bluuebunny/crossref_metadata_2025 huggingface dataset:
NADPH‐diaphorase activity and nitric oxide synthase isoforms in the trophoblast of Calomys callosus
Authors: MORAES NECI , ZAGO DOUGLAS , GAGIOTI SONIA , HOSHIDA MARA SANDRA , BEVILACQUA ESTELA
Published: March 2003

The pattern of expression of a variety of placental nitric oxide synthase isoforms has contributed to elucidating the regulatory mechanisms of nitric oxide (NO) synthesis during gestation. The maintenance of vascular tone, attenuation of vasoconstriction, prevention of platelet and leukocyte adhesion to the trophoblast surface, and possible participation in uterine blood flow seem to be the main functions of NO generated at the fetal‐maternal interface in humans and mice. Extending this knowledge to other rodent species commonly used as laboratory animals, in this study we focus on NADPH‐diaphorase activity and the distribution of nitric oxide synthase isoforms (NOS) in the trophoblast cells of Calomys callosus during different phases of pregnancy. NADPH‐diaphorase activity was evaluated cytochemically and the presence of NOS isoforms detected by immunohistochemistry. These techniques were performed on pre‐ and postimplantation embryos in situ and in vitro, as well as in placentae on d 14 and 18 of pregnancy. Neither NADPH‐diaphorase activity nor inducible or endothelial NOS isoforms were found in pre‐implanting embryos except after culturing for at least 48 h, when some of the embryonic cells were positive for the diaphorase reaction. On d 6·5 of pregnancy, trophoblast cells showed intense diaphorase activity both in situ and under in vitro conditions. A positive reaction was also found in the different placental trophoblast cells on d 14 and 18 of pregnancy. The inducible NOS (iNOS) isoform, but not the endothelial isoform, was immunodetected in trophoblast cells from the placenta and from postimplantation embryos in situ and under in vitro conditions. These results strongly suggest the production of NO by the iNOS isoform in the trophoblast of Calomys callosus after embryo implantation. The data also emphasise a possible role for the trophoblast in producing and releasing cytotoxic molecules at the fetal‐maternal interface.
Changes in aponeurotic dimensions upon muscle shortening: in vivo observations in man
Authors: MAGANARIS CONSTANTINOS N. , KAWAKAMI YASUO , FUKUNAGA TETSUO
Published: March 2003

Aponeurotic deformation measurements have traditionally been taken by loading dissected muscles; thus the values obtained may not reflect in vivo function. In the present study, we estimated dimensional changes in the central aponeurosis of the intact human tibialis anterior muscle upon loading induced by muscle contraction. Measurements were taken in seven males, and involved real‐time ultrasound scanning of the tibialis anterior muscle at 30° of plantarflexion at rest and during isometric dorsiflexion maximum voluntary contraction (MVC). At each contraction state, the length of the aponeurosis, the width along its length, and its area were estimated from sagittal‐plane and axial‐plane sonographs. In the transition from rest to MVC, the length of the aponeurosis increased by 7% (P < 0.05), its width increased by up to 21% (P < 0.05), and its area increased by 17% (P < 0.05). These results indicate that the in vivo tibialis anterior aponeurosis behaves as a compliant material upon active muscle shortening. The methodology employed allows cross‐sectional and longitudinal design investigations, circumventing the problems associated with epimysial removal under in vitro experimental conditions.
Role of immune cells in animal models for inherited neuropathies: facts and visions*
Authors: Mäurer Mathias , Kobsar Igor , Berghoff Martin , Schmid Christoph D. , Carenini Stefano , Martini Rudolf
Published: March 2003

Mice heterozygously deficient in the peripheral myelin adhesion molecule P0 (P0+/− mice) are models for some forms of Charcot–Marie–Tooth (CMT) neuropathies. In addition to the characteristic hallmarks of demyelination, elevated numbers of CD8‐positive T‐lymphocytes and F4/80‐positive macrophages are striking features in the nerves of these mice. These immune cells increase in number with age and progress of demyelination, suggesting that they might be functionally related to myelin damage. In order to investigate the pathogenetic role of lymphocytes, the myelin mutants were cross‐bred with recombination activating gene 1 (RAG‐1)‐deficient mice, which lack mature T‐ and B‐lymphocytes. The immunodeficient myelin mutants showed a less severe myelin degeneration. The beneficial effect of lymphocyte‐deficiency was reversible, since demyelination worsened in immunodeficient myelin‐mutants when reconstituted with bone marrow from wild‐type mice. Ultrastructural analysis revealed macrophages in close apposition to myelin and demyelinated axons. We therefore cross‐bred the P0+/− mice with spontaneous osteopetrotic (op) mutants deficient in the macrophage colony‐stimulating factor (M‐CSF), hence displaying impaired macrophage activation. In the corresponding double mutants the numbers of macrophages were not elevated in the peripheral nerves, and the demyelinating phenotype was less severe than in the genuine P0+/− mice, demonstrating that macrophages are also functionally involved in the pathogenesis of genetically mediated demyelination. We also examined other models for inherited neuropathies for a possible involvement of immune cells. We chose mice deficient in the gap junction component connexin 32, a model for the X‐linked form of CMT. Similar to P0‐deficient mice, T‐lymphocytes and macrophages were elevated and macrophages showed a close apposition to degenerating myelin. We conclude that the involvement of T‐lymphocytes and macrophages is a common pathogenetic feature in various forms of slowly progressive inherited neuropathies.
Blood–brain barrier breakdown and oedema formation in systemic sepsis and human brain tumours
Authors: Davies D. C.
Published: March 2003

