bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DEVELOPMENT OF ENDOMYCORRHIZAL ROOT SYSTEMS V. THE DETAILED PATTERN OF DEVELOPMENT OF INFECTION AND THE CONTROL OF INFECTION LEVEL BY HOST IN YOUNG LEEK PLANTS
Authors: BUWALDA J. G. , STRIBLEY D. P. , TINKER P. B. 
Published: May 2006

SummaryLeek plants (Allium porrum L.) were grown on partly sterilized soil, in tall pots so that roots grew downwards unimpeded, with inoculum of the vesicular‐arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe placed either under the seedling or dispersed uniformly throughout the soil. The age of each individual root, and the distribution of infection in single roots were both determined in each of a series of sequential harvests.The development of the root systems was unaffected by placement of inoculum. Formation of adventitious roots continued up to 42 d, when branching commenced. The rate of initiation of roots was approximately exponential but more accurately fitted a logistic function. The increase with time in total length of root for the root system (Lt) was approximately exponential but the length of the single roots (Ltr) increased linearly.The total length of infection in whole root systems (Lir) also increased exponentially with time, but the rate of extension for the sum of the individual lengths of infected root (infection ‘segments’) in single roots (Ltr) was linear, with an apparent delay of approx. 5 d before infection could be observed.The rate of increase in Lir was very similar for placed (0.53 cm d1) and dispersed (0.58 cm d1) inocula, even though the number of infection segments per root differed widely. This suggests that the host controls the rate of growth of the fungus. On this basis, and assuming each root encountered a new propagule every 4 d, it was possible to predict the lengths and numbers of infection segments in single roots.The percentage infection in whole root systems and single roots, plotted against time, showed a delay, then a sharp rise to a final constant value. This pattern of development can be explained for single roots by simple arithmetical rules. Using these simple rules, and assuming that the rate of production of adventitious roots fitted either a logistic or exponential equation, it was possible to model the development of infection up to 42 d for a whole root system either algebraically or by numerical simulation.
PHOTOSYNTHETIC CAPACITY CHANGES IN PELTIGERA
Authors: BROWN D. , KERSHAW K. A. 
Published: May 2006

SummaryThe seasonal net photosynthetic response matrix to moisture, temperature and light has been examined in two populations of Peltigera rufescens (Weis) Mudd, geographically widely separated and representative of arctic and temperate climates, respectively. The arctic population shows a seasonally constant net photosynthetic rate whereas the temperate population exhibits a marked summer increase of photosynthetic capacity under high temperatures and levels of illumination. This change in capacity is shown by use of photosynthetic‐illumination curves to be due to temperature acclimation, presumably involving a seasonal enzymatic change in the Calvin cycle. Experimental induction of the summer or winter response can be achieved by storage of air‐dry thalli under an appropriate combination of ambient temperature and day length. The data are discussed both in relation to the ecology of the two contrasting populations and to seasonal changes in the photosynthetic capacity of other lichen species.
A HYPOTHESIS RELATING CRITICAL POTASSIUM CONCENTRATIONS FOR GROWTH TO THE DISTRIBUTION AND FUNCTIONS OF THIS ION IN THE PLANT CELL
Authors: LEIGH R. A. , WYN JONES R. G. 
Published: May 2006

SummaryThe growth and metabolism of plants in response to different concentrations of tissue K is discussed in relation to current knowledge about the distribution and functions of this ion in plant cells. In the cytoplasm, K has an important role in providing the correct ionic environment for metabolic processes. The ionic requirements of protein synthesis seem to be particularly important in determining the composition of the cytoplasm. Potassium is not replaceable in its cytoplasmic functions and the plant probably needs to maintain the cytoplasmic concentration of K in the range of 100 to 200 mM. Potassium salts in the vacuole are involved in the generation of turgor but when unavailable they can be replaced by other solutes. Salts of other cations such as Na and Mg are often a readily available alternative to K but in their absence organic solutes must be accumulated.With these observations as a basis, a model is proposed in which, as the concentration of K in the tissue declines, the concentration in the cytoplasm is initially maintained constant, while that in the vacuole decreases. In order to maintain turgor, alternative solutes are accumulated in the vacuole as replacements for K. It is assumed that K in the vacuole can only drop to a certain minimum level and, once this is reached, any further decline of tissue K must be at the expense of that in the cytoplasm. This leads to a decrease in the rate of metabolic processes that depend on K and so to a decline in growth. The hypothesis explains the observed relationships between growth and concentrations of K in tissues, and their modification by Na and other cations.
WHY DOES PINGUICULA VULGARIS L. TRAP INSECTS?
Authors: KARLSSON P. S. , CARLSSON B. 
Published: May 2006

