bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Growth Regulators on Root and Shoot Initiation from Flax Meristem‐Tips and Hypocotyls in vitro
Authors: LANE W. DAVID 
Published: April 2006

AbstractHypocotyl sections and isolated meristem‐tips from 7‐ to 10‐day‐old seedlings of flax were cultured on a Murashige and Skoog (1962) medium. The optimum concentrations of naphthaleneacetic acid (NAA) and benzyladenine (BA) were determined for shoot and root initiation from hypocotyls. Meristem‐tip cultures differentiated shoots and roots in response to these concentrations. The frequency and yield of shoots, promoted by BA, decreased if NAA or gibberellic acid (GA3) was included in the medium. At high NAA concentration GA3 and BA inhibited root initiation. Morphological development of cultures differed depending on the growth regulators in the medium.
Effects of Fertilization and Irrigation on the Seasonal Changes of Carbohydrate Reserves in Different Age‐Classes of Needle on 20‐Year‐Old Scots Pine Trees (Pinus silvestris)
Authors: ERICSSON ANDERS 
Published: April 2006

AbstractThe effects of fertilization, irrigation or both on the seasonal changes of starch and soluble carbohydrates (glucose, fructose, myo‐inositol, pinitol and sucrose) in needles of 20‐year‐old Scots pine trees (Pinus silvestris L.) were studied during three consecutive years. The starch content of the mature needles increased during spring and early summer to about 25% of dry weight. Neither fertilization nor irrigation affected the general pattern of starch accumulation during the spring. The starch reserves were mobilized when the shoot started to grow. Starch content decreased more rapidly in needles from fertilized than in those from unfertilized trees. The current needles from the control trees accumulated starch while they were still growing. The current needles of the fertilized trees did so to a lesser extent. The amount of starch was closely correlated to the air temperature and to the growth rate. Large amounts were found at low temperatures and low growth rates.The concentrations of soluble carbohydrates showed the well‐known seasonal variation, with the highest value during the winter. The levels of sugars were nearly similar, irrespective of fertilization. An exception was sucrose, which was found in small quantities in needles from fertilized plots. Small amounts of sucrose were also found in growing current needles.The results are discussed in relation to growth limitation by assimilate availability and indicate that the ‘sink demand’ is the limiting factor.
Plant Regeneration from Mesophyll Protoplasts of Several Nicotiana Species
Authors: BOURGIN JEAN‐PIERRE , CHUPEAU YVES , MISSONIER CLAUDINE 
Published: April 2006

AbstractIn a search for model systems in plant cell genetics studies mesophyll protoplasts from eleven species of Nicotiana with low chromosome number (N. acuminata, N. alata, N. glauca, N. glutinosa, N. langsdorffii, N. longiflora, N. otophora, N. paniculata, N. plumbaginifolia, N. suaveolens, N. sylvestris) were shown to divide in a liquid culture medium. Plants were recovered from calli originating from protoplasts of all these species except N. glutinosa.
Evidence for Naturally Occurring Inhibitors of Archegonial Differentiation in Lygodium japonicum
Authors: TAKENO KIYOTOSHI , FURUYA MASAKI , YAMANE HISAKAZU , TAKAHASHI NOBUTAKA 
Published: April 2006

AbstractArchegonial differentiation in prothallia of Lygodium japonicum was inhibited when the filtrate of conditioned medium or the extracts of prothallia with organic solvents were added to the medium. By varying the timing of treatment with the methanol extract, archegonial differentiation was shown to start at least 4 days before microscopically detectable change. The inhibitory effect of methanol extract was nullified by transferring the treated plants to a fresh medium omitting the methanol extract, so that the archegonial formation became discernible 6 days after the transfer.The inhibitory activity was stable in both acidic and basic solutions at room temperature, and was partially lost by boiling at pH 3 or 11 for 30 min. The inhibitor, which could be retrieved from the filtrate and the methanol extract, was fractionated into the neutral ethyl acetate fraction, but was not found in the acidic ethyl acetate fraction and in the aqueous residue. At least two active zones were separated on thin layer chromatograms of the ethyl acetate extracts from the filtrate and the methanol extract, and the relative flow‐rates of each active zone from these two sources were very similar. The evidence described above indicates that specific inhibitors of archegonial differentiation may be produced in the tissue of prothallia of Lygodium and eventually be secreted to the medium.
Uptake of Nitrate by Mutants of Arabidopsis thaliana, Disturbed in Uptake or Reduction of Nitrate
Authors: DODDEMA HENK , OTTEN H. 
Published: April 2006

