bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic analysis of Cd uptake in Cd‐tolerant and intolerant populations of the moss Rhytidiadelphus squarrosus (Hedw.) Warnst and the lichen Peltigera membranacea (Ach.) Nyl.
Authors: WELLS J. M. , BROWN D. H. , BECKETT R. P. 
Published: April 2006

SUMMARYCadmium uptake by photosynthetically Cd‐tolerant and intolerant populations of the moss Rhytidiadelphus squarrosus (Hedw.) Warnst and the lichen Peltigera membranacea (Ach.) Nyl. was investigated. Intolerant plants showed increased intra cellular Cd uptake compared to Cd‐tolerant material. Kinetic analysis indicated that reduced intracellular Cd uptake by Cd‐tolerant plant material was reflected in an increased Km or decreased Vmax for Cd. Pretreatment with KNO3 modified the extra cellular ion content of plant material, significantly reduced the apparent Km and could increase or decrease the Vmax for intracellular Cd uptake. Changes in kinetic constants caused by K pretreatment could be related to altered chemical equilibria when plant material was incubated in Cd solutions. Selective exclusion of Cd from intracellular locations was excluded as a tolerance mechanism in R. squarrosus and P. membranacea. Contrasting kinetic constants for intracellular Cd uptake in intolerant and Cd‐tolerant plant material were due to the prevailing extra cellular ion content when collected from the field. In R. squarrosus, K pretreatment resulted in increased uptake capacities and cell‐wall binding affinities for Cd in field‐grown moss apices. Laboratory‐grown apices, following K pretreatment, displayed increased uptake capacities but reduced affinities for Cd. Increased extra cellular Cd uptake in K‐pretreated moss apices was interpreted as additional weak electrostatic binding. Kinetic analysis indicated that electrostatic binding by extra cellular sites was less influential than the available supply of wall‐bounds ions on intracellular Cd uptake by moss apices.
Current trends in studies of long‐term plant community dynamics
Authors: RITCHIE J. C. 
Published: April 2006

SUMMARYLong‐term plant community dynamics has been investigated by analyses of macro‐ and microfossil remains found in unconsolidated limnic and terrestrial sediments, chiefly of Late‐Quaternary and Recent age. Plant macrofossils preserved in packrat (Neotoma) midden sites in semi‐arid regions have yielded the most informative data for the period between the lastest glacial to the present day. The remains can, with few exceptions, be identified to species level, they represent a large (>75%) proportion of the species composition of vegetation within a radius of 30‐50 m of a site, and they can be dated by the accelerator mass‐spectrometric radiocarbon method. Most sites have been found in the arid southwest of the United States and significant contributions have been made recently to understanding of long‐term changes in species composition and shifts in range and elevational limits of species. Similarly, analysis of macrofossils in lake, mire and river sites can draw on the taxonomic precision, small source area and potential for precise radiocarbon dating of samples, to provide detailed reconstructions of the local vegetation of lacustrine, mire and fluvial habitats. The vast literature reporting these investigations deals with sites chiefly in northern temperate regions, but recent studies from tropical and warm‐temperate regions show the promise of the approach. The use of analyses of microscopic charcoal preserved in sediments has increased significantly in the past few decades as part of attempts to reconstruct forest tire history and, when combined with other analyses (pollen, physical chemistry), to investigate past community dynamics. The major limitations of the method are poor chronological control in many sediments, uncertainties about source area and limited taxonomic precision. On the other hand, macroscopic remains of charcoal can usually be identified to species level, can be dated accurately and have readily defined source areas. However, sites with high frequencies of sample occurrence spanning long, continuous time intervals are very rare, as a remarkable example from the humid tropics of Africa illustrates. Pollen analysis of lake and mire sediments has a long history and has yielded a vast literature. Its weaknesses as a tool in the three main fields of interest where it is used ‐ palaeoclimatology, cultural history and plant community dynamics are well known and increase in regions farther north and south of the boreal and

Contents

Summary
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I.
Introduction
470

II.
Types of evidence
471

III.
Problems and prospects
487

Acknowledgements
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References
490
Stem and root nodules on the tropical wetland legume Aeschynomene fluminensis
Authors: LOUREIRO M. F. , JAMES E. K. , SPRENT J. I. , FRANCO A. A. 
Published: April 2006

