bluuebunny/crossref_metadata_2025_split huggingface dataset:
torphological and physiological changes in ectomycorrhizas of spruce [Picea excelsa (Lam.) Link] associated with ageing
Authors: AL ABRAS K. , BILGER I. , MARTIN F. , LE TACON F. , LAPEYRIE F. 
Published: April 2006

summaryEctomycorrhizas of four‐year‐old Picea excelsa (Lam.) Link seedlings, grown in nursery soil, are described. The main ectomycorrhiza type, occurring on 55–80% of the root apices, exhibited a normal sheath. The associated symbiotic fungus probably belonged to the Hebeloma genus. Behind these extomycorrhizal root lips, older ectomycorrhizas were observed and the apical ones presumably originated from those. One‐ and two‐year‐old ectomycorrhizas lacked sheaths, but a normal Hartig net could be observed in transverse sections. The metabolic‐activity of these older ectomycorrhizas, as measured by radiorespirometry of [14C]glucose, was reduced compared to the younger symbiotic organs. This glucose respiration was, however, still larger than the activity of non‐mycorrhizal exploratory roots. The mechanism of sheath loss and its significance as an ageing process are discussed.
The involvement of glutamate dehydrogenase and glutamine synthetase in ammonia assimilation by the rapidly growing ectomycorrhizal ascomycete, Cenococcum geophilum Fr.
Authors: MARTIN F. , STEWART G. R. , GENETET I. , MOUROT B. 
Published: April 2006

summaryIn order to determine significance of the glutamate dehydrogenase pathway and a glutamine synthetase/glutamate synthase cycle in NH4+ assimilation, we followed a number of different metabolikc parameters (nutrient uptake, free amino acid pools, NH4+‐induced glutamine accumulation) and 15N incorporation into amino acids of rapidly growing Cennoccum geophilum. Arginine was a major free amino acid in C. geophilum during its entire growth period. C. geophilum synthesized and accumulated very large amounts of glutamine at the beginning of the rapid phase of growth in low nitrogen medium, during the whole growth period in high nitrogen medium, and immediately after addition of NH4+. Therefore, the accumulation of a large amount of glutamine tool; place when the external ammonium concentration was high. The current data identify four pathways of N metabolism in rapidly growing C. geophilum: (1) glutamine synthesis, invoking transfer of N to both amino and amino moieties; (2) glutamate formation; (3) transamination with pyruvate to yield alanine; (4) transamination with oxaloacetate to yield asparate. The higher accumulation of glutamate and related amino acids (alanine and aspartate) in the presence of the glutamine synthetase inhibitor methionine sulphoximine indicates that glutamate, the precursor of glutamine, was formed by a pathway insensitive to methionine sulphoximine, the glutamate dehydrogenase pathway. Up to 40% of the assimilated 15N terminated in the amido‐N of glutamine. These data are consistent with a pivotal role for glutamine synthetase activity and indicates that the primary assimilation of NH4+ in rapidly growing C. geophilum is brought about by concurrent activity of the GDH and GS pathways. The pathway of primary assimilation of NH4+ by C. geophilunt in the rapid phase of growth therefore differs from those operating in the stationary phase of growth where N flax through GDH is higher than the flux through the GS pathway.
Recognition in flowering plants: A comparison of the Brassica self‐incompatibility system and plant pathogen interactions
Authors: HODGKIN T. , LYON G. D. , DICKINSON H. G. 
Published: April 2006

summaryMorphological, genetic, and biochemical data on the sporophytic self‐incompatibility (SI) system of Brassica spp. are evaluated and compared with those from host‐pathogen (HP) interactions which conform to the gene‐for‐gene hypothesis and are characterized by the production of phytoalexins.SI and HP systems have many features in common, reflecting similarities in the processes of discrimination, particularly with respect to the response to an incompatible recognition event. Thus, both recognition reactions involve cell surface components which are likely to be glycoproteins in at least one of the partners. Both incompatible responses are active processes requiring enzyme synthesis, are biostatic rather than biocidal with respect to pollen and pathogen, and are accompanied by the production of low molecular weight phytoalexin‐like compounds. Recent evidence also suggests that incompatible HP interactions may involve recognition of ‘self’ cell wall components. These similarities are distinguished from those, such as the production of cuticle and cell wall degrading enzymes, which may result only from the common requirement of pollen and pathogen to penetrate through the plant surface. The significance of the most obvious differences between the two systems, such as the evidence that SI may be mediated through the supply of water lo the pollen grain and the absence, in SI interactions, of cell necrosis or ‘cross protection’ reactions is also explored. It is suggested that some of the observed differences may result from ‘pre‐programming’ of the SI response.
The effects of zinc contamination from electricity pylons – evolution in a replicated situation
Authors: AL‐HIYALY S. A. , McNEILLY T. , BRADSHAW A. D. 
Published: April 2006

