bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological Changes in the Hemiparasite Rhinanthus serotinus before and after Attachment
Authors: KLAREN CHRISTINE H. , JANSSEN GREET
Published: April 2006

Growth of the hemiparasite Rhinanthus serotinus (Schönh.) Oborny was greatly stimulated after attachment of the parasite to the roots of the host plant, Hordeum vulgare L. In order to find the limiting factors for the growth of Rhinanthus without a host, unattached and attached Rhinanthus plants were compared. Within I day after attachment the contents of nitrogen, phosphorus, potassium, magnesium, and sodium increased considerably. Organic nitrogen and phosphorus compounds were rapidly synthesized in attached Rhinanthus. The accumulation of sugars in unattached Rhinanthus and the decrease in sugar content after attachment suggested that the main requirement from the host was not for carbohydrates.
Effects of Crude Oil and Aromatic Hydrocarbons on the Photosynthesis of the Diatom Nitzschia palea
Authors: KUSK KRESTEN OLE
Published: April 2006

The rate of light saturated photosynthesis of Nitzschia palea was reduced by crude oil, naphthalene and benzene. A decrease in the rate of photosynthesis at weak irradiance was also found with crude oil and naphthalene and high concentrations of benzene. On a mg/1 basis naphthalene decreased photosynthesis to a greater extent than did crude oil and crude oil to a greater extent than did benzene. A linear proportionality was found between the decrease in light saturated photosynthesis and the concentrations of aromatic hydrocarbons. The effects on photosynthesis were generally reversible, but a concentration of 700 mg benzene/1 stopped photosynthesis completely and irreversibly.
Photo‐oxidative Degradation of Chlorophyll‐a and Unsaturated Lipids in Liposomal Dispersions at Low‐Temperature
Authors: DE KOK LUIT J. , VAN HASSELT PHILIP R. , KUIPER PIETER J. C.
Published: April 2006

Liposomal dispersions in water were used as a tool to study photo‐oxidation of chlorophyll‐a and photo‐oxidation of unsaturated lipids at 1 or 4°C. The presence of monogalactosyl diglyceride stimulated chlorophyll‐a degradation. In addition the level of linolenic acid was decreased in liposomal dispersions containing chlorophyll‐a, dipalmitoyl phosphatidyl choline, and monogalactosyl diglyceride, indicating that monogalactosyl diglyceride and chlorophyll‐a were coupled in the preparations. In liposomal dispersions containing equal (molar) quantities of a‐tocopherol, monogalactosyl diglyceride, and chlorophyll‐a, a‐tocopherol fully protected linolenic acid against photo‐oxidative degradation, while chlorophyll‐a degradation was only slightly reduced. In liposomal preparations containing a‐tocopherol, chlorophyll‐a and phosphatidyl choline, a‐tocopherol catalyzed degradation of chlorophyll‐a. Absorption spectra of the liposomal dispersions showed that the presence of a‐tocopherol caused increased absorption in red light, which was attributed to structural changes in the liposomal preparations and thus could explain the noted effects. Tocopherol itself was rapidly degraded in chlorophyll‐a containing liposomal preparations. Complex formation between chlorophyll‐a and monogalactosyl diglyceride in chloroplasts is suggested and protection by a‐tocopherol against photo‐oxidation in chilling‐sensitive plants; a suggestion which is founded on the similarities that exist between chloroplast preparations and liposomal preparations containing chlorophyll‐a and monogalactosyl diglyceride as regards photo‐oxidative degradation of chlorophyll‐a, a‐tocopherol and linolenic acid.
Adaptation of the Photosynthetic Apparatus of Scenedesmus obliquus to Strong and Weak Light Conditions
Authors: SENGER HORST , FLEISCHHACKER PH.
Published: April 2006

Homocontinuous cultures of the unicellular green alga Scenedesmus obliquus were grown under strong (28 W/m2∼28,000 lux) and weak (5 W/m2∼5000 lux) light conditions to simulate the conditions of ‘sun’ and ‘shade’ plants. As in higher plants the cells adapted to strong light had less chlorophyll but demonstrated a higher photosynthetic capacity and a higher respiration rate, so that their compensation point was reached at three times higher energy than in the cells grown under low light intensities. The CO2 fixation rate and the RuDP carboxylase activity under saturating light intensities were both higher in the cells grown in strong light. In spite of the differences in the pigment content and in the light saturated photosynthetic capacities for both cultures, the quantum yields of photosynthetic oxygen evolution were equal. As documented for some species of higher plants Scenedesmus is not genetically determined to be either a ‘sun’ or ‘shade’ organism but can adapt its photosynthetic apparatus to the different light intensities.
Adaptation of the Photosynthetic Apparatus of Scenedesmus obliquus to Strong and Weak Light Conditions
Authors: FLEISCHHACKER PH. , SENGER HORST
Published: April 2006

Simulating ‘sun’ and ‘shade’ conditions of higher plants, homocontinuous cultures of Scenedesmus obliquus were grown under 28 W/m2 (∼28,000 lux) or 5 W/m2 (∼5000 lux). In the high light intensity grown culture the photosynthetic capacity per chlorophyll was three times higher than in the low light intensity grown cells. The activity of photosystem II changed parallel to the photosynthetic capacity, whereas photosystem I activity was influenced to a lesser amount by the light intensity under which Scenedesmus was grown. The molar concentration of all cytochromes and reactive plastoquinone were higher in cells grown under high light intensities. Since only plastoquinone activity represented changes equivalent to photosynthetic capacity, its activity is regarded as the rate limiting step. In spite of the changes in the photosystems and the electron transport chains, the size of the photosynthetic units is independent of the light intensity under which the cells are grown. The results reported for Scenedesmus represent a striking similarity to those published for higher plants grown under different light intensities.
Effects of Acetazolamide (Diamox), Ethoxzolamide and High Levels of CO2 on Carbonic Anhydrase, Photosystem Activity, and Oxygen Evolution in Euglena gracilis
Authors: LONERGAN THOMAS A. , SARGENT MALCOLM L.
Published: April 2006

Investigations using steady‐state culture conditions indicate that carbonic anhydrase activity is correlated to the photosynthetic rate in Euglena in some but not all circumstances. When cultures grown with 5% CO2 were changed to air growth, the photosynthetic rate was independent of the carbonic anhydrase activity.

