bluuebunny/crossref_metadata_2025_split huggingface dataset:
Responses of rust (Puccinia lagenophorae Cooke) to nutrient supply in groundsel (Senecio vulgaris L.) and effects of infection on host nutrient relations
Authors: PAUL N. D. , LAXMI K. ARUNA , AYRES P. G. 
Published: April 2006

summary Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a nutrient‐poor sand‐soil mixture amended with a compound fertiliser to provide a range of nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by pustules was unaffected by nutrient supply. Since total leaf area increased with increasing nutrient supply, the percentage of total area that was infected declined. Plant and root dry weights increased with nutrient supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by nutrient supply, but reduced leaf area only under the most nutrient‐rich conditions.The ratios of root length: leaf area (R:L) and, especially, root:shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight.Conversely, increasing nutrient supply decreased root length:weight only on the basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt:f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3‐fold over those in controls and that of N was also substantially increased. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt:f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced.Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased ‘shoot demand’ on each unit of root which, in turn, reflected the decreased R:S and R:L of infected plants.
Ultrastructural and histochemical studies on interactions between Vitis vinifera L. and Uncinula necator (Schw.) Burr.
Authors: HEINTZ C. , BLAICH R. 
Published: April 2006

summaryHost‐parasite interactions between the grapevine Vitis vinifera L. and the powdery mildew Uncinula necator (Schw.) Burr, were studied by light microscopy and histochemistry, scanning and transmission EM. The lobed appressoria (10 μm diam) of the fungus adhered to the host cuticle because of their shape and the production of a soluble adhesive substance. Each formed a penetration peg (0–3 μm diam) which, after penetration into the epidermal cell, developed into a globular haustorium consisting of a nucleated central body with fingerlike lobes, embedded in a matrix. The surrounding extra haustorial membrane was derived from the transformed plasmalemma of the host cell. As a defence mechanism the walls of the host cell and neighbouring cells were encrusted with silica and phenolic substances associated with cell wall bound peroxidase activity. Penetration may have been blocked by the formation of a papilla composed of different layers containing carbohydrates, silica and phenolic substances. Cells forming a thick papilla were not infected. In cells with old infections, callose deposits could be observed in walls and/or around the haustorial neck and papilla, and sometimes around the whole haustorium.
Effect of VA mycorrhizal fungi and rhizosphere microorganisms on root and shoot morphology, growth and water relations in maize
Authors: KOTHARI S. K. , MARSCHNER H. , GEORGE E. 
Published: April 2006

summaryMaize (Zea mays L.) was grown in fertilized calcareous soil in pots which were separated by 30 μm nylon nets into three compartments, the central one for root growth and the two outer ones for hyphal growth. The size of each compartment was 40 × 25 × 3 cm. The treatments comprised of sterilized soil, either inoculated with rhizosphere microorganisms (other than VA mycorrhizal fungi), with rhizosphere microorganisms together with a VA mycorrhizal fungus [Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe] or remained non‐inoculated (sterile control). As inoculum for rhizosphere microorganisms the roots with adhering rhizosphere soil of non‐mycorrhizal maize plants was used.Compared to the non‐inoculated (sterile) control, inoculation with rhizosphere microorganisms did not affect shoot dry weight and morphology, but increased total root length (17 %) and root length per unit root dry weight (35%). The additional inoculation with VA mycorrhizal fungi had no influence on the shoot dry weight but increased area and dry weight of the leaf blades by about 30% and the ratio leaf blade:leaf sheath + stem (w/w) by 41 %. The most profound effect of VA mycorrhizal fungi inoculation was on root growth and morphology. Compared to the non‐inoculated control, root dry weight was decreased by 16%, root length by 31 % and root hair density and length by 41 and 43 %, respectively.In mycorrhizal plants the transpiration rates per plant were about 30 % higher than in the other treatments and this is attributed to the larger leaf area. Water uptake rate per unit root length and per unit time was about twice as high in mycorrhizal plants. For several reasons a substantial hyphal water transport seems unlikely. The results stress the necessity of detailed studies on root morphology for interpretation of effects of mycorrhizal fungi on mineral nutrient uptake and water relations in plants.
A laboratory scale air‐lift helical photobioreactor to increase biomass output rate of photosynthetic algal cultures
Authors: LEE EDMUND T.‐Y. , BAZIN MICHAEL J. 
Published: April 2006

