bluuebunny/crossref_metadata_2025_split huggingface dataset:
Half‐Life of sRNA from Primary Roots of Zea mays. A Contribution to the Cytokinin Production
Authors: KLEMEN FRANZ , KLÄMBT DIETER 
Published: April 2006

AbstractRoots produce cytokinins, which could be generated from the catabolism of transfer RNA. To prove such a hypothesis, the half‐life of sRNA from primary roots of corn was measured. The shortest half‐life was estimated to be 3 days. Depending on growth, cells at the root tips are “moving” out of the growing region and become differentiated cells. Therefore the highest label at the root tip during the pulse incubation is moving backwards during the chase incubation. Prolonged chase increases the half‐life of sRNA successively, possibly due to decreasing metabolic activities of the originally labeled cells.
Iron‐Stress Response in Tomato (Lycopersicon esculentum) 1. Sites of Fe Reduction, Absorption and Transport
Authors: BROWN J. C. , AMBLER J. E. 
Published: April 2006

AbstractT3238fer (Fe‐inefficient) and T3238FER (Fe‐efficient) tomato plants differ in their ability to utilize Fe and therefore can be used as test genotypes to locate sites of Fe uptake or to characterize changes that occur in roots in response to Fe stress (Fe deficiency). T3238fer does not respond to Fe stress. Release of hydrogen ions and reduction of Fe3+ to Fe2+ are two primary responses of T3238FER roots to Fe stress. Fe reduction sites were predominately in the young lateral roots, and between the regions of root elongation and maturation of the primary root. The use of BDPS (bathophenanthrolinedisulfonate) to trap Fe2+ did not affect the release of H+ ions or reduction by T3238FER roots. BPDS did not decrease Fe uptake until it exceeded the Fe concentration in the nutrient solution. A sevenfold increase in BPDS caused a threefold decrease in Fe taken up by the plant. Fe3+ is reduced to Fe2+ at root sites accessible to BPDS. Adding Zn decreased the response to Fe stress.Iron stress initiates the development of lateral roots, and we propose that most Fe enters the plant through these roots. The iron moves through protoxylem into the metaxylem of the primary root and then to the top of the plant as Fe citrate. Root environmental factors that are competitive or inhibit Fe‐stress response, or genotypes that fail to respond to Fe stress, contribute to the development of Fe deficiency in plants.
Thermal and Ionic Factors in the Ultraviolet Photolysis of Plant Cell Membranes
Authors: SIEGEL S. M. , CORN CAROLYN 
Published: April 2006

AbstractThe exposure of red beet root tissue to ultraviolet (254 nm) at 2 × 106 erg × cm−2× min−1 (0.2 J × cm−2× min−1) causes release of betacyanin after a 20 minute induction period. Ultraviolet‐photolysis is temperature‐sensitive having a thermal threshold at about 10°C. Reduction in pigment release was effected by chlorides of Mg, Ca and Sr, but not by Li, Na or K. This effect was marked but not complete, even at 40 mM concentration.It is concluded that photolysis is indirect, and involves a lytic factor, possibly an oxidant, derived from an original photochemical product.
Multiphasic Uptake of Sulfate by Barley Roots I. Effects of Analogues, Phosphate, and pH
Authors: VANGE MARTA S. , HOLMERN KARI , NISSEN PER 
Published: April 2006

AbstractFor sulfate uptake by barley roots, competition studies reveal that uptake and phase transitions are caused by interaction of ions with separate sites on or in the plasmalemma. Uptake is competitively, and unequally, inhibited by sulfate analogues but not by other divalent anions. In contrast, divalent phosphate and di‐ and trivalent pyrophosphate are equally effective in causing transitions. Phosphate is taken up mainly or entirely as H2PO4− by a similar but separate multiphasic mechanism. At pH 8, sulfate uptake is mediated by fewer phases than at low and intermediate pH.
Oscillatory Transpiration and Water Uptake of Avena Plants IV. Transpiratory Response to Sine Shaped Light Cycles
Authors: BROGÅDH T. , JOHNSSON A. 
Published: April 2006

