bluuebunny/crossref_metadata_2025 huggingface dataset:
Hair bundle profiles along the chick basilar papilla
Authors: DUNCAN R. K. , ILE K. E. , DUBIN M. G. , SAUNDERS J. C.
Published: March 2003

Cochlear hair cells play a central role in the transduction of sound into neural output. Anatomical descriptions of these cells, and their protruding hair bundles, are of fundamental interest since hair cell transduction is dependent on hair bundle micromechanics and hair bundle micromechanics depends on hair bundle morphology. In this paper, we describe quantitatively changes in the staircase profile of the hair bundle along the apical portion of the chick's basilar papilla. Images of hair cells from 8 discretely dissected segments of the apical 3rd of the basilar papilla were archived, and the profile contour outlined by the tips of the stereocilia was digitised and curves were fitted by linear and power equations. The hair bundles of tall hair cells exhibited both linear and curvilinear profiles, which were equally distributed along the papilla. All short hair cells in our sample had straight contours. The differences in hair bundle shape among the tall hair cells may lead to differential susceptibility to injury and some variance in the current‐displacement transduction curves due to differences in the translation of forces throughout the hair bundle.
Immunolocalisation of the janus kinases (JAK)—signal transducers and activators of transcription (STAT) pathway in human epidermis
Authors: NISHIO HAJIME , MATSUI KIYOSHI , TSUJI HIROKO , TAMURA AKIYOSHI , SUZUKI KOICHI
Published: March 2003

The janus kinases (JAK) and signal transducers and activators of the transcription (STAT) pathway have been shown to be activated by a number of cytokines or growth factors and to play significant roles in the differentiation of various cell types. In the present study, we investigated the distribution of the JAK–STAT pathway using immunohistochemistry in the human epidermis. Each element of the pathway showed abundant and differential expression in the epidermis. The differential distribution of the elements was most strikingly observed in the horny keratinised cell and granular layers of the epidermis. JAK2, JAK3, STAT1 and STAT5 were expressed in high amounts, and JAK1, TYK2, STAT2, STAT3, STAT4 and STAT6 to a much lesser extent in the horny cell layer. JAK3, TYK2, STAT2, STAT3, STAT4 and STAT6 were more abundantly expressed in the granular layer than the lower layers of the epidermis. JAK1, STAT1 and STAT5 were expressed at almost the same levels in the various layers of the epidermis. These results show that elements of the JAK–STAT pathway are abundantly and differentially expressed in the epidermis. It is suggested that each element of the pathway may play a role at a distinct stage of keratinocyte differentiation.
Ossification in the human calcaneus: a model for spatial bone development and ossification
Authors: FRITSCH HELGA , BRENNER ERICH , DEBBAGE PAUL
Published: March 2003

Perichondral bone, the circumferential grooves of Ranvier and cartilage canals are features of endochondral bone development. Cartilage canals containing connective tissue and blood vessels are found in the epiphysis of long bones and in cartilaginous anlagen of small and irregular bones. The pattern of cartilage canals seems to be integral to bone development and ossification. The canals may be concerned with the nourishment of large masses of cartilage, but neither their role in the formation of ossification centres nor their interaction with the circumferential grooves of Ranvier has been established. The relationships between cartilage canals, perichondral bone and the ossification centre were studied in the calcaneus of 9 to 38‐wk‐old human fetuses, by use of epoxy resin embedding, three‐dimensional computer reconstructions and immunhistochemistry on paraffin sections. We found that cartilage canals are regularly arranged in shells surrounding the ossification centre. Whereas most of the shell canals might be involved in the nourishment of the cartilage, the inner shell is directly connected with the perichondral ossification groove of Ranvier and with large vessels from outside. In this way the inner shell canal imports extracellular matrix, cells and vessels into the cartilage. With the so‐called communicating canals it is also connected to the endochondral ossification centre to which it delivers extracellular matrix, cells and vessels. The communicating canals can be considered as inverted ‘internal’ ossification grooves. They seem to be responsible for both build up intramembranous osteoid and for the direction of growth and thereby for orientation of the ossication centre.
Endothelial barriers: from hypothetical pores to membrane proteins*
Authors: Firth J. A.
Published: March 2003

The anatomical counterpart of the physiologically defined small pore system of capillary endothelia has proved difficult to establish. In non‐brain continuous capillaries, the contributions of caveolar and transmembrane pathways are likely to be small and paracellular clefts are probably the dominant routes. Analogy with epithelial paracellular pathways suggests that tight junctions may be the most restrictive elements. However, structural features of tight junction‐based models are incompatible with physiological data; it is more likely that the tight junction acts as a shutter limiting the available cleft area. Proposed molecular sieves elsewhere in the paracellular pathway include the glycocalyx and the cadherin‐based complexes of the adherens junctions. The molecular architecture of tight junctions and adherens junctions is moderately well defined in terms of molecular species, and there are differences at both sites between the endothelial and epithelial spectra of protein expression. However, definition of the size‐restricting pore remains elusive and may require structural biology approaches to the spatial arrangements and interactions of the membrane molecular complexes surrounding the endothelial paracellular clefts.
Complementary actions of VEGF and Angiopoietin‐1 on blood vessel growth and leakage*
Authors: Thurston Gavin
Published: March 2003