summaryThe helical air‐lift reactor of 0·315 1 capacity provides an improved way to cultivate photosynthetic organisms when compared to a 0·625 1 stirred reactor. The improvement results from an approximately three‐fold increase in the surface area: volume ratio of the reactor. Continuous operation of the helical reactor at a dilution rate of 0·025 h−1 permitted a light‐limited photosynthetic culture of Porphyridium cruentum to be maintained at a steady state biomass concentration of 4·6 g l−1 compared to 1·7 g l−1 in the stirred reactor under similar illumination. When operated at an air flow rate of 0·75 1 min−1, the volumetric oxygen transfer coefficient was 160 h−1 in the helical reactor and a Reynolds number of 2000 was obtained.
Effects of liming on ectomycorrhizal fungi infecting Pinus sylvestris L.
Authors: ERLAND SUSANNE , SÖERSTRÖM BENGT 
Published: April 2006

summaryFive ectomycorrhizal fungi were studied in relation to the effects of applications of lime and wood ash to the growth substrate. Growth and survival of inoculated fungi in unsterile humus and relative root colonization frequency by inoculated and indigenous ectomycorrhizal fungi were measured. Growth of the fungi was tested in Petri dish systems with humus taken from a field site treated with lime and wood ash. The infection potential of the fungi was tested by introducing Pinus sylvestris L. seedlings into the growth systems. Paxillus involutus (Fr.) Fr. was the only fungus affected both by the pH increase, and by the different treatments applied, in all aspects of its ecology tested (growth and survival in humus, infection potential and competitive ability). No other fungus grew saprophytically, but they showed the similar changes in infection potential in response to pH whether lime or ash had been used.
The influence of open‐top chambers on the growth and development of field bean
Authors: SANDERS G. E. , CLARK A. G. , COLLS J. J. 
Published: April 2006

summaryIn 1988, open‐top chambers (OTCs) based on the Raleigh (USA) design were used to investigate the effect of ambient pollutants on field‐sown Vicia faba cv, Ticol. This paper reports an aspect of this study in which the effect of the chamber itself on crop growth and development was investigated. Non‐filtered chamber (NF OTC) microclimates were typically 0.8°C warmer, with 20% less radiation and reduced wind speeds compared with open‐field sub‐plots (AA treatments). These differences are sufficient to induce alterations in the growth and development of V. faba.Plant development progressed more quickly inside the chambers in response to the faster accumulation of thermal time. Chamber‐grown V. faba were up to 20 cm taller and had fewer branches (0.7 compared with 1.2 per plant) than plants grown in the AA treatments. Larger leaf areas developed on the NF plants, and there were fewer stomata per unit leaf area in this treatment (34 compared with 42 mm−2, P= 0.01). Enclosure within an OTC did not alter the number of flowers per plant or the number of flowers which formed pods. However, at harvest, chamber‐grown plants had a 13% higher yield than the plants grown in open‐field plots. These differences in growth are described in relation to the microclimate differences between AA and NF treatments.
The vegetational history of Glen Diomhan, North Arran, site of endemic whitebeams, Sorbus arranensis Hedl. and S. pseudofennica E.F. Warb.
Authors: STEVEN G. , DICKSON J. H. 
Published: April 2006

summaryA detailed pollen analysis was undertaken of sediment from a site in Glen Catacol on the Isle of Arran, Scotland, close to Glen Diomhan National Nature Reserve which has a large though possibly declining population of the endemic whitebeams, Sorbus arranensis Hedl. and S. pseudofennica E.F. Warb. Blanket peat formation began before 7000 years BP. The results provide evidence that while parts of the glen saw the development and subsequent decline of birch, oak, hazel and alder woodland a large proportion of the surrounding vegetation has remained open throughout the Flandrian with grass‐heath similar to that which occurs over much of the glen in the present day.
The xylem wedge as a functional unit – speculations on the consequences of flow in leaky tubes
Authors: CANNY M. J. 
Published: April 2006

