bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of varied microbial substrate conditions on the growth and mycorrhizal colonization of little bluestem (Schizachyrium scoparium (Michx.) Nash]
Authors: MEREDITH J. A. , ANDERSON R. C. 
Published: April 2006

summaryTo determine the response of little bluestem [Schizachyrlum scoparium (Michx.) Nash] to vesicular‐arbuscular mycorrhizal (VAM) fungi, various microbial populations, and interactions between VAM fungi and other microbes, plants were grown in three substrates: autoclaved soil, autoclaved soil to which VAM fungal‐free sievings of non‐autoclaved soil were added, and non‐autoclaved soil. Mycorrhizal plants were established in autoclaved soil and in autoclaved soil receiving sievings by using little bluestem root pieces that were Clorox‐treated for 9 or 17 s as a source of VAM fungal inoculum. Exposure of root pieces to a 0‐5 % solution of sodium hypochlorite (Clorox) for 13–23 s, surface‐sterilizes the roots, but it does not destroy viable internal VAM fungi. Control plants were grown in substrates receiving autoclaved root pieces. Plants grown in the autoclaved substrates had greater total biomass than plants grown in non‐autoclaved soil. Inoculum type (autoclaved or surface sterilized root pieces) or addition of sievings had no effect on any growth parameter for plants grown in autoclaved soil. Mycorrhizal plants grown in the autoclaved substrate, not receiving sievings had higher tissue concentrations of P, Ca, S, Zn, Mn, and Fe than non‐mycorrhizal plants grown in the same substrate. However, mycorrhizal plants did not produce more biomass than non‐mycorrhizal plants in autoclaved substrates. Differences observed between plants grown in the autoclaved and non‐autoclaved substrates are most likely attributable to greater nutrient availability of autoclaved substrates. The type of inoculum used and substrate conditions had negligible effects on rhizoplane and soil microbial populations. These included rhizoplane fungi and bacteria and selected functional groups of rhizoplane microbes (cellulose, chitin, and protein decomposers).
Architectural analysis of plant root systems
Authors: FITTER A. H. , STICKLAND T. R. 
Published: April 2006

summaryThe techniques of architectural analysis were applied to the root systems of plants growing under field conditions, to determine their validity in this situation and to measure the extent and causes of plasticity and of interspecific differences in root architecture in co‐existing species. In a three‐year study of two species (Trifolium repensL. andPlantago lanceolataL.) on eleven different soils, large differences were found between species, soils and years; much of the variation in the root architecture ofT. repenscould be explained in terms of soil moisture concentration. On two woodland sites, the root architecture of five species was followed over a 15–month period, and at one a manipulative experiment involving irrigation and nitrogen and phosphorus addition was set up. There were large differences between species in root architecture and seasonal changes in some aspects (topology and exterior link length), which probably represent developmental patterns. Irrigation induced topological changes in one species (Galium aparineL.) which were consistent with the results of the three‐year study, but not apparently with an earlier model. In the case ofMercurialis perennisL., however, both irrigation and N and P addition brought about the predicted changes in root architecture, namely shorter interior links and lower topological index, though N had the opposite effect on exterior links. Interior link length differed widely between species, but showed little temporal variation, suggesting that it may be a valuable character for further studies. These results illustrate the validity and potential of architectural analysis for the study of root systems extracted from field soils.
Effect of boron on the growth and mineral economy of some halophytes and non‐halophytes
Authors: ROZEMA J. , DE BRUIN J. , BROEKMAN R. A. 
Published: April 2006

