bluuebunny/crossref_metadata_2025_split huggingface dataset:
INFLUENCE OF SOIL WATER STRESS ON WILTING AND WATER RELATIONS OF DIFFERENTLY OSMOTICALLY ADJUSTED WHEAT PLANTS
Authors: JENSEN C. R. 
Published: May 2006

SummaryDuring a pretreatment period of 1 week, spring wheat plants (Triticum aestivum, L., cv. ‘Sappo’) grown in a sandy soil in pots were adjusted to three levels of soil water osmotic potential induced by watering the plants with a nutrient solution (minus 0·5 bar) and further additions of KNO3 (minus 3 and minus 6 bar). After leaching of the soil, the plants were exposed to two drying cycles separated by rewetting. With severe water stress at the end of drying cycle 1, reduction of wilting was highly correlated with lowering of leaf osmotic potential due to the KNO3pretreatment. Turgor potential was highest and decreased at lowest soil water matric potentials in KNO3 pretreated plants. Recovery after rewatering was seemingly most accelerated in KNO3 pretreated plants due to a larger potential difference between leaf and soil water. The leaf and soil water matric potentials at which stomata closed were lowered as a result of both KNO3 pretreatment and the effect of previous water stress on leaf osmotic potential.
SPECIFICITY IN THE GUNNERA‐NOSTOC ENDOSYMBIOSIS
Authors: BONNETT HOWARD T. , SILVESTER WARWICK B. 
Published: May 2006

SummaryThe cyanobacterium, Nostoc, and the angiosperm, Gunnera, form a symbiotic association in which glandular cells host an intracellular population of heterocystous Nostoc cells. Symbiotic and free‐living isolates of Nostoc and Anabaena were assayed for their ability to infect, fix nitrogen and supply nitrogen to Gunnera. The range of cyanobacteria acceptable to Gunnera was found to be circumscribed by the genus, Nostoc, but included six different isolates within that genus. The effectiveness of the various Nostoc isolates was compared in terms of their activities at both the inter and intracellular levels of symbiotic association.
ULTRASTRUCTURE OF THE SEAGRASS RHIZOSPHERE
Authors: KUO J. , MCCOMB A. J. , CAMBRIDGE M. L. 
Published: May 2006

SummaryBacterial colonies, fungi and other micro‐organisms occur in the rhizosphere and peripheral root tissues of seagrasses of the genus, Posidonia. Fungi penetrate the epidermal cells and lyse the thick polysaccharide materials in the walls of the hypodermal cells. A suberin lamella in the wall of the hypodermal cell is more resistant but fungi and bacteria occur both within the lumen of hypodermal cells and in cortical cells adjacent to the hypodermis. It is suggested that these micro‐organisms in the rhizosphere and peripheral root tissues may be involved in nutrient uptake and nitrogen fixation into seagrasses.
QUANTITATIVE BIRCH (BETULA L.) POLLEN SEPARATION BY ANALYSIS OF SIZE FREQUENCY DATA
Authors: PRENTICE I. C. 
Published: May 2006

SummaryThe Gordon—Prentice maximum likelihood method for estimating proportions of morphologically overlapping pollen taxa in a mixture requires knowledge of the underlying frequency distributions. This requirement is hard to fulfil when size is the discriminating character. However, if normality can be assumed the underlying distributions can be inferred from the data. This indirect approach ‐ due to Usinger ‐ permits reliable separation of Betula species in northwest European pollen diagrams. Techniques for separating mixtures of known distributions and for estimating underlying normal components are compared and assessed. For illustration, birch pollen size data from a Late Weichselian/early Holocene sequence in Finnmark, Norway (H. C. Prentice, unpublished) are subjected to a simple graphical technique to derive (two) normal components and then to the Gordon‐Prentice method and an analytical least‐squares method to estimate proportions. The inferred distributions are broadly consistent with Usinger's for Betula nana and Betula pubescens. The results show an Allerød‐Younger Dryas fall in the pollen percentage of Betula nana, a Betula pubescens rise at the beginning of the Holocene (interpreted as long‐distance pollen transport), and a subsequent major Betula nana expansion concurrent with the regional Ericales maximum.
LIMITATIONS OF PHOTOSYNTHESIS IN DIFFERENT REGIONS OF THE ZEA MAYS LEAF
Authors: MIRANDA VALENTINE , BAKER NEIL R. , LONG STEPHEN P. 
Published: May 2006

