grown in short days (8 h light) or in total darkness. In a second series of experiments, phenolamides were studied in bud‐forming calli induced in vitro on explants of tuberised root. After sixteen days of culture in continuous light, large quantities of phenolamide were found in the buds and calli of the upper part of the explant, while the lower part which never produces buds contained much less.

Buds formed under continuous light produce inflorescences in approximately one month. Various other culture conditions make it possible to maintain the explants in the vegetative state. This can be obtained by short‐day conditions, or otherwise under continuous illumination by decreasing the sugar or increasing the NAA levels in the medium. After 13 days of culture, the phenolamide levels were much lower under all of these conditions, than under conditions favourable to floral induction. Compound C is absent or present in trace amounts in vegetative buds. The significance of the differences observed between floral and vegetative buds is supported by the sensitivity of the analytical techniques used.

The accumulation of phenolamides in tissues of Cichorium intybus appears to be closely linked to floral induction. Under continuous light it begins very early in young buds and even in the calli that bear these buds.
Water and solute flow through mung bean roots under applied pressure
Authors: Salim M. , Pitman M. G.
Published: April 2006

The technique of applying hydrostatic pressure on the root medium to study water and solute flows through excised plant roots and to study various characteristics of roots in relation to flow has been used by many workers but flows in excised roots have not been compared with those in intact transpiring plants. In the present study this comparison has been made using mung bean roots. Results show that excised roots under pressure lack the ion selectivity which is observed in intact plant roots and conduct salt many times higher than salt flows through intact plant roots. The role of stem resistance in the rates of water and salt flow through roots has been discussed. The suitability of this technique for solute flow studies through mung bean roots is questioned.
Regulation of root formation by auxin‐ethylene interaction in pea stem cuttings
Authors: Nordström Ann‐Caroline , Eliasson Lennart
Published: April 2006

The possibility was investigated that the inhibition of rooting in pea (Pisum sativum L. cv. Weibull's Marma) cuttings caused by low indol‐3yl‐acetic acid (IAA) concentrations is due to ethylene produced as a result of IAA treatment. Treatment with 10 uμ IAA reduced the number of roots to about 50% of the control and increased ethylene production in the stem bases by about 20 times the control value during the two first days of treatment. Ethylene‐releasing compounds (ethephon and 1‐amino‐cyclopropane‐1‐carboxylic acid, ACC), in concentrations giving a similar ethylene release, inhibited rooting to the same extent or more strongly than IAA. These results indicate that IAA‐induced ethylene is at least responsible for the negative component in IAA action on root formation in pea cuttings. A higher IAA concentration (100 μ) and indol‐3yl‐butyric acid efficiently counteracted the negative effect of ethylene on root formation.
The initial inhibition of protochlorophyll regeneration in dark‐grown leaves of barley after a short light pulse, and in greening leaves subjected to dark periods followed by a short light pulse
Authors: Virgin Hemming I.
Published: April 2006

The regeneration of protochlorophyll in darkness after a short irradiation of a dark‐grown leaf of barley (Hordeum distichum L. cv. Weibull's Ingrid), in which the protochlorophyll pool has reached its final value, starts only after a period of 2–6 min. On the other hand, the regeneration starts immediately after a repeated irradiation, provided the dark period between the two irradiations has not been long enough for the end value of the pool size to be reached. The same pattern is followed even during the process of greening. During this process the end value of the pool size of protochlorophyll during dark periods becomes smaller the more chlorophyll has been formed.
The influence of season on adenine nucleotide concentrations and energy charge in four marsh plant species
Authors: McKee K. L. , Mendelssohn I. A.
Published: April 2006

Seasonal changes in adenylate levels and adenylate energy charge (AEC) of four perennial marsh plant species growing in their natural environment were monitored. Leaf tissue was collected bimonthly from Spartina patens (Aiton) Muhl., S. cynosuroides (L.) Roth., S. alterniflora Loisel. and Distichlis spicata (L.) Greene using a method designed for field sampling of adenine nucleotides. The AEC of all four plant species exhibited a strong seasonal variability. Comparison with above‐ground biomass (g m−2) demonstrated a close relationship between AEC and growth. The AEC ratios peaked in early spring or summer (0.78‐0.85) and then declined in late summer and early fall. The ATP/ADP and ATP/AMP ratios also fluctuated seasonally and in a pattern similar to that of the AEC.
Endosperm dormancy breakage in olive seeds
Authors: Mitrakos K. , Diamantoglou S.
Published: April 2006

