bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DISTRIBUTION OF INTRASPECIFIC CHROMOSOME RACES OF HIPPOCREPIS COMOSA L. AND THEIR PHYTOGEOGRAPHICAL SIGNIFICANCE
Authors: Fearn Gillian M. 
Published: May 2006

SummaryResults of a cytological survey of Hippocrepis comosa are reported and the geographical and ecological distribution of the three chromosome races, two of which occur in Britain, is described. Reasons for the restricted distribution of the diploid race are proposed and the probable post‐glacial history of both British races is discussed. This intraspecific polyploidy is related to the evolution of a polyploid complex.
AN IMPROVED CATHODE FOR THE MEASUREMENT OF PHOTOSYNTHETIC OXYGEN EVOLUTION BY ISOLATED CHLOROPLASTS
Authors: DELIEU T. , WALKER D. A. 
Published: May 2006

SummaryThe construction, operation and calibration of an improved form of a Clark oxygen electrode are described in detail. The electrode shows a rapid response (1–5 seconds) to change in oxygen concentration and is capable of measuring rates of oxygen evolution (or uptake) of up to 4 μmoles oxygen per minute. The use of a pair of electrodes to measure the oxygen evolution of choloroplasts at high intensity of illumination is described.
NITROGEN METABOLISM OF HALOPHYTES
Authors: STEWART G. R. , LEE J. A. , OREBAMJO T. O. 
Published: May 2006

SummaryThe present paper reports a study into the activity of nitrate reductase in plants of Suaeda maritima. The growth of S. maritima in the upper salt‐marsh appears nitrogen limited, going from the upper to lower marsh there is a three‐fold increase in total nitrogen of the plants. Nitrogen status and the activity of nitrate reductase are related. Plants from the lower marsh contain a fifty times higher level of enzyme than those from the upper marsh. By feeding nitrate to plants at different sites in the marsh it was possible to induce high nitrate reductase activity in plants that previously contained low levels of the enzyme. At all sites there is an equal potential to induce nitrate reductase. The induction experiments with plants in situ suggest that in this marsh nitrate availability is the main factor limiting the growth of S. maritima in the upper marsh.
THE LOSS OF POTASSIUM AND SODIUM FROM EXCISED BARLEY AND BEAN ROOTS
Authors: NASSERY H. 
Published: May 2006

SummaryThe loss of potassium and sodium from preloaded excised barley and bean roots was compared under identical experimental conditions. In barley roots, metabolic inhibitors stimulated the potassium loss but inhibited that of sodium, indicating an active mechanism for sodium extrusion. In excised bean roots, such a mechanism could not be demonstrated and the losses of potassium and sodium were both stimulated by DNP and cold‐treatment.
STUDIES ON THE LIGNOTUBERS OF EUCALYPTUS OBLIQUA L'HERIT.
Authors: BLAKE T. J. 
Published: May 2006

SummarySeasonal variations in apical dominance, maximal in summer and minimal during winter, were noted in eucalypt lignotubers. Temperature variation was more important than photo‐period in affecting seasonal variation of apical dominance. The concentrations of growth‐promoting and growth inhibiting substances in the leaves were correlated with seasonal variation suggesting that both have a role in apical dominance. Decapitation studies indicate that amounts of mineral nutrients and carbohydrate do not prevent dormant bud development.
THE DIATOM FLORA OF THE HOXNIAN DEPOSITS AT MARKS TEY, ESSEX
Authors: EVANS G. H. 
Published: May 2006

