bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPARATIVE PHYSIOLOGY OF ALBUGO TRAGOPOGONIS‐INFECTED AND PUCCINIA LAGENOPHORAE‐INEECTED PLANTS OF SENECIO SQUALIDUS L.
Authors: WHIPPS J. M. , COOKE R. C. 
Published: May 2006

SUMMARYInfections of Senecio squalidus leaves by Puccinia lagenophorae (Uredinales) were characterized by polyol synthesis, development of green islands and deposition of starch within green island tissues. In infections by Albugo tragopogonis (Peronosporales), there was no polyol synthesis, comparable green islands did not develop or developed poorly, and there was extensive and progressive necrosis of host tissues in infected areas. No starch was deposited in infected tissues and there was gradual disappearance of all starch from infected leaves. In both kinds of infection, ethanol‐soluble metabolites accumulated around infected sites but there was no evidence for massive translocation to these sites from the rest of the leaf or plant. The differences between these two kinds of infection are discussed in relation to the biology of biotrophic, pathogenic higher and lower fungi. It is suggested that many lower fungi that infect leaves are hemibiotrophic rather than biotrophic.
THE UPTAKE OF ZINC AND CALCIUM FROM SOLUTION CULTURE BY ZINC‐TOLERANT AND NON‐TOLERANT SILENE MARITIMA WITH. IN RELATION TO CALCIUM SUPPLY
Authors: BAKER A. J. M. 
Published: May 2006

SUMMARYInter‐population variation in the uptake of calcium from solution culture was studied in a range of zinc‐tolerant and non‐tolerant populations of Silene maritima under conditions of high zinc and calcium. The populations exhibited great variability in their patterns of calcium uptake similar to that previously reported for zinc. The effects of variation in calcium supply on yield and calcium and zinc uptake by one zinc‐tolerant and one non‐tolerant population are described. Little difference in yield‐response to calcium was detected between the two populations but they showed major differences in the uptake and accumulation of zinc and calcium and their transport from root to shoot. Total zinc uptake was little affected by increases in calcium level in the tolerant plants but was decreased significantly in the non‐tolerant plants. At the higher calcium levels, total zinc uptake by tolerant plants was also significantly greater than by the non‐tolerant but the populations did not differ in total calcium uptake. Evidence for a reduction in zinc transport in both populations resulting from increased calcium uptake is presented. Marked stimulation of zinc accumulation by the roots of the tolerant population resulting from increases in the external calcium level is interpreted as a possible corollary of zinc tolerance in this tolerant population. The role of calcium in the internal detoxification of zinc is discussed.
ZINC‐PHOSPHORUS INTERACTIONS IN A ZINC‐TOLERANT AND A NON‐TOLERANT POPULATION OF SILENE MARITIMA WITH.
Authors: BAKER A. J. M. 
Published: May 2006

SUMMARYInter‐population variation in the long‐term uptake of phosphorus from solution culture indicated that uptake and transport in some zinc‐tolerant populations of Silene maritima were greater than in non‐tolerant coastal and arctic‐alpine populations. The effects of P and Zn level in the culture solution on yield and uptake of P and Zn by plants of a zinc‐tolerant population exhibiting extreme uptake characteristics and of a non‐tolerant population are described. The tolerant plants were higher‐yielding at low P levels, showed less phosphate response and proved to be more efficient in their P uptake and transport than the non‐tolerant plants. A differential interaction of Zn and P was also detected in the two populations. These features were considered to be of adaptive significance.
THE EFFECTS OF SOWING DENSITY, SALINITY AND SUBSTRATE UPON THE GERMINATION OF SEEDS OF PLANTAGO CORONOPUS L.
Authors: WAITE STEPHEN , HUTCHINGS MICHAEL J. 
Published: May 2006

SUMMARYThe influence of number of seeds per clump upon germination of Plantago coronopus L. was investigated at different salinity levels on filter paper, sand and soil. These substrates provide both artificial and semi‐natural microenvironments for seed germination.On all substrates, germination was positively dependent on clump density and seeds in clumps had a higher tolerance of salinity as reflected in higher germination percentages. Final percentage germination for a given clump size and salinity level depended upon substrate, being far higher on filter paper and sand than on soil, whilst the time required to reach final germination also increased in that order. The possible ecological significance of density‐dependent seed germination is discussed.
RE‐ORGANIZATION OF FINE STRUCTURE DURING REHYDRATION OF DESICCATED LEAVES OF XEROPHYTA VILLOSA
Authors: HALLAM N. D. , GAFF D. F. 
Published: May 2006

