bluuebunny/crossref_metadata_2025_split huggingface dataset:
Occurrence of genets of Armillaria spp. in four mountain forests in Central France: the colonization strategy of Armillaria ostoyae
Authors: LEGRAND PHILIPPE , GHAHARI SEPIDEH , GUILLAUMIN JEAN‐JACQUES 
Published: April 2006

summaryFour forests each of 4–8 ha were investigated in Central France: (1) a pure beech stand harbouring only the saprophytic species Armillaria gallica and A. cepistipes; (2) a pure beech stand with the same species plus A. ostoyae; (3) an ancient beech stand to which conifers had been introduced 60 yr ago, and in which A. ostoyae was becoming the dominant species with A. gallica and A. cepistipes still present; (4) a young pine stand on an old conifer site, where A. ostoyae was exclusive and pathogenic. A total of 764 isolates was obtained from rhizomorphs, fruiting bodies and mycelia from stumps. Mapping of genets of the different Armillaria species was carried out on the four sites by testing for somatic incompatibility. This allowed comparison of the number, area and distribution of the genets of the different species. There was complete overlap of the genets of A. ostoyae with those of A. cepistipes or A. gallica, suggesting different colonization strategies. By contrast, the genets of A. gallica and A. cepistipes overlapped only rarely, suggesting similar colonization strategies. Two different genets of the same species intermingled only in a limited area along their border. In the conifer plantation, A. ostoyae tended to colonize the stumps whereas the other two species prevailed as rhizomorphs in the litter, but the competition was evolving in favour of A. ostoyae. At the fourth site, where the stumps had been uprooted and the pine seedlings had been left to grow, a large number of small genets of A. ostoyae was observed, suggesting recent infection by basidiospores.
A comparison of different methods for the identification of genets ofArmillariaspp.
Authors: GUILLAUMIN JEAN‐JACQUES , ANDERSON JAMES B. , LEGRAND PHILIPPE , GHAHARI SEPIDEH , BERTHELAY SUZANNE 
Published: April 2006

summaryIn a previous study, somatic incompatibility (SI) was used to map the genotypes (or genets) of threeArmillariaspecies(A. ostoyae, A. gallica, A. cepistipes)at four forest sites. A total of 109 genets was identified among 764 isolates of the three species. The object of the present study was to compare SI with three other methods of distinguishing genets: Random Amplified Polymorphic DNAs (RAPD), mating‐type alleles, and isoenzyme analysis. RAPDs and mating‐type alleles were used with 73 isolates belonging to 36 genets identified on the basis of SI reactions. A few isolates were assayed for isoenzyme polymorphism. RAPDs, mating‐type alleles, and SI were equal in their ability to distinguish genets in the populations tested. In three cases, isolates distinguished by SI reactions included two subgroups with different RAPD phenotypes. In two cases groups distinguished by different SI reactions shared the same set of mating‐type alleles. Isoenzyme analysis showed interspecific differences and a few differences between the genets of the same species. These results validate the use of SI as a routine method for epidemiological studies ofArmillariaspp.TheEcoRI fragment profiles of mitochondrial DNA of the same group of isolates were also assayed. The analysis regrouped the genets into ‘mitochondrial types’ sharing a common cytoplasm and possibly closely related to one another through sexual reproduction. Each mitochondrial type consisted of one to five different genets.
Effects of phosphorus and ectomycorrhiza on maritime pine seedlings (Pinus pinaster)
Authors: CONJEAUD C. , SCHEROMM P. , MOUSAIN D. 
Published: April 2006

summaryThe purpose of this study was to determine how ectomycorrhizal infection and phosphorus nutrition affect biomass, photosynthesis and root respiration in the host plant. Maritime pine (Pinus pinasterSoland.inAit.) seedlings grown in containers filled with perlite–vermiculite were inoculated with the ectomycorrhizal fungusHebeloma cylindrosporum(strain D3.25.9) and given 0 or 0.5 mM phosphate in the nutrient solution.Hebeloma cylindrosporuminfection increased net photosynthesis and root respiration rates compared with those of non‐mycorrhizal plants, but there was an accompanying 35 % depression in growth. The addition of phosphorus to non‐mycorrhizal plants induced a rise in tissue phosphorus content which made them similar m that respect to mycorrhizal plants but did not result in increased photosynthesis. The nitrogen content of mycorrhizal plants was, moreover, lower than that of the control group. The data recorded were consistent with the photosynthate source‐sink hypothesis. The increase in fixed carbon in mycorrhizal plants was unable to compensate for the increased carbon cost of the mycorrhizal root system.
An experimental study of growth in relation to morphology and shoot water content in maritime Antarctic mosses
Authors: FOWBERT J. A. 
Published: April 2006

