bluuebunny/crossref_metadata_2025_split huggingface dataset:
Element localization in mycorrhizal roots of Pteridium aquilinum (L.) Kuhn collected from experimental plots treated with cadmium dust
Authors: TURNAU K. , KOTTKE I. , OBERWINKLER F. 
Published: April 2006

SUMMARY Pteridium aquilinum (L.) Kuhn roots collected from plots localized in a Pino‐Quercetum forest, treated 10 yr before with 2000 Mg km−2 of cadmium dust, were examined. The ultrastructure of endomycorrhizal roots and element distribution, determined using the electron energy loss spectroscopy, is given. The cytoplasm of the mycorrhizal fungus was found to contain more Cd, Ti and Ba than that of the host cells of the fern. Within polyphosphate granules present in fungal vacuoles beside Fe, S, N and Al which were reported by other authors, Cd, Ti and B were localized. Within fern cells Cd, Al, Fe, Zn and Cu were found to be accumulated both in plastids, especially in electron‐opaque, globular or crystalloid material, and on the surface of transfer cell wall ingrowth.
Genotype/nutrition interactions in the ectomycorrhizal fungus Hebeloma cylindrosporum Romagnesi
Authors: GAY G. , MARMEISSE R. , FOUILLET P. , BOULETREAU M. , DEBAUD J.C. 
Published: April 2006

SUMMARYIntraspecific variability in mycelial growth of the ectomycorrhizal basidiomycete Hebeloma cylindrosporum Romagnesi has been studied within 20 sib‐monokaryons, each being the progeny of one wild dikaryon fruiting in vitro, and the 50 synthesized dikaryons obtained from all the compatible fusions of these monokaryons. The interaction between fungal diversity and nutrition was also studied.The range of variation in mycelial growth (expressed as mg protein per culture) among the sib‐monokaryons was the same as that recorded among the synthesized dikaryons. The average growth of both mono‐ and dikaryons was highest on a synthetic medium containing nitrate as the sole nitrogen source, but showed the greatest variation. Fungal growth was approximately halved when nitrate was replaced by ammonium, and was intermediate on an organic nutrient‐rich medium. A decrease from 24 mM to 24 /M concentration of phosphorus reduced the average growth of the mycelia 40‐fold.The variation in mycelial growth in the synthesized dikaryons involved additive and non‐additive genetic components. Their ratio was variable depending on the nutrient conditions. In all cases but one, the interactive component was higher than the additive one.From an ecological point of view, these results emphasize the tremendous effect of nutrition on the phenotypic expression of fungal growth. Their possible significance for the dynamics of natural populations of ectomycorrhizal fungi is discussed.
Antioxidant response and winter hardiness in red spruce (Picea rubens Sarg.)
Authors: DOULIS A. G. , HAUSLADEN A. , MONDY B. , ALSCHER R. G. , CHEVONE B. I. , HESS J. L. , WEISER R. L. 
Published: April 2006

SUMMARYAntioxidant metabolism has been examined in red spruce growing at two sites with similar levels of ozone pollution but different winter temperatures. The northern site was Whiteface Mountain, New York with a latitude of 44° 31′(NY). The southern site was Whitetop Mountain, Virginia with a latitude of 36° 54′(VA). The northern site has lower winter temperatures. At the NY site two populations of trees were denned with respect to cold tolerance. An effort was made to establish a temporal relationship between the antioxidant capacity of conifer needles on one hand and the different stages of winter hardening/dehardening, and the induction of dormancy, on the other. The hypothesis tested was that winter injury of red spruce was due to an increased demand for glutathione at levels exceeding the inherent capacity of the needles and/or the altered activities of glutathione reductase.In the autumn, as temperatures began to decrease, photosynthetic potential decreased as spruce entered dormancy. At the same time, cold tolerance (measured as needle electrolyte leakage) gradually increased. Glutathione metabolism appeared to be coupled to these processes. At both sites, seasonal changes in glutathione levels were observed. These changes were found to coincide temporally with the onset and cessation of dormancy (as measured by decline in photosynthetic activity). The same pattern was observed at the northern and the southern site with the winter increases being greater at the former. Glutathione began to increase as soon as needles entered dormancy and began hardening. Glutathione reductase activities closely followed the dehardening process during spring, while glutathione concentration continued to stay relatively high with prehardening levels reached only by summer. At the northern site during the winter, cold‐tolerant trees had significantly higher glutathione reductase activities compared with cold‐sensitive ones. Based on these data, it is proposed that individuals that cannot respond to the increased demand for glutathione reductase activity during the hardening, winter and dehardening periods, become susceptible to winter injury.
Fructan content of wheat seedlings(Triticum aestivumL.) under hypoxia and following re‐aeration
Authors: ALBRECHT G. , KAMMERER S. , PRAZNIK W. , WIEDENROTH E. M. 
Published: April 2006

