bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of liming on the uptake of organic and inorganic nitrogen by mycorrhizal (Paxillus involutus) and non‐mycorrhizal Pinus sylvestris plants
Authors: ANDERSSON SOLBRITT , EK HANS , SÖDERSTRÖM BENGT 
Published: March 2003

SUMMARYSeedlings of Pinus sylvestris L. were grown in Plexiglas® observation chambers in limed (CaCO33, pH 5.0 and 5.9) and untreated (pH 4.1) peat. The seedlings were either colonized by the mycorrhizal fungus Paxillus involutus (Batsch: Fr.) Fr. Or were non‐mycorrhizal. After 18 wk in the observation chambers, 15N‐labelled organic nitrogen, as lyophilized and ground mycelium of Suillus variegatus (Swartz: Fr.) O. Kuntze, or ammonium, was added to the peat. The plants were harvested after an uptake period of 14 d.Irrespective of the nitrogen form added, liming decreased both the content and concentration of 15N in non‐mycorrhizal plants, and, to a lesser extent, those in mycorrhizal plants. In mycorrhizal plants the uptake of 15N was not correlated with area colonized by the mycorrhizal mycelium. The amount of KCl‐extractable 15N in peat without plants and mycorrhizal fungi decreased with liming. It is proposed that liming induced chemical or microbial immobilization of the added 15N. This is suggested to be the main reason for the decreased uptake of 15N in lime treatments.
Chlorophyll: a symptom and a regulator of plastid development
Authors: THOMAS HOWARD 
Published: March 2003

SUMMARYThe metabolism of chlorophylls and related tetrapyrroles directly influences, and is influenced by, the proteins and cell structures with which they are associated. During net accumulation, de‐greening and at the steady state chlorophyll and its derivatives are important elements in the post‐translational regulation of the expression of genes for chloroplast proteins. At the same time, they represent potential photodynamic hazards against which green cells need to have protective mechanisms. This review deals with genetic, chemical and environmental perturbations of chlorophyll biosynthesis that impact on protein stability, membrane organization and susceptibility to photodamage. NADPH‐protochlorophyllide oxidoreductase is considered in detail as a pigment– protein regulating, and regulated by, chlorophyll metabolism. The question of the extent and significance of chlorophyll turnover at the steady state is addressed, with particular emphasis on the dynamics of the photosystem II reaction centre. The pathway of chlorophyll catabolism is described, along with its interrelationship with protein mobilization in chloroplast senescence. Finally, the structural basis of pigment‐protein interaction and stability is examined, and the discussion ends by expressing some general thoughts about the control of protein lifetimes in the living cell.

CONTENTS

Summary
163

I.
Introduction
164

II.
Chlorophyll and related tetrapyrroles
164

III.
Chlorophyll‐protein complexes
164

IV.
Chlorophyll biosynthesis
166

V.
NADPH‐protochlorophyllide oxidoreductase
168

VI.
Assembling chlorophyll‐proteins
171

VII.
Chlorophyll turnover at the steady state
172

VIII.
The plastid family tree
173

IX.
The pathway of chlorophyll catabolism
173

X.
Chlorophyll and associated proteins in senescence
175

XI.
How does chlorophyll stabilize associated proteins ?
176

XII.
Conclusion
177

Acknowledgements
177

References
177
ATPase activities of root microsomes from mycorrhizal sunflower (Helianthus annuus) and onion (Allium cepd) plants
Authors: BAGO B. , DONAIRE J. P. , AZCÓN‐AGUILAR C. 
Published: March 2003

SUMMARYWe compared the plasma membrane, tonoplast and mitochondrial Mg‐ATPase activities of microsomes isolated from mycorrhizal and non‐mycorrhizal sunflower (Helianthus annuus L.) and onion (Allium cepa L.) roots during a time‐course experiment (21–60 d). No significant difference was observed between the protein levels of root microsomes from mycorrhizal and non‐mycorrhizal sunflower. However, the protein content of microsomes obtained from mycorrhizal onion roots increased when the symbiosis was well established (more than 50 % of root length colonized by the arbuscular mycorrhizal fungus). Kinetic studies revealed that vanadate‐sensitive (plasma membrane‐associated) ATPase activity of sunflower root microsomes increased with mycorrhizal colonization. However, the vanadate‐sensitive ATPase activity of microsomes from mycorrhizal onion roots decreased compared with those from non‐mycorrhizal controls. Increased activity of nitrate (tonoplast‐associated) and azide (mitochondrial membrane‐related)‐sensitive ATPase activities was detected in extracts obtained from 45– and 60–d‐old mycorrhizal onion plants. A slight increase in azide‐sensitive ATPase activity was detected in microsomes of mycorrhizal sunflower. The existence of different physiological and biochemical strategies in sunflower and onion in relation to the establishment of this mutualistic symbiosis is discussed.
Influence of leaf water content on the C3–CAM transition in Mesembryanthemum crystallinum
Authors: HERPPICH WERNER B. , HERPPICH MARGARETHA 
Published: March 2003

