bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Uptake Efficiency of Sunflower Roots
Authors: PETTERSSON SUNE
Published: April 2006

The term ion uptake efficiency is used for the rate of uptake of a particular ion from nutrient solutions holding a standard concentration of that ion (0.5 mM sulphate, 1.5 mM phosphate or 2.0 mM rubidium). The uptake efficiency for rubidium and phosphate in roots of intact sunflower plants depended on the salt status of the plants and on the concentration of the ion under investigation in pretreatment solutions. The effect of pretreatment was a rapid process causing differences of more than 300% in ion uptake efficiency within 1 h, depending on the composition of the pretreatment solution. At concentrations above 0.1 mM the rate of uptake of rubidium in the root was higher than the net potassium uptake necessary for adequate growth. The rate of sulphate uptake was related to potassium uptake but not to phosphate uptake. It is suggested that ion uptake of the roots is regulated by internal factors as well as by direct interactions between the medium and the absorbing surfaces.
Natural Chlorinated Auxins Labelled with Radioactive Chloride in Immature Seeds
Authors: ENGVILD K. C.
Published: April 2006

Immature seeds were harvested from 15 species grown in perlite/vermiculite containing 36Cl‐, but with very low levels of cold Cl‐. Autoradiograms of one‐ and two‐dimensional thin layer chromatograms of butanol extracts of lyophilized seeds indicated several radioactive compounds besides the 36Cl‐ in many species. In pea the radioactivity cochromatographed with 4‐(or 6‐)chloroindolyl‐3‐acetic acid and its methyl ester; in other species radioactivity was found near these chlorinated indolyl‐acetic acid markers.
Salt‐stimulated Phosphoenolpyruvate Carboxylase in Cakile maritima
Authors: BEER S. , SHOMER‐ILAN ADIVA , WAISEL Y.
Published: April 2006

The effects of NaCl and other salts, in vivo and in vitro, on the activity of phosphoenolpyruvate carboxylase from the coastal C3 halophyte Cakile maritima Scop, were investigated.

Plants grown with 100 mM NaCl in their growth medium yielded some 30% higher rates of phosphoenolpyruvate carboxylase activity than did salt‐depleted plants.

Activity of the enzyme was stimulated when NaCl was added to the reaction mixture in concentrations of up to 200 mM. The magnitude of this in vitro stimulation was similar for plants grown in the presence or absence of NaCl. The effect seems to be caused by chloride rather than by sodium ions.
Relative Contribution of Ribulose 1,5‐Diphosphate Carboxylase and Phosphoenolpyruvate Carboxylase to CO2 Fixation Activity in Roots of Dark‐grown or Light‐grown Lens culinaris Seedlings
Authors: NATO A. , DELEENS E.
Published: April 2006

The pathway of carbon assimilation in greening roots was compared to the pathway in leaves of Lens culinaris seedlings by means of labelling distribution analysis among the products of 14CO2 fixation in vivo, and in vitro with ribulose 1,5‐diphosphate as the substrate. In green leaves, CO2 fixation via ribulose 1,5‐diphosphate carboxylase predominated largely while, in green roots, this carboxylase activity and the phosphoenolpyruvate carboxylase contributed almost equally to the whole in vivo CO2 fixation. A participation of the activities of both carboxylases according to the double carboxylation pathway in the synthesis of dicarboxylic acids (malate and aspartate) was demonstrated in vitro after 48 h of greening in roots but seemed to be absent in in vivo experiments.
Uptake of Zinc and Strontium by Brown Algae
Authors: SKIPNES OLAV , ROALD TONE , HAUG ARNE
Published: April 2006

The accumulation of radioactively labelled strontium and zinc by living and killed tips of the brown alga Ascophyllum nodosum (L.) Le Jol. was studied and compared with the uptake in some model substances.

The accumulation of strontium was reversible, and similar in living and killed plants. Equilibrium was established within a couple of days. Strontium accumulation seemed to be an ionexchange process involving the negatively charged intercellular polysaccharides, probably mainly alginate.

Only a small fraction of the zinc uptake in living algae seemed to be due to a similar ion exchange with the intercellular polysaccharides. The characteristic features of the zinc uptake was a constant, slow, irreversible accumulation persisting for very long periods of time. In dead algae the uptake was rapid and reversible, indicating that the algae contained zinc‐binding substances which were not directly accessible to the zinc ions in the surrounding seawater before killing.

It is proposed that these substances in the living plant are contained in membrane‐surrounded structures, probably vacuoles. These membranes, effectively regulating the zinc uptake in the living cells, are destroyed by killing, making the zinc binding substances directly accessible.

The transfer of zinc from the reversible intercellular sites to the irreversible cellular sites continued undisturbed during low‐tide periods. The intercellular charged polysaccharides thus function as ion buffers, allowing ion uptake into the cell at a constant rate, independent of the tidal movements.
Inhibition of Corn and Sunflower Photosynthesis by Lead
Authors: BAZZAZ F. A. , CARLSON ROGER W. , ROLFE G. L.
Published: April 2006

Detached corn and sunflower leaves supplied with PbCl2 via the transpiration stream exhibited reduced rates of photosynthesis. The difference between species in the amount of Pb taken up was in direct proportion to their respective transpiration rates. For both species the reduction in photosynthesis and the amount of Pb taken up increased with increasing treatment concentrations. A corresponding reduction occurred in the rate of transpiration suggesting that stomatal resistance may be increased by Pb contamination. The pathways of CO2 and water vapor exchange are discussed in relation to the effects of Pb on photosynthesis and transpiration.
Light‐stimulated Absorption of Nitrate by Wolffia arrhiza
Authors: SWADER J. A. , STOCKING C. R. , LIN CHIN HO
Published: April 2006

The mechanism of the light‐stimulated absorption of nitrate by Wolffia arrhiza was studied. The nitrate‐absorption mechanism in ammonium‐grown plants is stimulated by the presence of nitrate. In a manner similar to the absorption of many other ions, the absorption of nitrate follows a typical biphasic pattern in relation to external nitrate concentration. Mechanism 1 is effective at nitrate concentrations up to 0.5 to 0.75 mM and mechanism 2 becomes operative at higher nitrate levels.