AbstractWildtype and nitrate reductase‐less mutant B 25 of Arabidopsis thaliana (L.) Heynh. were grown on a nutrient solution with NH4NO3 as the nitrogen source. Uptake of nitrate was determined with a continuous method in which the decrease of the absorbance at 210 nm of the the ambient solution was measured. The uptake rate, plotted against concentration, deviated in the low concentration range from the standard Michaelis‐Menten curve and appeared to follow the first tract of a sigmoid curve, indicating positive cooperativity kinetics. Starvation of the plants for nitrate during a few days resulted in an increased capacity (Vmax) and affinity (decreased Km) of nitrate uptake. After prolonged starvation the uptake capacity decreased again. The highest rates of uptake were reached after 2–3days' starvation for the wildtype and after 1–2 days' starvation for mutant B 25. Soluble carbohydrates were not correlated with nitrate uptake rates. Malate was accumulated during nitrate starvation, resulting in an inverse relation between malate and nitrate content of the plants. Certain amino acids, like l‐serine and l‐arginine were shown to inhibit nitrate uptake. Based on these, and previous results, a model was proposed for the regulation of nitrate uptake, which includes allosteric regulation of the nitrate carrier by nitrate and amino acids.
Mineral Nutrient Requirements of Pinus silvestris and Picea abies Seedlings
Authors: INGESTAD TORSTEN 
Published: April 2006

AbstractThe mineral nutrient requirements of Pinus silvestris L. and Picea abies Karst. were studied according to previously published methods applied to a series of various plant species. The optimum nutrient proportions are similar to those of Vaccinium, with a lower relative potassium requirement than birch and other broad‐leaf species. Various ratios between ammonium and nitrate nitrogen were about equally efficient except for a minor growth reduction with pure nitrate, which gave a comparatively low nitrogen content and a high cation/nitrogen ratio. The rate of ammonium uptake was much higher than that of nitrate when both sources were supplied. The required total concentration in the nutrient solution for maximum growth is lower in pine than in spruce, but both fall within the low salt range. Both species, especially pine, are sensitive to high salt concentrations. Although pine and spruce grow on the same type of soils as Vaccinium— leached soils with low base saturation – accumulation of calcium or other cations is not as pronounced as in Vaccinium, especially not in pine. The results are compared with results from similar experiments with a series of other conifers. All the conifers have more flexible cation uptake mechanisms than Vaccinium but the results indicate tendencies to accumulation of anions, nitrate and phosphate. Recommended fertilizer compositions for forest fertilization and nurseries are discussed.
The Influence of pH on the Cadmium‐Repressed Growth of the Alga Coelastrum proboscideum
Authors: MüLLER KLAUS W. , PAYER HANS‐D. 
Published: April 2006

AbstractThe inhibition of growth by different concentrations of CdCl2 in the range 4,5 × 10−7 to 5.6 × 10−7M was studied in the green alga Coelastrum proboscideum Bohlin in inorganic media at pH 4.3, 5.3 and 6.2. The factorial destgn of the experiments was evaluated as an analysis of 22 factors. Below pH 4.0 and above pH 6.5 growth was depressed without adding Cd. Cd concentrations exceeding 5.6 × 10−8M reduced algal growth significantly with a 50% inhibition at 5.6 × 10−7M Cd. The Cd concentration of 5.6 × 10−7M was less toxic at pH 6.2 than at pH 5.3 and 4.3, thus revealing a negative interaction between protons and Cd.
Hormonal Regulation of Ca2+ Stimulated K+ Influx and Ca2+, K+‐ ATPase in Rice Roots: in vivo and in vitro Effects of Auxins and Reconstitution of the ATPase
Authors: ERDEL LÁSZLÓ , TÓTH ILDIKÓ , ZSOLDOS FERENC 
Published: April 2006