Vascular endothelial growth factor (VEGF) and Angiopoietins are families of vascular‐specific growth factors that regulate blood vessel growth, maturation and function. To learn more about the effects of these factors in vivo, we have overexpressed VEGF‐A or Angiopoietin‐1 (Ang1) in two systems in mice, and examined the effects on blood vessel growth and function. In one set of studies, VEGF, Ang1, or both factors, were transgenically overexpressed in the skin under the keratin‐14 (K14) promoter. The skin of mice overexpressing VEGF (K14‐VEGF) had numerous tortuous, capillary‐sized vessels which were leaky to the plasma tracer Evans blue under baseline conditions. In contrast, the skin of mice overexpressing Ang1 (K14‐Ang1) had enlarged dermal vessels without a significant increase in vessel number. These enlarged vessels were less leaky than those of wild‐type mice in response to inflammatory stimuli. In double transgenic mice overexpressing VEGF and Ang1, the size and number of skin vessels were both increased; however, the vessels were not leaky. In a second set of studies, VEGF or Ang1 was systemically delivered using an adenoviral approach. Intravenous injection of adenovirus encoding VEGF (Adeno‐VEGF) resulted in widespread tissue oedema within 1–2 days after administration, whereas injection of Adeno‐Ang1 resulted in the skin vessels becoming less leaky in response to topical inflammatory stimuli or local injection of VEGF. The decreased leakage was not accompanied by morphological changes. Thus, overexpressing VEGF appears to promote growth of new vessels accompanied by plasma leakage, whereas overexpressing Ang1 promotes the enlargement of existing vessels and a resistance to leakage. Further understanding of the interrelationship of these factors during normal development could lead to their application in the treatment of ischaemic diseases.
Rheological and ultrastructural properties of bovine vaginal fluid obtained at oestrus
Authors: Rutllant J. , López‐Béjar M. , Santolaria P. , Yániz J. , López‐Gatius F.
Published: March 2003

The properties of cervical–vaginal fluid are under strict hormonal control: and in mammals in which semen is deposited in the anterior vagina, changes produced in these properties can result in a lower or higher resistance to sperm motion. The aim of this study was to determine whether the structural organization of bovine vaginal fluid is related to its rheological properties. Vaginal fluid samples were collected from 41 cows at oestrus: 20 at the middle of oestrus (between 8 and 12 h after starting) and 21 at the end of oestrus (between 18 and 22 h). Flow behaviour was determined using a viscosimeter, and the ultrastructural analysis was performed by scanning electron microscopy. Six samples showed newtonian behaviour: three collected at the middle and three collected at the end of oestrus. Newtonian samples had dense and compact matrices arranged as membranes with rough, irregular surfaces, and sparse, thin filaments (< 150 nm). Non‐newtonian samples collected at the end of oestrus (n = 18) had a higher (P = 0.016) consistency index (K = 944 ± 229 mPa.sn) than those collected at the middle of oestrus (n = 17; K = 237 ± 84 mPa.sn). Thick filaments (> 700 nm) that were either randomly arranged with thinner filaments forming a mesh or heavily cross‐linked by thin filaments (50–150 nm) were observed in all non‐newtonian samples collected at the end of oestrus, while medium‐diameter filaments (between 200 and 500 nm) forming loose networks were observed in non‐newtonian samples collected at the middle of oestrus. These findings indicate a close relationship between the molecular organization of the structural elements of bovine vaginal fluid and its rheological behaviour. Vaginal fluid dramatically reduces its mechanical barrier effect during the course of oestrus but always appears to maintain its three‐dimensional filamentous structure. The images of vaginal fluid showing newtonian behaviour would appear to support previous results, suggesting that this property may be related to bovine infertility.
Development of pharyngeal arch arteries in early mouse embryo
Authors: Hiruma Tamiko , Nakajima Yuji , Nakamura Hiroaki
Published: March 2003

The formation and transformation of the pharyngeal arch arteries in the mouse embryo, from 8.5 to 13 days of gestation (DG), was observed using scanning electron microscopy of vascular casts and graphic reconstruction of 1‐µm serial epoxy‐resin sections. Late in 8.5–9DG (12 somites), the paired ventral aortae were connected to the dorsal aortae via a loop anterior to the foregut which we call the ‘primitive aortic arch’, as in the chick embryo. The primitive aortic arch extended cranio‐caudally to be transformed into the primitive internal carotid artery, which in turn gave rise to the primitive maxillary artery and the arteries supplying the brain. The second pharyngeal arch artery (PAA) appeared late in 9–9.5DG (16–17 somites), and the ventral aorta bent dorsolaterally to form the first PAA anterior to the first pharyngeal pouch by early in 9.5–10DG (21–23 somites). The third PAA appeared early in 9.5–10DG (21–23 somites), the fourth late in 9.5–10DG (27–29 somites), and the sixth at 10DG (31–34 somites). By 10.5DG (35–39 somites), the first and second PAAs had been transformed into other arteries, and the third, fourth and sixth PAAs had developed well, though the PAA system still exhibited bilateral symmetry. By 13DG, the right sixth PAA had disappeared, and the remaining PAAs formed an aortic‐arch system that was almost of the adult type.
Dopaminergic differentiation of the Nurr1‐expressing immortalized mesencephalic cell line CSM14.1in vitro
Authors: Haas Stefan Jean‐Pierre , Wree Andreas
Published: March 2003