Septic encephalopathy (SE) is the commonest form of encephalopathy among patients in intensive care units. SE is associated with breakdown of the blood–brain barrier (BBB) since patients with this condition have high protein levels in their cerebrospinal fluid. Disruption of the BBB and associated oedema is also a common property of brain tumours. Oedema is a significant source of morbidity and mortality in both SE and brain tumours but an understanding of the its pathophysiology is lacking. Perimicrovessel oedema, disruption of associated astrocyte end‐feet and neuronal injury occurs in the brain in a porcine model of acute SE. Expression of the transmembrane protein occludin that is an essential functional component of interendothelial cell tight junctions, is reduced in human cerebral astrocytoma and metastatic adenocarcinoma (MA). This reduction is inversely correlated with the degree of contrast enhancement present on CT and electron microscopy revealed tight junction opening in high grade astrocytoma. Normal astrocytes secrete factors that induce BBB properties in endothelial cells and astroctoma, whereas MA cells secrete VEGF that increases microvessel endothelial permeability. Therefore damage to astrocytes could underlie BBB opening in SE, whilst the neoplastic cells cause a similar effect in astrocytoma and MA. The adrenergic system has been implicated in the inflammatory response to sepsis and it may play a role in the opening of the BBB in SE since the (2 receptor agonist dopexamine inhibits perimicrovessel oedema in septic pigs, whereas the (1 receptor agonist methoxamine causes perimicrovessel oedema formation in controls. However the way in which the adrenergic system is involved in oedema formation remains to be resolved. The amount of oedema fluid present in the brain in SE and tumours must reflect a balance between its production and clearance. The water channel protein aquaporin‐4 (AQP4) is expressed in astrocyte foot processes around microvessels and forming the glial limiting membranes in normal brain. Massive up‐regulation of AQP4 expression occurs in astrocytoma and MA and there is a significant correlation between contrast enhancement on CT and AQP4 expression. This strong correlation suggests that increased AQP4 expression is fundamental to the pathophysiology of brain oedema. However it remains unclear whether the increased AQP4 is functional and if so, whether it enhances oedema formation or clearance. These results suggest that the pathophysiology of brain oedema is multifactorial but that there may be common processes operating regardless of the aetiology.
An investigation of thoracic and lumbar cancellous vertebral architecture using power‐spectral analysis of plain radiographs*
Authors: Buck A. M. , Price R. I. , Sweetman I. M. , Oxnard C. E.
Published: March 2003

The internal architecture of the vertebral bodies spanning the levels T1 to L5 in seven male columns was studied using mammographic‐resolution radiographs of 2.5‐mm‐thick planar parasagittal slices. The overlapping radiographic shadows of vertebral trabeculae combined in the image to form a series of ‘elements’, broadly representative of the cancellous structure. The orientations and sizes of these elements were analysed by applying the Fast Fourier transform (FFT) to the digitized radiographic images. Elements aligned in the ‘vertical’ orientation, along the long axis of the column, were the most prominent for all vertebral levels. The relative prominence of horizontal to vertical elements was generally constant along the column below T5. In contrast, the relative prominence of oblique to vertical elements declined in the cranio‐caudal direction, particularly in individuals aged ≥ 60 years. The ratio of ‘large’ (x > 0.3 mm) to ‘small’ (0.15 mm ≤ x ≤ 0.3 mm) elements was unchanged cranio‐caudally in specimens < 60 years. However, in individuals ≥ 60 years, large elements increased in relative prominence in the caudal direction. These results suggest that a basic orthogonal pattern of trabeculae is found along the male human spine, regardless of differences in vertebral body size. Power‐spectral analysis is shown to yield information summarizing the predominant orientations and sizes of radiographically rendered architectural elements of vertebral cancellous bone, to define the effects of ageing on architecture, and to identify broad structural differences between vertebral levels in the adult male spine.
Apoptosis in the cortex of the developing mouse kidney
Authors: Foley Jonathan G. D. , Bard Jonathan B. L.
Published: March 2003

Published levels of apoptosis in developing rat kidney (∼2.5%) seem large for a tissue with no obvious need for continual cell death. This paper examines the levels and patterns of apoptosis and mitosis in the cortical region of the developing metanephros of the mouse, the standard mammalian model embryo. Using confocal microscopy on specimens stained with propidium iodide to highlight nuclear morphology, optical sections of wholemount kidneys to a depth of ∼50 µm were analysed and mitotic, apoptotic and interphase nuclei counted in the various compartments. Of the ∼200 000 cells examined over E11.5–16.5, 2–3% were mitotic, confirming observations based on cryosections; the mitotic index peaked at E14.5, dropping to ∼0.5% by P14. The mean apoptotic index during this period was 0.28%; this figure from wholemounts was ∼10% of that earlier reported in cryosectioned rat kidneys. One possible explanation for the difference is that cryosectioning turns out to create small nuclear fragments that can stain strongly with propidium. Such fragments are not seen in wholemounts and do not stain with TUNEL. Wholemount mouse E11.5 tails and E16.5 lungs were also analysed and both their mitotic and their apoptotic indexes were similar to those in wholemount developing kidneys. These results show that the level of apoptosis in wholemount embryonic mouse kidney cortex is far less than previously reported in cryosectioned rat embryonic kidneys, and typical of that in other mouse embryonic tissues whose development seems not to require apoptosis.
Optical projection tomography as a new tool for studying embryo anatomy
Authors: Sharpe James
Published: March 2003