While experiments using the inhibitor acetazolamide indicated a close correlation between photosynthetic capacity and carbonic anhydrase activity, the inhibitor was found to be nonspecific. Acetazolamide altered photosystem activities directly as measured by the photoreduction of DCPIP in chloroplast preparations, whole‐cell fluorescence transients of chlorophyll a, and by whole chain photoelectron flow. Ethoxzolamide, another inhibitor of carbonic anhydrase, was also found to inhibit photosystem activities, i.e., the photoreduction of DCPIP, and in vivo photoelectron flow, at high concentrations.

Cells grown in 5% CO2 were less sensitive to the effects of acetazolamide than cells exposed to air. The rate of electron flow in chloroplasts from cells grown with 5% CO2 and exposed to 10 mM acetazolamide was 2.5‐fold faster than that of chloroplasts from air‐grown cells exposed to the same concentration of inhibitor. The whole cell chlorophyll a fluorescence transients of cultures grown with high CO2 were completely different from those of air‐grown cells and also showed fewer effects on exposure to acetazolamide.

These results suggest a reevaluation of the hypothesis that carbonic anhydrase activity regulates photosynthesis. It is also apparent that results from air‐grown and 5% CO2‐grown cultures cannot be directly compared in such studies.
Response of Substituted Indoleacetic Acids in the Indolo‐α‐pyrone Fluorescence Determination
Authors: BÖTTGER MICHAEL , ENGVILD KJELD C. , KAISER PETRA
Published: April 2006

The method of indolo‐α‐pyrone fluorescence‐determination of indoleacetic acid was investigated to study possible interference from 4‐chloro‐indoleacetic acid and 5‐hydroxyindoleacetic acid, which occur naturally. Both compounds show about 40% of the fluorescence of indoleacetic acid after conversion into their a‐pyrones. Other halogenated indoleacetic acids show between zero and 60% of the fluorescence of indoleacetic acid.

It is concluded that the concentration of indoleacetic acid cannot be determined in crude extracts in the presence of 4‐chloro‐ or 5‐hydroxy‐indoleacetic acid, because separate determinations of each of these compounds are not possible by changing the excitation or fluorescence wave‐lengths of the testing equipment.
Attenuation of the Petal Movement Rhythm in Kalanchoë with Light Pulses
Authors: ENGELMANN WOLFGANG , JOHNSSON ANDERS , KARLSSON H. G. , KOBLER R. , SCHIMMEL M.‐L.
Published: April 2006

The circadian petal movement rhythm of Kalanchoë flowers has been studied. The amplitude of the rhythm can be drastically reduced by an appropriate stimulus of a light pulse. It has also been shown that it is possible to stop the rhythm permanently by administering a single light pulse to the flowers. This is interpreted to indicate that the light pulse has sent the circadian rhythm into a stable state of singularity.

The conditions which attenuate the rhythm have been investigated both theoretically (on the basis of a previously published model for circadian rhythms) and experimentally. 120 min red light of 230 μW · cm−2, starting briefly before the second petal closure about 30 h after transfer to constant safe light conditions is optimal in inducing rhythm‐damping. Damping requires the same duration when the light is given at the corresponding phase during the third or fourth cycle of the rhythm. However, in the first cycle 240 min red light of 230 μW · cm−2 is required to get optimal damping of the rhythm.

Conditions to achieve damping for other irradiances are investigated. Individual recordings are presented which show the behaviour of the rhythm when perturbed by light stimuli close to its singularity.
Cytokinin Activity in Lupinus albus
Authors: DAVEY J. E. , VAN STADEN J.
Published: April 2006

The cytokinin activity of the root exudate, the leaves, and the apices of vegetative and flowering white lupin plants (Lupinus albus L.) was investigated. The level of cytokinin activity in the root exudate decreased over the 11‐week experimental period. Four peaks of cytokinin activity were recorded in the root exudate of 8‐week‐old plants after fractionation on Sephadex LH‐20. Two of these peaks co‐eluted with zeatin and zeatin riboside. It is suggested that the remaining peaks represent nucleotide and glucoside cytokinins. The cytokinin levels in extracts of the mature leaves fluctuated slightly over the experimental period. Three peaks of activity co‐eluting with zeatin, zeatin riboside and the glucoside cytokinins were recorded in extracts of mature leaves of 8‐week‐old plants. In the apices cytokinin activity could only be detected in the inflorescences of flowering plants. It would appear that cytokinins produced by the roots accumulate in the fully expanded mature leaves, but are utilized in the rapidly growing apical region and in young expanding leaves.
The Effect of Activated Charcoal on Tissue Cultures: Adsorption of Metabolites Inhibiting Morphogenesis
Authors: FRIDBORG GUNNAR , PEDERSÉN MARIANNE , LANDSTRÖM LARS‐ERIK , ERIKSSON TAGE
Published: April 2006

