bluuebunny/crossref_metadata_2025_split huggingface dataset:
Allocation of biomass and mineral elements in Melilotus segetalis (annual sweetclover): effects of NaCl salinity and plant age
Authors: ROMERO J. M. , MARAÑÓN T. 
Published: April 2006

summaryThe allocation of biomass and mineral elements (Ka, K, Ca, P, N, Fe, Cu, Mn and Zn) during the ontogenetic cycle of annual sweetclover (Melilotus segetalis (Brot.) Ser.) growing under favourable and saline conditions has been studied. Plants were grown in a glasshouse, in pots with siliceous substrate and watered with Hoagland solution. Half were salinized by adding 170 mol m−2N2Cl (15 dS m−1) to the solution. Eleven harvests at 15 d intervals measured the dry weight distribution within the plant and the mineral composition. Allocation relative to biomass (ARB) in each plant organ, both under favourable and salt‐stress conditions, was calculated for each mineral element, Biomass and mineral elements were allocated independently within M. segetalis, and the general pattern thanked with age and was affected by salinity. Salt‐stressed plants were smaller and invested proportionately more biomass in leaves. Na was accumulated in roots of young plants and excluded from leaves and fruits, whereas K was depleted from roots and accumulated in leaves and fruits. Immobile Ca accumulated in leaves, with age. Phloem‐mobile P and X were translocated to flowers and fruits. Fe, Cu and Zn were diluted in leaves and not affected by salt; whereas Mn concentration increased with age and salinity. The switch to reproduction and increased demand for nutrients induced drastic changes in the allocation pattern of mineral elements. Salinity induced a re‐allocation of biomass and mineral elements in all plant organs except the reproductive structures, as part of a whole‐plant response to minimize salt toxic effects, to achieve osmotic adjustment, to preserve the reproductive output, and to compensate nutrient imbalance.
The effect of fungicides on vesicular‐arbuscular mycorrhizal symbiosis
Authors: SUKARNO N. , SMITH F. A. , SMITH S. E. , SCOTT E. S. 
Published: April 2006

summaryTwo experiments were conducted under controlled environmental conditions to determine the effects of the three fungicides, Benlate®. Aliette® and Ridomil®, on efficiency of P uptake from the soil and transfer across the living plant‐fungal interface‐ of onion plants (Allium cepa L.) associated with Glomus sp. ‘City Beach’ (WUM 16), P applied to the soil did not apparently increase the rate of transfer (flux) of P to the plant via the fungal partner of the mytorrhiza.Benlate reduced P inflow and transfer across the interface in one of the experiments. The rate of P uptake per m living external hyphae was not affected but, as development of living external hyphae in the soil was reduced, the contribution of the fungus to P uptake was small. Aliette reduced growth of both shoots and roots, but apparently increased the accumulation of P in the tissues compared with controls. Ridomil reduced P inflow per m of root and P uptake per m living external hyphae, hut had no effect on the rate of P transfer across the interface. This led to a reduction in the overall contribution of the fungus to P nutrition.
Direct measurement of release and assimilation of ammonia in the Gunnera–Nostoc symbiosis
Authors: SILVESTER WARWICK B. , PARSONS RICHARD , WATT PETER W. 
Published: April 2006

summaryIn Gunnera, Nostoc cells invade secretory tissue forming well defined symbiotic areas within the stems and are termed internal nodules (Silvester, 1976). Excised, but intact, internal stem Nostoc nodules taken from Gunnera magellanica show light‐stimulated nitrogenase activity and release a small, but measurable, proportion of their current N2 fixation as NH3 into the external solution. When nodules are disrupted and Nostoc extracted anaerobically, 90% or more of the estimated N2 fixation is released from the Nostoc cells as NH3 into the surrounding medium. Use of 15N2 confirmed that only 12% of N2 fixed is retained within the cells of Nostoc. The remaining 88% was identified as NH3 released outside the cells. Within the intact nodule system, 15N2 uptake showed that 2–5% of recently fixed N2 remains within the Nostoc cells and up to 30% of extracellular N is in asparagine after 1 h. Evidence is presented that stimulation of nitrogenase by light in the intact Gunnera/Nostoc system produces more NH3 than can be assimilated by the host cells, resulting in significant NH3 accumulation.
Carbonic anhydrase(s) associated with lichens: in vivo activities, possible locations and putative roles
Authors: PALMQVIST KRISTIN , BADGER MURRAY R. 
Published: April 2006