summaryChanges in leaf water content, night‐time accumulation of malic (δ‐malate) and citric acid (δ‐citrate) and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activity were followed for 60 d after germination in well watered and salt‐stressed plants of the facultatively halophytic ephemeral Mesembryanthemum crystallinum L. To separate the effects of development, salt stress and water deficit on crassulacean acid metabolism (CAM) induction plants were stressed initially 10 d after germination and then successively at 1‐wk intervals (five sets). Related to dry mass or organic matter (i.e. dry mass corrected for the mass of inorganic ions) water content started to decrease during the late embryonal phase of the life cycle. Water content on a dry mass basis was always lower in salt‐stressed than in well watered individuals. However, on an organic matter basis no difference was detectable. This indicated that salt treatment did not reduce leaf water content but falsified the basis (dry mass). Increases in leaf succulence and in pressure potential prevented long‐term water deficit in well watered and in salt‐stressed plants. Instead, these changes displayed enhanced vacuolisation, which is an essential prerequisite for the development of CAM. The end of that differentiation process might allow the initiation of nocturnal malic acid accumulation in a threshold response. At the onset of each salt treatment, short‐term water deficits occurred due to an incomplete osmotic adaptation independent of plant age. As δ‐malate only appeared when plants were c. 35 d old this water deficit was unlikely to be a decisive CAM‐inducing factor. About 2 wk after germination water content began to decline during the light periods in plants of all treatments. This pattern disappeared again when CAM had been fully established. Daytime transpirational water loss is therefore unlikely to be the decisive factor because it failed to induce the metabolic shift in young plants. Environmental stress (e.g. salt or drought) can therefore only induce δ‐malate when leaf and plant differentiation has reached a certain stage.
High densities of arbuscular mycorrhizal fungi maintained during long fallows in soils used to grow cotton except when soil is wetted periodically
Authors: PATTINSON G. S. , McGEE P. A. 
Published: March 2003

SUMMARYSequential harvests of cotton seedlings grown in soil cores enabled the quantification of the density of arbuscular mycorrhizal fungi to detect the effects of time, cultivation and periodic wetting of the soil. Cotton seedlings grown in soil cores from three locations formed arbuscular mycorrhizas at similar rates when cores were stored dry for up to 18 months. Disturbance of dry cores followed by dry storage for 18 months did not reduce the rate of establishment of mycorrhizas. Periodic wetting and drying of the cores, especially if the cores had first been disturbed, significantly reduced the rate of establishment of mycorrhizas. We suggest that long fallow disorder is possibly caused by falls of rain in clay soils of eastern Australia used to grow cotton. The proportion of the root with mycorrhizas at 3 wk was strongly correlated with the infection at 8 wk. We also suggest that it might be possible to predict maximum levels of infection and early uptake of phosphate of seedlings by determining the proportion of roots that are mycorrhizal 3 wk after emergence of cotton seedlings.
Artificial selection and heritability of ozone resistance in two populations of Plantago major
Authors: WHITFIELD C. P. , DAVISON A. W. , ASHENDEN T. W. 
Published: March 2003