AbstractThe transpiration rate of individual 6‐day‐old oat plants was forced to oscillate by cyclic sine‐shaped changes in the leaf irradiance (frequency 2 cycles h−1, amplitude and average value 1.4 mW cm−2, red light 620–800 nm). By means of a specially designed cuvette with three chambers the transpiration rate from three different segments of the leaf could be measured simultaneously. The leaf segments were illuminated individually and the illumination on each leaf segment could be modulated independently.The experiments showed that there was a strong correlation between the transpiration rates from the different leaf segments, dependent on a coupling mechanism in the plant. The coupling phenomenon disappeared when the root system was eliminated or when the water potential of the root medium was lowered. It was experimentally shown that CO2 diffusion in the leaf could not be the primary cause for the coupling. Therefore the stomatal dependence on the leaf water potential was considered the most probable reason for the coupling.The frequency of the forcing light cycles could be linearly changed during an experiment and this swept‐frequency technique was used to obtain a frequency response of one single oat plant. The technique made it also possible to study the strength of the coupling between different leaf segments.
Phylloquinone (Vitamin K1) Levels in Leaves of Plant Species Differing in Susceptibility to 2,4‐Dichlorophenoxyacetic Acid
Authors: JANSSON OWE 
Published: April 2006

AbstractPlant species differing in susceptibility to 2,4‐dichlorophenoxyacetic acid (2,4‐D) were examined as to the level of phylloquinone (K) in the leaves. The K level was found to be considerably higher in several plants resistant or moderately resistant to 2,4‐D (Aegopodium podagraria L., Galium mollugo L., Lamium album L., Matricaria chamomilla L., Oxalis acetosella L., Stellaria media (L.) Vill., Viola arvensis Murr.) than in Chenopodium album L. and Sinapsis arvensis L. which are susceptible to 2,4‐D. Capsella bursa‐pastoris (L.) Med. and Plantago major L. (both moderately susceptible) and a few resistant or moderately resistant species (Agropyron repens (L.) PB., Anthriscus silvestris (L.) Hoffm., Triticum aestivum L.) had intermediate K levels. Cirsium arvense (L.) Scop. (susceptible) had a relatively high level of K. It is possible that a high K level in the plant can be of importance in the resistance to 2,4‐D.
Influence of Growth Conditions, Metabolic Inhibitors, and Phenolic Compounds on the ATP Pool in Fomes annosus
Authors: JOHANSSON MARTIN , HÄGERBY ELISABETH 
Published: April 2006

AbstractThe ATP pool of growing fungal mycelia, particularly Fomes annosus, has been determined. The ATP level varied during the different growth phases and correlated with the variations in the economic coefficient. Common uncouplers (at concentrations similar to those used in mitochondrial tests) decreased the ATP pool very rapidly. The size of the pool often fell 50–80% before the O2 uptake decreased below that of the control and was accompanied by an increasing exudation of inorganic phosphate. Phenolic compounds added to the medium stimulated the lacease activity, generally in combination with a decrease in the ATP level.
Lipid Composition of Whole Roots and of Ca2+, Mg2+‐activated Adenosine Triphosphatases from Wheat and Oat as Related to Mineral Nutrition
Authors: KUIPER P. J. C. , KÄHR M. , STUIVER C. E. E. , KYLIN A. 
Published: April 2006