The use of neural stem cells as grafts is a potential treatment for Parkinson's disease, but the potential of stem cells to differentiate into dopaminergic neurones requires investigation. The present study examined thein vitrodifferentiation of the temperature‐sensitive immortalized mesencephalic progenitor cell line CSM14.1 under defined conditions. Cells were derived from the mesencephalic region of a 14‐day‐old rat embryo, retrovirally immortalized with the Large T antigen and cultured at 33 °C in DMEM containing 10% fetal calf serum (FCS). For differentiation, the temperature was elevated at 39 °C and FCS was reduced (1%). Using histology, immunocytochemical detection of the stem cell marker Nestin and the neuronal marker MAP5 and, in addition, Western blotting to determine the presence of neurone‐specific enolase and the neurone nuclei antigen we demonstrated a differentiation of these cells into neuronal cells accompanied by a decrease in Nestin production. In Western blots, we detected the orphan nuclear receptor Nurr1 in these cells. This was followed by a time‐dependent up‐regulation of the enzymes tyrosine hydroxylase and aldehyde dehydrogenase 2 characteristic of mature dopaminergic neurones. Ourin vitromodel of dopaminergic cell differentiation corroborates recentin vivoobservations in the developing rodent brain.
Structure, function and evolution of the gas exchangers: comparative perspectives
Authors: Maina J. N.
Published: March 2003

Over the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ‘necessity is the mother of invention’, gas exchangers have been inaugurated through stiff cost–benefit analyses that have evoked transaction of trade‐offs and compromises. Cogent structural–functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better‐refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones of the modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices – water or air – within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animals have adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water–air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter‐current, cross‐current, uniform pool and infinite pool designs have variably developed.
Coracoclavicular joint: osteologic study of 1020 human clavicles
Authors: Gumina S. , Salvatore M. , De Santis P. , Orsina L. , Postacchini F.
Published: March 2003

We examined 1020 dry clavicles from cadavers of Italian origin to determine the prevalence of the coracoclavicular joint (ccj), a diarthrotic synovial joint occasionally present between the conoid tubercle of the clavicle and the superior surface of the horizontal part of the coracoid process. Five hundred and nine clavicles from individuals of different ages were submitted to X‐ray examination. Using radiography, we measured the entire length and the index of sinuosity of the anterior lateral curve, on which the distance between the conoid tubercle and the coracoid process depends. We also used radiography to record the differences in prevalence of arthritis in two neighbouring joints, the acromioclavicular and sternoclavicular joints. Of the 1020 clavicles, eight (0.8%) displayed the articular facet of the ccj. No statistical correlation was found between clavicular length and the index of sinuosity of the anterior lateral curve. The prevalence of arthritis in clavicles with ccj was higher than that revealed in clavicles without ccj. The prevalence of ccj in the studied clavicles is lower than that observed in Asian cohorts. Furthermore, ccj is not conditioned by either length or sinuosity of the anterior lateral curve of the clavicle. Finally, the assumption that ccj is a predisposing factor for degenerative changes of neighbouring joints is statistically justified.
Mouse models for human hair loss disorders
Authors: Porter Rebecca M.
Published: March 2003

The outer surface of the hand, limb and body is covered by the epidermis, which is elaborated into a number of specialized appendages, evolved not only to protect and reinforce the skin but also for social signalling. The most prominent of these appendages is the hair follicle. Hair follicles are remarkable because of their prolific growth characteristics and their complexity of differentiation. After initial embryonic morphogenesis, the hair follicle undergoes repeated cycles of regression and regeneration throughout the lifetime of the organism. Studies of mouse mutants with hair loss phenotypes have suggested that the mechanisms controlling the hair cycle probably involve many of the major signalling molecules used elsewhere in development, although the complete pathway of hair follicle growth control is not yet understood. Mouse studies have also led to the discovery of genes underlying several human disorders. Future studies of mouse hair‐loss mutants are likely to benefit the understanding of human hair loss as well as increasing our knowledge of mechanisms controlling morphogenesis and tumorigenesis.
High‐resolution imaging of normal anatomy, and neural and adrenal malformations in mouse embryos using magnetic resonance microscopy
Authors: Schneider Jürgen E. , Bamforth Simon D. , Farthing Cassandra R. , Clarke Kieran , Neubauer Stefan , Bhattacharya Shoumo
Published: March 2003

An efficient investigation of the effects of genetic or environmental manipulation on mouse development relies on the rapid and accurate screening of a substantial number of embryos for congenital malformations. Here we demonstrate that it is possible to examine normal organ development and identify malformations in mouse embryos by magnetic resonance microscopy in a substantially shorter time than by conventional histology. We imaged embryos in overnight runs of under 9 h, with an operator time of less than 1 h. In normal embryos we visualized the brain, spinal cord, ganglia, eyes, inner ear, pituitary, thyroid, thymus, trachea, bronchi, lungs, heart, kidneys, gonads, adrenals, oesophagus, stomach, intestines, spleen, liver and pancreas. Examination of the brain in embryos lacking the transcriptional coactivator Cited2 showed cerebellar and midbrain roof agenesis, in addition to exencephaly. In these embryos we were also able to detect agenesis of the adrenal gland. We confirmed all malformations by histological sectioning. Thus magnetic resonance microscopy can be used to rapidly identify developmental and organ malformations in mutant mouse embryos generated by transgenic techniques, in high‐throughput mutagenesis screens, or in screens to identify teratogenic compounds and environmental factors contributing to developmental malformations.
Variation in endophytic fungi from roots and leaves of Lepanthes (Orchidaceae)
Authors: BAYMAN PAUL , LEBRÓN LIGIA L. , TREMBLAY RAYMOND L. , LODGE D. JEAN
Published: March 2003

