bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method for the Isolation of Stable Mesophyll Protoplasts from Tomato Leaves throughout the Year under Standard Conditions
Authors: CASSELLS ALAN C. , BARLASS MARTIN
Published: April 2006

A method is described, based on growing tomato plants under low light intensities and feeding with calcium nitrate, whereby stable protoplasts can be isolated throughout the year under standard conditions. Plants are grown in the equivalent of spring and winter light intensities (i. e. incoming solar radiation 2.52 to 10.8 MJ m−2 day−1 15 h day) in the glasshouse on peat compost supplied with a balanced fertilizer containing nitrate and urea as nitrogen sources and given a supplementary feed of calcium nitrate. Under these conditions, high yields of protoplasts can be isolated on incubation in the dark using low enzyme concentrations at 25°C for 2 h. Protoplasts isolated in this way can support tobacco mosaic virus replication and are capable of cell division.
Foliar Penetration of Succinic Acid‐2,2‐dimethylhydrazide: Mechanism and Rate Limiting Step
Authors: SCHÖNHERR J. , BUKOVAC M. J.
Published: April 2006

The foliar penetration of succinic acid‐2,2‐dimethylhydrazide (SADH) into primary leaves of bean (Phaseolus vulgaris L. cv. Blue Lake) was studied using detached leaves and a leaf disc method. SADH penetration was linear with time and directly related to concentration and the fraction of non‐ionized SADH molecules in the treating solution. The addition of a surfactant, polyoxyethylene sorbitan monolaurate, increasing temperature and light enhanced penetration. Surfactant and light enhanced penetration are discussed in relation to increased wetting and area of contact over guard and accessory cells and the greater permeability of the cuticular ledges in open than in closed stomata. Evidence is presented that foliar penetration of SADH takes place by diffusion controlled by the cuticular membrane. Metabolic processes were not rate limiting.
Characterization of the Proteinases Present in Germinating Seeds of Scots Pine, Pinus sylvestris
Authors: SALMIA M. Aulikki , NYMAN SEIJA A. , MIKOLA JUHANI J.
Published: April 2006

Methods were developed to determine proteinase activity in germinating seeds of Scots pine. The assays were based on the liberation of TCA‐soluble peptides from haemoglobin at pH 3.7 and from casein at pH 5.4 and pH 7.0; the reaction products were determined by the Lowry method. — Endosperms separated from seeds at the time of rapid storage protein mobilization (seedling length between 20 and 50 mm) showed high proteinase activities in all three assays. Experiments with different inhibitors suggested that at least four enzymes were involved. One of the enzymes resembled mammalian and microbial pepsin‐like acid proteinases: the pH optimum was 3.7 and the enzyme was inhibited by pepstatin.—The proteinase activities in the endosperms were high enough to account for the mobilization of the reserve proteins during germination. Moreover the activities at pH 3.7.5.4. and 7.0 in the endosperms were 10‐, 25‐, and 50‐fold the corresponding activities in the growing seedlings (a “reference” tissue). Consequently, it seems that both the acid and neutral proteinases take part in the mobilization of storage proteins in the germinating seed.
Non‐histone Proteins Associated with Chromatin of Spirogyra during the Conjugation Process
Authors: SASAKI KIMIKO
Published: April 2006

Non‐histone proteins were isolated from purified chromatin of Spirogyra sp. at different stages of the life cycle. Conjugation‐ specific acidic proteins were separated by DEAE‐Sephadex A50 column chromatography. The protein fraction includes an inhibitor of chromatin‐directed RNA synthesis.
Effects of Water Stress and Hardening on the Internal Water Relations and Osmotic Constituents of Cotton Leaves
Authors: CUTLER J. M. , RAINS D. W.
Published: April 2006

Experiments were designed to test the hypothesis that the internal water relations of leaves are altered when cotton plants (Gossypium hirsutum L.‘Acala SJ‐2′) are conditioned by several cycles of water stress. Preliminary experiments suggested that plants so conditioned are less sensitive to water deficits and that the change might be partly explained by an accumulation of solutes or by structural alterations attendant on development under conditions of water stress.

Leaves of preconditioned plants maintained turgor to lower values of water potential than did leaves of well‐watered plants. Accompanying this change was a lower osmotic potential at any given leaf water content in preconditioned plants. Tissue analysis of several osmotically active solutes indicated that soluble sugars and malate accumulate to about the same levels (dry‐weight basis) in both conditioned and unconditioned plants exposed to stress. These accumulations could not account for the turgor change. Analysis of the data on relative water content indicated that the leaves of conditioned plants had less water per unit dry weight than did leaves of controls. This change accounts for a substantial fraction of the difference between the osmotic potential of conditioned and control plants. The results of a simple model suggest that structural changes may play a significant role in explaining differences in the responses of conditioned and control plants to water stress.
The Capacity of Various Detergents to Solubilize and Stabilize Protochlorophyll(ide) Holochrome
Authors: STUMMANN B. M.
Published: April 2006