SUMMARYWe studied fructan accumulation in wheat seedlings (Triticum aestivumL. cv. Alcedo) caused by oxygen shortage around the root. Plants were cultivated in either nitrogen‐flushed or aerated nutrient solution. In response to the nitrogen treatment there was an accumulation of soluble carbohydrates in shoots as well as in roots. The main contribution was due to fructans. The content of fructo‐oligosaccharides had been increased five‐fold in the roots and seven‐fold in the shoots. This is incompatible with the assumption that higher substrate consumption follows enhanced fermentation under oxygen shortage. Re‐aeration of the nitrogen‐flushed nutrient solution resulted in enhanced consumption of stored carbohydrates, mainly of fructans, accompanied by high growth rates of the roots. The possibility of utilizing fructans quickly if oxygen is available is a possible advantage for plants adapted to hypoxia. Particularly however, it is suggested that the low energy requirements for sucrose: sucrose fructosyl transferase, allowing fructan synthesis even under oxygen shortage, may improve the fitness of plants to survive temporary hypoxia in the rhizosphere.
Fructosyltransferase activities from Lolium rigidum Gaudin
Authors: JOHN J. A. ST. , BONNETT G. D. , SIMPSON R. J. 
Published: April 2006

SUMMARYA partial separation of sucrose: sucrose fructosyltransferase (SST) activity from invertase activity extracted from leaves of Lolium rigidum Gaudin was achieved by gel filtration. The SST activity was purified 54‐fold with a ratio of SST activity to invertase activity of 1.1:1. The partially purified SST activity eluted with an apparent molecular mass of about 68000, had an optimum pH of 55 and a Km of 0.2 M. When incubated with sucrose concentrations ranging from 10 to 600 mM the partially purified SST activity produced mainly 1‐kestose and some 6‐kestose (10–15% of trisaccharide produced). SST and invertase activities declined during storage at — 25 °C with invertase activity declining at a faster rate. After the loss of invertase activity in storage, the partially purified SST activity synthesized only 1‐kestose. When incubated with 1‐kestose the partially purified SST activity synthesized neokestose (1.9 nkat ml−1), nystose (2.2 nkat ml−1) and an unidentified tetrasaccharide (1.4 nkat ml−1) indicating that the fructosyltransferase preparation also had FFT‐like activity. The partially purified invertase had significant sucrose‐hydrolyzing activity (25 nkat ml−1) and contained no measurable SST activity when incubated with 10–400 mM sucrose, but produced trisaccharide (1‐kestose and 6‐kestose, ratio 15:1) when incubated with 600 mM sucrose. L. rigidum does not normally accumulate 6‐kestose. The optimum pH of the sucrose‐hydrolyzing activity was 4–5 and the optimum pH of the fructosyltransferase activity of the invertase preparation was 55. The partially purified invertase did not have significant FFT‐like activity. The results support the hypothesis that SST activity synthesizes only 1‐kestose, which is a key intermediate in the synthesis of fructan in L. rigidum.
How to quantify differences in epicuticular wax morphology of Picea abies (L.) Karst. needles
Authors: TUOMISTO H. , NEUVONEN S. 
Published: April 2006