Little is known about non‐mycorrhizal endophytic fungi in tropical orchids; still less is known about how endophytes vary within and between individual orchid plants. Fungal endophytes were isolated from roots and leaves of epiphytic and lithophytic orchids in the genus Lepanthes; seven species, from rainforests in Puerto Rico, were sampled. The endophytes observed most frequently were Xylaria species and Rhizoctonia‐like fungi, found in 29% of roots and 19% of leaves, and 45 % of roots and 31 % of leaves, respectively. Five deuteromycete genera were also isolated, occurring in 19 % of roots and 43 % of leaves (combined). At least nine species of Xylaria were found, with several species sometimes occurring in a single plant. Differences between roots and leaves in frequency of Xylaria and Rhizoctonia isolates were not significant, although differences among orchid species in number and types of endophytes were. Heterogeneity of endophytes in single plants and plant organs was greater than differences between species. Many Lepanthes species are very restricted in distribution, and knowledge of their interactions with endophytes might be useful in species management.
Regulation of thiophene biosynthesis by sulphate in roots of marigolds
Authors: ARROO R. R. J. , JACOBS J. J. M. R. , VAN GESTEL J. A. M. , KENKEL H. , JANNINK W. , CROES A. F. , WULLEMS G. J.
Published: March 2003

The incorporation of [35S] sulphur in thiophenes by Tagetes patula roots was used as a model to study the regulation of secondary metabolism with a limited supply of substrate. Growth and thiophene accumulation were measured in root cultures incubated at various sulphate concentrations in the medium. A 20‐fold to 40‐fold reduction in the sulphate concentration did not affect elongation growth, branching and biomass production within 14 d but decreased the thiophene level to 25–50% of the control in the same period. The reduction in thiophene content was found to result from a decline in biosynthetic capacity of 80–95% after 8 d. This capacity was restored when roots were transferred to standard medium. The restoration took more than 24 h and was suppressed by cordycepin, an inhibitor of mRNA processing. It is concluded that the rate of thiophene synthesis is regulated by a control mechanism that reacts to the availability of sulphate to the roots.
Polyamine synthesis and accumulation in the hypersensitive response to TMV in Nicotiana tabacum
Authors: TORRIGIANI PATRIZIA , RABITI ANNA LAURA , BORTOLOTTI CRISTINA , BETTI LUCIETTA , MARANI FRANCESCA , CANOVA ANTONIO , BAGNI NELLO
Published: March 2003

summary

The possible involvement of polyamines in the tobacco mosaic virus (TMV)‐induced hypersensitive reaction (HR) in Nicotiana tabacum (L.) cv. Samsun NN, which bears the N resistance gene, was investigated. Concentrations of free and conjugated polyamines, as well as the activities of their biosynthetic enzymes ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), were analysed in the necrotic area (I, internal zone) and in the two concentric zones surrounding it (M, middle zone; E, external zone) during the progression of the HR (1, 3 and 5 d from TMV inoculation). Results were compared with those obtained in control plants (mock‐inoculated) and with the pattern in susceptible TMV‐infected tobacco plants.

In the HR, concentration increased towards zone I for free putrescine and spermidine. Highest concentrations in zones M and I occurred on day 3. Conjugated polyamines similarly showed an increasing concentration gradient towards zone I, with maximum accumulation on day 5. ODC and ADC activities also showed an increasing gradient towards zone I that could be related to the increase in free and conjugated polyamines. By contrast, in control plants concentrations of free and conjugated polyamines decreased from day 1 to day 5, ODC activity increased slightly, whereas ADC activity did not show significant changes. In the TMV‐infected susceptible tobacco plants, polyamines tended to remain in the free state instead of being conjugated as infection progressed. These results suggest that polyamines could play a role in mechanisms of resistance to biotic stress.
Components of relative growth rate and their interrelations in 59 temperate plant species
Authors: HUNT RODERICK , CORNELISSEN J. H. C.
Published: March 2003

summary

Three groups of species (21 herbaceous monocotyledons, 22 herbaceous dicotyledons and 16 woody dicotyledons), including representatives of a wide range of natural habitats and life forms in inland Britain, were grown in the seedling phase in a resource‐rich controlled environment and assessed over a 14‐day period (21 d in the case of woody species). Mean values of relative growth rate (RGR), unit leaf rate (ULR), leaf area ratio (LAR), leaf weight fraction (LWF), specific leaf area (SLA), and the root‐shoot allometric coefficient were derived.

In herbaceous species, the grand mean RGR was 0.20 d−1 comparable to values previously recorded. For woody species, the mean was 0.09 d−1. An existing assumption linking high RGR to high allocation to photosynthetic biomass was upheld by comparisons made between groups. Within groups, however, no pattern of this kind could be demonstrated.

