bluuebunny/crossref_metadata_2025_split huggingface dataset:
STUDIES OF CAVITATION IN ISOLATED VASCULAR BUNDLES AND WHOLE LEAVES OF PLANTAGO MAJOR L.
Authors: MILBURN JOHN A. , McLAUGHLIN MARGARET E. 
Published: May 2006

SummaryCavitation has been studied by acoustic detection in preserved and fresh vascular bundles and in whole leaves of Plantago and other plants. ‘Clicks’, indicating cavitation vibrations, were produced as vascular bundles lost water in a manner similar to that of Ricinus leaves (Milburn, 1973a), but the process was more rapid and freely suspended bundles jerked as they cavitated, like spore elator systems. Clicks were counted in a semi‐quantitative study of both cavitation and the reverse process, the restoration of water‐filled xylem conduits. Restoration was greatly enhanced by compression or vacuum infiltration treatments in comparison with simple soaking: apparently gas entrainment is the major obstacle preventing refilling.Cavitation within wilting leaves was much less extensive than when isolated bundles are dried, indicating that cavitation is generally incomplete under natural conditions. Xylem sap tensions at which cavitation is incipient were estimated approximately by balancing cavitation against the external humidity. Sap tensions at incipient cavitation could be measured more accurately using a pressure bomb, however. These tensions were surprisingly low, covering a range of tensions (5‐15 bar) expected to occur under field conditions. Cavitation was detected in Plantago under natural field conditions and in other plants also, especially Tussilago, Further implications are discussed.
QUANTITATIVE DETERMINATION OF STARCH AND GLYCOGEN AND THEIR METABOLISM IN LEAVES OF TUSSILAGO FARFARA DURING INFECTION BY PUCCINI A POARUM
Authors: HOLLIGAN P. M. , McGEE E. E. M. , LEWIS D. H. 
Published: May 2006

SummaryMethods for the differential extraction of starch and glycogen from rust‐infected leaf tissue and their assay using amyloglucosidase and glucose oxidase are described. In rusted leaves of Tussilago, the low starch levels show a typical diurnal variation whereas there is continued synthesis of glycogen by the fungus in the dark.
ULTRASTRUCTURE OF THE HOST‐FUNGUS INTERFACE IN A VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: COX GUY , SANDERS FRANCIS 
Published: May 2006

SummaryAn ultrastructural study was made of the vesicular‐arbuscular mycorrhiza formed by Endogone (Glomus) mosseae with roots of Allium cepa. The fungal arbuscules consist of highly branched hyphae that have a characteristic reticulate vacuolation. The host plasmalemma surrounds the individual branches of the arbuscule. Around the penetration point and the trunk of the arbuscule a collar of wall material lies between the host plasmalemma and the fungal wall. This layer is absent from the branches. When the arbuscule senesces, the branches collapse and the empty fungal walls aggregate into a clump. Within the clump the fungal walls appear to fragment and disintegrate. The host plasmalemma at this stage surrounds the clump as a whole. When an entire infection becomes senescent, a thick layer of wall material apparently derived from the host encases all intracellular fungal structures.
THYMIDINE AND THE MEASUREMENT OF RATES OF MITOSIS IN MERISTEMS
Authors: de la TORRE C. , CLOWES F. A. L. 
Published: May 2006

SummaryA series of pulses of [3H]thymidine was used to measure cell flow through the mitotic cycle in four regions of the root meristem of Zea. For comparison, colchicine was used to measure cell flow after the supply of pulses of non‐radioactive thymidine. Thymidine itself does not, at normal labelling concentrations, disrupt the pattern of cell proliferation within the meristem although it does so in other circumstances. [3H]thymidine, in contrast, does, at labelling concentrations, change the behaviour of the meristem, lengthening cell cycles in the regions normally with rapid cell division and accelerating cell cycles in the quiescent centre. The significance of this disruption is discussed in relation to the use of thymidine in investigating the cell kinetics of meristems.
BRANCHING IN PACHYCAUL SENECIOS: THE DURIAN THEORY AND THE EVOLUTION OF ANGIOSPERMOUS TREES AND HERBS
Authors: MABBERLEY D. J. 
Published: May 2006

