bluuebunny/crossref_metadata_2025_split huggingface dataset:
Root colonization ofLupinus latifoliusAgardh. andPinus contortaDougl. byPhialocephala fortiniiWang & Wilcox
Authors: O'DELL T. E. , MASSICOTTE H. B. , TRAPPE J. M. 
Published: April 2006

SUMMARYRoot colonization patterns were studied afterPhialocephala fortiniiwas inoculated onLupinus latifolius(broad‐leafed lupin), a nitrogen‐fixing legume, andPinus contorta(lodgepole pine). The fungus colonized epidermal and cortical cells in the root hair zone on ultimate pine roots, as well as cortical and epidermal cells of primary roots of both hosts. Fungal colonization was inter‐ and intracellular with sclerotia forming in cells of both hosts. Labyrinthine tissue, a type of fungal differentiation that occurs in the Hartig net of ectomycorrhizas, formed sporadically on pine roots. Similar colonization has been observed on conifers and many other plants, but this report is the first showing that a single fungus can form such structures on both pine and lupin.
Retention and spread of a genetically engineered pseudomonad in seeds and plants of Zea mays L. – a preliminary study
Authors: FISHER P. J. , BROAD S. A. , CLEGG C. D. , LAPPIN SCOTT H. M. 
Published: April 2006

SUMMARYThe survival of a genetically engineered strain of Pseudomonas fluorescens introduced to the seeds, stems and leaves of maize plants was monitored using viable cell counts on selective agars. The bacterium was introduced to the seeds under vacuum and stored at either room temperature or 5°C. The bacterium was detected after 1 d, but not after 8 d, in seeds stored at room temperature, whereas at the lower temperature it was still detected after 43 d. Other inoculated seeds were grown either in a nutrient solution or in potting compost. Studies of survival within both seed remnants and roots, and on the aerial parts of the plants, demonstrated that the majority of bacteria remained in the seeds with some movement into the roots. Seeds retained a greater colonization frequency than roots in plants grown in both soil and nutrient solution. Those plants grown in nutrient solution maintained higher bacterial populations in seed remnants and roots than those grown in soil. Viable counts of P. fluorescens within seed remnants and roots decreased in soil‐grown plants over a 43 d monitoring period. No introduced organisms were detected in either stem core sections or other aerial parts of any of the inoculated plants, yet the cores were shown to contain an indigenous population of up to 4.8 × 104 cells g−1 tissue. When mature plants were injected with the bacterium viable counts of the pseudomonad below and above the injection points demonstrated the ability of the bacterium to translocate in the stem after the wounding process. P. fluorescens applied to the leaf surfaces remained viable for at least 20 d but showed great variations in numbers with values ranging from 0 to 1.4 × 106 g−1 tissue. The practical applications of introducing genetically engineered microorganisms into plants as control measures against pathogens and insect pests are briefly discussed.
Annual changes in dormancy and germination in seeds of Sisymbrium officinale (L.) Scop.
Authors: BOUWMEESTER HARRO J. , KARSSEN CEES M. 
Published: April 2006

SUMMARYThe effect of environmental conditions on changes in dormancy and germination of seeds of Sisymbrium officinale (L.) Scop, was studied. Seeds were buried in soil in the field or in incubators and at regular intervals, germination of exhumed seeds was tested over a range of conditions. Seeds that were buried in the field showed clear seasonal changes in dormancy. Fluctuations in soil moisture and nitrate content were not required for the changes in dormancy. Temperature seemed to be the only factor regulating these changes. Dormancy was relieved in periods of low temperatures and induced in periods of high temperatures. Fresh seeds and seeds buried for only a few months germinated best at elevated temperatures whereas seeds buried for a longer time germinated best at low‐temperatures. Light, nitrate and desiccation stimulated germination of exhumed seeds. As a consequence, these treatments extended germination over a much longer period of the year. Germination of exhumed seeds in Petri dishes at field temperature was reasonably described by a model based on the dual role of temperature, in the regulation of both dormancy and subsequent germination.
The effect of temperature on the sensitivity of nitrogenase to oxygen in the cyanobacteria Anabaena cylindrica (Lemmermann) and Gloeothece (Nägeli)
Authors: GALLON JOHN R. , PEDERSON DENNIS M. , SMITH GEOFFREY D. 
Published: April 2006