SummarySamples from cores taken in the central and marginal areas of Hoxnian lacustrine beds at Marks Tey have been analysed for diatoms. Diatoms are extremely scarce in samples from the marginal areas. Non‐planktonic diatoms dominated the early parts of the interglacial. The change to planktonic dominance took place during the early‐temperate zone HoII. Stephanodiscus astraea var. minutula was the leading planktonic diatom. No diatoms have been found in deposits of post‐temperate age (zone HoIV), nor in the succeeding glacial deposits (Gipping Early‐glacial zone). In the Lowestoftian Late‐glacial deposits diatoms are scarce and corroded.
NITROGEN METABOLISM IN LICHENS IV. THE NITROGENASE ACTIVITY OF THE NOSTOC PHYCOBIONT IN PELTIGERA CANINA
Authors: MILLBANK J. W. 
Published: May 2006

SummaryThe content of the blue‐green alga phycobiont, Nostoc sp. in the lichen Peltigera canina has been estimated using various techniques and represents on average 2.7% of the total thallus nitrogen. Expressed in terms of cell numbers, this represents approximately 3 × 106 cells cm2, mature thallus. The nitrogenase activity, expressed as nil ethylene evolved/minute/mg Sostoc protein, varies considerably with the thallus sample, but a mean value of 10, considerably greater than that in free‐living Nostoc, has been found. The nitrogenase activity of the algal cells is particularly sensitive to disturbance of the thallus structure and the implications of these findings are discussed.
THE FREQUENCY OF HETEROCYSTS IN THE NOSTOC PHYCOBIONT OF THE LICHEN PELTIGERA CANINA WILLD.
Authors: GRIFFITHS H. BRONWEN , GREENWOOD A. D. , MILLBANK J. W. 
Published: May 2006

SummaryA reliable estimate of 3.27% for the frequency of heterocysts in the cell population of the Nostoc phycobiont present in the thallus of the lichen Peltigera canina has been obtained by electron microscopy at low magnification.
LICHEN PHYSIOLOGY XII. THE ‘INHIBITION TECHNIQUE’
Authors: HILL D. J. , SMITH D. C. 
Published: May 2006

SummaryDuring photosynthetic fixation of 14C by lichens, 14C‐carbohydrate moves from alga to fungus. If the 12C‐form of this mobile carbohydrate is added to the external medium, then the 14C‐form is released from the lichen. This observation forms the basis of the, inhibition technique', used to study movement of carbohydrates between symbionts within intact lichen thalli. The effect is specific since 14C is released from the lichen only if the 12C‐carbohydrate in the medium is identical or structurally very similar to that moving between the symbionts.This paper examines the usefulness of the technique in the study of carbohydrate movement. Lichens were exposed to a short pulse of NaH14CO3 before transfer to carbohydrate media. Relatively high concentrations of carbohydrate (20 mM–80 mM) were needed for maximum ‘inhibition’. More than half the lichens examined released over 50%, of a pulse of fixed 14C during maximum ‘inhibition’ Using 2‐desoxy‐glucose as an ‘inhibitor’ of glucose movement in Peltigera polydactyla, it was shown that the supply of glucose from the alga was more than sufficient for the metabolic requirements of the fungus. The rate release of 14C during ‘inhibition’ varied widely between different lichens, but it was not clear if this was due to differences in pool sizes of mobile caibohydrates, or to real differences in rates of carbohydrate supply. Much less carbohydrate movement between the symbionts occurred in the dark, than in the light. The effect of pH on 14C release during ‘inhibition’ contrasted sharply with effects of pH on release from freshly isolated algae. This raised further doubts whether the behavior of freshly isolated algae is similar to those in the thallus. The explanation of ‘inhibition’ on the basis of a competition between the high concentration of external carbohydrate and the much lower concentration of 14C‐carbohydrate released from the alga at fungal uptake sites may require modification in at least some lichens. Competition or exchange between 12C and 14C carbohydrates may begin at stages before the fungal uptake sites.
SOME OBSERVATIONS ON OXYGEN TRANSPORT IN CONIFER SEEDLINGS
Authors: ARMSTRONG W. , READ D. J. 
Published: May 2006