SummaryThe giant groundsels (Senecio L. subg. Dendrosenecio [Haum. ex]Hedb.) are tropical branching pachycaul trees in a predominantly temperate herbaceous group. Other pachycaul Senecio spp. of Africa with dendrosenecio‐branching are related to tropical herbs, shrubs and lianes; the pachycaul cabbage‐trees of St Helena include the he‐cabbage tree with dendrosenecio‐branching. It is postulated that the pachycaul tree with dendrosenecio‐branching is the primitive condition for at least some alliances in the Senecioneae. The hypothesis is tested by reviewing the taxonomic distribution of the pachycaul trees with such branching in Senecioneae throughout the world and its usefulness by a consideration of the origin of herbs and trees in the Compositae.
PHOSPHATE TRANSPORT IN HYDRODICTYON AFRICANUM
Authors: Raven J. A. 
Published: May 2006

SUMMARYThe transport and distribution of phosphate in Hydrodictyon africanum is reported, and discussed in relation to phosphate transport in other green algae and chloride transport in Hydrodictyon. The inorganic phosphate concentration in both vacuole and cytoplasm is 1–2 mM; the cytoplasm also contains 35 mM of phosphate as organic and polyphosphate, which are absent from the vacuole. Phosphate influx from 0.1 mM phosphate at pH 6.5 was much greater than the efflux, and was more stimulated by light and inhibited by low temperature than was the efflux. The phosphate influx is, on electrochemical criteria, active. The influx at the tonoplast was much higher than that at the plasmalemma. Na stimulated phosphate influx more than did K, in agreement with results for other green algae but in contrast to monovalent cation effects on active Cl influx. Both phosphate and chloride influxes show a simple hyperbolic relationship between anion concentration and influx, in the concentration range tested, but the kinetics for the two ions show different responses to changes in irradiance and Na concentration. pH effects on the influxes are also reported. The passive permeability of the plasmalemma to H2PO‐4 is similar to that to Cl‐.
THE ACTION OF FUSICOCCIN ON STOMATAL GUARD CELLS AND SUBSIDIARY CELLS
Authors: SQUIRE G. R. , MANSFIELD T. A. 
Published: May 2006

SUMMARYThe fungal toxin, fusicoccin, induces wilting when applied to uninfected plant material. We have confirmed that fusicoccin stimulates stomatal opening and the entry of potassium into the guard cells. When detached epidermis of Commelina communis is placed in a potassium‐free medium containing 10 μM fusicoccin, the stomata open widely and potassium accumulates in the guard cells, demonstrating that sufficient endogenous potassium is available.The failure of stomata to open on isolated epidermis is discussed. It is suggested that the subsidiary cells respond to a wound hormone produced after stripping off the epidermis, the effect of which is to block the normal route taken by potassium as it moves into the guard cells. A physiological role for the subsidiary cells in regulating stomatal movements is thus strongly indicated.Fusicoccin is able to overcome the effect of those environmental factors, darkness and high CO2 concentrations, which normally inhibit stomatal opening. Evidence is presented that, in this case, it must act within the guard cells and not only on the subsidiary cells. The time of exposure to the toxin required for a subsequent opening response of the stomata is very short. Stomata in contact with 10 μM fusicoccin for 1 min open almost as widely as those exposed to the same concentration for 2 h.
REGENERATION IN ROOT CUTTINGS IN TARAXACUM OFFICINALE II. EFFECTS OF EXOGENOUS HORMONES ON ROOT SEGMENTS AND ROOT CALLUS CULTURES
Authors: BOOTH A. , SATCHUTHANANTHAVALE R. 
Published: May 2006

SUMMARYIn long root cuttings of Taraxacum, the regeneration of shoots was promoted by kinetin and the regeneration of roots by IAA, each hormone reversing the normal polarity of regeneration when applied at high concentrations. However, IAA stimulated shoot regeneration and kinetin root regeneration when used at low concentrations. A callus culture, derived from Taraxacum root, required both auxin and cytokinin for growth. At a given level of cytokinin, callus regenerated shoots when the auxin level was low and roots when it was high. A cytokinin from Taraxacum roots promoted callus growth and shoot regeneration in both callus and short root cuttings. Gibberellic acid had no stimulatory effect on organogenesis in either root cuttings or callus cultures.
RESPONSE OF SEEDLINGS OF PINUS CONTORTA AND PICEA SITCHENSIS TO OXYGEN CONCENTRATION IN CULTURE SOLUTION
Authors: BOGGIE ROBERT 
Published: May 2006