summaryMost electricity pylons are zinc coated. It might be possible for this to cause zinc contamination of soil beneath the pylons sufficient to impose selective forces by which zinc‐tolerant populations would develop in a replicated manner. An investigation of Agrostis capilluris L. populations sampled under a series of pylons in North Wales shows that:

Zinc concentrations are considerably greater in soils beneath pylons, particularly adjacent to pylon legs.
Soils sampled under different pylons had mean zinc concentrations varying from 1250 ± 200 to 6500 ± 4000 μg−1 as total, and from 570 + 188 to 3000 ± 2000 μg g−1 as acetic acid extractable. In control soils, comparable values were from 170 ± 35 to 320 ± 90 μg g−1 total zinc, and 70±10 to 140 ± 30 μg g−1 acetic acid‐extraetable zinc.
Zinc toxieity is found in such soils causing significant reduction in plant dry weight and tiller production of normal material of A. capillaris.
The pattern of root growth response to increasing zinc concentration in solution culture of samples of adult plants collected from beneath pylons differed significantly.
Some individuals had zinc tolerance equivalent to that of zinc mine plants; others had low but measurable tolerance; others differed little from plants from uncontaminated control sites.

These results clearly show that evolution of zinc tolerance has occurred rapidly, since the pylons sampled were all less than 30 years old, but the outcome is different under different pylons, almost certainly because of differing genetic constitutions of different founding populations.
The role of CO2uptake by roots and CAM in acquisition of inorganic C by plants of the isoetid life‐form: a review, with new data onEriocaulon decangulareL.
Authors: RAVEN JOHN A. , HANDLEY LINDA L. , MACFARLANE JEFFREY J. , MCINROY SHONA , MCKENZIE LEWIS , RICHARDS JENNIFER H. , SAMUELSSON GORAN 
Published: April 2006

SUMMARYThe isoetid life‐form was originally defined on morphological grounds; subsequent physiological investigations showed that all of the isoetids examined took up a large fraction of the inorganic C fixed in their leaves from the root medium under natural conditions, and that some of them carried out much of their assimilation of inorganic C via a CAM‐like mechanism. Root‐dominated uptake of inorganic C appeared to be unique to, and ubiquitous in, the isoetids. I However, a large capacity for CAM‐like metabolism in submerged vascular plants is not universal in isoetids, nor is it restricted to this life‐form, being also found inCrassulaa aquatica.The work described here shows that submerged specimens of the North AmericanEriocaulon decangularehave a high fraction of their dry weight in the root system, a trait characteristic of isoetids but uncommon in other submerged vascular plants.E. decangularehas vesicular‐arbuscular mycorrhizas, as do other flowering plant isoetids hut not, generally, submergedIsoetesspp. Under conditions of natural supply of inorganic C,E. decangulare, like other isoetids, takes up most of its inorganic C through its roots. Uptake of inorganic C by both roots and shoots involves CO2rather than HCO3: photosynthesis at high external pH values does not exceed the rate of uncatalysed HCO3‐to CO2conversion in the medium and there is no detectable extracellular carbonic anhydrase activity.Measurements of titratable acidity and of malate content of leaves sampled at dawn and at dusk showed thatE. decangulare, growing and tested under either emersed or submersed conditions, did not exhibit CAM‐like behaviour. CAM was also absent from three non‐isoetid aquatic macrophytes(Amphibolic antarctica, Eeklonia radiataandVallisneria spiralis)which were examined.E. decangularethus resembles all other isoetids tested in acquiring much of its inorganic C via the root system.E. decangularealso resembles most of the isoetids which are not members of the Isoetaceae (e.g.)E. septangulare, Lobelia dortmannaandSubularia aquatica)but differs from submerged Isoetaceae andLittorella uniflorain lacking CAM.The ecological significance of uptake of CO2via the roots and, where it occurs, of CAM in isoetids may be related to either inorganic C or, via improved N use efficiency, inorganic C as a limiting resource.The isoetid life‐forms has evolved independently in at last five different families of vascular plants; it probably derived fairly immediately from terrestrial or amphibious ancestors with a similar rosette form. Emergent Isoetaceae with acquisition of CO2via roots and CAM probably evolved from submerged isoetids.CONTENTSSummary123I.Introduction126II.Material and Methods127III.Results and Discussion129IV.Conclusions142Acknowledgements142References143
Effects of sulphur dioxide and nitrogen dioxide on the control of water loss by birch (Betula spp.)
Authors: NEIGHBOUR EMILY A. , COTTAM D. A. , MANSFIELD T. A. 
Published: April 2006