SummaryThe diffusive flux of oxygen from the roots of intact conifer seedlings was measured by a polarographic technique. With an anaerobic solution bathing the roots maintained at 23° C and with their aerial parts in air, flux rates were appreciable from eight of the twenty‐five seedlings tested. When the aerial parts were placed in oxygen, there was a large increase in flux from each pine seedling. While their general response was barely measurable, a significant but much smaller increase occurred from eight of the spruce. Oxygen transport through the plants appeared to be by diffusion chiefly in the gas phase and significant flux rates from the roots with aerial parts in air might indicate some capacity for wet soil tolerance in the seedlings concerned.When the external concentration of oxygen was increased five‐fold there was a disproportionate increase in oxygen flux from pine roots indicating that respiration in the plants might be affecting the flux rates. By cooling the bathing medium to 30 C a further demonstration of the respiratory effect‐a large increase in flux rate‐was obtained. With respiration reduced by cooling, the flux rates from the pine seedlings increased approximately five‐fold for a five‐fold increase in the external oxygen concentration. Cooling did not induce any pronounced response from the spruce seedlings.Internal diffusional resistance and oxygen leakage from the sub‐apical parts of the roots may account for the absence of high apical flux rates in the pines and the extremely low readings recorded for the spruce seedlings.
CHANGES IN GROWTH AND METABOLISM OF EXCISED PEA ROOTS ASSOCIATED WITH IRON DEFICIENCY II. CHANGES IN NUCLEIC ACIDS
Authors: ABBOTT A. J. 
Published: May 2006

SummaryThe effects of iron deficiency on growth and metabolism of isolated pea roots grown in sterile culture have been further studied. Investigations at time intervals during a culture passage and by serial sectioning of roots at a critical stage of deficiency, have shown the distribution, concentration and composition of nucleic acids in relation to iron depletion. The significance of the results is discussed in relation to the primary role of iron in metabolism. It is suggested that the primary lesion resides in systems responsible for RNA synthesis. Formation of a soluble RNA fraction is inhibited, which in turn may cause failure to produce those enzyme proteins necessary for cell division and resulting in secondary disturbances which are a feature of the iron deficiency syndrome.
PHYTOCHROME AND SEED GERMINATION
Authors: HOLDSWORTH M. 
Published: May 2006

SummaryBoth tobacco ‘Virginia Gold’ and Plantago hirtella seed germinate on exposure to red light. During the first day or so after sowing, the response can be stopped by a following exposure to deep‐red, indicating phytochrome action. However, the effects of successive exposures to red are additive through intervening exposures to deep‐red. Moreover, after several days in the dark, both red and deep‐red induce germination.
CYTOLOGICAL STUDIES IN DORMANCY II. PATHOLOGICAL AGEING CHANGES DURING PROLONGED DORMANCY AND RECOVERY UPON DORMANCY RELEASE
Authors: VILLIERS T. A. 
Published: May 2006

SummarySeeds with a chilling requirement were maintained fully imbibed at 22–25° C for more than 6 years without germination. Similar seeds stored air‐dry at the same temperatures were dead by the second year. Cytological changes in the radicle meristem cells during the first year included the development of complex associations of ER with protein bodies. After 2 years imbibition, cytolysomes were formed, and by the fifth year membrane systems were extensively damaged. Upon release from dormancy, germination was delayed compared with that of normal, unaged embryos. During this delay, the vacuoles acted as lysosomes, engulfing and hydrolysing cytoplasmic organelles. Renewal was by sub‐division of existing organdies, separating damaged from apparently normal zones by the formation of partition membranes. The relationship between lysosomal systems and the plant cell vacuole is discussed. The extended viability of imbibed seeds compared with dry seeds is discussed in relation to the possibilities of running repairs to membrane and genetic systems whilst the tissue is hydrated.
CYTOLOGICAL STUDIES IN DORMANCY III. CHANGES DURING LOW‐TEMPERATURE DORMANCY RELEASE
Authors: VILLIERS T. A. 
Published: May 2006