summaryThe dependence of shoot growth and growth form on water availability was studied experimentally in six species of maritime Antarctic moss. Under all conditions the largest growth increments were observed in the hydric species Brachythecium austro‐salebrosum and Drepanocladus uncinatus. The xeric Andreaea depressinervis grew the least. Lateral shoot production varied within and between species. Over 50 % of the biomass produced in D. uncinatus was derived from lateral shoot production, whereas Polytrichum alpestre produced very few lateral shoots and A. depressinervis produced none. Leaf density and leaf size also varied with total water content.In all species growth ceased at total water contents of 100% d. wt or less. However, the total water content at which maximum growth was observed differed between species. Racomitrium austro‐georgicum (mesic/xeric) had the lowest optimum for growth at 370% of d. wt and D. uncinatus (hydric) exhibited maximum growth between 890 and 2300% d. wt. Optimum total water contents for growth were greater than those at full turgor and published optima for net assimilation.Growth and total water content of these Antarctic mosses were similar to those reported for temperate species.
A molecular characterization of the Gunnera–Nostoc symbiosis: comparison with Rhizobium– and Agrobacterium– plant interactions
Authors: RASMUSSEN ULLA , JOHANSSON CHRISTINA , RENGLIN ANNA , PETERSSON CARL , BERGMAN BIRGITTA 
Published: April 2006

summaryThe Gunnera‐Nostoc symbiosis is a N2‐fixing endosymbiosis between an angiosperm and a prokaryote, in some respects showing similarities to legume‐rhizobial symbioses as well as to pathogenic Agrobacterium‐plant interactions. We here describe the results of a molecular comparison of these systems, along with a characterization of the Gunnera mucilage which is important for Gunnera–Nostoc communication. Nostoc DNA sequences homologous to the rhizobial nodEF, nodMN, exoY genes, along with the nod box, were identified by heterologous hybridization, whereas no homologues to either nodABC, nodD1 or nodD2 were found. Nevertheless, no anti‐Nod protein antibodies recognized any Nostoc protein, either in normally grown or mucilage‐induced cells. Furthermore, probes containing the agrobactenal chvA, chvB and picA genes also hybridized with Nostoc DNA, whereas virA and virG genes did not.Using rhizobia with nod gene–lacZ fusions as reporters, Gunnera mucilage and seed rinse were shown to possess nod gene‐inducing activity.The mucilage secreted by the Gunnera stem gland, the organ susceptible to Nostoc infection, was composed of arabinose and galactose in relative molar proportions of 1.00:0.25, with an additional 0.13 molar parts of glucuronic acid. It showed a reaction on dot blot assays with the arabinogalactan protein‐specific monoclonal antibody MAC 207, indicating that it contains arabinogalactan proteins.
Phragmites die–back: bud and root death, blockages within the aeration and vascular systems and the possible role of phytotoxins
Authors: ARMSTRONG J. , ARMSTRONG W. , VAN DER PUTTEN W. H. 
Published: April 2006

summaryDie‐back and healthy stands of Phragmites australis (Cav.) Trin. ex Steud in the UK and Hungary were compared in terms of stand architecture, plant morphology and anatomy, sediment redox potential and sulphide levels, plant resistance to internal Poiseuille gas flow, and convective flow characteristics of culms. Compared with healthy sites, die‐back sites were characterized by lower sediment redox potentials, and in Hungary by very high sulphide levels. Plants at die‐back sites showed a markedly clumped distribution, with fewer new shoots and fewer old flower heads than those at healthy sites, a high incidence of dead and decaying rhizomes and roots, and dead ‘overwintering’ and ‘growing season’ buds, and occasional prematurely senesced culms. Dead and stunted adventitious roots with short peg‐like laterals were very common, and there was abnormal lignification and suberization within the cortex and epidermis/hypodermis of adventitious root apices, and in the epidermis of lateral roots. Callus was found blocking the internal aeration pathways in root aerenchyma, root‐rhizome junctions, rhizome nodes and the bases of buds and culms. Blockages of the vascular elements of both xylem and phloem in rhizomes and roots were also common. At the die‐back sites, callus accounted for a greater resistance to gas flow from the dead aerial culms into the rhizome system. Compared with healthy culms, prematurely senesced culms from die‐back sites exhibited smaller potentials for aerating the rhizome system by humidity‐induced convection.It is suggested that die‐back in Phragmites might be brought about and perpetuated at least partly by phytotoxins which induce (a) blockages within the aeration pathways due to callus development, (b) stunting of roots and the development of abnormal root wall lignification and suberisation causing interference with water and mineral absorption, and (c) internal blockages causing interference with vascular transport. A tentative scheme for Phragmites die‐back is presented.
Waterlogging and survival in Sesleria albicans
Authors: DIXON JEAN M. 
Published: April 2006