summaryXylem, as a mixture of elements of large and small diameter, presents a paradox when viewed as a conductor of sap flow, since the quantity carried is determined by only the largest diameter elements. The paradox may be s resolved, and an important function for the smallest elements revealed, by consideration of flow in leaky tubes. It is shown how the balance between axial flow and leakage becomes critical at a certain diameter, called the critical diameter (D0). Below D0, no axial flow can occur. When a stack of connected tracheary elements of different diameters is assembled into a xylem wedge, as in the major veins of dicotyledon leaves, this wedge will act as a functional unit. Elements with D > D0 have axial flow, but those where DD0 have only radial flow. The mixture of elements then acts to concentrate solutes of the sap in the smallest elements at the apex of the wedge, left behind as the water leaves. The balance between radial and axial flow is also self‐adjusting to changes in the longitudinal gradient of pressure. Consideration is given to the functions of these graded stacks in the metaxylem of leaves, of stem vascular bundles, within secondary wood, and in roots. It is shown how some xylem fibres may be expected to mediate exchanges of water and solutes, and may act as regulators of these exchanges in space and time. Some experimental demonstrations are presented of the predictions of this hypothesis.
Architectural analysis of plant root systems 1. Architectural correlates of exploitation efficiency
Authors: FITTER A. H. , STICKLAND T. R. , HARVEY M. L. , WILSON G. W. 
Published: April 2006

summaryIn order to determine whether variation in root system architecture can be said to be adaptive, it is necessary' to be able to define the costs and benefits of particular architectures. A simulation model of root growth is described that allows the development of root systems varying in several important architectural features, including topology, link lengths and radii, and branching angles. The program also estimates the exploitation efficiency of each root system, as the ratio of the volume of soil occupied by depletion zones (allowing for overlaps between competing roots) and the volume of tissue required to construct the system. Output from the model shows that high exploitation efficiency is associated with a herringbone topology (where branching is predominantly on the main axis) and with long interior and exterior links, although all these characteristics are associated with large tissue volumes and hence high construction cost, We predict, therefore, that such ‘expensive’ root systems will occur mainly in nutrient‐poor soils and on plants characteristic of such soils.
Biophysics of leaf growth of hybrid poplar: impact of ozone
Authors: FROST D. L. , TAYLOR GAIL , DAVIES W. J. 
Published: April 2006

summaryBiophysical parameters controlling leaf expansion in hybrid poplar (Populus nigra L. ×P. deltoides Barer, ex Marsh =P. x euramericana) were measured for first‐year cuttings growing under controlled conditions, with or without ozone fumigation. As individual leaves expanded, leaf water potential remained constant whilst solute potential declined and turgor (P) increased from approximately 0.5 MPa to over 1.0 MPa as leaf size increased. Yield turgor (Y) measured by stress‐relaxation of leaf discs within psychrometers, increased from approximately 0.2 MPa to over 1.0 MPa during the same period. As the value of Y approached that of P, the effective turgor For growth (P – Y) declined and became zero as leaf growth ceased.Cell wall extensibility (measured as percentage plasticity by the ‘Instron’ technique) was related to leaf growth rate such that highest values of plasticity corresponded to maximum rates of growth. As growth ceased, wall extensibility declined to very law values.Fumigation with 50 nl 1−1 ozone for 16 h d−1 had no effect on any of the measured parameters with the result that growth and mature leaf size were unaffected by comparison with control plants receiving charcoal‐filtered air. Additional episodes of 120 nl 1−1 ozone on three consecutive days during the period of maximum leaf growth similarly had no effect on expansion or final leaf size.
Colonization of wheat (Triticum vulgare L.) by N2‐fixing cyanobacteria: II. An ultrastructural study
Authors: GANTAR M. , KERBY N. W. , ROWELL P. 
Published: April 2006