AbstractLipid composition of whole roots of wheat (Triticum vulgare Vill. cv. Svenno Spring Wheat) and oat (Avena sativa L. cv. Brighton) and of cell wall fractions, mitochondrial fractions and microsomal fractions of these roots were studied. Lipid composition depended upon the level of mineral nutrition. In wheat total phospholipids, phosphatidyl choline and sulfolipid content was highest in the roots grown at the higher salt concentration, while the reverse was true for oat roots. In both species glycolipid and sterol content was lower in the high salt roots, at the same time as higher proportions of them were built into the microsomal fraction. Phosphatidyl choline content of the wheat root membrane fractions increased with the salt level, while the opposite occurred in the oat roots.The phosphatidyl choline content may be correlated with the (Ca2+, Mg2+)‐stimulated ATPase activity.
The Initiation of an Endogenous Rhythm Affecting Flower Bud Formation in Pharbitis nil
Authors: PARASKA JOHN R. , SPECTOR CALVIN 
Published: April 2006

AbstractWhen seedlings of Pharbitis nil are presented with an inductive dark period at varying times, they show a circadian fluctuation in the number of flower buds initiated. This study determines if this fluctuation is due to the plant's perception, at the time of the inductive dark period, of either a rhythmic, external, environmental stimulus or of an endogenous rhythm.Using experimental designs in which the time of planting, the time of seedling emergence from the soil, and the time at which the presentation of an inductive dark period are varied, this fluctuation in flower bud formation is shown to be due to an endogenous rhythm initiated or synchronized by some event associated with the emergence of the seedlings from the soil. The results are inconsistent with the hypothesis that the plants are responding to rhythmic external stimuli.
Effects of Fluoride on Mitochondrial Activity in Higher Plants
Authors: MILLER J. E. , MILLER G. W. 
Published: April 2006

AbstractThe effects of fluoride on respiration of plant tissue and mitochondria were investigated. Fumigation of young soybean plants (Glycine max Merr. cv. Hawkeye) with 9–12 μg × m−3 HF caused a stimulation of respiration at about 2 days of treatment followed by inhibition 2 days later. Mitochondria isolated from the stimulated tissue had higher respiration rates, greater ATPase activity, and lower P/O ratios, while in mitochondria from inhibited tissue, all three were reduced.Treatment of etiolated soybean hypocotyl sections in Hoagland's solution containing KF for 3 to 10 h only resulted in inhibition of respiration. Mitochondria isolated from this tissue elicited increased respiration rates with malate as substrate and inhibited respiration with succinate. With both substrates respiratory control and ADP/O ratios were decreased.Direct treatment of mitochondria from the etiolated soybean hypocotyl tissue with fluoride resulted in inhibition of state 3 respiration and lower ADP/O ratios with the substrates succinate, malate, and NADH.Fluoride was also found to increase the amount of osmotically induced swelling and cause a more rapid leakage of protein with mitochondria isolated from etiolated corn shoots (Zea mays L. cv. Golden Cross Bantam).The results are discussed with respect to possible effects of fluoride on mitochondrial membranes.
Morphological and Physiological Effects of Maleic Hydrazide on Tobacco
Authors: BUSH L. P. , SIMS J. L. 
Published: April 2006

AbstractTobacco plants (Nicotiana tabacum cv. Burley 21) were cultured in the greenhouse to the 18‐leaf stage. The apical meristem was removed and subsequent axillary bud growth was removed by hand (controls) or axillary bud development was inhibited by application of maleic hydrazide. Compared with the controls, maleic hydrazide treated plants had a decreased stem diameter and stem weight, but an increased leaf weight and leaf weight/area. Plant height and leaf area were the same for both treatments. Maleic hydrazide inhibited translocation of 14C from a single leaf exposed to 14CO2. Respiration was greater than in the controls three days after application of maleic hydrazide, but 9 and 14 days after application there were no differences in respiration between the two treatments. Maleic hydrazide did not affect photosynthetic activity.
Growth and Dormancy in Norway Spruce Ecotypes (Picea abies) I. Interaction of Photoperiod and Temperature
Authors: HEIDE OLA M. 
Published: April 2006