Cell suspensions of Daucus carota and Haplopappus gracilis and callus suspensions of Allum cepa var. proliferum were grown in media with and without activated charcoal. Differentiation occurred in those Daucus and Allium cultures that contained charcoal. It was shown by mass spectrometry that the media without charcoal contained high amounts of phenylacetic acid and p‐OH‐benzoic acid (Daucus), 2,6‐OH‐benzoic acid (Allium) and benzoic acid, pelargonic acid and caprylic acid (Haplopappus), whereas the media with activated charcoal did not. It was also shown that p‐OH‐benzoic acid had inhibitory effects on the embryogenesis in Daucus cultures.
Photochemical Characteristics of Mesophyll and Bundle Sheath Chloroplasts from C4 Plants
Authors: RAGHAVENDRA AGEPATI S. , DAS V. S. R.
Published: April 2006

Mesophyll and bundle sheath chloroplasts were isolated by differential grinding from the leaves of two NADP‐ME C4 plants, Setaria italica Beauv. cv. H‐1, Pennisetum typhoides S & H. cv. AKP‐2, and a NAD‐ME C4 species Amaranthus paniculatus L. The mesophyll chloroplasts of C4 plants possessed slightly lower Km for ADP and Pi than those of bundle sheath chloroplasts.

The Hill reaction activities and noncyclic photophosphorylation rates of the bundle sheath chloropiasts from S. italica and P. typhoides were less than one‐fifth of those by the mesophyll chloroplasts. But the bundle sheath chloroplasts of A. paniculatus exhibited high rates of Hill reaction, cyclic as well as noncyclic photophosphorylation. The pigment‐ and eyiochrome composition suggested a relative enrichment of PS 1 in bundle sheath chloroplasts of S. italica and P. typhoides. The chain exists in both mesophyll and bundle sheath chloroplasts. As much as 35–52% of leaf chlorophyll was located in the bundle sheath chloroplasts. The photochemical activities of bundle sheath chloroplasts are significant though a major part of leaf photochemical potential is associated with the mesophyll chloroplasts.
Changes in Ion Transport in Spring Wheat during Ontogenesis
Authors: JENSÉN PAUL
Published: April 2006

The influence of plant age on free space uptake to the root, rate of continuous uptake and translocation of potassium and sulphate was investigated during about 100 days in intact, high‐salt plants of spring wheat (Triticum aestivum L. cv. Svenno). The plants were grown in a green‐house in complete nutrient solution. For the short term uptake experiments, the test solutions were labelled with 36Rb+ and 35S‐sulphate.

Free space uptake to the roots increased during the entire growth period. The SO2‐4 free space uptake was divided into a Water Free Space (WFS) fraction and a labile‐bound fraction. The labile‐bound SO2‐4 was considered to be constant during development, and the WFS fraction of SO−24 could then be computed. WFS increased from 2% of total cell volume in 1‐day‐old plants to 30% in 100‐day old plants, apparently due to an increasing proportion of freely permeable root cells. As the WFS fraction of the free space uptake was known, the binding capacity (BC) of K+(86Rb−) of the cell walls and at the cytoplasmic surfaces could be computed. It is suggested that the increasing BC for cations with age was due to an increasing proportion of soluble pectate in the cell walls.

Except for the initial 20 days, the continuous ion uptake rate decreased during development. It is suggested that the low uptake rate in young plants is limited by the energy supply to the roots and that the decreased uptake in older plants is due to the increasing proportion of metabolically inactive and collapsed roots. At the end of the cultivation period the ion uptake rate increased at the same time as there was a shift from active to passive ion uptake. This was shown by uptake experiments with 2,4‐dinitrophenol (2,4‐DNP).

By changing the air humidity around the shoots and using 2,4 DNP, it was shown that ion and water uptake were closely linked to root activity in young plants but that transpiration pull became gradually more important for water uptake with age.
Influence of Nitrogen and Sucrose in the Medium and of Irradiance of the Stock Plants on Root Formation in Pelargonium Petioles Grown in vitro
Authors: WELANDER TORKEL
Published: April 2006

In vitro root formation was studied in petiole explants from Pelargonium×hortorom Bailey cv. Radio exposed to different irradiance (2.5. 11.6 or 23.0 W/m2). Optimal root formation was found when stock plants were subjected to 2.5 W/m2 and explants were grown on a medium with 20 g/I of sucrose and 5.0 mM of nitrogen. The number of roots per explant decreased with increasing nitrogen or sucrose concentrations in the growth medium and with increasing irradiance applied to the stock plants. Variation in temperature (17, 21 or 25°C) did not affect root formation. The number of roots per explant was higher in explants from young petioles than in explants from older petioles.

The initial nitrogen content of the explants was highest at the lowest irradiance. The content of reducing sugars and sucrose increased with increasing irradiance. The endogenous levels of lysine, arginine and ornithine were highest at 2.5 W/m2 and the levels of proline. alanine, γ‐aminobutyric acid, glutamic acid, glutaminc, aspartic acid and asparagine were highest at 23.0 W/m2.

