bluuebunny/crossref_metadata_2025_split huggingface dataset:
NITROGEN METABOLISM OF HALOPHYTES III. ENZYMES OF AMMONIA ASSIMILATION
Authors: STEWART G. R. , RHODES DAVID 
Published: May 2006

SUMMARYThe occurrence of glutamine synthetase, glutamate synthase and glutamate dehydrogenase in a range of halophytic higher plants has been investigated. Ferredoxin‐dependent glutamate synthase was found in shoot tissue of all the species examined. Root tissue glutamate synthase was active with both reduced pyridine nucleotides and reduced ferredoxin. The levels of enzymes present in the majority of species are consistent with the view that ammonia assimilation occurs via the combined action of glutamine synthetase and glutamate synthase. An increase in external salinity lowers the levels of glutamine synthetase and glutamate dehydrogenase of root tissue but increases the level of shoot glutamine synthetase.
THE TOLERANCE OF TREE ROOTS TO WATERLOGGING
Authors: PHILIPSON J. J. , COUTTS M. P. 
Published: May 2006

SUMMARYSeedling root systems, or individual roots of cuttings, were submerged in reduced indigo‐carmine solution so that only the seedling shoot, or basal part of the cutting root, was exposed to air or oxygen. Oxygen diffusing out of the roots produced a localized blue colouration of the previously clear reduced dye; this process was employed to study internal oxygen movement.Using plants grown in freely drained soil it was evident that seedlings of the flood‐tolerant species, Lodgepole pine, had a greater capacity for oxygen transport than the flood‐intolerant Sitka spruce. Oxygen diffusion was also observed in roots detached from Lodgepole pine cuttings and was greatly enhanced in plants which had grown in waterlogged conditions; in the latter plants oxygen diffusion was detected from the root tips after a short exposure of the basal region of the root to oxygen, whereas roots from plants grown in freely drained soil showed diffusion of oxygen only from the upper submerged portion during the same treatment period. Oxygen diffusion over distances of more than 30 cm was detected in certain experiments.Observations on the movement of gas supplied under pressure to Lodgepole pine root segments showed that the rate of gas flow was much greater in roots grown in waterlogged soil than in those grown in freely drained soil and that the gas movement occurred in the stelar tissues. The regions of oxygen entry included the needles, and lenticels on the roots.
LIMITATION OF GAEUMANNOMYCES GRAMINIS BY WHEAT ROOT RESPONSES TO PHIALOPHORA RADICICOLA
Authors: SPEAKMAN J. B. , LEWIS B. G. 
Published: May 2006

SUMMARYChanges in wheat roots invaded by Phialophora radicicola var. graminicola, P. radicicola var. radicicola and Gaeumannomyces graminis var. tritici were explored. Progress of Phialophora radicicola var. graminicola was arrested by lignitubers in the third cortical layer whereas P. radicicola var. radicicola progressed as far as the innermost layer of the cortex, failing to penetrate the endodermis, but was not arrested by detectable structural changes. Both varieties of P. radicicola elicited considerable lignification of the stelar components, and lignification and suberization of the inner tangential wall of the endodermis. When the two species of fungi were inoculated on the same root, P. radicicola var. graminicola prevented Gaeumannomyces graminis var. tritici from spreading longitudinally in the stele.
STUDIES ON OUTER EPIDERMAL CELL WALLS WITH MICROCHANNELS IN A XEROPHYTIC SPECIES
Authors: LYSHEDE OLE B. 
Published: May 2006

SUMMARYIn the thick cutinized outer epidermal wall in the stem of Spartocytisus filipes radiating microchannels have been observed. The structure of the wall and the microchannels have been investigated by histochemistry, polarized light, and electron microscopy. The micro‐channels contain pectic substances and branch richly. The structure of the wall and the microchannels are discussed in relation to the ecology of the plant.
FLORAL ENANTIOMORPHY AND THE REPRODUCTIVE SYSTEM OFWACHENDORFIA PANICULATA(HAEMODORACEAE)
Authors: ORNDUFF ROBERT , DULBERGER RIVKA 
Published: May 2006