Light stimulates the absorption of nitrate independently of the effect of light on the reduction of nitrate. The effects of uncouplers, inhibitors, and light of wavelengths of 700 nm or longer indicate that nitrate absorption by Wolffia cells is reduced when non‐cyclic electron transport is blocked. It is postulated that under this condition, ATP in the chloroplast (produced by cyclic photophosphorylation) may be less readily transported across the chloroplast envelope than when non‐cyclic electron transport is proceeding.
Germination of Seeds in the Shadow of Plants
Authors: GÓRSKI TADEUSZ
Published: April 2006

An attempt to prove the ecological significance of red‐far red control mechanisms in seed germination was made. The seeds of 30 species were exposed beneath the plant canopies. All the normally light‐stimulated seeds, and also seeds of 14 (out of 19) “insensitive’ species and seeds of 1 (out of 4) light‐inhibited species, were inhibited or significantly retarded in their germination, as compared with seeds exposed to diffuse light in an artificial construction.

Further experiments with “insensitive’ seeds of Lactuca sativa L. cv. Cud Vorburgu showed that after prolonged plant‐shadow treatment the seeds became light‐sensitive in the usual phytochrome‐mediated manner. Seeds exposed under the plant canopies during a few days were extremely sensitive to red or white light, but this sensitivity diminished slowly in the course of treatment.

The spectral composition of light filtered through the leaves shows great preponderance of far red radiation. The red‐far red reversion can be simply obtained with the natural light and a leaf. In open stands bright weather retards considerably the germination of lettuce, cloudy weather brings about full germination.

Some considerations on the ecological significance of seed behaviour, particularly as connected with plant competition, are given.
Changes in Sapwood of Roots of Norway Spruce, Attacked by Fomes annosus
Authors: POPOFF THOMAS , THEANDER OLOF , JOHANSSON MARTIN
Published: April 2006

Acetone extracts of sapwood and reaction zone of spruce roots attacked by Fomes annosus, collected in February, June and October, were separated into resinous and phenolic fractions. The fractions were further separated by column, thin layer and gas liquid chromatography, followed by biological tests, using Fomes annosus and other rot fungi. The reaction zone contained quantitatively less light petroleum soluble compounds than the sapwood but more acids. The phenolic content was about ten times higher in the reaction zone than in the sapwood. Nine lignans and one simple phenol (4‐methylcatechol) were identified and quantitatively estimated in the reaction zone. The resinous fraction of the extract from the reaction zone as well as some of the lignans and 4‐methylcatechol inhibited fungal growth, in some cases followed by detoxification and continued growth. The predominant lignan, hydroxymatairesinol, had no effect on Fomes annosus or five other wood degrading fungi. About 15 unidentified phenols were observed, some of them probably of importance as inhibitors, either alone or in combination with other phenols.
Control of Bean Bud ATP Levels by Regulatory Molecules and Phytochrome
Authors: KIRSHNER RONALD L. , WHITE JUDITH M. , PIKE CARL S.
Published: April 2006

This study assessed the involvement of exogenously supplied acetylcholine, dibutyryl cyclic AMP, and various inhibitors of acetylcholine and cyclic AMP metabolism on the rapid phytochrome‐mediated alteration in the ATP content of etiolated bean buds (Phaseolus vulgaris L. cv. Red Kidney). ATP was extracted in boiling water and measured by the firefly luciferin‐luciferase assay. The depression of ATP content by low levels of either acetylcholine or dibutyryl cyclic AMP was independent of irradiation. Atropine, AMO‐1618, and theophylline all altered ATP content, and the effects differed in red light and in darkness. In contrast to other reports, no straightforward model of phytochrome action through either acetylcholine or cyclic AMP could be constructed. Also, the time course of ATP content during the standard 5 min red‐irradiation period was determined, and effects of light are observed within 1 min.
In vitroPost‐germination Growth and Development of Embryos ofAlectra(Scrophulariaceae)
Authors: OKONKWO S. N. C.
Published: April 2006

In vivo, seeds of the obligate root parasiteAlectra vogeliiBenth. (Scrophulariaceae) germinate only after being soaked in water for a period of time (pretreatment) followed by stimulation by certain factors exuded from a host root. Germinated seedlings do not develop beyond radicle emergence, and finally die, unless their radicles make contact with and penetrate into a host root conductive system.In vitro, germinated embryos obtained by exposing sterilized and pretreated seeds to root exudate ofVigna unguiculatawere aseptically cultured on Knop's, White's and Murashige and Skoog's media. The embryos grew into seedlings with shoots and roots on a medium containing mineral salts and sucrose, but not on mineral salts alone. Seedling performance was generally not improved when the mineral salts‐sucrose media were supplemented with vitamins. Shoot extension growth was better on Murashige and Skoog's mineral salts‐sucrose medium than on Knop's or White's medium. However, seedling development was greatly boosted when cultivated on White's minerals salts‐sucrose medium supplemented with coconut milk. Seedlings turned green on transfer to light but did not flower. The successful culture of these embryos and seedlings on a simple, chemically defined medium of mineral salts and sugar suggests that these nutrient components are the minimal external requirements for stimulation and support of normal seedling growth. These may be obtainedin vivoby the parasite's tapping of the host root conductive system.
The Effect of Dichlorophenyldimethylurea on Light‐Stimulated 22Na+, 42K+ and 86Rb+ Absorption in Different Tissues of Phaseolus vulgaris Leaves
Authors: JACOBY BENJAMIN
Published: April 2006

