bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Stress in Birch Seedlings
Authors: INGESTAD TORSTEN 
Published: April 2006

AbstractIn a series of experiments with nitrogen stress, optimum and supra‐optimum nitrogen supply, N, K, P, Ca, and Mg have been analysed in leaves, stems and roots of birch seedlings (Betula oerrucosa Ehrh.). Growth rate was strongly and linearly correlated with the nitrogen status of the seedlings within the whole sub‐optimum range. Seedling weight was equally strongly correlated with nitrogen status, although exponentially. Various expressions for growth rate and nitrogen status give similar results. Nitrogen efficiency (dry matter produced per unit nitrogen) decreased with increasing nitrogen status, but nitrogen productivity (dry matter produced per unit nitrogen and time) increased up to optimum.The maintenance of a stable nitrogen status in the seedlings and a stable growth rate requires an accurate and closely controlled technique of nitrogen addition. Because of the exponential relation between seedling weight and sub‐optimum nitrogen status and a rapid decrease in the supra‐optimum range, a strict control of the optimum status is necessary to maintain maximum growth.
Leaf Conductance as Related to Xylem Water Potential and Carbon Dioxide Concentration in Sitka Spruce
Authors: BEADLE C. L. , JARVIS P. G. , NEILSON R. E. 
Published: April 2006

AbstractCurrent year shoots of Sitka spruce [Picea sitchensis Bong. (Carr.)] from the forest canopy were equilibrated in a leaf chamber. The shoots were excised in air, and removed at differing times in order to establish a relationship between stomatal conductance and xylem water potential. The experiment was repeated at five ambient CO2 concentrations. A second set of excised forest shoots, and shoots excised from 2‐year‐ old nursery seedlings were allowed to evaporate freely in a controlled environment wind tunnel until a constant rate of transpiration was measured, to establish a relationship between cuticular conductance and xylem water potential.Cuticular conductance was estimated to be 0.012 cm s‐1 at high water potential and declined linearly to 0.007 cm s‐1 at −3.5 MPa. The implication of this decline in the subsequent calculation of stomatal and mesophyll conductance is considered.Stomatal conductance remained constant at water potentials above −1.4 MPa and was not affected by ambient carbon dioxide concentrations between 20 and 600 cm‐3. At lower water potentials, stomatal conductance declined and approached zero at −2.5 to −2.6 MPa. The results suggest that stomatal aperture is not controlled by either ambient or intercellular space carbon dioxide concentration, and that stomatal closure at low water potential is unlikely to be mediated by carbon dioxide.
Freeze‐Preservation of Rice Cells Grown in Suspension Culture
Authors: SALA F. , CELLA R. , ROLLO F. 
Published: April 2006

AbstractA simple procedure has been worked out for the freeze‐preservation of rice (Oryza sativa L.) cells grown in suspension culture. The protocol differs in some interesting aspects from those established for other organisms. A peculiar feature of this procedure is that growth of freeze‐recovered rice cells resumes after an extremely short lag period of 2–8 days and proceeds with a growth rate identical to that of untreated cells. This, together with data obtained with viability tests, rules out the possibility that selection of freeze‐resistant mutant cells may occur, as postulated with other plant cells where growth resumption was considerably delayed in time.The viability of freeze‐recovered rice cells, when assessed at time zero after thawing by measuring the mitochondrial respiratory efficiency, was 60–65% of that of untreated cells. However, the limits of this and other viability tests in determining the efficiency of the freeze preservation methods and the percentage of surviving cells were shown by experiments in which cell viability and cell growth were followed in cultures initiated with freeze‐recovered rice cells.
Exo‐ and Endo‐Cellular Cellulase and Polygalacturonase in Abscission Zones of Developing Orange Fruits
Authors: HUBERMAN M. , GOREN R. 
Published: April 2006