Earlier work has shown that protochlorophyll(ide) holochrome is associated with the prolamellar body membranes in etioplasts of barley (Hordeum vulgare L.), and that this pigment‐protein complex can be extracted in a stable, photoactive form by the use of saponin. For future work it would be advantageous if saponin, a detergent mixture, could be replaced by a single, well‐characterized substance. The spectral characteristics of holochrome extracted with 10 ionic and nonionic detergents were compared to those of the holochrome extracted with saponin. Mulgofen BC‐840 and digitonin extracted significant amounts of photoactive protochlorophyll(ide) holochrome, but this activity was highly labile, and no adequate substitute for saponin was found. Thus the stabilizing and solubilizing function of saponin is not simply related to the general properties of detergents.
Multiphasic Uptake of Amino Acids by Barley Roots
Authors: SOLDAL TROND , NISSEN PER
Published: April 2006

Concentration‐dependence and other characteristics of uptake of 3H‐labeled l‐lysine, l‐methionine and l‐proline by excised roots of barley (Hordeum vulgare L.) were studied. Use of relatively short uptake and wash periods and low solute concentrations ensured good estimates of influx across the plasmalemma.

Uptake in the range of 10−7M– 6.3 × 10−3M can be precisely represented by four or five phases of single, multiphasic mechanisms. The mechanisms appear to be relatively specific as judged from the competition by unlabeled analogues. Structural requirements for interaction of a compound with the uptake site for methionine are given, as are the effects of analogues on the phase pattern for this amino acid. There is no indication of separate uptake and transition sites for methionine or lysine. i.e. phase transitions seem in this case to be caused by binding of molecule(s) to the uptake site.

Uptake, but not phase patterns, was highly pH‐dependent. The optima were pH 5 for lysine, pH 3–5 (a broad peak) for methionine and about pH 5.5 for proline. Uptake of the three amino acids was strongly inhibited by 2,4‐dinitrophenol. sulfhydryl reagents and deoxycholate.
The Effect of Potassium on Cotyledon Expansion Induced by Cytokinins
Authors: GREEN JEROME F. , MUIR ROBERT M.
Published: April 2006

Potassium has been found to enhance greatly the expansion response of cucumber cotyledons to cytokinins. A reduction of the response to kinetin is obtained with increasing age of the cotyledons. The lesser response is associated with lower levels of potassium remaining in the cotyledon. A high level of KCI in the incubation medium offsets the lower potassium content of the tissue and enables a much larger response to the cytokinins. At 40 mM KCI the response to kinetin is 4.2 times greater than in the absence of KCI. Calcium increases the effect of potassium on the response to kinetin. When incubated in 40 mM KCI and 10 mM CaCI2 with 10 mg/I 6‐benzylamino‐purine, the final weight of the cotyledons is 6.8 times the initial weight after just 4 days. This KCI‐CaCI2 combination is also found to promote chlorophyll synthesis in the usual cucumber cotyledon bioassay.
Growth Respiration of a Flood‐Tolerant and a Flood‐Intolerant Senecio Species: Correlation between Calculated and Experimental Values
Authors: LAMBERS HANS , STEINGRÖVER EVELIENE
Published: April 2006

Root growth respiration of Senecio aquaticus Hill (flood‐tolerant) and Senecio jacobaea L. (flood‐sensitive) was calculated, assuming different P: O ratios. The growth respiration values were calculated on the basis of the chemical composition of root and shoot dry matter, in combination with published data on the energy costs of biosynthetic and transport processes. The comparison between calculated and experimental values suggests a relatively low efficiency of ATP utilization in the roots of the flood‐tolerant species.

Root growth respiration of S. congestus (R.Br.)DC., which is also flood‐tolerant, and Plantago lanceolata L. were also determined. The data showed that not all the flood‐tolerant species investigated had high root growth respiration values.

An “overflow model’ is proposed to explain observed differences in root growth respiration between species.
The Effect of Cadmium on Net Photosynthesis, Transpiration, and Dark Respiration of Excised Silver Maple Leaves
Authors: LAMOREAUX ROBERT J. , CHANEY WILLIAM R.
Published: April 2006

Excised leaves of silver maple (Acer saccharinum L.) exposed to 0, 0.045, 0.090, or 0.180 mM Cd24 exhibited reduced net photosynthesis and transpiration, and increased dark respiration. Rates of net photosynthesis and transpiration diminished with time and were strongly correlated with solution concentration and tissue content of Cd24, Net photosynthesis and transpiration were reduced to 18 and 21%, respectively, of the untreated controls after 64 h. Dark respiration increased as much as 193% of the untreated controls but was poorly correlated with solution concentration or tissue content of Cd24, Diffusive resistances of leaves to carbon dioxide and water vapor transfer increased with both increasing Cd24 concentration and time. These findings are discussed in relation to stomatal function.
In vitro Protein Synthesis by Polyribosomes of Peach Flower Buds at Different Physiological Stages
Authors: TORRIGIANI P. , MARINO G. , BAGNI N.
Published: April 2006

The in vitro phenylalanine incorporation by polyribosomes of peach flower buds (Prunus persica Stokes) during dormancy, dormancy break and flowering was investigated. Protein synthesis was measured using as catalyst either calf liver soluble factors or the ribosomal supernatant from the peach flower buds in the presence or the absence of the synthetic mRNA, polyuridylic acid. In the presence of polyuridylic acid, the activity of protein synthesis of dormant ribosomes is the same as that of ribosomes during dormancy break and flowering. The absence of synthetic messenger did not cause a change in activity. The ribosomal supernatant of dormant buds, but not of flowering buds, reduces the phenylalanine incorporation by polyribosomes from buds harvested at dormancy break.
The Effect of Mercaptoethanol on the Activity of Enzymes of Nitrogen Metabolism in Leaves from Urtica dioica and Spinacia oleracea
Authors: WELANDER MARGARETA
Published: April 2006