The light‐stimulated absorption of 86Rb+ by Phaseolus vulgaris L. leaf slices was found to be sensitive to dichlorophenyldimethylurea in air as well as in nitrogen, whereas light‐stimulated 22Na+ absorption in nitrogen was not sensitive to this inhibitor. The absorption of 22Na+ is not affected by light in air. The absorption of 42K+ is enhanced by a dichlorophenyldimethylurea‐insensitive light effect under anaerobic conditions and further increased by light in the absence of the inhibitor. Light‐enhanced 42K+ absorption in air was also inhibited by dichlorophenyldimethylurea. Previous work showed that light‐stimulated 86Rb+ and 42K+ absorption by Phaseolus vulgaris leaf slices is restricted to the guard cells. The present results are discussed with reference to the effect of light on stomatal opening.
Quantacorrected Spectrometer for Recording Different Types of Photobiological, Photochemical, and Spectrophotometric Measurements
Authors: HALLDAL PER , NORDSTRÖM BERTIL , ÖQUIST GUNNAR
Published: April 2006

An instrument is described which functions as a spectrophotometer, In addition it measures action spectra of photobiological processes, excitation and emission spectra of fluorescence, and gives data for calculation of action spectra of partial reactions of photosynthesis and photocontrolled enzymatic reactions. The instrument has a Bausch and Lomb 250 mm grating monochromator. Equal numbers of quanta at different wavelengths are adjusted electronically with control of the slit through a quantacorrected photocell and a servo motor which is programmed by a cam connected to the wavelength drive.
Abscisic Acid as Inhibitor of α‐Amylase from Aspergillus and Bacillus subtilis
Authors: HEMBERG TORSTEN
Published: April 2006

Abscisic acid (ABA) inhibited the activity of α‐amylase from both Aspergillus and Bacillus subtilis in vitro if ABA and enzyme solutions were allowed to react with each other before adding to the starch solution. If the ABA solution was put to starch before adding the enzyme, no inhibition occurred.

The inhibition increased with increasing time between mixing ABA and enzyme solutions and adding the mixture to starch. It was not the absolute amounts of enzyme and ABA which were of importance for the inhibition, but the concentrations of ABA and enzyme in the ABA + enzyme mixture. Within certain limits the inhibition was proportional to the concentration of ABA, so that it should be possible to use the inhibition in quantitative tests for inhibitors.

Dialysis of a mixture of ABA and enzyme showed that ABA is bound to the enzyme. The enzyme was still inhibited after dialysis for 25 h. On the other hand, partitioning with diethylether from acid water solution could free the enzyme from all ABA. Supposedly ABA acts as an allosteric inhibitor.

The results may offer the foundation for one possible way to explain why inhibitors in plants sometimes inhibit growth and sometimes do not. If inhibitor, enzyme and substrate are compartmentalized, the degree of reaction should depend upon the sequence in which the three components meet each other.
Radial Oxygen Loss from Roots: The Theoretical Basis for the Manipulation of Flux Data Obtained by the Cylindrical Platinum Electrode Technique
Authors: ARMSTRONG W. , WRIGHT E. J.
Published: April 2006

A résumé is given of the cylindrical platinum electrode technique for measuring the rate of oxygen release from the submerged roots of intact plants.

Methods are then described for manipulating the oxygen flux data to quantify the following root characteristics: total effective internal diffusional resistance, non‐metabolic (pore‐space) resistance, internal apical oxygen concentration, effective diffusion coefficient of internal transport and fractional porosity, and the respiratory contribution to internal transport. The diffusional resistance of the root wall is discussed and the method formerly suggested for converting low temperature flux data to the appropriate room temperature values (Armstrong 1971) is revised. Finally, suggestions are made for overcoming the difficulties encountered in using flux data for comparative work if the roots differ in their apical radii.
Evolution des Teneurs en Acides Chlorogénique et “Isochlorogénique’ au Cours du Traitement de Vernalisation des Racines de Cichorium intybus
Authors: PAULET F. MIALOUNDAMA et P.
Published: April 2006

In a cold‐requiring variety of endive (chicory, Cichorium intybus L. ev. Witloof) we could demonstrate a relationship between the variations in the content of chlorogenic acid during the cold treatment of the roots and their disposition to produce flowers in vitro. An increase in the level of chlorogenic acid in the roots preceded the development of their aptitude to form flower buds. In addition, the three main forms of “isochlorogenic’ acid are present in the roots of this cultivar: 3,5‐dicaffeoyl‐quinic acid, 3,4‐dicaffeoyl‐quinic acid, and traces of 4,5‐dicaffeoyl‐quinic acid. The variations in the levels of chlorogenic and “isochlorogenic’ acids indicate that part of the chlorogenic acid (3‐caffeoyl‐quinic acid) is converted to 3,5‐dicaffeoyl‐quinic acid.
Protein Metabolism in Cultured Plant Tissues
Authors: KEMP JOHN D. , SUTTON DENNIS W.
Published: April 2006

Rates of protein synthesis in normal callus tissues (either tight or loose morphological form), in crown gall callus tissues and in cultured pith cells were measured for both the lower surface cells (those in contact with the original growth medium) and upper surface cells (those never in contact with the growth medium until labeling). Cells of both surfaces of loose and crown gall callus and the upper‐surface cells of tight callus had similar rates of protein synthesis, 29–31 mg of protein synthesized × (g protein)−1× h−1. The lower surface cells of tight callus had a 35% lower rate of synthesis, 20 mg × g−1× h−1.