SummaryGrowth and nutrient content were studied when various nutrients were fed to the carnivorous plant Pinguicula vulgaris L. through its leaves. Agar blocks containing different combinations of three nutrient solutions [N, P and micronutrients (M), i.e. all other essential nutrients] simulating insects were supplied in a factorially designed experiment. Plants not exposed to any treatment, and plants supplied with insects, were used as controls. Only P had a significant effect on plant biomass. The root/leaf ratio increased as a result of N treatment and decreased as a result of the NPM interaction. The NPM interaction also markedly affected the N and P content of the plants. No treatment had any significant effect on the concentration or total content of micronutrients in tissues.It is concluded that P is the most important nutrient gained by P. vulgaris through carnivory. The interactive effect of a complete nutrient solution is also important for nutrient relations.
DIURNAL CHANGES IN WATER RELATIONS AND ABSCISIC ACID IN FIELD‐GROWNVITIS VINIFERACULTIVARS
Authors: LOVEYS B. R. , DÜRING H. 
Published: May 2006

SummaryDiurnal changes in endogenous abscisic acid (ABA) in the leaves, together with stomatal conductance and water relations, were studied in grape vines (Vitis viniferaL. cvs Riesling and Silvaner) growing in the field in Adelaide, South Australia.There was an increase in ABA content of the leaves which commenced in the morning and reached a peak of approximately twice the pre‐dawn level at midday. Wilted excised leaves from the same vines accumulated ABA at a higher rate. The increase in attached leaves was sometimes unrelated to low leaf turgor. Import via the xylem may account for this increase during the early part of the day. Leaf conductance in Riesling was high in the early morning but fell as leaf ABA rose, and it is suggested that midday stomatal closure was due to ABA accumulation. Stomatal behaviour later in the day was more readily accounted for by environmental variables such as temperature and atmospheric vapour pressure deficit than by changes in ABA.Abscisic acid did not consistently accumulate in attached leaves in response to zero turgor, even if this condition was maintained for the greater part of the day. It is suggested that loading into the phloem and transport out of the leaf may be important in controlling stress‐induced accumulation of ABA.
ENERGETIC CONSIDERATIONS OF ION TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK
Authors: RITCHIE RAYMOND J. 
Published: May 2006

SummaryThermodynamic analyses have already shown that K+and Cl−are taken up actively byEnteromorpha intestinalis(L.) Link cells and Na+is actively excluded in seawater and in low‐salinity media (25 mM Cl−). The proton motive force (pmf) has been estimated across the plasmalemma ofEnteromorpha intestinalis. The pmf is about zero in plants in seawater but in low‐salinity medium there is apparently a proton extrusion pump at the plasmalemma producing a pmf of about − 6 kj mol−1. Secondary active transport cannot be responsible for the active uptake of K+and Cl−or the active efflux of Na+by plants in seawater. It is thermodynamically possible (but unlikely) that K+is taken up by plants in low‐salinity medium by an electrogenic K+/H+coport mechanism but secondary active transport of Na+or Cl−is not thermodynamically possible. The Hodgkin‐Katz equation shows that the membrane potential ofEnteromorphain seawater is consistent with a diffusion potential but in low‐salinity medium (ACBSW, 25.5 mM Cl−) the observed membrane potential is more negative than the calculated diffusion potential in both the light and dark and an electrogenic proton extrusion pump appears to be likely in those plants.Various estimates of the power requirements of active transport of K+in, Cl−inand Na+outhave been made and compared to the power available from respiration and photosynthesis. Na+is very far from electrochemical equilibrium but the power consumption of Na+transport is less than 0.2 mW m−2because the Na+fluxes are very low. Even though both K+and Cl−are close to electrochemical equilibrium, the active transport of these ions accounts for most of the power consumed in ion transport. The power requirements of active K+and Cl−transport are approximately equal.In plants in seawater and low‐salinity medium photosynthesis provides about 400 mW m−2and respiration about 70 mW m−2of power which is available for the metabolism of the plant. In plants in seawater, the power dissipation necessary to maintain the observed K+, Cl−and Na+gradients is about 5 to 19 mW m−2or about 7 to 20% of the total respiratory power available in the dark. The power requirement of ion transport at low‐salinity is about 10 to 20 mW m−2and so would consume about 15 to 30% of the total power available in the dark. In the light the power requirement of ion transport is less than 5% of the total metabolic power available in both seawater and low‐salinity. The power requirements of active K+and Cl−transport are both large and it is not clear why the plant expends so much power on the active transport of Cl−. The metabolic power requirements of the active transport of K+and Cl−may account for the K+sensitivity ofEnteromorphain culture and in the field.
SOME RESPONSES OF LADINO CLOVER (TRIFOLIUM REPENS L. CV. REGAL) TO LOW CONCENTRATIONS OF SULPHUR DIOXIDE
Authors: MURRAY FRANK 
Published: May 2006