SummaryThe cytological changes occurring in dormant embryo radicle meristem cells of Fraxinus excelsior during the period of chilling before germination are described. The only events observed to be dependent on low temperature occurred in the nucleolus, which increased in volume and complexity of structure. A large, low temperature‐dependent increase in total cellular RNA occurred during chilling, and autoradiography showed preferential incorporation of RNA precursor into the nucleolus during this treatment. Other changes observed included the formation of smooth ER, the development of plastid inclusion bodies, and the formation of cytolysomes. As these changes also took place in control embryos maintained at 22° C, they were probably not directly concerned in the relief of dormancy by chilling. Certain deleterious changes are discussed in relation to the stress which may be experienced by the embryo during dormancy.
ULTRASTRUCTURAL OBSERVATIONS ON PINACEAE LEAF PHLOEM I. THE SPRING CONDITION
Authors: HARRIS WILLIAM M. 
Published: May 2006

SummaryPine and spruce leaves were fixed for electron microscopy during their period of rapid differentiation (April‐May 1970). The sieve cells are in radial rows and mature from the outside towards the inside of the leaf. The sieve cell initials have large nuclei and many organelles. As the sieve cells mature, the walls become thick and lamellar, the tonoplast breaks down, and most of the organelles disappear. The plastid stroma becomes fibrillar. The plastids then rupture, releasing fine fibrils into the mictoplasm. The plasmodesmata between phloem parenchyma cells and albuminous cells occur in expanded regions of the cell wall. The sieve areas have little callose in the spring.
INHIBITION AND STIMULATION OF THE RESPIRATION OF ARUM MITOCHONDRIA BY CYANIDE AND ITS RELATION TO THE COUPLING OF OXIDATION AND PHOSPHORYLATION
Authors: WEDDING R. T. , MCCREADY C. C. , HARLEY J. L. 
Published: May 2006

SummaryMitochondria prepared by standard methods from the sterile spadix of Arum maculatum show relatively poor coupling (ADP/O = 0.5–1.0, respiratory control ratio =1.5–2.8). This coupling is, however, crucial to the response elicited by the application of cyanide. Mitochondria oxidizing malate are inhibited by cyanide with an apparent Ki of 0.3 mM, but an infinitely high cyanide concentration would produce only 50–60% inhibition. With succinate, similar high concentrations of cyanide cause substantial (30–50%) stimulation of the rate of oxidation. When the mitochondria are completely uncoupled by the presence of dinitrophenol or by freezing and thawing, the application of cyanide causes a 12–40% stimulation of the rate of malate oxidation and an even greater increase in that of succinate oxidation. This stimulation by cyanide is not dependent on the nature of the cation supplied.The inhibitor of cyanide‐resistant respiration, mCLAM,† shows an inhibition additive to that of cyanide with coupled mitochondria, with an apparent Ki of 12–40 μM and 2 maximal inhibition of 40–80%, but in the presence of DNP the addition of mCLAM completely eliminates the cyanide‐sensitive oxidation of succinate or malate.These results indicate the presence of two pathways for electron transport in Arum mitochondria, of which one, the cyanide‐resistant pathway, is more readily available to the dehydrogenase of succinate than to that of malate and those of other substrates using DPN. The uncoupling of phosphorylation appears to permit electrons to flow more readily through the resistant pathway from either malate or succinate. The cyanide‐sensitive pathway appears to be inhibited readily by mCLAM, and the fact that the stimulation of oxidation by KCN is abolished by mCLAM indicates that the resistant pathway is responsible for the increased flow of electrons in the presence of cyanide.
MEASUREMENT OF NITRATE‐ AND NITRITE‐REDUCTASE ACTIVITIES IN WHOLE CELLS OF CHLORELLA
Authors: SYRETT P. J. 
Published: May 2006