AbstractThe activity of cellulase, cellulase‐isoenzymes and polygalacturonase (PG) in the shoot/peduncle and calyx abscission zones (AZ‐A and AZ‐C, respectively) of young and mature Shamouti orange (Citrus sinensis (L.) Osbeck) fruit explants was tested after extraction of total enzymes from either exo‐ or endo‐cellular fractions from fruits treated with ethylene or 2,4‐D. Ethylene enhanced and 2,4‐D delayed both abscission and the activity of exo‐ and endo‐cellular cellulase and PG. When tested separately in the exo‐ and endo‐cellular fraction, the effects of both growth regulators on the activity of almost all cellulase isoenzymes were similar, irrespective of their location in the tissue. In mature fruits no abscission occurred in AZ‐A, and yet the activity of cellulase and PG was regulated by the hormones as in abscising AZs. This was also true for total activity of exo‐ and endo‐cellular cellulase and PG. Similar effects were observed when the activity of cellulase isoenzymes was tested in AZ‐A of non‐abscising mature fruits. It is suggested that whenever the increase in activity of the hydrolytic enzymes, and especially cellulase, is not followed by abscission, the substrate is either immune or not available to the enzymes.
Seasonal Levels of Abscisic Acid in Buds and Stems of Acer saccharum
Authors: DUMBROFF E. B. , COHEN D. B. , WEBB D. P. 
Published: April 2006

AbstractChanges in abscisic acid (ABA) were followed in the buds and youngest stems of 6‐year‐old sugar maple (Acer saccharum Marsh.) saplings at approximately monthly intervals during the year. High levels present in the buds in July and August showed a moderate decline through early October, but subsequently increased following leaf fall and reached the maximum values detected during the study in November and December. Thereafter ABA fell sharply, reaching its lowest point immediately prior to budbreak in early May. While ABA in the stems followed a somewhat similar pattern, only minor changes were observed in the relatively low values detected between June and November. Except for the spring months, when concentrations of ABA in the stems and buds were at minimum levels, the buds always contained several times more inhibitor per unit dry weight of tissue. Analysis of selected samples from both tissues showed that bound (alkaline‐hydrolyzable) ABA increased during the overwintering season, with the highest values noted in the spring. Although the patterns of change observed in this study are indicative of a role for ABA in the overwintering process, ABA does not appear to be the primary endogenous factor responsible for initiation of the dormant state.
Relationships between Bulb Size, Apex Size and Flowering in Bulbous Iris cv. Ideal
Authors: DOSS ROBERT P. , CHRISTIAN JAMES K. 
Published: April 2006

AbstractLarge, retarded bulbs of the Iris cv. Ideal flower readily after exposure to appropriate preplanting conditions, whereas smaller bulbs flower with decreased frequency. Flower initiation occurs when apices from large, retarded bulbs are cultured on either Murashige‐Skoog medium supplemented with gibberellic acid, or on the same medium without gibberellic acid on which scales from large bulbs have been incubated. Since floral initiation seldom occurs in explants from small bulbs, it is likely that reduced flowering of small bulbs relates in part to characteristics of the apical meristem.Apical dome diameter is one characteristic of retarded (and freshly dug) bulbs that is positively correlated with bulb size. However, whereas prolonged storage at retarding temperature increases the frequency of flowering of smaller bulbs, there is not a concomitant increase in apical dome diameter. Moreover, the ratio of apical dome diameter to bulb size in freshly dug bulbs does not increase measurably with later digging date indicating that apical dome size is not correlated with bulb maturity.
The Role of Endogenous Auxins and Ethylene in the Formation of Adventitious Roots and Hypocotyl Hypertrophy in Flooded Sunflower Plants (Helianthus annuus)
Authors: WAMPLE ROBERT L. , REID DAVID M. 
Published: April 2006