SUMMARYAir‐dry viable leaves of Xerophyta villosa, fixed in non‐aqueous fixatives, show disorganization of the cytoplasm and loss of cristae, grana and thylakoids, but retention of intact double membranes around plastids and of intact nuclei. Some reorganization of cell fine structure takes place while the leaves are rehydrating: cristae reappear in the mitochondria and numerous spherical vesicles in the plastids first swell, flatten to discs, and associate at their rims to form the thylakoid system and, following full rehydration, grana. Reformation of starch grains in the rehydrated tissue appears to precede the renewal of net photosynthesis.
A PLOTTER FOR PLANT POPULATION STUDIES
Authors: CULLEN J. M. , WEISS P. W. , WEARNE G. R. 
Published: May 2006

SUMMARYA simple plotter utilizing rectangular coordinates is described for use in following populations of known individual plants over periods of time. Each plant is positioned by two coordinates determined by reference to a metal bar and a shorter arm, each graduated in mm and held at right angles to each other in the horizontal plane. The arm moves along the bar and is adjustable for height. The bar rotates about its longitudinal axis thus allowing the arm to swing to an upright position to avoid vertical obstructions. The plotter copes readily with tall vegetation and difficult terrain, is easily transported and installed, and has been used successfully to plot individual plants of Chondrilla juncea L. and Emex australis Steinh.
THE PALAEOBOTANY OF INTERGLACIAL DEPOSITS AT SUGWORTH, BERKSHIRE
Authors: GIBBARD P. L. , PETTIT M. 
Published: May 2006

SUMMARYInterglacial deposits in a river channel‐fill sequence at Sugworth, Oxfordshire contain a rich flora indicating a late Cromerian (Cr IIIb) age. Analyses of pollen and macroscopic plant remains indicate uniform vegetational conditions throughout the period of deposition, with mixed deciduous‐coniferous woodland in the valley, and alder fen carr bordering the river. On the immediate floodplain and point bar the various wet areas supported several herb communities. New interglacial records for several plant taxa are discussed, in particular Cyperus michelianus and C. fuscus.
PRESENCE OF 14C ACTIVITY IN ROOT EXUDATES AND GUTTATION FLUID FROM AGROPYRON REPENS TREATED WITH 14C‐LABELLED GLYPHOSATE
Authors: COUPLAND D. , CASELEY J. C. 
Published: May 2006

SummaryThe herbicide, N‐phosphonomethyl glycine (glyphosate), is readily absorbed by the foliage and translocated in the phloem of Agropyron repent (L.) Beauv. The roots and rhizomes were active sinks and, 8 days following herbicide treatment, 14C accumulated at the rhizome nodes, especially at the apical buds. Appreciable amounts of [14C]glyphosate were exuded from intact roots into surrounding solutions but very low levels occurred in the guttation drops collected from the leaf tips. Some implications of the work are discussed.
SALT‐INDUCED LOSS OF POTASSIUM FROM PLANT ROOTS
Authors: NASSERY H. 
Published: May 2006

SummaryThe loss of K+ from excised barley, wheat, chick pea and bean roots was measured in the absence or presence of different concentrations of NaCl and mannitol. In the presence of 50 mM Ca2+, the threshhold NaCl concentration for induction of K+ loss was 160 mM for barley, wheat and chick pea and 140 mm for bean. Mannitol iso‐osmotic to 160 mM NaCl did not induce K+ loss from barley, wheat or chick pea roots indicating that the induction of K+ loss was a salt‐induced and not an osmotic injury. The preventive effect of various concentrations of CaCl2 and MgCl2 on salt‐induced K+loss indicated that the protective effect of Ca2+was specific. Although 50 mM Ca8+ was sufficient, concentrations up to 40 mM may be more effective. The measurement of salt‐induced K+ loss appears to be a quick and reliable method of estimating the degree of salt resistance in plants.
SEASONAL AND EDAPHIC VARIATION IN VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION OF GRASSES BY GLOMUS TENUIS
Authors: RABATIN SUSAN C. 
Published: May 2006