Optical projection tomography (OPT) is a new technique for three‐dimensional (3D) imaging of small biological tissues. It is particularly useful for reconstructing vertebrate embryos and for examining the 3D anatomy of developing organs. The advantages of this technique over previous methods will be explained: in particular, its ability to image at a higher resolution than magnetic resonance imaging (MRI), while at the same time being able to image specimens much larger than those possible using confocal laser‐scanning microscopy. Being an optical technique, OPT is also able to take advantage of the many coloured and fluorescent dyes which have been developed for tissue‐specific or gene‐specific staining. This becomes particularly important for the visualization of the 3D shapes of specific organs and tissues as it allows the computer to automatically determine the outline of the desired structure.
Characterization of the host genotype and fungal diversity in Scots pine ectomycorrhiza from natural humus microcosms using isozyme and PCR‐RFLP analyses
Authors: TIMONEN SARI , TAMMI HANNA , SEN ROBIN
Published: March 2003

The early development of indigenous and introduced Scots pine (Pinus sylvestris L.) ectomycorrhiza in natural forest humus was examined using molecular fingerprinting techniques. Non‐mycorrhizal or mycorrhizal (Suillus bovinus (L. ex Fr.) O. Kuntze or Paxillus involutus (Batsch ex Fr.) Fr.) seedlings were placed in transparent two‐dimensional microcosms on a thin layer of sieved humus to allow observation of ectomycorrhizal development and fungal growth. Twelve ectomycorrhizal morphotypes, mainly based on colour, gross morphology and outer mantle structure, were identified over a 3‐month period. No successional trends in mycorrhiza formation were observed. For further characterization, individual ectomycorrhiza representing the different morphotypes were subjected to analyses of esterase (EST) isozyme profiles and RFLPs of the internal transcribed spacer (ITS) from fungal rRNA genes following amplification using PCR. All 10 morphotypes analysed displayed different esterase isozyme profiles, and the characteristic s. bovinus species diagnostic band (S. b. EST8) was detected in two white morphotypes. Ten Pink and Black ectomycorrhiza were all separated into one and three groups, respectively. A fast‐running plant‐specific polymorphic locus (Z) was also confirmed in most ectomycorrhizal morphotypes. Diagnostic species‐specific (S. bovinus and Pink) EST bands were detected in intact external mycelium colonizing soil. Successful amplification of the ITS from individual ectomycorrhiza, of eight different morphotypes, was found to be mainly influenced by the DNA template concentration. Different RFLPs (Hinf I, Mbo I and Hha I) of the ITS placed the white morphotypes into two groups, one corresponding to S. bovinus, in agreement with the esterase fingerprinting. By contrast, Pink and Beige morphotypes displayed different EST profiles but nearly identical RFLP fingerprints. The ITS amplification success rate of standardized DNA template concentrations from 10 individual Pink and Black ectomycorrhiza was 90 and 50%, respectively. In all successful amplifications, the black morphotype yielded the smallest ITS fragment, similar to earlier reports for Cenococcum geophilum, that gave identical RFLPs. The ecological significance of the observed mycorrhizal diversity and combined application of these two identification methods is discussed.
Effects of potassium deficiency on cell water relations and elongation of tap and lateral roots of maritime pine seedlings
Authors: TRIBOULOT MARIE‐BÉATRICE , PRITCHARD JEREMY , LEVY GÉRARD
Published: March 2003

The effects of potassium deficiency (KD) and all‐macronutrient deficiency (MD) on elongation of tap and lateral roots were studied on maritime pine seedlings (Pinus pinaster Ait.) in hydroponic culture.

Tap root elongation was unaffected by either of the two deficiencies. By marked contrast, lateral root elongation was strongly reduced. The analyses of cell turgor pressure and relative elemental growth rate (REGR) profile in the growing zone allowed us to determine the effects of the nutrient stresses on cell‐wall properties. For both deficiency treatments, elongation rate, REGR profile (measured only for control and KD) and turgor pressure in the fastest growing cells were unaffected in the tap root, suggesting that KD and MD did not modify cell‐wall properties in the growing zone. In lateral roots, KD shortened the growing zone and significantly reduced REGR. However, turgor pressure remained unaffected in this region. The absence of turgor pressure change suggests that KD reduced elongation of lateral roots by tightening cell walls. In mature cells of the two types of roots, turgor and osmotic pressures tended to be reduced by the nutrient deficiencies, indicating that these parameters were better maintained in the growing cells.