summaryGeographically separated populations of Plantago major L. differ in ozone resistance, and this is correlated with the exposure to ozone at the location of each population. In addition, two populations of P. major have been demonstrated to show an increase in ozone resistance after summers when ozone concentrations were high. However, if evolution of ozone resistance has occurred in the field there must be appropriate heritable genetic variation and this must be demonstrated.In the present study, artificial selection for ozone resistance and sensitivity was imposed on a resistant (‘Lullington Heath’) and sensitive (‘Bush’) population of P. major. Artificial selection is an efficient means of demonstrating additive genetic variance for a character. Selection was based on 2 wk growth in ozone (70 nl O3 1−1for 7 h d−1), and selected lines were tested for ozone resistance under both short and long term ozone exposures. Changes in ozone resistance were demonstrated for each population. On the basis of a 2‐wk screening test, selection from the initially sensitive Bush population led to a line that was significantly more resistant to ozone, but it was not possible to select a line with greater sensitivity than the original population. Conversely, selection from the initially resistant Lullington Heath population led to a line with increased sensitivity but not to a line with increased resistance. Differences in ozone resistance between the selected lines were maintained over the long term and were reflected in growth and seed production at the final harvest. Net assimilation rate, stomatal conductance and leaf pigments were measured. In both populations the lines selected for sensitivity showed a greater effect of ozone on net assimilation rate. Ozone had a minor effect on chlorophyll content in the Lullington Heath sensitive line but tended to increase carotenoid concentrations. However, this effect on carotenoids was not related to ozone resistance.The experiment demonstrated that ozone resistance in P. major is heritable. The response to selection reported here supports previous evidence from field collections of a rapid evolution of ozone resistance.
The relationship between intracellular pH, growth characteristics and calcium in the cyanobacterium Anabaena sp. strain PCC7120 exposed to low pH
Authors: GIRALDEZ‐RUIZ N. , MATEO P. , BONILLA I. , FERNANDEZ‐PIÑAS F. 
Published: March 2003

summaryChanges in various cell functions were examined during a shift of the cyanobacterium Anabaena sp. strain PCC7120 to acidic external pH (pHex) in the presence and absence of added calcium. In the presence of 0–25 mM Ca (the standard Ca concentration of the growth medium), growth and O2 evolution were inhibited at pH values lower than 6. The cyanobacterium was unable to maintain a relatively constant internal pH (pHi) at pH 6 and below, which led to acidification of the cytoplasm. In the absence of Ca, the acidification found at acid pH values was even more pronounced. The elimination of Ca did not affect pHi at pHex of 6–5 and above. Increased acidification of the internal cell contents correlated well with a general impairment of growth in Ca‐deficient cells exposed to external acid pH values. On the other hand, Ca enrichment of cells grown under acidic conditions resulted in a significant improvement of several physiological processes. The protein pattern of cell extracts of Anabaena sp. strain PCC7120 was altered by acidity. The most significant modifications of the protein profiles induced at low pH were not evident in the presence of high concentrations of Ca. Increasing concentrations of Ca allowed Anabaena sp. strain PCC7120 to perform better at lower pH.
Mathematical modelling of morphogenesis in fungi: spatial organization of the gravitropic response in the mushroom stem of Coprinus cinereus
Authors: MEŠKAUSKAS A. , MOORE DAVID , FRAZER LILYANN NOVAK 
Published: March 2003

The purpose of this work was to establish how the distribution of local curvatures changed during the mushroom stem gravitropic reaction and to suggest a suitable mathematical model based on these new data.The gravitropic bending of base‐ and apex‐pinned Coprinus cinereus (Fries) S. F. Gray stems was recorded on videotapes. The images were captured from the tapes after each 10 min, rotated by 45° and transformed into tables of changing co‐ordinates of points for each stem. The non‐linear regression of these points was performed using Legendre polynomials. From the resulting equations the patterns of changing local curvature for 50 subsections per stem during 400 min of gravitropic reaction were calculated.It was observed that base‐pinned stems first bent from the apex, but later the curvature of this part decreased, and in the late stages the apex became nearly completely straight again. Subsections, located about one third of stem length from the base determined the main part of the final curvature. The free basal part of the apex‐pinned stems bent upward and after a certain bending time also began to straighten. However, this process started significantly later and was weaker. Bending of the subsections close to the pinned apex did not stop when they reached the vertical position, and the final angle of gravitropic curvature could exceed 180°.Plotting various functions of local bending speed and its derivatives against each other and against local angle indicated that, if the hypothetical signal about reorientation arises in the apex, its propagation towards the base did not follow simple wave or simple diffusion laws. The importance of the local angle of all subsections both for signal origin and transmission was established and a signal transmission equation, involving local angle of each subsection, was derived. After creating a suitable program this partial differential equation was solved numerically. The generated shapes of the bending stem coincided in high degree with experimentally observed images.
Solute transport into healthy and powdery mildew‐infected leaves of pea and uptake by powdery mildew mycelium
Authors: CLARK JOANNA I. M. , HALL J. L. 
Published: March 2003

