bluuebunny/crossref_metadata_2025_split huggingface dataset:
Occurrence of esterified triterpenoid alcohols in the leaves of Pilosella officinarum
Authors: Karunen P. , Hakala K. , Heinonen S. 
Published: April 2006

The mature winter leaves of Pilosella officinarum coll. Schultz and Schultz contained 29 mg esterified triterpenoid alcohols (g dry weight)−1, of which over 80% was esterified with long‐chain (C16‐C18) fatty acids. The major fatty acids were 16:0, 18:2ω6 and 18:3ω3 and their amounts varied according to the season and stage of leaf development. In mature leaves the amount of triterpenoid alcohols esterified with long‐chain fatty acids varied only slightly with the season. The changes in the fatty acid proportions in late winter‐early spring, however, indicated a turnover in the esterified triterpenoid alcohol pool. In late winter after the snow had melted a 50% decrease occurred in the amount of triterpenoid alcohols esterified with short‐chain fatty acids. The amount of esterified triterpenoid alcohols in immature leaves was relatively low [4 mg (g dry weight)−1].In the mature leaves esterified triterpenoid alcohols were found in globules whose appearance varied greatly according to the season. The globules were partly dissolved in late winter, and this together with the activation of respiration, suggests that the globules function as short‐term energy reservoirs. Relationships between the appearance of lipid globules and the amount of esterified triterpenoid alcohols are discussed.
Photoautotrophic potato cells: Transition from heterotrophic to autotrophic growth
Authors: LaRosa P. Christopher , Hasegawa Paul M. , Bressan Ray A. 
Published: April 2006

Cells of potato (Solanum tuberosum L.) were obtained which were capable of photoautotrophic growth in liquid suspension culture under a photon flux density of 90–110 μmol m−2 s−1 PAR and in an atmosphere enriched with 2% CO2. These photoautotrophic cells contained between 100 to 200 μg Chl (g fresh weight)−1 and fixed CO2 at a maximum rate of 16 μmol CO2 (g fresh weight)−1h−1. In order to obtain cells capable of photoautotrophic growth it was necessary to adapt highly chlorophyllous heterotrophic cells (>50 μg Chl (g fresh weight)−1) for growth in medium with 2.5 g sucrose 1−1 (photomixotrophic cells). The photomixotropic cells had a Chl content of ca 100 μg Chl (g fresh weight)−1 and were capable of photosynthetic activity which allowed them to survive after sugars had been depleted from the medium. It was from the photomixotrophic cells that cells capable of photoautotrophic growth were obtained.Heterotrophic cells initially established in liquid medium with 25 g sucrose I−1 from chlorophyllous callus contained about 50 to 150 μg Chl (g fresh weight)−1. However, after 5 to 10 passages the Chl content decreased to a maximum of 15 μg Chl (g fresh weight)−1. These cells could not be adapted to photomixotrophic or photoautotrophic growth. These cells also were not able to regain Chl or initiate high rates of CO2 fixation during the stationary phase of growth as did photomixotrophic cells or chlorophyllous heterotrophic cells. The loss of Chl exhibited by the cells during adaption to heterotrophic growth could be attributed at least in part to unbalanced growth (when cell division and growth exceeds Chl accumulation). Sucrose appeared to have an inhibitory effect directly on photosynthesis independent of Chl accumulation.
Auxin effects on rooting in pea cuttings
Authors: Eliasson Lennart , Areblad Karin 
Published: April 2006