Seeds of Olea europaea L. ssp. oleaster Hoffm. and Link freed from the sclerous endoearp and incubated in water at 15 or 25°C in darkness or in 12:12 h white light:dark conditions, did not germinate, due to dormancy imposed by the endosperm. Seeds also did not germinate when incubated in abscisic acid, gibberellic acid, kinetin or zeatin in darkness and at cither 15 or 25°C. SAN 9789 |4‐chloro‐5‐(methylamine)‐2‐(a,a,a‐trifluoro‐m‐tolyl)‐3‐(2H)‐pyridazmone] did not promote germination at 15°C but it did to a 75% level at 25°C. This promoting effect of SAN was counteracted by abscisic acid. Cultures of naked embryos grew equally well in the presence or absence of SAN 9789. 6‐Benzylaminopurine promoted whole seed germination to a 15% level.
The physiological basis of seed dormancy in Arena fatua V. Action of ethanol and other organic compounds
Authors: Adkins Stephen W. , Naylor James M. , Simpson Graham M.
Published: April 2006

Ethanol (50‐200 mM)induced germination in four genetically pure dormant lines of Avena fatua L. The sensitivity to this treatment was moderate immediately after harvest and increased steadily during six months of after‐ripening. This sensitivity to ethanol was detectable much earlier during after‐ripening than with two other germination promoters, NaN3, and NaNO3, Because ethanol can overcome dormancy in freshly harvested caryopses, the mode of action of ethanol in these caryopses apparently differs from that of the two other promoters, azide and nitrate. Nevertheless, it is clear that induction of germination by the three promoters is fully gibberellin‐dependent since in each case this response can be blocked by the administration of 2‐chlorocthyl trimethylammonium chloride, an inhibitor of gibberellin biosynthesis. Short‐term incubation treatments with ethanol were relatively more effective than continuous treatments. These brief treatments were most effective when presented near the beginning of seed imbibition. Among other organic compounds tested only acetaldehyde significantly promoted germination in all lines tested. Propan‐1‐ol, butan‐l‐ol, chloral hydrate, procaine, methanol and chloroform were marginally effective on the least dormant lines, while ether, formaldehyde, acetone and ethyl acetate were ineffective. The mode of action of ethanol in overcoming dormancy in both freshly harvested and partly after‐ripened caryopses is discussed and the possible role as a metabolic substrate or anaesthetic is indicated.
Estimation of cellular parameters in the compartmental analysis of Li+ transport in Lemna gibba using the stable isotopes, 6Li and 7Li, as tracers
Authors: Bielenski U. , Ripoll C. , Demarty M. , Lüttge U. , Thellier M.
Published: April 2006

Using the conventional methods of compartmental analysis has led us to recognize three main compartments in the Lemna cells: the cell‐wall, cytoplasm and vacuolc. The half‐times of Li+ isotopic exchange were of the order of a few minutes, a few hours and a few days, respectively. The possible existence of a 4th, small, and almost non‐exchangeable compartment cannot be excluded. Despite different possible sources of uncertainty (ambiguity of the kinetic solutions, no uniformity of cell types in the plant material, uncertainties in the estimations of electric potentials), the data were consistent with i) Li+ being actively extruded from the cytoplasm, both towards the exterior and the vacuole, ii) the electrochemical potential difference of Li+ being of the order of ‐25 kj mol across the plasmalemma, and in the range of 5 to 10 kJ mol across the tonoplast, and iii) the passive permeability coefficients of Li+ being in the range of 10 to 10 m s both for the plasmalemma and the tonoplast.
Recycling efficiency in hydrogenase uptake positive strains of Rhizobium leguminosarum
Authors: Truelsen Truels A. , Wyndaele Rita
Published: April 2006

The presence of hydrogen uptake (Hup+) activity was demonstrated in root nodules formed on the pea cultivar Bodil (Pisum sativum L. cv. Bodil) by 19 out of 23 tested strains of Rhizobium leguminosarum. Only 3 of the 19 Hup+ strains showed significant hydrogen recycling efficiency in the nodules. The correlation between N; fixation in nodules and N content of aerial parts of the plants was poor. The reasons for this and for the luck of significant hydrogen recycling in 16 of the 19 Hup+ strains is discussed.
Phospholipids, free sterols and adenosine triphosphatase of plasma membrane‐enriched preparations from roots of citrus genotypes differing in chloride exclusion ability
Authors: Douglas Trevor John , Walker Robert Ronald
Published: April 2006

Plasma membrane‐enriched preparations from fibrous roots of three citrus genotypes differing in their abilities for chloride exclusion, and grown in the presence of 0,50 or 100 mM NaCl for 4 weeks, were analysed for phospholipid and free sterol content and vanadate‐sensitive adenosine triphosphatase (ATPase) activity over a range of temperatures. The best chloride excluder, Rangpur lime (Citrus reticulaia Blanco var. austera hyb.?), had significantly higher maximal ATPase activity than both the moderate chloride excluder. Kharna khatta (Citrus kharna Raf.), and the worst chloride excluder, Etrog citron (Citrus medico L.), at all assay temperatures below 28°C. Salt treatment had no effect on maximal ATPase activity of either Rangpur lime or Etrog citron but resulted in increased activity of the enzyme in Kharna khatta at temperatures below 28°C.