The transport of sugars and amino acids into the mycelium of Erysiphe pisi DC. was investigated using two different systems, intact leaf discs and mycelial suspensions. Of the sugars tested, glucose was preferentially taken up by both uninfected and mildew‐infected leaf discs, whereas glutamine was taken up by both tissues at a higher rate than lysine or aspartic acid. Leaf discs from infected tissue had a greater uptake capacity than those from healthy tissue for both sugars and amino acids. The uptake of glucose was inhibited more markedly than that of sucrose and fructose by 10 μm carbonyl cyanide m‐chlorophenylhydrazone (CCCP), 1 mmN‐ethylmaleimide (NEM), 1 mm diethyl pyrocarbonate (DEPC) and 1 mm phenylglyoxal, whereas 1 mm PCMBS (p‐chloro‐mercuribenzenesulphonic acid) inhibited sucrose uptake to the greatest extent. Uptake of glutamine, lysine and aspartic acid was inhibited similarly by CCCP (80%), NEM (20%), DEPC (70%) and PCMBS (60%). Additionally, leaf discs were used to determine which solutes could be taken up from leaf tissue by the fungus. The uptake of sugars into the mycelium was greater than that of amino acids.Suspensions of powdery mildew mycelium accumulated glucose at about three times the rate of sucrose or fructose, and the amino acid glutamine was taken up at three times the rate of lysine or aspartic acid. Spores separated from the suspension had a low uptake capacity.When the reducing sugar concentration of leaf apoplastic fluid was estimated, leaves infected by powdery mildew had much higher amounts in the apoplast, whereas the activity of acid invertase also appeared to be higher in apoplastic fluids from infected leaves. When apoplastic fluid samples were run on SDS gels, an invertase antibody detected two bands in samples from infected tissues that were not found in the uninfected samples.
Development and good breeding in legume models: poise and peas?
Authors: Downie J. A. , Bonfante P. 
Published: March 2003

John Innes Centre, Norwich, UK, June 2000Genomics research involving legumes, an area that is attracting major funding, has two distinct branches – work involving model species, and work involving crops. This meeting aimed to stimulate communication between these two groups. The major research areas covered included leaf, flower and seed development, establishment of symbioses, pathogen interactions and applied aspects (from the conservation of legume ecotypes to products required by the market).
Limited effect of increased atmospheric CO2concentration on ombrotrophic bog vegetation
Authors: Hoosbeek Marcel R. , Van Breemen Nico , Berendse Frank , Grosvernier Philippe , Vasander Harri , Wallén Bo 
Published: March 2003

Summary Boreal and subarctic peatlands contain 20–30% of the world’s soil organic carbon, and if growing, they constitute sinks for atmospheric CO2. We hypothesized that even in the nutrient‐poor bog environment, elevated CO2would stimulateSphagnumgrowth more than vascular plant growth, thereby improvingSphagnum’scompetitive strength and enhancing carbon (C) sequestration. Free‐air carbon dioxide enrichment (FACE) experiments took place on predominantly ombrotrophic peatbog‐lawns in Finland (FI), Sweden (SW), The Netherlands (NL), and Switzerland (CH). After 3 yr of treatment, increased CO2concentration (560 ppm on volume basis) had no significant effect onSphagnumor vascular plant biomass at either site. This research suggests that, just as with other nutrient‐poor ecosystems, increased atmospheric CO2concentrations will have a limited effect on bog ecosystems.
Grassland species effects on soil CO2 flux track the effects of elevated CO2 and nitrogen
Authors: Craine Joseph M. , Wedin David A. , Reich Peter B. 
Published: March 2003

Summary

•  Understanding and predicting the impacts of elevated atmospheric CO2, elevated nitrogen deposition, and decreases in plant diversity require better understanding of the way in which plant species influence soil CO2 flux.
•  In experimental grassland plots where atmospheric CO2, nitrogen supply, and species composition and diversity were manipulated, species effects on soil CO2 flux during 19 sampling periods over 2 yr were determined for 16 grassland species.
•  The average effect of a species on soil CO2 flux was correlated with biomass of the species grown in monoculture, suggesting that effects of species on soil CO2 flux are related to the potential productivity of a species and total belowground C allocation. During dry, warm conditions there is a greater effect of elevated atmospheric CO2 on soil CO2 flux and during these times deeper‐rooted species contribute to soil CO2 flux more than average.
•  Although differences in responses to elevated CO2 and nitrogen among species were not great, decreases in diversity can affect belowground carbon allocation depending on the plant traits of the species that are lost from ecosystems.
Stable‐carbon isotopes and soil organic carbon in wheat under CO2 enrichment
Authors: Leavitt S. W. , Pendall E. , Paul E. A. , Brooks T. , Kimball B. A. , Pinter P. J. , Johnson H. B. , Matthias A. , Wall G. W. , LaMorte R. L. 
Published: March 2003