The effect of mercaptoethanol at different concentrations on enzyme activity was investigated in leaves from Urtica dioica and Spinacia oleracea. The interference of mercaptoethanol with enzyme activity is dependent on the type of plant, the configuration of the enzyme and the concentration of mercaptoethanol. A stimulation of GDH (glutamate‐dehydrogenase) was obtained in both species, while inhibition of GOT (glutamate‐oxaloacetate transaminase) and GPT (glutamate‐pyruvate transaminase) was demonstrated in Spinacia. The stimulation of GOT and GPT activity in Urtica was probably due to inhibition of phenol oxidase. Conclusions concerning the effect of mercaptoethanol on NR (nitrate reductase) activity were difficult to draw, since mercaptoethanol itself reduced nitrite and interfered with NR determination in tests in vitro. In Urtica. no activity could be obtained at all with the in vitro method, probably because an inhibitor of NR was liberated during the extraction procedure, Activity of NR could however be obtained in both species when using the in vivo method. Addition of protective agents to the extraction medium has been supposed to influence the protein extractability. In conformity with this increasing amount of fresh matter to the same volume of extraction medium resulted in decreased protein extractability. This led to differences in enzyme activity when expressed on a fresh weight basis but the specific activity remained constant.
Rhythmic Behavior in Germination of Cocklebur Seeds
Authors: SATOH SHIGERU , ESASHI YOHJI
Published: April 2006

Non‐dormant, lower seeds of cocklebur (Xanthium pensylvanicum Wallr.) germinated with unimodal flush after 20 and 36 h from the start of water imbibition at 33 and 23°C, respectively. At 28°C, however, germination occurred bimodally, the time of each peak coinciding with that at 23 and 33°C. This type of germination behavior was induced even at 33°C, when the seeds were contacted with some osmotica. Further, the application of different osmotica at 28°C caused a rhythmic multimodal germination with a period of about 16 h. It was suggested that an endogenous rhythmicity may be involved in the control of cocklebur seed germination.
Control of Chlorophyll Degradation in Detached Leaves of Barley and Oat through Effect of Kinetin on Chlorophyllase Levels
Authors: SABATER B. , RODRGUEZ M.a T.
Published: April 2006

Chlorophyllase seems to be responsible for the degradation of chlorophyll during senescence of detached leaves of barley (Hordeum vulgare) and oat (Avena sativa). Treatment at temperatures higher than 40°C — which protects against chlorophyll loss — lowers the level of chlorophyllase. Kinetin treatment lowers the level of chlorophyllase in barley leaves and prevents its rise in oat leaves after their detachment. Synthesis of proteins in both cytoplasm and chloroplast seems to be required in order to maintain a high level of Chlorophyllase in barley leaves after detachment.
Physiology and Chemistry of Substances Accelerating Abscission in Senescent Petioles and Fruit Stalks
Authors: DÖRFFLING KARL , BÖTTGER MICHAEL , MARTIN DOROTHEA , SCHMIDT VOLKER , BOROWSKI DETLEF
Published: April 2006

Senescent petioles of Coleus rehneltianus Berger. Phaseolus vulgaris L. cv. Saxa. Acer pseudoplatanus L., and senescent fruit stalks of Malus domestica Borkh. cv. Golden Delicious contain at least three abscission accelerating substances, which were isolated by extraction with methanol or with water and by diffusion into agar. They were purified by thin‐layer chromatography and bioassayed in a special abscission test using Coleus explants. Two of these abscission accelerators could be conclusively identified by thin‐layer chromatography and by gas chromatography as abscisic acid and xanthoxin. The third substance, which has acidic properties and is less polar than abscisic acid, could not be identified. The concentration and the absolute amount of abscisic acid in Coleus petioles were found to decrease during their development, young petioles having the highest concentration. No evidence was found that the three abscission accelerators or synthetic abscisic acid and xanthoxin affect the production of ethylene in Caleus explatns. The results obtained do not support the hypothesis that senescent petioles contain a specific “senescence factor”, which stimulates abscission via ethylene production.
Effects of Frost Hardening and Dehardening on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris
Authors: MARTIN BJÖRN , MÅRTENSSON OLLE , ÖQUIST GUNNAR
Published: April 2006

Photosynthetic electron transport and low‐temperature fluorescence emission properties have been analyzed in isolated chloroplasts during the course of frost hardening and dehardening of Pinus silvestris L. Both the partial electron‐transport reactions (H2O DPIP and Asc./DPIP NADP) and the overall electron transport (H2O — NAPD) showed decreasing capacities during the course of hardening. Upon exposing the plants to −5°C and high irradiance a block in the electron‐transport chain between the two photosystems developed, whereas the partial reactions still showed activities. The decrease in activity of PSl was accompanied by a decrease in P700 content, as determined by light oxidation of P700, which indicates a correlation between the two changes.