Arrhenius plots of ATPase activity from the three citrus genotypes showed that, in controls, the activation energy (E.,) of Rangpur lime ATPase was significantly lower than that of both Kharna khatta and Etrog citron. The thermotropic phase transition temperature (Tf) for Rangpur lime (27°C) was also lower than for the other citrus genotypes (31°C). Salt treatment resulted in increases in both Ea and T, for Rangpur lime, decreases in both parameters for Kharna khatta and no change of either parameter for Etrog citron.

An inverse relationship between Ea and the phospholipid to free sterol ratio was evident for plasma membrane preparations from all three citrus genotypes in the presence and absence of salt treatment suggesting that changes in membrane fluidity, particularly those induced by free sterols, have the potential to influence active as well as passive ion transport processes and thus may play a significant role in the chloride exclusion mechanism.
Opposite effects of temperature on breaking of dormancy and on induction of frost resistance in apple embryos
Authors: Nguyen X. V. , Côme D.
Published: April 2006

Apples (Pyrus mains L., ev. Golden Delicious) were placed at 0, 12 and 35°C. At different intervals, seeds were taken from fruits, and the ability of isolated embryos to germinate was determined. In parallel, the survival of similar embryos frozen for 30 min at ‐7°C was estimated. Storage of apples at 0°C led to complete removal of embryo dormancy within ca 10 weeks. At 12°C, dormancy was only partly eliminated, and at 35°C breaking of dormancy did not occur. The onset of secondary embryo dormancy was thus evident as the result of 35 and 12°C treatments. On the other hand, the storage of apples at 35°C was the most effective treatment for induction of frost resistance in the embryos. At 12°C the same level of frost resistance was reached much slower. Even a prolonged storage of apples at 0°C did not allow frost survival of all embryos. The above relations were confirmed in experiments with transfer of fruits from one temperature of storage to another. The temperature of fruit storage affected the dormancy removal in embryos and induction of resistance to rapid freezing in opposite directions.
Comparative studies of diurnal variations of nitrate reductase activity in wheat, oat and barley
Authors: Lillo Catlirinc , Henriksen Aase
Published: April 2006

Diurnal variations of in vitro and in vivo (intact tissue assay) nitrate reductase (EC 1.6.6.1) activity and stability were examined in leaves of wheat (Triticum aestivum L. cv. Runar), oat (Avcna saliva L. cv. Mustang) and barley (Hordeum vulgure L. cv. Agneta and cv. Gunillu). Nitrate reductase activity was generally higher for wheat than for oat and barley. However, the diurnal variations of nitrate reductase activity and stability were principally the same for all species, e.g. the high activity during the photoperiod was associated with low stability. All species showed a rapid (30‐60 min) increase in the in vitro and in vivo activity when the light was switched on. When light was switched off the in vitro activity decreased rapidly whereas decrease in in vivo activity was slower. These experiments support the hypothesis that an activation/ deactivation mechanism is involved in the regulation of diurnal variations in nitrate reductase activity. Red light enhanced nitrate reductase activity in etiolated wheat and barley leaves. In green leaves, however, the daily increase in nitrate reductase activity was not induced by a brief red light treatment. Indications of different regulation mechanisms for the diurnal variations of nitrate reductase activity among the cereals were not found.
Effects of CO2 enrichment on photosynthesis and photosynthate partitioning in soybean (Glycine max) leaves
Authors: Huber S. C. , Rogers H. , Israel D. W.
Published: April 2006

The short‐term and long‐term effects of CO, enrichment on certain aspects of photosynthesis and leaf carbohydrate metabolism were studied with soybean [Glycine max (L.) Merr.] plants. In general, both long‐term and short‐term CO2 enrichment (300 ppm CO2 above ambient) of soybean plants resulted in increased rates of photosynthesis (per unit leaf area) and starch accumulation. Leaf sucrose concentrations were increased slightly, but the rate of assimilate export and activity of sucrose phosphate synthase (EC 2.4.1.14) were usually not increased. Plant N‐status affected the response of vegetative soybean ‘Ransom’ plants to short‐term CO, enrichment. When plants were N‐stressed (2 mM NO3‐ supplied), CO2 enrichment resulted in increased rates of both starch accumulation and export. As N‐supply was increased, partitioning of carbon into starch in CO2‐enriched atmospheres increased at the expense of assimilate export. When plants were grown with high‐N (20 mM NO3), the rate of assimilate export from CO2‐enriched leaves was reduced below the rate observed with plants maintained at ambient CO2. The reduction in export rate was associated with decreased activities of sucrose phosphate synthase in leaf extracts. The activity of sucrose phosphate synthase in leaf extracts was closely associated with partitioning of carbon between starch and sucrose in leaves, and with the rate of assimilate export.
Ca2+ acts synergistically with brassinosteroid and indole‐3‐acetic acid in stimulating ethylene production in etiolated mung bean hypocotyl segments
Authors: Arteca Richard N. , Guern J.
Published: April 2006