Cell turgor and osmotic pressures of control plants were 0.1 MPa lower at 30 mm (mature cells) than at 2–4 mm (expanding cells) from the meristem. Moreover, these parameters were 0.1 MPa lower in expanding cells of lateral roots than in those of tap the root. Turgor and osmotic pressures were not homogeneous throughout the root system and were affected differently by the nutrient deficiencies depending on the location in the root system.
Cloning plant genes differentially during colonization of roots of Hordeum vulgare by the vesicular—arbuscular mycorrhizal fungus Glomus intraradices
Authors: MURPHY P. J. , LANGRIDGE P. , SMITH S. E.
Published: March 2003

A model system was developed for the molecular analysis of plant‐mycorrhizal fungus interactions using Hordeum vulgare cv. Galleon and Glomus intraradices Schenk and Smith. High levels of early‐colonization stage mycorrhizas (20–35 % of the total root length) were routinely obtained in the roots of 12–14–d‐old barley seedlings. Detailed colonization studies showed that most colonization occurred in the first 5–10 lateral roots, and that colonization in primary roots and younger lateral roots was low. Differential screening of a cDNA library prepared from the highly colonized region of the root system and subsequent northern analyses identified four differentially expressed cDNA clones. Two clones, BMR6 and BMR78, detect RNA transcripts that accumulate to much higher levels in mycorrhizal roots than in non‐mycorrhizal root tissues. DNA hybridization analysis confirmed that both of the clones were of plant rather than fungal origin. Hybridization and sequence analysis strongly suggests that BMR78 represents a partial cDNA of a low copy proton‐ATPase gene. This finding is consistent with the extensive proliferation of the periarbuscular membrane and high ATPase activity associated with it. BM6 detects a low copy gene whose function is unknown.
In vivo manipulation of cuticular water permeance and its effect on stomatal response to air humidity
Authors: KERSTIENS GERHARD
Published: March 2003

summary

Cuticular water permeance was manipulated in Corylus avellana L., Hypericum androsaemum L. and Populus tremula L. by (1) long‐term application of low doses of various systemic herbicides inhibiting biosynthesis of cuticular waxes, (2) very short‐term application of organic solvents to the leaf surface, and (3) exposure to natural strong winds. Treatment effects were very variable, but increased the natural range of permeances by a factor of 10 or so in undamaged leaves. All species had hypostomatous leaves. Relative change of leaf conductance (g) in response to stepwise increases of leaf‐to‐air water vapour pressure difference (VPD) was measured for individual leaves (Corylus) or groups of leaves at the shoot or branch tip. Adaxial cuticular water permeance (P) was determined for the same leaves after measurement of the VPD‐response. A proportional measure of relative change of g with VPD, d(log e.g)dVPD, was then plotted against P. No increase in the strength of the closing response to increasing VPD was found with increasing P, as would have been expected if water loss through the cuticle was involved in stomatal response to changes in VPD via a direct effect on guard cell turgor. By contrast, high P coincided, most clearly in Corylus, with a reduced strength of the stomatal closing response to increasing VPD, i.e. less negative d(logeg)dVPD. As the responses were non‐linear, the value of d(logeg)dVPD changed with VPD. With rising VPD, all three species and a fourth one previously studied showed a decline in the value of [d(logeg)dVPD]/d(log P), reaching negative values in one species. This is interpreted in terms of two independent and antagonistic effects of increased cuticular water permeance on guard cell response to VPD, one acting by reducing the backpressure exerted on guard cells by the epidermis, and the other one possibly causing greater depression of guard cell turgor through delivery of more chemical messengers (such as abscisic acid) to the guard cells with the cuticular transpiration stream.
The influence of air pollution on the concentration of mineral elements, on the spectral reflectance response and on the production of stress–ethylene in the lichen Ramalina duriaei
Authors: GARTY J. , KLOOG N. , WOLFSON R. , COHEN Y. , KARNIELI A. , AVNI A.
Published: March 2003

summary

Two parameters were applied to estimate the degree of stress induced by exposure of the lichen Ramalina duriaei (De Not.) Bagl. to air pollution in urban‐industrial sites in Israel. Changes in the spectral reflectance response of the thallus and in the production of stress‐ethylene, were compared with the concentration of sulphate‐S, V, Ni, K, Pb, P, Cu, Cr, Fe, Mn and Mg in either in situ or in transplanted thalli of the lichen.

The concentrations of Cu, Mg, Fe, Ni, Pb, V, Cr, Mn and sulphate‐S in in situ thalli collected in a nature reserve in an industrial town (Ashdod, SW Israel) were higher than those detected in in situ thalli collected in a forest (HaZorea Forest) in the north‐east of Israel. The high concentrations of these mineral elements in R. duriaei from the nature reserve coincided with a high rate of production of stress‐ethylene and with a low normalized difference vegetation index (NDVI) indicating that changes in the spectral reflectance response relate to damage to the chlorophyll.

Lichens collected in the unpolluted forest in February 1994, either resuspended in the same site or transplanted in nine sites in the Ashdod region, and retrieved in November of the same year, contained a higher concentration of sulphate‐S, Pb, Cu, Ni, V and Cr in the urban‐industrial sites than in most of the rural localities. Statistical analysis revealed a positive correlation between the amount of ethylene produced by R. duriaei and the concentration of V and Ni in the same thalli.