Hardening also induced changes in the in vivo chlorophyll organization. During the course of hardening the fluorescence emission bands F692 and F726 decreased relative to F680. These changes were more pronounced if the plants were treated in high than in low irradiance. This suggests a greater destruction of the chlorophyll antennae in close association with the two photoreactions than in the so‐called light‐harvesting chlorophyll a/b antenna.

During dehardening basically the reverse of the changes observed during hardening occurred. The recovery of secondary needles was complete, whereas primary needles only partly recovered.
Reassessment of the in vivo Assay for Nitrate Reductase in Leaves
Authors: HEUER BRURIA , PLAUT Z.
Published: April 2006

The in vivo assay procedure for nitrate reductase and its dependence on the concentration of nitrate and other ions were examined. It was found that high ion concentrations led to an increased release of nitrite to the reaction media which could be interpreted as a stimulated nitrate reductase activity. This phenomenon is not an osmotic effect, since equivalent concentrations of mannitol did not lead to identical results. The effect of ions on the enhanced nitrite production was attributed to changes in cell membrane permeability rather than to a supply of substrate. This conclusion is based on several findings: (a) in in vitro assays, the rate of nitrite production was not affected by ion concentrations: (b) the stimulation of nitrite production was obtained by various ions and not only by nitrate; (c) pretreatment of alfalfa leaves with nitrate did not increase the NO2− release rate to the external solution; and (d) nitrate and nitrite export from leaf discs to the solution was stimulated even in discs which were enzymatically inactive. Calcium ions in the presence of KNO3 inhibited the enhanced nitrite production, probably due to alteration of membrane stability.

The effect of ions on the rate of nitrite production was reversible and the high rate of nitrite production was reduced to the control rate when discs were transferred to a solution of low concentration.
Oscillations in the Activities of Enzymes of Nitrate Reduction and Ammonia Assimilation in Glycine max and Zea mays
Authors: DUKE STANLEY H. , FRIEDRICH JAMES W. , SCHRADER LARRY E. , KOUKKARI WILLARD L.
Published: April 2006

The activities of glutamate dehydrogenase (GDH), glutamine synthetase (GS), and nitrate reductase (NR) and the levels of soluble protein and NO‐3 were assayed in soybean (Glycine max [L.] Merr.) leaves over a 48‐h period with the initial 24 h under a light‐dark cycle (LD 16:8) followed by 24 h of continuous light (LL). Plants had been entrained for 30 days under the LD regime. Maize (Zea mays) leaves (10 days old) under a LD 15:9 cycle were assayed only for NR and nitrite reductase (NiR). Data were subjected to frequency analysis by the least squares method to determine probabilities for cosine function periods (τ's) between 10 and 30 h. NR activities for both soybean and Zea leaves had 24 h τ's with P values < 0.05 indicating circadian periodicity. GDH in soybeans had a 24‐h rhythm under LD conditions which lengthened under LL conditions. The 24‐h rhythm of GDH displayed maximal activity toward the end of the dark period of the LD cycle whereas the highest activity of NR was early in the light period. Total soluble protein displayed a rhythm with a best fitting τ of greater than 24 h under both LD and LL. GDH, GS, NR, NO3, and soluble protein in soybeans and NiR in Zea, all displayed that were ultradian (10–18 h), indicating that a τ of about one half a circadian periodicity may be a common characteristic of the enzymes of primary nitrogen metabolism in higher plants. These data also demonstrate that although both NR and GDH are circadian in their activity, the 24‐h rhythm may be greatly influenced by ultradian oscillations in activity.
Influence of CO2 on Reduction of Nitrate in Corn Seedlings
Authors: STULEN INEKE , LANTING L.
Published: April 2006

The influence of CO2 on the assimilation of nitrate in intact corn seedlings was measured with 15N labelled nitrate, 24 and 48 h after the dark‐grown seedlings were transferred to the light, either in normal air or in CO2‐free air. During the first 24 h CO2 had no influence on nitrate reduction in intact seedlings. Experiments with detopped seedlings showed that during this period the roots were the only site of nitrate reduction. After 48 h seedlings grown in normal air had reduced more nitrate than detopped seedlings, and seedlings grown in CO2‐free air had reduced the same amount of nitrate as detopped seedlings. During the whole 48 h period CO2 had no influence on the level of nitrate reductase of the leaves. It was concluded that in normal air corn leaves started to reduce nitrate after a lag period of 24 h and that in CO2‐free air they were incapable of nitrate reduction.
Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels
Authors: NAIR T. V. R. , GROVER H. L. , ABROL Y. P.
Published: April 2006

Upper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.‐1) increased significantly due to soil N application (N30 over N0). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)‐1 revealed that two‐thirds of N is translocated by 28‐day stage and the rest between 28‐day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)‐1 at N0, N30 and N120‐ respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.
Degradation of Muskmelon Cell Wall by the Xylanases of Colletotrichum lagenarium
Authors: DOUX‐GAYAT A. , AURIOL P. , JOSELEAU J. P. , TOUZÉ A.
Published: April 2006

Xylose‐rich polysaccharide fractions were isolated from cell walls of muskmelon (Cucumis melo L. cv. Cantaloup Charentais) stems. A xylan with a (1 → 4) linked backbone has been characterized as a component of these fractions. Two xylanases excreted by the fungus pathogen Colletotrichum lagenarium were able to degrade this substrate both after extraction and when it was included in the crude cell walls. The results suggest that the xylanases are involved in the parasitism of this pathogen.
Optimum Conditions for Indoleacetic Acid Oxidase Extraction from Betula Leaves
Authors: HOYLE MERRILL C.
Published: April 2006