When photosynthetically active radiation was increased from 125 to 250 μmol m−2 s−1, ULR was increased almost pro rata. The parallel response in RGR was only slight, being offset by considerable reductions in LAR. The apparent mean quantum yield for photosynthesis in herbaceous species (whole‐plant d. wt basis) was 0–60 g mol−1.

There was no significant dependence of RGR on ULR in any of the three groups of species, although the absolute magnitude of ULR declined in the order: herbaceous monocotyledons > herbaceous dicotyledons > woody dicotyledons. In all three groups, RGR was strongly dependent upon LAR but no differences emerged in absolute scale of LAR. The absolute scale of mean LWF decreased from herbaceous to woody species, but the dependence of LAR on LWF strengthened. Groups showed no systematic differences in magnitude of SLA, but the correlation of LAR with SLA was strong throughout.

Multiple regression showed that the leading determinants of RGR were ULR and SLA in herbaceous species and LWF in woody species. Principal components analyses (PCA) on each of the three groups explained at least 77% of variation and agreed closely with an optimal (non‐hierarchical) classification. Only six cluster ‘types’ were recognized out of the 16 theoretically possible combinations of ‘high’ or ‘low’ values of the four growth parameters. Strong evidence of evolutionary trade‐offs emerged, most strikingly in that high RGR was never seen in combination with low SLA. The morphological/physiological types identified by an all‐groups PCA separated woody from the herbaceous species, but dicotyledons were almost congruent with the monocotyledons.

The non‐growth‐analytical attributes most strongly correlated with mean RGR were percentage yield at a low level of mineral nutrients, leaf nitrogen concentration, and seed weight. It was concluded that mean RGR plays a central role in the identification of pathways of evolutionary specialization in herbaceous species.
Soil Mg and Ni as causal factors of plant occurrence and distribution at the Meikle Kilrannoch ultramafic site in Scotland
Authors: NAGY L. , PROCTOR J.
Published: March 2003

summary

Solution culture experiments were made using two subspecies of Cerastium fontanum and Cochlearia pyrenaica ssp. alpina (Bab.) Dalby and Festuca rubra L.of ultramafic and non‐ultramafic origin to test: (1) whether Mg and Ni toxicities are likely to exclude non‐ultramafic races of the three species; (2) whether tolerance to Mg and Ni toxicities by the ultramafic plants differed markedly among the species; and (3) to use (2) to generate a hypothesis about controlling factors of species distribution on the Meikle Kilrannoch (MK1) ultramafics. The solution cultures were based on soil solution extracts with experimentally varied concentrations of Mg, Ni and Na. The solution with high (7.5 HIM) Mg and high (0.7 mg l−1) Ni concentrations simulated the ultramafic soil solution. Care was taken to use a Fe source which did not react with Ni and microelements. Of the non‐ultramafic plants, the growth of Cerastium was reduced by high concentrations of Mg but not by Ni, whereas both the Cochlearia and the Festuca suffered severe reduction in biomass production in the presence of high Mg or Ni or both. Of the ultramafic plants, Festuca was tolerant of high Mg and Ni concentrations; Cerastium was less tolerant of high Mg; and Cochlearia had low shoot production in high Ni (although the effect was ameliorated by high Mg). The different interspecific responses of the ultramafic plants to Mg and Ni supported field observations that the three species might occupy microhabitats which differ in Mg and Ni.
Effects of elevated atmospheric CO2and soil water availability on root biomass, root length, and N, P and K uptake by wheat
Authors: VAN VUUREN MARGRET M. I. , ROBINSON DAVID , FITTER ALASTAIR H. , CHASALOW SCOTT D. , WILLIAMSON LISA , RAVEN JOHN A.
Published: March 2003

summary

We investigated interactions between the effects of elevated atmospheric carbon dioxide concentrations ([CO2]) and soil water availability on root biomass, root length and nutrient uptake by spring wheat (Triticum aestivumcv. Tonic). We grew plants at 350 and 700 μmol mol−1CO2and with frequent and infrequent watering (‘wet’ and ‘dry’ treatments, respectively). Water use per plant was 1.25 times greater at 350 than at 700 μmol CO2mol−1, and 1.4 times greater in the ‘wet’ than in the ‘dry’ treatment. Root biomass increased with [CO2] and with watering frequency. Elevated [CO2] changed the vertical distribution of the roots, with a greater stimulation of root growth in the top layers of the soil. These data were confirmed by the video data of root lengths in the ‘dry’ treatment, which showed a delayed root development at depth under elevated [CO2]. The apparent amount of N mineralized appeared to be equal for all treatments. Nutrient uptake was affected by [CO2] and by watering frequency, and there were interactions between these treatments. These interactions were different for N, K and P, which appeared to be related to differences in nutrient availability and mobility in the soil. Moreover, these interactions changed with time as the root system became larger with [CO2] and with watering frequency, and as fluctuations in soil moisture contents increased. Elevated [CO2] affected nutrient uptake in contrasting ways. Potassium uptake appeared to be reduced by the smaller mass flow of water reaching the root surface. However, this might be countered with time by the greater root biomass at elevated [CO2], by the greater soil moisture contents at elevated [CO2], enabling faster diffusion, or both. Phosphorus uptake appeared to be increased by the greater root biomass at elevated [COJ. We conclude that plant nutrient uptake at elevated [CO2] is affected by interactions with water availability, though differences between nutrients preclude generalizations of the response.
Numerical integration of phytoplankton photosynthesis through time and depth in a water column
Authors: WALSBY ANTHONY E.
Published: March 2003

