bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal Effects on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris
Authors: MARTIN BJÖRN , MÅTENSSON OLLE , ÖQUIST GUNNAR 
Published: April 2006

AbstractChloroplasts were isolated from primary needles of 1‐year‐old seedlings and from secondary needles of a 20‐year‐old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20‐year‐old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1‐year‐old showed the same general trends as observed in the 20‐year‐old tree, but the changes were less pronounced. However, in snow‐covered seedlings the PSI‐mediated electron transport and the electron transport from H2O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyll a antennae closely associated with the two photosystems than of the light harvesting chlorophyll a/b complex. In this case, too, the changes were more pronounced in the 20‐year‐old tree than in the 1‐year‐old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter were mainly reversed during spring.
Allosteric and Non‐Allosteric Regulation of Rubidium Influx in Barley Roots
Authors: PETTERSSON SUNE , JENSÉN PAUL 
Published: April 2006

AbstractUptake of Rb+ was investigated in 6–8‐day‐old intact barley plants (Hordeum vulgare cv. Kristina), which had been cultivated or pretreated in nutrient solutions with various K+ concentrations. The relationship between Rb+ influx and the K+ concentration of roots appeared to be sigmoidal for plants grown in solutions containing K+, indicating regulation of Rb+ uptake by allosteric inhibition of the uptake mechanism. Pretreatment of the roots in K+‐free solutions changed the pattern of uptake and caused the Rb+ influx to become linearly related to the chemical Rb+ potential of the uptake solution. Pretreatment in K+‐free solutions probably abolishes the allosteric inhibition of a carrier system.
Light‐Induced Phosphate Binding in Relation to Photophosphorylation and Levels of ATP, ADP and AMP in the Green Alga Scenedesmus
Authors: LARSSON C.‐M. , TILLBERG J.‐E. , HALLMÉN G. 
Published: April 2006

AbstractSynchronous cultures of Scenedesmus obtusiusculus Chod. were starved for phosphorus for 48 h. Such cells develop an efficient mechanism for phosphate binding which is very sensitive to metabolic inhibitions. Phosphate binding, fluctuations in the ATP pool during dark‐light‐dark transitions, and steady state levels of ATP, ADP and AMP were studied. The experiments were carried out in a CO2‐free N2 atmosphere. DCMU, phloridzin and 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐p‐benzoquinone (DBMIB) were used as inhibitors of photophosphorylation.Light‐induced phosphate uptake was inhibited to various extents by all the inhibitions. The dark‐light‐dark transition experiments show that neither the light‐induced increment in ATP nor the decrease at darkening are affected by DCMU, but DBMIB and phloridzin inhibit both processes. DCMU seems to affect the regulation of the ATP pool size. The steady state levels of the adenylate pools were almost the same in the light as in the dark, and they were also little sensitive to the inhibitors. In unpoisoned cells in the light the steady state ATP/ADP ratio was 1.7 and the energy charge was 0.66.The rates of phosphate binding are not correlated to any of the adenylate parameters studied. This is probably due to the diverse effects of the inhibitors on light‐stimulated production of reducing equivalents, photophosphorylation and transfer of energy from the chloroplast to the cytoplasm.
Changes in the Ability of Photophosphorylation and Activities of Surface‐Bound Adenosine Triphosphatase and Ribulose Diphosphate Carboxylase of Chloroplasts Isolated from the Barley Leaves Senescing in Darkness
Authors: BISWAL U. C. , MOHANTY PRASANNA 
Published: April 2006