Light‐grown stem cuttingss of Pisum sativum L. cv. Weibull's Marma were rooted in a nutrient solution. The presence of 10 μM indolylacetic acid (IAA) in the solution for 24 h or longer periods decreased the number of roots subsequently formed to about 50% of control, provided IAA was present in the solution during any of the 4 first 24 h periods. Treatment for 6 h or shorter periods caused no or small response. IAA did not appreciably change the time needed for root formation, the time course of root appearance or the pattern of root distribution along the basal internode. IAA at 100 μM usually increased the number of roots although variable results were obtained with this IAA concentration.The number of roots was strongly increased by treatment with indolylbutyric acid (IBA) or 2,4‐dichlorophenoxyacetic acid (2,4‐D). None of these or other synthetic auxins decreased the number of roots in suboptimal concentrations. Experiments with 10 μM IBA showed that stimulation of rooting was obtained only if the auxin was present in the rooting solution for several days. Simultaneous treatment with IAA decreased the stimulating effect of IBA to some extent, whereas no such response was obtained if IAA was combined with 2,4‐D.IAA applied in lanolin to the stem of intact cuttings decreased the number of roots formed. Decapitation and debudding of the cuttings decreased the number of roots formed. If at least 2 leaves were left this decrease was efficiently counteracted by an optimal IAA dose applied to the upper part of the stem. A five times higher dose was less effective, indicating a negative effect on rooting also by IAA applied to the shoots.
Ethylene and apical dominance
Authors: Yeang A. Y. , Hillman J. R. 
Published: April 2006

Ethylene is involved in at least two discrete mechanisms in the control of apical dominance: the release of lateral buds from inhibition and their subsequent growth and development. Generally, high levels of freely diffusible ethylene in the apical region of the shoot are conducive to lateral‐bud‐outgrowth, while high ethylene levels in the region of the lateral buds themselves tend to be inhibitory. Threshold ethylene levels concerned with the release of buds from inhibition and with the growth that follows may differ between species. Thus, in some species (e.g. Gossypium) lateral‐bud growth proceeds in the continuing presence of ethylene supplied to the whole plant, whereas in others (e.g. Petunia) the growth of the released lateral buds occurs only when the ethylene is remaved.When ethylene production in Pisum nodal sections is enhanced by exomgenous auxin, growth of the attached buds is suppressed. In the intact plant system, unequivocal evidence has not been established for a role of endogenous ethylene acting directly on lateral buds to effect their inhibition. Apical dominance is not affected by the apptication of ethylene antagonists to the lateral buds of intact plants. Results from different studies have been inconsistent regarding the changes in endogenous ethylene levels in the node/lateral‐bud tissue when the plant is decapitated or when auxin is applied to the stump of the decapitated plant to maintain lateral bud inhibition.While exogenous ethylene supplied to the lateral bud generally increases inhibition, the availability of ethylene, regulated endogenously, is essential to the released bud on the decapitated plant in order to sustain its subsequent development into a lateral shoot. There is evidence that, in certain instances, endogenous ethylene may also be essential in the initial stages of bud development, e.g. in thee early growth that is promoted bmy auxin in Phaseolus or by kinetin in Avena.
Rapid isolation of plant peroxidase. Purification of peroxidase a from Petunia
Authors: van den Berg Bartel M. , van Huystee Robert B. 
Published: April 2006

A rapid isolation procedure was developed for purification of peroxidase a from Petunia hybrida. Rapid isolation was possible since about 15% of the extracellular protein from stem tissue obtained by vacuum infiltration followed by centrifugation of the tissue represents peroxidase. Purification of peroxidase a from intercellular fluid was achieved by two acetone precipitation steps followed by DEAE‐cellulose chromatography.Three different forms of peroxidase were eluted from DEAE‐cellulose at different NaCl concentrations. Isoelectric focusing showed, however, a pI of 3.8 for all three forms of peroxidase a. Only part of the peroxidase a enzymes bound to Concanavalin A indicating heterogeneity in the carbohydrate part. Homology of peroxidase a to the peroxidase G1 group from tobacco is discussed.
The perception of dusk signals in photoperiodic time‐measurement
Authors: Lumsden Peter J. , Vince‐Prue Daphne 
Published: April 2006

