bluuebunny/crossref_metadata_2025 huggingface dataset:
Gibberellin like Substances in Parts of Developing Barley Grain
Authors: MOUNLA M. A. KH.
Published: April 2006

In husks, the activity of gibberellin‐like substances extracted with aqueous methanol (M‐“free” GAs) showed a maximum on the 9th day after pollination. In developing embryos, M‐“free” GAs showed no biological activity, whereas biological active component(s) were obtained when the embryos were extracted with Tris buffer. The “free” GAs found in the buffer homogenates (B‐“free” GAs) of developing embryos showed a maximum of activity on the 33rd day after pollination. Bound GAs recovered from the precipitated protein of the buffer homogenate (“Protein‐bound” GAs) were found in embryo and endosperm.

Developing endosperm generally contains the major amount of the extractable gibberellin‐like substances. In this tissue, the amount of all examined fractions (M‐“free” GAs, B‐“free” GAs and “protein‐bound” GAs) increased after pollination to reach a maximum on the 21st day, before decreasing to a minimum at grain maturity. Moreover, the curves for dry weight increase and gibberellin like substances follow a remarkably similar course, with the latter reaching its maximim slightly earlier than the former one. This result indicates that gibberellines may participate in the regulation of the accumulation process in the endosperm of barley grain.
Action de quelques phytohormones sur la respiration et ľabsorption du phosphate par des disques de tubercules de pomme de terre en survie
Authors: HOURMANT Par ANNICK , PENOT Et MICHEL
Published: April 2006

Action of some phytohormones on the respiration and on the absorption of phosphate by aging potato tuber discs.

Discs of potato tuber incubated in aerated medium show an increase of the rates of respiration and phosphate absorption with aging time; the rates increase by two and nine respectively during the time period between 5 and 24 h of aging. Adenine or some N‐6 substituted adenines [benzylaminopurine (BAP), furfurylaminopurine (FAP), methylaminopurine (MAP)], which present variable degrees of cytokinin activity, partially inhibit the increase of the rate of phosphate absorption and, to a lesser extent, the increase of the rate of respiration. Also abscisic acid (ABA), indole 3‐acetic acid (IAA), and gibberellic acid (GA3) produce inhibition of the increase of the rate of phosphate absorption with varied effects on the respiration. With regard to phosphate uptake, the effects of ABA, 1AA and GA3 were additive to those of BAP. The effects on respiration were different from the effects on phosphate uptake, so that there is no direct relationship between inhibition of respiration and inhibition of phosphate uptake.
The Influence of Photoperiod and Temperature on the Development of Frost Hardiness in Seedlings of Pinus silvestris and Picea abies
Authors: CHRISTERSSON LARS
Published: April 2006

The influence of short days and low temperature on the development of frost hardiness in seedlings of Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.], grown for 6 months in glasshouses and climate chambers, was investigated. The degree of hardiness was estimated by freezing the shoots of the seedlings to predetermined temperatures. After 8 weeks in a glasshouse the viability of the seedlings was determined by establishing bud flushing.

The most effective climate for the development of frost hardiness was short days (SD) and low temperature (2°C); the next most effective was SD and room temperature (20°C). However, long days (LD) and low temperature also had a marked effect on the development of hardiness. A combination of 3 weeks’treatment with SD and 20°C, and 3 weeks with SD and 2°C gave the same results as 6 weeks with SD and 2°C. The results clearly demonstrate the importance of the photoperiod prior to low temperature for the development of frost hardiness.

In conclusion both short days and low temperature induce frost hardiness development. Probably this occurs by initiation of different processes in the two cases. The degree of frost hardiness development appears to depend on the sum of these different processes and on the timing between them.
Ca2+‐ and Mg2+‐stimulated ATPases from Roots of Plantago major and Plantago maritima: Response to Alterations of the Level of Mineral Nutrition and Ecological Significance
Authors: KUIPER DAAN , KUIPER PIETER J. C.
Published: April 2006

Growth of Plantago major L., ssp. major L. and ssp. pleiosperma Pilger and P. maritime 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 the studied Plantago species was strongly stimulated by high‐salt conditions.