Brassinosteroid (BR) and indole‐3‐acetic acid (IAA) were used in combination with Ca2+ in order to determine if there was a synergistic effect in the stimulation of ethylene production in etiolated mung bean (Vigna radiata L. Rwilez ev. Berken) hypocotyl segments. Ca2+ was found to act synergistically with BR. IAA or a combination of the two in promoting a stimulation in ethylene production. EDTA, which chelates Ca2+, greatly reduced the effectiveness of calcium salts in promoting ethylene production in the presene of either BR, IAA or a combination of the two. Neither K+, Mg2+ nor Mn24 (chloride salts) acted synergistically with BR and IAA.
Sexual differentiation in higher plants
Authors: Durand R. , Durand B.
Published: April 2006

As in all organogenetic studies, sex differentiation implies three fields of research: the identification of macsomalecular markers specific for stamens or carpels }expression program); the analysis of the signals (such as phytohormones{ inducing them: and finally the knowledge of the regulator genes (sex detsrmination genes).

In dioecious plants, sex determination (male and female genes or combinations of heterochromosomes) occurs at the fertilization stage. These regulators probably act early by means of inducers; their action is perceptible mainly when reproductive organs develop, and the existence of target cells able to respond to the inductive message is obvious. Experimental control of sex expression by phytohormones leads to the repression of the normal organogenetic program (induced by the presence of the sex genes) arrd to the induction of the opposite program (normally incompatible with these genes).

Analogous mechanisms occur in monoecious plants, but here the male program is always expressed before the female one. Experimental control of sex expression suggests that the successive induction of first male and then the female program results from inverse gradients of male and female signals. Sex differentiation studies of monaeciousness are more difficult than studies on dioeciousness since, in all the cells. not only male and female programs co‐exist as in dioeciousness, but also male and female sex penes and signals.

The present model has been tested in the dioecious Mercurialisannua (2n = 16) and some other species, and the results that have been established are described.
Glycerol‐3‐phosphate dehydrogenase (EC 1.1.1.8) from Dunaliella tertiolecta. II. Influence of phosphate esters and different salts on the enzymatic activity with respect to osmoregulation
Authors: Haus M. , Wegmann K.
Published: April 2006

The effects of AMP, ATP, inorganic phosphate and fructose‐1, 6‐bisphosphate on glycerol‐3‐phosphate dehydrogenase (NADH) from Dunaliella tertiolecta were investigated. In addition the salt effects and the influence of different anions were studied. The results support the assumption that concentration changes of intermediates and salts by cell shrinkage during osmotic stress can account for the control of glycerol synthesis.
Homology of plant peroxidases: Relationships among acidic isoenzymes
Authors: Clark Samuel K. , Conroy James M.
Published: April 2006

Antisera specific for two commercial acidic peroxidases from horseradish (Amoracea rusticana L.) were used to determine the degree of homology between isoperoxidases from horseradish, turnip (Brassica rapa L. cv. Purple White Top Globe) and radish (Raphanus sativus L. cv. Cherry Belle). Ouchterlony agar diffusion, precipitin tests and anticatalaytic assays were used to show that acidic horseradish peroxidases could be distinguished by immunological methods but were closely related. Antisera specific for either horseradish acidic isoperoxidase gave a lesser degree of cross reaction with the basic isoenzyme from this plant. Acidic isoperoxidases from turnip and radish were more closely related to acidic horseradish peroxidases than the basic isoperoxidase from horseradish as assessed by immunological cross‐reaction. Basic isoperoxidases from carrot (Daucus carota L. cv. Danvers), radish or turnip did not react with antisera prepared against acidic horseradish peroxidases. Finally, acidic horseradish peroxidases were shown to be poor immnnogens in rabbits in contrast to the basic horseradish isoenzyme.
Ammonia‐assimilating enzymes in bryophytes
Authors: Meade R.
Published: April 2006

Ammonia can be incorporated into amino acids by reductive amination of oxoglutarate, or by the glutamate synthase cycle via glutamine. The majority of plants possess the enzymes necessary for the operation of both these pathways although nitrogen is thought to be assimilated via the glutamate synthase cycle in most cases. Measurements of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase activities are presented from a selection of bryophytes. The genus Sphagnum was found to be unique in lacking measurable glutamate dehydrogenase activity. The relevance of this in the nitrogen‐poor acid bog is briefly considered.
Promotion and inhibition by plant growth regulators of aerenchyma formation in seedling roots of Zea mays
Authors: Konings Henk , de Wolf Anita
Published: April 2006