A critical duration of darkness must be exceeded for the photoperiodic induction of flowering in short‐day plants. This requires detection of the light/dark transition at dusk and the coupling of this information to a time‐measuring system.Lowering the Pfr/Ptot, ratio photochemically at the end of the day did not accelerate the onset of dark timing in Pharbitis nil Choisy cv. Violet. Time‐measurement was initiated when, with no change in spectral quality, the irradiance fell below a threshold value. Thus, if the light/dark transition at dusk is sensed by a reduction in Pfr, this reduction can be achieved as rapidly through thermal reactions as through photochemical ones. When given at hourly intervals during a 6‐h extension of a 24‐h main light period in white light, pulses of red light were as effective as continuous red light in delaying the onset of timing; pulses every 2 or 3 h were less effective. The effectiveness of intermittent red light indicates that phytochrome is the photoreceptor and the requirement for frequent exposures suggests that Pfr is lost rapidly in the dark. However, the red light pulses could not be reversed by far‐red light, which argues against this hypothesis. An alternative explanation is that the perception of light as being continuous occurs only when “new” Pfr is regenerated sufficiently frequently.The nature of the coupling of the dusk signal to the time‐measuring system is discussed and it is suggested that the effect of each red light pulse is to delay the phase of the photoperiodic rhythm by 1–3 h.
Variation in the lag phase and uniformity of the length of the rooting phase prior to adventitious root production in cuttings of Agathis australis
Authors: White Julie , Lovell Peter H. 
Published: April 2006

Cuttings of Agathis australis (D. Don) Lindl passed through a well‐defined series of morphological changes prior to root emergence. These phases were incorporated into a morphological index which can be used as a guide for the selection of cuttings at known developmental and anatomical stages. After a variable period (lag phase) during which no external change occurred there was an increase in stem diameter a few milimetres above the cut base. This swelling gradually increased in size and isolated bulges developed. Longitudinal splits then arose in the epidermis over the bulges, followed by root emergence through the splits. Root initiation occurred shortly after the sub‐basal swelling commenced in cuttings that eventually rooted. Removal of the basal 8 mm of a rooted cutting (which included the roots) usually led to re‐rooting of the cuttings. However, if the roots were merely trimmed off, the cutting never formed new roots and always died. The basal region apparently has the capacity to produce only one set of roots. Occasionally the stem diameter continued to increase and the swelling extended to include the basal region. Such cuttings never formed isolated wellings and never rooted.In general the younger the plant from which the cutting was taken, the shorter the lag phase and the higher the final percentage rooting. Cuttings taken from older plants had a lower rooting percentage and a more variable lag phase, which was related to the time of year the cuttings were taken since root emergence always occurred in spring. Irrespective of the age of the original material there was a constant time period (3–4 weeks) from root initiation to root emergence.
Stimulation par la lumière rouge lointain de la synthèse de la δ‐aminolévulinate déshydratase des cotylédons de radis
Authors: Huault Claude , Balangé Philippe Bruyant et Alain Pierre 
Published: April 2006

Stimulation of de novo synthesis of δ‐aminolevulinate dehydralasc of radishes grown under far‐red light.Density labelling studies of δ‐aminolevulinate dehydratase (ALAD) in cotyledons of radish (Raphanus sativus L. cv. Longue Rave Saumonée) seedlings demonstrate that far‐red light stimulates de novo synthesis of ALAD and that the turn‐over of this enzyme is very poor. Cycloheximide reduces considerably both the increase of ALAD activity and the incorporation of deuterium in ALAD, which indicates that ALAD synthesis depends upon cytoplasmic ribosomes.
Nutritional and root development factors affecting growth of tissue culture plantlets of loblolly pine
Authors: McKeand S. E. , Allen H. L. 
Published: April 2006

Tissue culture plantlets of loblolly pine (Pinus taeda L.) were compared to seedlings to quantify growth and developmental differences. The two plant types were grown in containers in a greenhouse and sampled periodically for twenty weeks. Dry weights and nitrogen and phosphorus concentrations of the shoots and roots were determined every two weeks.During the twenty weeks in the greenhouse, seedlings grew to a greater size than the plantlets, but the relative rates of growth were approximately equal. Plantlets had significantly lower concentrations of nitrogen and phosphorus per g of shoot dry weight. Seedlings were much more efficient at nutrient uptake per g of dry weight of root. Plantlets had thick, unbranched roots, which were inefficient at nitrogen and phosphorus uptake. Nutrient uptake based on an index of root surface area was equal in the plantlets and seedlings.The main differences between plantlets and seedlings apparently were related to root system morphology rather than physiological processes. The uptake of nutrients showed the greatest difference between the plant types.
Genotypic variation in tissue water relations of leaves and roots of black walnut (Juglans nigra) seedlings
Authors: Parker W. C. , Pallardy S. G. 
Published: April 2006