summaryThe activity of the enzyme carbonic anhydrase (CA; E.C. 4.2.1.1) was examined in eight species of lichen in vivo by measurements of 18O exchange from doubly labelled CO2 (13C18O18O) to water, with the aim of determining whether this enzyme is present in lichens and if so to what extent it participates in physiological processes. The lichens were chosen to represent different mycobiont (Heterodera, Leptogium, Lobaria, Peltigera, Pseudocyphellaria, Xantoparmelia) and photobiont (Coccomyxa, Dictyochloropsis, Myrmecia, Nostoc, Trebouxia) genera as well as varying morphology. All lichens were found to possess considerable activity of CA, which varied by a factor of about four between the species when compared on a chlorophyl basis, and by u factor of about 10 when related to the weight. Incubation of lichen tholli with ethoxyzolamide (EZA) and acetazolamide (AZA), which inhibit intracellular and extracellular CA respectively, showed that intracellular CA was present in all of the species. Incubation with EZA also resulted in inhibition of photosynthetic CO2, uptake in all species suggesting a role of internal CA in the CO2, acquisition process in all the investigated photobiont genera. A part of the CA activity was inhibited by AZA in all except two of the four cyanobacterial Nostoc lichens, indicating the possible presence of extracellular forms of CA. This CA also appeared to be involved in the acquisition of CO2, as AZA inhibited photosynthetic CO2 uptake in these lichens. The CA inhibitors also affected CO2 efflux in the dark, i.e. fungal respiration, which was inhibited by both AZA and EZA in six of the species, suggesting that a proportion of the CA activity might be located in the mycobiont.
Potential effects of rising tropospheric concentrations of CO2 and O3 on green‐algal lichens
Authors: BALAGUER LUIS , VALLADARES FERNANDO , ASCASO CARMEN , BARNES JEREMY D. , DE LOS RIOS ASUNCION , MANRIQUE ESTEBAN , SMITH ELIZABETH C. 
Published: April 2006

summary Pormelia sulcata Taylor was used as a model to examine the effects of elevated CO2 and/or O3 on green algal lichens. Thalli were exposed for 30 d in duplicate controlled‐environment chambers to two atmospheric concentrations of CO2 (‘ambient’ [350μmol mol−1] and ‘elevated’ [700μmol mol−1] 24 h d−1) and two O3 regimes (‘non‐polluted’ air [CF, < 5 nmol mol−1] and ‘polluted’ air [15 nmol mol−1overnight rising to a midday maximum of 75 nmol mol−1]), in a factorial design. Elevated CO2, or elevated O3 depressed the light saturated rate of CO2, assimilation Asat) measured at ambient CO2, by 30% and 18%, respectively. However, despite this effect ultrastructure) studies revealed increased lipid storage in cells of the photobiont in response to CO2‐enrichment. Simultaneous exposure to elevated O3 reduced CO2‐induced lipid accumulation and reduced Asat in an additive manner. Gold‐antibody labelling revealed that the decline in photosynthetic capacity induced by elevated CO2and/or O3 was accompanied by a parallel decrease in the concentration of Rubiscoa in the algal pyrenoid (r= 0.93). Interestingly, differences in the amount of Rubisco protein were not correlated with changes in pyrenoid volume. Measurements of in vivo chlorophyll‐fluorescence induction kinetics showed that the decline in Asat induced by elevated CO2, and/or O2, was not associated with significant changes in the photochemical efficiency of photosystem (PS) II. Although the experimental conditions inevitably imposed some stress on the thalli, revealed as a significant decline in the efficiency of PS II photochemistry, and enhanced starch accumulation in the photobiont over the fornication period, the study shows that the green‐algal lichen symbiosis might be influenced by future changes in atmospheric composition. Photosynthetic capacity, measured at ambient CO2, was found to be reduced after a controlled 30 d exposure to elevated CO2, and/or O3 and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal chloroplasts.
Nickel‐accumulating plants from the ancient serpentine soils of Cuba
Authors: REEVES R. D. , BAKER A. J. M. , BORHIDI A. , BERAZAÍN R. 
Published: April 2006