This report deals with total extraction and activation of soluble indoleacetic acid oxidase from Betula alleghaniensis leaves as affected by different buffers, varying pH, phenol binder, detergent, plus volume and time parameters. For all buffers and pH levels tested, only tris pH 8 gave a high activity. This result was not a pH effect, since a wide‐range, citrate‐phosphate buffer at pH 8 gave a very low activity. Addition of a neutral detergent, Triton X‐100, to all buffers gave considerable activity in every case. Most activity with Triton X‐100 occurred at pH 6 and least at pH 8 regardless of buffer composition. A phenol binder, polyvinylpyrollidone, increased activity also, but less than the detergent Triton X‐100. Both of these compounds in combination gave an additive effect and the highest measure of enzyme activity. Further increases in measurable indoleacetic acid oxidase activity were obtained by using the best combination of these factors to determine the optium tissue: buffer ratio and optimum soaking time. Increases in activity of 70 and 60%, respectively, were achieved.
Phycochrome d, a New Photochromic Pigment from the Blue‐Green Alga, Tolypothrix distorta
Authors: BJÖRN G. S.
Published: April 2006

A new reversibly photochromic pigment, phycochrome d, has been found in extracts of the blue‐green alga Tolypothrix distorta. This phycochrome exhibits an absorbance increase in the red region (maximum at about 650 nm) when irradiated with 650 nm light, and a corresponding absorbance decrease when irradiated with 610 nm light. The absorbance difference spectrum and action spectra for in vitro conversions were determined.
Adenosine 3′:5′‐Cyclic Monophosphate in Normal and Habituated Helianthus Callus
Authors: TRUELSEN T. A. , WYNDAELE RITA
Published: April 2006

A compound with properties identical to adenosine 3’:5′‐cyclic monophosphate (cAMP) has been isolated from callus of Helianthus annuus. The compound accompanied cAMP during an extensive purification procedure and co‐chromatographed with cAMP in three solvent systems. The compound stimulated cAMP‐dependent protein kinase and was active in a cAMP protein‐binding assay. Its activity was abolished by cAMP phosphodiesterase. It is concluded that the compound is cAMP.

The variation in cAMP content in the callus during its development was determined. In 1974 when the stock callus was grown on auxin‐containing medium the content was c. 2 pmol cAMP/g when the cells were vigorously dividing and c. 125 pmol cAMP/g two weeks after the transfer. In 1976 the callus had attained hormone autotrophy. Its cAMP content was generally low during the whole developmental cycle.

The results might indicate that cAMP played a role in the development of the normal callus of 1974, while it has no regulatory function in the tumour‐like tissues of 1976. The results are discussed on the basis of recent literature.
Variations dans ľexpression du pouvoir oncogène d'Agrobacterium tumefaciens
Authors: Le Goff L. , MANIGAULT P.
Published: April 2006

Variations in the expression of the oncogenic power of Agrobacterium tumefaciens due to interactions between bacteria.

The effects of the virulent strain A6 of Agrobacterium tumefaciens after co‐culture with non‐virulent variants of the same bacterium, or even with other bacterial species (e.g. Escherichia coli), showed that interactions between different strains of bacteria exist. These interactions are expressed as a phenomenon of either enhancement or inhibition, as shown by an increase or a decrease in the weights of tumors induced in decapitated stems of Pisum sativum L. cv. Annonay. These two phenomena depend on the contact time between the bacteria in mixed cultures (type I). With a short contact time between the two bacterial types (one or two generations), infections in decapitated pea stems produced by mixed inocula caused an increase in tumor weight compared with infections induced by inocula of virulent bacteria only. If the contact time was increased to the end of the log phase, a decrease in tumor weight was observed. Clarified supernatant fluids of spent media were also used as culture media (type II) for the virulent A6 bacteria. The stimulatory or inhibitory activity of (a) substance(s) present in these supernatant fluids depended on two variables: culture time of the bacteria A6 in the supernatant fluids and the “age” of the bacterial culture used to prepare them. Weight increase of the tumors was obtained if the proliferating time of the A6 bacteria in the supernatant fluids was short (4 h), or if the super natants were obtained from “young” cultures. Inhibition of the tumor expression occurred if the contact time of A6 bacteria in the supernatant fluids was increased or if the supernatants originated from bacterial cultures at the end of their growth. The in vitro interactions between the two bacterial strains in a mixed culture (type I or type II) were suppressed in the presence of pancreatic ribonuclease. Deoxyribonuclease had no effect. This provides indirect evidence for the action of a ribonucleic acid in the expression of the oncogenic power of a bacterial population of Agrobacterium tumefaciens.
Gibberellins and Inhibitors in Leaves of Tall and Dwarf Beans
Authors: GOTÔ NOBUHARU
Published: April 2006