summaryGrowth of halophytes in nutrient solutions with increasing boron concentrations was less reduced than that of some non‐halophytes. Boron (B) concentrations occurring in sea water (0350 mol m−3B) depressed growth of glycophytic plant species strongly, while growth of halophytes did not significantly differ from that under control conditions (Hoagland's nutrient solution containing 0025 mol m−3B).With increasing boron concentrations in the medium, the total boron concentrations in the shoot tissue increased up to 35 umol B B g−1d. wt (350 mg kg−1B d. wt basis) in the non‐halophytic species and were lower in most of the halophytic species examined. Sodium chloride (200 mol m−3) in the culture medium depressed the total B content of the shoot in the halophytic species. In most halophytic species, the water‐insoluble B fraction in the shoot and root tissue was higher than in the non‐halophytic species tested with the exception of Phaseolus vulgaris. When the plants were grown in culture solution containing 200 mol m−3NaCl, the ratio of insoluble: total B in shoot and root tissue increased. The resistance of halophytes to excess B and the possible detoxification of excess borate by complexation, either with cis‐diol groups of carboxyl groups in the cell walls or with dissolved compounds such as sorbitol in the halophytic Plantago maritima is discussed. The mechanism by which B tolerance in the halophytes might be accomplished is also discussed.
Role of calcium in aluminium toxicity
Authors: RENGEL ZDENKO 
Published: April 2006

summaryAluminium is the most important growth‐limiting factor in many acid soils throughout the world. Physiological effects of Al toxicity and mechanisms of tolerance are not well understood. An initial uptake of Al is confined to the apoplasm. Aluminium complexes (whose exact identification is beyond current experimental techniques) enter the cytosol slowly and only after prolonged exposure. Electrochemical properties of the cell wall Donnan free space as well as the plasma membrane of root cells are altered by the presence of Al ions that are polyvalent cations in acidic environments. The primary Al effects are very fast (taking only seconds to several minutes to develop) and may therefore occur while Al is still in the Donnan free space and on the apoplasmic side of the plasma membrane. Resumption of root growth upon removal of Al ions supports such a claim. Aluminium affects membrane permeability for both electrolytes and non‐electrolytes; it reduces accumulation of divalent cations (especially Ca and Mg) by interfering with the membrane transport. Aluminium alters the pattern of Ca2+ fluxes across the plasma membrane, thus supposedly disturbing symplasmic Ca2+ homeostasis. Supplemental Ca2+ can greatly alleviate deleterious Al effects. Frequently observed changes in the secretory activity of root cells exposed to Al are mediated through altered cell Ca2+ homeostasis; they result in cessation of cell wall growth and stoppage of root elongation. Involvement of calmodulin in the Al‐related phenomena is suggested to be indirect, at least in the initial stages of the Al treatment when Al is likely to be confined to the apoplasm. The role of growth substances, at least auxins and cytokinins, in the Al toxicity syndrome appears to be related to the Ca‐Al interactions that may alter the pattern of auxin transport as well as cytokinin biosynthesis and transport. Disturbance of the cell Ca2+ homeostasis appears to be an important feature of ion‐related environmental stresses in general (salt, heavy metals, aluminium).
Growth and maintenance respiration in leaves of Liriodendron tulipifera L. exposed to long‐term carbon dioxide enrichment in the field
Authors: WULLSCHLEGER S. D. , NORBY R. J. , GUNDERSON C. A. 
Published: April 2006

summarySpecific respiration rate (SRR) was mathematically partitioned into its growth and maintenance components for leaves of yellow‐poplar (Liriodendron tulipifera L.) after 3 yr of CO2 enrichment in open‐top field chambers. Despite the absence of a CO2 effect on individual leaf expansion or specific growth rate (SGR), increasing the CO2 concentration to ambient +150 or +300 cm3 m−3 decreased SRR by 28 to 45% compared with ambient‐grown controls. These lower leaf respiration rates were correlated with reduced leaf nitrogen concentrations. As described by the two‐component model of growth and maintenance respiration, SRR was a linear function of SGR. Ambient‐grown leaves had a growth respiration coefficient of 704 mg CO2 g−1 dry mass compared with 572 and 570 mg CO2 g−1 for leaves grown at the two higher CO2 concentrations. Leaves from the elevated CO2 treatments had an average maintenance respiration coefficient of 88 mg CO2 g−1 dry mass d−1 compared with 135 mg CO2 g−1 d −1 for leaves from the ambient treatment. Incorporating these growth and maintenance coefficients into a leaf growth simulation model indicated that total respiration would be reduced by 21 to 26 % for a leaf exposed to + 150 or + 300 cm3 m−3 CO2 throughout its 50‐d lifespan compared with one grown at ambient CO2 conditions. Reductions in total respiration were dominated by a lower rate of maintenance respiration, while the contribution of a lower specific rate of growth respiration was largely offset by a greater dry mass for leaves grown at elevated CO2 concentrations. Although reductions in the respiratory loss of carbon could be beneficial, respiration is unlikely to decrease without a concomitant decrease in other metabolic processes. Whether these reductions are beneficial or detrimental to the long‐term growth of plants exposed to elevated CO2 remains unresolved.
In vitro germination of wheat pollen on raffinose medium
Authors: CHENG CANHONG , MCOMB J. A. 
Published: April 2006