SummaryThe progressive development of the photosynthetic apparatus occurring along the length of the Zea mays leaf offers a convenient system with which to examine the limitations to photosynthetic CO2 assimilation during biogenesis of a C4 leaf. Changes in light‐induced O2 evolution and CO2 assimilation, chlorophyll content, activity of PEP‐carboxylase, NADP‐malic enzyme and the ‘R5P system’ (consisting of d‐ribose‐5‐phosphate‐keto isomerase, ATP‐d‐ribulose‐5 phosphate 1‐phosphotransferase and d‐ribulose‐1,5‐bisphosphate carboxylase) and fluorescence emission characteristics were examined along the length of the second leaf of 7‐day‐old plants grown under a diurnal light regime. The results suggest that the major limitation to CO2 assimilation in the leaf sheath lies within the chlorenchyma and is either energy supply for carboxylation or the capacity of key photosynthetic enzymes. In the leaf blade stomatal resistance to CO2 diffusion constitutes a major fraction of the total leaf resistance to CO2 assimilation implicating the stoma as the major limiting factor to photosynthetic CO2 assimilation.
AN ECOPHYSIOLOGICAL STUDY OF THE SALT SECRETION OF FOUR HALOPHYTES
Authors: ROZEMA JELTE , GUDE HENK , POLLAK GAD 
Published: May 2006

SummaryPlants of Spartina anglica, Limonium vulgare, Armeria maritima and Glaux maritima were collected in the field and grown on different concentrations of NaCl, KCl and CaCl2. Salt secretion, ion content, water content and transpiration rates were determined. The highest sodium secretion was found in Spartina anglica, a species from the most saline habitat; and a somewhat lower secretion rate in Limonium vulgare. The lowest rates were found in Glaux maritima and Armeria maritima. The sodium secretion efficiency, i.e. the ability to maintain an unchanged internal sodium content, was highest in Spartina anglica. Spartina anglica is the most successful in the removal of excessively absorbed salt, since it secretes 60% of the absorbed sodium. The values for Limonium vulgare, Glaux maritima and Armeria maritima were 33, 20 and 4% respectively. The species studied differ in the preferential sequence of ion secretion as well as in secretion rate and efficiency. This preferential sequence of ion secretion seems to be similar in members of the same taxonomic group (Plumbaginaceae). The comparability of the secretion parameters is discussed with regard to morphological differences between the species.
ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZAS IN THE ERICACEAE II.
Authors: BONFANTE‐FASOLO P. , BERTA G. , GIANINAZZI‐PEARSON V. 
Published: May 2006

SummaryThe endomycorrhizal infection in Vaccinium myrtillus is limited to the cortical cells of the fine hair roots; the fungi responsible have simple septa with associated Woronin bodies (Ascomycetes). Hyphae penetrating into cells are surrounded by a layer of inner host wall material which diminishes with intracellular development of the fungus. In living cells hyphae are separated from host cytoplasm by continuous host plasmalemma and there is no evidence of their lysis or digestion by the plant cell. This biotrophic relationship (living host cell and fungus) appears to predominate in late summer and autumn when new root formation and mycorrhizal infection are most important. During other periods of the year living or dead fungus in moribund host cells seem to be the most common situation.
BACTERIUM‐LIKE ORGANELLES IN THE VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS CALEDONIUS
Authors: MACDONALD R. M. , CHANDLER MURIEL R. 
Published: May 2006