SUMMARY Aeschynomene fluminensis Veil., originally obtained from flooded areas of the Pantanal Matogrossense region of Brazil, was grown under stem‐flooded or non‐flooded conditions for 70 d after inoculation with isolates of photosynthetic stem nodule rhizobia obtained from native A. fluminensis. Stem nodules formed only on submerged stems of flooded plants (mean of 25 per plant), and did not form on aerial parts, although they were capable of growing and fixing N2 after drainage of the stems. Root nodules formed on both non‐flooded and flooded plants but were usually decreased in number by flooding (from means of 124 to 51 per plant, respectively). Flooding (and stem‐nodulation) resulted in an increase in shoot (and a decrease in root) dry weight, regardless of rhizobial isolate.Stem nodules were attached by a wide collar of aerenchymatous tissue at the base of the nodule. There were large air spaces in the stem where nodules were subtended and these were continuous with nodule aerenchyma/outer cortex. In addition, aerenchyma and spongy tissue at the base of the nodule connected both flooded and non‐flooded root nodules to large intercellular spaces in the root cortex. The stem and root nodules were ovoid in shape, and essentially aeschynomenoid in type, i.e. the central infected tissue was without uninfected, interstitial cells. Root nodules had a similar structure to stem nodules (although stem nodules were generally larger), and flooded root nodules were approximately twice the size of non‐flooded nodules. The infected tissue of root and stem nodules consisted of spherical, bacteroid‐containing cells containing one or two rod‐shaped bacteroids per peribacteroid unit and prominent organelles. Infection threads were observed in root but not in stem nodules.The cortex of stem and root nodules had an apparent oxygen diffusion barrier, consisting of concentric layers of small cells with interlocking cell walls and few intercellular spaces. Cell layers external to these consisted of larger cells and intercellular spaces, with some spaces being occluded with an electron‐dense material that contained a glycoprotein recognized by the monoclonal antibodies MAC236 and MAC265. The amount of glycoprotein occlusions did not appear to differ between nodule types or treatments, although stem nodules contained intracellular glycoprotein vesicles adjacent to cell walls. The exterior of the nodules consisted of an epidermis of thin flattened cells with occasional lenticels. Amyloplasts were common in lower stem and hypocotyl nodules, but fewer in flooded or non‐flooded root nodules. Upper stem nodules (i.e. those within 6 cm of the water surface) differed from more profoundly submerged stem nodules by having chloroplasts throughout the cortex. Root nodules did not contain chloroplasts, and undifferentiated plastids were found mainly in lower stem nodules.
Ultrastructure of cortical root cells of Alnus incana infected by Penicillium nodositatum
Authors: SEQUERRA JEANINE , CAPELLANO ANDRE , GIANINAZZI‐PEARSON VIVIENNE , MOIROUD ANDRE 
Published: April 2006

SUMMARY Penicillium nodositatum Valla penetrates Alnus incana (L.) Moench roots through deformed root hairs. It then colonizes the cortical cells and induces the formation of myconodules which have structures similar to those of young actinorhizas. The ultrastructure of infected cortical cells has been compared with that of cells infected by pathogenic or symbiotic fungi as well as with that of cells infected by Frankia. Our observations show that an infected host cell shows few visible signs of resistance to the fungal invasion. As soon as P. nodositatum enters the cell, it is surrounded by a wall‐like pecto‐cellulosic matrix produced by the host cell. The host plasmalemma, invaginated around the endophyte, keeps its integrity as it does in symbiotic associations. At the beginning of the infection, the host cytoplasm and the fungus are intact but when the cell is completely invaded, the host cytoplasm becomes disorganized and subsequently the fungus also senesces, as in roots of Ericaceae infected by an endomycorrhizal fungus or as in older tissues of actinorhizas. P. nodositatum could survive the dead host cell by using its own reserves. Uninfected neighbouring host cells remain intact. P. nodositatum can be considered to behave as a neutral microsymbiont of A. incana, in a way similar to that of a compatible but ineffective Frankia strain.
Gas exchange rates and chlorophyll content of epi‐ and endolithic lichens from the Trieste Karst (NE Italy)
Authors: TRETIACH M. , PECCHIARI M. 
Published: April 2006