SUMMARYTransient exposure to elevated temperature (37‐40 °C) inhibited N2 fixation (acetylene reduction) in cultures of the heterocystous cyanobacterium Anabaena cylindrica (Lemmermann) ATCC 27899 and the unicellular, non‐heterocystous cyanobacterium Gloeothece sp. (Nägeli) ATCC 27152. In neither organism was inhibition of N2 fixation due to thermal inactivation of nitrogenase. Rather, inactivation of N2 fixation at elevated temperature was a consequence of increased sensitivity to inhibition by O2 In A. cylindrica, thermally induced inactivation of N2 fixation by O2 could be correlated with inhibition of uptake hydrogenase. However, in Gloeothece, inhibition of carbon‐supported respiratory O2 consumption by elevated temperature was the probable cause of the increased sensitivity of N2 fixation to O2.
Delayed NH3 and N2O uptake by maize leaves
Authors: GRUNDMANN G. L. , LENSI R. , CHALAMET A. 
Published: April 2006

SUMMARY 15N was used to give evidence of NH3 and N2O absorption by maize leaves. A short‐term labelling method (90 min) was chosen with high NH3 concentration (40 μ1 1−1) to assess uptake mechanisms. Two initial entry pathways were suggested for NH3: fast uptake with immediate metabolism and fast storage with progressive metabolism. A storage compartment delayed NH3 absorption after exposure. Similar mechanisms might be involved in N2O uptake.
Do inorganic solutes limit growth of the facultative hemiparasite Rhinanthus minor L in the absence of a host?
Authors: SEEL W. E. , PARSONS A. N. , PRESS M. C. 
Published: April 2006

SUMMARYThe response of the facultative hemiparasitic angiosperm Rhinanthus minor to inorganic solutes was investigated by supplying plants not attached to a host with nitrogen, phosphorus and potassium. Solutes were supplied both individually (in pots) and in combination (under field conditions). Only phosphorus resulted in any significant stimulation of growth. The phosphorus treated plants also had higher rates of light saturated photosynthesis and higher water use efficiencies than control plants. In contrast to many autotrophic plants, nitrogen neither stimulated growth nor photosynthesis.
Morphological plasticity of the clonal herb Lamiastrum galeobdolon (L.) Ehrend. & Polatschek in response to partial shading
Authors: DONG MING 
Published: April 2006

SUMMARYThe present experiment investigates the morphological plasticity of Lamiastrum galeobdolon (L.) Ehrend. & Polatschek in response to light patchiness. In a garden experiment, stolons of the plant were grown under the following six light regimes: high light, low light, from low light to high light, from high light to low light, under high light but with the apical region of the stolon under low light, and under low light but with the apical region under high light. The low‐light conditions provided 50% of high light PAR and 28% of high light R/FR ratio (ratio of red to far red light), and simulated the canopy‐like shade that may be relevant to this species in its natural habitat.Plants growing under different light treatments did not show significant differences in total plant dry weight, total number of ramets, number of primary ramets, number of secondary ramets, and number of branches per clone. L. galeobdolon plants growing under high‐light conditions formed shorter internodes, shorter petioles and smaller laminas with lower SLA, and showed higher branching intensity than those growing under low‐light conditions. Accordingly, when growing between patches of different light conditions, the primary ramets had shorter internodes, shorter petioles and smaller laminas with lower SLA in high‐light than in low‐light patches. Exposing the apical region, of an otherwise shaded stolon, to high light shortened its internodes, compared with those of plants growing entirely under low‐light conditions. Shading the apical region, of otherwise unshaded stolon, had no effect on the lengths of these internodes. In contrast, the morphology of the leaf responded to local light conditions only.Elongation of stolon internodes was completed much faster (within 2 or 3 wk) than lamina expansion and petiole extension, which took at least 6 wk.These results are interpreted in terms of the efficiency of exploitation of high‐light patches within the habitat of L. galeobdolon.
Carryover effects on the clonal growth of the grass Holcus lanatus L.
Authors: BULLOCK J. M. , MORTIMER A. M. , BEGON M. 
Published: April 2006