The influence of naphthylacetic acid, abscisic acid, gibberellic acid and kinetin on the formation of aerenchyma in seedling roots of Zea mays L. cv. Capella has been studied in relation to reported changes of their concentration in poorly aerated roots, which readily form aerenchyma, and to the effects of these hormones on the production of ethylene, a major factor promoting aerenchyma formation. Because the absence of nitrate accelerates aerenchyma formation in aerated roots, their influence on these roots was compared. The growth regulators were added to roots growing in non‐aerated and aerated nutrient solutions, and aerenchyma formation and the production and endogenous concentration of ethylene were measured. Naphthylacetic acid prevented aerenchyma formation in both aerated roots without nitrate and in non‐aerated roots although it enhanced the ethylene concentration of the roots. Abscisic acid also prevented aerenchyma formation, but without affecting the ethylene concentration. Gibberellic acid promoted aerenchyma formation in aerated roots only, but ethylene production in both aerated and non‐aerated roots. Kinetin promoted aerenchyma formation in both aerated and non‐aerated roots. It stimulated ethylene production in aerated roots, but slightly inhibited it in non‐aerated roots. Co2+ and Ag+, which suppress ethylene production and action, respectively, reduced the promoting effects of gibberellic acid, but not those of kinetin. It is concluded that the effects of the plant growth regulators on aerenchyma formation in maize roots were, with a possible exception for gibberellic acid, not the result of altered ethylene concentrations in the roots. Their influence on aerenchyma formation is discussed in relation to their reported actions on cell membranes.
Changes in peroxidase, indolyl‐3‐acetic acid oxidase and amylase activities in a viable wheat hybrid and its antecedents
Authors: Chaturvedi Neera , Laloraya M. M.
Published: April 2006

A viable wheat hybrid intermediate of the same height as the parents was obtained by crossing the female parent of tall variety NP4 with the male parent of the dwarf variety HD2160. Seeds of the hybrid and its parents were germinated and their growth pattern as well as the activities of peroxidase, indolyl‐3‐acetic acid oxidase and amylase in extracts made from them were studied at the early seedling stages i.e. up to 96 h.

A positive correlation existed between the length of the axis at the early seedling stage and at mature plant height as far as the parental varieties are concerned but no such correlation was observed with the hybrid. Growth of the hybrid seedlings was less than of its parents. Light appeared to stimulate the longitudinal growth of the axis to different extents in the parents and hybrid. Higher activities of peroxidase, indolyl‐3‐acetic acid oxidase and amylase were observed in the hybrid as compared to both of its parents. Lethal wheat hybrid also exhibits increased activities of amylase, indolyl‐3‐acetic acid oxidase and peroxidase. Therefore, it appears that seedling growth and enzyme activities at the seedling stage are not always correlated with hybrid vigour.
Endopeptidase activity and nitrogen mobilization in senescing leaves of Nicotiana rustica in light and dark
Authors: Weckenmann Dieter , Martin Peter
Published: April 2006

The time course of endopeptidase activity (digestion of azocasein at pH 4.6) in leaves of intact plants of Nicotiana rustica L. was studied and related to changes in the contents of chlorophyll, total nitrogen and soluble and insoluble protein nitrogen. Endopeptidase activity increased several fold during senescence. However, the course of protein degradation did not reflect the steep slope of azocaseolytic activity. When single mature leaves were darkened, senescence proceeded faster than in illuminated leaves but the amount of nitrogen mobilized and translocated did not differ greatly between darkened and illuminated leaves. However, in contrast to leaves in light, azocaseolytic activity did not increase.

Gelatin zymograms obtained using isoelectric focusing of extracts of mature leaves showed several bands in the pH 4.0 to 6.5 region of the gels. During senescence in both light and dark the position and number of bands remained largely unchanged. In leaves in light, the activity of endopeptidases focusing in the range pH 4.1 to 5.0 increased greatly. In leaves in dark, however, no major changes in activity could be detected. The results suggest that in tobacco leaves endopeptidase activity normally increases considerably during senescence but this increase is not a prerequisite for an effective protein degradation.

Separation and analysis of free amino acids showed that during senescence in light the levels of all amino acids decreased considerably. In leaves senescing in the dark there were large increases in the levels of glutamine and asparagine, concomitant decreases in glutamate and aspartate, and considerable increases in all other amino acids.
Phytochrome control of its own accumulation and leaf expansion in tentoxin‐ and norflurazon‐treated mung bean seedlings
Authors: Duke Stephen O. , Lane Alfred D.
Published: April 2006

Primary leaves of 4‐day‐old, dark‐grown mung bean [Vigna radiata (L.) Wilczek cv. Berken] seedlings were exposed to 24 h of white light (200 μmol m−2 s−1) which was terminated by a 15 min, phytochrome‐saturating red or far‐red light exposure. Phytochrome content (in vivo and in vitro) and leaf area were monitored during the subsequent dark period. Red light treatments resulted in lower phytochrome content and greater leaf expansion than did far‐red treatments. Phytochrome accumulation and leaf expansion were less in norflurazon‐ (no carotenoids and very low Chl) than in tentoxin‐ (very low Chl) treated leaves. After 3 days of darkness, leaf expansion was about 25% greater and phytochrome content was about 50% less in red‐ than in far‐red‐treated leaves of all treatments. These effects generally took longer to develop in norflurazon‐ than in tentoxin‐treated tissues. Norflurazon‐treated tissues exposed to long white light periods apparently do not as accurately reflect phytochrome‐controlled photomorphogenic events of green tissues as do tentoxin‐treated tissues of mung bean seedlings.
A brassinosteroid‐cytokinin interaction on ethylene production by etiolated mung bean segments
Authors: Schlagnhaufer Carl , Arteca Richard N. , Yopp John H.
Published: April 2006

