bluuebunny/crossref_metadata_2025_split huggingface dataset:
Appropriate controls for vesicular–arbuscular mycorrhiza research
Authors: KOIDE ROGER T. , LI MINGGUANG 
Published: April 2006

SUMMARYSunflower (Helianthus animus L.) and mustard (Brassica hirta Moench.) plants were grown in autoclaved soil to which was added various components of soil inoculum. Use of inocula containing mycorrhizal propagules ultimately resulted in growth promotions which were related to improved phosphorus nutrition. Inoculation with soil containing mycorrhizal propagules caused an initial growth depression in comparison with plants receiving no inoculation, but inoculation with washed spores did not. For several reasons, the growth depression caused by inoculation with soil was not attributable to mycorrhizal infection. First, the growth depression was evident before mycorrhizal infections had become established. Second, the growth depression was also evident when either soil or soil sievings, both lacking mycorrhizal propagules, were used. Third, similar growth depressions were observed in mustard. The results suggest that careful selection of appropriate controls for mycorrhizal plants must be made, particularly if the emphasis is on early phases of plant growth. Use of non‐sterile soil reduced the extent of mycorrhizal infection.
Spread of endomycorrhizal colonization and effects on growth of apple seedlings
Authors: DOUD MILLER DIANE , BODMER MAJA , SCHÜEPP HANNES 
Published: April 2006

SUMMARYAn experiment to determine the short‐term characteristics of root colonization by two vesicular‐arbuscular (VA) mycorrhizal fungi with apple (Malus × domestica Borkh.) was initiated concurrently with an experiment to determine longer‐term effects of colonization by these fungi on the growth of apple seedlings. Short‐term characteristics of colonization were determined by sequential harvesting of a cuvette system which also allowed monitoring of hyphal spread from inoculated ‘spreader’ plants, through a root‐free soil region, to non‐inoculated ‘receiver’ plants. Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe exceeded Glomus macrocarpum Tul. & Tul. in rate of initial colonization, amount of maximum colonization, and persistence of arbuscules and external hyphae. Colonization by either fungus reduced shoot fresh weight 11 days after inoculation but increased shoot and total fresh weight by day 38. Hyphae of G. mosseae had traversed through 2 and 3 cm of root‐free soil to colonize non‐inoculated ‘receiver’ roots by 29 days, and hyphae of G. macrocarpum by 38 days. G. mosseae colonized ‘receiver’ roots more intensely than did G. macrocarpum at 2 and 3 cm, and 3 and 4 cm distance, at subsequent harvests. The fungi were effective, singly and in combination, in increasing apple plant biomass, as compared to non‐mycorrhizal controls. Relative height growth rate, and colonization at harvest, of G. macrocarpum‐inoculated plants were less than those of G. mosseae‐inoculated or G. mosseae + G. macrocarpum‐ inoculated plants, but greater than those of the non‐mycorrhizal control trees.
Chitin‐decomposing actinomycetes associated with a vesicular–arbuscular mycorrhizal fungus from a calcareous soil
Authors: Ames R. N. , Mihara K. L. , Bayne H. G. 
Published: April 2006

SUMMARYSpores of Glomus macrocarpum Tul. & Tul. were sieved from a calcareous, silty clay loam soil, washed in sterile water, and plated on chit in agar for the isolation of actinomycetes. Of the 190 spores examined, 100 were colonized by one or more chitin‐decomposing microorganisms: 82% were colonized by actinomycetes, 17% by bacteria, and 1 % by fungi. Fifty‐one actinomycete isolates were classified on the basis of morphological, cultural and biochemical criteria. Tentative identifications to genera and numbers of different isolates are as follows: Streptomyces (29); Nocardia (3); Streptosporangium (1); Streptoverticillium (1); Intrasporangium (1); Nocardiodes (1); and unidentified (15). This is the first study to report the prevalence and diversity of chitin‐decomposing actinomycetes associated with spores of a vesicular‐arbuscular mycorrhizal fungus in field soil.
Differential heat sensitivity amongst four populations of the lichen Ramalina menziesii Tayl.
Authors: Larson D. W. 
Published: April 2006