SUMMARYSeedlings of Pinus contorta and Picea sitchensis were grown in culture solutions flushed with gas mixtures containing 0–21% oxygen. Pinus contorta was more tolerant of an oxygen‐deficient root environment than Picea sitchensis. When the oxygen tension was lower than in solutions flushed with air, the growth of both species was impaired. Growth of Pinus contorta was severely restricted below 5% O2 but some growth was measurable even in a non‐aerated solution; growth of Picea sitchensis was severely restricted below 10% O2 and no root growth was discernible at 3% O2 or less. Over the 12‐week periods of the experiments shoot extension occurred in all treatments, but was not so clearly correlated with the oxygen concentration around the roots as was root growth.
MOVEMENT OF 14CARBON FROM HOST TO FUNGUS IN ORCHID MYCORRHIZA
Authors: HADLEY G. , PURVES S. 
Published: May 2006

SUMMARYUninfected plantlets of Goodyera repens and plantlets infected with the endophyte Rhizoctonia goodyerae‐repentis were fed with 14CO2. Quantities of 14C fixed varied greatly between individuals, but there was a consistent pattern of distribution of label which remained unaltered over four weeks. Very little 14C moved to the rhizomes. The endophytic fungus readily grew from infected plantlets on to Pfeffer agar and small amounts of radioactivity were found in the mycelium growing from previously fed plantlets. 14C leakage from uninfected plantlets was negligible, although low levels of radioactivity occurred in serial washings from them. When the tops alone of infected plants were fed with 14CO2, no radioactivity could be detected in the emerging fungal mycelium. Where rhizomes alone were exposed, small quantities of 14C were detected in the growing mycelium. The fungus readily translocated 14C from the remains of dead protocorms. It appears that R. goodyerae‐repentis does not freely utilize recent photosynthate from its host under the conditions of these experiments.
THE CONTROL OF CATION LEVELS IN SEASHORE AND INLAND MOSSES
Authors: BATES J. W. , BROWN D. H. 
Published: May 2006

SUMMARYAfter immersion of seashore and inland mosses in artificial seawater, their extracellular, exchangeable and intracellular cations were analysed. Levels of extracellular and exchangeable Na and Mg in both inland and seashore mosses increase. In the intracellular fraction of inland species there was a rapid loss of K and an accompanying net uptake of Na by a slower, possibly active, process. K loss from inland mosses occurred in seawater concentrations exceeding 50% whereas seashore species withstood concentrations of seawater up to 200% with little change.Treatment of the seashore moss, Grimmia maritima, with NaCl at the concentration in seawater produced almost complete loss of intracellular K. This effect was greatly alleviated by Ca, partially by Mg and was nullified when Na was accompanied by both Ca and K. When Grimmia spp. were supplied with seawater solutions containing a range of Ca concentrations, G. pulvinata showed stimulation of net uptake of Na and reduced net loss of K with increasing Ca concentration whereas G. maritima showed inhibition of net uptake of Na and increased net uptake of K. The ability of seashore mosses to withstand immersion in seawater without undergoing large changes in intracellular cation content may reflect greater K specificity of the monovalent cation uptake carriers than in the inland species studied.
EXISTENCE OF SALT GLANDS IN VARIOUS GENERA OF THE GRAMINEAE
Authors: LIPHSCHITZ NILI , WAISEL Y. 
Published: May 2006

SUMMARYSalt glands were observed in twenty‐five species belonging to the Chlorideae, Sporoboleae and Aeluropodeae tribes of the Gramineae. Most of those species are presently glycophytes, and the possession of salt glands suggests that they had a common halophytic ancestor.
SURFACE POLLEN STUDIES ACROSS A WOODLAND/HEATH TRANSITION AND THEIR APPLICATION TO THE INTERPRETATION OF POLLEN DIAGRAMS
Authors: TINSLEY HEATHER M. , SMITH RICHARD T. 
Published: May 2006

SUMMARYPollen analysis has been carried out on surface moss polsters from oak woodland and moorland communities in West Yorkshire, and the results have been compared with the composition of the surrounding vegetation. In general, the pollen specta reflected the adjacent plant communities well, but certain marked anomalies have been observed. The deposition of Alnus and Corylus pollen in particular appeared to be erratic, and certain of the non‐arboreal pollen types such as Rumex, the Rubiaceae and the spores, had a markedly peaked distribution. Vaccinium, an important member of the woodland and moorland plant communities, was scarcely represented in the surface samples.The distribution of arboreal pollen at increasing distances from the woodland edge has been examined by analysing polsters collected along three transect lines. A very rapid decline in arboreal pollen within 100 m of the woodland edge was observed in each case.The application of these results to the ecological interpretation of pollen diagrams is considered.
A COMPARISON OF FOUR ABSOLUTE POLLEN PREPARATION TECHNIQUES
Authors: PECK RONA M. 
Published: May 2006