summaryWheat pollen gave up to 81.7 % germination when cultured on a 0.7 % agar medium containing 100 mg 1−1 H3BO3, 300 mg 1−1 CaCl2.2H2O and 0.75 M raffinose. On this medium at 25°C, germination started within 5 min and tubes reached a mean maximum length of 200 μm after 1 h. Maltose supported 27.9% germination, while sucrose gave at most 6.8%. Pollen on media with fructose, galactose, dextrose or lactose failed to germinate.
Seedling growth and root morphology of plants with different life‐histories
Authors: GROSS KATHERINE L. , MARUCA DEBORAH , PREGITZER KURT S. 
Published: April 2006

summaryDifferences among plant species in morphology and patterns of growth are assumed to influence their ability to acquire resources and, consequently, their competitive ability. Despite the acknowledged importance of below‐ground resources for plant growth, our knowledge of species differences in root morphology of non‐agricultural plants is limited. Comparisons of root morphology, growth rate and topology of seedlings of 12 herbaceous plant species that occur in early to mid‐successional fields revealed significant differences among species that were largely related to life history. Annuals grew faster and produced longer and more branched roots than did biennials and perennials. Only among the annuals was there a positive correlation between seed mass and root growth. The grasses allocated proportionately more biomass to roots than the dicots, but did not differ in root length or branching pattern. As seedlings, all 12 species exhibited a herringbone topology; although after 10 d there were significant differences in topology between annuals and perennials indicating that the annuals had begun to develop a more dichotomously branched root system. The possible effects of early differences in root morphology among life‐history types in acquiring soil resources in heterogeneous and successional environments are discussed.
Water stress effects on successional populations of the dioecious herb, Rumex acetosella L.
Authors: HOUSSARD C. , ESCARRÉ J. , VARTANIAN N. 
Published: April 2006

summaryThe effects of water stress and rewatering on the water relations and biomass of male and female plants of the dioecious herb, Rumex acetosella L., have been examined. Plants were collected from two fields, 2 and 15 yr old respectively, and submitted to different water regimes. Male plants from both populations showed a similar response to water deficit, having a low transpiration rate and low consumption of soil water, whilst maintaining a high green leaf area. Females from the two populations differed from each other more than males, both in terms of their response to drought and survival capacity. Females from the young population, which had a small green‐leaf area and a small root biomass, had progressively lower water potentials and maintained higher levels of transpiration at the onset of the first drought period, indicating a progressive acclimation to water stress. They also recovered more rapidly and to a greater extent than all the others upon rewatering. Females from the old population, with a high root/shoot ratio, transpired the most prior to the onset of water stress. They maintained a high water potential throughout the stress period, having high stomatal resistances and removing more water as soil moisture declined. This is indicative of drought avoidance. Root development was, however, limited in the shallow pots, hence the water resource was depleted rapidly and mortality occurred to a greater extent in these old‐field females. These characteristics may be adaptative, given the selection pressures which operate on water balance characters along a successional gradient and the spatial segregation of sexes that has been previously observed in this dioecious species in the same old‐field succession, with the sex ratio becoming progressively male‐biased with time.
Measuring investment in carnivory: seasonal and individual variation in trap number and biomass in Utricularia vulgaris L.
Authors: FRIDAY LAURIE E. 
Published: April 2006