SummaryBacterium‐like organelles (BLOs) were found by electron microscopy in the vesicular‐arbuscular (VA) mycorrhizal fungus Glomus caledonius. They were morphologically similar to those found by others in other V A mycorrhizal fungi, in the ectendomycorrhizal fungus Endogone flammicorona and in the Discomycete Scutellinia. They occurred free in the cytoplasm of Glomus caledonius reproductive spores and in the intercellular hyphae and thick arbuscule branches in infected roots. They were irregularly coccal with diameters of 0·3 ± 0·06 μm and had a conspicuous cell membrane and simple cell wall and appeared to divide by median constriction and separation. The fungal cytoplasm did not show any cytopathic effects in the vicinity of the BLOs.A competely different type of bacterium colonized and eroded the walls of reproductive spores of Glomus caledonius. These bacteria did not enter the fungal cytoplasm and had a thick complex wall and peripheral membranes. In contrast to BLOs, their cytoplasm was clearly differentiated into electron‐dense and transparent areas.
CARBON METABOLISM OF SPARTINA ALTERNIFLORA LOISEL IN RELATION TO THAT OF ASSOCIATED NITROGEN‐FIXING BACTERIA
Authors: BOYLE C. D. , PATRIQUIN D. G. 
Published: May 2006

SummaryRelationships between the carbon metabolism of the C4 salt‐marsh grass, Spartina alterniflora Loisel, and that of root and rhizosphere soil diazotrophs were investigated. Experiments involving addition of carbon compounds demonstrated that acetylene reducing activity (ARA) of both populations was dependent upon compounds from roots soluble in 80% ethanol. Of these, sugars (glucose, fructose and sucrose) were most effective in increasing ARA of the soil diazotrophs, while organic acids (malate) increased ARA of root diazotrophs. ARA of both populations was dependent upon carbon sources from large carbon pools. 14CO2 labelling of plants demonstrated that sugars were the only quantitatively significant photosynthates translocated to the roots and that these entered large carbon pools. After longer periods, labelled sugars were detected in rhizosphere soils where they were metabolized (possibly by diazotrophs) to form acidic and basic compounds. The possibility that dark CO2 fixation by roots or bacteria provided malate for the root diazotrophs was investigated.
THE EFFECT OF NITROGEN AVAILABILITY ON GROWTH AND CELLULOLYSIS BY SERPULA LACRIMANS
Authors: WATKINSON S. C. , DAVISON E. M. , BRAMAH J. 
Published: May 2006

SummaryThe effect of sodium nitrate level on three parameters of growth of Serpula lacrimans was investigated and compared with nitrogen levels normal in wood. The results showed that mycelial extension from a wood food base over non‐nutrient substrata is probably not limited by nitrogen availability, but that the rate of increase in mycelial biomass and of cellulose decomposition probably are. The nitrogen required for cellulolysis could be translocated to the site of cellulolysis when supplied at a distance from it. The results are discussed in relation to the biology of the fungus.
SPATIAL DEVELOPMENT OF POPULATIONS OF CORIOLUS VERSICOLOR
Authors: WILLIAMS E. N. D. , TODD N. K. , RAYNER A. D. M. 
Published: May 2006

SummaryVarious combinations of dikaryons and monokaryons of the wood‐rotting Basidiomycete Coriolus versicolor (L. ex Fr) Quél. were inoculated evenly spaced into Petri dishes containing 3% malt agar, or birch logs placed in a woodland site. The resulting patterns of colonization were similar to those found in natural populations of the fungus, with individual dikaryons present in discrete regions delimited by zones of mutual antagonism. Different dikaryons had similar growth rates and occupied approximately equal areas or volumes when inoculated simultaneously on to agar or into wood respectively. Simultaneous and sequential inoculation of sexually compatible monokaryons on to agar demonstrated that growth rate of the monokaryons and patterns of dikaryotization and nucleus migration between them are likely to be crucial determinants of the spatial distribution of dikaryons in a population. Monokaryons inoculated into logs in the field quickly became dikaryotized, and the resulting dikaryons contained diverse mating‐type factors indicating the presence of a heterogeneous spore rain.
THE AZOLLA‐ANABAENA AZOLLAE RELATIONSHIP
Authors: KAPLAN D. , PETERS G. A. 
Published: May 2006