SUMMARYThe effects of clipping and daylength treatments and their carryover effects on the clonal growth of the perennial grass Holcus lanatus L. were investigated. Plants from ten clones were grown in six combinations of two daylength and three clipping treatments. Both clipping and low daylength reduced the tillering rate of all the clones but the clones differed in their degree of response to these treatments. After eight weeks, the treatments were discontinued and plants were grown in a common environment for seven weeks. Four‐week‐old tillers from the plants were repotted and grown in a common environment to examine the possibility of ‘carryover’ effects of the parental environments. After 8 wk of growth, there were main and interaction carryover effects of daylength and clipping on the tillering rates, biomass and tiller extension rates of the plants, which, however, differed greatly among clones. These differences among clones in both direct and carryover treatment effects, on clonal growth, indicate how the effects of many different environmental variables may interact to produce an environment that is highly heterogeneous in space and time, influencing the coexistence of genotypes and species.
Competition between diploid and derivative autotetraploid Dactylis glomerata L. from Galicia. Implications for the establishment of novel polyploid populations
Authors: MACEIRA N. O. , JACQUARD P. , LUMARET R. 
Published: April 2006

SUMMARYThe competitive ability of a tetraploid, and its morphologically indistinguishable progenitor diploid Dactylis glomerata L., from Galicia (Spain), was tested in a two‐year study, using isolated plants and the same individuals grown at two densities (16 and 36 plants per pot, respectively). Inverse linear regression equations were used to quantify the response of the different ploidy levels (hereafter cytotypes) to density. For the diploids, inter‐cytotype competition coefficients were significantly higher than intra‐cytotype coefficients. The substitution rate increased from 1. in the first year to 3.9 in the second year, when most of the diploids failed to flower and some died. The competitive superiority of the tetraploids was associated with higher mean tiller weight, particularly in the mixed cultures. The tetraploids also had heavier seeds and faster leaf production in early spring, and they flowered earlier than the diploids. Several of these differences between cytotypes appear to be due to differences in ploidy level and may play a major role in the establishment of the tetraploids in Galician pastures, where competition is high.
Flandrian vegetational history of southeastern England. Pollen data from Pannel Bridge, East Sussex
Authors: WALLER M. P. 
Published: April 2006

SUMMARYPollen data, plant macrofossil remains and lithostratigraphy are used to reconstruct Flandrian vegetational history from a coastal site in south‐eastern England. The record at this site, Pannel Bridge in East Sussex, extends back to c. 10000 BP and is the most complete so far obtained from this region.The thirteen pollen assemblages zones defined reflect, in part, the complex development of the site. Prior to c. 8500 BP, wetland in the Pannel valley was localized around the site. Between c. 8500 and c. 6000 BP, in response to changes in coastal configuration, such areas underwent expansion and the valley floor was occupied alternately by sedge fen and Alnus carr. A period of stability followed, with Alnus‐dominated communities prevailing for c. 2000 yr. From c. 4000 to c. 2200 BP local conditions were more open with Cyperaceae and subsequently Myrica the dominant wetland types. Alnus carr became re‐established c. 2200 BP.The vegetational history of adjacent dryland areas is obscured by the changing local conditions and nature of the deposits investigated. The problems of reconstructing past vegetation from coastal peats are explored. Amongst these are the determination of the pollen source area, establishing an environment of origin for many herb types, and distinguishing the processes controlling wetland vegetational change.The discussion focuses on the arrival and expansion of arboreal taxa in the early Flandrian and human activity. Unusually, Alnus is present in the pollen and macrofossil record from c. 10000 BP onwards. In dryland areas, after an initial Pinus, Betula phase, Corylus populations expanded c. 9500 BP, Quercus and Ulmus became woodland components from c. 9100 BP and c. 8400 BP onwards respectively. Pollen values for Tilia increased c. 7000 BP and Fraxinus c. 5900 BP though both of these taxa were probably locally present earlier. Openings in the forest canopy appear to have persisted after the arrival of the deciduous trees, possibly as a consequence of human activity during the mesolithic. There is some palynological evidence for human presence accompanying the elm decline, though substantial clearance did not occur until the decline in Tilia, c. 3700 BP. This, and a subsequent phase of disturbance c. 3200 BP, appear not to have been followed by periods of intense human activity. Woodland regeneration may have occurred c. 2000 BP.
Pattern of fructan synthesized in cell‐free extracts from leaf blades of chilled Triticum aestivum
Authors: BANCAL PIERRE , GAUDILLÈRE JEAN PIERRE 
Published: April 2006