SUMMARYThe photosynthetic activity of calcicolous endo‐ and epilithic lichens from the Trieste Karst area (NE Italy) was investigated. The data consist of: (a) gas exchange rates of Acrocordia conoidea, Petractis clausa, Rinodina immersa (endolithic), and Aspicilia calcarea (epilithic), recorded at different combinations of temperature, water content and radiation flux values, (b) chlorophyll content values of nine species, and (c)δ13C values measured in 24 lichen species with different growth‐forms. The results show that: (1) the maximum photosynthetic rates of endolithic lichens are rather small, ranging between 0·2 and 1·5μmol CO2 m‐2 h‐1 at optimal conditions; (2) the relation between thallus water content and photosynthesis differs from that of foliose and fruticose lichens; the optimum water content of endolithic lichens is particularly small, when expressed in g H2O cm‐2; (3) the algae of endolithic lichens, which belong to different systematic groups, are light‐saturated at a small radiation flux; (4) chlorophyll contents of endolithic lichens are rather large, being similar to those of some parmelioid lichens. The ecological implications of the endolithic growth‐form are briefly discussed. Endolithic lichens should be regarded as slow‐growing, stress‐tolerant organisms, which are rather similar in their physiology to epilithic crustose lichens; they have a high resistance to CO2 diffusion, saturation being reached only at a very large CO2 concentration.
Differential response of leaf conductance, carbon isotope discrimination and water‐use efficiency to nitrogen deficiency in maritime pine and pedunculate oak plants
Authors: GUEHL JEAN‐MARC , FORT CHRISTINE , FERHI ANDRÉ 
Published: April 2006

SUMMARYGrowth, CO2 assimilation rate (A), leaf conductance (g), transpiration efficiency (W= ratio biomass production/plant water use) and carbon isotope discrimination (Δ) were assessed in maritime pine (Pinus pinaster Ait.) and pedunculate oak (Quercus robur L.) grown on a sand–peat mixture with three levels of fertilization: F100, optimal complete fertilization; F25, 25% of the optimal fertilizer supply; F0, no fertilization. Leaf phosphorus (P) and potassium (K) concentrations were affected little by the diminishing nutrient availability. Reduced fertilization decreased plant nitrogen (N) concentration in both species but leaf N concentration was less affected in oak than in pine. In pine W was markedly reduced in response to reduced leaf or whole plant N concentration, which was consistent with the sharp decrease also observed for plant intrinsic water‐use efficiency (ratio A/g) both at the instantaneous (gas exchange data) and time‐integrated (A/g derived from Δ measurements) levels. In this species, lowered W in the N deficient conditions was primarily associated with enhanced values of g. The existence of such a stomatal response pattern, confirmed by the increase in plant transpiration between F100 and F25, has not been reported before. In oak, both A and g were decreased in F25 and F0 as compared with F100. W was not affected – and instantaneous as well as time‐integrated A/g values were only slightly decreased – in relation to decreasing plant N concentration. For F100, no difference in W was noticed between pine and oak though the Δ values were 2·6‰ lower in oak. We speculate that this discrepancy was linked with higher plant‐carbon losses through processes like respiration, fine‐root mortality or root exudation in oak. The isotopic approach proved useful for assessing the effects of nutritional status on W, but has to be used with caution when comparing different species.
Interactions between drought and elevated CO2on osmotic adjustment and solute concentrations of tree seedlings
Authors: TSCHAPLINSKI T. J. , STEWART D. B. , NORBY R. J. 
Published: April 2006

