bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipid synthesis in callus and protoplasts during culture: Analysis of dividing protoplasts of Petunia hybrida and non‐dividing protoplasts of Parthenocissus tricuspidata
Authors: Zuily‐Fodil Y. , Teodorescu‐Ionescu N. , Passaquet C. , Pham Thi A. T.
Published: May 2006

The purpose of the investigation was to study the process, by which protoplasts derived from callus tissue overcome the hydrolysis of membrane phospholipids, which is induced by the isolation. Dividing protoplasts from Petunia hybrida L. (line SFla) and non‐dividing protoplasts from Parthenocissus tricurpidara L. crown gall (Morel strain) were fed with sodium [1‐14C]‐acetate for 1 h. The incorporation was carried out at protoplast isolation and after 1, 2, 4 and 7 days of culture. The rates of fatty acid and lipid synthesis were then followed. Isolation stress induced diversions in the utilization of the precursor via triacylglycerol (Petuunia) or diacylglycerol (Partheno‐cissus) and a decrease in the synthesis of oleic acid (Parrhenocissus). During the first 2 days of culture, the rate of phospholipid synthesis was similar in both systems. Later on, an increase in the rate and in the efficiency of phospholipid synthesis was observed in dividing Petunia protoplasts. The accelerated rate of lipid synthesis allowed them to recover the same partitioning and content in membrane phospholipids as the reference cells in the callus. This process seemed to bc related to cell division, since it was not observed in the non‐dividing protoplasts of Parthenocissus.
Cytosolic and particulate phosphatidylinositol phospholipase C activities in pollen tubes of Lilium longiflorum
Authors: Helsper J. P. F. G. , Heemskerk J. W. M. , Veerkamp J. H.
Published: May 2006

Pollen tubes of Lilium longiflorum Thunb. cv. White Europe contain three distinguishable phosphatidylinositol phospholipase C activities (EC 3.1.4.10). Two of these are particulate and have optima at pH 5.2 and 7.0, respectively. The third one, a cytosolic activity, has an optimum at pH 6.0. The distribution of radioactivity in reaction products from phosphatidylinositol, labeled in either the inositol, glycerol or phosphate moiety, indicates that the three phospholipase activities cleave only the bond between glycerol and phosphate. The dependence on divalent cations slightly differs, though Ca2+ is the most stimulatory ion species for all the three enzyme activities. Activity is not observed in the presence of EDTA. When anionic phospholipids are mixed with phosphatidylinositol substrate an increase in phosphatidylinositol phospholipase C activities is observed, except for the particulate activity with an optimum at pH 5.2. Phosphatidylcholine and phosphatidylethanolamine are inhibitory.
Effects of water deficit on photosynthetic capacity
Authors: Kaiser Werner M.
Published: May 2006

Under drought, CO2 assimilation rates decrease already at small leaf water deficits. At least part of the inhibition is attributed to non‐stomata1 effects at the chloroplast level, with electron transport and phosphorylation being main targets of inhibition. These findings are questioned by direct measurements of photosynthetic capacity with systems that are not Limited by stomata, e.g. leaf slices in solution or leaves at ex‐ternal CO2 concentrations exceeding 5%. Here, photosynthesis was rather insensitive to dehydration down to 50–70% relative water content, and different plant species re‐sponded in a very similar way. More severe dehydration affected not only pboto‐synthesis, but also dark CO2 fixation and presumably also photorespiration. Rever‐sible and unspecific inhibition is thought to be mediated mainly by increased concen‐trations of solutes in dehydrated cells. Inhibition of photorespiration might favour photoinhibition when long‐term water stress is coupled with full sunlight. Photo‐inhibition, together with general senescence phenomena might be involved in long‐term effects of water stress under natural drought conditions. This offers an explanation for the conflicting results of short‐term water stress experiments and studies carried out under field conditions.
Drought‐induced shifts in daily CO2 uptake patterns for leafy cacti
Authors: Nobel Park S. , Hartsock Terry L.
Published: May 2006

For cacti with persistent, relatively large leaves, most shoot CO2 uptake under well‐watered conditions occurs by the leaves using the C3 pathway. For three species in the primitive subfamily Pereskioideae, droughts of 7 or 14 days decreased leaf daytime net CO2 uptake by an average of 49 and 88%, respectively; these species always had a net CO2 release at night by the leaves and both at night and during the day by the stems. For three leafy species in subfamily Opuntioideae, 7 and 14 days of drought reduced leaf daytime net CO2 uptake by 90 and 100%, respectively. Although drought reduced the total CO2 uptake over 24 h, the average percentage occurring at night by the leaves of these species increased from 5% under wet conditions to 71% after 7 days of drought to 99% after 14 days of drought. For two of the three species of Opuntioideae, 7 days of drought caused the small net CO2 uptake by the sterns to shift from the daytime to the nighttime, while for the third species drought caused a reduction of its stem nocturnal net CO2 uptake. Thus, shifts from predominantly daytime to predominantly nighttime net CO2 uptake can be induced by drought for the leaves and the stems of leafy cacti in subfamily Opuntioideae, indicating a high degree of biochemical versatility.
Graviperception of lentil seedling roots grown in space (Spacelab Dl Mission)
Authors: Perbal Gérald , Driss‐Ecole Dominique , Rutin Jacques , Sallé Georges
Published: May 2006