The Ca2+‐ and Mg2+‐stimulated ATPase activity of microsomal preparations of the roots was also studied. In P. major ssp. major and P. maritime a major pH optimum was observed at pH 6.5, and in addition a second pH optimum was found at pH 8.0. High‐salt plants of these two species were characterized by biphasic stimulation curves for Ca2+ and Mg2+, whereas P. major ssp. pleiosperma showed a monophasic pattern. The ATPase activity per g dry weight of P. major and P. maritima was highest in high‐salt plants. The species investigated here are adapted to relatively nutrient‐rich conditions, and the properties of ATPases (Km, Kmax, protein content) and the growth responses are discussed in relation to this ecological property.
Enzymes Related to Serine Synthesis in Spinach Chloroplasts
Authors: LARSSON CHRISTER , ALBERTSSON ELISABETH
Published: April 2006

The three enzymes D‐3‐phosphogIycerate dehydrogenase (E.C. 1.1.l.s), eqglutamate dependent O‐phospho‐L‐serine aminotransferase (E.C. 2.6.1.52), and O‐phospho‐L‐serine phosphatase (E.C. 3.1.3.3.), which together catalyse the turnover of D‐3‐phos‐phoglycerate (3‐PGA) to serine were assayed in chloroplast and leaf extracts from spinach (Spinacia oleracea). Relatively high activities of the dehydrogenase and the phosphatase were found in both chloroplast and leaf extracts, whereas the specific activity of the aminotransferase was 10 times higher in leaf extracts than in chloroplast extracts. The results suggest that spinach chloroplasts are able to produce minor amounts of serine directly from 3‐PGA, but that the main part of the phosphohydroxypyruvate formed is exported, and probably used in a parallel pathway to serine outside the chloroplasts. Some kinetic properties of the enzymes were also determined.
Uptake and Distribution of Nitrogen in Young Apple Trees after Application of Nitrate or Ammonium, with Special Reference to Asparagine and Arginine
Authors: TROMP J. , OVAA J. C.
Published: April 2006

Apple rootstocks M.7 were given either nitrate or ammonium at the end of September. Until the following June, total and protein nitrogen and the composition of the soluble nitrogen fraction were followed in the roots, stem‐bark, and new growth. Nitrogen from both sources was readily absorbed in roughly the same amounts. Absorption occurred in the autumn and especially in the following spring. Incorporation of the absorbed nitrogen took place exclusively in the young roots. Arginine and, to a lower degree, asparagine were by far the most abundant of the soluble amino compounds and reached levels far above those in the unfertilized trees. The asparagine/arginine ratio was rather high during the first few weeks after fertilization but then dropped steadily to a low winter level. During May and June there was a gradual decrease to very low levels, especially in the new growth. The data suggest that the absorbed nitrogen is incorporated into asparagine and that arginine is formed from asparagine if the supply of nitrogen exceeds the immediate needs.

Throughout the experimental period, ammonium fertilization led to higher values of the asparagine/arginine ratio than did nitrate nutrition. This is explained in terms of an enhanced production of asparagine and a retarded conversion into arginine. It is argued that asparagine is the main translocation compound for nitrogen. The possibility is discussed that, in addition, arginine moves upwards by a process of exchange along the negatively charged walls of the xylem vessels.
The Effect of Coumarin on Young's Modulus in Sunflower Stems and Maize Roots and on Water Permeability in Potato Parenchyma
Authors: UHRSTRÖM INGER , SVENSSON SVEN‐BÖRJE
Published: April 2006

By means of the resonance frequency method Young's, modulus has been determined after coumarin treatment of growing segments of etiolated sunflower hypocotyl segments and in maize roots. Coumarin caused a decrease in Young's modulus in both shoot and root tissue. The response was very rapid; in sunflower hypocotyls the decrease in elastic modulus appeared 3 min after application of coumarin. The effects produced by coumarin were similar to those found by auxin. Coumarin increased the rate of water efflux out of potato parenchyma by about 20%. The increase in water permeability was evident within 3 min.
Effects of Ultraviolet‐B Radiation Stress on the Abscisic Acid Status of Rumex patientia Leaves
Authors: LINDOO SUSAN J. , SEELEY SCHUYLER D. , CALDWELL MARTYN M.
Published: April 2006