AbstractDark‐induced aging of detached primary leaves of 11‐day‐old barley seedlings brings about a significant decline in the rates of ferricyanide [Fe(CN)6]3− reduction and photophosphorylations of isolated chloroplasts. Ferricyanide‐supported noncyclic photophosphorylation is somewhat more susceptible to leaf aging than phenazine methosulfate (PMS)‐supported cyclic phosphorylation. Non‐latent membrane‐bound adenosine triphosphatase (ATPase) and ribulosediphosphate carboxylase (RuDPCase) lose about half of their initial activities after 24 h, while during this period the electron transport and photophosphorylation activities are much less affected. Also, the loss of RuDPCase is almost complete, while chloroplasts still exhibit a significant level of [Fe(CN)6]3− reduction and photophosphorylations after 7 days of dark incubation. This would suggest that the enzymatic dark reactions are more sensitive to aging stress than the primary photochemical reactions of chloroplasts.Studies on the effect of divalent cations such as Mg2+ and Ca2+ on non‐latent ATPase activity revealed that the dark stressed aging of detached leaves brings about a time dependent alteration in the response of this enzyme to Mg2+, but not to Ca2+. The former showed inhibitory as well as stimulatory response, whereas the latter always caused the usual stimulation. Addition of kinetin (50 μM) ensured retention of [Fe(CN)6]3− reduction, photophosphorylations and RuDPCase activity in chloroplasts during leaf aging, but it failed to preserve the initial loss in the activity of the non‐activated membrane‐bound ATPase.
A Two‐Dimensional Separation of Proteins from Chloroplast Thylakoids and Other Membranes
Authors: BOSCHETTI ARMINIO , SAUTON‐HEINIGER ERIKA , SCHAFFNER JEAN‐CLAUDE , EICHENBERGER WALDEMA 
Published: April 2006

Abstract

A two‐dimensional, highly reproducible, analytical separation procedure for Triton/urea extractable proteins, using isoelectric focusing in the first dimension and gelelectrophoresis with sodium dodecylsulfate (SDS) in the second, is described. The separation of erythrocyte membrane proteins compares the reliability with that of published procedures.
From the thylakoid membranes of the green alga Chlamydomonas reinhardii and of spinach, two‐dimensional maps of the Triton/urea extractable proteins were established, containing 58 and 33 peptide spots, respectively, which were characterized by their molecular weights and apparent isoelectric points. In Chlamydomonas some of the spots could be attributed to the photosystem I and II particles. A few major spots in the maps of the thylakoid proteins from the two non‐related plants were found at the same relative positions.
A one‐dimensional electrophoretic comparison of the SDS and the Triton/urea‐extractable proteins showed that in the Triton/urea extract of thylakoid membranes some proteins of the photosystem II region, and in that of erythrocyte membranes, some components of the band 3 and 5 region are reduced or missing.
Dipeptides as Nitrogen Sources for Drosera rotundifolia in Aseptic Culture
Authors: SIMOLA LIISA KAARINA 
Published: April 2006

AbstractThe growth of Drosera rotundifolia was studied in aseptic cultures with 17 dipeptides as the only nitrogen source. About half of the dipeptides were well or partly utilized. Compounds containing glycine, alanine, glutamic or aspartic acid are clearly more favourable than dipeptides containing proline. Arginyl‐aspartic acid (1.25 mM) promoted growth more than inorganic nitrogen (1.25 mM of NH4NO3). Glycyl‐alanine gave about the same growth response as NH4NO3. The inocules died rapidly in medium containing leucyl‐tyrosine and dipeptides containing methionine and valine were also toxic. There was usually a clear correlation between the growth‐retarding or growth‐stimulating effect of the dipeptides and the effects of their amino acid components.
Effects of Water Stress on Cuticular Transpiration Rate and Amount and Composition of Epicuticular Wax in Seedlings of Six Oat Varieties
Authors: BENGTSON CURT , LARSSON STIG , LILJENBERG CONNY 
Published: April 2006

AbstractSix varieties of oat (Avena sativa L. cv. Stormogul II, Risto, Sol II, Selma, Sang and Pendek, arranged according to decreasing drought resistance) were cultivated under controlled conditions and exposed to water stress on 4 consecutive days. Seven‐day‐old seedlings were stressed by cooling the roots for 3 h to 1.0°C. During this treatment the leaf water potential decreased from ‐7 to ‐12 bars. Cuticular transpiration rate, total amount of epicuticular wax and amounts of some wax components (primary alcohols, alkanes, fatty acids) were determined.Unstressed seedlings of the most drought resistant variety (Stormogul II) showed the highest cuticular transpiration rate. After stress treatment the cuticular transpiration rate was most strongly reduced in this variety and at the same time it showed the largest increase in amount of epicuticular wax of the tested varieties. In Pendek and Sang, showing the least increase in epicuticular wax, the cuticular transpiration rate was only 5% lower after stress treatment.In all varieties the primary alcohol content of the epicuticular wax was slightly higher in stressed seedlings than in controls. Further, in Stormogul and Risto the content of the predominant alkanes was much lower in stressed seedlings than in controls. On the contrary, in Pendek the stressed seedlings showed a higher alkane content. In Stormogul II, Risto and Sol II the total amount of fatty acids was higher in stressed seedlings than in controls while the opposite was true in Sang.The relation between the epicuticular wax (amount and composition) and the cuticular transpiration rate is discussed as well as the possibility of using the tested parameters in a screening test for drought resistance.
Substituted Indoleacetic Acids Tested in Tissue Cultures
Authors: ENGVILD KJELD C. 
Published: April 2006