The growth and graviresponsiveness of roots were investigated in lentil seedlings (Lens culinaris L. cv. Verte du Puy) grown (1) in microgravity, (2) on a 1 g centrifuge in space, (3) in microgravity and then placed on the 1 g centrifuge for 3 h, (4) on the ground. Dry seeds were hydrated in space (except for the ground control) and incubated for 25 h at 22°C in darkness. At the end of the experiment, the seedlings were photographed and fixed in glutaraldehyde in a Biorack glove box. Root length was similar for seedlings grown in space and for the ground and the 1 g centrifuge controls. The direction of root growth in the microgravity sample deviated strongly from the initial orientation of the roots of the dry seeds. This deviation could be due to spontaneous curvatures similar to those observed on clinostats. When lentil seedlings were first grown in microgravity for 25 h and then placed on the 1 g centrifuge for 3 h, their roots bent strongly under the effect of the centrifugal acceleration. The amplitude of root curvature on the centrifuge was not significantly different from that observed on ground controls growing in the vertical position and placed in the horizontal position for 3 h. The gravisensitivity of statocytes differentiated in microgravity was similar to that of statocytes differentiated on earth. There were no qualitative differences in the ultrastructural features of the gravisensing cells in microgravity and in the 1 g centrifuge and ground controls. However, the distribution of statoliths in the gravisensing cells was different in microgravity: most of them were observed in the proximal part of these cells. Thus, these organelles were not distributed at random, which is in contradiction with results obtained with clinostats. The distal complex of endoplasmic reticulum in the statocytes was not in contact with the amyloplasts. Contact and pressure of amyloplasts on the tubules were not prerequisites for gravisensing. The results obtained are not in agreement with the hypothesis that the distal endoplasmic reticulum would be the transducer of the action of the statoliths.
Transport‐related amino acid metabolism in germinating barley grains
Authors: Saarelainen Ritva , Mikola Juhani
Published: May 2006

When eight [14C]‐labelled amino acids were separately injected into the endosperm of germinating (4 days at 20°C) barley (Hordeum vulgare L. cv. Himalaya) grains, the label was rapidly taken up by the scutellum and further transported to the shoot and roots. Some of the amino acids (leucine, lysine and asparagine) were transported in an intact form through the scutellum to the seedling, whilst glutamic acid and aspartic acid were largely converted to glutamine in the scutellum. Proline was mainly transported unchanged, but a small part of the label appeared in glutamine. Arginine was mostly broken down in the scutellum, possibly providing ammonia for the synthesis of glutamine. During further transport in the seedling there was a partial transfer of label from glutamine to asparagine, particularly in the shoot. None of the amino acids used supplied carbon for the synthesis of sucrose, glucose or fructose. Glutamine synthetase activity was particularly high in the scutellum during the period of rapid amino acid transport.
An endogenous circadian rhythm of transpiration in Tamarix aphylla
Authors: Hagemeyer Jügen , Waisel Yoav
Published: May 2006

An endogenous circadian rhythm in the transpiration of Tamarix aphylla (L.) Karst. was found for plants grown in continuous light under laboratory conditions. The mean period (±SD) was 21.7±2.3 h (n = 121). No such rhythm was observed in continuous darkness, except for one small hump at the time of the first cycle. The influence of NaCl, Cd(NO3)2 and LiCi on the rhythmic behaviour of young T. aphylla plants was investigated. NaCl concentrations of up to 150 mM reduced the overall transpiration rates of the plants, but did not change the period of the rhythm. The amplitude and the mesor of the oscillations were inversely correlated with the NaCl concentration. A similar influence was found for Cd(NO3)2, but with concentrations that were approximately three orders of magnitude smaller than those of the NaCl treatments. The rhythmic behaviour of the plants was not altered by 10 mM LiCl. It is suggested that the described rhythm of transpiration may have a dual effect: (a) it might cause a partial closure of the stomates during midday hours and (b) it might serve as a possible synchronizer (“master clock”) for other rhythmic phenomena in the plants.
Non‐transportable radioactivity in hypocotyls of Helianthus annuus after application of [3H]–IAA: Analysis of diffusion parameters
Authors: Hasenstein Karl‐Heinz
Published: May 2006

IAA was applied as a droplet to the apical cut surface of hypocotyl sections of Helianthus annuus L. After collecting auxin moving in the polar transport stream, the distribution of radioactivity remaining within the tissue was kinetically investigated. By use of regression functions of the type y = a exp(‐bx2) it was demonstrated that two independent diffusion profiles characterize the distribution of the residual radioactivity. An estimate of diffusion coefficients as well as amounts of each of the two components allowed conclusions concerning their molecular size and possibly their role in auxin transport. The results suggest that auxin and auxin metabolites are leaving the tissue by diffusion rather than by the activities of different transport systems. These results are discussed in respect to earlier descriptions of multiple auxin transport systems. H is concluded that a single transport system is sufficient to account for biphasic elution curves.
Correction for non‐specific interference in competitive immunoassays
Authors: Jones Hamlyn G.
Published: May 2006