summaryThe performance of Sesleria albicans Kit. ex Schultes, a species usually found in dry limestone habitats, but also recorded in wet places, was examined over a period of 2 yr along a soil‐water gradient. This supplied a ‘dry’ end with the water‐table 22 cm below the surface, grading to a ‘wet’ end with the water‐table at the surface, providing static waterlogged conditions. The performance of plants (judged from measurements of tussock diameter, plant height, panicle length, counts of the number of panicles and spikelets per panicle, and shoot and root d. wt) was progressively impaired with increasingly waterlogged conditions. Previously waterlogged ramets recovered when removed to non‐waterlogged soil, showing that waterlogging had stunted but not killed the roots.The effects of waterlogging were demonstrated by a pot experiment to be similar in three different types of soil. Differences in the performance of S. albicans in these (determined by counts of the number of tillers, number of nodal axes and measurements of leaf length, root length, and shoot and root d. wt) were a result of factors other than waterlogging, since the differences were maintained in both waterlogged and normally watered soil.Although performance of S. albicans was adversely affected in static waterlogged soils, none of the plants died, even after 2 yr. Possible explanations for the survival of S. albicans were sought.
The role of mycorrhizas in the response ofPinus taedaseedlings to elevated CO2
Authors: LEWIS J. D. , STRAIN B. R. 
Published: April 2006

summaryThe effects of mycorrhizal status, phosphorus supply and CO2, partial pressure on production and allocation of biomass in seedlings from two populations ofPinus taedaL. were examined. Seedlings from a North Carolina and a Florida population were grown in sterile soil in a full‐factorial experiment with one of two phosphorus treatments (low P, high P) and at one of two CO2partial pressures (35.5, 71.0 Pa). One half of the seedlings were inoculated withPisolithus tinctorius(Pers.) Coker & Couch hyphae and spores. Seedlings were harvested 60, 90 and 120 d after emergence. Elevated CO2significantly increased total seedling dry mass in all treatments at all three harvests. Phosphorus limitation reduced seedling growth, and mycorrhizas increased seedling growth in seedlings limited by phosphorus supply. Generally, however, there were no interactions between CO2, phosphorus supply and mycorrhizal status on dry mass of seedlings. Mycorrhizas probably did not affect the response of dry mass to elevated CO2, because phosphorus limitation did not reduce response of dry mass to elevated CO2, Phosphorus‐limited seedlings responded to elevated CO2, as a result of increased phosphorus uptake, resulting from increased total root dry mass, and increased phosphorus use efficiency. Although mycorrhizal colonization did not affect the response of biomass to elevated CO2, it significantly reduced the response of needle area. As a result, specific leaf area (leaf area per unit plant biomass) was lower in mycorrhizal seedlings grown in elevated CO2than in mycorrhizal seedlings grown in ambient CO2Because there were no effects on relative growth rate or seedling dry mass, reductions in specific leaf area suggest that elevated CO2reduced the relative cost of the symbiosis.
Facilitation of plant phosphate acquisition by arbuscular mycotrhizas from enriched soil patches
Authors: CUI MUYI , CALDWELL MARTYN M. 
Published: April 2006