To test the integrity of the ethylene‐producing system, lichens were soaked in either 5 mM or 10 mM FeCl2 at pH 3–7. Thalli exposed to a very polluted environment produced less ethylene after this treatment. The NDVI correlated positively with the concentration of K in the thallus but negatively with the concentration of Mn, Ni, Pb and sulphate‐S in the same material.

It may be concluded that the in situ thalli of R. duriaei in the nature reserve are severely stressed and possibly‐endangered by the pollution produced by the combustion of heavy fuel oil in the local power plant and oil refineries and by acid rain.
The detection of Glomus spp. (arbuscular mycorrhizal fungi) forming mycorrhizas in three plants, at different stages of seedling development, using mycorrhiza‐specific isozymes
Authors: TISSERANT B. , BRENAC V. , REQUENA N. , JEFFRIES P. , DODD J. C.
Published: March 2003

A series of glasshouse experiments was used to determine mycorrhiza‐specific isozymes (MSIs) produced by five species of Glomus colonizing roots of a desert shrub legume (Anthyllis cytisoides L.), Thymus vulgaris L. and Allium porrum L. over time. Extracts of colonized roots were electrophoresed on non‐denaturing polyacrylamide gels (PAGE) and stained for 10 different enzymes. Staining protocols for esterase, glutamate oxaloacetate transaminase, alkaline phosphatase and malate dehydrogenase provided MSIs for the mycorrhizas formed by different arbuscular mycorrhizal (AM) fungi that had colonized roots of the three host plants. There was no apparent correlation between levels of colonization or arbuscular intensities, at or between each sampling, and the presence of MSIs. The development of colonization by the AM fungi differed little between the three plants when assessed with two methods of estimating fungal biomass. The variety of MSIs detected might reflect the diversity of metabolic activities of these Glomus species and, possibly, differing ecological functions. The high‐level induction of two alkaline phosphatase MSIs in the mycorrhizas of Anthyllis cytisoides colonized by Glomus microaggregatum BEG56 was used to track the fate of this fungus when the same plant was inoculated and transplanted into a semi‐arid site in south‐east Spain. The probable fungal origin of the isozyme was indicated by detection of the same isozyme in the extraradical mycelium formed by Glomus microaggregatum BEG56 on Allium porrum. The use of MSIs to detect the mycorrhizas of species of Glomus in colonized roots is discussed.
Is the threshold size for flowering in Cynoglossum officinale fixed or dependent on environment?
Authors: DE JONG TOM J. , GOOSEN‐DE ROO LEENTJE , KLINKHAMER PETER G. L.
Published: March 2003

In the monocarpic perennial Cynoglossum officinale L. the probability of flowering is related to the size of the plant. In previous work it was observed that this relation varies between years. We hypothesized that variable conditions during the winter, the period of vernalization, explain this variation.

We collected plants from the field in autumn and placed these under different simulated winter conditions in a climate room. In contrast to our hypothesis, the probability of initiating flowering at a given size was not affected by: (a) the temperature during the cold period, (b) the duration of the cold period, or (c) the application of a plant hormone (GA3) or an inhibitor of gibberellin synthesis (paclobutazol) during the cold period. Winter cold is not necessary for floral initiation, and is only required for elongation of the inflorescence. It is unlikely that winter temperature affects the fraction of plants flowering.

Subsequent morphological investigation of flower development in material collected in the field showed that large plants had primordial inflorescences well before vernalization, sometimes as early as August. In plants grown from seeds under constant conditions in a climate room, the probability of initiating the inflorescence differed for plants grown at various temperatures (34·1% at 15°C, 100% at 20°C, and 95% at 25°C). Our results suggest that environmental conditions in August and September, up to 10 months before actual flowering, could affect the fraction of flowering plants.
Structure and function of the ectomycorrhizal association between Paxillus involutus and Betula pendula. II. Metabolic changes during mycorrhiza formation
Authors: BLAUDEZ D. , CHALOT M. , DIZENGREMEL P. , BOTTON B.
Published: March 2003

Seedlings of Betula pendula Roth. were grown in the presence of Paxillus involutus (Batsch) Fr., and metabolic changes during mycorrhiza formation were examined by measuring organic acid and amino acid pools and related enzyme activities, following sequential harvests. Glutamine, aspartate and asparagine pools were always lower in infected roots than in non‐infected roots, especially during Hartig net initiation and formation. Glutamate concentration was similar in both tissues. Citrate and malate were the two major organic acids detected and their concentrations were equal in infected and non‐infected roots. Aspartate aminotransferase, glutamine synthetase, NAD‐dependent malate dehydrogenase and glucose‐6‐phosphate dehydrogenase activities were higher in infected roots than non‐infected roots. For all enzymes revealed on polyacrylamide gels, both root and fungal isoforms were present in infected roots. Quantitative changes in enzyme capacities and metabolite pools indicated that mycorrhiza formation caused a re‐arrangement of the main metabolic pathways during the very early stages following contact, which might be related to the structural changes.
Impacts of tropospheric ozone and airborne nitrogenous pollutants on natural and semi‐natural ecosystems: a commentary
Authors: BOBBINK ROLAND
Published: March 2003