SUMMARYFructosyltransferase activities were studied with varying concentrations of sucrose in cell‐free extracts from wheat (Triticum aestivum L.). A C18‐HPLC separation method was used to quantify the synthesized compounds individually. Hexoses and 1‐kestose were the major products at all temperatures and concentrations of sucrose. 1‐Kestose production was maximal at 25 °C, with an apparent Km of about 250 m, but competition for sucrose by invertase affected this value. Neokestose, which is not observed in vitro, and 6‐kestose were also formed in vitro, but at a much lower rate and at lower sucrose affinity than 1‐kestose synthesis. When extracts were incubated with a high initial concentration of sucrose for up to 1 d, five new fructan oligomers appeared. Four of these were also accumulated early in vitro by chilled blades, whereas the fifth belonged to the neokestose series. The rates of synthetic oligomers are compared to those in vivo. Invertase‐linked artefacts are present in wheat, but not overwhelming as they are in Lolium temulentum.
Ultrastructure and chemical composition of some isolated plant cuticles in relation to their permeability to the herbicide, diuron
Authors: GOURET EVELYNE , ROHR RENE , CHAMEL ANDRE 
Published: April 2006

SUMMARYThe ultrastructure of leaf and fruit cuticles from nine species was investigated before and after their enzymatic isolation. No major alteration was observed in the internal ultrastructure of cuticles after the isolation process. The isolated cuticle preparations showed several levels of complexity from the Pyrus communis L. leaf cuticle represented by a simple layer, to the Vanilla planifolia Andr. leaf cuticle preparation having extensive cell walls on its inner face. Two main ultrastructural types were distinguished; cuticles characterized by an almost entirely reticulate structure and cuticles characterized by an outer lamellate region with an inner reticulate region. The permeability of isolated cuticles to diuron was measured with a double water compartment device using 14C‐diuron. The permeability coefficient (P) ranged from 1.9 to 40.1 nm s−1 for seven species. The mean value of P for cuticles having an entirely reticulate structure was higher than that for cuticles with an outer lamellate zone. Moreover, for each of the two ultrastructural types, the permeability decreased with an increase in soluble wax content expressed per surface unit.
The effects of ozone episodes on autumn leaf fall in apple
Authors: WILTSHIRE J. J. J. , WRIGHT C. J. , UNSWORTH M. H. , CRAIGON J. 
Published: April 2006

SUMMARYMature apple (Malm domestica Borkh.) trees were exposed to episodes of 100 and 150 nl l−1 ozone in 1990 and 1991 respectively, in open‐top chambers at the University of Nottingham, Sutton Bonington Campus, UK. The episodes were for 8 h daily and for not more than 3 d in succession, with a seasonal total of 37 d in each year. Leaf fall was monitored by counting leaves on marked shoots at frequent intervals. A significant interaction between ozone exposure and leaf age was observed: exposure to ozone accelerated autumn leaf fall in old leaves. The relationships between experimental conditions, leaf age and plant material are discussed, and the implications for UK flora are considered.
Resveratrol production as a part of the hypersensitive‐like response of grapevine cells to an elicitor from Trichoderma viride
Authors: CALDERÓN ANTONIO A. , ZAPATA JOSE M. , MUÑOZ ROMUALDO , PEDREÑO MARÍA A. , BARCELÓ A. ROS 
Published: April 2006