Genetic variation in the drought response of leaf and root tissue water relations of seedlings of eight sources of black walnut (Juglans nigraL.) was investigated using the pressure‐volume technique. Tissue water relations were characterized at three stages of a drying cycle during which well‐watered plants were allowed to desiccate and then were reirrigated.Sources varied both in the capacity for and degree of leaf and root osmotic adjustment, and in the mechanism by which it was achieved. A decrease in osmotic potential at the turgor loss point (ψπp) of 0.4 MPa was attributable to increased leaf tissue elasticity in seedlings of four sources, while seedlings of an Ontario source exhibited a 0.7–0.8 MPa decline in ψπpas a result of both increased solute content and increased leaf tissue elasticity. Seedlings of a New York source showed no detectable osmotic adjustment.In roots, decreased ψπp(osmotic potential at full hydration) and ψπpwere observed under drought. Sources that exhibited significant leaf osmotic adjustment also generally showed a similar response in roots. Tissue elasticity and ψπpof roots were higher than those of shoots, whereas ψπpof the two organs was similar for most sources. Because of greater elasticity, roots exhibited a more gradual decline in turgor and total water potential than did leaves as tissue relative water content decreased.
Growth inhibition of crown‐gall tissues in relation to the structure and activity of DNA
Authors: Le Goff L. , Roussaux J. , Cunha M. I. Aaron‐da , Beljanski M. 
Published: April 2006

The growth of crown‐gall cells cultured in vitro (Nicotiana tabacum L. cv. White Burley and Parthenocissus tricuspidata cv. Veitchii) is inhibited by alstonine (BG‐8), a plant alkaloid, the anti‐cancer effect of which has previously been demonstrated on animals and plants. The growth of normal cells is only slightly affected. The inhibitory effect of BG‐8 on crown‐gall cells is antagonized by indole‐3‐acetic acid (IAA) added to the culture medium. Kinetin associated with IAA does not prevent this inhibitory effect. BG‐8 present in the culture medium containing the two types of hormones seems to modify the later hormonal requirement of Parthenocissus crown‐gall tissues.BG‐8 exhibits high binding affinity for crown‐gall DNA and, therefore, strongly inhibits its in vitro synthesis. The alkaloid has practically no effect on DNA from healthy cells. The inhibition by BG‐8 is dependent on the level of DNA strand separation and on the origin and nature of the tissues (crown‐gall DNA is more destabilized than healthy DNA; DNA from habituated tissues is intermediate). IAA and kinetin have opposite effects on the in vitro strand separation of the DNAs from crown‐gall cells and, consequently, antagonistic effects on DNA replication (IAA stimulates and kinetin inhibits). It is possible to establish a close relationship between in situ development of crown‐gall tissues of the two species studied (in the presence or absence of BG‐8 or cell‐growth factors), in vitro DNA synthesis and DNA strand separation.
Nutrition and growth of coniferous seedlings at varied relative nitrogen addition rate
Authors: Ingestad Torsten , Kähr Monika 
Published: April 2006