Man's activities pose a number of threats to the functioning, structure and diversity of natural and semi‐natural ecosystems. One of the main threats is the increase in concentrations in air pollutants in this century (Wellburn, 1988; Tamm, 1991). This paper is a commentary on the effects of tropospheric ozone (O3) and airborne nitrogen deposition (both oxidized (NOx) and reduced (NHy) compounds) on natural and semi‐natural ecosystems, based upon the oral presentations and the discussions during the Symposium, extended with a personal overview and some suggestions about future challenges for research. The most important effects of these air pollutants on natural and semi‐natural vegetation are summarized and evaluated in ecological terms, with respect to the functioning and structure of unaffected systems. Air pollutants are transported over both short and long distances (as far as a few thousand km) before being deposited on surface water, vegetation or soil. In this way, vegetation over a large area or in remote regions can be influenced by airborne pollutants (see Fowler et al. (1998); Asman, Sutton & Schjørring (1998)).
Effects of ozone on wild plants
Authors: DAVISON A. W. , BARNES J. D.
Published: March 2003

Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi‐natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting/grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant‐induced changes in ecosystems.
Influences of atmospheric CO2 enrichment on the responses of sugar maple and trembling aspen to defoliation
Authors: KRUGER ERIC L. , VOLIN JOHN C. , LINDROTH RICHARD L.
Published: March 2003

Impacts of defoliation on the growth and physiology of sugar maple (Acer saccharum Marsh.) and trembling aspen (Populus tremuloides Michx.) were examined in ambient and CO2‐enriched atmospheres. Saplings were grown for 70 d in controlled environments, wherein CO2 mole fractions averaged either 356 μmol mol−1 or 645 μmol mol−1, under a PPF of 500 μmol m−2 s−1. On day 49 of the study, 50% of the leaf area was removed from a subset of each species in both CO2 environments. Relative growth rate (rgr) and its physiological and morphological determinants were monitored before and after defoliation. For non‐defoliated saplings of both species, a slight stimulation of rgr (c. 5%) in elevated CO2 led to a modest increase (9–11%) in final sapling weight. In the case of maple, the minimal growth response corresponded with minor CO2 effects on specific leaf area (sla) and leaf weight ratio (lwr), and an apparent CO2‐induced down‐regulation of photosynthetic metabolism. For aspen, the CO2 stimulation of photosynthesis was largely offset by a decrease in sla. Responses to defoliation differed markedly between species and CO2 environments. Defoliation decreased maple rgr in ambient CO2, whereas the opposite occurred in elevated CO2. The latter led to complete recovery of plant weight (compensation), and was attributed to a defoliation‐induced increase in carbon allocation to new leaves, along with a reversal of photosynthetic CO2 acclimation in that foliage. In both environments, aspen rgr increased after defoliation, facilitating almost full compensation. Defoliation increased light penetration into the aspen canopy, and it was estimated that the resultant stimulation of photosynthesis in lower leaves would have more than offset the concomitant decrease in lwr. CO2 enrichment might substantially enhance the ability of certain tree species to recover from herbivory. Moreover, responses to elevated CO2 might be largest in the presence of stresses, such as herbivory, that decrease plant source∶sink ratios.
Growth and C allocation of Populus tremuloides genotypes in response to atmospheric CO2 and soil N availability
Authors: KUBISKE MARK E. , PREGITZER KURT S. , ZAK DONALD R. , MIKAN CARL J.
Published: March 2003

We grew cuttings of two early (mid Oct.) and two late (early Nov.) leaf‐fall Populus tremuloides Michx. genotypes (referred to as genotype pairs) for c. 150 d in open‐top chambers to understand how twice‐ambient (elevated) CO2 and soil N availability would affect growth and C allocation. For the study, we selected genotypes differing in leaf area duration to find out if late‐season photosynthesis influenced C allocation to roots. Both elevated CO2 and high soil N availability significantly increased estimated whole‐tree photosynthesis, but they did so in different ways. Elevated CO2 stimulated leaf‐level photosynthesis rates, whereas high soil N availability resulted in greater total plant leaf area. The early leaf‐fall genotype pair had significantly higher photosynthesis rates per unit leaf area than the late leaf‐fall genotype pair and elevated CO2 enhanced this difference. The early leaf‐fall genotype pair had less leaf area than the late leaf‐fall genotype pair, and their rate of leaf area development decreased earlier in the season. Across both genotype pairs, high soil N availability significantly increased fine root length production and mortality by increasing both the amount of root length present, and by decreasing the life span of individual roots. Elevated CO2 resulted in significantly increased fine root production and mortality in high N but not low N soil and did not affect fine root life span. The early leaf‐fall genotype pair had significantly greater fine root length production than the late leaf‐fall genotype pair across all CO2 and N treatments. These differences in belowground C allocations are consistent with the hypothesis that belowground C and N cycling is strongly influenced by soil N availability and will increase under elevated atmospheric CO2. In addition, this study reinforces the need for better understanding of the variation in tree responses to elevated CO2, within and among species.
Temporary phosphorus partitioning in mycelial systems of the cord‐forming basidiomycete Phanerochaete velutina
Authors: WELLS JOHN M. , HARRIS MELANIE J. , BODDY LYNNE
Published: March 2003