SUMMARYThe partitioning of biomass between traps and leaves is a measure of the investment in carnivory of Utricularia vulgaris and is dependent on the relative values of three attributes: trap size, trap number and leaf size.Marked seasonal and individual variations in trap size, trap number and leaf size occur within a small population of U. vulgaris at Wicken Fen, Cambridgeshire, UK, with some plants consistently having fewer traps per leaf than others, and some smaller leaves than others, throughout the growing season. However, the three attributes vary independently, so that all combinations over the observed ranges of trap size, trap number and leaf size occur simultaneously in the population.In spite of the variation in the three constituent factors, the proportion of biomass invested in traps is close to 50% in the majority of plants and throughout most of the growing season. The contribution of traps to total biomass cannot be predicted from the number of traps per leaf.Although the proportion of biomass represented by traps is the most useful measure of a plant's investment in carnivory, the precise way in which the biomass is partitioned between a variable number of traps of different sizes may also be an important consideration in cost‐benefit analyses.
The clones of common lime (Tilia×vulgaris Hayne) planted in England during the seventeenth and eighteenth centuries
Authors: PIGOTT DONALD 
Published: April 2006

SUMMARYMost avenues of limes planted in England and Wales during the late seventeenth and early eighteenth century contain two distinct clonal types of common lime (Tilia×vulgaris Hayne). They differ in many morphological characters.Clonal group A has a fluted trunk with epicormic bosses or sprouts, a conical crown, scarlet, shining, ellipsoid overwintering buds, bright green leaves with obliquely asymmetric bases, long bracts narrowed to both ends and inflorescences normally of seven flowers. Clonal group B has a cylindrical trunk which is almost without epicormic buds or shoots, a hemispherical crown, crimson, pruinose, ovoid and sub‐acute buds, more or less cordate, dull green leaves, bracts narrowed to the stalk but broadly rounded at the distal end, and inflorescences with 3–5 flowers.Clonal group A includes the Dutch clones ‘Pallida’ and ‘Koningslinde’. Clonal group B is closely related to, but not identical with, the Dutch clone ‘Svartelinde’.Both clonal groups were probably originally imported from the Netherlands and were possibly derived from ancient village trees, which in the Netherlands are usually T. ×vulgaris.
Predicting plant responses to global environmental change
Authors: WOODWARD F. I. 
Published: April 2006

SUMMARYPredicting the future responses of plants and ecosystems to further changes in the CO2 concentration of the atmosphere and to the possibility of global warming are important current concerns. Predictions have been most frequently attempted using short‐term, single‐factor experiments in controlled environments. However, these experiments have failed to indicate the outcome of field experiments at larger spatial and temporal scales. Some of this failure is due to ignorance of environmental conditions and interactions while some is due to the use of inappropriate short‐cuts, such as the addition of fertilizers for simulating enhanced mineralization, and some is due to ignorance of the processes involved in scaling‐up from individual plants to populations. Long‐term observations on plants in ecosystems nevertheless indicate that community‐scale experiments may provide a useful but imperfect capacity to predict ecosystem responses. Although difficult to implement in practice, it is concluded that catchment‐scale experiments offer the best opportunity to predict plant, community and ecosystem responses to environmental change.

CONTENTS

Summary
239

I.
Introduction
239

II.
CO2‐enrichment experiments
240

III.
Experiments with applied nitrogen fertilizer
243

IV.
Population ecophysiology
245

V.
Ecosystem predictions
248

Acknowledgements
249

References
250
Sulphite‐induced changes of sulphur metabolism in the lichen alga Trebouxia sp
Authors: SCHLEE D. 
Published: April 2006

SUMMARYSolutions of sodium sulphite have been used to simulate the effect of gaseous sulphur dioxide on the lichen alga Trebouxia sp. The uptake and the metabolism of inorganic and organic [35S]compounds such as sulphate, sulphite, and cysteine were investigated in cells of Trebouxia under conditions of sulphite preincubation (sulphite‐stressed cells: 3 d pretreatment with 50 mmol m‐3 and 5 mol m‐3 solutions of sodium sulphite). Metabolism was similar, regardless of whether the Trebouxia was provided with [35S]sulphate or ‐sulphite. In sulphite‐stressed cells, uptake and incorporation into ethanol‐soluble compounds, especially cysteine and methionine, was significantly decreased. In Trebouxia exogenous [35S]cysteine is metabolized only at a very low rate.
Effects of an experimentally applied increase in ammonium on growth and amino‐acid metabolism of Sphagnum cuspidatum Ehrh. ex. Hoffm. from differently polluted areas
Authors: BAXTER R. , EMES M. J. , LEE J. A. 
Published: April 2006