To determine if increased abscisic acid (ABA) levels are associated with ultraviolet‐B (UV‐B) radiation (288–320 nm) stress, Rumex patientia L. plants were exposed to visible light with high or low (control) UV‐B irradiance and then assayed for ABA by gas chromatography. Though leaf growth was inhibited by the UV‐B irradiation, no differences in levels of free ABA were found between leaves from the two treatments after 1, 3 or 5 days of exposure. Unlike the situation in most environmental stresses, increased ABA levels are not associated with UV‐B radiation stress. Further, photolysis or isomerization are not likely explanations for the absence of ABA increase. Calculations indicate that if ABA in the leaf were fully exposed to solar UV‐B radiation only about 6.7% would be photolyzed by existing daily radiation at 40°N latitude, and 11.3% by radiation resulting from a 40% decrease in atmospheric ozone. The quantum yield for isomerization of cistrans‐ABA by radiation in the 288–312 nm waveband was determined. Existing daily solar UV‐B irradiation is capable of isomerizing ABA in solution to an equilibrium mixture of 50% cisjrans and 50%irans, trans‐ABA., However, because of radiation attenuation in the leaf, it is estimated that only a small fraction of the cistrans‐A.BA. would be isomerized.
Influence of Cytokinins and Temperature on Development of Asparagus plumosus Shoot Tips in vitro
Authors: FONNESBECH ANNE , FONNESBECH MOGENS , BREDMOSE NIELS
Published: April 2006

Lateral shoot tips from young shoots of Asparagus setaceus (Kunth) Jessop (syn. A. plumosus Baker) were grown on a modified Murashige and Skoog medium. PBA was the most effective cytokinin for growth and development of Asparagus plumosus shoot tips. The optimal range of PBA was between 0.02 and 2 mg/1. Zeatin was less effective, and kinetin, BA and 2iP were poor as cytokinins for A. plumosus. The optimal temperature for growth and development was 21°C. There was interaction between the temperature and the PBA concentration. With increasing temperature from 17 to 24°C the need for PBA increased from 0.2 to 2 mg/1.
Germination and Dormancy of Reed Canary‐Grass Seeds (Phalaris arundinacea)
Authors: LANDGRAFF ASBJÖRN , JUNTTILA OLAVI
Published: April 2006

Effects of various chemical and physical factors on the germination of several seed lots of reed canary‐grass (Phalaris arundinacea L.) have been studied. Germination at the optimum constant temperatures of 24 to 27°C was significantly stimulated by the following treatments: moist chilling in light, red light given during the first 3 days of imbibition, three 2‐h periods at 12°C given during the second day of imbibition, ethylene, increased oxygen tension and soaking in aerated water for 4 days. Dry storage at 20–30°C had no effect on the germination ability of the seeds. No significant quantities of germination inhibitors were found either in water or methanol extracts of seed dispersal units.

By comparing three cultivars with various degrees of seed dormancy, respiration measurements showed that there was a significant positive correlation between oxygen uptake prior to visible germination and germination capacity. Similarly, germination‐stimulating treatment significantly enhanced oxygen uptake prior to visible germination.
Promotion of Flowering on Mature Picea sitchensis by Gibberellin and Environmental Treatments. The Influence of Timing and Hormonal Concentration
Authors: TOMPSETT P. B. , FLETCHER A. M.
Published: April 2006

Male and female flowering were significantly promoted by gibberellin A4/7+ A3 mixtures applied beneath bark flaps on branches of 11‐year‐grafted mature scions of Picea sitchensis (Bong.) Carr. growing in the open in Scotland; 4 mg/ml gave more flowering than higher or lower concentrations of gibberellins and application in June was more effective than in July.