SummarySeasonal differences in percentage length of gramineous host root infected with Glomus tennis were measured in three field sites in Pennsylvania, U.S.A. Highest G. tennis infection levels were generally found in the spring in very phosphorus‐deficient soils low in moisture. In roots sampled from soils with a high spring soil‐moisture content, fine endophyte infection increased to a maximum later in the growing season. A higher percentage frequency of fine endophyte infection on fine grass feeder roots in spring is taken as evidence for the hypothesis that G. tenuis is a vesicular–arbuscular mycorrhizal fungus particularly adapted to penetrating host roots during brief seasonal fluxes of phosphorus availability. The implications of these data are discussed in relation to mechanisms in grasses which adapt them to nutrient stress.
EFFECT OF WATER STRESS ON PHOSPHORUS UPTAKE BY MYCORRHIZAS OF PINUS RADIATA
Authors: REID C. P. P. , BOWEN G. D. 
Published: May 2006

SummaryThe uptake of 32P by excised non‐mycorrhizal and mycorrhizal roots of Pinus radiata was examined in solutions adjusted with polyethylene glycol 4000 to water potentials of 0, 005, 01, 0.3, 0.6 and 1.2 negative MPa. Solutions contained 5 μm KH2PO4 and 0.5 mM CaSO4. Uptake of phosphate was little affected by water potential in either mycorrhizal or non‐mycorrhizal roots. Changes in water potential also caused no appreciable change in its efflux from mycorrhizal roots, suggesting little effect on permeability to phosphate. Uptake of phosphate, when based on surface area of the roots, was similar for both mycorrhizal and non‐mycorrhizal roots, but was less for non‐mycorrhizal roots when based on fresh wt.It is thus considered that changes in soil water potential per se may have little impact on absorption processes by mycorrhizal and non‐mycorrhizal roots. However, effective penetration of soil by mycelial strands and hyphae from ectomycorrhizas may be important in offsetting lowered transfer of ions to roots under low soil moisture conditions.
TOLERANCE OF ANDROPOGON SCOPARIUS TO COPPER AND ZINC
Authors: EHINGER L. H. , PARKER G. R. 
Published: May 2006

SummaryThe glass, Andropogon scoparius, from two sites in northwestern Indiana was tested hydro‐ponically for tolerance to zinc and copper. Plants from both sites showed a continuum of response to zinc, spanning the range of inhibition to enhancement of root growth. The urban plants were unaffected by 0.025 p.p.m. copper, whereas the rural plants were adversely affected at this level. The rural plants exhibited greater root growth than the urban plants at 0.1 p.p.m. copper. At 0.025 and 0.05 p.p.m. copper, the urban plants exhibited the greater root growth. At 0.075 and 0.l p.p.m. copper, the plants from both sites exhibited the same root growth. It was concluded that the urban site plants possess tolerance to low (0.025 p.p.m.) copper levels.
THE ROLE OF METAL‐ION BINDING IN MODIFYING THE TOXIC EFFECTS OF SULPHUR DIOXIDE ON THE LICHEN UMBILICARIA MUHLENBERGII
Authors: NIEBOER E. , RICHARDSON D. H. S. , LAVOIE P. , PADOVAN D. 
Published: May 2006

SummaryK+ efflux from Umbilicaria muhlenbergii was not affected following the uptake of known amounts (< 20 μmol g‐1) of Ca2+, Mg2+, Sr2+ and Zn2+, but was increased in the cases of Cu2+ and Pb2+. In a number of samples that had taken up increasing amounts of Cu2+, a discontinuity in K+ release during metal incubation correlated with a decrease in subsequent 14C fixation. Some of the binding sites associated with the first phase of Cu2+ uptake (up to 12 μmol g‐1) are interpreted to occur near, on or within the algal cells. The larger K+ loss associated with higher Cu2+ uptake levels indicated that a component of the second Cu2+ uptake phase involved binding at or penetration of the fungal membranes. The uptake of Sr2+, Ni2+ and Zn2+ conferred some protection to samples subsequently exposed to 75 p.p.m. aqueous SO2 for 1 h, while Mg2+, and Ca2+ had no effect. The combined effects of Cu2+ uptake and SOS exposure (and also Pb2+ and SO8) were approximately cumulative. Finally, the results are explained by reference to a classification that separates metal ions into three chemically and biologically significant categories. It is concluded that class A metal ions (those with a preference for ionic interactions) and borderline metal ions with class A character tend to protect lichens against SO2 damage, while borderline metal ions with class B character (a preference for covalent interactions) have the opposite effect.
THE ROLE OF METAL‐ION BINDING IN MODIFYING THE TOXIC EFFECTS OF SULPHUR DIOXIDE ON THE LICHEN UMBILICARIA MUHLENBERGII
Authors: RICHARDSON D. H. S. , NIEBOER E. , LAVOIE P. , PADOVAN D. 
Published: May 2006