The contents of GAs and growth inhibitors were investigated in the dwarf (cv. Masterpiece) and tall (cv. Kentucky Wonder) varieties of bean (Phaseolus vulgaris L.). The comparison of active substances was carried out by parallel extraction and fractionation from leaves of the two varieties followed by paper chromatography, thin layer chromatography (TLC) and bioassay, using lettuce hypocotyl growth test. Five GA‐like activities and six growth‐inhabiting activities, in which xanthoxin. ABA and bound ABA might be included, were detected in both dwarf and tall varieties. The levels of all of these GAs and inhibitors were almost identical between the two varieties. In both varieties GA3 treatment caused two inhibitory activities to decrease. The expression of dwarfism in the vegetative growth stages of beans may have to be discussed also on the basis of another factor than that of the levels of endogenous GA inhibitors.
The Influence of Colchicine on Initiation and Early Development of Adventitious Roots
Authors: OPPENOORTH J. M.
Published: April 2006

The first sign of adventitious root formation in the petiole of the primary leaves of Phaseolus vulgaris after treatment with IAA was the dedifferentiation of mature parenchyma cells next to strands of sieve elements and companion cells. Colchicine strongly inhibited this dedifferentiation. Treatment with colchicine 3 days after treatment with IAA, caused the groups of meristematic cells formed to grow by cell enlargement only. Groups of more than about 30 meristematic cells changed into recognizable root primordia during this growth. Groups with a smaller number of meristematic cells extended also in size but did not form a recognizable root primordium.
Oscillatory Transpiration and Water Uptake of Avena Plants
Authors: KLOCKARE RUNE , JOHNSSON A. , BROGÅRDH T. , HELLGREN M.
Published: April 2006

The transpiration rate of oat plants, 6 days old, has been investigated. Dependent on the irradiance level of the white light used in the experiments, the transpiration rate oscillated with different period times. In darkness or at low irradiances the period was about 100–110 min. At higher irradiances the period was about 40 min. At intermediate irradiances autocorrelation analysis was used to find the period content of the transpiration rate. It was concluded that two oscillatory systems were present in the plants, characterized by their different periods.

When plants cultivated in a light/dark cycle were used, the transpiration oscillations were influenced by a circadian rhythm. Oscillations in darkness were then most pronounced in the mornings. Plants cultivated in continuous light did not show such a circadian rhythm, but the oscillations died out after about 20 h.

Kinetin induced transpiration oscillations in darkness and made them sustain for a longer time.
Thermodormancy in Celery Seeds and its Removal by Cytokinins and Gibberellins
Authors: BIDDINGTON N. L. , THOMAS T. H.
Published: April 2006

Imbibition of celery (Apium graveolens L.) seeds at 32°C for up to 96 h lowered the upper temperature limit for germination. If this high temperature treatment was given in the light, these seeds germinated slightly earlier than those treated in the dark although the final percentage germination was similar for both treatments. The inhibitory effect of the high temperature treatment was completely removed by allowing the seeds to imbibe in a mixture of the gibberellins A4 and A7 (GA4/7) and partially removed by the cytokinin N6‐benzylaminopurine (BA). GA4/7 was less effective when added before rather than after the high temperature treatment, whereas the opposite was true of BA. At constant temperatures more GA4/7 was required to promote germination as the temperature was raised but addition of BA reduced the concentration of GA4/7 required. A model is proposed for the control of celery seed germination by light and temperature through the action of endogenous cytokinins and gibberellins.
Movement of Cell Organelles and the Geotropic Curvature in Roots of Norway Spruce (Picea abies)
Authors: HESTNES ARNOLD , IVERSEN TOR‐HENNING
Published: April 2006

The geotropic development in roots of Norway spruce [(Picea abies (L.)] H. Karst, has been followed by light and electron microscopy and compared with the movement of cell organelles (statoliths) in the root cap cells. The geotropic curvature develops in two phases: (a) an initial curvature in the root cap region, which results in an asymmetry in the extreme root tip and which appears after about 3 h stimulation in the horizontal position; and (b) the geotropic curvature in the basal parts of the root tip, which after 8 h is distributed over the entire elongation zone. A graphic extrapolation, based on measurements of the root curvatures after various stimulation periods, indicates a presentation time in the range of 8 to 10 min.

The root anatomy and ultrastructure have been examined in detail in order to obtain information as to which organelles may act as gravity receptors. The root cap consists of a central core (columella) distinct from the peripheral part. The core contains three to four rows of parenchymatic cells each consisting of 15 to 18 storeys of statocyte cells with possibly mobile cell organelles. Amyloplasts and nuclei have been found to be mobile in the root cap cells, and the movement of both types of organelles has been followed after inversion of the seedlings and stimulation in the horizontal position for various periods of time at 4°C and 21°C. Three‐dimensional reconstructions of spruce root cap cells based on serial sectioning and electron microscopy have been performed. These demonstrate that the endoplasmic reticulum (ER)‐system and the vacuoles occupy a considerable part of the statocyte cell. For this reason the space available for free movement of single statolith particles is highly restricted.
Changes in the Activity of Acetyl CoA Carboxylase in Germinating and Ripening Sunflower Seeds
Authors: BHATIA I. S. , AHUJA K. L. , SUKHIJA P. S.
Published: April 2006