Gibberellins also increased male flowering on mature scions when applied directly to the buds in a polythene house. A gibberellin A4/7+ A3 mixture produced greater numbers of strobili when applied to 2‐year‐grafted plants in May and June than when applied in July and August. Flowering of 5‐year‐grafted plants increased with increasing concentrations of a gibberellin A4/7+ A9 mixture up to 19.7 mg/ml above which flowering decreased.

Modifying the environment by keeping in a polythene house enhanced the combined male and female flowering of 5‐year‐grafted mature scions above the amount on control plants outside, the effect being more marked in June and July than in August and September. Larger numbers of gibberellin applications or longer total lengths of time in the polythene house gave significantly greater amounts of combined male and female strobili.
Nitrogen Stress in Birch Seedlings
Authors: INGESTAD TORSTEN
Published: April 2006

In 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

Current 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

A 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

The 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

Changes 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

Large, 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

The 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

Growth 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

The 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

Extracts 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

Respiration 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

Removal 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

Seedlings 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

Oscillatory 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

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

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.
The Effect of Monochromatic Light on α‐Linolenic and Trans‐3‐Hexadecenoic Acids Biosynthesis, and Its Correlation to the Development of the Plastid Lamellar System
Authors: TRÉMOLIÉRES A. , GUILLOT‐SALOMON T. , DUBACQ J.‐P. , JACQUES R. , MAZLIAK P. , SIGNOL M.
Published: April 2006

Seven day old etiolated Zea mays L. (cv. Wisconsin 355) seedlings were illuminated for 20 h under monochromatic radiations (100 Á pass band) produced by a spectral illuminator of high energy. Four regions of the visible spectrum were observed to stimulate chlorophyll synthesis. With poorly developed leaves (grown for 7 days at 22°C: experiment A). the most efficient wavelengths were found to be in the blue and green (between 445 and 505 nm). yellow (between 580 and 605 nm) and red (maximum 650 nm) parts of the spectrum. With well developed leaves (grown for 7 clays al 27°C: experiment B), a slight displacement of the maxima towards shorter wavelengths was observed.

14C‐acetate was furnished to illuminated maize seedlings to follow lipid synthesis during greening. In the leaves of experiment A, the biosynthesis of α‐linolenic acid and monogalactosyldiacylglycerol followed chlorophyll accumulation. In the more developed leaves of experiment B. containing higher amounts of galactolipids, the biosynthesis of α‐linolenic acid and monogalactosyldiacylglycerol followed chlorophyll accumulation only in blue and yellow light. The biosynthesis of trans‐3‐hexadecenoic acid was strictly dependent on the wavelength of the irradiating light in the leaves of experiment A; it was optimal under blue (420 nm) and still very high under yellow (580 nm) and red (650 nm). In the more developed leaves of experiment B, it was optima in blue (445 nm) and in yellow (580 nm), and the red maximum was shifted to 630 nm. All C‐trans‐3‐hexadecenoic acid was incorporated into phosphatidylglycerol.

A marked relationship was observed between the intensity of galactolipid synthesis and the development of the lamellar system of maize plastids during greening. A positive correlation could be established between the biosynthesis of trans‐3‐hcxadeccnoie acid and the development of well constituted grana stacks in the plastids.
Chemical Forms of Nickel and Cobalt in Phloem of Ricinus communis
Authors: WIERSMA DOUWE , VAN GOOR BEREND J.
Published: April 2006

Investigations were performed to study the chemical form in which nickel and cobalt are transported in sieve tubes. Ricinus communis plants were used since they allow easy collection of relatively pure phloem sap. In the experiments labelled nickel or cobalt were given to the nutrient solution. The tapped phloem exudate was separated by gel filtration on Sephadex or by paper electrophoresis. Nickel and cobalt were bound to complexing organic compounds with a molecular weight in the range of 1000—5000. The overall charge of the nickel complex was negative, and the bulk of cobalt also appeared to complex to a compound with negative overall charge.
The Accumulation and Transport of Calcium in Barley Roots
Authors: SINGH CHANCHAL , JACOBSON LOUIS
Published: April 2006