SUMMARYAn investigation was made of the degree of physiological differentiation in response to high temperatures, in the lichen Ramalina menziesii Tayl. The range of this species extends from cool coastal rainforest in British Columbia, Canada to hot and dry coastal desert in Baja California del Sur, Mexico. Thalli were collected from four extreme positions within the range and exposed to temperature pretreatments ranging from 20 to 70 °C in 10 °C increments for 7‐5 h. Rates of net photosynthesis, dark respiration and calculated gross photosynthesis were then determined. There was physiological differentiation among the four populations at a narrow range of pretreatment temperatures so that Thalli derived from the site with the least heat stress show the least resistance, while Thalli derived from the site with the most heat stress show the most heat resistance. This suggests that physiological as well as morphological plasticity is important to the ecology of this lichen. It also suggests that high temperatures alone do not act to restrict the distribution of this species.
Anatomy of a vesicular—arbuscular endomycorrhizal symbiosis between sugar maple (Acer saccharum Marsh) and Glomus etunicatum Becker & Gerdemann
Authors: YAWNEY W. J. , SCHULTZ R. C. 
Published: April 2006

SummaryMicroscopic analysis of infection development by Glomus in sugar maple roots revealed changes in the cortical cells similar to those reported by other workers using either herbaceous or woody plant hosts. Few cortical cells contained exclusively terminate hyphal structures. Instead, large intracellular hyphae entered and exited cortical cells while arbuscules formed from initiation points at various places on the intracellular hyphae. Intercellular hyphae were rare and vesicles were not observed. The beaded root morphology observed did not seem to influence the infection process. Beaded roots are formed from repeated constrictions in feeder roots due to major reductions in cell size. The relationship between the constrictions and moisture stress is discussed. The living arbuscule seemed to be the site of transfer between the host and endophyte, implying that the process is an active one.
The role of the external mycelial network in the effect of soil disturbance upon vesicular—arbuscular mycorrhizal colonization of maize
Authors: EVANS D. G. , MILLER M. H. 
Published: April 2006

SummaryThis study examined the mechanism by which vesicular‐arbuscular (VA) mycorrhizal colonization of young maize (Zea maysL.) plants is inhibited by soil disturbance. Attention focussed upon the role of the external mycelial network.Plastic cylinders were divided into a central and two outer compartments by a fine nylon mesh screen which was impervious to roots but not to mycorrhizal hyphae. Soil was packed into each compartment and maize plants grown in the outer compartments over a series of 3‐week cycles, leaving root‐free central sections. Prior to a final growth cycle, the root‐free soil in the central compartment was either disturbed and repacked or left undisturbed. In a third treatment the hyphal connections between the outer and central sections were severed, while leaving the soil in all sections undisturbed. Plants were then grown in the central compartments.Mycorrhizal colonization and shoot P and Zn concentrations of plants grown in the root‐free zones were substantially reduced by disturbance of the soil. The reduction in colonization was similar to that found in control pots in which the root system and mycelial network were disturbed. This suggested that destruction of the hyphal network is an important component in the disturbance phenomenon. Removal of hyphal connections with roots in the outer compartments had no effect on colonization or nutrient absorption. Isolation of the mycelial network from the root system from which it had originated did not then seem to affect its infectivity.The mycelial network appears to be an important component of the inoculum potential of an undisturbed soil and it is likely that its destruction is directly responsible for much of the effect of soil disturbance upon mycorrhizal colonization. Evidence is presented indicating that the undisrupted mycelial network may also increase the nutrient absorption capacity independent of the degree of colonization.
First syntheses of ectomycorrhizas between Afzelia africana Sm. (Caesalpinioideae) and native fungi from West Africa
Authors: BA A. M. , THOEN D. 
Published: April 2006