Methods for correcting for non‐specific interference in immunoassays are outlined. Two main correction methods are evaluated: i) The use of antibodies to non‐naturally occurring substances, ii) curve‐fitting approaches. Curve‐fitting is based on the assumption of non‐competitive kinetics where only the maximum binding of label is affected, with no significant effect on the shape of the response curve. The latter assumption is evaluated using a simple mass‐action model, and shown to be adequate for many assays of the plant growth regulator, abscisic acid. A non‐linear curvefitting approach is presented and is shown to have wide applicability to all immunoassays beyond its use in correcting for interference. All correction methods have reduced sensitivity and require additional data compared with direct estimation of antigen. Nevertheless the additional measurements, which involve the assay of each sample with a range of added spikes of unlabelled antigen, should be routinely included in assays in order to test for interference.
Endogenous light‐dependent rhythm of zonation in Penicillium claviforme
Authors: Jerebzoff Stephan , Piskorz‐Binczycka Bernadetta
Published: May 2006

In darkness, sporalation of Penicillium claviforme Bainier CBS strain 126–23 was uniform. A single 10 J m−2 blue light pulse (in the range 360 to 520 nm) was sufficient to elicit an endogenous zonation rhythm (coremia formation); the higher the fluence, the longer the rhythm expression. The period was 30 to 36 h as long as sufficient fluence rate (3 μW m−2 for broad band blue light and 18.1 nmol m−2 s−1 for wavelengths 433, 457 or 465 nm) was continuously maintained; this rhythm became desynchronized in about a week. The period increased rapidly and reached 72 to 120 h as soon as the fluence rate was too low or dark was established. The 445,479 and 495 nm radiations evoked the rhythm in pulse experiments, whereas the rhythm was immediately desynchronized in continuous light. The participation of two photosensitive reactions in the rhythm regulation of P. claviforme is postulated.
Effect of high and low sulfate concentrations on adenosine 5′‐phosphosulfate sulfotransferase activity from Lemna minor
Authors: Brunold Christian , Suter Marianne , Lavanchy Pierre
Published: May 2006

The effect of Na2SO4 concentrations from 0 to 17.6 mM in the nutrient solution of Lemna minor L. strain 6580 on adenosine 5′‐phosphosulfate sulfotransferase activity was examined. Routinely, the plants were cultivated on 0.88 mA SO42−. The enzyme activity was increased by 50 to 100% after transfer to 0 or 0.0088 mM SO42−. Transfer back to 0.88 mM rapidly decreased the enzyme activity to the initial level. Cultivation on 17.6 mM Na2SO4 redueed extractable adenosine 5′‐phosphosulfate sulfotransferase by 50%. The original level was rapidly re‐established on 0,88 mM. In control experiments, a decrease in adenosine 5′‐phosphosulfate sulfotransferase activity was also induced by K2 SO4, whereas NaCl caused a small increase. This indicates that the observed effects are dependent on the sulfate ion. ATP‐sulfurylase activity measured for comparison was only significantly affected by the omission of sulfate, which induced a 20% increase, indicating that this enzyme activity from Lemna minor is less suseeptible to changes in medium sulfate than adenosine 5′‐phosphosulfate sulfotransferase. A close relationship between adenosine 5′‐phosphosulfate sulfotransferase activity and the content of asparagine, glutamine, non‐protein thiols and sulfate in the tissue was detected, indicating a positive control mechanism induced by amides and a negative mechanism induced by thiols and sulfate.
Rose leaf elasticity changes in response to mycorrhizal colonization and drought acclimation
Authors: Augé R. M. , Schekel K. A. , Wample R. L.
Published: May 2006

Tissue elasticity can affect plant response to drought, in terms of turgor maintenance and water uptake from drying soils. The purpose of this study was to determine the effect of mycorrhizal colonization and drought acclimation on rose (Rosa hybrida L. cv. Samantha) leaf elasticity. Bulk elasticity was characterized by the pressurevolume method using plots of the elastic modulus as a function of leaf turgor pressure, total water potential and relative water content. The treatments, arranged in a 2 × 3 factorial design, included acclimated and unacclimated plants, and either Glomus irararadices Schenck and Smith, Glomus deserticola Trappe, Bloss and Menge, or a non‐mycorrhizal control. Plants with root mycorrhizal colonization showed reduced leaf elasticity (i.e. higher elastic moduli) over a broad range of leaf waler potential and water content. Both mycorrbizal colonization and acclimation facilitated the maintenance of positive values of turgor and elasticity at lower leaf water potential and water content than in controls. Mycorrhizal infections may aid plants in acclimating to water deficits through effects on leaf tissue elasticity.
The effect of different growth conditions on dark and light carbon assimilation in Littorella uniflora
Authors: Madsen Tom Vindbæk
Published: May 2006

The effect of long‐term exposure to different inorganic carbon, nutrient and light regimes on CAM activity and photosynthetic performance in the submerged aquatic plant, Littorella uniflora (L.) Aschers was investigated. The potential CAM activity of Littorella was highly plastic and was reduced upon exposure to low light intensities (43 μmol m−2 s−1), high CO2 concentrations (5.5 mM, pH 6.0) or low levels of inorganic nutrients, which caused a 25–80% decline in the potential maximum CAM activity relative to the activity in the control experiments (light: 450 μmol m−2 s−1; free CO2: 1.5 mM). The CAM activity was regulated more by light than by CO2, while nutrient levels only affected the activity to a minor extent. The minor effect of low nutrient regimes may be due to a general adaptation of isoetid species to low nutrient levels.

The photosynthetic capacity and CO2 affinity was unaffected or increased by exposure to low CO2, irrespective of nutrient levels. High CO2, low nutrient and low light, however, reduced the capacity by 22–40% and the CO2 affinity by 35‐45%, relative to control.