summaryExtraordinary uptake of nickel (Ni), reaching concentrations of 0.1–5.0%, c. 1000 times greater than those usually found in flowering plants, has been observed previously in c, 190 species that grow on Ni‐rich serpentine soils derived from ultramafic rocks in various parts of the world. These so‐called hyperaccumulators of Ni include c. 50 species from the rich ultramafic flora of New Caledonia and c. 80 species from the Brassicaceae of Mediterranean Europe and Turkey. A study of a limited part (the families Buxaceae and Euphorbiaceae) of the very large ultramafic flora of Cuba has now identified this as the home of at least 80 hyperaccumulators, the largest number jet found in any one country. The more frequent incidence here of this unusual form of plant behaviour is linked to the very long period (r. 10–30 million years) during which some of the Cuban ultramafic substrata are believed to have been continuously available for colonization; the distribution of Ni hyperaccumulators between older and younger ultrarnafic soils in Cuba mirrors the overall incidence of endemic species in these areas.
Availability of organic and inorganic phosphorus compounds as phosphorus sources for Carex species
Authors: PÉREZ CORONA M. E. , VAN DER KLUNDERT I. , VERHOEVEN J. T. A. 
Published: April 2006

summaryInorganic phosphates (ferric phosphate, calcium phosphate and aluminium phosphate) and organic forms of phosphorus (inosito) hexaphosphate and β‐glycerophosphate) were tested as phosphorus (P) sources for the growth of three Carex species from fens differing in productivity‐ and nutrient availability. Aluminium phosphate and β‐glycerophosphate were equally effective sources of P for all three Carex species as KH2PO4, which was used as a control treatment. Phosphorus from ferric phosphate and calcium phosphate was also taken up bv Carex acutiformis Ehrh., a species of high productivity from eutrophic fen areas, but not by the other two species. Only Carex lasiocarpa Ehrh., a species from P‐limited fens, showed a higher P‐uptake when grown with inositol phosphate than in the second control treatment without P. The P‐source also affected, with differences between species, the biomass allocation to the below‐ground plant parts and the area of absorption surface of the roots.The mobilization of organic sources of P by fen Carex species found in the present study might be an important factor in the P dynamics of fens because of the high contents of organic P in the fen peat soils where these species grow. In the same way, the utilization of inorganic sources of P can play a relevant role in the P‐cycle in these systems where the discharge of ground water rich in ions can lead to the fixation of P into inorganic compounds. However, the differing abilities of the various Carex species to mobilize P from P‐pools does not explain clearly their preferential presence in different fens in relation to the P‐availability.
Plant‐affecting streptomycin‐sensitive micro‐organisms in barley monoculture soils
Authors: OLSSON STIG , ALSTRÖM SADHNA 
Published: April 2006

summarySoils from barley monoculture and from crop‐rotation plots of three long‐term field experiments were tested for their effects on barley growth in the glasshouse, using plant growth tubes. Test plants of young barley developed significantly shorter and thinner root axes when grown in soil from monoculture plots than when grown in soil from crop rotation plots, but the difference in shoot growth was only small. Addition of small doses of streptomycin sulphate neutralized the retarded root growth in soil from monoculture plots, whereas the fungicide metalaxyl induced no such effect. The difference in root growth of barley test plants could be transmitted into a soil‐free root environment by inoculation with the microflora from roots grown in soil. These findings indicate that some component(s) of rhizosphere bacteria is the causal agent of the early monoculture effect measured.
The roles of internal iron hydroxide precipitation, sulphide toxicity and oxidizing ability in the survival of Stratiotes aloides roots at different iron concentrations in sediment pore water
Authors: SMOLDERS A. J. P. , ROELOFS J. G. M. 
Published: April 2006