SUMMARYBecause researchers seldom possess unlimited resources, planning is needed to maximize the ratio of information gained to work needed. The aim of the present study was to find reasonable sampling and observation schemes for documenting regional differences in the impact of air pollution on the morphology of epicuticular needle wax. One‐year‐old Picea abies (L.) Karst. needles were collected in Southern Finland at two sites with different air pollution levels. In both sites, samples were taken from four trees, and within each tree, from three heights and four compass directions. The epicuticular wax of the needles was investigated under a scanning electron microscope (SEM) by estimating the relative abundances of eight wax types representing both tubular and degraded forms. Two ways are proposed to convert these data to index values, and the usefulness of this approach is evaluated. The differences between the two sites were significant, the needles from the urban site showing, on average, less‐preserved wax types than those from the rural site. Variation among individual trees within each site was pronounced, which proved the necessity of sampling several trees. There was also marked variation among the needles taken from the same tree, but this showed no consistent pattern with respect to sampling height or compass direction. Analysis of the variance at different hierarchical levels (among trees, among needles and within needles) suggested that the sampling effort is better invested when it is spread among several tree individuals than when it is concentrated on the detailed study of fewer trees.
Wall extensibility: its nature, measurement and relationship to plant cell growth
Authors: COSGROVE DANIEL J. 
Published: April 2006

SUMMARYExpansive growth of plant cells is controlled principally by processes that loosen the wall and enable it to expand irreversibly. The central role of wall relaxation for cell expansion is reviewed. The most common methods for assessing the extension properties of plant cell walls (‘wall extensibility’) are described, categorized and assessed critically. What emerges are three fundamentally different approaches which test growing cells for their ability (a) to enlarge at different values of turgor, (b) to induce wall relaxation, and (c) to deform elastically or plastically in response to an applied tensile force. Analogous methods with isolated walls are similarly reviewed. The results of these different assays are related to the nature of plant cell growth and pertinent biophysical theory. I argue that the ‘extensibilities’ measured by these assays are fundamentally different from one another and that some are more pertinent to growth than others.
‘That's a great deal to make one word mean,’ Alice said in a thoughtful tone.‘When I make a word do a lot of work like that’ said Humpty Dumpty,‘I always pay it extra’.‘Oh!’ said Alice. She was too much puzzled to make any other remark.Lewis Carroll, Through the Looking‐glass

CONTENTS

Summary
1

I.
Introduction
1

II.
The nature of wall expansive growth
2

III.
Techniques for measuring wall extensibility
4

IV.
Concluding remarks and prospectus
20

Acknowledgements
20

References
20
Mycorrhiza‐like interaction between the achlorophyllous gametophyte of Lycopodium clavatum L. and its fungal endophyte studied by light and electron microscopy
Authors: SCHMID E. , OBERWINKLER F. 
Published: April 2006

SUMMARYThe mycorrhiza‐like association of mature gametophytes of Lycopodium clavatum and an endophytic fungus was studied by means of light and electron microscopy. Fine aseptate hyphae of the fungus formed very regular dense hyphal coils and numerous small vesicles of different stages in the cortical cells. Extended infections occurred within preformed spaces between the cells of the storage tissue. These spaces probably arose by degeneration of the host cells. Several hyphae grew within them and were partly swollen or irregularly lobed and branched. They were embedded in a heterogeneous material, probably of host origin. Arbuscles were not established during the interaction. All fungal structures degenerated in the older host tissues that remained intact. The fungus contained bacterium‐like organelles. Elliptic interphase spindle‐pole bodies of the fungus were attached to the outer nuclear envelope. The host‐fungus interaction in the gametophyte of L. clavatum cannot be related to any type of mycorrhizal association described to date. It is therefore called the ‘Lycopodioid mycothallus interaction’.
Accumulation of photoassimilate by Peronospora viciae (Berk.) Casp. and leaves of Pisum sativum L.: evidence for nutrient uptake via intercellular hyphae
Authors: CLARK J. S. C. , SPENCER‐PHILLIPS P. T. N. 
Published: April 2006

SUMMARYAutoradiography showed that accumulation of label by hyphae of Peronospora viciae (Berk.) Casp., in leaflets of Pisum sativum L. exposed to 14CO2, was up to 4.5 times greater in the susceptible cv. Krupp Pelushka than the resistant cv. Early Onward. Concentrations of label were similar in apoplastic solutions from both cvs, although a greater volume was available in Early Onward. Uninfected Krupp Pelushka assimilated more label from 14CO2 than Early Onward; para‐chloro‐mercuribenzene sulphonic acid (PCMBS) treatment and infection reduced assimilation by Krupp Pelushka but not Early Onward. Infected leaf tissue from Early Onward assimilated more label than Krupp Pelushka from [14C]sucrose supplied to the apoplast. Transient treatment with PCMBS reduced assimilation of [14C]sucrose into infected plant tissue to 30 and 61 % of untreated levels, in Early Onward and Krupp Pelushka respectively. In contrast, autoradiography of hyphal fragments showed that the fungus accumulated 1.4 times more label from [14C]sucrose than without PCMBS. The different nutrient status of leaves of Early Onward and Krupp Pelushka, and evidence that label from sucrose is accumulated by intercellular hyphae directly from the apoplast, are discussed in relation to the role of haustoria and mechanisms of compatibility.
Wound‐healing in Vaucheria longicaulis Hoppaugh var. macounii Blum.
Authors: TORNBOM LAURIE , OLIVEIRA LUIS 
Published: April 2006