Pulse‐chase experiments suggested that rates of protein degradation for all tissues were the same, 21–23 mg protein × (g protein)−1× h−1. Thus, there probably was no accumulation of protein in the lower surface cells of tight callus tissue, but the other tissues had rates of accumulation equaling 10 mg × (g protein)−1× h−1. Autoradiography and electron‐microscopic examination of cells in tight callus labeled with 3H‐leucine show that: (a) the lower‐surface cells were more degenerate than cells within the callus or on the upper surface; and (b) the first few cell layers nearest the medium were preferentially labeled.

Pulse‐chase experiments were also used to quantitate the nonprecursor pool (defined as that tritium in the soluble amino acid pool that does not equilibrate with protein during a pulse‐chase experiment). The nonprecursor pool increased linearly with time at the same rate as incorporation of 3H‐leucine into protein. Furthermore, the nonprecursor pool copurified with leucine and was probably either D‐ or L‐leucine.
Protein Metabolism in Cultured Plant Tissues
Authors: KEMP JOHN D.
Published: April 2006

The N‐trifluoroacetyl‐L‐prolyl‐leucyl methyl ester (TFA‐L‐prolyl‐leucine) was synthesized to quantitate the amounts of D‐ and L‐leucine in the amino acid pool fraction of tobacco callus tissue. TFA‐L‐prolyl‐D‐leucine and TFA‐L‐prolyl‐L‐leucine could be separated on gas liquid chromatography, with the former eluting about 45 s before the latter. The chromatographed TFA‐L‐prolyl‐L‐leucine was collected from the gas liquid chromatograph and found to contain equal molar amounts of leucine and proline. The identity of the two gas liquid chromatography peaks was confirmed by gas liquid chromatography/mass spectrometry.

Although callus tissue incorporated both exogenously added D‐ and L‐leucine into its amino acid pool fraction, the rate of uptake of D‐leucine appeared to be substantially less than that of L‐leucine.

When callus tissue was labeled on 3H‐L‐leucine medium for 24 h and then transferred to nonradioactive medium for 24 h, about 50% of the tritium remaining in the leucine pool was not available for protein synthesis (nonprecursor pool fraction). However, all of the tritium was associated with L‐leucine, and the specific radioactivity of leucine in collected TFA‐L‐prolyl‐leucine was the same as that of leucine in the crude pool fraction. Thus, the nonprecursor pool is L‐leucine.
Vegetative Propagation of Pinus sylvestris
Authors: WHITEHILL S. J. , SCHWABE W. W.
Published: April 2006

Methods for the vegetative propagation of Pinus sylvestris L. from interfascicular shoots are described. Using 5‐year‐old plants the outgrowth of interfascicular shoots was promoted by removal of terminal and lateral buds; this response was augmented substantially by application of cytokinin, tri‐iodobenzoic acid, alar and morphactin alone and especially in combination.

The rooting capacity of shoot cuttings from interfascicular shoots appeared to be largely determined by the state of growth of the stock plant. Cuttings from dormant stock plants subjected to short‐day treatment followed by a period of low temperature gave the best rooting, especially when the cuttings themselves had been cold‐stored prior to planting. Rooting was optimal when such cuttings were treated with a mixture of 25 mg/l of indolebutyric acid and 25 mg/l of napthaleneacetic acid as a 48 h basal soak, and were planted on a heated mistbench under extended illumination; over 90% of such cuttings could be rooted. These results are discussed in relation to bud activity, endogenous hormone levels and promoting tissue extracts also tested.
Purification and Partial Carbohydrate Analysis of Phytochrome from Avena sativa
Authors: ROUX STANLEY J. , LISANSKY STEPHEN G. , STOKER BLANCHE M.
Published: April 2006

Highly purified samples of phytochrome from etiolated oat (Arena satira L.) seedlings were analyzed for sugar content. Phytochrome was found to be a glycoprotein, with about 4% of its weight as carbohydrate. In addition, modifications in the procedure for purifying phytochrome are proposed here and certain details about the protocol are discussed that improve the yield and reproducibility of previously published methods.
Two Steps of Gas Exchange in Leaf Photosynthesis
Authors: OGAWA TERUO
Published: April 2006

Photosynthesis and transpiration of excised leaves of Taraxacum officinale L. and a few other species of plants were measured, using an open gas analysis system. The rates of CO2 uptake and transpiration increased in two steps upon illumination of stomata‐bearing epidermis of these leaves at a light intensity of 50 mW × cm−2. Abscisic acid inhibited only the second step of gas exchange. Illumination of the astomatous epidermis of hypostomatous leaves caused only the first step of gas exchange. These data indicate that the first and second steps arise from cuticular and stomatal gas exchange, respectively. The rate of the cuticular photosynthesis in a Taraxacum leaf reached saturation at a light intensity of 5 mW × cm−2, and the rates of the stomatal photosynthesis and transpiration reached saturation at a higher intensity of 35 mW × cm−2. The cuticular photosynthesis of a Taraxacum leaf was 18% of the stomatal photosynthesis at 50 mW × cm−2 and 270% at 5 mW × cm−2. The other species of leaves showed the same trend. The importance of cuticular CO2 uptake in leaf photosynthesis, especially under low light intensity was stressed from these data.
Effect of Water Stress on Transpiration in Birch Seedlings
Authors: SMOLANDER HEIKKI , HARI PERTTI , LUUKKANEN OLAVI
Published: April 2006