The parallel effect of growth conditions on CAM activity and photosynthetic performance of Littorella suggest that light and dark carbon assimilation are interrelated and constitute an integrated part of the carbon assimilation physiology of the plant. The results are consistent with the hypothesis that CAM is a carbon‐conserving mechanism in certain aquatic plants. The investment in the CAM enzyme system is beneficial to the plants during growth at high light and low CO2 conditions.
The composition and function of thylakoid membranes from pea plants grown under white or green light with or without far‐red light
Authors: Chow W. S. , Haehnel W. , Anderson Jan M.
Published: May 2006

Pea plants (Pisum sativum L. ev. Greenfeast) were grown for 2 to 3 weeks in while (˜ 50 μmol photons m−2 s−1; 400–700 nm) or green (˜ 30 μmol photons m−2 s −1 400–700 nm) light (16 h day/8 h night), with or without far‐red light. Supplementary far‐red light decreased leaf area and increased internodal length in both white and green light, demonstrating that phytochrome influenced leaf size and plant growth. However, there was no effect of far‐red light on chlorophyll a/chlorophyll b ratios, chlorophyll‐protein composition, the stoichiometry of electron transport complexes or photosynthetic function of isolated thylakoids. These results suggest that phytochrome is ineffective in modulating the composition and function of thylakoids in pea plants grown at low irradiance. One possible explanation of the ineffectiveness of phytochrome on thylakoids is discussed in terms of the drastic attenuation of red relative to far‐red light in green tissue.
Effects of red, far‐red and blue light on the viscosity of the cytoplasm of wheat leaf cells
Authors: Virgin Hemming I.
Published: May 2006

The displacement by centrifugation of the cell contents of wheat (Triticum aestivum L. cy. Weibull's Starke) was studied after various light treatments. In dark‐grown leaves the viscosity of the cytoplasm, measured as the time necessary to displace the cell contents, is low, but increases slowly during continuous red irradiation as well as after a short red pulse. The increase after a red light pulse can be nullified by a short far‐red irradiation which in itself has no effect. Unlike that found earlier for Elodea densa Casp., and verified in the present study, the cytoplasm of wheat leaves does not show any rapid response to blue light, not even after pretreatment with red light.
A comparison of prolamellar bodies from wheat, Scots pine and Jeffrey pine. Pigment spectra and properties of protochlorophyllide oxidoreductase
Authors: Selstam Eva , Widell Anna , Johansson Lennart B.‐Å.
Published: May 2006

Inner etioplast membrane fractions were isolated from wheat (Triticum aestivumL. cv. Starkell), Scots pine (Pinus sylvestrisL.) and Jeffrey pine (Pinus jeffreyiMurr), in order to investigate whether cotyledons of dark‐grown conifers have protochlorophyllide associated to protochlorophyllide oxidoreductase (EC 1.6.99.–) in the pro‐lamellar body in the same way as angiosperms. Protochlorophyllide was found to be present in dark‐grown seedlings of Scots pine and Jeffrey pine to the same extent as in dark‐grown wheat, 10–15.8 nmol (g fresh weight)−1. Fluorescence emission spectra at 77 K showed accumulation of protochlorophyllide with emission maximum at 657 nm in the prolamellar body fractions of the three species studied. Also the light‐ and NADPH‐dependent activity of protochlorophyllide oxidoreductase was consistently localized in the prolamellar body fractions. The three prolamellar body fractions were dominated by the same polypeptide. Its molecular weight was estimated to be 38 000 by sodium dodecylsulphate polyacrylamide gel electrophoresis.
Cell infrastructure and some enzyme activities in rice coleoptiles grown in air and in anoxia
Authors: Rascie Nicoletta , De Bellis Luigi , Alpi Amedeo
Published: May 2006

The rice (Oryza saliva L. cv. S‐6) cells in anaerobic coleoptiles maintained their ultra‐structure. Most of the organelles did not show significant changes as compared to those from aerobic tissues. However, the number of mitochondria was reduced by 34% and they showed enlarged cristae. Most affected were unspecialized micro‐bodies: Their number was reduced by 80% under anaerobiosis and both matrix and membrane structure appeared altered. The activities of the unspecialized microbody enzymes, glycolate oxidase (EC 1.1.3.1), urate oxidase (EC 1.7.3.3) and catalase (EC 1.11.1.6) were alt reduced by anoxia. Catalase decreased to the same extent as the number of microbodies.
Flower induction by atrazine analogues in seedlings of Asparagus officinalis
Authors: Abe Tomoko , Shimizu Ryo , Iwamura Hajime , Kameya Toshiaki
Published: May 2006

Flower formation in one‐month‐old seedlings of asparagus (Asparagus officinalis L. cv. Mary Washington 500 W) was increased by soaking the seeds for 12 days in solutions of an atrazine analogue. These compounds are known to affect electron flow in photosystem II. Whereas only 2.4% of the control seedlings flowered, one of the fourteen analogues tested caused 60% of the seedlings to flower at 400 μM. These seedlings continued to grow normally and produced new shoots, but these had no flowers. Flowers formed only at the shoot tip and were morphologically normal. Treatment with an atrazine analogue enables sex identification of the plants at an early stage.
Identification and subgrouping of Frankia strains using sodium dodecyl sulfate‐polyacrylamide gel electrophoresis
Authors: Gardes M. , Lalonde M.
Published: May 2006