SummaryThe fixation of 15N2 and its transport were studied as a function of leaf development along the main stem axes of Azolla.Main stem axes dissected from Azolla caroliniana Willd. plants, and sequential groups of leaves along the axes, had 25 to 35 % less nitrogenase activity than the undissected controls when assayed immediately. However, they exhibited activities equivalent to those of the intact controls when allowed to recover for 12 h or more prior to assaying. Nitrogenase activity was determined as a function of leaf age by measuring 15N2 fixation and C2H2 reduction in parallel samples. The reduction of both substrates was very low in the apical region, increased rapidly with leaf maturation and plateaued prior to declining as leaves began to senesce. Whereas the nitrogen content and dry matter decreased with increasing leaf age, the C:N ratio increased. These findings are consistent with the demonstration that nitrogen fixed by the endophytic Anabaena in mature leaves is transported toward the stem tip where undifferentiated but actively dividing filaments of the endophyte are associated with the apex and leaf primordia.
GERMINATION OF THE DIMORPHIC FRUITS OF BIDENS PILOSA L.
Authors: FORSYTH C. , BROWN N. A. C. 
Published: May 2006

SummaryDimorphic fruits of Bidens pilosa were tested separately for differences in germinability and seedling development. The long achenes were found to germinate readily under a wide range of conditions while the short achenes showed fairly exacting germination requirements. Germination of the short achenes was found to be enhanced by red light treatment, scarification, applied hormones, leaching and increased oxygen tensions. Seedlings originating from short achenes showed lower survival rates and initially slower development than those originating from the long achenes. The implications of the morphological differences and differences in germination and development of the two achenes are discussed.
THE EFFECTS OF SALINITY AND WATERLOGGING ON THE GROWTH AND CATION UPTAKE OF SALT MARSH PLANTS
Authors: COOPER ALAN 
Published: May 2006

Summary Festuca rubra, Juncus gerardii, Armeria maritima, Plantago maritima, Aster tripolium, Triglochin maritima, Puccinellia maritima and Salicornia europaea from a salt marsh near Portaferry, County Down, were grown on drained and waterlogged salt marsh soils under saline and non‐saline conditions. Shoot and root yields and the concentrations of sodium, potassium, calcium, magnesium, manganese and iron in the shoots were determined after a 2‐month growing period. The tolerance of the plants to waterlogging and salinity differed in a way which was correlated with their position on the salt marsh ecotone.The growth of upper marsh species, but not that of lower marsh species, was strongly limited by both salinity and waterlogging. Only Salicornia europaea gave its maximum yield on the saline treatments and only Puccinellia maritima showed a preference for waterlogged soils. Reduced yields on the saline treatments were associated with large increases in shoot sodium concentrations but in general, salinity and waterlogging had little effect on shoot cation concentrations. It is suggested that factors other than the greater availibility of iron and manganese on araerobic salt marsh soils are involved in determining species distribution along the salt marsh ecotone.
INFLOW OF PHOSPHATE INTO MYCORRHIZAL AND NON‐MYCORRHIZAL PLANTS OF TRIFOLIUM SUBTERRANEUM AT DIFFERENT LEVELS OF SOIL PHOSPHATE
Authors: SMITH S. E. 
Published: May 2006