Transpiration of birch seedlings in the field is largely controlled by the amount of available water in the soil. This is in contrast with the situation found in CO2 exchange, where distinct interaction between temperature and drought was observed in our previous studies. The present study indicates that no similar relationships exist as far as transpiration is concerned, and in agreement with our previous preliminary studies, separate control mechanisms thus seem to affect transpiration on the one hand and photosynthesis on the other under natural conditions.
Proteins of Mitochondrial Synthesis
Authors: GOSWAMI BISWENDU B. , DUBE SYAMALIMA , BHATTACHARYYA PRABIR , SINHA SANDIP N. , RAY BIMAL K. , DUBE D. K. , ROY S. C.
Published: April 2006

Proteins synthesized in vitro by mitochondria isolated from 48‐h germinating seeds of Vigna sinensis (L.) Savi and incubated in the presence of 14C‐labelled amino acids from Chlorella protein hydrolysate, have been found associated with nine products separable by acrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Cytoplasmic contribution to these products was practically eliminated by the use of cycloheximide. Most of the radioactivity was incorporated into proteins having molecular weights between 10,000 and 65,000 as determined by comparing their electrophoretic mobilities with those of standard, reference proteins.
Regulation of Transpiration in Avena. Responses to White Light Steps
Authors: BROGÅRDH T. , JOHNSSON A.
Published: April 2006

The transient responses in transpiration rate of the primary leaf of 8‐days‐old oat plants were studied when step changes in the white light irradiance were administered to the plants. A light or dark step was achieved by an instant increase or decrease, respectively, of the irradiance on the leaf surface. Usually the light step responses consisted of one rapid response (rise time 1–2 min) and one slow response (rise time 5–10 min). The dark step response had a fall time of about 10 min.

At a high irradiance level and in CO2‐free air the slow response disappeared. This could mean that the slow response is CO2‐controlled. The rapid response was still present under these conditions and is therefore probably caused by other processes than the slow response.

In long time experiments several cycles of a circadian rhythm (period 26–28 h) could be followed in the light step responses. Thus the rapid response was small at that time of the day when the slow response was most pronounced and vice versa. The endogenous nature of the rhythm was established in phase‐shift experiments. It is concluded that experiments on stomatal dynamics must take circadian variations into account.
Glutamic Acid Dehydrogenase Activity in Linseed as Influenced by Plant Age and Photoperiod
Authors: SAIRAM R. K. , SIROHI G. S. , SRIVASTAVA G. C.
Published: April 2006

Glutamic acid dehydrogenase (GDH) activity was measured in linseed Linum usitatissimum ev. SH‐1 at different growth intervals under normal and long photoperiodic conditions. In ungerminated seeds a low activity of GDH was recorded which increased rapidly during germination and thereafter decreased to a level when no GDH activity could be detected at 47 days of growth. An increase in its activity was recorded at 67, 87 and 107 days. Longer photoperiod (continuous light) increased the activity in roots markedly as compared to shorter photoperiods (normal days).
Properties of Extracellular Enzymes from Aphanomyces astaci and Their Relevance in the Penetration Process of Crayfish Cuticle
Authors: SÖDERHÁLL KENNETH , UNESTAM TORGNY
Published: April 2006

In culture filtrates from the crayfish plague parasite, Aphanomyces astaci, protease and a low level of hyaluronidase activity were found. The hyaluronidase activity was highest at pH 6.5 or above and at about 23°C. The protease activity had a broad pH‐optimum, between pH 7 and at least pH 10, and was partially denatured at 30°C. However, when incubated for 30 min with the substrate, casein, the activity increased logarithmically up to about 35–40°C and had an apparent optimum at 45–50°C.

The proteases from the parasitic as well as from two less proteolytic, saprophytic Aphanomyces species were predominantly constitutive and were excreted mainly by the older mycelia. Proteases from the parasite and a saprophyte did not reach full activity until 10–30 min after substrate addition.

No lipase activity was found in the case of the mycelium of the parasitic species. However, esterase was apparently present inside germinating zoospores.

The native enzymes of A. astaci could degrade freeze‐dried soft cuticle from crayfish. The relevance of the different enzymes of A. astaci for the penetration process within the cuticle of crayfish is discussed.
In vivo Chlorophyll Fluorescence Monitoring with Solid State Photosensors
Authors: MELCAREK PETER K. , BROWN GREGORY N.
Published: April 2006

Solid state photosensors with their many advantages have not been utilized for chlorophyll fluorescence research. One reason is their reputed low photosensitivity compared to photomultiplier tubes. A photodarlington sensor has a relatively low photosensitivity and a nonlinear current output versus light intensity. However, when incorporated into an apparatus described in this paper it can respond to fluorescence signals from leaves using light excitation as low as 500 μW/cm2. The sensitivity of another solid state device (photovoltaic photodiode) was compared to five photomultipliers using a monochromator‐microphotometer testing apparatus. This solid state sensor proved to have equal or greater sensitivity to chlorophyll fluorescence. An apparatus incorporating the photovoltaic photodiode is discussed.
Endogenous Shoot Growth Rhythms and Indeterminate Shoot Growth in Oak
Authors: BORCHERT ROLF
Published: April 2006

Wide variations of shoot growth patterns in saplings of pin oak (Quercus palustris Muenchh.) have been observed as a consequence of varying environmental conditions, experimental manipulations, and vigor of trees. Shoot growth patterns range from a series of recurrent, determinate flushes, constituting a genuine endogenous rhythm, to continuous, indeterminate growth. Observed growth patterns agree well with those predicted by a model of rhythmic growth which assumes the dependence of shoot growth on the functional equilibrium between shoot and root system. Indirect evidence suggests that cessation of shoot growth under favorable environmental conditions might be a consequence of internal water deficits. Observed differences in shoot growth patterns between young and mature trees are discussed as logical consequences of the model.
Tracheary Element Formation from Single Isolated Cells in Culture
Authors: TORREY JOHN G.
Published: April 2006