Three cytokinins and their ribosides were tested in conjunction with brassinosteroid (BR) for their effects on ethylene production in etiolated mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. When varying concentrations of BR were tried in combination with a fixed amount of kinetin (10 μM), there was an increase in ethylene production with increasing concentrations of BR up to 3 μM, and a decline beyond. A stimulation in ethylene production was observed with increasing concentrations of each of the cytokinins used. However, when applied in conjunction with 3 μM BR, all cytokinin concentrations produced similar stimulatory patterns. When 3 μM BR or 10 μM 6‐benzylaminopurine (BAP) was applied in conjunction with increasing concentrations of IAA, there was a stimulation in ethylene production with increasing concentrations of IAA. However, 3 μM BR and 10 μM BAP together with varying concentrations of IAA failed to alter the level of ethylene production.
Polyamines bound to nucleic acids during dormancy and activation of tuber cells of Helianthus tuberosus
Authors: Serafini‐Fracassini Donatella , Torrigiani Patrizia , Branca Camillo
Published: April 2006

Tuber tissue of Helianthus tuberosus L. (cv. OB1) contains a low amount of polyamines during dormancy but they are rapidly synthesized when tuber cells are activated in a growth medium and enter a new cell cycle. It was assumed that one of the reasons for this synthesis is that polyamines are necessary for the active conformation and correct functioning of nucleic acids. Complexes were found between spermine, spermidine and putrescine and rRNA, tRNA and an RNA fraction which contains poly(A) RNA and proteins. The amount of RNA‐bound polyamines in the parenchyma cells of dormant tubers is dependent on the stage of dormancy and clearly increases (especially putrescine) when cells are activated. There are both tightly‐bound and non‐tightlybound polyamines. The significance of these bound polyamines is discussed in relation to their stabilizing role on nucleic acids.
Measurement of light gradients and spectral regime in plant tissue with a fiber optic probe
Authors: Vogelmann Thomas C. , Björn Lars Olof
Published: April 2006

A method is described in which light gradients and spectral regime can be measured within plant tissue using fiber optics. A fiber optic probe was made by modifying a single optical fiber (200 μm diameter) so that it had a light harvesting end that was a truncated tip 20–70 μm in diameter. The probe was a directional sensor with a half‐band acceptance angle of 17–20°. Light measurements were made as the fiber optic probe was driven through plant tissue by a motorized micromanipulator, and the light that entered the fiber tip was piped to a spectroradiometer. By irradiating green leaf tissue of the succulent Crassula falcata L. with collimated light and inserting the probe from different directions, it was possible to measure light quality and quantity at different depths. Collimated light was scattered completely by the initial 1.0 mm of leaf tissue, which also greatly attenuated all light except the green and far‐red. Light scatter contributed significantly to light quantity and had a pronounced spectral structure. Immediately beneath the irradiated surface the amount of light at 550 nm was 1.2 times that of the incident light. The light gradient declined rapidly to 0.5 times incident light at 1.4 mm depth. In contrast, the amount of light at 750 nm increased during the initial 0.5 mm to 2.9 times incident light and then declined linearly to 0.5 times incident light at the dark side of the leaf (4.5 mm). The implications of the magnitude of the contribution of light scatter to the light gradient is also discussed.
Chromophore structure in phytochrome intermediates and bleached forms of phytochrome
Authors: Thümmler F. , Rüdiger W.
Published: April 2006

Phytochrome (120 kdalton or 60 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa München). Irradiation with red light of the Pr form at −23°C in aqueous medium or at −40°C in 66% glycerol leads to the intermediate meta‐Rb. Acidification of the glycerol solution at −40°C leads to the absorption of the 15(E) phytochrome chromophore (= Pfr chromophore). Subsequent irradiation transforms this into the 15(Z) chromophore (= Pr chromophore). The presence of the 15(E) chromophore was demonstrated by the same methods also in phytochrome bleached either as Pfr in the dark by 4 M urea, methanol, acetone, ethylene glycol, 8‐anilinonaphthalene‐1‐sulfonate, or as Pr by irradiation with red light in the presence of the same agents. Phytochrome bleached by sodium dodecylsulfate or by dehydration was also investigated. It was concluded that bleached phytochrome contains the Pfr chromophore without specific interaction with the protein.
Biosynthesis of acyclic and cyclic carotenoids in higher plants and the control by phytochrome
Authors: Grumbach K. H.
Published: April 2006