The daily integral of photosynthesis for a population of planktonic cyanobacteria in the Baltic Sea is calculated by numerical analysis based on the photosynthesis‐irradiance curve of the organism, the vertical distribution of the population and details of the underwater light field. Variations in the light field are calculated from continuous recordings of surface irradiance and measurements of vertical light attenuation, with corrections for losses by reflection at the water surface that depend on the sun's elevation and roughening by wind. Integrals calculated using models in which simplifying assumptions are made about the surface irradiance overestimate the calculated value by 21% on a cloudless day and by 75%, or more, on an overcast day. Even larger discrepancies (> 100%) result when the population, which is concentrated in near‐surface layers, is assumed to be evenly distributed with depth. Errors of up to 5% result from neglect of surface reflection, and up to 12% from neglect of changes in phytoplankton distribution over 24 h. Details are given of the method of numerical analysis, using standard computer spreadsheets. Versions of the spreadsheet are described in which effects of changes in the vertical distribution of the phytoplankton and light attenuation can be calculated and the effects of water temperature and photoinhibition can be modelled. The method will improve estimates of primary productivity in natural waters. It can also be used for calculating values of the euphotic depth integrated over 24 h. The spreadsheets are available on http://www.bio.bris.ac.uk/research/walsby/integral.htm.
Appressorium formation by AM fungi on isolated cell walls of carrot roots
Authors: NAGAHASHI G. , DOUDS D. D.
Published: March 2003

Cell walls were isolated and purified from Ri T‐DNA‐transformed carrot roots to determine whether arbuscular mycorrhizal (AM) fungi need a signal from the host root in order to form appressoria. Large cell‐wall pieces were generated by the Parr nitrogen bomb technique. Purified cell walls were sterilized and inoculated with single spores of Gigaspora gigantea (Nicol. & Gerd.) Gerdemann & Trappe and Gigaspora margarita Becker & Hall using an in vitro culture technique. Appressoria only formed on epidermal cell walls isolated from host roots (Daucus carota L.) but did not form on epidermal cell walls isolated from non‐host roots (Beta vulgaris L.). Although appressoria formed on host‐cell walls, penetration hyphae did not fully develop. The results of this study indicate that appressorium formation by these AM fungi is a contact recognition event that does not require a signal secreted from the host root or the presence of intact host cells.
The selective advantage of buoyancy provided by gas vesicles for planktonic cyanobacteria in the Baltic Sea
Authors: WALSBY ANTHONY E. , HAYES PAUL K. , BOJE ROLF , STAL LUCAS J.
Published: March 2003

summary

Observations were made on the vertical distribution of colonies of Aphanizomenon flos‐aquae for 9 d at a drift‐station east of Bornholm Island in the Baltic Sea. The buoyant colonies were dispersed in the upper layers of the water column during periods of wind‐induced mixing but floated up during calm periods. From measurements of the vertical light extinction, surface irradiance and the photosynthesis versus irradiance curve, calculations were made of the changes in the daily integral of photosynthesis with respect to time and depth throughout the water column. From these calculations it is demonstrated that net photosynthesis by the population of Aphanizomenon flos‐aquae increased nearly threefold by floating up after a deep mixing event. It is estimated that, averaged over alternating periods of calm and mixing, the buoyancy provided by gas vesicles in this organism will result in a nearly twofold increase in photosynthesis. A quantitative analysis has been made of the relationship of the daily integral of photosynthesis by the Aphanizomenon population with the mean depth of the population in the water column and the daily insolation. The analysis shows that the integral decreases linearly with respect to mean depth.
Physiological changes on agricultural crops induced by different ambient ozone exposure regimes
Authors: MEYER U. , KÖLLNER B. , WILLENBRINK J. , KRAUSE G. H. M.
Published: March 2003

Spring wheat (Triticum aeslivum cv. Nandu) cultivated under glasshouse conditions was exposed to ozone in large fumigation chambers for 2 wk. Different exposure regimes were applied as constant concentrations as well as with ozone peaks, partly under equal dose‐conditions, in times of high solar radiation during different stages of development (seedling, late tillering, anthesis). Chlorophyll fluorescence was monitored and amounts of carbohydrates (hexoses, sucrose, starch) and chlorophyll were measured in young leaves (seedling) and flag leaves (late tillering, anthesis) during and after ozone exposure. Although seedlings showed no significant response in photosynthesis, strong effects on photosynthesis and carbohydrate accumulation were measured when plants were fumigated during anthesis, especially after a heat stress period preceding ozone treatments. Under equal dose conditions chlorophyll fluorescence parameters (Fv:Fm) and electron transport rate decreased and sucrose content of flag leaves increased significantly if ozone at a concentration of 220 μg m−3 was supplied for 4 h, indicating that peak concentrations show stronger effects than constant concentrations. The reaction of wheat plants is dependent on environmental conditions such as preceding heat stress and on the developmental stage during exposure. The results favour the hypothesis that photoinhibition and disturbance of photosynthesis are only secondary effects as a consequence of retarded sucrose export from the leaf, because of damage at the plasma membrane.
Quantitative trait loci associated with stomatal conductance, leaf rolling and heading date mapped in upland rice (Oryza sativa)
Authors: PRICE A. H. , YOUNG E. M. , TOMOS A. D.
Published: March 2003