Summary

Stable‐carbon isotopic tracers were enlisted in 1996 and 1997 wheat (Triticum aestivum) free‐air CO2 enrichment (FACE) experiments to detect entry of new C into soil organic carbon (SOC) pools. Any enhanced soil inputs might mitigate rising atmospheric CO2.
The CO2 used to enrich FACE plots (to ambient +190 µmol mol−1) resulted in 13C‐depleted wheat relative to ambient plants and the native SOC. To trace new C in control plots C4‐plant‐derived exotic soils were placed into subplots in high‐N FACE and control treatments, and a 13CO2 gas tracer was pulsed to subplots in high‐N control replicates.
Under high‐N, isotopic mass balance showed 6% (P = 0.003) and 5% (P = 0.04) new C in 0–15‐cm and 15–30‐cm FACE SOC, respectively, after 2 yr. Results from the C4‐soil subplots were ambiguous, but the 13CO2 tracer induced a SOC δ13C increase (P = 0.08) at 15–30 cm in control‐high N consistent with 6% new C.
We infer c. 3% year−1 (30–40 g C m−2 yr−1) SOC turnover in surface soils at high‐N under both ambient and elevated CO2. The 13CO2‐tracer result, however, is less reliable because of lower significance, fewer replicates and heterogeneous isotopic distribution within plants.
Variation in nitrogen‐use efficiency among and within subarctic graminoids and herbs
Authors: Eckstein R. Lutz , Karlsson P. Staffan 
Published: March 2003

Summary

This study addresses the question of whether a trade‐off between the annual nitrogen (N) productivity (aNP) and the mean residence time (MRT), an index of N conservation, occurs both among and within species. We hypothesized that a trade‐off between aNP and MRT observed among species might not hold within species.
Seven perennial graminoids and herbs (including one evergreen) were subjected to two fertilizer concentrations and light intensities. The effect of these treatments was examined on plant traits determining aNP and MRT.
Except for the evergreen Tofieldia pusilla, fertilization had an overriding effect on most variables related to the species’ nitrogen use and the response to fertilization among and within species closely matched. By contrast, shade had minor effects on plant nitrogen use. Across all species, aNP varied inversely with MRT, but within species aNP and MRT were not related.
We suggest that there might not be a trade‐off between aNP and MRT within species because small intraspecific changes in leaf life span may not involve significant consequences for leaf morphology, photosynthesis and growth.
Compression wood has little impact on the water relations of Douglas‐fir (Pseudotsuga menziesii) seedlings despite a large effect on shoot hydraulic properties
Authors: Spicer Rachel , Gartner Barbara L. 
Published: March 2003

Summary• Compression wood has been shown to reduce stem permeability, but it is not known to what extent it affects leaf‐level processes. Here, we report whole‐plant hydraulic properties of Douglas‐fir (Pseudotsuga menziesii) seedlings induced to form varying amounts of compression wood.• Seedlings were grown under three bending treatments to assess the impact of compression wood on hydraulic properties, including stomatal conductance (gs), above‐ground shoot conductance (Kl(abg)), and both specific and leaf area‐specific conductivity (ks and kl, respectively).• Kl(abg) was significantly lower (50% reduction) in severely bent seedlings than in controls. Similarly, both ks and kl of the main axis were significantly reduced (by 52% and 46%, respectively) in severely bent seedlings relative to controls. Seedlings in the moderate bending treatments had ks and kl that were intermediate between controls and severe bending.• Despite clear differences in above‐ground shoot hydraulic properties, severely bent seedlings maintained the same water potentials as controls and had similar diurnal patterns of gs. This suggests that when the entire soil–plant–atmosphere continuum is considered, even a severe reduction in stem ks caused by compression wood has little impact on leaf‐level processes.