AbstractMonochloro substituted indole‐3‐acetic acids inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted indole‐3‐acetic acids inhibited shoot formation less. Other substituted indoleacetic acids except 5‐fluoro‐ and 5‐bromoindole‐3‐acetic acid were less active than IAA. Callus growth was quite variable and not correlated with auxin strength measured in the Avena coleoptile test.
Influence of Gamma Radiation on the Transport of Indolyl‐3‐Acetic Acid in Bark Tissue from Apple Trees
Authors: ANTOSZEWSKI R. , RANGELOV B. , DZIĘLCIOŁ U. , BACHMANN S. 
Published: April 2006

AbstractThe influence of gamma radiation on the polarity of IAA translocation was investigated. Pieces of apple tree shoots, taken from 3‐year‐old trees, were irradiated in a dark irradiation chamber BK‐60Co source, 10 kCi. Doses from 20 to 150 krad were given. Strips of bark were peeled off both irradiated and control shoots. The middle parts of the bark strips were placed on agar blocks loaded with IAA‐1‐14C. The radioactivity of basal and acropetal segments was determined after about 20 h and results expressed as polarity quotient.It has been shown that irradiation with 20 krad (200 Gy) decreases the polarity quotient remarkably (polarity quotient of control equals 7; for 20 krad—2.9; 100 krad—1.6). The decrease in polarity results from inhibition of the basipetal translocation of IAA. Irradiated tissue shows a decrease in IAA uptake. Possible mechanisms of gamma irradiation effects on polar translocation of IAA are discussed.
Control of Adventitious Root Production and Hypocotyl Hypertrophy of Sunflower (Helianthus annuus) in Response to Flooding
Authors: WAMPLE R. L. , REID D. M. 
Published: April 2006

AbstractThe morphological changes of the shoots of Helianthus annuus cv. Russian caused by varying periods of flooding of the roots were studied. Attention was focused on adventitious root formation and hypocotyl hypertrophy which are known to be caused by excess water around the roots in the absence of anoxia. Twenty‐four hours of flooding was found to be sufficient to cause both of these responses. Experiments involving flooding, leaf removal, shoot apical bud removal, two different light intensities, and a treatment in which only a small proportion of the roots were flooded suggested that a major factor causing the flood‐induced changes in the hypocotyl arises in the root but other factors may come from the leaves. In the longer‐term experiments other flood‐induced changes in shoot morphology were leaf epinasty, death of shoot apex, extreme chlorosis and hypertrophy of nodes and internodes. There was no apparent contribution of adventitious roots to the survival of flooded plants.
Changes in the Content of Phytyl and Geranylgeranyl Esters of Germinating Polytrichum commune Spores
Authors: LILJENBERG CONNY , KARUNEN PIRJO 
Published: April 2006

Abstract Polytrichum commune spores contained esterified phytol and geranylgeraniol, 706 and 114 μg, respectively, per 100 mg dry weight of freshly collected spores. After storage for 9 months the level of esterified phytol of the spores was decreased by c. 600 μg, whereas the level of esterified geranylgeraniol was more or less unchanged.The changes in the level of esterified prenols during germination follow the same pattern in freshly collected and in 9 month‐old spore material. An immediate steep decrease between 0 and 3 h was followed by an increase in the level of esterified phytol between 3 and 12 h and by a constant value for esterified geranylgeraniol during the same period. Between 12 and 48 h the level of both types of esterified prenols decreased. In the freshly collected spores the amount of esterified prenols increased after 48 h of germination, in the older spores after 72 h. Free phytol was found in trace amounts in dry and germinating spores and in the protonema.
Sprouting and Growth of Purple Nutsedge, Cyperus rotundus, in Relation to pH and Aeration
Authors: AL‐ALI F. A. , SHAMSI S. R. A. , HUSSAIN S. M. 
Published: April 2006