Mycelial cord systems, up to 50‐cm diameter, of the basidiomycete Phanerochaete velutina (DC.: Pers.) Parmasto, a common woodland saprotroph, grown on non‐sterile soil in model laboratory microcosms were baited, after 27 d, with pairs of fresh beech wood blocks (baits), placed at 10 d intervals behind the foraging colony margin. System development was quantified by image analysis. Mean radial extent and hyphal cover increased linearly with time until day 21, but declined before the mycelial systems reached the edges of the laboratory microcosms. The mass (DBM) and border (DBS) fractal dimensions of the mycelial systems changed with time but the ratio DBM∶DBS became constant after 14 d. A separate central compartment containing the inoculum was supplied with 32P orthophosphate and its translocation to wood baits monitored non‐destructively for 73 d. Whilst total 32P acquisition by wood baits increased linearly with time, the proportion of total allocated to baits varied significantly both temporally and according to the length of time that baits had been in contact with the mycelium. Most recently supplied wood baits were not the main sink for supplied phosphorus; rather, the rate of
32P acquisition was initially greatest in baits from which egress of the fungus had already occurred. The rate of
32P acquisition by the most recently added baits increased with time, supported by efflux from other wood baits, which had initially been the main sinks for translocated phosphorus. The results raise important questions about the ecological and functional significance of nutrient partitioning in cord systems and imply that ‘observed’ translocation, rather than being an absolute measure, indicates the degree to which phosphorus is loaded from a translocation stream in regions where it is being actively utilized and/or stored.
Implications of missing efflux sites on convective ventilation and amino acid metabolism in Phragmites australis
Authors: ROLLETSCHEK H. , BUMILLER A. , HENZE R. , KOHL J.‐G.
Published: March 2003

Three stands of Phragmites australis (Cav.) Trin. ex Steudel were investigated regarding the relationship between the number of efflux culms and convective ventilation efficiency affecting the hypoxic status of roots and rhizomes. The lack of old (efflux) culms after mowing the preceding winter caused a significantly higher counterpressure within the rhizome, thereby diminishing air flushing rate, i.e. oxygen supply, of rhizomes. The levels of alanine and c‐aminobutyric acid in basal culm internodes increased significantly. Both amino acids indicate the hypoxic status of the root and rhizome metabolism of P. australis. Amino acid patterns of the basal culm internodes are discussed with respect to the maintenance of aerobic root metabolism and nutrient availability.
Influence of plant age on ozone resistance in Plantago major
Authors: LYONS T. M. , BARNES J. D.
Published: March 2003

The impact of O3 at different stages of plant development was investigated in growth‐chamber‐cultivated Plantago major L. Six‐d‐old plants of an O3‐sensitive population (‘Valsain’) were exposed to one of the following six treatments; 56 d charcoal/Purafil®‐filtered air (CFA): 56 d CFA plus 70 nmol mol−1 O3 for 7 h d−1; CFA with a 14‐d episode of O3 administered at days 1, 14, 28 or 42. Harvests were made every 14 d, and at the final harvest (56 d) the influence of O3 on reproductive structures was assessed.

Analysis of the effects of O3 on growth and reproductive performance confirmed the sensitivity of the population to the pollutant. In the absence of the development of typical visible symptoms of foliar damage, the total d. wt of plants maintained in O3 over a 56‐d period was 35% lower than that of control plants. However, the impact of the pollutant was found to decrease as plants aged. Plant relative growth rate (R) was only affected in seedlings, suggesting that effects of O3 on seedling growth were largely responsible for the decrease in accumulated biomass; the growth rate of older plants was not affected by O3. The observed shift in O3 resistance with plant age was mediated by both ‘acclimation’ and ontogenetic changes. ‘Acclimation’ was not associated with changes in O3 uptake, and there was some evidence to support the existence of compensatory growth responses. In addition to effects on vegetative growth, plants exhibited an O3‐induced decline in reproductive performance; O3 reducing the number of flower spikes and seed capsules produced per plant. Ozone episodes administered at different stages of development indicated that reproductive development was particularly sensitive to O3 during the early stages of flowering.

The findings of this study are discussed in relation to evolutionary adaptation to O3 in natural plant communities.The importance of plant age, prior exposure to the pollutant and the timing of O3 episodes in relation to plant developmental stage are highlighted.
Molecular determination of genetic variation in Pisolithus isolates from a defined region in New South Wales, Australia
Authors: ANDERSON I. C. , CHAMBERS S. M. , CAIRNEY J. W. G.
Published: March 2003

Sixty‐two isolates of Pisolithus were obtained from a carpophore population collected from a 90‐km2 area of New South Wales, Australia. Random amplified polymorphic DNA (RAPD) analysis was used initially to screen isolates for variation, and restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer (ITS) region and ITS sequence analysis were subsequently performed on selected isolates. ITS–RFLP and ITS sequence analysis indicated that two isolates (LJ07 and WM01) from different sites were considerably different from all other isolates, a strict consensus tree generated by bootstrap analysis of sequence data strongly suggesting that isolates LJ07 and WM01 represent a separate Pisolithus species. Although the general morphology of carpophores and basidiospores of the majority of collected isolates was consistent with previous descriptions of P. tinctorius (Pers.) Coker and Couch, basidiospore characteristics suggest that isolates LJO7 and WMO1 might represent a Pisolithus species distinct from P. tinctorius and the previously described Australian species, P. microcarpus (Cooke & Massee) G. Cunn.
Response to three seasons of elevated ozone in the progeny of healthy and unhealthy Norway spruce trees from a plantation with the ‘top dying’ syndrome
Authors: LEVERENZ J. W. , PALUDAN‐MÜLLER G. , SAXE H.
Published: March 2003