summaryThe infrastructure of a novel association between a N2‐feeing cyanobacterium, Nastoc sp, isolated from soil, and wheat seedlings grown in liquid culture is described. Cyanobacteria were found either as hormogonia, filaments or aseriate packages. The aseriate packages, which developed from filaments, often formed a thick layer surrounding the root surface. The packages were in intimate contact with adjacent root epidermal cells and could not be removed without damaging the epidermis. Cyanobacteria penetrated both the root epidermis and cortex and formed packages in intercellular spaces. Cyanobacteria] filaments were occasionally found within plant cells that appeared empty. Additionally, cyanobacteria were observed in association with the stem and on the surfaces of leaves. These findings demonstrate the technical feasibility of forming a novel association between a N2‐fixing cyanobacterium and a cereal.
Dimorphic epidermal cell chloroplasts in the mesophyll‐less leaves of an extreme–shade tropical fern, Teratophyllum rotundifoliatum (R. Bonap.) Holtt.: a light and electron microscope study
Authors: NASRULHAQ‐BOYCE A. , DUCKETT J. G. 
Published: April 2006

summaryThis light and electron microscope study of the iridescent blue leaves of the fern Teratophyllum rotundifoliatum, reveals several novel anatomical and cytological features. In this extreme shade species [0.4—‐(3)–4 W m−2] of lowland tropical rainforest in peninsular Malaya, the greater part of the lamina between the simple collateral vascular bundles, consists only of epidermal cells. From 4–(6.9)–12 large chloroplasts 9.4–(17.9)–27 μm in diameter are located adjacent to the inner walls of the lens‐shaped upper epidermal cells. Those in the tessellated lower epidermal cells are smaller [5.0–(7.6)–19.5 μm], much more numerous [21–(53)–83] and regularly distributed around the periphery. They are identical in size and ultrastructure to the chloroplasts in the guard cells of the stomata. Whereas the upper epidermal chloroplasts and those in the stelar tissues contain very little starch, numerous starch grains occupy up to Sl‐9% of the volume of the lower epidermal chloroplasts. As in other extreme‐shade plants the epidermal chloroplasts in T. rotundifoliatum contain numerous large grana, with no preferred orientation, and integranal lamellae completely filling the stroma. The numbers of thylakoids per granum in the lower epidermal cells [9–(29.3)–84] are significantly smaller than those in the upper [22–(86)–28O]. The latter appear to be the largest yet recorded in land plants and this probably accounts for the remarkably low chlorophyll a: b ratio (1.8) in T. rotundifoliatum. Record amounts of chlorophyll per unit leaf fresh weight and per unit leaf area in T. rotundifoliatum reflect the high proportion of leaf cells containing chloroplasts. The unusual features of leaf anatomy and cytology in T. rotundifoliatum appear to be associated with maximizing the efficiency of absorption of very low diffuse radiation.
Rapidity of cellular changes induced by zinc in a zinc tolerant and non‐tolerant cultivar of Festuca rubra L.
Authors: DAVIES M. S. , FFRANCIS D. , THOMAS J. D. 
Published: April 2006