SUMMARYThe sequence of events leading to wound‐healing and resumption of growth are studied by light microscopy including the use of differential interference contrast optics in Vaucheria longicaulis Hoppaugh var. macounii Blum. Wound‐healing has been divided into four stages. In stage 1, a wound‐healing vesicle is rapidly extruded from the wound site. Loss of turgor pressure, as observed by the appearance of plasmolysis, is seen along the length of the filament. In stage 2, the wound‐healing vesicle is sealed‐off from the filament. Organelles then accumulate at the barrier created by the sealing‐off process. This is followed by chloroplast retraction from and return to the wound site, concurrent with the restoration of turgor pressure in late stage 2. In stage 3 chloroplasts again retract from and return to the wound site, in preparation for stage 4 that finally leads to the resumption of growth on the part of the healed filament.The effect of wound healing on organelle distribution has been studied with the use of selective fiuorochromes. The distribution of nuclei, identified by DAPI staining, remains largely unchanged after wounding. Mitochondria and probable lipid bodies (designated RBIs) are identified by staining with DiOC6 and Rhodamine B, respectively. Their presence in the wound‐healing vesicle cytoplasm and accumulation along the wound site points to the existence of an efficient mechanism of ATP synthesis in support of the energy requirements associated with the healing process. CTC fluorescence along the wound site and wound vesicle cytoplasm suggests that Ca2+‐based exocytosis is important in both wound‐healing vesicle expansion and its sealing‐off from the filament.
Combination effect of NaCl salinity, nitrogen form and calcium concentration on the growth, ionic content and gaseous exchange properties of Triticum aestivum L. cv. Gamtoos
Authors: HAWKINS H.‐J. , LEWIS O. A. M. 
Published: April 2006

SUMMARYThe effects of NaCl salinity have been investigated with respect to the growth response, ionic content and gas exchange characteristics of wheat plants (Triticum aestivum L. cv. Gamtoos) raised on nitrate or ammonium nutrition at different Ca2+ concentrations in the nutrient medium. Salinity up to 100 mM reduced the biomass production, moisture content and water use efficiency of both NO3− and NH4+‐supplied wheat but the biomass production of NO3+‐supplied wheat was reduced to a far greater degree than that of NH4+‐supplied wheat. There was no clear trend in the photosynthetic response of these plants to moderate salinity stress (50 mM NaCl). The stomatal conductances and transpiration rates of NH4+‐supplied wheat were between 20 and 40 % lower than those of NO3−‐supplied wheat, depending on the degree of salinity stress; at higher salinity (70–100 mM NaCl) the moisture content of NH4+‐supplied plants was c. 10% higher than that of NO3+‐supplied salinized plants. An increase in Ca2+ concentration from 0.5 to 5.0 mM resulted in an increase in biomass production, moisture content, shoot:root ratio, K+ content and a decrease in Na+ content of 50 mM NaCl‐stressed, NO3+‐supplied plants. Supplemental Ca2+ had no effect on the biomass production, shoot: root ratio or moisture content of 50 mM NaCl‐stress, NH4+‐supplied plants relative to the controls.
Effect of NaCl salinity, nitrogen form, calcium and potassium concentration on nitrogen uptake and kinetics in Triticum aestivum L. cv. Gamtoos
Authors: HAWKINS H.‐J. , LEWIS O. A. M. 
Published: April 2006