With rising nitrogen concentration in the medium, the final endogenous content of nitrogen in the explants increased, whereas the content of reducing sugars decreased. When the sucrose concentration in the medium increased, the endogenous content of reducing sugars rose, and the nitrogen level was lowered. Variations in the nitrogen concentration in the growth medium influenced the final level of free amino acids in the explants.
Changes in the Endogenous Cytokinins of Bark and Buds ofSalix babylonica as a Result of Stem Girdling
Authors: VAN STADEN J. , BROWN N. A. C.
Published: April 2006

Girdling of 1‐year‐old Salix babyionica L. plants resulted in an early accumulation of compounds which co‐chromatographed with cytokinin glucosides in both the bark and buds below the girdle. In the bark the cytokinin glucosides were present in high levels in both girdled and non‐girdled plants. In the buds of non‐girdled plants. however, glucoside concentration was initially low but then increased rapidly after ringing and reached a maximum level prior to any visible signs of bud swell. With the onset of lateral shoot growth the glucoside cytokinins decreased while the cytokinins that co‐chromatographed with zeatin and its derivatives increased. As the cytokinin glucosides are generally considered to be storage forms, their accumulation in the bark and buds below the girdle apparently does not reflect synthesis but rather transport towards a more competitive sink. In the case of Salix plants the lateral buds would appear to have the ability to hydrolyze these glucosylated zeatin derivatives and then to utilize them for bud development. It is suggested that in the presence of a functional root system lateral buds do not synthesize cytokinins de novo, but that they do have the metabolic capacity to convert cytokinins transported to them.
Critical Water Potential for Stomatal Closure in Sitka Spruce
Authors: BEADLE C. L. , TURNER N. C. , JARVIS P. G.
Published: April 2006

Steady state rates of net photosynthesis and stomatal conductance at high water potentials were measured under controlled conditions in a leaf chamber on Sitka spruce [Picea sitchensis (Bong.) Carr.] shoots detached from the forest canopy or on seedlings. The water supply to the seedlings was terminated by excision and the shoot water potential (or critical water potential) and osmotic potential at the onset of stomatal closure measured. The turgor potential was calculated. The initial osmotic potential before insertion of the shoot into the chamber was also measured. Shoot water potential and osmotic potential at stomatal closure, and initial osmotic potential were significantly higher (less negative) in foliage from the lowest level in the canopy compared with foliage in the upper canopy, and higher in shoots of seedlings transferred to low light than in those at high light. Critical water potential also varied with season, being higher in July than in October and November. In all except one instance, turgor potential at the onset of stomatal closure was negative, possibly because of dilution of the cell sap by the extracellular water during the estimate of osmotic potential.

Over all the experiments variation in critical water potential was correlated with variation in critical osmotic potential and, to a lesser extent, the initial osmotic potential. However, turgor potential at the critical potential varied from +0.6 to ‐4.6 bar. This suggests that difference in turgor between the guard cells and subsidiary cells, which controls stomatal aperture, is only loosely coupled with the bulk leaf turgor and hence that bulk leaf turgor is not a good index of the turbor relations of the guard cells.
Effects of Ca2+ and Temperature on K+ Content Distribution along Roots of Wheat, Rice and Cucumber
Authors: ZSOLDOS FERENC , KARVALY BÉLA
Published: April 2006

The effects of Ca2+ and temperature on the K+ contents of root segments of wheat (Triticum aestivum L. cv. Aurora), rice (Oryza sativa L. cv. Dunghan Shali) and cucumber (Cucumis sativus L. cv. Csemege Fürtös) were investigated with special regard to the low‐temperature anomaly of the K+ uptake of thermophilic plants. The anomaly occurred in those root segments where the K+ contents turned out to be highest. The K+ contents of the apical root sections of thermophilic species responded in general to Ca2+ in more pronounced ways than those of wheat, at both 0 and 25°C. The concerted actions of a purely physical process with negative temperature coefficient and of the special thermotropic properties of the membranes are suggested to be responsible for the low‐temperature anomaly. A strict discrimination between the Viets‐effect on the content (classical Viets‐effect) and on the uptake is proposed. The classical Viets‐effect seems to be related to alterations in both active transport and exchange processes.
Lowering of Endogenous Lipoxygenase Activity in Pisum sativum Foliage by Cytokinin as Related to Senescence
Authors: GROSSMAN SHLOMO , LESHEM YA'ACOV Y.
Published: April 2006

Cytokinin (CK), when applied to intact pea plants, considerably lowered endogenous lipoxygenase levels. Furthermore it was demonstrated that the triggering of senescence induced by leaf detachment was invariably accompanied by a significant increase of lipoxygenase activity and the CK application considerably decelerates lipoxygenase increment. It is suggested that the lipoxygenase repression induced by CK is a contributing mechanism to the overall antisenescence action of the hormone, and that this may have biological implications.
Physiology of Rice Tungro Virus Disease: Increased Cytokinin Activity in Tungro‐Infected Rice Cultivars
Authors: SRIDHAR R. , MOHANTY SUSANTA K. , ANJANEYULU A.
Published: April 2006

Tungro virus infection decreased the chlorophyll content in the susceptible rice (Oryza sativa) cultivar ‘Taichung Native 1’, while it increased the pigment in the less‐susceptible cultivar ‘IR 20’ during the later stages of infection. The virus was recovered from the infected susceptibile cultivar as early as 3 days after inoculation. Relatively low amounts of virus were recovered from the less‐susceptible cultivar between 12 and 30 days after inoculation. The senescence of detached leaves of virus‐infected less‐susceptible cultivar incubated in water in darkness was considerably delayed compared to healthy leaves. The cytokinin activity in the extracts from inoculated less‐susceptible cultivar was 69% higher than in the extracts from the healthy plants.
Response of Eucalyptus occidentalis to Water Stress Induced by NaCl
Authors: ITAI CHANAN
Published: April 2006

Eucalyptus occidentalis plants were exposed to NaCl in their culture solution for various time. Determination of cytokinin, abscisic acid, 14C leucine incorporation of E. occidentalis, a xerophyte, does not differ from the response of mesophytes to such treatments.
Rapid, Blue‐Light Induced Transpiration in Avena
Authors: SKAAR H. , JOHNSSON A.
Published: April 2006

The transpiration responses of primary Avena leaves to blue‐light pulses were investigated. Only light with wave length shorter than 524 nm can produce the rapid transpiration response. The action spectrum has a maximum around 450 nm. The rapid transpiration response induced by blue‐light pulses successively disappeared in long‐term experiments if the plant was kept in darkness between the pulses. However, if visible light was given to the plant between the pulses, the rapid response was restored.