summary Stratiotes aloides L. is an aquatic macrophyte that occurs in waters on reduced peaty sediments which have a relatively narrow range of free‐iron content in the sediment.Comparison of different aquatic macrophytes reveals that species from reducing sediments have much lower oxidizing ability than do species from oxidizing sediments. Compared with those other species from reducing sediments, the oxidizing ability of Stratiotes aloides is very low and probably makes the species very vulnerable to sulphide toxicity and internal precipitation of iron hydroxide.Apoplastic iron contents were determined for Stratiotes roots growing in sediments with different free‐iron concentrations. Roots collected from sediment with a low free‐iron content appeared to have a relatively low apoplastic‐iron content whereas roots from sediments with a relatively high free‐iron concentration had a relatively high apoplastic‐iron content. In sediments with low free‐iron levels, sulphide levels are generally high.Using light microscopy, iron hydroxide precipitates were observed around the endodermis and cortical air spaces of the roots of Stratiotes aloides growing in iron‐rich sediments. Internal iron oxidation outside the endodermis can prevent iron toxicity inside the stele and thus enable root apices to survive. The root hairs, however, die because of iron hydroxide precipitation at their base; the dead roots have the highest visible iron hydroxide content. Excessive internal iron hydroxide precipitation and the consequential early death of the roots probably explains the absence of Stratiotes aloides in locations with high free‐iron levels in sediment pore water.
Spatial heterogeneity of soil water around single roots: use of CT‐scanning to predict fungal growth in the rhizosphere
Authors: GROSE M. J. , GILLIGAN C. A. , SPENCER D. , GODDARD B. V. D. 
Published: April 2006

summaryWhole‐body computed tomography X‐ray scanning (X‐ray CT) of wheat, cotton and radish growing in pots containing 350 g of a white sand: clay mixture produced images from which digital data of the volumetric water content were obtained. The volumetric water contents were spatially heterogeneous around the root and altered with the depth at which the image was taken. Data represent a ‘snapshot in time’ of the soil around single roots in a living soil–plant system.The volumetric water contents of soil around seedlings were assessed for the growth of two soil‐borne fungi, Gaeumannomyces graminis var. tritici and Rhizoctonia solani. The heterogeneity of water content was biologically significant: water contents around the roots of wheat, radish and cotton were of a great enough range to suggest the existence of heterogeneous sites in the rhizosphere which might favour or restrict fungal growth. In soil surrounding wheat roots, the most favourable regions for the growth of G. graminis were nearest the root, suggesting that the inner rhizosphere might be more amenable to the growth of this pathogenic fungus than the outer region of the rhizosphere, and the bulk soil.The technique of X‐ray CT enables spatial examination of the response of soil water to environmental treatments of the soil–root system, and the non‐destructive observation of the effect of the spatial heterogeneity of volumetric water content upon fungal growth in the soil, over time and at a range of depths.
Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungusGlomus intraradicesgrown in monoxenic culture
Authors: BAGO B. , VIERHEILIG H. , PICHÉ Y. , AZCÓN‐AGUILAR C. 
Published: April 2006

summaryThe effect of the extraradical mycelium of the arbuscular mycorrhizal (AM) fungusGlomus intraradicesSmith & Schenck on nitrate uptake and on the pH of the medium was studied in a monoxenic culture with tomato(Lycopersicon esculentumMill. var. Vendor) roots obtained from root organ culture. The symbiosis was established in compartmented Petri dishes containing agar media amended with the pH indicator bromocresol purple. A pattern of pH changes was revealed as the symbiosis progressed in the media of the Petri dish compartments containing the dual, arbuscular‐mycorrhizal fungi/root, culture as well as in the media of the hyphae, root‐free compartments, in which the extraradical hyphae developed extensively, coming from the compartment containing the symbiosis. The colour changes in the media were measured spectrophotometrically, whilst maintaining the monoxenic conditions. The extraradical hyphae ofG. intraradicesstrongly increased the pH of nutrient‐free medium when supplied with nitrate, whereas the pH decreased m the absence of this N source. The hyphae developing from germinated spores and growing in axenic, nitrate‐amended media did not induce any increase in pH. Nitrogen analysis revealed that a depletion of nitrate in the media accompanied increased pH.These results point towards an active uptake of nitrate by the extraradical mycelium ofG. intraradices, probably coupled to a H+‐symport mechanism. The pH changes induced by AM fungal hyphae and the possible influence of the establishment of a functional symbiosis on these pH changes are discussed.
A comparative study of phenolic acids associated with cell walls and cytoplasmic extracts of host and non‐host roots for AM fungi
Authors: NAGAHASHI GERALD , ABNEY GLORIA D. , DONER LANDIS W. 
Published: April 2006