Friable callus tissue of Centaurea cyanus L. was grown on a solidified synthetic nutrient medium (EBM‐1) to produce a tissue with a low frequency of differentiated tracheary elements. Tissues were then suspended in liquid nutrient medium with agitation to produce a suspension which was filtered and the single‐cell suspension resulting was used as inoculum for either cell suspension cultures or for plating of cells into solidified medium in Petri plates. Media for the suspension cultures were selected to favor cytodifferentiation of tracheary elements. Differentiated tracheary elements formed as early as 10 days and numbers of tracheary elements increased with time roughly in relation to the increase in total cell number. From plating experiments it was shown conclusively that single isolated parenchyma cells differentiated directly into single isolated tracheary elements, although this event was rare. More usual was the division of isolated cells to form small colonies and then the differentiation of one, several or all of the cells into tracheary elements. Comparisons are made between results with cell plating experiments and cell suspension cultures. Optimism is expressed for finding a cell suspension culture system for studying cytodifferentiation.
Physiological Changes during Protoperithecial Differentiation in Neurospora tetrasperma
Authors: VISWANATH‐REDDY M. , TURIAN G.
Published: April 2006

Protoperithecial differentiation in Neurospora tetrasperma proceeds in four clearly discernible stages: ascogonial bud, ascogonial hook, ascogonial coil, and protoperithecium. This morphogenetic sequence was completely but transitorily blocked at 37°C. Under low oxygen tensions or in the absence of carbon dioxide, only ascogonial coils were differentiated. Glycolytic inhibitorssuchas2‐deoxy‐D‐glucose interfered with the ascogonial differentiation. Citric acid cycle inhibitors such as fluoroacetate selectively blocked the further development of ascogonial coils into protoperithecia. Differentiating cultures at 25°C responded positively to external sucrose with respiratory quotients above 1.0, whereas non‐differentiating cultures at 37°C, although respiring at high rates, never reached RQ 1.0. These results indicate that carbohydrate metabolism via fermentative glycolysis functions normally in ascogonia differentiating (25°C) cultures only.

Comparative chemical analysis showed delayed RNA synthesis, sharp disturbances in protein biosynthesis and metabolism, and lower levels of carbohydrate and bound lipids in young cultures at 37°C.

Polyols, especially ribitol and xylitol utilized as sole source of carbon, induced abundant protoperithecial morphogenesis at 37°C. This alleviating effect of polyols was negated by the addition of sugars at 37°C and shown to be a specific metabolic effect.
Bleach‐induced Germination and Breakage of Dormancy of Seeds ofAlectra vogelii
Authors: OKONKWO S. N. C. , NWOKE F. I. O.
Published: April 2006

The effects of solutions of sodium hypochlorite and calcium hypochlorite (bleach) on dormancy and germination ofAlectra vogeliiseeds were investigated. Dry (non‐pretreated) and 10‐day water‐pretreated seeds were exposed to various bleach concentrations, as well as to the host (Vigna unguiculata) root exudate.

The 15‐month‐old Alectra seeds used were partially dormant in that only 40% or less of the 10‐day pretreated seeds could be stimulated to germinate by the standard host root exudate. Comparable percentage germination of nonpretreated seeds was achieved with certain concentrations of bleach and the halogens, chlorine and bromine. Bleach and the halogens served not only as germination stimulant for pretreated Alectra seeds but appropriate concentrations induced also high percentage (70–90%) germination indicating a breakage of seed dormancy as well. The activity of the bleach in stimulating high percentage germination could be significantly reduced when the optimally bleach‐treated seeds were rinsed daily with water during the germination period. Vigna root exudate, but not bleach, was shown to act as root stimulant for Alectra seedlings. The possible mechanism of the bleach effect on germination and dormancy of Alectra seeds is discussed.
Indole‐3‐Acetic Acid (IAA) Oxidation by Leghemoglobin form Soybean
Authors: PUPPO ALAIN , RIGAUD JEAN
Published: April 2006

Leghemoglobin from nudules of soybean prepated by ammonium sulfate frationation appeared to be able to destroy substantial quantities of IAA, Degradation still occurred in purified leghemoglobin preparations isolated by G‐100 Sephadex chromatography. Nicotinic acid and acetate affecting the conformation of leghemoglobin both inhibited IAA oxidation by this hemoprotein. The ferric form was found to be the most active in this catabolism. This oxication, related to the psedudoperocidase activity of leghemoghlobin, is undoubtedly restricted in vivo by the very low level of the ferric form present in efficient nodules.
The Reducing Power and the CO2 Fixation Activity of Isolated Choroplasts
Authors: MIGINIAC‐MASLOW M. , HOARAU A.
Published: April 2006

Antimycin A, which stimulates the Co2 fixation activity of isolated intact spinach (Spinacia oleracea L) chloroplasts, was shown to stimulate also the oxygen evolution in the presence of oxaloacetate, as do the uncouplers. Some uncoupers (tetramethlethylenediamine, Nh4CL) were shown to stimulate the CO2 fixation activity, and to decrease the intrachloroplastic ATP levels, like antimycin A. The intrachloroplastic NADPH levels were not affected by the inhibitors studied.
Influence of Ethidium Bromide on the Gibberellin‐Induced Elongation of Cucumber Seedlings
Authors: SNIR IONA , KESSLER BEZALEL
Published: April 2006