Activity of acetyl CoA carboxylase was determined in germinating and maturing sunflower (Helianthus annuus L.) cv. Rum Sun Record seeds. A constant decrease was observed in germi nating embryos. Exposure of etioplasts to light intensity of 500 (74 mW . cm−2) lux for different time intervals decreased the activity of the enzyme in the embryos. A reverse trend was observed in ripening embryos where the ATP‐Pi exchange rate was found to be directly correlated to the activity of acetyl CoA carboxylase.
The Influence of Ambient Nitrate, Temperature, and Light on Nitrate Assimilation in Sudangrass Seedlings
Authors: HALLMARK W. B. , HUFFAKER R. C.
Published: April 2006

Seedlings of Sundangrass (Sorghum Sudanese [Piper] Stapf.) were grown 10 to 13 days of age in a nutrient solution containing nitrate and then placed under treatment conditions for 24 h before assays of nitrate assimilation were begun. Nitrate uptake was determined by its disappearance from the ambient solution. In vivo reduction of nitrate was determined by the overall balance between the amount taken up and the change in tissue concentration of nitrate during the experiments. Nitrate reductase activity was determined from tissue slices. In vivo reduction was strongly regulated by uptake in response to time and ambient nitrate concentration, temperature and light. Nitrate reduction responded to the concentration of nitrate supplied by uptake and by a storage pool, since reduction often exceeded uptake. Nitrate reductase activity in tissue slices was exponential in initial response to increasing temperature. After a 24‐h equilibration period at each temperature, the activity was lower at higher temperatures. In contrast, actual reduction of nitrate increased linearly with increasing temperature between 15 and 24°C in the plants equilibrated 24 h at each temperature. Nitrate uptake and reduction were greatly inhibited under low light conditions, with reduction inhibited more than uptake., The effect of ambient nitrate, temperature, and light on the nitrate assimilatory processes help to explain observations reported on nitrate accumulation by Sudangrass forage.
Influence of Exogenous Fatty Acids on Cottonseed Germination
Authors: BARTKOWSKI EDMUND J. , KATTERMAN FRANK R. H. , BUXTON DWAYNE R.
Published: April 2006

Effects of exogenous free fatty acid application on percentage germination and radicle length were investigated with more chill sensitive (Pima S‐4) and less chill sensitive (Pima S‐5) cottonseed (Gossypium barbadense L.) at chilling (14°C) and optimal (34°C) temperatures. Of the organic solvents able to solubilize free fatty acids, aqueous solutions as high as 5% dimethyl sulfoxide did not adversely affect germination at 34°C. Palmitic, oleic and linoleic acids (120 μM) were solubilized in 5% DMSO.

At 14°C, percent germination of fatty acid treated Pima S‐5 significantly increased, while no difference was observed for Pima S‐4. Conversely, radicle length of fatty acid treated Pima S‐4 significantly increased especially with oleate and linoleate, while no difference was detected for Pima S‐5. Fatty acid supplementation influenced neither germination nor radicle length for Pima S‐4 and Pima S‐5 at 34°C.
Formation of Cytokinin Nucleotides in a Detached Inflorescence Stalk and the Occurrence of Nucleotides in Phloem Exudates from Attached Yucca Plants
Authors: VONK C. R.
Published: April 2006

The metabolism of isopentenyl adenine, Δ‐isopentenyl pyrophosphate, DL‐mevalonic acid and adenine in detached inflorescence stalks of Yucca has been studied using radioactive tracer techniques.

Xylem feeding of detached stalks with Δ‐isopentenyl pyrophosphate, DL‐mevalonic acid or adenine did not result in the formation of zeatin‐ or isopentenyl adenine cytokinins.

In contrast isopentenyl adenine fed to a detached inflorescence stalk lead to the formation of isopentenyl‐ and zeatin nucleotides in the exudate. After alkaline phosphatase treatment of this exudate an unknown compound, presumably isopentenyl adenine‐7‐glucoside was also detected. The same compound was found after incubation of phloem exudate with isopentenyl adenine.

The occurrence of both zeatin‐ and isopentenyl adenine nucleotides in phloem exudate from an attached inflorescence stalk of Yucca is described.
Effect of Salinity on the Activities of RNase, DNase and Protease during Germination and Early Seedling Growth of Mung Bean
Authors: SHEORAN I. S. , GARG O. P.
Published: April 2006

Seeds and seedlings of mung bean (Phaseolus aureus Roxb.) were treated separately with NaCl, KCl, Na2SO4 and K2SO4 solutions of 5 and 10 S/cm conducitivity. The activity of RNase, DNase and protease were estimated in cotyledons, embryo axis, leaves, and roots. Salinity caused inhibition of RNase activity in the cotyledons and roots, but increase in embryo axis and leaves. Activity of DNase was also increased; sodium salt was more effective than potassium irrespective of associated anion. Salinity in general either reduced or had no effect on protease activity in all organs, with the exception of NaCl which doubled it in leaves.
Polarity of Xylem Formation in Isolated Stem Segments of Pinus silvestris
Authors: ZAJĄCZKOWSKI STEFAN , ROMBERGER J. A.
Published: April 2006