The magnitude of the rapid transpiration response was investigated under different conditions of background illumination and blue‐light exposure. Saturation of the response was obtained with an irradiation level of 1.5–2 mW.cm−2 (5 min pulses) and with a pulse duration of 4 min (pulse irradiance 2 mW.cm−2). A pulse duration of 3 s was sufficient to produce a significant rapid response at an irradiation level of 2 mW.cm−2.
Different Effects of Tris and Histidine on a Membrane Bound NaK ATPase from Sugar Beet Roots
Authors: LINDBERG SYLVIA , HALLMÉN GUN
Published: April 2006

A membrane fraction of sugar beet roots prepared in the presence of dithiothreitol contains (Na++ K++ Mg2+) ATPase activity. This activity was studied in the presence of different concentrations of Tris and histidine. Tris was found to interact with the ATPase in the following way: (1) Tris at 50 mM increases, in the absence of Na and/or K, the activity in an uncompetitive way with respect to MgATP. (2) Concentrations of Tris > 50 mM cause inhibition in the absence of Na and K when the ratio between MgATP and Tris is relatively low. (3) Though Tris at 50 mM stimulates similarly to Na, it can not substitute for Na in the Na + K activation. (4) In the presence of Na and K, Tris acts as a competitive inhibitor. Histidine has little influence on the rate both in the presence and absence of Na and/or K.
Inactivation of Nitrate Reductase of the Yeast, Rhodotorula glutinis
Authors: ITO NOBUAKI , SUZUKI YONEZO
Published: April 2006

Nitrate reductase (NR) from the yeast, Rhodotorula glutinis var. salinaria was composed of two enzymatic components, diaphorase and terminal nitrate reducing moieties. The enzyme used NADPH as electron donor and FAD as cofactor. The synthesis of nitrate reductase was promoted specifically by nitrate and repressed by ammonium and amino acids. Nitrate reductase from this yeast had an inactive as well as an active form. Inactive enzyme was reactivated by oxidation with ferricyanide in vitro. Hydroxylamine promoted the formation of inactive enzyme in vivo. Ammonium could neither promote the inactivation nor reduce the total level of nitrate reductase activity. Nitrate could protect nitrate reductase from inactivation caused by nitrogen starvation or hydroxylamine.
Photodecomposition of Monogalactosyl Diglyceride Mediated by Chlorophyll
Authors: SELSTAM EVA
Published: April 2006

In acetone extracts the presence of chlorophyll a and b caused enhanced photodecomposition of monogalactosyl diglyceride. Irradiation of isolated etioplasts containing chlorophyllide and monogalactosyl diglyceride caused photodecomposition of chlorophyllide but not of monogalactosyl diglyceride. In irradiated etiochloroplasts containing chlorophyll a and monogalactosyl diglyceride both components were photodecomposed. During photodecomposition of monogalactosyl diglyceride the fatty acid composition remained constant.
Seasonal Changes in Total Free Sugar Content of Field Cocoa Plants
Authors: OWUSU J. K. , ADOMAKO D. , HUTCHEON W. V.
Published: April 2006

As part of a study of factors affecting the vegetative and reproductive characteristics of cocoa, Theobroma cacao L., (viz. leaf flushing, flowering, cherelle wilt, pod setting and pod growth), seasonal changes in total free sugar levels of the bark and wood of field cocoa trees growing under medium shade provided by Gliricidia sepium Steud. trees were studied over a period of 13 months. On dry weight basis, sugar content of the bark (13 to 63 mg/g) was higher than that of the wood (9 to 40 mg/g). Free sugar content was significantly correlated with sunshine hours for the whole period, except October‐November 1975, and March 1976 when pod load, and flowering and leaf flushing respectively, caused considerable reduction in free sugar levels. The peaks of flowering and flushing coincided with those of sunshine hours and free sugar levels. The results, analysed in terms of the prevailing microclimatic conditions, suggest that light is a limiting factor for photsynthesis of shaded cocoa and that the reported stimulation of flowering and leaf flushing, which accompany shade removal, may be attributed to increased sugar status of the trees due to increased photosynthetic activity.
Leucine Uptake and Incorporation by Convolvulus Tissue Culture Cells and Protoplasts under Severe Osmotic Stress
Authors: RUESINK ALBERT W.
Published: April 2006

The uptake and incorporation of radioactive leucine by Convolvulus arvensis L. suspension culture cells were studied under various osmotic conditions to provide information about the effects of osmotic stress at the cellular level and about the suitability of various osmotica for stabilizing protoplasts. When manitol, sorbitol, sucrose, or a mixture of CaCl2 and KCl was added to the cells at a concentration normally used to stabilize protoplasts, the uptake of leucine was inhibited by 50 to 60% and incorporation by 37% with no major differences detected among these osmotica. NaNO3 of a similar osmotic strength exerted considerably more inhibition, an inhibition that was reversed by as little as 10 mM simultaneous CaCl2. None of the osmotica altered leucine or protein leakage from the tissue. In general, external solute concentrations below 0.36 osmolal slightly enhanced uptake and incorporation. At successively higher concentrations, uptake and incorporation decreased in a linear fashion, with no apparent discontinuity in the rate of decrease as the cells plasmolyzed. Cycloheximide inhibited both the uptake and the incorporation of leucine in all osmotic situations tested, exerting a much stronger inhibition upon the uptake by control tissue than upon that by cells in osmotica. Different cellulase enzyme preparations varied considerably in their effects on subsequent leucine uptake and incorporation.
Relation between Nitrogen Nutrition, Cytokinin Activity and Tuberization in Solanum tuberosum
Authors: SATTELMACHER B. , MARSCHNER H.
Published: April 2006