SummaryLadino clover (Trifolium repens L. cv. Regal) was exposed to mean SO2 concentrations of 215, 78 or 2.8 μg m−3* in open top fumigation hambers for up to 175 d. Exposure to 215 μg m−3 for 28 d significantly increased leaf area and number of leaves per plant, and exposure to 78 μg m−3 significantly reduced the shoot: root ratio, and increased the leaf area ratio, compared with control plants exposed to 2.8 μg m−3. Exposure to 215 or 78 μg m−3 had no significant effect on shoot or root weight, and all other effects had decreased beyond the level of statistically significant differences between treatment and control after 63 d of fumigation.Exposure to SO2 for 175 d had no effect on leaf protein concentration but exposure to 215 or 78 μg m−3 significantly reduced the concentrations of L‐ascorbic acid and starch in leaves, and increased the sulphur concentrations in the shoot. The specific energy of leaves was not significantly changed by 78 μg m−3 but was significantly increased by exposure to 215 μg m−3 of SO2 for 28 d and significantly decreased by the same concentration after 175 d. Exposure to SO2 for 175 d had no significant effect on the specific energy of shoots. The SO2‐induced reduction in ascorbic acid concentration may suggest a mechanism for reduced freezing resistance in plants exposed to SO2.
PHYSIOLOGICAL PROCESSES IN SOYBEAN INHIBITED BY GASEOUS POLLUTANTS BUT NOT BY ACID RAIN
Authors: NORBY R. J. , RICHTER D. D. , LUXMOORE R. J. 
Published: May 2006

SummaryThe responses of several physiological processes and indices were studied in soybean plants [Glycine max (L.) Merr. cv. ‘Davis’] exposed to combinations of polluted air (0.1 μl l−1 SO2+ 0.05 μl l−1 O3) and simulated acid rain (pH 3.4, 4.2 and 5.0). Plants exposed to the gaseous air pollutants had lower foliar concentrations of mineral nutrients and chlorophyll. Leaf abscission was increased and photosynthesis, nitrogen fixation, and vegetative growth were inhibited by SO2+ O3. There was no evidence of adverse effects from acid rain on the physiology of this cultivar, regardless of the gaseous pollutant treatment. In the absence of fundamental physiological dysfunctions, acid rain is unlikely to reduce yield; hence, this study with ‘Davis’ soybeans supports the conclusion of those field studies that have indicated no adverse effects of acid rain on soybeans.
DICHOTOMOUS BRANCHING IN LATERAL ROOTS OF PINE: TYPES OF FORKING IN LONG AND SHORT SECONDARY ROOTS OF PINUS RADIATA D. DON.
Authors: WILSON E. R. L. , FIELD R. J. 
Published: May 2006