SUMMARYAlthough drought tolerance of tree species is a critical determinant of forest composition, how elevated CO2affects drought tolerance is uncertain. Interactions between elevated CO2and drought on osmotic potential and osmotic adjustment of American sycamore (Platanus occidentalisL.), sweetgum (Liquidambar styracifluaL.), and sugar maple (Acer saccharumMarsh.) were investigated using 1‐yr‐old seedlings, planted in 81 pots and grown in four open‐top chambers, containing either ambient air or ambient air enriched with 300 μmol mol−1CO2. A well‐watered treatment with plants watered daily and a droughted treatment in which plants were subjected to a series of drought cycles were included within each chamber. Sugar maple and sweetgum seedlings completed a total of seven drying cycles, whereas sycamore seedlings, because of their greater leaf area and plant size, completed 11 cycles. The mean soil water potential at re‐watering for droughted seedlings in ambient CO2was –0·5, –0·7, and –1·8 MPa for sugar maple, sweetgum and sycamore, respectively, compared with –0·2, –0·7, and –1·2 MPa, respectively, under elevated CO2. By contrast, all well‐watered plants were maintained at soil water potential – 0·1 MPa.Drought under ambient CO2reduced osmotic potential at saturation for leaves of sycamore and sweetgum by 0·30 MPa and 0·61 MPa, respectively, but leaves of sugar maple did not display osmotic adjustment to drought. Elevated CO2increased osmotic potential at turgor loss for leaves of sugar maple by 0·33 MPa under well‐watered conditions, and 0·48 MPa under drought. This response was not evident in the other species and might be related to the rapid growth of sugar maple causing a depletion of solutes. Whereas drought reduced the total solute concentration in roots of sugar maple, primarily the result of a reduction in K, elevated CO2did not alter the concentration of total solutes in roots of any of the three species. Elevated CO2has differing effects on drought tolerance among tree species, and thus might alter the competitive relations between species.
Flood‐induced leaf elongation in Rumex species: effects of water depth and water movements
Authors: BANGA M. , BLOM C.W. P. M. , VOESENEK L. A. C. J. 
Published: April 2006

SUMMARYSeveral species from the genus Rumex are found in Dutch river forelands. Species such as R. palustris Sm. From the low, frequently flooded areas are well adapted to wet conditions, Rumex species from higher and less frequently flooded sites are poorly adapted and therefore sensitive to flooding. One of the adaptations to flooding is enhanced shoot elongation upon complete submergence, enabling plants to restore leaf‐air contact, provided that the water is not too deep. This paper demonstrates the strong variation in the absolute extent of flood‐induced leaf elongation among species of the genus Rumex. The effects of flooding on shoot dry and fresh weight and internal gas volumes of an elongating and a non‐elongating species, R. palustris and R. acetosella L., were compared. Net water uptake in response to complete submergence was observed in the shoots of both species. Based on results presented here, we conclude that in plants of R. palustris water enters the cells and is used for cell expansion leading to petiole elongation, whereas in plants of R. acetosella at least part of the water taken up fills the intercellular gas spaces. Elongation of completely submerged Rumex plants does not vary with different depths of submergence, This was concluded from the observation that there is little effect of either hydrostatic pressure or irradiance on leaf elongation during complete submergence. However, when R. palustris plants were subjected to a changing water depth, i.e. alternate periods of complete submergence and waterlogging, they elongated less strongly than under permanent complete submergence. Water movements did not affect leaf elongation induced by submergence.
Fructan exohydrolase activities from Lolium rigidum that hydrolyze β‐2, 1‐ and β‐2, 6‐glycosidic linkages at different rates
Authors: BONNETT G. D. , SIMPSON R. J. 
Published: April 2006

SUMMARYFive fructan exohydrolase activities from Lolium rigidum Gaudin were separated and partly purified by a combination of salt precipitation, affinity chromatography, gel‐filtration chromatography, anion‐exchange chromatography and isoelectric focusing. The activities were identified by incubating enzyme fractions with fructan from both Lolium rigidum and Cichorium intybus. On the basis of activities when (6,6,6)‐kestopentaose and (1,1,1)‐kestopentaose were used as substrates, it was concluded that three of the activities hydrolyzed β‐2, 6‐glycosidic linkages faster than β‐2,l‐glycosidic linkages and two activities hydrolyzed β‐2,l‐glycosidic linkages faster than β‐2, 6‐glycosidic linkages. Fructan exohydrolases that hydrolyze β‐2,l‐glycosidJc linkages faster than β‐2, 6‐glycosidic linkages, and fructan exohydrolases that hydrolyze β‐2, 6‐glycosidic linkages faster than β‐2,1‐ glycosidic linkages have not previously been identified together in a temperate grass. All fructan exohydrolases were inhibited markedly by sucrose. It is proposed that the classification of β‐fructofuranosidases be reconsidered because EC 3.2.1. 80 is presently used to designate all fructan exohydrolases irrespective of the rates at which they hydrolyze β‐2, 6 or β‐2, 6‐glycosidic linkages in fructans.
Reorganization of the endoplasmic reticulum in pea leaf epidermal cells infected by the powdery mildew fungus Erysiphe pisi
Authors: LECKIE CALUM P. , And JAMES A. CALLOW , GREEN JONATHAN R. 
Published: April 2006