AbstractThe results of experiments on the sprouting and growth of purple nutsedge (Cyperus rotundus L.) in relation to pH and aeration are described. All pH levels between 2.2 to 9.0 allowed high sprouting percentage but the sprouted tubers did not survive at pH below 3 and survival beyond pH 7 was very poor. Post‐sprouting growth of nutsedge was optimal at pH 4.Pre‐sprouting aeration of tubers stimulated early sprouting and produced vigorous shoots, whereas submersion of the tubers was inhibitory. Continuous aeration of the submerged tubers substantially removed the inhibitory influence on sprouting but the shoots remained weak. Seedlings grown in constantly aerated nutrient solution showed significantly better growth than in a non‐aerated one.
Hormonal Aspects of Senescence in Detached Tobacco Leaves
Authors: EVEN‐CHEN ZEEV , ATSMON DAN , ITAI CHANAN 
Published: April 2006

AbstractThe objective of the present work was to describe the simultaneous changes in endogenous levels of cytokinins, abscisic acid, indoleacetic acid and ethylene in detached, senescing tobacco (Nicotiana rustica L.) leaves. These measurements were related to changes in chlorophyll contents, 14CO2 fixation and proline contents — three parameters which have been considered to reflect senescence. Effects of exogenous hormonal treatments on these parameters, as well as on endogenous hormonal levels, provided further evidence for the interrelationships between hormones and for their roles in senescence.Starting with actively growing attached leaves and ending with well‐advanced senescence in detached leaves, our data indicate a chronological sequence of three hormonal states: (a) cytokinins — high activity, abscisic acid, auxin and ethylene — low contents (actively growing, attached leaves); (b) cytokinins — low activity, abscisic acid — high, auxin and ethylene — low contents (apparent induction of senescence in detached leaves); and (c) cytokinins and abscisic acid — low, auxin and ethylene — high contents (senescence proper in detached leaves).
Water Potential and Component Potentials in Expanded and Unexpanded Leaves of Two Xeric Grasses
Authors: MAXWELL JAMES O. , REDMANN ROBERT E. 
Published: April 2006

AbstractWater (ψ), osmotic (ψs+ψm) and pressure (ψp) potentials were measured in three leaf regions of Agropyron dasystachyum and A. smithii grown in the field. Spanner‐type thermocouple psychrometers were used to measure ψ and (ψm+ψm). Absolute water content (AWC) was measured gravimetrically. The ψ and ψp were slightly lower in the emerging leaf blade (EBI) than in the last fully emerged leaf blade (FEBI); (ψs+ψm) and AWC were similar in the two regions. A gradient as large as 0.7 MPa was observed between the EBI and the base of the same emerging leaf (EBs); the latter included the meristematic regions. Although (ψs+ψm) and ψp were generally higher in the EBs, the gradients diminished as the level of stress increased in the shoot. Under moderate water stress the ψp of the EBs remained constant relative to the ψp in the exposed blades. The large ψ gradient within the growing leaf could have resulted from high resistance imposed by poor vascular development in the intercalary meristem. Ability to maintain a relatively large ψ gradient may be of general significance in buffering the growing region of xeric grass leaves from extreme, short‐term fluctuations in water stress that occur in exposed leaf blades.
2,4‐D‐Induced Changes in the K+ Uptake of Wheat Roots at Different pH Values
Authors: ZSOLDOS FERENC , KARVALY BÉLA , TÓTH ILDIKÓ , ERDEI LÓSZLÓ 
Published: April 2006

AbstractThe effects of an auxin herbicide, 2,4‐D, at a concentration of 0.01 mM, on the K+ uptake and efflux of excised roots of wheat (Triticum aestivum L. cv. Rannaya) were investigated at different pH values. The K+ movement was monitored with a K+ (86Rb) tracer. In parallel experiments the ATPase activities of microsomal fractions were determined by the inorganic phosphate liberation method. 2,4‐D inhibited the K+ uptake especially at low pH, irrespective of whether Ca2+ was present or not. No marked changes were observed in the K+ efflux properties at pH values above 4. The inhibitory effect on K+ uptake exhibited a correlation with the hydrocarbon solubility of the herbicide, but not with the 2,4‐D‐induced decrease of the ATPase activity. It is suggested that 2,4‐D exerts a non‐specific effect on the lipid‐protein interactions, giving rise to a generalized alteration of the transport barrier properties of the plasma membrane even at as low a concentration as 0.01 mM.
Photosynthesis of Ivy Leaves (Hedera helix) after Heat Stress I. CO2‐Gas Exchange and Diffusion Resistances
Authors: BAUER HELMUT 
Published: April 2006