In water‐culture experiments with potato plants (Solanum tuberosum L. cv. Ostara), the influence of tuberization initiated by a 7‐day period of nitrogen withdrawal (discont. N) on the cytokinin activity in shoots, roots and exudate was studied. Plants with a constant supply of nitrogen (cont. N) were used as control. — Whereas no tuberization could be observed with cont. N, discont. N led to tuberization already 2 days after nitrogen withdrawal and all plants had been induced after another 4 days. In the roots of plants with discont. N, there was a temporary increase in cytokinin activity, whereas the activity decreased steadily with cont. N. In the exudate, cytokinin activity was greatly reduced during nitrogen withdrawal, whereas this activity in the exudate increased steadily with cont. N. — In the shoot with cont. N cytokinin activity decreased steadily, but with discont. N, after an initial decrease, the activity increased steeply. This increase is mainly or exclusively caused by a shift between the water‐soluble and butanol‐soluble fractions of the cytokinins in favour of the latter. The shift in cytokinin activity of the shoot is assumed to be in causal connection with an increased photosynthetic activity after the onset of tuber growth as ‘sink’ for assimilates.
Cytokinin Activity in Stolons and Tubers of Solanum tuberosum during the Period of Tuberization
Authors: SATTELMACHER B. , MARSCHNER H.
Published: April 2006

In water‐culture experiments with potato plants (Solanum tuberosum L. cv. Ostara), changes in cytokinin activity in the stolon tips and newly formed tubers during tuberization were studied. Tuberization was induced by withdrawing nitrogen from the nutrient solution. — The cytokinin activity was low in the stolon tips prior to tuberization, but increased considerably in both stolon tips and young tubers during tuberization. At the same time qualitative changes in the cytokinin spectrum occurred. These qualitative changes are reversible if ‘regrowth’ of young tubers is brought about by a sudden high supply of nitrogen. — Despite the close correlation between tuberization and cytokinin activity, it is assumed that cytokinins are not directly responsible for the onset of tuberization, although they play an important role in tuber growth.
The Metabolism of the Herbicide Diphenamid (N‐N‐dimethyl‐2,2‐diphenyl‐acetamide) in Cell Suspensions of Soybean (Glycine max)
Authors: DAVIS D. G. , HODGSON R. H. , DUSBABEK K. E. , HOFFER B. L.
Published: April 2006

The fate of the herbicide diphenamid was determined in cell suspensions of soybean [Glycine max (L.) Merr. ‘Wilkin’] at different stages of cell growth: early log phase (3 to 7 d), log phase (7 to 14 d), and stationary phase (14 to 18 d). [Carbonyl‐14C]‐diphenamid was added to the suspensions as an acetone solution. Neither diphenamid (2 to 3 μM) nor acetone (0.5% v/v) was phytotoxic. The 14C‐labeled products were identified tentatively by thin layer chromatographic comparison with reference compounds. The major metabolic products formed were N‐hydroxymethyl‐N‐methyl‐2,2‐diphenylacetamide, N‐methyl‐2,2‐diphenylacetamide, 2,2‐diphenylacetamide, and two polar metabolites (0.9 to 25% of the applied 14C activity) that appeared to be glucose conjugates; one an acidic glucoside. All metabolites were found in both the cell extract and the culture medium, except for the acidic glucoside, which was recovered in small amounts only from the cell extracts. These products were the same as those recovered from intact plants. Similar results were obtained from cell suspensions of different ages. The rate of metabolism by log phase cells was slightly less than the rate for either young or old cells. The results indicated that soybean cell suspensions can be used to obtain reliable information on the fate of agricultural chemicals in soybeans.
Effect of Water Stress on the Temperature Optima of Net CO2 Exchange for Two Desert Species
Authors: NOBEL PARK S. , LONGSTRETH DAVID J. , HARTSOCK TERRY L.
Published: April 2006

The temperature dependence of net CO2 exchange was determined at various soil water potentials for two sympatric desert species. Notholaena parryi D. C. Eat. (Pteridaceae) and Encelia farinosa Gray (Compositae). As water stress increased, the temperature optimum of apparent (net) photosynthesis shifted 7 to 10°C downward and the maximum rate decreased for both species. The downward shift in temperature optimum with water stress was the result of a greater fractional stomatal closure with increasing temperature and a lowering of the temperature where maximal CO2 residual conductance of the mesophyll cells occurred. This lowering of the temperature for maximal CO2 residual conductance appears to reflect (1) a greater effect of water stress on gross photosynthesis than on respiration plus photorespiration and (2) the higher temperature optimum for respiration plus photorespiration than for gross photosynthesis. The downward shift in the temperature optimum of apparent photosynthesis can have a significant effect on the predicted carbon balance of plants as the soil water potential decreases.
Seasonal Effects on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris
Authors: MARTIN BJÖRN , MÅTENSSON OLLE , ÖQUIST GUNNAR
Published: April 2006