SUMMARYLaboratory tests were made on three absolute pollen preparation techniques previously published by Davis (1965, 1966), Matthews (1969) and Jørgensen (1967), and on an additional weighing method (Modified Jørgensen) using both standard pollen suspensions and fossil minerogenic samples. Laboratory procedure is described and the following results include an investigation of grain distribution within slides prepared by the Jørgensen and Matthews methods, a discussion of the statistical reliability of the Jørgensen method, and a test of the variability attributable to preparation methods, using the coefficient of variation (C.V.) as the basis of comparision. The relation between grain loss (bias) during the preparation procedure, the methods employed, and the sediment type used is explored, and some practical aspects of the various techniques are considered. It is concluded that for detailed palynological work, particularly in conjunction with 14C dating, the extra time needed in the preparation of the Davis or the Modified Jørgensen methods is balanced by a greater reliability of result. The Matthews and Jørgensen techniques are shown to be adequate for determination of large scale changes in pollen concentration, though all methods would benefit through the addition of an ‘exotic’ pollen type in order to detect losses during preparation.
THE EFFECT OF L‐ARGININE ON THE GROWTH OF HETEROTROPHIC CULTURES OF THE EMERSON STRAIN OF CHLORELLA I. EFFECTS ON CELL GROWTH, CELL DIVISION, CHLOROPLAST DEVELOPMENT AND NUCLEIC ACID SYNTHESIS
Authors: Thinh L. V. , Griffiths D. J. 
Published: May 2006

SUMMARYCells of the Emerson strain of Chlorella grown heterotrophically on a glucose medium in darkness, do not divide normally but grow in volume well beyond their normal maximum size to give ‘giant’ cells. The delay in the onset of cell division is much reduced if L‐arginine (2 × 10‐3 M) is included in the medium. In the presence of arginine the cells reach their maximum ‘giant’ dimension sooner and then divide to produce twenty to thirty autospores‐the usual number for ‘giant’ cells. Arginine‐stimulated autospore production is preceded by chloroplast development, by an increased rate of endogenous respiration and by nucleic acid synthesis. The arginine effect is observed only if nitrate is also supplied. The arginine effect is compared with the previously reported light‐stimulated recovery of chloroplast development and autospore production in ‘giant’ cells of this strain and its significance is discussed in relation to the probable involvement of arginine in the mechanism controlling the onset of cell division.
CHLOROPLAST DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: Whatley J. M. 
Published: May 2006

SUMMARYChanges in plastid ultrastructure in the primary leaves of Phaseolus vulgaris were followed during the period of seed development and, following a period of dormancy, throughout the life span of the leaf from germination to senescence. The total life span of the leaf was about 14 weeks. During this time the plastid remained as a proplastid for about 7 weeks. Following germination, synchronous developmental changes associated with lamellar production, which lasted for a period of 1 week, resulted in the change of the proplastid into a mature chloroplast. This mature chloroplast was characteristic of the subsequent period of 2 weeks, then changes in plastid shape and in the lamellar alignment led eventually to senescence some 3‐4 weeks later. The period of rapid synchronous development during the week following germination was observed in detail and a comparison made with plastid development in plants grown in continuous darkness. Three transitory stages were consistently observed between other more persistent and generally recognized plastid developmental stages. The first occurs when the E.R. partially surrounds the proplastid during early germination; the second when the proplastid assumes an amoeboid configuration which is postulated as a precursor to various divergent plastid types; the third occurs between the developing plastid with perforated stroma lamellae and incipient grana and the mature chloroplast with continuous aligned lamellae and stacked grana.
EFFECT OF ENDOGONE MYCORRHIZA ON PLANT GROWTH VII. INFLUENCE OF INFECTION ON THE GROWTH AND NODULATION IN FRENCH BEAN (PHASEOLUS VULGARIS)
Authors: DAFT M. J. , ELGIAHMI A. A. 
Published: May 2006

SUMMARYInfections of Phaseolus with Endogone and Rhizobium compared with Rhizobium alone had increased growth, reproduction, number and weight of nodules, acetylene reduction rates, leghaemoglobin, phosphorus and total protein contents. Shoot/root ratios were lower in the dual infected plants. Levels of infection by Endogone influenced nodulation and the application of soluble phosphate simulated the effects of the fungus. The significance of these additive effects of dual symbiotic infections is discussed.
NITROGEN METABOLISM IN LICHENS V. THE FORMAS OF NITROGEN RELEASED BY THE BLUE‐GREEN PHYCOBIONT IN PELTIGERA SPP.
Authors: MILLBANK J. W. 
Published: May 2006