Summary Afzelia‐associated fungi in Senegal were isolated from sporocarps, sclerotia and ectomycorrhizas. The choice of sterilizing agent was critical for the success of isolation. Osmic acid was more efficient than mercuric chloride, hydrogen peroxide and calcium hypochlorite. Isolates were tested for their ability to form mycorrhizas in vitro and their mycelia in pure culture were described. Sclerotia linked to mycorrhizas of Scleraderma verrucosum Pers. were also isolated and their infectivity checked. Among isolates from sporocarps, only Scleroderma dictvosparum Fat. and S. verrucosum Pers. formed ectomycorrhizas with Afzelia africana Sm. Two native Amanita spp. and two introduced isolates belonging to the genus Pisolithus did not form typical ectomycorrhizas although a normal mantle was observed.
Light‐enhanced convective throughflow increases oxygenation in rhizomes and rhizosphere of Phragmites australis (Cav.) Trin. ex Steud.
Authors: ARMSTRONG J. , ARMSTRONG W. 
Published: April 2006

SummaryThe convective throughflow of gases found recently in Phragmites australis increased with increasing fluxes of photosynthetically active radiation. Despite this, the oxygen in the venting gases remained lower than in air and the convection is thought to depend mainly on a humidity‐induced diffusion of atmospheric gases across the leaf sheaths. When convection was prevented, and aeration was dependent entirely upon diffusion, no photosynthetic enhancement of rhizome and root aeration could be detected.In terms of oxygen transport, rapid rates of convection were much more effective than diffusion and substantially enhanced the entry of oxygen into the rhizome system. This resulted in large increases in the efflux of oxygen into the rhizospheres of basal laterals and apical and sub‐apical regions of the adventitious roots. This effect was attributed to a greater diffusion of oxygen from rhizome to root. Substantial diurnal fluctuations in rhizome oxygen regimes and in root oxygen efflux occurred.It is estimated that because of convection and diffusion, up to 0.31 kg of oxygen d−1 m−1 may enter the rhizome system of vigorous stands of Phragmites during summer months. By comparison, diffusion alone could be expected to supply less than 0.01 kg d−1. Scanning electron micrographs of root‐shoot junctions showed that the resistance to gaseous diffusion from rhizome to roots must be especially small in Phragmites.
Growth of Pyrola rotundifolia ssp. maritima in relation to shade
Authors: HUNT RODERICK , HOPE‐SIMPSON J. F. 
Published: April 2006

SummaryThe maritime race of the larger wintergreen [Pyrola rotundifolia L. ssp. maritima (Kenyon) E. F. Warb.] was investigated in relation to its light environment at Braunton Burrows in south‐west England.Measurements made at the site of its greatest abundance indicated that, in July, Pyrola commonly experiences an irradiance which is below 10% of full daylight with some habitats providing less than 1%. The species also occurs in situations receiving up to 100% daylight; at or towards this extreme the foliage is yellowish‐green instead of deep green, giving an impression of reduced luxuriance.The mean specific leaf area of plants growing in the field was found to be inversely related to mean percentage irradiance received at each site. However, the slope of this trend was slight.Detached, rooted rosettes were removed from the field and grown for 85 days in a glasshouse under treatments which provided 100, 20.2 and 6.1% daylight. The plants in all treatments appeared normal but growth was slow. Yields and relative growth rates were significantly reduced by shading (P 0–05). The depressing effect of shading on growth rate was very slightly less than on unit leaf rate, the difference being due to slight increases in leaf area ratio. This, in turn, was tracted entirely to small increases in specific leaf area. Leaf weight ratio was not affected significantly, nor were substantial effects recorded in root/shoot ratio or in fresh weight/dry weight ratio.We conclude that the vegetative growth of Pyrola has a low capacity for adjustment to both natural and experimental shading; its growth rate in the field will tend to be lower under a dense leafy canopy than in less shaded habitats. The inherently low growth rate might, however, be an advantageous feature under shade conditions. The evident success of the species in shaded situations is certainly due to factors other than a simple shade requirement for vegetative growth.
Crystal occurrence and wax disruption on leaf surfaces of cabbage treated with simulated acid rain
Authors: ADAMS CINDY M. , CAPORN SIMON J. M. , HUTCHINSON THOMAS C. 
Published: April 2006