SummaryA method is described for the assay of nitrate‐reductase activity in frozen and thawed cells of Chlorella. The method depends on coupling nitrate reductase with malic dehydrogenase, both enzymes and the necessary coenzyme being retained within frozen/thawed cells. Other ways than destroying permeability by freezing are considered and a short treatment of fresh cells with 1.5 M glycerol is shown to be effective. The method has been used to follow the induction of nitrate‐reductase activity in Chlorella. Other enzyme activities that can be measured by similar methods, i.e. by enzymic coupling within damaged cells, are nitrite reductase and urea amidolyase.
UPTAKE OF PICLORAM BY EUCALYPT LEAF DISCS
Authors: SANDS R. , BACHELARD E. P. 
Published: May 2006

SummarySurfactants markedly increased the uptake of picloram by Eucalyptus viminalis and E. poly‐anthemos leaf discs. The effects of different surfactants and different surfactant concentrations on uptake depended largely on the degree of wetting by the applied solution on the leaf surface.A species‐surfactant interaction was evident with some surfactants, and this was examined in terms of differences in leaf‐surface characteristics between the two species. The effects of surfactants on the leaf surfaces were also observed.The inadequacy of surface tension as a measure of the ability of a solution to wet leaves, and to stimulate herbicide uptake, is discussed.
SOME GENERAL EFFECTS OF PHOSPHORUS DEFICIENCY ON GROWTH AND DEVELOPMENT
Authors: ATKINSON D. 
Published: May 2006

SummaryA number of general effects of phosphorus deficiency on plant growth are described. The experiments employed a wide range of species from different ecological habitats. Most species followed a similar pattern regardless of ecological origin.Seed size seemed to be the principal factor determining the severity of deficiency in short‐term experiments. Deficiency affected root/shoot ratio, hydration and leuco‐anthocyanin content. Even when plants were severely affected by deficiency they were sensitive to the physical environment.
A COMPARATIVE STUDY OF THE EFFECT OF SOIL‐ AND LEAF‐APPLIED PHOSPHORUS ON THE YIELD OF BARLEY (HORDEUM VULGARE L.)
Authors: AFRIDI M. M. R. K. , SAMIULLAH  
Published: May 2006

SummaryBarley (Hordewn vulgare L.) variety N.P. 13 gave a higher yield of grain when an aqueous solution of phosphate was applied to the tops 70–80 days after sowing as compared with the controls sprayed with de‐ionized water only. The beneficial effect of spray was generally more pronounced when the plants had received a small dose of phosphatic fertilizer by basal dressing than when they were grown without soil‐applied phosphorus.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE BARBARA 
Published: May 2006

SummaryThe growth of mycorrhizal and non‐mycorrhizal plants was compared in several soils receiving increasing amounts of Ca(H2PO4)2. In some soils mycorrhizal plants grew better at all levels of applied phosphate. In other soils, where high phosphorus concentrations built up rapidly in the plants, those with mycorrhiza grew worse when more than 0.2 g Ca(H2PO4)2 was added per kg of soil. Because their roots take up more phosphate, mycorrhizal plants may reach supra‐optimal phosphorus concentrations with smaller amounts of added phosphate.Mycorrhiza tended to die out when 1 g Ca(H2PO4)2 or more was given per kg soil. With added phosphate no arbuscules were formed, many attenuated hyphae ramified through the cortex and the host seemed to have lost control over fungal development. Eventually only certain, morphologically distinct cells in the sub‐epidermal layer were infected. With 6 g Ca(H2PO4)2 root infection disappeared completely, but some viable inoculum survived in the soil.
PHOTOSYNTHESIS BY ISOLATED CHLOROPLASTS: SOME FACTORS AFFECTING INDUCTION IN CO2‐DEPENDENT OXYGEN EVOLUTION
Authors: WALKER D. A. , KOSCIUKIEWICZ KRYSTYNA , CASE CHRISTINE 
Published: May 2006