The growth of two provenances of Pinus sylvestris L. were compared with two provenances of Picea abies (L.) Karst. and with Pinus contorta Dougl. when grown in solution cultures with low nutrient concentrations. Nitrogen was added at different exponentially increasing rates, and the other nutrients were added at a rate high enough to ensure free access of them to the seedlings.During an initial period of the culture (a lag phase), when the internal nutrient status was changing from optimum to the level of the treatment, deficiency symptoms appeared. The needles yellowed and the root/shoot ratio increased. The initial phase was followed by a period of exponential growth and steady‐state nutrition. The needles turned green again, and the root/shoot ratio stabilized at a level characteristic of the treatment. These patterns were the same as previously reported for other tree species.The relative growth rate during exponential growth was numerically closely equal to the relative nitrogen addition rate. The maximum relative growth rates were about 6 to 7.5% dry weight increase day‐1. This is a much lower maximum than for broad‐leaved species (about 20 to 30% day‐1) under similar growth conditions.The internal nitrogen concentrations of the seedlings and the relative growth rates were stable during the exponential period. Close linear relationships were found between these parameters and the relative addition rate up to maximum growth.During steady state the relative growth rates of the different plant parts were equal. However, there were large differences between genotypes in absolute root growth rate at the same seedling size because of differences in root/shoot ratio. Lodgepole pine had the highest root growth rate, whereas that of Norway spruce, especially the southern provenance, was remarkably low. Yet, Norway spruce had a high ability to utilize available nutrients. In treatments with free nutrient access, growth allocation to the shoot had a high priority in all genotypes, but there was still a marked tendency for luxury uptake of nutrients. Nitrogen productivity (growth rate per unit of nitrogen) was lower than in broadleaved species and highest in lodgepole pine. The relevance of the dynamic factors, i.e. maximum relative growth rate, nutrient uptake rate, nitrogen productivity, growth allocation and root growth rate, are discussed with regard to conifer characteristics and selection value.
A rapid assay for aluminium phytotoxicity at submicromolar concentrations
Authors: Kinraide Thomas B. , Arnold Robert C. , Baligar V. C. 
Published: April 2006

Investigations of Al phytotoxicity, including the identification of the Al species responsible for toxicity, require a rapid assay procedure employing very low concentrations of Al and a chemically simple rooting medium. Root elongation in newly germinated red clover (Trifolium pratense L. cv. Kenland) was inhibited by submicromolar concentrations of Al. Ca2+ at concentrations of at least 0.2 mM was essential for optimal elongation in control seedlings. Ca2+ also relieved Al toxicity with the net effect that maximum reduction of elongation by 1 μM Al was achieved at 0.2 mM Ca2+. Elongation in control seedlings was at least 90% of maximum from pH 4.5 to 5.7. Increases in pH relieved Al toxicity so that maximum sensitivity to 1 μM Al occurred at pH 4.7. As a consequence of these experiments and other considerations we chose for our basic assay a medium composed of 0.2 mM CaSO4 adjusted to pH 4.5 with H2SO4, variously supplemented with Al2(SO4)3.Day‐old seedlings were incubated in this aerated medium in the dark at 23°C for one day. No additions of other solutes increased the sensitivity of the assay, but amelioration of Al toxicity was effected by Mg2+, F‐, phosphate and citrate. Increases in ionic strength per se had comparatively little effect on the toxic effects of Al. Two barley cultivars (Hordeum vulgare L. cv. Dayton and Kearney) and two wheat cultivars (Triticum aestivum L. cv. Hart and Thorne) known to differ in sensitivity to Al were reliably separated at submicromolar Al concentrations by the assay procedure, which was slightly modified. Suggestions for the improvement of the assay and for applications to future research are offered.
Comparative investigations on the distribution of sucrose synthase activity and invertase activity within growing, mature and old leaves of some C3 and C4 plant species
Authors: Claussen W. , Loveys B. R. , Hawker J. S. 
Published: April 2006

Sucrose synthase (EC 2.4.1.13) activity in young growing leaves was highest in the leaf base in eggplants (Solanum melongena L.), cassava (Manihot esculenta Crantz), grapevine (Vitis vinifera L.), and in the leaf sheath of sugar cane (Saccharum of ficinarum L.) and maize (Zea mays L.). In addition, increasing sucrose synthase activity was measured towards the edge of growing eggplant leaves while the activity in mature leaves was highest in the midrib. The activity of acid and alkaline invertase was very low in the midrib but higher in the blade of fully expanded eggplant leaves. Highest invertase activities were found in younger growing leaves. It was concluded that in growing leaves a close relationship might exist between the activity of sucrose synthase and the import of sucrose from source leaves.Detachment of mature eggplant leaves led to a 2‐ to 3‐fold increase of sucrose synthase activity in blade and midrib of these leaves. In contrast, invertase activity decreased after detachment in both leaf blade and midrib. It was concluded that the rise in sucrose synthase activity might have been caused by the observed increase of sucrose concentration in detached leaves and that sucrose synthase might have an important role in the regulation of sucrose content of the conducting tissue.