SUMMARYSuspension cell cultures of grapevine (Vitis vinifera, cv. Monastrell) treated with an elicitor (cellulase, Onozuka R‐10) from Trichoderma viride showed a hypersensitive‐like response. This was characterized by cell plasmolysis and was accompanied by localized cell death, which was concomitant with cell culture browning, itself probably due to an activation of oxidative phenolic metabolism driven by a large increase in endogenous levels of H2O2. In addition to these responses, the treatment of cell cultures with the elicitor produced an increase in amounts of benzoic acid and of resveratrol, the latter a potent phytoalexin of grapevines. This hypersensitive‐like response was specific since none of the above responses was obtained with other cell wall‐degrading enzymes from several sources, or with inocula of either mycelial extracts or culture filtrates of Botrytis cinerea. These results are discussed in the light of a disease‐resistance reaction induced in grapevine cells by a product of T. viride, a fungal agent characterized by its effective biocontrol of Botrytis cinerea, the causal agent of grey mould in grapevines.
Colonization of wheat (Triticum vulgare L.) by N2‐fixing cyanobacteria: III. The role of a hormogonia‐promoting factor
Authors: GANTAR M. , KERBY N. W. , ROWELL P. 
Published: April 2006

SUMMARYInitial colonization of the roots of wheat plants by Nostoc 2S9B in liquid culture was by motile hormogonia, irrespective of whether co‐culture was started using a cyanobacterial inoculum consisting of hormogonia or of aseriate packages. In the latter case the aseriate packages differentiated into hormogonia and this was most rapid and extensive when co‐culture was carried out in NO3−‐free BG‐11 medium. Hormogonia‐promoting activity appears to be due to a plant product that can be extracted from roots and is released into the growth medium in the presence or absence of the cyanobacterium. Induction of hormogonia was inhibited by 17 mM NaNO3, the concentration in BG‐11 medium. This effect was apparently not due to the presence of a combined N source (NO3−) per se but appears to be an ionic effect on the functioning of the hormogonia‐promoting factor, since other salts (NaCl and KNO3) had the same effect as NaNO3. The presence in aseriate packages of an autoinhibitor of hormogonia differentiation is inferred from the effects on hormogonia differentiation of washing aseriate packages. The hormogonia‐promoting factor from wheat roots appears to act antagonistically with respect to the autoinhibitor of hormogonia differentiation. Following initial colonization of plants roots by hormogonia, the cyanobacterial filaments progressed through a complete developmental cycle of hormogonia, long filaments and tightly bound aseriate packages, with subsequent differentiation of hormogonia from these aseriate packages giving rise to further colonization of the growing roots. The attachment of Nostoc 2S9B to the root surface may involve an initial attachment of hormogonia via fimbriae, and a subsequent tight binding of the cyanobacterium by means of the mucilaginous sheath.
Growth responses of two contrasting upland grass species to elevated CO2 and nitrogen concentration
Authors: BOWLER J. M. , PRESS M. C. 
Published: April 2006

SUMMARYGrowth parameters of Agrostis capillaris L. and Nardus stricta L. were measured in relation to ambient and elevated concentrations of CO2 (340 and 550 μl CO2l−1, respectively) and at low and high concentrations of nitrogen (0.8 and 3 mM NH4NO3, respectively). After 60 d of growth A. capillaris had attained approx. four times the total dry weight of N. stricta in all treatments, which was attributed to the greater leaf area ratio of the former. A. capillaris grown at the low nitrogen concentration attained 30% of the total dry weight of plants grown at high nitrogen. Over the 60 d period, destructive harvests (seven in total) showed the growth of N. stricta to be less sensitive than that of A. capillaris to the concentration of nitrogen, but in both species growth analysis showed the lower total dry weight at low nitrogen to be attributable to lower unit leaf rate. There was a differential response of both species to elevated concentrations of CO2, which was nitrogen dependent. A. capillaris grown at elevated CO2 attained a greater total dry weight than at ambient CO2 and this response was proportionately greater at low nitrogen (78% increase) than at high nitrogen (58% increase). In contrast, in N. stricta there was no effect of CO2 concentration on the total dry weight at low nitrogen whilst at high nitrogen plants grown at elevated CO2 had a greater total dry weight after 48 d of growth. Calculation of the allometric coefficient (K) relating root growth to shoot growth indicated that the effect of the lower nitrogen concentration was to increase partitioning to the roots while the higher CO2 concentration did not alter partitioning.