SummaryTotal 14C fixation in Umbilicaria muhlenbergii was not significantly affected at levels near the capacity of the first binding site (c. 12 μmol g‐1) of class A metal ions or borderline metal ions with class A characteristics: i.e. Sr2+, Mg2+, Ca2+, Ni2+, and Zn2+. Although both Cu2+ and Pb2+ are borderline ions with significant class B character, only Cu2+ greatly reduced fixation. However Ni2+ and Pb2+, as well as Cu2+, induced increased photosynthate release from lichen samples. Protection against damage due to SO2 exposure was rendered by the uptake of class A ions and even borderline ions except those normally accumulated intracellularly (Mg2+, Zn2+) or possessing the capacity to penetrate cells readily (Cu2+). Of the borderline ions tested, Pb2+, Cu2+ and Ni2+, as well as SO2, induced changes resulting in the incorporation of less 14C into ribitol and more into sucrose and other sugars during photosynthesis by the lichen samples. The presence of the class A ion Ca2+ caused a shift in the opposite direction. The presence of Ca2+, Ni2+, Pb2+, but not Cu2+, on the lichen tended to inhibit the large SO2‐induced shift away from ribitol production. The threshold levels of various metals reported from field studies to result in visible damage are discussed in terms of the observed photosynthetic perturbations, K2+ leakage and factors determining metal uptake by lichens. Finally, the ecological significance of the ability of Ca2+ to protect lichens against the damaging effects of air pollution is discussed.
PATHWAYS OF PLASTID DIFFERENTIATION IN SPIRODELA OLIGORRHIZA
Authors: PORATH D. 
Published: May 2006

SummaryIn light‐grown Spirodela oligorrhiza, a duckweed, chloroplasts complete differentiation in 2·5 days. When young green fronds are transferred to the dark, their plastids undergo ultrastructural changes that are retrogressive. Prolamellar bodies appear in the intergranal spaces within 12 to 18 h, while well‐developed amyloplasts can be seen after 11 days. Mature green fronds maintained in the dark for up to 3 months remain unchanged. The results are discussed in the context of monotropic and reversible pathways of plastid differentiation in higher plants.
CELL DOUBLING TIME IN THE APICAL MM OF ELONGATING LATERAL ROOTS OF VICIA FABA L.
Authors: THOMPSON A. , MacLEOD R. D. 
Published: May 2006

SummaryCell doubling time was determined in several ways in the apical mm of newly emerged, 0·2, 1 and 4 cm long lateral roots of Vicia faba L. and in every case it tended to decrease with increase in root length. Similar values were obtained in the roots of each length investigated when cell doubling time was calculated from the rate of passage of cells into the period of DNA synthesis (S) in both control and colchicine treated roots and from the rate of accumulation of cells in metaphase in the presence of colchicine, assuming cell number increased exponentially, i.e. colchicine had not affected the rate of entry of cells into mitosis or S during the 3 to 6 h period over which measurements were taken. A discrepancy was found, however, between the values determined for cell doubling time obtained from these rates and those calculated on the basis of the method devised by Evans and his co‐workers (Evans, Neary and Tonkinson, 1957). Possible reasons for such a discrepancy are discussed.
THE EFFECTS OF AIR POLLUTION ON PLANT GROWTH WITH SPECIAL REFERENCE TO SULPHUR DIOXIDE. III. GROWTH STUDIES WITH LOLIUM MULTIFLORUM LAM. AND DACTYLIS GLOMERATA L.
Authors: CRITTENDEN P. D. , READ D. J. 
Published: May 2006