AbstractThe role of natural and synthetic auxins in regulation of ion transport and ATPase activity was studied in rice roots (Oryza sativa L. cv. Dunghan Shah). In vivo treatment of seedlings with 2,4‐dichlorophenoxyacetic acid at 2 × 10−6M for a short period enhanced subsequent Ca2+ stimulated K+ influx and ATPase activity, while a longer treatment diminished both K+ influx and ATPase activity. Indoleacetic acid at 10−10–10−8M induced ATPase activity. In in vitro experiments both 2,4‐dichloro phenoxyacetic acid and indoleacetic acid (10−10–10−8M) stimulated Ca2+, K+‐ATPase activity of a plasmalemma rich micro somal fraction from the roots.Acetone extracted ATPase preparations lost their activity. The enzyme regained its activity and its sensitivity towards ions (Ca2++ K+) when reconstituted with phosphatidyl choline. Addition of auxins also indicated that the presence of the lipid was necessary in the interaction between the ATPase and auxins. Auxins and ions probably interact with the intact ATPase lipoprotein complex, which may possess a receptor site for the auxins, possibly as a sub unit.
Effect of Continous Light on CO2 Fixation and Chloroplast Structure of the Mosses Pleurozium schreberi and Ceratodon purpureus
Authors: ARO EAV MARI , VALANNE NIINA 
Published: April 2006

AbstractWhen the mosses Pleurozium schreberi (Brid.) Mitt, and Ceratodon purpureus (Hedw) Brid. were exposed for 4 week to either continuous or rhythmie light of 75 or 150 μE m−2 s−1, the photosynthetic rate, calculated on the basis of chlorophyll and of dry weight, was lower in the moss plants exposed to continuous light. RUBP‐carboxylase activity was lower in these plants, too. On the other hand more starch was accumulated in the chloroplasts in continuous than in rhythmic light. Neither moss species showed any differences in the dark respiration rates. The chlorophyll content was lower in continuous light, especially at the higher intensity; but Chi a/Chl b ratio showed little change compared with that in rhythmic light. The reduction of chlorophyll did not affect the two chlorophyll protein complexes equally; the percentage of chlorophyll associated with CP I decreased, while that associated with CP II showed liltle change. The decrease in CP I chlorophyll appeared to be due to the partial destruction of stroma thylakoids: the size or the grana increased in continuous light. Many of the effects of continuous light in these mosses resembled those observed in higher plants in the early phases of senescence.
Photophosphorylation and Ultrastructural Development in Pinus nigra Chloroplasts, Grown under Different Spectral Composition of Light
Authors: TYSZKIEWICZ E. , NICOLIČ D. , POPOVIČ R. , SARIČ M. 
Published: April 2006

AbstractDeveloped pine seedlings synthesize chlorophyll in darkness. Their photosystem II reducing capacity is very low. The development of chloroplast structure and of photophosphorylation ability has been studied in plastids isolated from Pinus nigra (var. austriaca) developed for 14 days under different spectral compositions of light as compared with chloroplasts isolated from seedlings grown under white light or in darkness. Chloroplast structure was studied by electron microscopy. Cyclic and non‐cyclic photophosphorylation were studied under white light. The spectral bands which are efficient for the development of granal structures are different from those needed to make photosystem II functional: red light makes photosystem II functional but does not permit the formation of granal structure, and under yellow light the granal structure develops but photosystem II is not fully functional. Orange light alone fulfils both these purposes. The spectral band around 650 nm seems effective in making the photosystem II functional.
Solute Uptake of Acer pseudoplatanus Cell Suspensions during Recovery from Gas Shock
Authors: THOIRON BERNARD , THOIRON ARLETTE , GUIEL JEANNE LE , LüTTGE ULRICH , THELLIER MICHEL 
Published: April 2006

AbstractWhen the ambient atmosphere of Acer pseudoplatanus cells in suspension culture is rapidly changed by opening the culture flasks and gently stirring (‘mild gas‐shock’) or by filtering and suspending in new medium (‘strong gas‐shock’), drastic modifications of the rates of leucine, methionine, glucose, adenine, sulphate and phosphate uptake are observed. Following the gas‐shock, rates of uptake rapidly decrease within a few minutes. Subsequently the rates increase again to the intial level within several hours. The uptake of potassium, which is known to be passively distributed between the medium and the interior of many plant cells, at least at high external concentrations, is apparently independent of gas‐shock.The shock and recovery kinetics are similar for all solutes investigated (except K+), in particular for different solutes studied in double labelling experiments with the same batch of cells. At the maximum of the after‐effect of shock, i.e. at minimum rates of uptake, uptake shows a highly reduced dependence on temperatures. Gas‐shock probably inactivates, denatures, structurally alters or releases membrane macromolecules engaged in transport. These molecules are then re‐synthesized and re‐incorporated into the membrane during recovery.
Effects of pH Changes on Ion and 2,4‐D Uptake of Wheat Roots
Authors: ZSOLDOS FERENC , HAUNOLD ERNST 
Published: April 2006