Polypeptide patterns of soluble proteins from 35 Frankia strains from different plants of various geographical origins, belonging to Alnus and Elaeagnus host‐specificity groups were determined by one‐dimensional sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. The polypeptide pattern was qualitatively the same for each strain whatever the number of subcultures or the age. Two gel electrophoresis groups A and E were observed which matched with the Alnus and Elaeagnus host‐specificity groups, but with some exceptions. The polypeptide patterns of the 35 Frankia strains tested were separated into 13 gel electrophoresis subgroups. Five Frankia strains were inoculated separately or in 3 mixed combinations of 2 strains on Alnus glutinosa (L.) Gaertn. plants. The polypeptide patterns of the re‐isolates obtained from 5‐month‐old nodules were identical to the corresponding strains used initially in the inoculum. Dual infection was observed on single plantlets.
Relationships among pure cultured strains of Frankia based on host specificity
Authors: Baker Dwight D.
Published: May 2006

Fifty strains of Frankia were tested for their ability to nodulate six species of actinorhizal plants. Pure cultured strains were used to inoculate seedlings of Alnus glutinosa (L.) Gaertn., Alnus rubra Bong., Casuarina equisetifolia L., Elaeagnus angustifolia L., Hippophaë rhamnoides L. and Myrica cerifera L. in nutrient solution culture. From the results of this study, host inoculation groups among the actinorhizal plants were defined. Although overlap between host inoculation groups appears to be common, the results from this study did not support the view that Frankia strains are promiscuous. All Frankia strains tested in this study could easily be classified into four major host‐specificity groups.
Studies on Frankia sp. LLR 02022 from Casuarina cunninghanmiana and its mutant LLR 02023
Authors: Lechevalier M. P. , Labeda D. P. , Ruan J.‐S.
Published: May 2006

Frankia sp. LLR 02022, isolated from nodules of Casuarina cunninghamiana Miq., and its spontaneous mutant LLR 02023, show similar morphology but slight differences in cell chemistry and major differences in carbohydrate utilization. The mutant has the same phospholipids, phospholipid fatty acids and menaqmnones as the parent, but shows quantitative differences in peptidoglycan composition, pigment production and triglyceride fatty acids. The parent utilizes only rhamnose; the mutant also utilizes arabinose, glucose and xylose under certain conditions of growth. The significance of these findings is discussed.
Isolation and characterization of Frankia from nodules of actinorhizal plants of Pakistan
Authors: Chaudhary Ashraf H. , Mirza M. Sajjad
Published: May 2006

Frankia strains have been isolated from actinorhizal nodules of Alnus (2 strains), Casuarina (5 strains), Coriaria (1 strain), Datisca (3 strains), Elaeagnus (1 strain) and Hippophae (1 strain). The isolates were characterized for their growth on various carbon and nitrogen sources, nitrogen‐fining ability in culture and nodulation of seedlings of the original host plant.
Formation and regeneration of Frankia protoplasts
Authors: Normand Philippe , Simonet Pascal , Prin Yves , Moiroud André
Published: May 2006

A technique for forming protoplasts from Frankia cells and regenerating them to the normal hyphal mode of growth is described. Electron microscopy proved that protoplasts were studied and not spores or small hyphae. Regenerated colonies were investigated for genetic markers. One ArI3 colony had been cured of its plasmids without being affected in its symbiotic properties.
Nitrogenase is restricted to the vesicles in Frankia strain EAN1pec
Authors: Meesters Titia M. , Van Vliet Wihna M. , Akkermans Antoon D. L.
Published: May 2006

The presence of nitrogenase in vesicles and hyphae of Frankia EAN1pec was investigated by using immunogold labelling on ultrathin cryosections for electron microscopy. These studies resulted in the specific labelling of nitrogenase in the vesicles of nitrogen‐fixing cultures. No significant label could be found in the hyphae, indicating a strong repression of nitrogenase in the hyphae.
Sensitivity of selected Frankia isolates from Casuarina, Allocasuarina and North American host plants to sodium chloride
Authors: Dawson Jeffrey O. , Gibson Alan H.
Published: May 2006

Three experiments examined the effects of NaCl concentrations 0 to 500 mM on the growth of isolates of Frankia from Casuarinaceae and selected North American host plants. Four Casuarina isolates grew well in defined medium (pyruvate‐BAP) but not in a yeast extract medium. Conversely the non‐Casuarina isolates preferred the yeast‐extract medium, although two of them grew in the defined medium. When grown in their preferred medium, the Casuarina isolates were little affected by NaCl concentrations up to 200 mM but did not grow at 500 mM. The non‐Casuarina isolates, with the exception of an isolate from Purshia tridentata. were severely affected above 50 mM NaCl.

Nitrogenase activity (C2H2 reduction) by the non‐Casuarina isolates could not be detected in low‐N medium although protein determinations indicated that a low level of nitrogen fixation had occurred. All four Casuarina isolates showed nitrogenase activity in culture, up to 200 mM NaCl, although at that concentration of NaCl, growth was affected more than that of cultures in N‐supplemented medium. All four strains showed a marked increase in nitrogenase activity up to 72 h after the addition of C2H2, with the magnitude of the effect and their subsequent behaviour being strain dependent.