SummaryDuring early growth of mycorrhizal and non‐mycorrhizal plants of Trifolium subterraneum fertilized with soluble (Na2HPO4) phosphate, inflow of phosphate (moles P absorbed per unit length root per unit time) into mycorrhizal roots from soil exceeded that into non‐mycorrhizal roots over a range of levels of phosphate. High rates of uptake (up to 45 × 10−15 mol phosphate cm−1 s−1) were associated with reductions in root: shoot dry wt ratios.The length of mycorrhizal root per plant was little affected by fertilization with phosphate. However, rapid growth of roots at high levels of Na2HPO4 resulted in reductions in percentage root length infected by mycorrhizas. Results are discussed with respect to rates of uptake by whole plants and to differences in distribution of phosphate between roots and shoots in mycorrhizal and non‐mycorrhizal plants.
LOCALIZATION AND CHANGES IN CATECHIN AND TANNINS DURING DEVELOPMENT AND RIPENING OF COTTONSEED
Authors: HALLOIN JOHN M. 
Published: May 2006

SummaryTannnins and their precursor, (+)‐catechin, are localized primarily in the pigmented layers of the cottonseed coat and in seed linters. Lesser quantities are localized in the nucellus and in the palisade parenchyma of embryo cotyledons. Oxidation of seed coat tannins during seed ripening is accompanied by seed coloration and reduction of seed coat permeability to water. Localization and changes in cottonseed flavanols and tannins during seed development and ripening are consistent with their proposed functions as (1) chemical barriers against infection by fungi, (2) physical barriers against absorption of water, and (3) chromogens in baked products containing cottonseed products.
THE OCCURRENCE OF BACTERIUM‐LIKE ORGANELLES IN VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: MACDONALD R. M. , CHANDLER MURIEL R. , MOSSE BARBARA 
Published: May 2006

SummaryBacterium‐like organelles (BLOs), morphologically indistinguishable from those which occur in Glomus caledonius and Acaulospora laevis have been found in the spores of Glonius mosseae, Gigaspora margarita, Gigaspora heterogama and an unidentified white reticulate vesicular‐arbuscular mycorrhizal spore. Morphologically different BLOs were also found in Gigaspora margarita and the white reticulate spores. The significance of the organelles is discussed.
ROLE OF TEMPERATURE IN THE SEASONAL DORMANCY OF SEEDS OF VERONICA HEDERIFOLIA L.
Authors: ROBERTS H. A. , NEILSON JUNE E. 
Published: May 2006

SummaryHigh temperatures (10 to 30 °C) promoted after‐ripening of fresh, imbibed seeds of Veronica hederifolia L. and overcame dormancy of seeds buried in the soil. Low temperature (4 °C) inhibited after‐ripening and also tended to induce dormancy in physiologically non‐dormant seeds. This response, however, was not sufficient to account for the increase in dormancy which occurs during late autumn and winter in seeds buried in the field.
THE EFFECT OF A FOREIGN POLLEN ON OVULE DEVELOPMENT IN DIERVILLA LONICERA (CAPRIFOLIACEAE)
Authors: THOMSON JAMES D. , ANDREWS BRENDA J. , PLOWRIGHT R. C. 
Published: May 2006

SummaryWhen pollen from Hieracium floribundum Wimmer and Grab. (Compositae) was applied to stigmas of Diervilla lonicera Mill. (Caprifoliaceae) in mixtures with Diervilla pollen, Diervilla fecundity was strongly depressed. While this phenomenon is unlikely to be of importance to Diervilla under field conditions, this property of Hieracium pollen may have stronger effects on other ecological associates. The only other reported instance of inhibitory pollen is from Parthenium hysterophorus L., which, like Hieracium, has allelopathic properties.
PERTURBATION OF PHOSPHOLIPID MEMBRANES BY GIBBERELLINS
Authors: PAULS K. P. , CHAMBERS J. A. , DUMBROFF E. B. , THOMPSON J. E. 
Published: May 2006