The accumulation and transport of Ca by various zones of 6‐day old barley roots (Hordeum vulgare L.) were examined with special reference to their relationship to the salt status of the root. The initial salt content had a profound effect on Ca transport and a lesser effect on Ca accumulation. High‐salt roots transported Ca in much larger amounts than did low salt roots. In low salt roots the apical zone was more active in transporting Ca to the conducting tissue than were the mid or basal zones However, in high salt roots all zones were about equally active in transporting Ca. The metabolic inhibitor, DNP, had little effect on accumulation but inhibited transport very effectively. The effect of DNP was more pronounced on transport from the apical zone than from the other root zones. Calcium applied anywhere along the root length moved only basally and its polarized longitudinal movement was maintained irrespective of the salt status of the root. The movement of Ca was characterized by a rapid release of preabsorbed Ca and a ready exchange of apoplastic Ca. The hypothesis is presented that cellular Ca is in a relatively mobile state. Its entry into the symplasm is the rate limiting step in longitudinal transport and its overall movement is metabolically controlled.
Hormonally Induced Polyembryos in Wheat
Authors: FERGUSON J. D. , McEWAN J. M. , CARD K. A.
Published: April 2006

It had been shown previously that wheat plants, which had been sprayed with auxin herbicide al flowering lime, produced seeds with extra shoots. These shoots have now been found lo belong So new, and relatively normal, embryos formed in the lower part of the scutellum.
Relationship between Position on the Parent Plant and Dormancy Characteristics of Seeds of Three Cultivars of Celery (Apium graveolens)
Authors: THOMAS T. H. , BIDDINGTON N. L. , O'TOOLE DIANE F.
Published: April 2006

Germination and seedling emergence studies were made on seeds harvested from four different umbel positions of three cultivars of celery (Apium graveolens L.). Although heavier seeds were produced from primary umbels than from other umbels, these were less viable as measured by the germination percentage at I8°C in the light. However, germination of viable seeds from quaternary umbels was lower than that of seeds from primary umbels at 18°C in the dark when incubated with GA4, (2 × 10 −4M) and seed from secondary and tertiary umbels tended to be intermediate in response. All viable seeds germinated when N6‐benzyladenine (10−2M) was used in combination with GA4. Seeds from quaternary umbels of two of the cultivars had a lower high‐temperature limit for germination in the dark than did seeds from other umbels. In glasshouse experiments the emergence of viable ‘quaternary’ seeds of these cultivars was higher than that of ‘primary’ seeds. Under these conditions the time to 50% of the final emergence as determined after 42 days was similar for seeds from all umbel positions within each cultivar. In two varieties seedling weights were greater from seeds of primary as compared to quaternary umbels, and in general, the largest seedlings arose from the heaviest seeds and the smallest from the lightest seeds in all three cultivars.
Putrescine and Spermidine in Peas: Effeets on Nitrogen Source and Potassium Supply
Authors: KLEIN H. , PRIEBE A. , JÄGER H.‐J.
Published: April 2006

Free and total putrescine and, to a lesser extent, spemidine accumulate in both roots and shoots of peas in response to potas stum deficiency and ammomnium supply. Free putrescine responds more sensitively than total putreseine to variatioin of nutrients. Accumulation of putrescine is more pronounced in the roots than in the shoots.
Metabolic Study of Douglas‐fir Pollen Germination in vitro
Authors: MUREN ROGER C. , CHING T. M. , CHING KIM K.
Published: April 2006

Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] pollen was germinated and grown in mass in a sterile mineral medium supplemented with 0.3 M mannitol as osmotic stabilizer. During the 4‐day period, pollen elongated threefold; free sugar and amino acid contents did not change significantly; soluble protein, insoluble protein, and RNA decreased; starch reduced to 30%; and DNA doubled in quantity. Respiration rate remained high and constant during the first 36 h and then increased, but the respiratory quotient averaged about 1.0 throughout the period. The pool size of adenine nucleotides remained constant, whereas ATP content and energy charge increased rapidly during the first 8 h and remained high for the remainder of the period. 14C‐glucose was rapidly metabolized within 2 h at 25°C to amino acids (33%), organic acids (22%), sugars (20%), CO2 (15%), lipids (5%), and insoluble components (3%). Experimental data indicated that the cultural conditions provided a suitable environment for rapid germination and active metabolism of Douglas‐fir pollen.
Effects of Glyphosate on Metabolism of Phenolic Compounds
Authors: DUKE STEPHEN O. , HOAGLAND ROBERT E. , ELMORE C. DENNIS
Published: April 2006