The results indicate that the isolates of Frankia from Casuarina and Allocasuarina, and that from Purshia tridentata, are more tolerant of NaCl than isolates from species not normally growing under sodic conditions. They provide optimism that these strains could successfully establish in saline soils if introduced with species of host plants tolerant to these soils.
Endophyte sporulation in root nodules of actinorhizal plants
Authors: Torrey John G.
Published: May 2006

All strains of isolated Frankia possess the genetic capacity to form sporangia since, when grown in vitro, they usually sporulate freely, depending on the physical and chemical environment in which they are cultured. Endophytic sporulation involving Frankia differentiation of sporangia within root nodules has been described in only 16 host species in 9 genera within six families of actinorhizal plants. From studies published to date, endophytic sporulation cannot be correlated with specific environmental conditions surrounding the host plants. Based on the literature and on previously unpublished observations from field and greenhouse studies, an account is given of the occurrence of sporulation in actinorhizal plants with emphasis on Alnus, Casuarina, Comptonia, Elaeagnus and Myrica. The possible role of the host plant in controlling Frankia sporulation as contrasted to the control exerted by the genetic constitution of the microbial symbiont is explored.
Frankia in acid soils of forests devoid of actinorhizal plants
Authors: Smolander Aino , Sundman Veronica
Published: May 2006

The capacity of some acid forest soils to induce nodulation on a hybrid between Alnus incana (L.) Moench and A. glutinosa (L.) Gaertn. was investigated. Soil was sampled from tree stands devoid for decades of actinorhizal hosts. Seven‐week‐old Alnus seedlings growing m liquid culture were inoculated with soil dilutions. The nodules were counted after 6 weeks and classified as Sp−, if they lacked spores, or as Sp+. if spores were present, according to microscopy of microtome sections. Frankia was found in all the forest soils studied, apart from a soil from a Betula swamp. The highest nodulation capacities on Alnus, caused predominantly by Frankia of the Sp− type. were observed in mineral soil sites with Betula stands — even higher than in soil from an A. incana stand. A positive correlation was found between the pH and the noduiation capacity of the soil.
Restriction pattern analysis of deoxyribonucleic acid isolated from callus and cell suspension of actinorhizal and non‐actinorhizal Betulaceae
Authors: Giasson L. , Lalonde M.
Published: May 2006

Using cell suspensions, a method was elaborated to isolate high‐molecular‐weight genomic deoxyribonucleic acid (DNA; 65 MDa or more) from members of the Betulaceae: Alnus incana (L.) Moench, Alnus glutinosa (L.) Gaertn. and Betula papyrifera Marsh. The method was also effective for isolation of DNA from callus cells. Based on the chemical lysis of protoplasts, this procedure yielded 130 μg (callus) to 250 μg (cell suspension) of DNA (g fresh cells)−1, with a ratio A200/A28 of 1.7–2.0. The purified DNA obtained, formed distinct bands when restricted fragments were electrophoresed. Among the 10 endonucleases used for restriction analysis of Alnus glutinosa, Alnus incana and Betula papyrifera genomes, PvuI1 (EC 3.1.23.33) was unique in giving identical patterns for the two Ainus species. An unusual pattern occurred when Al‐2 DNA was restricted with Ava II (EC 3.1.23.4). It formed a ladder with a repeating fragment unit of 181 base pairs long. With the enzymes tested, no differences in restriction patterns were observed among clones of Alnus incana (AI‐2 vs AI‐2), Betula papyrifera (BP‐4 vs BP‐8) and subclones of Ainus glutinosa AG‐1 (PLFJ709 vs LF1709), suggesting genetic stability of the Betulaceae cultures.
Genetic diversity within and among 11 juvenile populations of green alder (Alnus crispa) in Canada
Authors: Bousquet J. , Cheliak W. M. , Lalonde M.
Published: May 2006

Germinated seeds from 11 populations of green alder [Alnus crispa (Ait.) Pursh] sampled in four Canadian provinces were analysed for electrophoretically demonstrable diversity of 10 enzymes encoded by 15 structural loci. Of these, nine were polymorphic, and on average, 52% of the loci per population were polymorphic. Assuming a diploid model of expression, average level of expected heterozygosity was 0.11 with nearly all populations in Hardy‐Weinberg equilibrium for the set of polymorphic loci analysed. No significant inbreeding and associated subpopulation structuring were noted. Rates of gene flow appeared high within and among populations. Although little divergence was observed among populations, genetic and geographical distances between populations were related. Discriminant and cluster analyses revealed a pattern of genetic variation associated with geography. Populations from northern Quebec were poorly differentiated, whereas western populations from Alberta exhibited a larger degree of genetic differentiation. Introgresive hybridization with the sympatric species Alnus sinuata (Regel) Rydberg and partial isolation in the West are suggested as an explanation for this larger differentiation. The occurrence and significance of rare alleles is discussed in relation to the importance of geographical distance in the process of population differentiation in this species.
Preliminary analysis of root exudates of in vitro‐micropropagated Alnus glutinosa clones
Authors: Vergnaud L. , Chaboud A. , Rougler M.
Published: May 2006

Biochemical analysis at Alnus glutinosa (L.) Gaertn. root exudates was carried out in order to investigate the probable role of these exudates in the establishment of the Alnus‐Frankia symbiosis. Sufficient amounts of sterile root exudates were collected from plants originating from five in vitro‐micropropagated A. glutinosa clones (AG1, AG2, AG3, AG4, AG8) grown under aerobic conditions in nutrient solution with Ballotini glass beads. Cytological controls showed good preservation of roots at the end of the collecting period. The total protein and sugar contents of crude root exudates were determined and related to the dry root weight. These results showed a provenance effect. Soluble high molecular‐weight fractions (i.e. the mucilage) were isolated following rigorous purification of the crude root exudates and within this fraction proteins were characterized by isoelectric focusing. The protein pattern of the five clones tested showed major bands in common and some minor specific ones. These experimental data will serve as a useful basis for future physiological investigations.
Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species
Authors: Tremblay Marie‐Francine , Lalonde Maurice
Published: May 2006

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.

Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra. Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.
The effectivity of Frankia for nodulation and nitrogen fixation in Alnus rubra and A. glutinosa
Authors: Hooker John E. , Wheeler Christopher T.
Published: May 2006

The effectivity of nodulation of Alnus rubra Bong, by Frankia isolates from A. rubra and Alnus glutinosa (L.) Gaertn. in Northern Britain was compared with strains from The Netherlands and North America, using plants grown in combined nitrogen‐free conditions. All strains gave rise to spore (‐) nodules, even when isolated from nodules from sites known to contain spore (+) nodules. Nodules of all plants evolved little hydrogen, probably due to the presence of an efficient uptake hydrogenase in the microsymbkmts. Nodule weight as a percentage of whole plant weight was higher for nodules of low specific activity (N fixed per unit weight nodules), attaining a maximum of 5.1% of plant dry weight in the least effective of the heterologous associations of A. glutinosa Frankia with A. rubra. The range of variation in nodule specific activity was much greater in heterologous than homologous associations, but nodules of high specific activity were found in both associations. However, plants that fixed most N during the growth period were not those with nodules of highest specific activity. The most effective associations were homologous symbioses, which combined good nodule growth per plant with satisfactory specific activity, fixing N at rates which would support superior plant growth under the prevailing growth conditions. Preliminary field experiments suggest that the most effective of the A. rubra isolates is suitable for use as an inoculant in nurseries. Strains isolated from A. glutinosa were more effective and showed a different order of effectivity in homologous symbioses compared with their association with A. rubra. An A. glutinosa strain was isolated, which stimulated satisfactory nodule growth and gave good nodule specific activity in both A. rubra and A. gtutinosa.
Loss and recovery of nitrogenase in Abuts incana nodules exposed to low oxygen and low temperature
Authors: Huss‐Danell Kerstin , Winship Lawrence J. , Hahlin Ann‐Sofi
Published: May 2006

The possibility that respiration limits oxygen access to nitrogenase was tested by artificially upsetting the balance between oxygen consumption (respiration) and oxygen influx (diffusion). Argon treatment of the nodulated root system on intact plants stopped in vivo nitrogenase activity almost completely. Upon return to air, nitrogenase activity was very low and recovered gradually to full activity after about 5 h. In vitro measurements on nodule homogenates indicated that active nitrogenase was lost upon the shift from low (argon) to normal (air) oxygen. Maintenance of nodulated root systems at low temperature (2°C) inhibited both respiration and in vivo nitrogenase activity. Upon return to normal temperature (22°C), oxygen uptake recovered very rapidly, but nitrogenase activity recovered only gradually to full activity after about 5 to 6 h. Again, loss of active nitrogenase could, at least partly, explain the reduced in vivo nitrogenase activity. The effects from a temporarily impaired balance between oxygen consumption and oxygen influx thus point to the importance of respiration for limiting oxygen access to nitrogenase.
The acetylene reduction assay inactivates root nodule uptake hydrogenase in some actinorhizal plants
Authors: Winship Lawrence J. , Martin Kendall J. , Sellstedt Anita
Published: May 2006

Actinorhizal nodules do not usually evolve H2 due to the action of an uptake hydrogenase. We have found that nodules of several Frankia symbioses evolved large amounts of H2 gas when returned to air following exposure to 10 kPa C2HT2 during an acetylene reduction assay. Increased H2 evolution in air persisted for several days when intact root systems of Alnus incana (L.) Moench (inoculated with Frankia UGL 011101) were treated with 10 kPa C.H2 for 1 h. Full recovery of uptake hydrogenase activity required 4 to 8 days. Studies with crude homogenates of nodules of the same plants showed that hydrogenase (measured amperometrically with phenazine metho‐sulfate as electron acceptor) was directly affected, since activity in treated nodules was only 10% of that in untreated nodules. A survey of actinorhizal symbioses revealed variation in the effect of an acetylene reduction assay on hydrogen metabolism. Nodules of three species, including Alnus rubra Bong, inoculated with Frankia HFPArD. showed complete inactivation of hydrogenase. H2 evolution in air was 25% of the C2H2 reduction rate and H, evolution in Ar/O2 was equal to the QH2 reduction rate. Two symbioses, Ceanothus americanus L. (soil inoculant) and Batista glomerata Baill. (soil inoculant) showed no change following an acetylene reduction assay. A third group of symbioses showed an intermediate response.
Hydrogen metabolism of Casuarina root nodules: A comparison of two inoculum sources
Authors: Sellstedt Anita , Winship Lawrence J.
Published: May 2006

Hydrogen metabolism was studied in three Casuarina species, C, equisetifolia Forst., C. glauca Sieb. ex. Spreng. and C. obesa Miq., either inoculated with the pure Frankia culture HFP CcI3 or inoculated with a crushed nodule inoculum made from C. glauca nodules. Nitrogenase (EC 1.7.99.2) activity and hydrogen evolution was measured on intact plants, while hydrogen uptake was measured on excised nodules and in nodule homogenates.