Ethidium bromide, a DNA intercalating agent, acts synergistically with gibberellin on the elongation of cucumber seedling hypocotyls at concentrations of 0.05 and 1.0 μg per plant. At higher concentrations and when given prior to the GA treatment, ethidium bromide acts antagonistically with gibberellin.
Ribonucleic Acid Synthesis in Plant Mitochondria: Effects of Some Inhibitors and Cyclic Nucleotides
Authors: GOSWAMI BISWENDU B. , DUBE D. K. , ROY S. C.
Published: April 2006

Mitochondria isolated from 48‐h germinating Vigna sinensis (L.) Savi can incorporate [3H]uridine into acid‐insoluble material. The incorporation is highly sensitive to rifampicin and partially so to ethidium bromide, two specific inhibitors of template function. The inhibitory effect of rifampicin can be partly counteracted by cyclic 3′:5′‐AMP but not by cyclic 3′:5′‐GMP, if they are allowed to interact with the synthetic system before the treatment with rifampicin. This indicates that cyclic AMP and rifampicin compete for a common site on the RNA polymerase responsible for DNA‐dependent RNA synthesis. Inhibition by ethidium bromide is unaffected by prior nucleotide interaction with the system.
Differectial Induction of Zoospore Encystment and Germination in Aphanomyces astaci, Oomycetes
Authors: SENSSON EBBE , UNESTAM TORGNY
Published: April 2006

Genmination and encystment of zoosspores of Aphanomyces astaci, the very serious pathogen of European freshwater crayfish, Astacus astacus, were studied in ritro.

Encystment of motile zoospores was achieved using mild heating, stirring, or addition of alkali metal chlorides or mannitol. The physical treatments were inhibitory to the subsequent germination, while encytment could be achieved with potassium chloride, indicating that the two processes are differently induced and can be studied separately. The effect of temperature on these processes was also somewhat different.

Some ionic substances drastically influenced the final shape of the cyst. but without noticeably influencing the subsequent germination.

Germination was induced by a short exposure to the stimulatory substances. A synergistic effect between ionic and non‐ionic compounds was found. The receptivity of the zosspores to the triggering substances was low in newly formed spores but increased during the first 3 h of motility.

The initiation of germination is suggested to be parltly to be partly due to an osmotic effects on the zoospore. The relevance of the experimental results to in vivo conditions in discuessd.
Potassium and Photosynthesis in the Marine Diatom Phaeodactylum tricornutum as Related to Washes with Sodium Chloride
Authors: OVERNELL JULIAN
Published: April 2006

Three washes of Phaeodactylum tricornutum with potassium free sodium chloride solution reduced the potassium content of the cells to approximately 7% of the control value at pH 7.0. There was a concomitant reduction of the light induced evolution of oxygen to a value of approximately 20% of the control value. This reduction was less at pH 8.0. Addition of potassium to the washed cells gave rise, after 15 min, to a partial regain of the photosynthetic activity and of cellular potassium.

Activities of the two photosystems as assayed here were not dependent on the maintainance of a high potassium content in the cells. The level of ribulose‐1,5‐diphosphate carboxylase activity was the same whether the cells had been washed with potassium free or potassium containing saline.

Ruptured cells rapidly lost their ability to catalyse the photoreduction of dichlorophenolindophenol by water.
Reproducibly High Plating Efficiencies of Isolated Mesophyll Protoplasts from Shoot Cultures of Tobacco
Authors: BINDING H.
Published: April 2006

Sterile shoot cultures of Nicotiana tabacum L. cv. Sansum proved to be a highly appropriate source for the isolation of viable protoplasts. High yields of isolated protoplasts and high plating efficiencies are guaranteed by the absence of contaminaction, by controlled culture conditions and by the rhythmic rejuvenation of the shoots at each transfer to fresh agar medium.
Influence of S‐ethyl dipropylthiocarbamate (EPTC) on Wheat Root Phospholipid Fatty Acid Composition
Authors: KARUNEN P. , WILKINSON R. E.
Published: April 2006

Winter wheat (Triticum sativum L. ev. Nisu) was grown in sand which contained 0, 0.25, 0.5 and 1.0 mg S‐ethyl dipropylthicarbamate (EPTC) per kg air dry sand. In 21 day old roots, the phospholipids (PL) were extracted in ice‐cold chloroform/methanol (2:1, v/v) and isolated by thin layer chromatography (TLC). The PL fatty acids were analysed by gas liquid chromatography (GLC). The major fatty acids of the root PL fraction were palmitic, oletic, linoleic, and linolenic (22.4, 6.8, 39.2, and 23.1 μ/g root fresh weight, respectively). Total fatty acid content of the PL fraction was decreased to 39% by 1 mg EPTC/kg sand in which linolenic acid was decreased to 28%. The remainder of the major fatty acid constituents were decreased to 12–47%. The general quality of fatty acids in the PL fraction was slightly altered, while a 60% inhibition of total PL production resulted.
Stock‐Scion Interactions of Normal and Fruit Ripening Mutants rin and nor in Tomato
Authors: MIZRAHI Y. , DOSTAL H. C. , McGLASSION W. B. , CHERRY J. H.
Published: April 2006

Scions of the non‐ripening rin and nor tomato strains (Lycopersicum esculentum Mill.) were grafted on normal understock plants (cv. Rutgers) in an effort to study the influence of roots and vegetative tissue on the ripening behavior of the tomato fruit. Receiprocal grafts of ‘Rutgers’ scions on rin and nor understocks as well as grafted and ungrafted controls were also established. No alteration in the ethylene, and CO2 evolution and color development of either mutant fruits on normal understock or of normal fruits on mutant understock occurred. We suggest that the inability of rin and nor mutant fruits to ripen normally stems either from the presence in mutant fruit of a non‐translocatable ripening inhibitor, or from the absence of a non‐translocatable ripening factor.
Water Stress Induced Alterations of the Stomatal Response to Decreases in Leaf Water Potential
Authors: BROWN K. W. , JORDAN W. R. , THOMAS J. C.
Published: April 2006

Young growth‐chamber‐grown cotton plants were subjected to a series of eight periods of soil water stress, which served as a preconditioning treatment. After preconditioning, water was withheld and changes in the stomatal resistance and leaf water potential were determined and compared with similar well watered control plants.