SUMMARY Sphagnum cuspidatum Ehrh. ex. Hoffm. was removed from a relatively remote moorland site at the Migneint, N. Wales and from Holme Moss, S. Pennines — a site that has been subjected to atmospheric pollution deposition for a period of at least the last 200 yr.When exposed to elevated ammonium (NH4+) concentrations (0·1 and 1·0 mM) under laboratory conditions for a period of 30 d, S. cuspidatum from N. Wales showed a marked reduction in growth, whereas in the S. Pennine population, growth was stimulated above that of the untreated control tissue at both 0·1 and 1·0 mM NH4+. The largest growth stimulation, however, was seen at 0·1 mM.The effects of increased NH4+ in the growth medium on tissue total chlorophyll concentration after 30 d exposure were similar in moss from both study sites. There was a small linear decline in chlorophyll concentration with increasing ammonium concentration.Moss from both sites was exposed to 0·1 mM NH4+ for a period of 20 d. There was a marked difference in the response of the different moss populations as indicated by changes in the concentrations of the individual amino acids; notably a dramatic transient increase in glutamine (three‐fold), arginine (19‐fold), and asparagine (fourfold) in the moss from N. Wales. In contrast, in the S. Pennine moss, changes in tissue amino‐N concentration were very much smaller. Possible mechanisms to account for the intraspecific differences in response of the moss from the two study sites to increased ammonium concentrations are discussed.
The role of carbohydrate storage and redistribution in the source‐sink relations of wheat and barley during grain filling — a review
Authors: SCHNYDER HANS 
Published: April 2006

SUMMARYTwo types of source contribute photosynthate for grain filling in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), current photosynthate transferred directly to the grain and photosynthate redistributed from reserve pools in vegetative tissues. Reserve pools provide the substrate needed to maintain transport and the supply of assimilate to grains during the dark period of the diurnal cycle and during the latter part of grain filling, when the photosynthetic apparatus is senescing and the rate of dry matter accumulation of grains exceeds the rate of dry matter accumulation of the total crop. In addition reserve pools provide a means by which the current rates of photosynthate production and of photosynthate use in grain filling are allowed to proceed (at least in part) independently from each other. There is evidence that all photosynthetic organs (leaves, glumes and exposed portion of the peduncle) contain one or more diurnal carbohydrate storage pools. Diurnal storage of sucrose seems to be much more important than the transient storage of starch. There is little evidence for fructan pools serving a role as a net source of carbon during the dark period of the diurnal cycle. However, fructan is the most important longer‐term reserve carbohydrate of vegetative tissues. Fructan accumulation occurs mainly in the extended internodes and leaf sheaths and usually terminates within three weeks following anthesis, after which fructan is gradually lost until grain maturity. The accumulation and loss of fructan are greatly influenced by environmental conditions and treatments that alter the longer‐term balance between photosynthate production by the plant and photosynthate use in grain filling. Observations are consistent with the view that fructan accumulation in expanded vegetative tissue is not competitive with grain filling, but the fructan pools accept surplus photosynthate during periods of low demand by grains and provide photosynthate during longer‐term deficits in current photosynthate production. Even under optimal conditions for photosynthesis it is likely that half or more of the photosynthate in mature grains is temporarily deposited in one or more reserve pools before being transferred to the grain. Neither the efficiency of reserve utilization in grain filling nor its potential variability in different genotypes and environments are known. Also, very little is known about the mechanisms that control the partitioning of photosynthate between the grain and reserve pools and the allocation to different types of reserve pools. Future progress in the understanding of photosynthesis‐yield relationships will likely depend to a great extent on improved knowledge of the controls that govern photosynthate deposition and redistribution in the different pools of reserve carbohydrate.