SummaryEpicuticular waxes on leaves of Brassica oleracea L. (cabbage) were studied using scanning electron microscopy after a single treatment with simulated rain of pH 5.6, 3.0 or 2.5 which was either sprayed on to plants in an exposure chamber or applied as droplets with a micropipette. Treatments with acidified rain caused serious structural degradation of the wax crystals. The alteration of crystalline wax structures was similar for leaves treated with nitric acid solutions, but less severe, than for leaves treated with sulphuric acid solutions. With both H2SO4, and HNOa‐derived rain solutions numerous gypsum (CaSO4) crystals were found in and near lesions on the leaves treated with rain of pH 3.0 and 2.5. The crystals probably resulted from damage of cuticular membranes by acidic rain which significantly altered their permeability to ions in the area of lesions. Crystalline leaf waxes may be an important target for acidic pollutants, and the physiological consequences of their degradation are discussed.
The stimulation of CAM activity in Mesembryanthemum crystallinum in nitrate and phosphate‐deficient conditions
Authors: PAUL M. J. , COCKBURN W. 
Published: April 2006

SUMMARYPlants of Mesembryanthemum crystallinum L. were grown from seed in phosphate‐sufficient and phosphate‐deficient conditions. Separate plants were subjected to nitrate deficiency by removing nitrate from the rooting medium of previously nitrate‐sufficient plants. Subsequently, they were also irrigated with 400 mM NaCl to induce CAM. Plants of M. crystallinum with induced CAM that had been grown in complete nutrient medium were deinduced by rehydration.Nitrate and phosphate deficiencies caused enhanced CAM activity prior to salt treatments. After salinisation, phosphate deficiency also caused higher background levels of malate. Prolonged nitrate deficiency reduced CAM activity.Endogenous P1 levels in phosphate‐sufficient plants correlated with CAM activity. However in phosphate‐deficient plants CAM occurred without a significant rise in P1 content. Levels of endogenous P1 appeared more related to nitrate deficiency than to CAM or salt treatment. Nitrate and phosphate deficiencies and salt treatment could all cause a nitrate deficiency within the leaf, causing high endogenous P1 when available in the rooting medium. It is speculated that a change in nitrogen status could play a role in the initiation of CAM induction in M. crystallinum. A further possibility is that CAM could be induced by reduced water potential due to dehydration and increased ion content in saline conditions, and by an inhibition of growth and concomitant accumulation of solutes in phosphate‐ and nitrate‐deficient conditions.
Changes in intracellular amino acids and glutamine : glutamate during N‐deprivation and feeding in Candida nitratophila
Authors: FLYNN K. J. , HIPKIN C. R. 
Published: April 2006

SUMMARYIn the yeast, Candida nitratophila Shifrine et Phaff, the intracellular concentrations of α‐amino acids decreased rapidly during N‐deprivation, with the ratio of glutamine: glutamate (Gln: Glu) falling from 07 in NH4+‐grown cells, or 0.5 in NO3−‐grown cells, to 0.1 after 1 h. Addition of NH4+ to N‐deprived cultures resulted in rapid increases in glutamate, glutamine and alanine with Gln: Glu exceeding 1.5 within 30 min. Recovery of other amino acids, such as arginine, was much slower. Addition of NO3, resulted in a less rapid increase in the concentration of some intracellular amino acids, including glutamate and glutamine, while levels of arginine continued to fall for 30 min after addition of this N‐source. Gln: Glu was slow to rise in NO3− pulsed cells. Addition of NH4+ to cells growing on NO3− produced little change over the following 2 h other than decreases in arginine and histidine. Carbon deprivation resulted in a rapid decrease in levels of glutamate, glutamine and alanine, but not of aspartate (which this yeast is unable to use as a sole C‐source for growth) or arginine. Gln: Glu increased during C‐deprivation but fell within 10 min to normal levels on addition of glucose. It is concluded that, in C. nitratophila, Gln:Glu values correlate well with C‐N status.
The influence of ozone and acid mist on the amount and wettability of the surface waxes in Norway spruce [Picea abies (L.) Karst.]
Authors: BARNES J. D. , BROWN K. A. 
Published: April 2006