SUMMARYOxygen production by chloroplasts isolated from spinach was measured. The lag in oxygen production following first illumination of the chloroplasts was independent of light intensity and chlorophyll concentration. The length of the lag period was unaffected by addition of DCMU to the reaction mixture but was increased by addition of orthophosphate or arsenate. It was also longer at lower temperatures. The data are consistent with the view that the lag results from the time necessary for the concentration of photosynthetic metabolites to increase to a level that allows maximal rate of photosynthesis. However, anomalies in behaviour occur and their significance is discussed.
THE CONVERSION OF GLYCERATE INTO PYRUVATE BY CHLORELLA EXTRACTS
Authors: LORD J. M. , MERRETT M. J. 
Published: May 2006

SUMMARYCell‐free extracts from autotrophically grown Chlorella convert glycerate to pyruvate by the reactions of glycolysis. It has already been demonstrated that exogenous glycollate is metabolized to glycerate by the reactions of the glycollate pathway in Chlorella. The activities of the constituent enzymes of glycolysis are great enough to account for the further metabolism of glycerate formed during the metabolism of exogenous glycollate by Chlorella.
[3H]THYMIDINE UTILIZATION IN THE PRIMARY ROOT OF VICIA FABA L.
Authors: MACLEOD R. D. 
Published: May 2006

SUMMARYThe size of the endogenous pool of TdR in roots of Vicia faba was found to influence the rate of [3H]TdR incorporation into DNA. Thus, increasing the size of this pool, as a result of treatment with TdR, resulted in a decrease in the amount of [3H]TdR incorporated into DNA, while decreasing the size of the endogenous TdR pool, resulted in increased incorporation of [3H]TdR into DNA. The size of the TdR pool could be decreased by excising the roots or by removing the cotyledons. TdR was found to be transported to the root apex from the cotyledons in young V. faba plants.The pattern of distribution of 3H‐compounds in the primary root of V. faba was found to change with increase in duration of the period of exposure to [3H]TdR. These changes were a consequence of the movement of 3H‐compounds from the base of the root to the apex and of the fact that DNA synthesis was greater in the root apex than in more basal segments.
THE EFFECTS OF PHOSPHORUS DEFICIENCY ON WATER CONTENT AND RESPONSE TO DROUGHT
Authors: ATKINSON D. , DAVISON A. W. 
Published: May 2006

SUMMARYAcute phosphorus deficiency was induced in seedlings of a number of species over a period of 5 weeks. Deficiency affected dry weight, root/shoot ratio, leaf water content, leaf water deficits and the time taken for the plants to show visible stress after watering was stopped. Populations of two of the species from soils differing in phosphorus status showed consistent and major differences in the effects of phosphorus deficiency. The ecological implications of the results are discussed.
THE PRODUCTION OF TREHALOSE AND POLYOLS BY USTILAGO NUDA IN CULTURE AND THEIR UTILIZATION IN HEALTHY AND INFECTED WHEAT PLANTS
Authors: GAUNT R. E. , MANNERS J. G. 
Published: May 2006

SUMMARYIn liquid culture, Ustilago nuda hydrolyses exogenous sucrose and endogenously synthesizes trehalose, mannitol and erythritol. The two polyols are released into the medium. When injected into healthy host tissue, mannitol did not appear to be readily metabolized, but erythritol was converted into an unidentified compound, probably a glycoside derivative. It is suggested that a reciprocal flow of carbohydrate may occur from the fungus to the host. Spores produced in culture were shown to be pathogenic.
VESICLES IN THE PHYCOBIONT SHEATH AS POSSIBLE TRANSFER STRUCTURES BETWEEN THE SYMBIONTS IN THE LICHEN LICHINA PYGMAEA
Authors: PEVELING ELISABETH 
Published: May 2006

SUMMARYIn the lichen Lichina pygmaea, there are numerous vesicles in the fibrillar sheath of the phycobiont (a blue‐green alga of the genus Calothrix). The possible function of these vesicles is discussed in connection with the metabolic exchange between the symbionts.