AbstractFor an analysis of the inhibition of the photosynthetic CO2‐uptake after heat stress attached leaves of Hedera helix L. were heat‐stressed for 30 min at various temperatures. Subsequently their photosynthetic CO2‐uptake, transpiration, respiration in light and darkness, and CO2‐compensation concentration were measured under optimal conditions.After heat stress the stomatal resistance increased only corresponding to the raised CO2‐concentration inside the leaves (due to the reduced CO2‐uptake). The physical resistance between the mesophyll cell walls and the chloroplasts remained unchanged after heat stress. A non‐stomatal inhibition of the CO2‐uptake is indicated by a strong increase of the CO2‐compensation concentration after heat stress. This is hardly due to a stimulation of the respiration in light, as the CO2‐evolution into CO2‐free air in light was even reduced. Therefore, it must be concluded that the photosynthetic process itself is impaired after heat stress.
The Effect of Some External Factors on Nitrogenase Activity in the Free‐Living and Endophytic Nostoc of the Liverwort Blasia pusilla
Authors: RODGERS G. A. 
Published: April 2006

AbstractThe effects of pH, light intensity, temperature, oxygen and dehydration on nitrogenase activity in the free‐living and endophytic Nostoc sp. of Blasia are described. The endophyte exhibits greater nitrogenase activity at lower pH's than the free‐living alga. Maximal activity in the free‐living alga is attained at much lower light intensities than those required by the endophyte. Both algae have low activities below 10°C, the free‐living alga showing high activity above 12°C and the endophyte above 17°C. Increasing pO2 levels cause a decrease in activity in both algae. The free‐living alga is more tolerant to dehydration than the endophyte, although both algae are protected by mucilage. The results are discussed and possible benefits resulting from the symbiosis, with respect to nitrogen fixation rates, considered.
Content and Fatty Acid Composition of Steryl and Wax Esters in Germinating Spores of Polytrichum commune
Authors: KARUNEN PIRJO , LILJENBERG CONNY 
Published: April 2006

Abstract Polytrichum commune spores contained 5.61 ± 0.52 mg steryl and wax esters, including volatile compounds, per 100 mg dry weight of spores. Volatile compounds were not found in 3‐h‐old sporelings. The content of the steryl and wax ester fraction, excluding the volatile compounds, is slightly increased during the first 6 h of germination. Thereafter, the content is decreased throughout the germination. Thus, 3‐day‐old sporelings contained 0.52 ± 0.05 mg steryl and wax esters per 100 mg dry weight of spores. In connection with protonema growth, steryl and wax esters were produced, and the 7‐day‐old cultures contained 5.09 ± 0.37 mg steryl and wax esters per 100 mg dry weight of spores. The main fatty acids of the steryl and wax ester fraction of dry spores and germinating spores as well as of protonemata were palmitic, oleic, linoleic and linolenic acids. Polyunsaturated C 20 acids were present only in trace or small amounts. Phytanic and phytenic acids were found in small amounts in dry spores, in 3‐ to 72‐h‐old sporelings, and in protonemata.
The Effects of Light and Temperature on Germination and Growth of Luffa aegyptiaca
Authors: OKUSANYA O. T. 
Published: April 2006

AbstractThe effects of light and temperature on the germination and growth of Luffa aegyptiaca were investigated both in the laboratory and in the field. The seeds germinated in both darkness and light but germination was better in the light.At constant temperatures germination was best at 21°C, while alternating temperatures of 21 and 31°C and 15 and 41°C caused higher germination than the most favourable constant temperature. Constant temperatures of 15 and 31°C and alternating temperatures of 21 and 41°C resulted in very low germination, whereas no germination occurred at 41°C and at alternating temperatures of 31 and 41°C. Soil depth caused only a delay in seed germination, as it did not affect the total germination.High temperature and high light intensity resulted in good seedling growth in terms of dry weight, leaf area and relative growth rate. High temperature and low light intensity caused increased plant height and high shoot weight ratio, both of which manifested in seedling etiolation. They also caused high leaf area ratio. Under low temperatures, irrespective of light intensity, growth was generally poor, but it was significantly poorer under low light intensity, which also caused high root weight ratio. High light intensity was principally responsible for high leaf weight ratio. The results help to explain the abundance of the species in newly cleared areas in Lagos and its environs.