AbstractThe quantitative relationships between pH‐dependent ion and 2,4‐D uptake in winter wheat seedlings (Triticum aestivum L. cv. Yubileynaya 50) have been investigated. The movement of various ions (potassium, phosphate, nitrate and ammonium) and 2,4‐D across the root membranes was monitored with radioactive and stable isotope tracer methods. It was found that the H+ ion concentration of the absorption solution strongly influences the 2,4‐D uptake of the roots. Simultaneously, the 2,4‐D uptake stimulates secretion of H+ into the absorption solution, that is, a H+ efflux can accompany the uptake of 2,4‐D. This finding is consistent with the acid secretion theory of auxin and fusicoccin action. At pH 4 the 2,4‐D uptake was much higher than at pH 6, thereby inhibiting the ion uptake and increasing the phytotoxicity in the plant. The results indicate that 2,4‐D enters the root cells rapidly at the lower pH, mostly as undissociated molecules. With reference to the 2,4‐D concentration in the roots at pH 4, a possible transport mechanism of the auxin herbicide is briefly discussed.
Induction of Nitrate Reductase and Peroxidase Activity in the Seedlings of Normal and High Lysine Maize
Authors: SRIVASTAVA H. S. , ASTHANA J. S. , JAIN ABHA 
Published: April 2006

AbstractSteady state levels of in vivo nitrate reductase activity in the endosperm, scutella, roots and shoots of maize seedlings were higher in normal maize than those in high lysine maize. Activity of peroxidase in the roots, however, was higher in the high lysine cultivar. The nitrate reductase activity increased with the supply of nitrate in all parts of the seedlings of both cultivars, although the rates of increment in the endosperm were lower than those in scutella, roots and shoots. In relation to substrate concentration, a saturation was achieved at 5 to 10 mM of nitrate except in the endosperm, where activity increased slowly up to 100 mM at least. Final levels of enzyme activity were significantly higher in the scutella of normal than in that of high lysine seedlings. In vitro enzyme activity in the roots also increased with the supply of nitrate in both cultivars, reaching maximum at 5 to 10 mM nitrate.
Nitrate Assimilation in Rice Grown under Lowland Conditions
Authors: RAO E. V. S. PRAKASA , PRASAD RAJENDRA , ABROL Y. P. 
Published: April 2006

AbstractPattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO3‐ when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)‐1 than the sheaths and stem. Calculation of total NO3‐ (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO3‐ was reduced to slightly over 50% of the total NO3‐ that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.
Efflux of Potassium from Wheat Roots Induced by Changes in the Water Potential of the Root Medium
Authors: ERLANDSSON GUNVOR 
Published: April 2006

AbstractEffects of rapid or stepwise decrease of the water potential by polyethylene glycol in the root medium on the efflux and uptake of 86Rb‐potassium, and the effect of abscisic acid on the efflux of 86Rb‐potassium were investigated in roots of intact wheat plants (Triticum aestivum L. cv. Weibulls Original Starke II). The efflux of ions increased at both a rapid and a stepwise reduction in water potential, but the effect was less at a stepwise reduction in water potential. Active uptake of ions decreased as much at a stepwise as at a rapid reduction in water potential. Addition of 4 × 10–5 M abscisic acid to the root medium did not affect the efflux of ions. It is suggested that low water potentials affect both membrane permeability and active uptake of ions. The increase of efflux is not induced by increase of ABA only.
Chlorophyll Composition in an Isolated Chlorophyll a‐Protein Complex of Photosystem I
Authors: ANDERSSON LARS , EGNÉUS HANS 
Published: April 2006