summaryMycorrhizal contribution to nutrient acquisition from spatially heterogeneous soil was investigated using two‐way comparisons of non‐mycorrhizal and arbuscular mycorrhizal Agropyron desertorum (Fisch. ex Link) Schult. in soil with either a patchy or a uniform nutrient distribution. Double‐labelling allowed a comparison between acquisition of an ion of lower abundance and mobility, phosphate (P), and an ion of higher abundance and mobility, nitrate. As expected, root density increased in enriched‐nutrient patches relative to either unenriched soil or to soil where the same quantity of nutrients was applied to the entire soil volume (uniform‐nutrient treatment). However, the increase of local root density in patches was less for mycorrhizal plants than for non‐mycorrhizal plants. Mycorrhizal infection enhanced plant acquisition of labelled P relatively more in the enriched patches (patchy‐nutrient treatment) than in soil with uniform nutrient distribution, both when expressed on a shoot mass and on a root‐length basis. As expected, plant nitrate acquisition and shoot nitrogen concentration were not significantly affected by either mycorrhizal infection or patterns of soil nutrient distribution. Hence, arbuscular mycorrhizas can enhance root P acquisition and, thus, contribute to plant exploitation of soil P heterogeneity.
Facilitation of plant phosphate acquisition by arbuscular mycorrhizas from enriched soil patches
Authors: CUI MUYI , CALDWELL MARTYN M. 
Published: April 2006

summaryEffects of arbuscular mycorrhizas (AM) on plant exploitation of soil nutrient heterogeneity were studied with non‐mycorrhizal and mycorrhizal Agropyron desertorum (Fisch. ex Link) Schult. in two‐compartment containers. A central cylindrical plant compartment was separated from an outer hyphal compartment by two layers of stainless‐steel screen with a 2 mm air gap between the screen layers. Patchy or uniform nitrate (NO2−) and phosphate (P) distribution patterns were created in the outer compartment. Only AM hyphae could cross the double‐screen barrier to access those nutrients. Mycorrhizal plants acquired significantly more labelled P in both the patchy‐ and the uniform‐nutrient treatments than did non‐mycorrhizal plants. Mycelia in root‐free soil delivered similar amounts of P from the more distant rich patches to mycorrhizal plants as from the uniform and more proximate labelling. The uptake of a more mobile and abundant element, nitrate, was not affected significantly by either mycorrhizal infection or by nutrient distribution patterns in the root‐free soil. Despite a lower root:shoot mass ratio, mycorrhizal plants had significantly greater shoot phosphorus concentration than did nonmycorrhizal plants. There was no significant difference in P uptake or phosphorus concentration between the two nutrient distribution patterns for mycorrhizal plants, indicating that AM hyphae can explore the root‐free soil for available P and transport it to host plants equally well when P was distributed in either patchy or uniform patterns in the root‐free soil.
Growth and mineral nutrition of non‐mycorrhizal and mycorrhizal Norway spruce (Picea abies) seedlings grown in semi‐hydroponic sand culture
Authors: ELTROP LUDGER , MARSCHNER HORST 
Published: April 2006

summaryGrowth, nitrogen uptake and mineral nutrient concentrations in the plant tissues were determined in non–mycorrhizal and mycorrhizal Norway spruce (Picea abies (L.) Karst.) seedlings grown under controlled conditions in a semi‐hydroponic culture system with quartz sand as substrate and a percolating nutrient solution. The culture system allowed the determination of nutrient uptake rates in mycorrhizal root systems with an intact extramatrical mycelium. The rate of infection of the roots by the mycorrhizal fungi Pisolithus tinctorius and Laccaria laccata was high but the rate of infection by Paxillus involutus was low.When supplied with ammonium nitrate, the d. wt of the roots and particularly of the shoots was significantly lower in mycorrhizal than in non–mycorrhizal plants. Despite the lower root d. wt, the number of root tips and the root branching ratio (number of root tips per unit root length) were significantly higher in mycorrhizal plants infected with L. laccata and P. tinctorius than in non–mycorrhizal plants. The depletion of ammonium in the external solution was faster than the depletion of nitrate. Nitrate uptake rates increased at ammonium concentrations below 400μM. The maximal N uptake rates (Vmax), calculated after Lineweaver–Burk, were significantly higher for ammonium than for nitrate. The N uptake rates did not differ significantly between non–mycorrhizal and mycorrhizai plants. The concentrations of N, P, K, Ca and Mg tended to be higher in the smaller mycorrhizal than in the larger non–mycorrhizal plants. A significant increase in mineral nutrient concentration in mycorrhizal compared with non–mycorrhizal plants was found only for N concentrations in the needles of mycorrhizal plants infected with P. tinctorius.When they were supplied with ammonium ((NH4), SO4) as source of N, but not when they were supplied with nitrate (KNO3), the d. wt was lower in mycorrhizal plants infected with P. tinctorius than it was in non‐mycorrhizal plants. Therefore, N uptake rates were increased in mycorrhizai plants with P. tinctorius only when they were supplied with ammonium but not with nitrate.The insignificant differences in uptake rates of N, P, K, Ca and Mg between non–mycorrhizal and mycorrhizal plants indicate that at unlimited spatial nutrient availability the contribution of the extramatrical mycelium to nutrient uptake by mycorrhizal plants was small. It is suggested that the decreased growth of mycorrhizal plants is due to the demand of the mycorrhizal fungus for photosynthates, i.e. source limitation.
Growth and mineral nutrition of non‐mycorrhizal and mycorrhizal Norway spruce (Picea abies) seedlings grown in semi‐hydroponic sand culture
Authors: ELTROP LUDGER , MARSCHNER HORST 
Published: April 2006