SUMMARYThe effects of SO2 and NO2 on the control of water loss by birch trees were investigated using clonal populations of both Betula pendula Roth, (silver birch) and Betula pubescens Khr. (downy birch). Plants were grown in controlled environments and were fumigated in a 2 × 2 factorial experiment with 65 nl l‐1 SO2 and/or NO2, or with equal concentrations of both SO2 and NO2 in four treatments, namely zero, 20, 40 and 60 nl l‐1.Excised leaves showed in increased rate of water loss approximately corresponding to the concentration of pollutant to which they had been previously exposed. When petroleum jelly was applied to the abaxial epidermal surface of polluted leaves the increased rate of water loss was not found, strongly implying that the damage had occurred only at this site, and not on the adaxial epidermis, which is virtually devoid of stomata.Measurements of gas exchange were made on B. pubescens exposed to the four doses of the mixture of the two gases. The rate of transpiration was approximately doubled as a result of the two higher pollution treatments, judging from measurements made later in clean air. When transpiration was measured in high and low CO2 concentrations, polluted plants had a slightly reduced and more variable response to the change in CO2 concentration.Both clones were also exposed first to the four doses of the gas mixture, and then to drought. There was a more rapid onset of water stress, accompanied by an earlier decrease in effective leaf area in the polluted plants, when compared with the unpolluted plants.The abaxial surface of frozen hydrated leaves of the Betula pubescens clone were examined at low temperature with a scanning electron microscope. Damaged epidermal cells were clearly visible on the polluted leaves and thought to be responsible for areas of wide open stomata.It is concluded that leaves of these species are less efficient in the utilization of water after a period of exposure to pollution and are less able to restrict water loss in a time of shortage.
The influence of ozone on the winter hardiness of Norway spruce [Picea abies (L.) Karst.]
Authors: Barnes J. D. , Davison A. W. 
Published: April 2006

SUMMARYThree‐year‐old clonal saplings of Picea abies (L.) Karst. were exposed in chambers to 240μg O3 m‐3 for 70 d, 6hd‐1 and then hardened for 14 d at 4°C day/night. The winter hardiness of trees was tested by subjecting excised shoots, bearing previous and current year's needles, to night temperatures of –6, –9, –12, –15 and – 18°C in a computer‐controlled freezer. No visible injury was observed during the fumigation, hardening period or on the current year's needles of any of the clones. However, during post‐freezing recovery in a mist spray unit four of the clones exposed to ozone developed extensive visible injury on the previous year's needles, in the form of severe, uniform necrosis. The affected needles began to fall prematurely. Induced chlorophyll fluorescence was significantly reduced by O3 in two of the clones that showed post‐freezing injury. This suggested that O3‐induced membrane injury increased the sensitivity of needles to freezing. One clone (no. 4076), which exhibited no effect of ozone on fluorescence kinetics, showed severe ozone‐induced injury of the previous year's needles, developing about 40 d after fumigation independent of temperature. Previous year's needles of O3‐treated plants of this clone showed significantly greater rates of euticular transpiration, so the O3 may have induced gradual desiccation of the needles. The restriction of damage to the older needles of certain clones of Norway spruce is consistent with symptoms of forest decline affecting high‐altitude forests on acid soils. Results indicate that O3 predisposes trees to freezing injury, winter desiccation and drought, and it is proposed that such interactions are important factors contributing to the decline of high‐altitude forests of Norway spruce in Europe.
Adaptation of grasses in the Netherlands to air pollution
Authors: DUECK TH. A. , DIL E. W. , PASMAN F. J. M. 
Published: April 2006