Radish plants (Raphanus sativus L. cv. Saxa treib) were grown in the presence of three different herbicides interfering with the biosynthesis of cyclic carotenoids. The herbicides caused an accumulation of acyclic biosynthetic intermediates. Plants were then irradiated using four different light programs in order to gain more insight into the first steps of carotenoid biosynthesis and their control by light and phytochrome. Plants grown in the dark in the presence of SAN 6706 or aminotriazole accumulated the acyclic intermediate phytoene, and those treated with J 852, the intermediates phytoene, phytofluene and zeta‐carotene. In herbicide‐treated plants short time irradiation with red light enhanced the formation of phytoene, phytofluene, zeta‐carotene or lycopene, consistent with an effect of phytochrome on the early steps of carotenoid biosynthesis. Biosynthesis of cyclic carotenoids was also enhanced by red light in the untreated controls. In amitrole‐treated plants formation of β‐carotene, but not that of xanthophylls was stimulated by red light. In many cases neither the red light‐induced biosynthesis of cyclic carotenoids nor the formation of acyclic intermediates could be prevented by a subsequent irradiation with far‐red light. Similar enhancement as with red light was also obtained after treatment with far‐red light only. Presented data may be taken as evidence that the biosynthesis and dehydrogenation of phytoene and the cyclization of lycopene are activated by a low threshold of active phytochrome. This may be further supported by the observation that far‐red light itself stimulated carotenoid biosynthesis.
The development and ageing of membranes from etioplasts of Avena sativa
Authors: Bergweiler Paul , Röper Ursula , Lütz Cornelius
Published: April 2006

A growth period from day 4 to day 11 after sowing of dark‐grown oat seedlings (Avena sativa L. cv. Flämingskrone) was studied. Etioplasts were prepared from various stages. By means of one and two dimensional gel eletrophoresis developmental changes in the polypeptide pattern of the prolamellar body‐prothylakoid complex of etioplasts were studied. Polypeptides were described by their molecular weights and pI values after isoelectric focusing. The polypeptide map changes continuously with age, with the onset of effects of senescence around day 7. Concomitantly, proto‐chlorophyllide and proteins are degraded, with a higher degradation rate for proto‐chlorophyllide. An analysis of protochlorophyllide fluorescence displayed a constant ratio (fluorescence emission at 650 nm/fluorescence emission at 630 nm) from day 6 to day 11. It is concluded, that the best stages for greening studies of dark‐grown oat seedlings occur between day 4 and day 6 after sowing.
Oleic acid metabolism: A biochemical marker for studying photoregulation of epicotyl elongation in Vigna unguiculata
Authors: de March Ghislaine , Tréimolières Antoine , Lecharny Alain
Published: April 2006

Oleic acid metabolism can be considered to be an indicator of growth photoregulation in cowpea (Vigna unguiculata Westphal cv. M53) epicotyls. Phosphatidylcholine and phosphatidylethanolamine are the two lipid classes concerned in the photoregulation of oleic acid accumulation. The incorporation of radioactive precursors in internodes of whole plants has shown that there is de novo synthesis of these phospholipids during the light dependent growth process.

The variations in oleic acid content were used to study the photocontrol of elongation in segments excised from the apical part of the epicotyl. In this system, as in whole plants, oleic acid was the only fatty acid showing significant variation related to the light/dark treatments. Differences in photoresponse between excised intenode segments and internodes in whole plants are discussed.
An enzyme‐linked immunosorbent assay for phytochrome
Authors: Thomas Brian , Crook Norman E. , Penn Susan E.
Published: April 2006

A double‐antibody sandwich, enzyme‐linked immunosorbent assay has been developed for phytochrome in Avena sativa L. cv. Saladin. An immunoglobulin fraction of rabbit antiserum raised to 118 kdalton phytochrome was used with alkaline phosphatase as the enzyme label. The assay detected as little as 0.2 ng phytochrome in extracts of dark‐grown plant material. No evidence for specific or non‐specific measurement of proteins other than phytochrome was found. The assay detected phytochrome in extracts of Avena grown in the light. Dilution curves for light‐grown phytochrome extracts had a reduced slope and saturated at a lower level of enzyme activity than those for dark extracts. These differences were not caused by an inhibitor in extracts from light‐grown plants. Phytochromes from dark‐ and light‐grown plants may be immunologically different.
A study of phytochrome‐membrane association using an enzymelinked immunosorbent assay and Western blotting
Authors: Jordan Brian R. , Partis Michael D. , Thomas Brian
Published: April 2006

Enzyme‐linked immunosorbent assay (ELISA) and Western blotting have been used to study the association between phytochrome and membranes in dark‐grown tissue of Avena sativa L. cv. Saladin. Enhanced phytochrome pelletability can be demonstrated by ELISA after red irradiation in vivo and extraction in buffer containing Mg2+, but not with red irradiation of Mg2+ alone. This enhanced association may, however, be restricted to specific membranes. The results obtained with ELISA are confirmed by Western blotting techniques. Membrane‐associated and soluble phytochrome give different immunological responses and it is suggested that immunologically distinct populations of phytochrome may exist in dark‐grown tissue.
Stem extension rate in light‐grown plants. Evidence for an endogenous circadian rhythm in Chenopodium rubrum
Authors: Lecharny A. , Wagner E.
Published: April 2006