summary7 day‐old seedlings of a Zn‐tolerant cultivar (Merlin) and a non‐tolerant cultivar (S59) of Festuca rubra L. were transferred to aerated solution culture containing 3 concentrations of Zn (0, 80 and 120 μM). Roots were sampled at 0, 6, 12, 24, 48, 72 and 96 h following transfer. Zn markedly reduced root extension in S59; this inhibition was evident after only 12 h exposure. In contrast Zn stimulated the root extension of Merlin. The length of the apical meristem of S59 was reduced within 12 h after transfer to the Zn‐containing solutions, followed by a further reduction to 69 % and 61 % of that of control roots (0 μM Zn) after 96 h at 80 μM Zn and 120 μM Zn respectively. The meristem length of Merlin was much less affected by Zn. Treatment with 80 μM Zn resulted in a stimulation in the number of lateral root primordia in both cultivars but their formation was depressed relative to the control roots at 120 μM Zn in S59, though not in Merlin. The area of mitotic cells was reduced by 25 % after only 12 h exposure to 120 μM Zn in S59 and this reduction increased with duration of exposure. However, in Merlin, the area of mitotic cells increased with increasing length of exposure to Zn. The protein content of mitotic cells of S59 was reduced by 28 %, relative to that of roots grown in the control solutions, after 12 h exposure to 120 μM. Zn, culminating in a 50 % reduction after 96 h exposure. However, the cellular protein content of Merlin increased progressively with time of exposure to Zn. The sensitivity and rapidity of response of these cellular changes to Zn in S59 may make them useful early markers of metal toxicity in roots.
Population variation in Spartina anglica C. E. Hubbard
Authors: THOMPSON J. D. , McNEILLY T. , GAY A. J. 
Published: April 2006

summaryReplicated clones from ten populations of Spartina anglica C. E. Hubbard were grown in a common garden experiment to determine whether the phenotypic variation previously observed in natural habitats was due to inherent differences between clones. For a range of morphological characters, mean differences between populations, and clonal repeatability, were very low. Different morphological forms were, however, evident from differences in character correlations. Thus, morphological variation appears to be dominated by phenotypic plasticity with a limited amount of possibly genetic differences distinguishing different morphological forms. No differences in the relative variability of morphological characters were recorded between populations sampled from successionally adjacent salt‐marsh zones, although the oldest population, from Poole Harbour, contained significantly less morphological variation than other populations. The pattern of (a) flowering during the first year of the experiment, (b) clone survival, and (c) clonal growth, showed that the vigour of clones sampled from four successionally mature populations was significantly less than that of the other populations. It is suggested that these consistent differences between populations are due to an age‐related decline in vigour of clonal material and, thus, due to somatic variation rather than to genetic differences between populations. The ecological implications of this interpretation are discussed in relation to the origin of S. anglica and the successional development and ‘die‐back’ of natural populations.
Leaf area compensation and nutrient interactions in CO2‐enriched seedlings of yellow‐poplar (Liriodendron tulipifera L.)
Authors: NORBY RICHARD J. , O'NEILL E. G. 
Published: April 2006

summaryThe responses of yellow‐poplar (Liriodendron tulipifera L.) seedlings to elevated levels of atmospheric CO2 were investigated to identify attributes governing growth and physiological responses to CO2. Based on the pattern of leaf initiation and nutrient requirements of the species, it was predicted that (1) CO2, enrichment would enhance growth of yellow‐poplar seedlings both through accelerated leaf area production and through higher rates of carbon assimilation per unit leaf area; and (2) growth enhancement of yellow‐poplar by CO2 enrichment would be reduced by nutrient limitations. The hypotheses were tested in an experiment in which yellow‐poplar plants were grown from seed for 24 weeks in controlled‐environment chambers. The experimental design comprised three atmospheric CO2 concentrations (371, 493, and 787 cm3m−3), two levels of mineral nutrients (unfertilized or weekly additions of complete nutrient solution), and three harvests (6, 12, and 24 weeks). Plant growth rate, water use, foliar gas exchange, component dry weights, and nutrient contents were measured.Both hypotheses were rejected. Whole‐plant dry weight increased similarly with CO2, enrichment in plants provided with additional mineral nutrients and in unfertilized plants, although the fertilized plants grew 10‐fold larger. The increase in dry weight resulting from elevated CO2 occurred only in root systems. Although leaves were produced continuously during the experiment, leaf area was slightly reduced in elevated CO2, and the whole‐plant growth response was wholly attributable to an increase in carbon assimilation per unit leaf area. Although the compensation between photosynthesis and leaf area reduced the potential growth response to CO2, the reduction in leaf area ratio was associated with a significant increase in water‐use efficiency. This unexpected result demonstrated the importance of feedbacks and interactions between resources in shaping the response of a plant to CO2.