The stomatal response of stress preconditioned plants adjusted such that the diffusion resistance of the lower surface of the leaf did not reach a value greater than 20 s cm−1 until the leaf water potential dropped 14 bars below that required to reach the same resistance on previously unstressed plants. The resistance—leaf water potential relation for the adaxial surface was unaltered by the preconditioning treatment. Adjustment of the osmotic potential of the guard cells on the abaxial surface provides at least a partial explanation of this change in response. The lack of adjustment of stomatal response on the adaxial surface of the leaves was correlated with a lack of adjustment in osmotic potential of guard cells on that surface.
A Brominating and Hydroxylating Peroxidase from the Red Alga Cystoclonium purpureum
Authors: PEDERSÉN MARIANNE
Published: April 2006

A particulate enzyme displaying peroxidase activity has been extracted from the red alga Cystoclonium purpureum (Huds.) Batt. The enzyme preparation was shown to contain ferri‐protoporphyrin IX through its formation of formic acid hemochromogen with absorption maxima at 399, 402, 555 and 600 nm. The preparation catalyses the formation of 3‐bromo‐p‐hydroxybenzyl alcohol from p‐hydroxybenzyl alcohol in the presence of H2O2 and NaBr at pH = 5.4. The formation of 3‐bromo‐p‐hydroxybenzyl alcohol was measured by gas chromato‐graphy‐mass spectrometry. At pH = 6.7, 4,5‐di‐hydroxybenzyl alcohol was formed. Addition of homogentisic acid stimulated the formation of dihydroxybenzyl alcohol and suppressed the brominating reaction. Iodide inhibits the enzyme. The results are consistent with a two‐site model of the enzyme.
Influence of Different Cytokinins on the Germination of Lettuce (Lactuca sativa) and Celery (Apium graveolens) Seeds
Authors: BIDDINGTON N. L. , THOMAS T. H.
Published: April 2006

The naturally occurring cytokinins, zeatin, zeatin riboside and dihydrozeatin did not promote the germination of celery (Apium graveolens L.) seeds and 6‐Δ2‐isopentenyladenine (2iPA) and its riboside were only moderately active. Of the synthetic cytokinins, kinetin, kinetin riboside, and the disubstituted urea, N‐phenyl‐N′‐pyridyl urea (NC5392) were moderately active, and 6‐benzyl‐aminopurine (BA) and its derivatives BA riboside and 6‐benzyl‐amino‐9(tetrahydropyran‐2yl)purine (SD8339) were the most active cytokinins tested. 6‐(o‐hydroxybenzyl)aminopurine (hyd‐BA) and its naturally occurring riboside inhibited germination under normally inductive conditions.

All the cytokinins examined were more active in promoting germination of lettuce (Lactuca sativa L.) than celery seeds. BA, BA riboside and SD8339 were again the most active cytokinins. In contrast to the results with celery, zeatin and zeatin riboside were highly active. The other cytokinins also showed high activity with the exception of dihydrozeatin, hyd‐BA and hyd‐BA riboside which were less active. Cytokinin ribosides were less active than the corresponding free bases during the early period of the lettuce seed incubation but total germination after 90 h was similar.
Effect of Salinity on the Photosynthesis of the Halophyte Salicornia rubra and Distichlis stricta
Authors: TIKU B. L.
Published: April 2006

The photosynthesis and biomass production of two contrasting species, Salicornia rubra and Distichlis stricta from the same habitat, were studied under different light intensities and osmotic conditions. Application of NaCl increased the biomass and succulence of Salicornia and decreased that of Distichlis. Ethylene glycol, EG mol. wt. 62.07, and 1:1 NaCl‐EG killed Salicornia and affected Distichlis adversely. The CO2 uptake of both the species increased with increasing light intensity and was strongly influenced by the application of NaCl. All concentrations of NaCl stimulated the CO2 uptake of Salicornia, but decreased that of Distichlis. NaCl significantly decreased the light compensation point of Salicornia but had no effect on that of Distichlis. The CO2 efflux of the two species at 4.52 klx was not significantly different. The rate of CO2 uptake of both the species declined with time at all levels of treatment. Salicornia had a more rapid decline in CO2 uptake in absence of NaCl, whereas that of Distichlis was relatively unaffected by it.

Although the tissue Na concentration of the two species increased with increasing NaCl concentration in the medium, the increase in Salicornia was 3.0 to 5.5 times greater than that of Distichlis. Increasing NaCl concentration decreased the chlorophyll concentration of Salicornia and increased that of Distichlis. This resulted in higher ratios of photosynthesis/chlorophyll concentration in Salicornia as against lower ratios in Distichlis. The tissue OP (osmotic potential) of both the species decreased with decreasing OP of the medium. In Salicornia the tissue OP decrease was concurrent with an increase in the CO2 uptake, whereas the CO2 uptake of Distichlis declined with decreasing OP of the medium despite a decrease in its tissue OP. It is concluded that Salicornia requires NaCl for its normal development, whereas Distichlis is adversely affected by it. Both species however, are better adapted to osmotic stress due to natural osmotic agents like NaCl, than to the osmotic stress due to artificial osmotic agents like ethylene glycol.