Stem extension in light‐grown plants of Chenopodium rubrum L. ecotype selection 184 (50°10′N; 150°35′W) was recorded continuously for periods up to one week at constant temperature. Stem extension rate measurements were made with linear voltage‐displacement transducer devices. At the beginning of experiments, the 3rd intenode above the cotyledons was about 5 mm long. Stem extension rate exhibited a rhythmic behaviour in continuous white light (20 W m−2), and in continuous darkness with a period of approximately 23 h. In continuous darkness, the amplitude of the rhythm damped out very quickly after 24 h and a second peak was just measurable. The mean value of the stem extension rate was dependent on the light fluence before the experiments. This overt rhythm, which could be observed at the individual plant or even internode level, exhibited the characteristics of an endogenous circadian rhythm. There was no correlation of the peak time to local time. The peak time was determined by the time of transfer from dark to light for dark periods equal to or longer than 8 h, and the phase was shifted by the time of transfer from light to dark at the proper phase of a pre‐existing rhythm.
Sporulatim in the fungus Verticillium agaricinum: Reversal of blue light inhibition by Ultraviolet radiation
Authors: Hsiao Ke‐cheng
Published: April 2006

In colonies ranging from 3‐ to 5‐days‐old, light in general stimulates conidiation in Verticillium, including V. agaricinum and several strains of V. albo‐atrum. However, when growth was started by inoculating with conidial suspension spread evenly over the plate, it was found that blue light inhibited conidiation in our strain of V. egaticinum. We most light‐sensitive phase was around 9 h after inoculation. A broad band blue light pulse of 10 J m−2 saturated the response. The inhibitory effect of blue light could be reversed by a subsequent ultraviolet (UV) radiation, but a further effect of blue light was lost after the UV pulse. Blue light inhibition was also prevented by IJV radiation administered before the blue light.
Ultraviolet light‐induced coiling and curvature of broom sorghum first internodes
Authors: Hashimoto Tohru , Ito Sumiko , Yatsuhashi Hiroko
Published: April 2006

Unilateral pulse ultraviolet irradiation caused positively phototropic coiling (> 180°) and curvature (≤ 180°) in the growth zone of dark‐grown broom sorghum (Sorghum bicolor Moench, cv. Acme Broomcorn and Sekishokuzairai Fukuyama) first internodes. Coiling was induced by irradiation at 257 to 302 nm, and proceeded to develop almost linearly during 72 h or more involving new tissue produced after irradiation. Curvature, caused at 308 to 413 nm and by red light, developed rapidly during the first several hours then slowly to cease by about 24 h, and did not surpass 120° even at the optimum photon fluences. Action spectra were higher towards shorter wavelengths, having a shoulder at about 287 nm, and could not separate the two photoresponses. The curvature was partially but markedly suppressed by far‐red following the ultraviolet irradiation, whereas the coiling was not affected. Possible involvement of a specific UV‐B photoreceptor and phytochrome in curvature and of a UV‐C photoreceptor in coiling is discussed.
Carbohydrate accumulation and partitioning in Pinus banksiana seedlings and seedling cuttings
Authors: Haissig Bruce E.
Published: April 2006

Tests were conducted to identify possible relations between carbohydrates and callusing‐rooting of Pinus banksiana Lamb, cuttings. Terminals, upper stems, and basal (1 cm) stems of 90‐day‐old untreated seedlings and seedling cuttings were analyzed for sucrose, total soluble reducing sugar, starch and total non‐structural carbohydrate during propagation. Seedlings were evaluated in order to determine whether data for cuttings alone properly described carbohydrate‐callusing‐rooting relations under conditions where stock plants and cuttings were propagated in different environments. Results indicated that seedling terminals and upper stems, but not basal stems, accumulated the measured carbohydrates much like cuttings, though to lesser concentrations. Thus, carbohydrate accumulation by cutting terminals and upper stems would have been overestimated, based on cutting data alone. In terms of rooting, results indicated that: 1) Total carbohydrate accumulation in cutting basal stems was related to callusing‐rooting, but a cause‐effect relation was not established; 2) The positive relation between callusing‐rooting and total carbohydrate accumulation was primarily due to accumulation of reducing sugar and starch, with reducing sugar predominant. 3) Reducing sugar/starch concentration ratios were the most sensitive and convenient indicators of specific carbohydrate differences within and between seedlings and cuttings.
Interactions of green or red light with blue light on the dark closure of Albizzia pinnules
Authors: Tanada Takuma
Published: April 2006

The interactions of green or red light with blue light on the dark closing of Albizzia julibrissin Durazz. pinnules have been investigated. Irradiations at 430, 450 and 470 nm progressively delay dark closing with increasing photon fluence rates. Red or green light alone has no effect. However, when the blue fluence rate is low, both red and green light interact with it and increase the delaying effect of the blue light. When the blue fluence rate is high, green light interacts with it to negate some of the effectiveness of the blue light, while red light has no effect. This is similar to results obtained previously with far‐red light. It is suggested that the same unidentified photoreceptor is operating in both the far‐red and blue regions. The results also indicate the presence of a blue‐only absorbing photoreceptor whose action is increased by phytochrome.