AbstractThe role of ethylene and auxins in flood‐induced adventitious root formation and hypocotyl hypertrophy in sunflower (Helianthus annuus L. cv. Russian) plants was studied. Flooding without aeration (F) resulted in a steady increase in ethylene in hypocotyls, and flooding with aeration (FA) caused a transient increase. Low light intensity increased ethylene levels but decreased adventitious root formation. Treatment of shoots with benzyladenine (BA) increased ethylene content in non‐flooded (NF) but not in F or FA shoots.Twenty‐four hours of flooding brought about a rise of endogenous indole‐acetic acid (IAA) in hypocotyls. 14C‐IAA applied to the shoot accumulated more in F and FA hypocotyls than in NF hypocotyls, and BA reduced this accumulation. There was less IAA metabolism in F and FA than in NF hypocotyls.Tri‐iodo benzoic acid (TIBA) applied to the hypocotyls of F plants inhibited root production. Benzyladenine (BA) applied to the leaves had similar effect but was not effective when supplied to the shoot apex. BA did not inhibit flood‐induced hypocotyl hypertrophy. Ethrel did not affect adventitious root formation in NF plants but did increase hypocotyl thickening.It is concluded that flood‐induced adventitious root formation is stimulated primarily by an accumulation of auxins in the hypocotyls. Increases in ethylene might cause this auxin build up. Hypocotyl hypertrophy is presently thought to be the result of an interaction of auxin and ethylene with ethylene being the major factor.
Ca2+ and Mg2+‐Stimulated ATPases from Roots of Plantago lanceolata, Plantago media and Plantago coronopus: Response to Alterations of the Level of Mineral Nutrition and Ecological Significance
Authors: KUIPER DAAN , KUIPER PIETER J. C. 
Published: April 2006

AbstractGrowth of Plantago lanceolata L., P. media L. and P. coronopus L. was followed at two levels of mineral nutrition (low‐salt and high‐salt). In addition the response of transfer of plants from low‐salt conditions to high‐salt conditions and vice versa was studied. Growth of these Plantago species was not much affected by the nutritional level. P. coronopus showed the least dependence on the level of mineral nutrition.The Ca2+‐ and Mg2+‐stimulated ATPase activity of microsomal preparations of the roots of Plantago was also studied. A pH optimum at pH 6.5 was observed in all species, together with a relatively high ATPase activation by Mg2+ in P. lanceolata, by Ca2+ in P. media, and by both ions in P. coronopus. The specific activity of the ATPases was highest in preparations from low‐salt roots.The three species all occur in relatively nutrient‐poor habitats, but they are at the same time particularly adapted to circumneutral soils (P. lanceolata), to Ca2+‐rich soils (P. media) and to alternating levels of mineral nutrition (P. coronopus). The properties of the ATPases (Km, Vmax, protein content) and the growth are discussed in relation to these ecological properties of the species.
The Effect of Reduced Light Intensity and Sub‐optimal Potassium Supply on N2 Fixation and N Turnover in Rhizobium Infected Lucerne
Authors: FEIGENBAUM SALA , MENGEL KONRAD 
Published: April 2006

AbstractThe effect of low light intensity and suboptimal potassium supply on the fixation of molecular nitrogen by root nodules and the nitrogen turnover in the host plant was studied in Medicago sativa using 15N labelled molecular nitrogen. For the application of 15N2 labelled gas a special box was used. Both low light intensity and a low potassium supply resulted in a substantial growth depression. In particular the protein content of tops, roots and nodules was lower in the plants of the low light intensity treatment as compared with the control plants. Decreasing potassium supply had a similar but less‐pronounced effect on protein content. The low protein content was not a consequence of a lack of soluble amino nitrogen or NH3, since these fractions were influenced to a lesser degree by the reduced light intensity and by the low potassium supply. This observation is supported by the data obtained with 15N. N2 fixation and NH3 assimilation were affected by both low light intensity and low K application to the same degree as the overall metabolism, thus showing no particular response to the treatments applied.
Immunochemical Identification Of α‐Amylass In Developing, Mature And Germinated Triticale Seeds
Authors: DAUSSANT J. , HILL R. D. 
Published: April 2006

AbstractExtracts from triticale (Triticale hexaploide Lart.) cultivar 6A190 kernels harvested at 10 days post anthesis (developing), 41 days post anthesis (mature) and after 7 days' germination, were analyzed for their α‐amylase isoenzymic composition by electro‐phoretic and immunochemical techniques. One antigenic α‐amylase (I) was common to both developing and germinated seeds but was present in greater quantity during germination. A second antigenic cr‐amylase (II) was found in germinated seeds only and was barely detectable, even in an inactive state, in developing seeds. A third antigenic α‐amylase (III) was found only in developing seeds. In mature seeds the α‐amylase (II) predominated. α‐Amylase (I) was also present but to a lesser extent than that found in developing seeds. It was concluded that the abnormally high levels of a amylase found in triticale 6A190 in the mature, non‐sprouted kernel arose due to a lack of dormancy in the grain, resulting in the de novo synthesis of α‐amylase (II).
Respiration of Senecio Shoots: Inhibition during Photosynthesis, Resistance to Cyanide and Relation to Growth and Maintenance
Authors: LAMBERS HANS , NOORD ROELIE , POSTHUMUS FREEK 
Published: April 2006