Summary Lolium multiflorum cv. S22 and Dactylis glomerata cv. S143 were grown in a sealed glass chamber, force‐ventilated with ambient SO2‐polluted air and the yields compared with those of control plants grown in a second chamber receiving filtered air, free of SO2 and particulates. Shoot dry weight of both species was reduced by 30 to 40 % after 8 to 10 weeks in unfiltered air containing mean SO2 concentrations of 50 to 90 μg m−3, growth reductions being readily detectable after 3 weeks from transplanting seedlings to the chambers. The productivity of L. multiflorum was only marginally depressed (c. 10 %) by late summer SO2 levels in the range 10 to 50 μg m−3. It is suggested that grass plants may be particularly susceptible to SO2 pollution during the early growth phase following germination when aerodynamic resistance is low and relative growth rate maximal. The possibility that environmental factors other than SO2 pollution contributed to the inhibitory effect of the unfiltered air treatment is discussed.
TOLERANCE AND TOXICITY OF COBALT, COPPER, NICKEL AND ZINC IN CLONES OF AGROSTIS GIGANTEA
Authors: HOGAN GARY D. , RAUSER WILFRIED E. 
Published: May 2006

SummaryThree clones of Agrostis gigantea were evaluated for their tolerance to cobalt, copper, nickel and zinc. Of the clones originating from a mine waste site in Sudbury, Ontario, one showed tolerance to copper, cobalt, and nickel, the other only to nickel. Neither of these clones showed tolerance to zinc. A clone from a seed supply house lacked tolerance to any of the metals tested. Copper was most toxic to A. gigantea, followed by nickel, cobalt and zinc.
THE BIOLOGY OF AMBROSIA TRIFIDA L.
Authors: Abul‐Fatih H. A. , Bazzaz F. A. 
Published: May 2006

Summary Ambrosia trifida L. is an annual plant found in repeatedly disturbed ground in the midwestern and eastern United States. When present, it dominates the community, producing most of the plant biomass and suppressing all associated species. When A. trifida was selectively removed in field plots early in the growing season, the biomass of the remaining species, their density and species diversity increased but the biomass of the community decreased. With A. trifida the total standing above‐ground plant biomass of the other species was 43.7 gm‐2, their density was 86 plants m−2 and the species diversity was 0.21. Without A. trifida the corresponding values were 666 g m −2, 584 plants m−2, and 1.64. Total above‐ground biomass of the community was 1640 with and 666g m−2 without A. trifida. Ambrosia trifida produced 97 % of the plant biomass. The negative correlation between biomass and diversity was undoubtedly caused by the strong dominance and high production of A. trifida. This species may be considered an ‘organizer’ or ‘keystone’ species which controls the properties of some annual communities in disturbed ground.
THE BIOLOGY OF AMBROSIA TRIFIDA L.
Authors: ABUL‐FATIH H. A. , BAZZAZ F. A. , HUNT R. 
Published: May 2006

Summary Ambrosia trifida plants were grown in monocultures in the field at five densities ranging from 4 to 500 plants m−2. Plant growth, productivity, biomass allocation, plant architecture, and seed predation were studied in repeated harvests. Plant growth was very plastic and the weight of individual plants was greatly influenced by density. Mean dry weight per plant varied from 11 g in the highest density to 320 g in the lowest density. At the final harvest in September the plants had lost up to 34% of their biomass through senescence of lower leaves. Above ground biomass production was extremely high and averaged from 1590 g m−2 in the lowest density to 3058 g m−2 in the highest density. Leaf area index was very high especially at high densities.The relationship between plant height and density was complex and some individuals in the intermediate density were more than 3 m tall. Reproductive ratios, the weight of reproductive materials/shoot biomass, generally declined with increasing density and were significantly higher when the weight of the male flowers was added to the weight of seed. With time a pronounced decline in leaf area ratio occurred in all densities. There was no significant effect of density on unit leaf rate. The plants were able to discard their lower unproductive leaves in dense plots and effectively raised their canopy further up the stem. But this left much unproductive stem structure below and leaf area ratio and relative growth rate declined. Plants in high densities were single stemmed while those in the lowest density were much branched.The presence in dense stands of tall and short plants created a bimodal distribution of leaf area and seed weight. Most seed biomass was located in the upper canopy of low density plants. The percentage of plants producing male flowers decreased with increasing density and, in the highest density, with decreasing height in the canopy. The shorter plants, without male flowers, had a higher reproductive ratio. They invested their reproductive energy into seed. Insects damaged many seeds and the percentage of damaged seeds per plant declined with increasing density. Furthermore in the population of highest density seed predation was higher in the ‘apparent’ tall plants than in less apparent short plants.