Light enhanced the inhibiting effect of root‐fed glyphosate (5 × 10−4M) on dry weight accumulation of soybean [Glycine max. (L.) Merr.] seedling axes. Inhibition of growth by light was greatest in hypocotyls, whereas by glyphosate it was greatest in roots. A synergistic effect of light and glyphosate on stimulation of phenylalanine ammonia‐Iyase (PAL, E.C. 4.3.1.5) activity was also demonstrated. In continuous white light PAL activity increased linearly for 4 days in axes of seedlings exposed to glyphosate. Evidence of phytochrome involvement in the light effect was shown. The stimulatory effect of glyphosate on PAL activity was greater in roots than in hypocotyls. Soluble hydroxyphenolic compound levels were reduced by glyphosate but were increased by light on a per axis basis. On a fresh weight basis, hydroxyphenolics were more concentrated in glyphosate‐treated than in control tissues in the light. When compared to other amino acids, disproportionate decreases in free pools of phenylalanine and tyrosine occurred in axes of seedlings treated with glyphosate and light. The effect of light on all measured parameters was mainly in the hypocotyl, while that of glyphosate was primarily in the root. In the light, glyphosate caused increases in levels of glutamine and other amino acids that may be the result of amination reactions, protecting from excess ammonia generated by enhanced PAL activity. These results suggest that PAL has a strong influence on its substrate levels in this system and/or that glyphosate inhibits synthesis of aromatic amino acids.
Nitrate and Nitrite Reduction in Wheat Leaves as Affected by Different Types of Water Stress
Authors: HEUER BRURIA , PLAUT Z. , FEDERMAN EVELYN
Published: April 2006

The effect of different types of water stress on nitrate and nitrite reductases of wheat (Triticum vulgare L. cv. Mivhor) leaves was investigated. Water stress was applied either to leaf tissue by its incubation in mannitol or various salt solutions, or to intact plants by exposure of the root system to low temperatures or to salinity. Nitrite reductase was much less sensitive to water stress than nitrate reductase, and was not sensitive to salinity up to osmotic potentials of about — 13 bars.

The decrease in nitrite reductase activity by water stress was attributed to a direct inhibition of the enzyme rather than to a repression of enzyme synthesis. This was based on the fast response of the enzyme after exposure of leaf tissue to reduced osmotic potential, on the lack of a continuous decrease in enzyme activity during a prolonged stress, and on the fact that light activation of reductase was unaffected by water stress.

The inhibition of nitrate reductase under water stress was attributed to both a direct inhibition and a reduced rate in enzyme synthesis. This is concluded from the fact that a decrease in its activity was obtained already within 1 h after stress application and from the fact that light induction of the enzyme was inhibited by stress.
Properties of Plasmamembrane ATPase and Mitochondrial ATPase of Saccharomyces cerevisiae
Authors: PETERS P. H. J. , BORST‐PAUWELS G. W. F. H.
Published: April 2006

The properties of mitochondrial ATPase and plasmamembrane ATPase of Saccharomyces cerevisiae are compared. The pH dependence differs considerably. At low pH plasmamembrane ATPase is inactivated. High salt concentrations protect the ATPase against acid inactivation. K+ is more effective than Na+. The sensitivity of mitochondrial ATPase towards azide, Dio 9 and oligomycin is far greater than found with plasmamembrane ATPase. There are no indications that the membrane ATPase is involved directly either in monovalent cation uptake or in divalent cation uptake. Sr2+ and Ca2+ do not activate plasmamembrane ATPase and inhibit Mg2+‐activated ATPase. The substrate specificity of plasmamembrane ATPase is much greater than the substrate specificity of mitochondrial ATPase.