SUMMARYDuring the formation of haustoria by biotrophic pathogens the synthesis of extra host plasma membrane (PM) is required to accommodate the invagination of the PM and its transition to the extrahaustorial membrane. This implicates alterations in host exocytosis, membrane trafficking and targeting. Probes for endoplasmic reticulum (ER) and whole‐cell imaging by confocal laser scanning microscopy (CLSM) have been used to examine the organization of the endoplasmic reticulum (ER) in compatible interactions between pea leaf cells and Erysiphe pisi DC ex Saint‐Amans. In uninfected epidermal cells, the dicarbocyanine dye DiOC6(3) and the ER‐specific anti‐HDEL antibody showed cortical ER was an open network of tubules interspersed with lamellar cisternae, immediately beneath the cuticle. Endoplasmic reticulum in infected cells could not be stained with DiOC6(3) but anti‐HDEL labelling revealed that the ER was no longer evenly distributed throughout the cortical cytoplasm but was concentrated in a tight network in the viciniti, of the haustorium particularly at early stages of infection. In some infected cells there was intense ER staining very close to the extrahaustorial membrane. Endoplasmic reticulum was also observed as large cisternae adjacent to the haustorial complex (HC), contrasting with tubular ER structures distal to the HC. In Western blots, anti‐HDEL labelled one major band at 70 icDa (probably the BiP homologue) in extracts from uninfected and infected epidermis, mycelia and haustoria. Additional proteins at 55 and 80 kDa were recognized in the fungal extracts. A minor protein at 50 kDa in uninfected pea is possibly upregulated in infected leaves. Overall, the results show that in a compatible pea powdery mildew interaction, the host cortical ER reorganizes around the developing HC from early to late stages of the infection process. This reorganization is likely to be involved in the exocytosis of new membrane and matrix materials which contribute to the expanding HC.
Root hair length determines beneficial effect of a Glomus species on shoot growth of some pasture species
Authors: SCHWEIGER P. F. , ROBSON A. D. , BARROW N. J. 
Published: April 2006

SUMMARYDifferences between plant species in the benefit derived from arbuscular mycorrhizal colonization have often been attributed to differences in physical properties of their roots, especially in root hair development. To test this hypothesis, the growth response to phosphate of five pasture species which differed markedly in the length of their root hairs was measured. Plants in the mycorrhizal treatments were inoculated with a Glomus sp. (isolate WUM 10(1)) while non‐mycorrhizal plants received control inoculum. Benefit was described as the relative effectiveness of phosphorus (P) for the mycorrhizal plants compared with non‐mycorrhizal plants. The beneficial effect of Glomus sp. was inversely related to root hair length of the host plant but it was not well related to root diameter, root length per plant or root/shoot ratio. It is suggested that root hairs and external hyphae of Glomus sp. act as alternative, similar ways of shortening the distance for the diffusion of phosphate in soils.
Chitinolytic activities of Eucalyptus pilularis and Pinus sylvestris root systems challenged with mycorrhizal and pathogenic fungi
Authors: HODGE A. , ALEXANDER I. J. , GOODAY G. W. 
Published: April 2006

SUMMARYThe chitinolytic activities of Pinus sylvestris L. and Eucalyptus pilularis Sm. roots were measured after an exposure for 24 h to either ectomycorrhizal (Pisolithus tinctorius (Pers.) Coker and Couch) or root‐infecting pathogenic fungi (Heterobasidion annosum (Fr.) Karst. and Phytophthora cinnamomi Rands.). P. sylvestris roots not exposed to fungal hyphae had low levels of β‐N‐acetylglucosaminidase. This activity greatly increased after exposure to H. annosum but not P. cinnamomi or P. tinctorius.β‐N‐Acetylglucosaminidase activity in E. pilularis roots was unchanged after exposure to P. cinnamomi or P. tinctorius. Exo‐ and endochitinase activity increased after P. sylvestris roots were challenged with H. annosum, but not by the other fungi. These results suggest that β‐N‐acetylglucosaminidase might be an important early response to chitinous pathogens.