SUMMARYIn three separate experiments, the response of three populations of Agrostis capillaris L., Nardus stricta L., and Lolium perenne L., from areas differing in ambient air pollution concentrations, were examined in experimental fumigations using SO2, O3, NO2 and NH3. Growth of A. capillaris generally increased following the fumigations, except at the highest pollutant concentrations (120 μg m‐3 O3, alone or combined with 150 μg m‐3 SO2 and 35 μg m‐3 NO2). Growth of each population of N. stricta was stimulated by the SO2 and NH3 combination, but was significantly increased only in the populations originating from the most heavily polluted of the three areas. The growth of L. perenne was not inhibited by any air pollutant or combination of pollutants. Despite a low growth rate in clean air and a large amount of within‐population variation, biomass production was significantly stimulated by the highest pollutant mixture.The response of each species to the experimental treatments depended in part on the location from which it originated. This site‐dependent (population) response differed between species, suggesting that the selective processes induced by these air pollutant concentrations were insufficient for a clear‐cut adaptation to gaseous air pollutants.
The structure and function of the vegetative mycelium of ectomycorrhizal plants III. Ultrastructural and autoradiographic analysis of inter‐plant carbon distribution through intact mycelial systems
Authors: DUDDRIDGE J. A. , FINLAY R. D. , READ D. J. , SÖDERSTRÖM B. 
Published: April 2006

SUMMARYPlants of Pinus sylvestris L. were grown in mycorrhizal association with Suillus bovinus (Fr.) O. Kuntze in observation chambers until an interconnecting mycelial network had developed between the seedlings. The shoot of an individual seedling was then scaled in a perspex cuvette and exposed to 14CO2. After incubation for 48 h, the‘donor’shoot was removed and components of the mycelial network and mycorrhizal roots of connected and unconnected‘receiver’seedlings were harvested, fixed, embedded and sectioned prior to being autoradiographed and examined by transmission electron microscopy. The patterns of distribution of 14C‐labelled material within the mycelial strands, the sheath and root tissues was examined. The results are discussed in relation to carbon metabolism of the fungus and of the interconnected host plant.
The mycorrhizal relationship of multinucleate rhizoctonias from non‐orchids with Microtis (Orchidaceae)
Authors: Milligan M. J. , Williams P. G. 
Published: April 2006

SUMMARYMultinucleate rhizoctonias isolated from the roots of non‐orchid plants were used in symbiotic germination tests with seed of 18 orchid species from 10 genera. The rhizoctonias only stimulated germination of Microtis. Investigation of the natural mycosymbionts of adult Microtis failed to yield fungi similar to the original multinucleate rhizoctonias: 27 Microtis plants collected at seven sites in the Sydney region yielded 26 binucleate rhizoctonias tentatively identified as Tulasnella calospora (Boudier) Juel and one very slow growing multinucleate rhizoctonia tentatively identified as Sebacina vermifera Oberwinkler. Fungi closely resembling the original multinucleate rhizoctonias were isolated by baiting the soil with subterranean clover (Trifolium subterraneum L.) plants at three of the seven Microtis sites.
Effects of aluminium on fluoride uptake by plants
Authors: TAKMAZ‐NISANCIOGLU S. , DAVISON A. W. 
Published: April 2006

SUMMABYThe effect of aluminium on the uptake and transport of fluoride by bean (Phaseolus vulgaris L.) was examined by means of water culture. Tomato (Lycopersicon esculentum Mill.) was used in one experiment. Exposing bean roots to NaF led to fluoride concentrations in the roots and first leaves of 47 and 17 times respectively those of controls. In contrast, the same concentration of F given as A1F3 gave concentrations 83 and 68 times respectively those of controls. Both roots and leaves showed an increase in concentration of 042 mol of F for each mol of Al in contrast to the 3:1 molar ratio of F to Al in the A1F., solution. Giving the Al (as A1C13) before NaF also led to significant increases in uptake and transport of F compared with controls. Fluoride was readily washed out of roots whether it was presented as NaF or A1F3. Analysis of xylem exudate of tomato given A1F3 showed that 44 % of the fluoride was associated with metals compared with 4.7% in controls. It was concluded that when F is presented as F−, it remains largely in the apoplast and that it enters the xylem by leaking past the endodermal barrier at the root tip or where laterals emerge. In complexing with Al, the negative charge on the F is neutralized, decreasing Donnan exclusion and therefore leading to a higher concentration of F in the apoplast. The formation of fluoride‐aluminium complexes in plant tissues would be expected to decrease the toxicity of both elements.
The structure and function of the vegetative mycelium of ectomycorrhizal plants IV. Qualitative analysis of carbohydrate contents of mycelium interconnecting host plants.
Authors: SÖDERSTRÖM B. , FINLAY R. D. , READ D. J. 
Published: April 2006