summaryIn seedlings of Norway spruce(Picea abies(L.) Karst.), grown in semi‐hydroponic sand culture, mycorrhizal infection decreased growth (Eltrop & Marschner, 1996). Possible reasons for this growth depression were investigated in the present study by comparing the plant and fungal biomass distribution and carbon partitioning between non‐mycorrhizal and mycorrhizal(Pisolitlius tinctorius)plants supplied with ammonium or nitrate as source of N.Despite the high mycorrhizal infection rate (55–71% of total root tips), the amount of fungal biomass in roots and extramatrical mycelium of mycorrhizal plants accounted for less than 3% of plant dry matter and was significantly lower in nitrate‐ than in ammonium‐supplied plants.The CO2assimilation rates were higher in mycorrhizal than in non‐mycorrhizal plants supplied with ammonium as well as those supplied with nitrate. High light intensity considerably increased CO2assimilation rates. The respiration rates of the intact root systems were significantly increased in ammonium‐supplied mycorrhizal plants compared with non‐mycorrhizal plants. The amount of CO2lost in root respiration as a percentage of the amount of CO2gained in photosynthesis (respiratory quotient), ranged from 49.3% at 30°C root zone temperature and low light intensity (290 μmol m−2S−1) to 11.7% at 10 °C and high light intensity (990 μmol m−2s−1). In ammonium‐supplied plants grown at 22 °C and low light intensity, the proportion of carbon lost by root respiration was significantly higher in mycorrhizal than in non‐mycorrhizal plants. This increase in root respiration was of the same order of magnitude (7.4 %) as the decrease in dry matter production by mycorrhizal plants (10.1 %). In nitrate‐supplied plants, no significant difference in the respiratory quotient was found between non‐mycorrhizal and mycorrhizal plants. The respiration rate per unit d. wt of the fungal mycelium was estimated to account for 31.3 % (ammonium supply) and 8.3 % (nitrate supply) of that of the total mycorrhizal root system although the dry weight accounted for only 4. % (ammonium supply) and 2.5 % (nitrate supply). Accordingly, the respiration rate was calculated to be 11.1 times higher with ammonium supply, and 3.4 times higher with nitrate supply, than that of the root tissue. The carbohydrate concentrations in shoots and roots were not consistently different between non‐mycorrhizal and mycorrhizal plants.It was concluded that increased root respiration was mainly responsible for the growth reduction in mycorrhizal compared with non‐mycorrhizal plants, whereas the production of fungal biomass in the extramatrical mycelium of mycorrhizal plants was of minor importance.
The effect of long‐term ozone fumigation on the growth, physiology and frost sensitivity of Calluna vulgaris
Authors: FOOT J. P. , CAPORN S. J. M. , LEE J. A. , ASHENDEN T. W. 
Published: April 2006

summary Calluna vulgaris (1) Hull, plants were fumigated in open‐top chambers with ambient charcoal‐filtered air, or 70 nl 1−1 (70 ppb) ozone, for 8 h a day, five days a week. Ozone treatment during the winter increased the frost sensitivity of plants as measured by electrolyte leakage following a controlled frosting regime. Root growth was decreased and the allometric root‐.shoot ratio (k) was reduced by the ozone treatment, reflecting a decrease in the partitioning of carbon to the roots. There was no significant effect of ozone on instantaneous net photosynthesis. There was a significant increase in anthocyanin content in ozone‐fumigated plants, but no effect on chlorophyll content. In contrast with the effects of wintertime exposure, plants treated during summer showed no significant responses. These results suggest that Calluna vulgaris can be adversely affected by prolonged ozone episodes in the field, particularly if these are followed by or coincide with frosting temperatures.