AbstractRespiration and dry matter producation were measured in shoots of senecia aquaticus Hill, which is flood tolerant and in shoots of S. jacobaea L., which is flood‐ sensitive. Both species were grown in culture solutions of high and of low oxygen concentration Growth of food of S. jacobaca was unaffected by a low oxygen supply bur growth of S. jacobaca was severly hampered by a low oxygen concentration in the root medium.Kinetic data about the rate of apparent photosynthesis at low oxygen conetration and different carbon dioxide concentrations indicated that at light saturation respiration was strongly repressed during photosynthesis. Shoot growth respiration, i.e. the amount of carbon dioxide produced for synthesis of shoot dry, matter appeared to be absent on S. jacobaea and to be very low (13.mg CO2/g dry shoots) in S. aquaticus. In comparison with values prepiration rate was 2.8. 2.0. 1.5 and 1.3mg CO2/h.g dry shoots in aerobically and anaerobically growth S. jacobaea and in aerobically and anaerobically growth S. aquabaea respectively. These values were also low in comprision with values previously found for roots of the same species.Shoot dark respiration on S. aquaticus was inbihitedd by a com bination on CN and salicylhydroxamic acid (SHAM), but not by application on one of these inhibitors alone. It was therefore concluded that an alternative oxidative pathway was present but not active in shoots of S. aquaticus. In the absence of inhibited of the cylochorome pathway.The low value of growth respiration and maintenance respiration rate in the shoots as compared with those in the roots of the investigated Sencio species are discussed in relation to the activity of the alternative oxidative pathway and to the possibilbity of a direct supply of ATP by photosynthesis intead of respiratory meta bolism.
The Influence of Cotyledons on Embryonic Axes during Induction of Dormancy in Corylus avellana
Authors: JARVIS B. C. 
Published: April 2006

AbstractRemoval of a cotyledon from dormant hazel seeds can stimulate germination. Such removal results in a stimulated synthesis of RNA in the embryonic axis within 24 h after the excision. Growth of isolated embryonic axes in liquid culture is partially inhibited by Actinomycin D, markedly inhibited by αfamanitin and totally prevented by cordycepin and cycloheximide. Early axis growth appears therefore to be dependent on transcription and/or poly adenylation of mRNA. Sucrose is necessary for growth of excised axes in liquid culture but when one‐third of one cotyledon is left attached to the axis sucrose is inhibitory to growth.
Oak Seedlings Grown in Different Light Qualities
Authors: AXELSSON LENNART , KLOCKARE BIRGITTA , SUNDQVIST CHRISTER 
Published: April 2006

AbstractSeedlings of oak (Quercus robur) were germinated in darkness for 3 weeks and then given continuous light or short pulses of light (5–8 min every day). The morphological development was followed during 25 days. In continuous white, blue, and red light the stem growth terminated after about 10 days by formation of a resting bud. At that time the seedlings were about 100 mm high. In con tinuous long wavelength farred light (wavelength longer than 700 nm) the stem growth including leaf formation was continuous without the formation of resting buds, and the stem length was about 270 mm after 25 days. The number of nodes developed became twice that of the seedlings grown in while light. The leaves became well developed in all light colours, but leaf areas were largest in plants cultivated in white light. Compared to dark grown seedlings the mean area per leaf was increased about five times in continuous long wavelength far red light. A supplement with short (5 min) pulses of red light each day increased the leaf area up to 20 times.The stem elongation showed a high energy reaction response, i.e. the stem length increased only in continuous long wavelength far‐red light but was not influenced by short pulses of red light or far‐red light. The leaf expansion, however, was increased by short pulses of red light with a partial reversion of the effect by a subsequent pulse of far‐red light. The fraction of the plant covered with periderm was higher in plants given continuous light. In respect to periderm inhibition continuous long wavelength far red light was the most effective. The transfer of seedlings from darkness to continuous white light gave anthocyanin formation in the stem 10–20 mm below the apex. This formation took place in the cortex and was evident in plants grown in darkness or under short pulses of light. Plants grown in continuous red, blue or long wavelength Far red light showed only traces of anthocyanin.
Oscillatory Transpiration of Avena Plants: Perturbation Experiments Provide Evidence for a Stable Point of Singularity
Authors: JOHNSSON A. , BROGARDH T. , HOLJE Ø. 
Published: April 2006