AbstractGrowth and dormancy as affected by photoperiod and temperature have been studied in Norway spruce ecotypes of different latitudinal and altitudinal origin. First‐year seedlings were used.In all ecotypes apical growth cessation and terminal bud formation occurred within 2 weeks after exposure to SD at temperatures of 18 to 24°C. At lower temperatures or at near‐critical photoperiods the response was delayed. The critical photoperiod for apical growth cessation varied from 21 hours in ecotype Steinkjer, Norway (64°N) to about 15 hours in ecotype Lankowitz, Austria (47°04′N). High‐elevation ecotypes also had longer critical pholoperiods than low‐elevation ecotypes from the same latitude.A detectable growth depression resulted from as little as 1 or 2 SDs of 10 hours, and with 4 or more SDs apical growth cessation took place. In contrast to the situation in the shoot, root growth was not affected by photoperiod. Accordingly, the top:root ratio is drastically affected by photoperiod.The critical photoperiod for cambial growth was shorter than that for apical growth in all ecotypes and cambial growth cessation was delayed for several weeks compared with cessation of apical growth. A transition to formation of late‐wood tracheids with thick walls and narrow lumens took place upon exposure to SD.The photoperiodic effects were significantly modified by temperature, but the critical photoperiods were only slightly changed by temperature in the range of 12 to 24°C. However, a 10‐hour “night” at 4°C caused growth cessation in continuous light in four ecotypes tested.Temperature optimum for apical growth under non‐limiting photoperiods (24 hours) was 21°C in all ecotypes, but with little difference among 18,21 and 24°C. The Q10 for apical growth was 3.5 in the temperature range 12 to 18°C. The growth potential as determined in 24‐hour photoperiods was not significantly different among the various ecotypes except for one northern eco‐type which was clearly inferior to the others. However, the growth of ecotype Steinkjer (64°N) was greatly suppressed even by the long midsummer days at 59°40′N, thus demonstrating the misleading impression one gets of the growth potential of northern ecotypes when they are moved southwards.
Distribution of Chlorophyll between the Two Photoreactions in Photosynthesis of the Blue‐Green Alga Anacystis nidulans Grown at Two Different Light Intensities
Authors: ÖQUIST GUNNAR 
Published: April 2006

Abstract Anacystis nidulans was grown in white light of two different intensities, 7 and 50 W ·m−2. The in vivo pigmentations of the two cultures were compared. The ratio phycocyanin/chlorophyll a was 0.96 for cells grown at 7 W · m−2 and 0.37 for cells grown at 50 W · m−2. Phycocyanin‐free photosynthetic lamellae (PSI‐particles) were prepared, using French press treatment and fractionated centrifugation. Algae grown in the irradiance of 50 W · m−2 showed a chlorophyll a/P700 ratio of 260, while algae grown at 7 W · m−2 had a value of 140. Corresponding PSI‐particles showed values of 122 and 109 respectively. Light‐induced absorption difference spectra measured between 400–450nm indicated different ratios between cytochrome f and P700 in the two algal cultures.Enhancement studies of photosynthetic oxygen evolution were carried out. When a background beam of 691 nm was superimposed upon a signal beam of 625 nm, good enhancement was observed for both cultures. With the wavelengths 675 and 691 nm together a pronounced enhancement could be detected only in algae grown at the higher light level.Absorption spectra recorded on whole cells at 77°K revealed a small shift of the main red chlorophyll a absorption peak caused by light intensity.It is proposed that the reduction of the phycocyanin/chlorophyll a ratio in high light‐grown cells is accompanied by an increased energy distribution by chlorophyll a into PSII.
Light‐Induced Changes in Pigment Composition of Photosynthetic Lamellae and Cell‐Free Extracts from the Blue‐Green Alga Anacystis nidulans
Authors: ÖQUIST GUNNAR 
Published: April 2006