summary

Improving the drought resistance of high yielding rice (Oryza sativa L.) varieties for upland areas is a goal of rice breeders since upland rice relies exclusively on rainfall for water and is generally low yielding. Identifying quantitative trait loci (QTLs) which confer drought resistance promises to speed this goal. We have previously described the use of 82 restriction fragment length polymorphism (RFLP) markers in the genetic mapping of root growth characteristics that are potentially involved in drought resistance in a population of 178 F2 plants derived from a cross of two drought resistant upland varieties, Azucena and Bala. Here we report the characterization and QTL mapping of three other mechanisms of drought resistance, leaf rolling, stomatal behaviour and early flowering, in this population. When the youngest fully expanded leaf was excised from 12 rice varieties,‘IR20’and‘Bala’ were identified as slow at rolling. Although ‘Azucena’ rolled its leaves much faster than ‘Bala’ upon excision, stomatal resistance rose more rapidly in‘Bala’, resulting in a lower rate of water loss. By assessing leaf rolling and stomatal resistance in the F2 population, it was possible to identify QTLs for these traits. A QTL for slow leaf rolling from ‘Bala’ was found on chromosome 1. Two QTLs associated with resting stomatal conductance were found on chromosomes 3 and 12. QTLs for the rate of stomatal closure were found on chromosomes 3 and 7. In addition, it was possible to map QTLs associated with the days to heading which were found on chromosomes 3, 8 and 10. These results identify markers of potential value to breeders and are discussed in the context of previously reported data for heading date QTLs in rice and for stomatal conductance QTLs in maize.
Toxic interactions of metal ions (Cd2+, Pb2+, Zn2+ and Sb3−) on in vitro biomass production of ectomycorrhizal fungi
Authors: HARTLEY JEANETTE , CAIRNEY JOHN W. G. , SANDERS FRANCIS E. , MEHARG ANDREW A.
Published: March 2003

summary

A number of ectomycorrhizal (ECM) fungi, from sites uncontaminated by toxic metals, were investigated to determine their sensitivity to Cd2+, Pb+2, Zn2+ and Sb3−, measured as an inhibition of fungal biomass production, Isolates were grown in liquid media amended with the metals, Individually (over a range of concentrations) and in combination (at single concentrations) to determine any significant interactions between the metals. Significant interspecific variation in sensitivity to Cd2+ and Zn2+ was recorded, while Pb2+ and Sb3− individually had little effect. The presence of Pb2+ and Sb3− in the media did however, amcliorate Cd2+ and Zn2+ toxicity in some circumstances. Interactions between Cd+2 and Zn+2 were investigated further over a range of concentrations. Zn2+ was found to significantly ameliorate the toxicity of Cd2+ to three of the four isolates tested. The influence of Zn2+varied between ECM species and with the concentrations of metals tested.
Initial stages of lichen hydration observed by proton magnetic relaxation
Authors: HARAŃCZYK H. , GAŹDZIŃSKI S. , OLECH M.
Published: March 2003

The hydration of selected lichens (Cladonia mitis, Cladonia bellidiflora, Cetraria islandica, Parmelia saxatilis, and Xanthoria parietina) was investigated using gravimetry and proton magnetic free induction decays (FIDs).

The hydration from gaseous phase and dehydration to gaseous phase showed first‐order kinetics. The amount of water which was non‐removable in the air‐dry state (relative humidity p/p0=9%) did not depend significantly on the lichen species and was found to be 5·6±1·0% of the d. wt.

The proton FID Gaussian component from the solid matrix of thallus structure, and two (or, depending on lichen species, one averaged) liquid signals coming from water tightly bound on the surface of thallus solid matrix and from loosely bound or free water, were recorded. The bound‐water component was distinguished by its motional properties and by its proximity to endogenous paramagnetic centres present in solid matrix (presumably PS II reaction centres of the photobiont). Mild dehydration (from gaseous phase) could completely remove the loosely bound water fraction, leaving the system below the water percolation threshold and below the water clustering point, emphasizing the passivity of lichen response to desiccation shock. In the species in which the one average liquid component was recorded, bound water behaved similarly.