AbstractOscillatory plant water regulation of young Avena plants was studied. The period of the oscillations was around 40 min. Pulse perturbations were given to plants showing oscillations in the transpiration rate. Perturbations consisted in temporary irradiance changes of the leaf or in water potential changes around the root. The effect of the pulse perturbations on the amplitude of the oscillations was recorded. The oscillations could be permanently halted after a perturbation of suitable magnitude given at a suitable phase of The oscillations. A subsequent perturbation could restart the oscillations again.By means of simulations it was shown that a feedback model For the transpiration oscillations could explain the experimental outcome if a non finearity of a special kind was incorporated. The circadian eclosion rhythm of Drosophila pseudoobscura and the petal rhythm of Kalanchoe blossfeldiana show many features in common with the experiments reported. Biophysically the present results indicate that the transpiration oscillations of Avena plants have a stable point of equilibrium or a stable point of singularity.
Growth Substances and Dormancy in Ceratophyllum demersum
Authors: BEST ELLY P. H. 
Published: April 2006

Abstract Ceratophyllum demersum L. occurs in winter in the dormant form, in summer in the vegetative form. Factors that affect growth and dormancy in Ceratophyllum were studied. After several weeks of severe winter conditions the plants changed from dormant to quiescent state. Under natural conditions Ceratophyllum plants remain quiescent for several months, due to unfavourable growth conditions. Experimentally the dormant could also be broken by high and low temperature treatments (shocks), and most effectively by addition of GA, An attempt to induce dormancy in full grown plants by the addition of ABA under extreme summer or winter conditions proved unsuccessful.The IAA and ABA contents in the plants were measured during the year. In winter the concentration of ABA was high and that of IAA low, whereas in summer the IAA concentration increased and that of ABA was variable. IAA only slightly antagonized the inhibition of growth by ABA. Both the growth regulators were readily taken up from the culture medium, as was confirmed by a study with the radioactive labelled compounds. The uptake rate of IAA was significantly higher than that of ABA. being 762 μg and 3.26, μg per plant in 24 h, respectively. GA, was found to have a strong antagonistic effect on the ABA induced growth inhibition.The total GA activity in dormant and quiescent plants was similar, in full grown plants it was much lower. In the dormant state a large part of GA was in a bound form, whereas during quiescence relatively more GA occurred in a free state in the plants.
Corrélations de croissance entre le mycélium et les rhizomorphes chez le Sphaerostilbe repens
Authors: BOTTON BERNARD , CASALIS‐GOUGEROT CATHERINE 
Published: April 2006

Abstract Correlation of Growth between Mycelium and Rhizomorphs in Sphaerostilbe repens In Sphaerostilbe repens Berkeley and Broome, cultured on a solid medium in Petri dishes, growth of mycelium and chizomorphs depends on the thickness of the culture medium underlying the thallus. On shallow layers of agar medium, aggregated units were fewer and rhizomorph growth reduced. Vegetative mycelium which starts growth earlier than rhizomorphs contributed to inhibit the development of these latter. On deep layers of substrate, rhizomorphs were numerous, elongated rapidly, and eventually inhibited undifferentiated mycelium. – There was no evidence for the involvement of any inhibitor substance diffusing into culture medium or located in the thallus. Development of aerial mycelium and rhizomorphs, could, on the contrary, be interpreted as nutritional competition between these two parts of the colony.