SUMMARYThree‐year old Norway spruce [Picea abies (L.) Karst.] trees from two clones (4076 and 4102) of a medium altitude southern German provenance were transplanted in May 1986 into an acid brown earth soil. During the summers of 1987 and 1988 the trees were exposed in large‐scale fumigation chambers (solardomes) to ozone at 100 or 20 nl 1−1 (control). Acid (pH 3.6) or control mist (pH 5.5) was applied daily to trees. The wettability of current and 1‐year‐old needles was assessed in November 1988 by measuring the contact angle of water droplets placed on needles, and the amount of surface wax was determined. The contact angle of water droplets on current and 1‐year‐old needles was significantly reduced by 100 nl 1−1 PPB ozone and/or acid mist, indicating that the wettability had increased, but the combined effect of ozone and acid mist was no more than additive. Exposure to the pollutants resulted in a slight decrease in the quantity of surface wax, but the effect was not significant. Ozone and acid mist treatment also increased the projected area of needles relative to their dry weight. The possible involvement of such effects in forest decline are discussed.
Growth responses of barley exposed to SO2
Authors: MURRAY FRANK , WILSON SUSAN 
Published: April 2006

SUMMARYBarley (Hordeum vulgare ev. Schooner) plants were exposed to 4, 42, 121, 256 or 517 nl 1−l SO2 to investigate the relationship between the exposure concentration of SO2 and growth. The plants were exposed from 14 days old, in open‐top chambers for 4 h day−1 (10.00‐14.00 h) for 79 days. The concentration‐response curves established illustrated a small growth stimulation (approx. 10%) at 42 nl 1−1 and a growth inhibition at 121 nl 11− or greater. The growth reduction was generally proportional to the exposure concentration at concentrations above 42 nl 1−1 Sulphur concentration in the shoot increased linearly with ambient SO2 concentration.
Evidence for early changes in membrane structure during post‐harvest development of cut carnation (Dianthus caryophyllus L.) flowers
Authors: PALIYATH G. , THOMPSON J. E. 
Published: April 2006

SUMMARYFreeze‐fracture electron microscopy and X‐ray diffraction have indicated that there are marked alterations in membrane structure prior to the initiation of increased ethylene production and petal inrolling during post‐harvest development of cut carnation flowers. In replicas of petals from partially open flowers (stage 1 of post harvest development), an even distribution of intramembranous particles, which is characteristic of normal membranes, was evident on the fracture plane of the plasma membrane. By contrast, endoplasmic reticulum membranes had begun to develop intramembranous particle‐free areas indicative of gel phase lipid domains. By stage 2 of development, when the flowers were fully open, large areas devoid of intramembranous particles were apparent on the plasma membrane as well. The presence of gel phase lipid was confirmed by wide‐angle X‐ray diffraction of isolated microsomes. Imaginations reflecting microvesiculation were also discernible in the fracture planes of plasma membrane at stage 2 of development and vesicles lying adjacent to the cell surface were evident in the cytoplasm. These observations collectively indicate that there are deteriorative alterations in membrane structure during the very early stages of post‐harvest development in cut carnation flowers. They also provide an explanation for the previous finding that carnation petals become leaky well before morphological symptoms of senescence such as petal inrolling are apparent.
The fate of soil‐derived phosphorus in mycelial cord systems of Phanerochaete velutina and Phallus impudicus
Authors: WELLS J. M. , HUGHES C. , BODDY LYNNE 
Published: April 2006

SUMMARYThis study demonstrated the direct uptake of [32P]phosphorus from soil by ‘foraging’ cord systems of Phanerochaete velutina (DC: Pers.) Parmasto and Phallus impudicus (L.) Pers., grown from 4 cm3beech (Fagus sylvatica L.) wood inocula. Total uptake was independent of, but ‘allocation’ within cord systems dependent on, species, the state of decay of wood inocula, and phosphorus availability in different parts of cord systems. Cords were shown to be functional pathways for translocation of 32P between distant resource units and more than 90 % of accumulated phosphorus was translocated to the inocula or to new resource units. Allocation of opportunistically‐scavenged phosphorus was in preferential order of the potential of new resource units as carbon sources and in proportion to the mass of like resource units. Non‐destructive 32P determination, using a scintillation probe, showed that significant differences (P 0.05) in allocation to combinations of new resource units could be detected within 12 d and corresponded with the results of destructive total 32P determination after nine weeks. The results are discussed in terms of the role of saprotrophic cord‐forming basidiomycetes in nutrient cycling and the efficiency of nutrient allocation within their cord systems.