Chloroplasts were isolated from primary needles of 1‐year‐old seedlings and from secondary needles of a 20‐year‐old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20‐year‐old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1‐year‐old showed the same general trends as observed in the 20‐year‐old tree, but the changes were less pronounced. However, in snow‐covered seedlings the PSI‐mediated electron transport and the electron transport from H2O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyll a antennae closely associated with the two photosystems than of the light harvesting chlorophyll a/b complex. In this case, too, the changes were more pronounced in the 20‐year‐old tree than in the 1‐year‐old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter were mainly reversed during spring.
Allosteric and Non‐Allosteric Regulation of Rubidium Influx in Barley Roots
Authors: PETTERSSON SUNE , JENSÉN PAUL
Published: April 2006

Uptake of Rb+ was investigated in 6–8‐day‐old intact barley plants (Hordeum vulgare cv. Kristina), which had been cultivated or pretreated in nutrient solutions with various K+ concentrations. The relationship between Rb+ influx and the K+ concentration of roots appeared to be sigmoidal for plants grown in solutions containing K+, indicating regulation of Rb+ uptake by allosteric inhibition of the uptake mechanism. Pretreatment of the roots in K+‐free solutions changed the pattern of uptake and caused the Rb+ influx to become linearly related to the chemical Rb+ potential of the uptake solution. Pretreatment in K+‐free solutions probably abolishes the allosteric inhibition of a carrier system.
Light‐Induced Phosphate Binding in Relation to Photophosphorylation and Levels of ATP, ADP and AMP in the Green Alga Scenedesmus
Authors: LARSSON C.‐M. , TILLBERG J.‐E. , HALLMÉN G.
Published: April 2006

Synchronous cultures of Scenedesmus obtusiusculus Chod. were starved for phosphorus for 48 h. Such cells develop an efficient mechanism for phosphate binding which is very sensitive to metabolic inhibitions. Phosphate binding, fluctuations in the ATP pool during dark‐light‐dark transitions, and steady state levels of ATP, ADP and AMP were studied. The experiments were carried out in a CO2‐free N2 atmosphere. DCMU, phloridzin and 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐p‐benzoquinone (DBMIB) were used as inhibitors of photophosphorylation.

Light‐induced phosphate uptake was inhibited to various extents by all the inhibitions. The dark‐light‐dark transition experiments show that neither the light‐induced increment in ATP nor the decrease at darkening are affected by DCMU, but DBMIB and phloridzin inhibit both processes. DCMU seems to affect the regulation of the ATP pool size. The steady state levels of the adenylate pools were almost the same in the light as in the dark, and they were also little sensitive to the inhibitors. In unpoisoned cells in the light the steady state ATP/ADP ratio was 1.7 and the energy charge was 0.66.

The rates of phosphate binding are not correlated to any of the adenylate parameters studied. This is probably due to the diverse effects of the inhibitors on light‐stimulated production of reducing equivalents, photophosphorylation and transfer of energy from the chloroplast to the cytoplasm.
Changes in the Ability of Photophosphorylation and Activities of Surface‐Bound Adenosine Triphosphatase and Ribulose Diphosphate Carboxylase of Chloroplasts Isolated from the Barley Leaves Senescing in Darkness
Authors: BISWAL U. C. , MOHANTY PRASANNA
Published: April 2006

Dark‐induced aging of detached primary leaves of 11‐day‐old barley seedlings brings about a significant decline in the rates of ferricyanide [Fe(CN)6]3− reduction and photophosphorylations of isolated chloroplasts. Ferricyanide‐supported noncyclic photophosphorylation is somewhat more susceptible to leaf aging than phenazine methosulfate (PMS)‐supported cyclic phosphorylation. Non‐latent membrane‐bound adenosine triphosphatase (ATPase) and ribulosediphosphate carboxylase (RuDPCase) lose about half of their initial activities after 24 h, while during this period the electron transport and photophosphorylation activities are much less affected. Also, the loss of RuDPCase is almost complete, while chloroplasts still exhibit a significant level of [Fe(CN)6]3− reduction and photophosphorylations after 7 days of dark incubation. This would suggest that the enzymatic dark reactions are more sensitive to aging stress than the primary photochemical reactions of chloroplasts.

Studies on the effect of divalent cations such as Mg2+ and Ca2+ on non‐latent ATPase activity revealed that the dark stressed aging of detached leaves brings about a time dependent alteration in the response of this enzyme to Mg2+, but not to Ca2+. The former showed inhibitory as well as stimulatory response, whereas the latter always caused the usual stimulation. Addition of kinetin (50 μM) ensured retention of [Fe(CN)6]3− reduction, photophosphorylations and RuDPCase activity in chloroplasts during leaf aging, but it failed to preserve the initial loss in the activity of the non‐activated membrane‐bound ATPase.
A Two‐Dimensional Separation of Proteins from Chloroplast Thylakoids and Other Membranes
Authors: BOSCHETTI ARMINIO , SAUTON‐HEINIGER ERIKA , SCHAFFNER JEAN‐CLAUDE , EICHENBERGER WALDEMA
Published: April 2006

A two‐dimensional, highly reproducible, analytical separation procedure for Triton/urea extractable proteins, using isoelectric focusing in the first dimension and gelelectrophoresis with sodium dodecylsulfate (SDS) in the second, is described. The separation of erythrocyte membrane proteins compares the reliability with that of published procedures.

From the thylakoid membranes of the green alga Chlamydomonas reinhardii and of spinach, two‐dimensional maps of the Triton/urea extractable proteins were established, containing 58 and 33 peptide spots, respectively, which were characterized by their molecular weights and apparent isoelectric points. In Chlamydomonas some of the spots could be attributed to the photosystem I and II particles. A few major spots in the maps of the thylakoid proteins from the two non‐related plants were found at the same relative positions.