SUMMARYDifferential scanning calorimetry and electron spin resonance have been used to characterize the association of gibberellic acid4 and gibberellic acid, (a GA4/GA7 mixture) with phospholipid membranes. The GA4/GA7 mixture lowered the temperature and reduced the co‐operativity of the main phase transition of liposomes prepared from dipalmitoylphosphatidylcholine (DPPC), distearylphosphatidylcholine (DSPC) and dipalmitoylphosphatidylglycerol (DPPG), and eliminated the pretransition. The reduction in co‐operativity of the main transition was not accompanied by a reduction in transition enthalpy, indicating that the gibberellins simply perturb the bilayer rather than complex with the phospholipid molecules. Perturbation was markedly greater at pH values approaching the pKa of the gibberellin carboxyl group than at pH 7. Moreover, the negatively charged DPPG was less susceptible to perturbation than the zwitterionic phosphatidylcholines. Perturbation by GA8, a physiologically inert gibberellin, was virtually imperceptible. Electron spin resonance of GA4/GA7‐treated liposomes of phosphatidylcholine (PC) and phosphatidylglycerol (PG) confirmed the results obtained by differential scanning calorimetry and also indicated that the gibberellins associate with the surface of the phospholipid membranes rather than penetrate into the interior of the bilayer. The data are consistent with the proposal that gibberellins can influence membrane behaviour by modulating the physical properties of the lipid bilayer.
PLANT‐INDUCED CHANGES IN THE RHIZOSPHERE OF RAPE (BRASSICA NAPUS VAR. EMERALD) SEEDLINGS
Authors: GRINSTED M. J. , HEDLEY M. J. , WHITE R. E. , NYE P. H. 
Published: May 2006

SUMMARYRape (Brassica napus, var. Emerald) plants were grown in thin layers of a phosphate‐deficient soil supplied with a P‐free nutrient solution containing N solely as NO3− (3.5 × 10−3 M). Inter‐root competition (excluding root hairs) for soil P began on the 14th day of growth, after which all soil in the thin layer was considered to be rhizosphere soil. During subsequent plant growth the pH in the rhizosphere decreased as much as 2.4 units (from pH 6.5 to 4.1) before rising slightly towards the end of the experiment (35th day). The pH decrease was associated with an increase in solution P concentration in the depleted rhizosphere soils, compared to the P concentration attained when similar amounts of P were desorbed from unplanted control soils by shaking them in 10−2 M Ca(NO3)2 at the original soil pH of 6.1. P desorption in 10−2 M Ca(NO3)2 at pH values between 6.2 and 4.5 indicated that a decrease in the soil pH from 6.5 to 4.1 could result in at least a 10‐fold increase in the P released into solution, which would be available for plant uptake. These results may explain reports in the literature that rape is efficient in absorbing P from P‐deficient soils.
DEVELOPMENT OF EXTERNAL HYPHAE BY DIFFERENT ISOLATES OF MYCORRHIZAL GLOMUS SPP. IN RELATION TO ROOT COLONIZATION AND GROWTH OF TROYER CITRANGE
Authors: GRAHAM J. H. , LINDERMAN R. G. , MENGE J. A. 
Published: May 2006

SUMMARYThe hypothesis was tested that the amount of external hyphae of a vesicular‐arbuscular mycorrhizal (VAM) fungus extending from roots out into soil is not always proportional to the extent of colonization of the root cortex. Growth enhancement and amount of external hyphae were compared for eight isolates of five Glomus spp. that differed in their geographic origin and capacity to enhance growth of Troyer citrange, but were similar in their capacity to extensively colonize Troyer citrange roots. In general, isolates from California increased growth in a P‐deficient (9.8 mg kg−1) California soil more than did non‐native isolates from Florida soils. The difference between the capacity of California and Florida isolates to enhance growth was not a function of the degree to which they colonized the roots since all had colonized over 95% of the root length by the time of harvest. Differences in growth enhancement did appear, however, to be a function of the amount of external hyphae that had developed as estimated by the weight of soil they had bound into aggregates. This study suggests that isolates of VA mycorrhizal fungi may differ in their capacity to develop an external hyphal system independent of their capacity to colonize the root cortex, and that we cannot assume that high levels of colonization will necessarily mean the fungus has also developed the mycelium in the soil necessary to transport nutrients responsible for plant growth enhancement.