SummaryThree classes of non‐mycorrhizal forking secondary roots on young seedlings of Pinus radiata D. Don grown in solution are described and illustrated. Roots are distinguished on the basis of their pattern and degree of forking and the extent of elongation before and after forking. Both long and short roots exhibited forking in the absence of mycorrhizal development.
THE SPREAD OF GLOMUS FASCICULATUM THROUGH ROOTS OF TRIFOLIUM SUBTERRANEUM AND LOLIUM RIGIDUM
Authors: SCHELTEMA M. A. , ABBOTT L. K. , ROBSON A. D. , DE'ATH G. 
Published: May 2006

SummaryThe lateral spread in a steamed lateritic podsol of Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe from localized inoculum was examined in two pasture species: Trifolium subterraneum L. (subterranean clover) and Lolium rigidum Gaud. (Wimmera ryegrass). Mycorrhizal infection was estimated 21, 28, 38 and 59 d after sowing at points 2, 4, 6, 8, 10, 14, 20 and 26 cm from the inoculum.The proportion of root length infected by G. fasciculatum at increasing distances from the inoculum could be best described by a Gompertz curve in both plant species at all harvests. Thus the curve had an upper plateau of the maximum percentage infection close to the inoculum, an exponential decline in the spread of G. fasciculatum and a lower plateau of infection. It is suggested that the pattern of spread of G. fasciculatum through roots of subterranean clover and ryegrass is related to changes in the amount of inoculum with distance from the point of inoculation, as well as over time.The rate of spread of the infection front was not constant. Thus it may not be appropriate to calculate mean rates of spread of mycorrhizal fungi over long time periods.
HOMOSERINE SYNTHESIS IN DARK‐GROWN AND LIGHT‐GROWN SEEDLINGS OF PISUM SATIVUM
Authors: MELCHER INGA M. 
Published: May 2006

SummaryThe synthesis of homoserine has been studied in pea seedlings (Pisum sativum L. cv. Rondo) supplied with l‐[U‐14C]amino acids. The results demonstrate that both labelled aspartate and glutamate produce similarly large quantities of labelled homoserine. It is suggested that, in addition to asparagine and glutamine, homoserine also has an important function as a transport metabolite.
POLYAMINES IN THE ROOTS OF TURNIP INFECTED WITH PLASMODIOPHORA BRASSICAE WOR.
Authors: WALTERS D. R. , SHUTTLETON M. A. 
Published: May 2006

SummaryThe concentrations of three amines (putrescine, spermidine and spermine) are much increased in ‘clubbed’ regions of roots of turnip infected by Plasmodiophora brassicae, whilst the concentrations, particularly that of putrescine, decreased in regions of infected roots not exhibiting symptoms of clubroot development. The possible involvement of these polyamines in the formation of ‘clubs’ on infected roots is discussed.
EXPERIMENTAL ECOLOGY OF DRYAS OCTOPETALA ECOTYPES: RELATIVE RESPONSE TO COMPETITORS
Authors: McGRAW JAMES B. 
Published: May 2006

SummaryA competition experiment was performed to determine the relative competitive abilities of fellfield and snowbed ecotypes of Dryas octopetala L. under conditions of high nutrients, high light, and high water availability. Pots were designed to allow the effects of root competition and shoot competition to be assessed separately. The large‐leaved snowbed ecotype responded positively to shoot competition, producing larger leaves and higher biomass than in control pots (no competition). Root competition resulted in a decrease in leaf size and an increase in root: shoot ratio, but no significant effect on shoot number or biomass accumulation. In contrast, the fellfield ecotype responded to shoot competition with an increase in root:shoot ratio, with no effect on biomass or shoot numbers. However, root competition caused a reduction in plant growth. Under growth chamber conditions of high resource availability, the snowbed ecotype is the superior competitor, probably due to ecotypic differences in both root and shoot characteristics.
A CONTRAST BETWEEN OOMYCETES AND OTHER TAXA OF MYCELIAL FUNGI IN REGARD TO METACHROMATIC GRANULE FORMATION
Authors: CHILVERS G. A. , LAPEYRIE F. F. , DOUGLASS P. A. 
Published: May 2006