SUMMARYPlants of Pinus spp. were grown in observation chambers with the mycorrhizal fungi Suillus bovinus, Pisolithus tinctorius or Paxillus involutus. After interconnecting mycelial systems had developed between plants, individual hosts in some chambers of each species were fed with 14CO2. Mycelia from radioactively labelled and unlabelled chambers were harvested and their carbohydrates were extracted, separated chromatographically and identified. The major carbohydrates in all of the fungi were trehalose, mannitol and arabitol, their relative proportions differing in the different fungi. The results are discussed in relation both to carbon nutrition of the fungus and to carbon transfer between interconnected plants.
Nuclear DNA content in root cells of Lotus and Trifolium colonized by the VAM fungus, Glomus versiforme
Authors: Blair D. A. , Peterson R. L. , Bowley S. R. 
Published: April 2006

SUMMARYNuclear DNA content of root cortical cells of Lotus pedunculatus Cav., Lotus corniculatus L. and Trifolium pratense L. was determined using a microspectrophotometer. Infected and uninfected roots from plants which had been colonized with the fungus, Glomus versiforme (Daniels and Trappe) Berch and roots from non‐inoculated plants were compared. Relative DNA contents for cortical cell nuclei of the three hosts were within the 2–4C range for uninfected root cells. There was no evidence that the VAM fungus, G. versiforme, induced endoreduplication of cortical cell nuclei during infection of these forage legumes. Nuclear enlargement reported in other studies of VAM colonization is likely to involve mechanisms of nuclear enlargement other than DNA endoreduplication.
Comparative effectivity of three Fraxinus pennsylvanica Marsh, vesicular‐arbuscular mycorrhizal fungi in a high‐phosphorus nursery soil
Authors: LAMAR R. T. , DAVEY C. B. 
Published: April 2006

SUMMARYInoculation of seedlings of green ash (Fraxinus pennsylvanica Marsh.) with vesicular‐arbuscular (YA) mycorrhizal fungi, significantly increased seedling heights, root collar diameters, dry matter accumulations and phosphorus (P) nutrition relative to control seedlings. The ability of these YA mycorrhizal fungi, which were isolated from low‐P forest soils (5–7 mg kg−1), to enhance seedling growth in a high‐P (148 mg kg−1) nursery soil provides evidence for the occurrence of YA mycorrhizal fungi which may be effective under both high and low soil P conditions. There was a significant positive correlation between foliar P concentration and percentage infection. Despite significant differences in tissue P concentrations among seedlings receiving different inoculum treatments, the degree of growth enhancement was the same. Growth increases due to enhanced P nutrition in seedlings with higher concentrations of foliar P may have been offset by an increased drain on host photosynthate via production and maintenance of greater amounts of fungal bomass, or may have been limited by the low K fertility of the nursery soil.Colonization percentages in roots of seedlings of green ash were high despite high soil P concentrations. The pattern of infection development was unique for each YA mycorrhizal fungal species. A modification of the grid‐line intercept technique was used to assess intensity of infection. Infection for all endophytes during the period of most rapid vegetative host growth was predominantly arbuscular. However, arbuscular intensity fluctuated during this period. Vesicles increased in number with time but always made up a small percentage of total infection.
A discrete probability model for polycyclic infection by soil–borne plant parasites
Authors: BRASSETT P. R. , GILLIGAN C. A. 
Published: April 2006

SUMMARYA discrete, theoretical infection model is developed to describe the temporal progress of an epidemic of a soil‐borne pathogen. The model is based upon the probability of escape of host units, such as roots, seeds or entire plants from two sources of inoculum, a primary source, comprising randomly dispersed propagules in soil, and a secondary source derived from infected hosts. A polycyclic sequence of infection is modelled: thus infections derived from soil inoculum serve as sources of infection, giving rise to secondary infections which, in turn, give rise to tertiary infections and so on to the the cycle. The discrete, successive cyclical progression is generalized by the introduction of a parameter for survival of existing infections. The problem of a dynamically varying population of host units is discussed. A simplification of the model is obtained to give a continuous analogue, in which non‐integer values for time replace cycle number. Statistical methods of fitting the model to experimental data are discussed and illustrated by the fit to disease progress curves for the infection and damping–off of cress seedlings, Lepidium sativum L., by Pythium ultimum Trow.