SUMMARYIn wheat plants it was found that salinity stress (50 mM NaCl) and an increase in the exogenous Ca2+ supply (to 5 mM) had a differential influence on N uptake capacity depending on the N source (NO3− or NH4+). In NO3−supplied wheat plants which had not been supplied with supplemental calcium, a salinity of 50 mM NaCl reduced the N uptake rate of the root by 30 %, reduced the Fmax of NO3− uptake by 38 % and the N concentration of the plants by 35 %. In NH4+supplied plants (which were not affected by a change in calcium concentration) a salinity of 50 mM resulted in a reduction in the N concentration by 16 % (only in the root), a reduction in the Fmax of NH4+uptake by 50 %, while the N uptake rate by the plant was reduced by 16 %. In salt‐stressed NO3−supplied wheat, an exogenous Ca24 concentration of 5 mM resulted in a 65 % increase in Vmax of NO3− uptake, a 58% increase in NO3− uptake rate by the shoot per g root and a 61 and 5 % increase in shoot and root N concentration respectively. Increased exogenous concentrations of either Ca2+ or K+ had no effect on NH4+ uptake. Kinetic calculations indicate that the inhibitory activity of NaCl on both NO3− and NH4+ uptake was one of noncompetitive inhibition. When NO3−, but not NH4+, was the N source, Ca2+ at a concentration of 5 mM partially ameliorated the NaCl‐mediated inhibition of NO3− uptake.
Orientation of the lateral roots of trees
Authors: COUTTS M. P. , NICOLL B. C. 
Published: April 2006

SUMMARYSitka spruce [Picea sitchensis (Bong.) Carr.] plants were grown under controlled conditions in specially designed boxes in which the plagiogravitropic lateral roots grew out from moist peat into an air space at one side. In one treatment the air was saturated with water vapour. In the other a linear horizontal gradient of water vapour pressure was maintained between the vertical peat surface and a porous membrane made from black cloth. Near the peat surface the vapour pressure gradient was equivalent to a soil water‐potential gradient of about 0.48 MPa mm−1.The angles of the roots before and after emergence from the peat were measured in different planes. In the saturated air treatment there was no significant change of angle after emergence but roots which emerged into the air with the humidity gradient grew more slowly and showed a marked change of direction. This deflection had two components; there was some tendency for the roots to be attracted to the moist peat surface (hydrotropism), and there was also a downward component (gravitropism). Mean deviation from the angle of emergence which would have resulted from a hydrotropic response alone was 58°, while deviation from the true gravitropic position was only 31°. Therefore under the conditions of the experiment the gravitropic response was considerably stronger than the hydrotropic one.The implications of these results are discussed for the growth of roots in soils, where water potential gradients generally do not seem to be sufficient to cause hydroptropic curvature. However, there was an enhanced gravitropic response of the tips of lateral roots subject to water stress and this may help control the orientation of roots near the soil surface.
Structure of fructan oligomers in cheatgrass (Bromus tectorum L.) *
Authors: CHATTERTON N. J. , HARRISON P. A. , THORNLEY W. R. , BENNETT J. H. 
Published: April 2006

SUMMARYLeaves of field‐grown cheatgrass (Bromus tectorum L.) plants were sampled during early spring when day‐ and night‐time temperatures were relatively cool. Fructan oligomers with a degree of polymerization (DP) 3–6 were extracted and purified using gel and anion‐exchange chromatography. The structures of 13 cheatgrass fructans were established. They included two trisaccharides [1‐kestotriose (1‐kestose) and 6‐kestotriose (6‐kestose)], four tetrasaccharides [(1.1)‐kestotetraose (nystose), (1&6)‐kestotetraose (bifurcose), (6,1)‐kestotetraose and (6,6)‐kestotetraose], three pentasaccharides [(1,1&6)‐kestopentaose, (1&6,6)‐kestopentaose and (6;1&6)‐kestopentaose] plus four hexasaccharides [(1,1,1&6)‐kestohexaose (1&6,6,6)‐kestohexaose, (6;1&6,6)‐kestohexaose and (6;1,6&6)‐kestohexaose]. All fructans larger then DP 4 contained a branch point. Each member of the dominant series(1&6)‐kestotetraose, (1&6,6)‐kestopentaose and (1&6,6,6)‐kestohexaose, is a branched fructan in which two fructose moieties are linked to the fructose subunit of each sucrose molecule. Thus the dominant series is built upon (1&6)‐kestotetraose. Fructans larger than DP 3 with exclusively 2→1‐ or 2→6‐linkages were absent except for a very small amount of (6,6)‐kestotetraose. The unique fructan structures synthesized in cheatgrass, wheat and oats illustrate diversity in the enzymology of fructan biosynthesis among grass species.