We tested a hypothesis that elevated ozone was an eliciting or contributing factor in outbreaks of the ‘top dying’ (or ‘subtop dying’) syndrome in Norway spruce (Picea abies). Progeny were used from open‐pollinated trees within a stand with the ‘top dying’ syndrome. The mother trees were classified in relation to the expression of the ‘top dying’ syndrome, and progeny from the healthiest and least healthy thirds of the population were exposed to high and low concentrations of ozone for three seasons. Elevated ozone did not affect height growth of the trees. It did not measurably affect net photosynthesis, stomatal conductance or instantaneous water use efficiency. Chlorophyll and carotenoid contents were also not significantly affected by ozone concentration. In the first year, instantaneous water use efficiency was lower in the progeny of the unhealthy mother trees than in the healthy mother trees. Furthermore, the unhealthy mother trees tended to produce longer annual shoots and showed more winter damage at the end of the experiment. None of these parameters were related to ozone concentration in the atmosphere. These results do not support a hypothesis that elevated ozone is a significant contributory factor or an eliciting factor in the development of the syndrome.
Dynamics of mycelial growth and phosphorus partitioning in developing mycelial cord systems of Phanerochaete velutina: dependence on carbon availability
Authors: WELLS JOHN M. , HARRIS MELANIE J. , BODDY LYNNE
Published: March 2003

Mycelial cord systems, up to 50 cm in diameter, of the basidiomycete Phanerochaete velutina, a common woodland saprotroph, were grown on unsterile soil in model laboratory microcosms from either 4 or 16 cm3 wood inocula.
After 48 d, systems were supplied at 10‐d intervals with pairs of new 4 cm3 beechwood resources placed behind the foraging colony margin, where possible on opposite sides of the system. Image analysis was used to quantify radial extension, hyphal cover, the mass (DBM) and surface fractal (DBS) dimensions of the mycelial systems and wood‐resource bleaching activity. Mycelial systems developing from small inocula had significantly (P0.05) lower radial extension rates, hyphal cover and DBM∶DBS ratio than those from large inocula. Initially, systems developing from small inocula also displayed significantly (P<0.05) slower wood‐resource bleaching activity than those from large inocula, suggesting that carbon limitation affected both foraging behaviour and resource utilization. A separate central compartment containing the inoculum was supplied with 32P orthophosphate and its partitioning amongst wood resources was monitored nondestructively for 44 d. Total 32P acquisition by wood resources was not significantly (P>0.05) affected by inoculum resource size. However, the proportion of total acquired P allocated to resources, which varied according to the length of time that resources had been in contact with the mycelium, was dependent upon inoculum size. The results support the hypothesis that phosphorus translocation is not a demand‐driven process. We suggest that the time taken before the greatest rate of phosphorus withdrawal from a uniform translocation stream is dependent upon prior availability of carbon within colonized resources.
Tribology of the root cap in maize (Zea mays) and peas (Pisum sativum)
Authors: BENGOUGH A. G. , KIRBY J. M.
Published: March 2003

Frictional resistance to a penetrating body can account for more than 80% of the total resistance to penetration of soil. We measured the frictional resistance between growing root caps of maize and pea and ground and smooth glass surfaces, which was linearly correlated to load, allowing calculation of the coefficient of kinetic friction and adhesion. Coefficients of kinetic friction between the root caps and the ground and smooth glass surfaces were approximately 0.04 and 0.02, respectively, the first measurements of the frictional properties of root tips at rates approaching those of root elongation, and an order of magnitude smaller than those previously reported. Results suggest that roots are well designed for penetrating soil, and encounter only small frictional resistance on the root cap. These data provide important parameters for modelling soil stresses and deformation around growing root tips.
Effects of geminivirus infection and growth irradiance on the vegetative growth and photosynthetic production of Eupatorium makinoi
Authors: FUNAYAMA S. , TERASHIMA I.
Published: March 2003

Eupatorium makinoi plants with or without geminivirus infection were grown in shading frames with 70, 15 and 5.5% sunlight. Growth characteristics of these plants in the early vegetative phase were compared by means of growth analysis. We also measured leaf photosynthetic gas exchange rates and examined relationships between leaf photosynthesis and whole‐plant growth. Relative growth rate (RGR=(1/W)×(dW/dt), where W is plant dry mass) of virus‐infected plants was lower than that of uninfected plants under all three light conditions. The reduction of RGR by infection was increased with irradiance. The net assimilation rate (NAR=(1/A)×(dW/dt), where A is total leaf area of the plant) was also reduced both by infection and shading. NARs that were estimated from light‐response curves of leaf photosynthesis, in situ measurements of irradiance, and respiration rates of leaves, stems and below‐ground parts, agreed very well with the values obtained by conventional growth analysis techniques. Decreases in the estimated NAR value from infection and shading were mostly explained by the decreases in leaf photosynthesis. These results clearly showed that lowered RGR in virus‐infected plants was attributed mainly to impaired photosynthesis in virus‐infected leaves.