A one‐dimensional electrophoretic comparison of the SDS and the Triton/urea‐extractable proteins showed that in the Triton/urea extract of thylakoid membranes some proteins of the photosystem II region, and in that of erythrocyte membranes, some components of the band 3 and 5 region are reduced or missing.
Dipeptides as Nitrogen Sources for Drosera rotundifolia in Aseptic Culture
Authors: SIMOLA LIISA KAARINA
Published: April 2006

The growth of Drosera rotundifolia was studied in aseptic cultures with 17 dipeptides as the only nitrogen source. About half of the dipeptides were well or partly utilized. Compounds containing glycine, alanine, glutamic or aspartic acid are clearly more favourable than dipeptides containing proline. Arginyl‐aspartic acid (1.25 mM) promoted growth more than inorganic nitrogen (1.25 mM of NH4NO3). Glycyl‐alanine gave about the same growth response as NH4NO3. The inocules died rapidly in medium containing leucyl‐tyrosine and dipeptides containing methionine and valine were also toxic. There was usually a clear correlation between the growth‐retarding or growth‐stimulating effect of the dipeptides and the effects of their amino acid components.
Effects of Water Stress on Cuticular Transpiration Rate and Amount and Composition of Epicuticular Wax in Seedlings of Six Oat Varieties
Authors: BENGTSON CURT , LARSSON STIG , LILJENBERG CONNY
Published: April 2006

Six varieties of oat (Avena sativa L. cv. Stormogul II, Risto, Sol II, Selma, Sang and Pendek, arranged according to decreasing drought resistance) were cultivated under controlled conditions and exposed to water stress on 4 consecutive days. Seven‐day‐old seedlings were stressed by cooling the roots for 3 h to 1.0°C. During this treatment the leaf water potential decreased from ‐7 to ‐12 bars. Cuticular transpiration rate, total amount of epicuticular wax and amounts of some wax components (primary alcohols, alkanes, fatty acids) were determined.

Unstressed seedlings of the most drought resistant variety (Stormogul II) showed the highest cuticular transpiration rate. After stress treatment the cuticular transpiration rate was most strongly reduced in this variety and at the same time it showed the largest increase in amount of epicuticular wax of the tested varieties. In Pendek and Sang, showing the least increase in epicuticular wax, the cuticular transpiration rate was only 5% lower after stress treatment.

In all varieties the primary alcohol content of the epicuticular wax was slightly higher in stressed seedlings than in controls. Further, in Stormogul and Risto the content of the predominant alkanes was much lower in stressed seedlings than in controls. On the contrary, in Pendek the stressed seedlings showed a higher alkane content. In Stormogul II, Risto and Sol II the total amount of fatty acids was higher in stressed seedlings than in controls while the opposite was true in Sang.

The relation between the epicuticular wax (amount and composition) and the cuticular transpiration rate is discussed as well as the possibility of using the tested parameters in a screening test for drought resistance.
Substituted Indoleacetic Acids Tested in Tissue Cultures
Authors: ENGVILD KJELD C.
Published: April 2006

Monochloro substituted indole‐3‐acetic acids inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted indole‐3‐acetic acids inhibited shoot formation less. Other substituted indoleacetic acids except 5‐fluoro‐ and 5‐bromoindole‐3‐acetic acid were less active than IAA. Callus growth was quite variable and not correlated with auxin strength measured in the Avena coleoptile test.
Influence of Gamma Radiation on the Transport of Indolyl‐3‐Acetic Acid in Bark Tissue from Apple Trees
Authors: ANTOSZEWSKI R. , RANGELOV B. , DZIĘLCIOŁ U. , BACHMANN S.
Published: April 2006

The influence of gamma radiation on the polarity of IAA translocation was investigated. Pieces of apple tree shoots, taken from 3‐year‐old trees, were irradiated in a dark irradiation chamber BK‐60Co source, 10 kCi. Doses from 20 to 150 krad were given. Strips of bark were peeled off both irradiated and control shoots. The middle parts of the bark strips were placed on agar blocks loaded with IAA‐1‐14C. The radioactivity of basal and acropetal segments was determined after about 20 h and results expressed as polarity quotient.

It has been shown that irradiation with 20 krad (200 Gy) decreases the polarity quotient remarkably (polarity quotient of control equals 7; for 20 krad—2.9; 100 krad—1.6). The decrease in polarity results from inhibition of the basipetal translocation of IAA. Irradiated tissue shows a decrease in IAA uptake. Possible mechanisms of gamma irradiation effects on polar translocation of IAA are discussed.
Control of Adventitious Root Production and Hypocotyl Hypertrophy of Sunflower (Helianthus annuus) in Response to Flooding
Authors: WAMPLE R. L. , REID D. M.
Published: April 2006

The morphological changes of the shoots of Helianthus annuus cv. Russian caused by varying periods of flooding of the roots were studied. Attention was focused on adventitious root formation and hypocotyl hypertrophy which are known to be caused by excess water around the roots in the absence of anoxia. Twenty‐four hours of flooding was found to be sufficient to cause both of these responses. Experiments involving flooding, leaf removal, shoot apical bud removal, two different light intensities, and a treatment in which only a small proportion of the roots were flooded suggested that a major factor causing the flood‐induced changes in the hypocotyl arises in the root but other factors may come from the leaves. In the longer‐term experiments other flood‐induced changes in shoot morphology were leaf epinasty, death of shoot apex, extreme chlorosis and hypertrophy of nodes and internodes. There was no apparent contribution of adventitious roots to the survival of flooded plants.