Abstract Anacystis nidulans was grown at two different levels of white light, 7 and50 W.m−2. The cells were disrupted through French press treatment, and phycocyanin‐free photosynthetic lamellae were obtained from the homogenate by fractionated centrifugation. Comparative absorption studies of the lamellae revealed that high intensity gave an increased carotenoid content relative to chlorophyll a. The spectral characteristics of the cell‐free supernatants were also analysed. The high light intensity gave increased contents of both pteridines (410 nm) and allophycocyanin (655 nm) compared with the contents in algae grown at the low light level.
Compounds Association with Cytokinin Activity in Fruitlets and Tracheal Fluid of Gossypium hirsutum
Authors: TAYLOR P. A. , KOSUGE T. , DeVAY J. E. 
Published: April 2006

AbstractCompounds that account for cytokinin activity in fruitlets and tracheal fluids of cotton (Gossypium hirsutum L.) were determined using preparations purified by thin‐layer chromatography and gas–liquid chromatography and bioassayed with cultures of soybean stem callus tissue. At least five substances were found that stimulated growth of callus tissue. Among these, adenine and adenosine accounted for most of the growth stimulation of callus tissue. A compound with cytokinin activity was isolated with TLC properties similar to other known cytokinins, but its identity as zeatin, dihydrozeatin or N6‐(Δ2‐isopentenyl)‐adenine was not confirmed using GLC and GLC combined with mass spectrometry. It was estimated that less than 1% of the cytokinin activity of this unknown substance could have been due to N6‐substituted adenine derivatives.
Restoration of Photosynthesis in Dried Tobacco Leaf Tissue
Authors: GRAZIANI Y. , LIVNE A. 
Published: April 2006

AbstractA comparison of 14CO2 fixation rates in dehydrating tobacco leaf tissue, either intact or epidermis‐free, shows that stomatal closure is the primary cause for photosynthetic reduction due to dehydration. Rehydration of the dried, epidermis‐free tissue was accompanied by restoration of photosynthetic activity. The restoration was not only affected by hydration level but was notably time‐dependent, apparently for reorganization of the photosynthetic apparatus.
Induction of Biplanar Growth in Fern Gametophytes
Authors: RAGHAVAN V. 
Published: April 2006

AbstractIn constant white light, protonemata of different ages of Asplenium nidus produce a fixed number of cells before they become biplanar. Protonemata with a lower initial cell number require a longer time to become biplanar than those with a higher initial cell number. Increasing the photoperiod or the light intensity reduces the cell number in the filament at the time of initiation of biplanar morphology. It is suggested that inductive light acts directly on cell metabolism to induce biplanar morphology, rather than indirectly by inducing mitotic activity.
Root Formation in Pea Cuttings III.
Authors: ERIKSEN E. NYMANN 
Published: April 2006

AbstractCuttings were either decapitated or both decapitated and disbudded at different time intervals. Cytokinin, at different concentrations, was applied to the cuttings in lanoline.Higher concentrations of cytokinin inhibited root initiation during the early stage. However, the inhibitory effect of cytokinin disappeared during the later stage of root initiation.Lower concentrations of cytokinin promoted the root initiation during the early stage. This effect was observed on cuttings which were only decapitated.These results seem to indicate that the influence of cytokinin changes with the stage of development.There seems to be an interaction between cytokinin and one or more other growth factors. A possible reason for this may be that cytokinin, in higher concentrations, produces inhibitory effects during the early part of root initiation by blocking the activity of auxin. The loss of the inhibitory effect of cytokinin during the later part of the initiation phase suggests that, at this stage, developing root primordia are capable of controlling the level of active cytokinin and thus do not react to the exogenous application of cytokinin.
Cold Hardiness of Plants: Correlation witb Changes in Electrophoretic Mobility, Composition of Amino Acids and Average Hydrophobicity of Fraction‐1‐protein
Authors: SHOMER‐ILAN ADIVA , WAISEL Y. 
Published: April 2006