SummaryForty‐nine cultures of mycelial fungi, representing five different taxonomic classes and diverse ecological groupings, were screened for the presence of metachromatic granules by staining hyphae with toluidine blue. Regardless of the ecological roles of the fungi, granules were detected in all representatives of the following classes: Zygomycetes, Ascomycetes, Deuteromycetes and Basidiomycetes. When selected mycelia were starved of phosphorus during growth, they lacked granules. However, these same mycelia would subsequently form granules readily if they were incubated for several hours in a phosphate‐containing solution, which supports the belief that these met achromatic granules represent a store of polyphosphate.No met achromatic granules could be detected in any of the fungi from the class Tomcats, which provides further evidence of the unique nature of this particular group of fungi. If their inability to form met achromatic granules is indicative of a limited capacity to store phosphorus, it could explain why no reliable examples have been discovered of Oomycete fungi forming symbiotic mycorrhizal associations with higher plants.
INFLUENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZA ON GROWTH, WATER RELATIONS, AND LEAF ORIENTATION IN LEUCAENA LEUCOCEPHALA (LAM.) DE WIT*
Authors: HUANG RUEY‐SHYANG , SMITH WILLIAM K. , YOST RUSSELL S. 
Published: May 2006

SummaryPlant growth characteristics, nutrient absorption and water relations were compared for plants of Leucaena leucocephala (Larn.) de Wir that were non‐mycorthizal and those that were infected with the vesicular‐arbuscular (VA) mycorrhizal fungus Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe. Mycorrhizal plants had substantially greater shoot and root dry weight, leaf area and root length than non‐mycorrhizal plants, and alsos greater P, K, and Ca uptake. Leaf area was over five times greater and leaf conductance to water vapour diffusion was nearly twice as great for mycorrhizal plants, yet the difference between xylem pressure potential and soil water potential were considerably less in mycorrhizal plants than in non‐mycorhizal plants. Stomatal responses to the humidity deficits of the air during the day were nearly twice as great in mycorrhizal plants. Leaflet folding and orientation responses to avoide direct sunlight during the day were also much greater in non‐mycorrhizal plants. Lower leaf conductances and increased leaf folding leading to less absorption of sunlight may contribute significantly to the reduction in growth rate observed in non‐mycorrhizal plants.
ECTOMYCORRHIZA FORMATION BY GLOMUS TUBIFORME
Authors: WARCUP J. H. 
Published: May 2006

Summary Glomus tubiforme Tandy, a white sporocarpic species with chlamydospores about 20 to 45 × 18 to 38 μm and fine hyphae ± 2 μm wide, forms ectomycorrhizas in association with a range of plants including Eucalyptus, Pinus and Quercus. The mycorrhizas have a thin sheath, one to a few cells thick, and a Hartig net. Glomus tubiforme has also been grown in agar culture on simple weak media.
RHIZANTHELLA GARDNERI (ORCHIDACEAE), ITS RHIZOCTONIA ENDOPHYTE AND CLOSE ASSOCIATION WITH MELALEUCA UNCINATA (MYRTACEAE) IN WESTERN AUSTRALIA
Authors: WARCUP J. H. 
Published: May 2006

Summary Rhizanthella gardneri R. S. Rogers, a rare subterranean achlorophyllous orchid which grows in Western Australia near plants of the Myrtaceous shrub Meialeuca uncinata R. Br. ex Alton f., is associated with an undescribed species of Rhizoctonia which forms hyphal coils within cortical cells of the orchid rhizome. The Rhizoctonia also forms ectomycorrhizas with sheath and Hartig net on Meialeuca uncinata and other ectomycorrhizal plants including Eucalyptus.Seeds of R. gardneri may germinate without the Rhizoctonia but their growth soon ceases unless the protocorm is invaded by the fungus through the protocorm hairs. Two plants of R. gardneri raised from seed in association with Rhizoctonia ectomycorrhizas on M. uncinata have flowered after 15 months.The Rhizanthella endophyte stimulated germination of seed of R. gardneri but not seed of two chlorophyllous terrestrial orchids, Prasophyllum regium R. Rogers and Microtis unifolia (Forster f.) Reichb. f. However, germination of these two orchids was stimulated by five of six other Rhizoctonias, including Tkanatephorus cucumeris (Frank) Donk and two species of Tulasnella, also isolated from soil and litter from two Rhizanthella sites.