The hydration at which free water pool vanishes (ΔM/m0) and the relative (scaled to water) proton densities of solid matrix of lichen (β) were evaluated for all lichens investigated.
Delineation of the European Armillaria species based on the sequences of the internal transcribed spacer (ITS) of ribosomal DNA
Authors: CHILLALI MOHAMMED , WIPF DANIEL , GUILLAUMIN JEAN‐JACQUES , MOHAMMED CAROLINE , BOTTON BERNARD
Published: March 2003

Variation within the internal transcribed spacer (ITS) of the ribosomal RNA gene of 15 isolates representing seven European Armillaria species, was examined by sequencing of the PCR‐amplified products. The analysis of an 744‐bp region showed that the 5.8S gene appeared to be highly conserved in the 15 isolates and in other Basidiomycetes and Ascomycetes, whereas ITS1 and especially ITS2 spacers exhibited polymorphisms due to base substitutions, insertions or deletions of up to eight nucleotides. An initial dendrogram for the full sequence was drawn using cluster analysis (UPGMA), and a tree was constructed using the maximum parsimony method. Both methods indicated that the isolates could be divided into four major groups. One group, consisting of A. ectypa, was distinct from all the other species. Examination of the other groups indicated that A. tabescens and A. mellea were in a separated cluster, with a significant variation between the two isolates of the latter species. A. gallica and A. cepistipes constituted another closely related group distinguishable from A. ostoyae and A. borealis, these latter two species exhibiting the highest similarity. The results are consistent with, and discussed in regard to, the relationships estimated previously by pairing tests, morphological and physiological comparisons, as well as by restriction fragment length polymorphism of the rDNA.
Activities of oxidoreductase enzymes in tissue extracts and sterile root exudates of three crop plants, and some properties of the peroxidase component
Authors: GRAMSS G. , RUDESCHKO OLGA
Published: March 2003

Aqueous extracts of homogenized shoot and root tissue of alfalfa (Medicago sativa L.), white mustard (Sinapis alba L.), and cress (Lepidium sativum L.), with the exudates of sterile roots of these crop plants, were examined spectrophotometrically for the activities of 20 oxidoreductase enzymes by standard procedures. In tissue extracts and root exudates, the reactions of laccase (EC 1.10.3.2), ascorbate oxidase (EC 1.10.3.3), monophenol monooxygenase (EC 1.14.18.1), and phenol 2‐monooxygenase (EC 1.14.13.7) were readily detected. Of the aromatic‐ring cleavage dioxygenases, those of the meta‐cleavage pathway (EC 1.13.11.2 and 1.13.11.8) could also be detected. Guaiacol peroxidase (EC 1.11.1.7) was dominant in all samples. In sterile root exudates of alfalfa, this enzyme was represented by at least seven acidic isoforms. The formation of the ligninolytic Mn3+/malonate and Mn3+/citrate complexes from Mn2+ occurred in all tissue extracts and in root exudates of alfalfa. In root extracts of soybean (Glycinemax L.), the rate of Mn3+ generation correlated (P=0·993) with the activities of endogenous plant guaiacol peroxidase and horseradish peroxidase (HRP) supplements and also with the total phenol content in tissue extracts (P=0·984). Plant guaiacol peroxidase and purified HRP decolorized four aromatic dyes, an activity reported to be involved in ligninolysis. Although no enzymes capable of generating H2O2 as a consequence of the oxidation of simple sugars, amino acids, organic acids, and aldehydes were found, traces of peroxide were detected in tissue extracts and in the root exudate of alfalfa. It is concluded that the oxidoreductases found in plant tissues also occur in root exudates of aseptic whole plants. The significance of interrelations between oxidoreductase enzymes and enzymically generated higher‐valency metal ions is discussed in the context of the oxidative conversion of phenolic compounds in soil and plant tissue.
Photosynthetic responses to CO2 concentration and photon fluence rates in the CAM‐cycling plant Delosperma tradescantioides (Mesembryanthemaceae)
Authors: HERPPICH W. B. , HERPPICH M. , TÜFFERS A. , Von WILLERT D. J. , MIDGLEY G. F. , VESTE M.
Published: March 2003

Responses of gas exchange and photosynthesis to changes in CO2 concentration and PPFD were examined in well watered plants of Delosperma tradescantioides Bgr. to establish the relative importance of these environmental changes on the photosynthetic machinery in this CAM‐cycling species which grows naturally in both exposed and partly shaded environments. Plants were grown at two PPFDs (220 [LL] and 550 [HL]μmol m−2 s−1). HL plants had larger leaves with higher specific weight, water content and diurnal malic acid fluctuation. Photosynthetic PPFD responses were typically those of sun and shade species for HL and LL plants, both under 21% O2 and non‐photorespiratory (2% O2) conditions. The CO2 compensation point in the absence of non‐photorespirational CO2 evolution in the light (Γ∗) was c. 30 μmol mol−1. Irradiation reduced mitochondrial respiration by >50%. Comparison of the PPFD responses of linear electron flow rates derived from gas exchange measurements and from fluorescence analysis (𝒥F) indicated effective photosynthetic control. 𝒥F was always larger than electron flow rates calculated from gas exchange, indicating that processes other than carboxylation and oxygenation were consistently important in energy consumption under all sampled environmental conditions. Regardless of PPFD during growth, electron flow to carboxylation and 𝒥F were linearly correlated, demonstrating that the photosynthetic apparatus was well adapted to PPFD during growth. In HL plants, non‐photochemical quenching increased, and photochemical quenching and the quantum yield of linear electron transport through PS II decreased more slowly with increasing PPFD than in LL plants. In plants of both treatments non‐photochemical energy dissipation seemed to be exhausted when the proportion of photons not utilizable by photochemistry exceeded 0·7. Results illustrate a pronounced ability of D. tradescantioides to acclimate to a 100% change in the prevailing PPFD and lend support to the hypothesis that CAM cycling might act as a photoprotective process.