summaryCarrots (Daucus carota L.) are a ubiquitous host for arbuscular mycorrhizal fungi whereas sugar beets (Beta vulgaris L.) are a non‐host. Root cultures were used to compare the constitutive phenolic compounds associated with the cell wall or present in the cytoplasm of the host and non‐host. Phenolic acids were released from purified cell walls by alkaline hydrolysis and were separated and identified by HPLC, TLC and u.v. absorption spectra analyses. Two phenolic acids unique to carrot root cell walls were identified as p‐hydroxybenzoic acid (p‐HBA) and vanillic acid. Sugar beet root cell walls had ferulic acid as major constituent and contained several unique phenyl propanoids which were not identified. Caffeic acid was found only in the cytoplasm of carrot roots and was present in the conjugated form (chlorogenic acid). The sugar beet cytoplasm also contained several unidentified hydroxycinnamic acid‐type phenolics which were not found in carrot roots.
Effects of a mycophagous Collembola on the symbioses betweenTrifolium subterraneumand three arbuscular mycorrhizal fungi
Authors: LARSEN JOHN , JAKOBSEN IVER 
Published: April 2006

summaryWe examined the effect of the mycophagous CollembolaFolsomia CandidaWillem on the symbioses betweenTrifolium subterraneumL. and three arbuscular mycorrhizal (AM) fungi. Mycorrhizal and non‐mycorrhizal plants were grown in pots with a central mesh bag which constituted a root‐free soil compartment (RFSC) where the soil was labelled with32P. This allowed us to study hyphal P transport as affected by the presence of Collembola in the soil with roots. The hyphal P transport was monitored by measuring the32P content in leaflets sampled from the latest fully developed trifoliate leaf after 3, 4, 5 and 6 wk. Measurementsoneach plant after 6 wk furthermore included total contents of32P and31P, root length and length of hyphae inside the mesh bag. The presence ofF, Candidareduced the average hyphal32P transport from the RFSC by 12% and the average AM hyphal length in the RFSC was reduced by 30%. The root dry weights of mycorrhizal plants were also reduced by the presence of Collembola. The reduction in total hyphal32P transport was not revealed by the data from the time‐course study using leaflet samples, which demonstrates the uncertainty of analyses of AM fungal activity based solely on measurements of leaf materials.The results from this work suggest thatF. Candidagrazed on roots and/or hyphae of AM; however, shoot yields were unaffected by this grazing. In conclusion, Collembola seemed to have little effect on the functioning of AM fungi.
Imbalanced nuclear ratios, post‐germination mortality and phenotype—genotype relationships in allopatrically‐derived heterokaryons of Heterobasidion annosum
Authors: RAMSDALE MARK , RAYNER ALAN D. M. 
Published: April 2006

summaryTwelve heterokaryotic strains of Heterobasidion annosum (Fr.) Bref. containing nuclei and mitochondria derived from British and North European populations were prepared by pairing homokaryotic strains and isolating hyphal tips from either side of interaction interfaces. Conidia derived from the heterokaryons had high germinability and were predominantly uninucleate. The nuclear genotypes recovered from these conidia were predominantly nonresident in origin, reflecting the marked asymmetry m nuclear ratios (as high as 9:1) in favour of invasive nuclei that developed in the mycelium. In spite of this asymmetry, the heterokaryons had similar phenotypes to the resident homokaryons that they were derived from.Whereas the relative ability of sib‐related nuclei to become established in a homokaryon was about equal in sympatric protoplasm, it could be very different in allopatric protoplasm. Post‐germination mortality due to the cessation of development following transfer of germlings to fresh medium was on average similar for allopatric and sympatric conidia, but there was a marked trend for reduction in mortality as nuclear ratio asymmetry increased. Homokaryons derived via conidia from a common heterokaryon exhibited less somatic incompatibility when paired together than did the original, basidiospore‐derived strains.These findings indicate that phenotype–genotype relationships resulting from allopatric matings, such as could occur following geographical transposition, are liable to differ radically from those in sympatric matings and so have potentially profound effects on resident population structure.