SUMMARYThe nitrogenous materials released by the blue‐green phycobiont (Nostoc sp.) of five lichens have been examined by means of high voltage paper electrophoresis. They were found to be a mixture of substances with similar electrophoretic characteristics to the materials released by the same algae when grown in pure culture, and were largely peptide in nature. A more detailed study was made of the components released into their growth media by the three strains of Nostoc isolated from Peltigera aphthosa, P. canina and P. polydactyla. From about twelve compounds demonstrable by electrophoresis, the six most abundant were examined for their amino acid composition. The only finding strikingly different from existing data was a generally low level of serine. Molecular weight estimates by means of gel filtration indicated that most of the substances had molecular weights of approximately 1100, with substances with molecular weights of about 300 forming a smaller important group, although materials with a wide range of molecular weights were evidently present and low molecular weight material could also be important.
THE EFFECT OF SULPHITE AND FLUORIDE ON CARBON DIOXIDE UPTAKE BY MOSSES IN THE LIGHT
Authors: INGLIS F. , HILL D. J. 
Published: May 2006

SUMMARYFour mosses, Bryum argenteum, Grimmia pulvinata, Hypnum cupressiforme and Tortula muralis were exposed to sulphite, and their uptake of radioactive bicarbonate measured. About 50% reduction in 14C uptake was caused by 0.01‐0.1 mM sulphite. The effect of pH indicated that SO2 (or‘H2SO3') was the active molecular species. Fluoride had little effect on 14C uptake.
POPULATION VARIATION, DIFFERENTIATION AND REPRODUCTIVE BIOLOGY OF STACHYS PALUSTRIS L. S. SYLVATICA L. AND
Authors: SM S. AMBIGUA , Wilcock C. C. 
Published: May 2006

SummaryThe population variation of leaf and inflorescence characters of Stachys palustris L., S. sylvatica L. and the hybrid S. ×ambigua Sm. in Britain has been studied and shows S. palustris and S. × ambigua to intergrade. S. palustris varies extensively both within and between populations and, from studies of the variation of leaf and rhizome characters in wet and dry soil, the ‘dry‐ground’ form is shown to be an ecotype. S. sylvatica is less variable, both within and between the populations sampled. S. palustris outbreeds more readily than S. sylvatica and this difference in breeding system may be responsible for the patterns of variation exhibited by the parents. Attempts to backcross S. × ambigua to either S. palustris or S. sylvatica have been totally unsuccessful. The intergradation between S. palustris and S. × ambigua is unlikely to be the result of introgressive hybridization but is principally produced since first, 5. palustris exhibits a much greater range of variation than S. sylvatica and secondly, the Ft is not intermediate but closer to S. palustris.
ASPECTS OF THE DECOMPOSITION OF SPHAGNUM LEAVES IN AN OMBROPHILOUS MIRE
Authors: DICKINSON C. H. , MAGGS G. H. 
Published: May 2006

SUMMARYThe extent of the decomposition ofSphagnum magellanicumleaves in an ombrophilous peat mire was assessed by direct observation using light and scanning electron microscopy. Although many leaves had become buried to depths of up to 30 cm without being visibly damaged there was a small proportion in which the green and hyaline cells were extensively decomposed. The progressive destruction of these cells was clearly visible using scanning microscopy. The role of fungi and animals in these processes was examined and although the former group was apparently active, especially in the superficial layers of peat, the restricted animal populations appeared to be of minor importance in the destruction of the senescentSphagnumleaves.
ENERGY‐DEPENDENT PROCESSES IN CHARA CORALLINA: ABSENCE OF LIGHT STIMULATION WHEN ONLY PHOTO‐SYSTEM ONE IS OPERATIVE
Authors: SMITH F. A. , RAVEN J. A. 
Published: May 2006

SummaryLight‐stimulated active chloride influx in Chara corallina, like that in other giant algal cells, requires the operation of photo‐system two of photosynthesis. Active phosphate influx and glucose influx also require photo‐system two for light‐stimulation, and are not stimulated by light under anaerobic conditions. This contrasts with the situation in Nitella and Hydrodictyon where influx of phosphate and glucose can be supported by photo‐system one, i.e. by cyclic photophosphorylation alone. None of the other metabolic processes in Chara tested in this work (acetate uptake and oxidation, starch synthesis, and passive Rb+ influx), or described elsewhere in the literature, are light‐stimulated when photo‐system two is inoperative. Possible explanations of this apparent inability of cyclic photophosphorylation to act as a source of metabolic energy in Chara are suggested. Their significance is discussed in relation to hypotheses of the light reactions of photosynthesis and mechanisms of light‐dependent solute transport.