AbstractA P700‐chlorophyll a‐protein complex, solubilized by the detergent Triton X‐100, has been isolated by hydroxyl apatite column chromatography. The chlorophyll composition was determined by thin‐layer chromatography and spectrofluorimetric analysis. This photosystem I reaction centre complex, prepared at pH 7, contained pheophytin a and P700 in a ratio of 2/1, high enough to account for a composition similar to that in the reaction centre of photosynthetic bacteria. Prepared at pH 9, the same ratio was 0.2/1, which excludes pheophytin a from having the same function as that of bacterio‐pheophytin in the photosynthetic bacteria.
The Presence of a Ribonuclease of High Molecular Weight in Sugar Beet Storage Tissue
Authors: GUERRIERO VINCENT , DUNHAM VALGENE L. 
Published: April 2006

AbstractSoluble ribonuckasie activity in sliced root tissue or sugar beet (Beta vulgaris) decreased to 30% of initial levels during the first 15 hours of aeration in sterile phosphate buffer. Activity increased with continued aeration reaching a maximum at 30 hours (85% of initial levels). Ribonuclease activity was isolated from unaerated tissue and partially purified by precipitation with acid and ammonium sulfate and by Sephadex chromatography. Enzyme activity was linear with respect to enzyme and substrate concentrations. The enzyme exhibited a substrate preference for RNA with no activity in the presence of native or denatured DNA. Elution of the enzyme from a Sephadex G‐150 column indicated a molecular weight of 155,000. This uniquely large ribonuclease had no phosphodiesterase activity, was unaffected by ethylenediamine tetraacetate, and was inhibited by increasing Nig2+ concentrations.
Determination of Indoleacetic Acid from Plant Samples by an Alkali Flame lonization Detector
Authors: SWARTZ H. J. , POWELL L. E. 
Published: April 2006

AbstractGas chromatography in which an alkali flame ionization detector is utilized has been shown to be a highly sensitive and selective method for determination of indoleacetic acid and certain other indoles. Methodology for detecting indoleacetic acid in plant samples (Fragaria × ananassa Duch. and Malus pumila Mill.) is described.
Mesure journaliére sur cycle végétatif complet des échanges gazeux: photosynthése, transpiration et respiration nocturne ?une culture de Maïs conduite sur colonnes de sol
Authors: MOUTONNET P. , COUCHAT PH. 
Published: April 2006

Abstract Daily measurement of gas exchanges during a complete growth cycle: photosynthesis, transpiration and night respiration in a soil culture of maize.During a complete growth cycle, photosynthesis (P), night‐respiration (R) and transpiration (T) have been measured daily for maize (Zea mays L. cv. INRA F7 × F2) in a self‐regulating growth chamber. P and T varied according to three different kinetics. During the growing period there was a fast and concomitant variation of both P and T, which could be filled to a power function of time. During the fructification period we observed a linear decrease of P and T. Finally, during the senescence period P decreased to zero, whereas T kept a value higher than the evaporation of the naked soil. In the first two periods, the P/T ratio decreased as leaves aged. From this we could deduce that a slow increase of stomatal resistance (RS) and mesophyll resistance (RM) took place. R increased until the panicle appeared; it remained constant during fructification and then it decreased with senescence. Each nitrogen supply induced a transient increase of R. Finally, a water stress led to a greater decrease of P than of R, but the after effect of water stress disappeared a day later. These results were compared with those obtained in hydroponic conditions.
Petiole Pithiness in Celery Leaves: Induction by Environmental Stresses and the Involvement of Abscisic Acid
Authors: ALONI B. , PRESSMAN E. 
Published: April 2006

AbstractPetiole pithiness in celery, Apium graveolens L., was found to be stimulated by several types of root stress. Flooding of the root zone as well as nutrition deficiency required a prolonged period (25–30 days), but water deprivation had a rapid (2–3 days) effect on pithiness development.Pithiness development induced by water deprivation is not reversible upon rehydration of whole plants but is reversible upon rehydration of affected petiole slices. The stimulation of water stress‐related pithiness was found to be associated with an increased level of endogenous free abscisic acid (ABA). Exogenously applied ABA stimulated petiole pithiness of detached leaves in a concentration‐dependent fashion.It is suggested that in celery, ABA is an agent which mediates stimulation of petiole pithiness by water stress.