AbstractCold‐hardening of cabbage plants, involves changes in Fraction‐1‐protein. Such changes are correlated with factors affecting hardening e.g. temperature, light, mineral nutrition and age. A 24‐h exposure to 5°C conditions induced the formation of a new protein with a different amino acid composition, lower average hydrophobicity and a higher hydrophility.
Activity Changes in Selected Enzymes from Soybean Leaves Following Ozone Exposure
Authors: TINGEY DAVID T. , FITES ROGER C. , WICKLIFF CARLOS 
Published: April 2006

AbstractSoybeans [Glycine max(L.) Merr.] were harvested at various time periods after a 2‐h exposure to either 0 or 0.5 μ1/1 ozone to determine the effects of ozone on selected enzymes. Carbohydrate metabolism was modified by a depression of glyceraldehyde 3‐phaosphate dehydrogenase and an activation of glucose 6‐phosphate dehydrogenase. Ozone did not alter the levels of RNase, protease, acid phosphatase or esterase as might be expected if ozone enhanced leaf senescence. The activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase were initially depressed and then stimulated following the ozone exposure. The reactions of soybeans to an acute ozone stress were more nearly akin to those elicited in response to other stresses than to the process of senescence.
Auxin Synthesis in Crown Gall Tumor Tissue: A Comparison of Three Putative Precursors
Authors: DAVIES FREDERICK S. , MAU SHIAO‐LIM CHEN , NOODÉN LARRY D. 
Published: April 2006

AbstractAxenic crown gall tumor callus (from Vinca rosea L.) which is known to synthesize its own auxin is able to convert exogenous 14C‐indole or tryptamine to indoleacetic acid [5.4 and 10 × 10−6μmol × h−1× (g fr wt)−1 respectively], but little or no 3H‐tryptophan is converted [less than 6.4 × 10−8×μmol × h−1× (g fr wt)−1].
Lipid Peroxidation and Chlorophyll Destruction Caused by Diquat during Photosynthesis in Scenedesmus
Authors: VAN RENSEN J. J. S. 
Published: April 2006

AbstractLipid peroxidation and decrease in chlorophyll‐a and chlorophyll‐b content in Scenedesmus cells was followed in the course of time. Addition of diquat to the algae in the light causes lipid peroxidation and a decrease in chlorophyll content. This decrease is mainly due to chlorophyll‐a, the concentration of chlorophyll‐b remains more or less constant during the experiment. In the presence of N′‐(3,4‐dichlorophenyl)‐NN‐dimethylurea (DCMU), of cysteine, or during nitrogen‐flushing of the algal suspension, the lipid peroxidation caused by diquat is strongly suppressed. The decrease in chlorophyll‐a content caused by diquat is somewhat smaller in the presence of DCMU or during nitrogen‐flushing than with diquat alone, but is not influenced by cysteine. The chemical antioxidant butylated hydroxytoluene does not affect lipid peroxidation and chlorophyll destruction caused by diquat.
Effect of EMD‐IT‐5914 on Chlorophyll Synthesis in Leaves of Pennisetum typhoides Seedlings
Authors: HAMPP R. , SANKHLA N. , HUBER W. 
Published: April 2006

AbstractEMD‐IT‐5914 (5‐dimethylamino‐methylene‐2‐oxo‐4‐phenyl‐2,5‐dihydrofurane‐carbonitril‐(3)) inhibited chlorophyll a formation almost completely and chlorophyll b and total carotenoids up to 80% of the control, but did not appreciably affect the activity of the enzyme system succinyl‐CoA synthetase/δ‐aminolevulinic acid synthetase. The activity of δ‐aminolevulinic acid dehydratase was not found limiting. In contrast, the herbicide strongly inhibited the activity of porphobilinogenase, and the reaction kinetics pointed towards a non‐competitive type of inhibition. The results are discussed in relation to the possible role of EMD‐IT‐5914 in chlorophyll biosynthesis.