Nitrogenase activity was highest in C. glauca inoculated with C. glauca nodules, while no hydrogen evolution was detected. Hydrogen evolution was highest in the symbiosis between C. equisetifolia and HFP CcI3, but the nitrogenase activity showed intermediate values compared to the other symbioses. Measured at a concentration of 93 μM H2, H2 uptake was highest in C. glauca inoculated with the C. glauca inoculum. H2 uptake activity in homogenates was 83% of the intact nodule rate. With phenazinemethosulfate as the electron acceptor, H2 uptake by nodule homogenates showed typical Michaelis‐Menten kinetics with a Km of 21.3 μM for H2.

The data presented here indicate a host plant effect on the endobiont which alters the hydrogen metabolism.
The abilities of three Frankia isolates to nodulate and fix nitrogen with four species of Casuarina
Authors: Rosbrook P. A. , Bowen G. D.
Published: May 2006

Three isolates of Frankia from nodules of Casuarina sens, strict. (JCT287. JCT295 and 20607) were compared in their abilities to nodulate and fix N, when associated with four species of Casuarina (C. cunninghamiana Miq., C. equisetifolia Forst., C obesa Miq. and C. glauca Sieb. ex Spreng) growing in a N‐deficient soil.

All three Frankia isolates nodulated each of the four species of Casuarina. At 27 weeks after inoculation, growth (dry weight) of inoculated plants was 3.6 to 5.0 times greater than that of uninoculated plants. There were no significant differences in plant dry weight, the N concentration of shoots or roots, or the amount of N, fixed per plant among the Frankia isolates for each of the species of Casuarina studied. The infectivity and effectiveness in N, fixation of Frankia strain JCT287 with C. cunninghamiana was similar when two different defined media were used for culture of the inoculum.
Immobilization of plant protoplasts on solid supports
Authors: Vaňková Radomíra , Bornman Chris H.
Published: May 2006

Brassica napus L. and Rosa sp. protoplasts were immobilized on variously treated Biosilon, Cytodex 1, 2 and 3, Separon, Sephadex, Sepharose and Sorfix micro carriers. Best anchorage of protoplasts of both species was obtained with Biosilon and Cytodex 3 coated with polylysine of high molecular weight (55 and 450 kDa), as well as with concanavalin A‐coated Cytodex 1. Precoating of micro carriers with bovine serum albumin was generally without effect.
Influence of growth retardants on the internode and ethylene production of sunflower plants
Authors: Sauerbrey EIke , Grossmann Klaus , Jung Johannes
Published: May 2006

The growth‐retarding activity of the norbornenodiazetine tetcyclacis and the di‐oxanylalkenyl triazole LAB 150 978 as well as the ethylene‐forming compounds 2‐chloroethyl‐phosphonic acid (ethephon) and 1‐amino‐cyclopropane‐l‐carboxylic acid (ACC) on stem histogenesis and ethylene production of sunflower plants (He‐lianthus annuusL. cv.Spanners Allzweck) has been studied. The shoot growth of plants hydroponically grown and treated was reduced by the compounds. The shortening in the length of the 1st internode caused by tetcyclacis and LAB 150 978 was mainly induced by inhibition of cell division (the internode possessed fewer cortical cells per cell file). In contrast, ethephon and ACC decreased internode elongation mainly by reducing the rate of cell enlargement.

The ethylene production of sunflower seedlings cultivated on agar nutrient medium rose with increasing concentrations of ethephon and ACC, the shoot length of the plants being progressively reduced.

Tetcyclacis and LAB 150 978 inhibited both the formation of ethylene and shoot growth. It is suggested that in contrast to ethephon and ACC, tetcyclacis and LAB 150 978 do not achieve their growth‐retarding effect by influencing the production of ethylene.
Mechanism of phosphorus‐induced zinc deficiency in cotton. III. Changes in physiological availability of zinc in plants Is mail
Authors: Cakmak Ismail , Marschner Horst
Published: May 2006

The effect of varied supply of P (2.5× 10−5 to 6× 10−4 M) and Zn (0 to 10−6 M) on uptake and concentrations of P and Zn was studied in cotton (Gossypium hirsutum L. cv. Deltapine 15/21) grown in nutrient solution under controlled environmental conditions. At a given Zn supply, increasing levels of P had no significant effect on the concentrations of total Zn in plants. However, increasing levels of P induced or enhanced visual Zn deficiency symptoms when the Zn concentration in the nutrient solution was low. The concentrations of water‐soluble Zn in roots and shoots constituted 60% of the total Zn concentrations for plants grown with low P and 30% for plants grown with high P. The concentration of water‐soluble Zn in leaves, but not total Zn, was closely correlated with visual Zn deficiency symptoms, levels of chlorophyll, super oxide dismutase and membrane permeability. The critical deficiency concentration of water‐soluble Zn in cotton leaves was in the range of 6 to 7 μg (g dry weight)−1 or about 1.0 μg (g fresh weight)−1. The results show that high P concentrations in plant tissue decrease the physiological availability of Zn. Water‐soluble Zn in the tissue appears to be a suitable indicator for Zn nutritional status in general and phosphorus‐induced Zn deficiency in particular. Also in field‐grown orange trees (Citrus sinensis) visual Zn deficiency symptoms in leaves were closely related to the concentration of water‐soluble Zn.