The culture of isolated stem sogments was used as a technique to study polarity of xylem formation in Pinus silvestris L. Cambial activity was greatest at the apical or the basal end, whichever received the complete fresh medium, but decreased more abruptly with increasing distance when the basal end was so supplied. Whether gradients of activity increased basipetally or acropetally also depended upon the end to which the auxin and the sugar components were supplied. Ring‐barking of segments, then cultur‐ing them with apical supply of medium to the xylem, resulted in inhibition of xylem production below, and above, the ring. Cambial activity at the apical ends of such segments was expressible as a logarithmic function of the uninterrupted length of contiguous extraxylary tissues. The involvement of polarity phenomena in control of cambial activity in isolated stem segments is confirmed.
Seasonal Effects on Chlorophyll‐Protein Complexes Isolated from P‐inus silvestris
Authors: ÖQUIST GUNNAR , MÅRTENSSON OLLE , MARTIN BJÖRN , MALMBERG GUNILLA
Published: April 2006

The seasonal changes in the relative distribution of P700 chlorophyll‐protein complex a1 and light harvesting chlorophyll‐protein complex a/b were studied in a natural stand of Pinus silvestris. Similar measurements were made after artificial photobleaching of chlorophyll in pine seedlings or in isolated pine chloroplasts. The chlorophyll‐protein complexes were solubilized by sodium dodecyl sulphate and separated by polyacrylamide gel electrophoresis. When autumn and winter destruction of chlorophyll occurs, the chlorophyll a antenna associated with P700 in photosystem 1 (P700‐CPa1) is relatively more affected than the light harvesting complex, which lacks a reaction centre. These results are further supported by low‐temperature fluorescence emission properties of isolated chloroplasts presented in this work and elsewhere. The destruction of chlorophyll in stressing autumn and winter climates is most probably caused by photosensitized oxidation of chlorophyll.
Daily Patterns under the Life Cycle of a Maize Crop
Authors: ANDRÉ M. , MASSIMINO D. , DAGUENET A. , RICHAUD C. , VIVOLI J.
Published: April 2006

Together with photosynthesis, transpiration and respiration, the daily uptake of NO3−, NH4+, H2PO4−, K+, Ca2+, Mg2+, SO42−, the root respiration, root volume increase and root excretions have been studied by daily measurements during the growth period of whole maize plants (Zea mays L. cv. INRA F7 × F2) raised until complete maturity on nutrient solution. The uptake patterns show a maximum absorption of NO3−, K+ and Ca2+ during the vegetative growth phase. The absorption of these ions declines during maturation while that of H2PO4− reaches a maximum. Root respiration and particularly the uptake of NO3− and K+ are well correlated with the rate of root growth. Root excretion is more notable in young plants than in the old. It represents less than 0.2% of the net assimilation of adult plants.
Morphology and Physiology of Lyngbya nigra with Reference to Copper Toxicity
Authors: GUPTA A. B. , ARORA ASHA
Published: April 2006

The effect of copper sulphate on morphology and physiology of Lyngbya nigra has been studied. The growth was inhibited in all treatments (0.4 to 80.0 μM) of copper sulphate. There were no apparent morphological changes up to 0.8 μM and during the first two days of treatment even in the higher concentrations of copper sulphate.

In concentrations above 0.8 μM the first symptom of toxicity was the formation of separation discs in large numbers. The trichomes contracted longitudinally and the cells became swollen and constricted at the cross walls. The cells also became yellowish due to loss of photosynthetic pigments. Finally, in 4 μM and above, vacuoles appeared in large number indicating the moribund state of the cells.

Copper sulphate increased respiration at 2 μM, and optimum effect was observed in 8 μM after 96 h. Inhibition of photosynthesis was detectable in 0.8 μM, and 100% inhibition took place in 8 μM after 96 h. In higher concentrations the effect was immediate, and a conspicuous inhibition of photosynthesis could be observed within 10 min.

The copper content of the alga increased with increased concentration of copper sulphate while potassium content decreased. With rise in outside concentrations of copper, there was a comparatively great increase of absorption in 2 and 4 μM, while further increases were gradually less. The observations indicate that changes in the physiological activity of the alga under treatment are closely interlinked with marked changes in morphology.
Lipid Properties of Carex aquatilis from Hot Spring and Permafrost‐Dominated Sites in Alaska: Implications for Nutrient Requirements
Authors: KEDROWSKI RICHARD A. , CHAPIN F. STUART
Published: April 2006

Selected lipid properties were compared between populations of Carex aquatilis occupying adjacent hot spring and permafrost‐dominated sites in interior Alaska. Analyses were carried out on a variety of plant parts and results correlated with prevailing ambient temperature. Phospholipid concentrations were higher in plants from permafrost than from hot spring areas, even though there was no consistent interpopulation difference in total lipid content. The population differences in phospholipid content were greatest in those plant parts that experienced the greatest interpopulation temperature difference. Despite lower soil phosphorus availability, permafrost plants had higher total phosphorus concentrations, and a larger proportion of their phosphorus was contained in phospholipid than in hot spring plants. There was no consistent relationship between the proportion of various classes of phospholipids present and prevailing ambient temperature. Fatty acid chain length and degree of unsaturation of the phospholipid fraction were inversely correlated with temperature both between populations and among plant parts. No such relationship was found in the fraction containing neutral lipids. We suggest that the high tissue phosphorus content that characterizes northern plants may be necessary in part to maintain large quantities of phospholipid‐containing membrane. Increased amounts of membrane in turn may be a prerequisite for the high rates of membrane‐associated processes characteristic of plants in the cold subarctic environment.