SUMMARYFlowers of the South African genusWachendorfia(Haemodoraceae) are dimorphic. Some individuals in a population produce flowers in which the style and one stamen are deflected to the right and the other two stamens are deflected to the left; other individuals produce flowers with the reverse arrangement of style and stamens. Articifical pollinations ofW. paniculataindicate that it has a weakly developed self‐incompatibility system; intermorph crosses produced more seeds than self‐pollinations or intramorph pollinations. Features of the floral morphology ofW. paniculatasuggest that it is pollinated by a large‐bodied insect, possiblyXylocopa.The dimorphism in the position of anthers and stigmas probably increases the level of intermorph pollination. The low sugar concentration of the nectar, low pollen production per flower, and few flowers per plant also probably result in pollinators visiting more than one plant during their foraging activities, thus reinforcing the floral dimorphism and increasing the opportunities for intermorph pollination.
THE AZOLLA‐ANABAENA AZOLLAE RELATIONSHIP
Authors: PETERS G. A. , TOIA R. E. , RAVEED D. , LEVINE N. J. 
Published: May 2006

SUMMARYThe nitrogen‐fixing blue‐green alga, Anabaena azollae, occurs as a symbiont in leaf cavities of the water fern, Azolla. Organization and morphological aspects of the association, with emphasis upon the cavity area, were studied by light, transmission, and scanning electron microscopy. Cleared whole mounts, sectioned, and enzymatically digested materials were employed. Leaf cavity formation, including the association of the symbiont and epidermal hairs, is shown during leaf development in A. caroliniana Willd. Enzymatic digestion of the fern leaf tissue provided preparations of algal packets which correspond to the leaf cavity area. The digestion process complemented other approaches in providing insight into the organization of the leaf cavity. Scanning electron microscopy allowed visualization of these packets in three dimensions. The packets are surrounded by a filmy, limiting envelope of unknown composition. The envelope was isolated and shown to remain associated with hairs which protrude into the cavity area. The hairs are multicellular and may be branched or unbranched. When nitrogen fixation by the symbiont is the sole nitrogen source, sections through some cells of hairs in mature leaf cavities exhibit the ultrastructural characteristics of transfer cells. These characteristics are not observed, however, in sections through cells of hairs associated with the early stages of leaf cavity formation in the shoot tip. The potential significance of the envelope and hair cells in the metabolic interaction of the host and symbiont are discussed.
TRANSLOCATION AND TRANSFER OF NUTRIENTS IN VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: COOPER KAREN M. , TINKER P. B. 
Published: May 2006

SUMMARY Trifolium repens (white clover) or Allium cepa (onion) infected with the mycorrhizal fungus Glomus mosseae were grown in split‐plate cultures, so that nutrients could be supplied to the external hyphae only. The uptake and translocation of 32P, 65Zn and 35S by hyphae of the fungus was measured.A lag phase of 2‐3 days in the appearance of 32P in the shoot was caused by a delay in the uptake and translocation of P by the hyphae, rather than in transfer from fungus to host.The calculated maximum translocation rate of P for onion was 6.4 × 10−16 mole s−1, and the P flux in the hyphae about 2 × 10−10 mole cm−2 s−1. The molar amounts of P, S and Zn translocated were in the ratio of 35:5:1 and the mean fluxes in the ratio of 50:8:1 with clover.
STRUCTURAL RESISTANCES TO MASS TRANSFER IN THE LICHEN XANTHORIA PARIETINA
Authors: COLLINS C. R. , FARRAR J. F. 
Published: May 2006

SUMMARYQuantitative morphological data obtained from Xanthoria parietina by light and electron microscopy is related to measurements of photosynthesis rate and estimates of biotrophic ribitol transfer. It is concluded (a) that diffusive CO2 flux into the alga is greatly reduced by the resistance of the fungal cortex, (b) that diffusion can easily account for the mass transfer of ribitol from alga to fungus, and (c) that haustoria have no role in the biotrophic transfer of carbohydrate in lichens.
FRUIT DEVELOPMENT AND WAX BIOSYNTHESIS IN JOJOBA
Authors: BENZIONI ALIZA 
Published: May 2006

SUMMARYSimmondsia chinensis (jojoba), a wild desert shrub, is known for its fruit which contains unique wax esters similar in nature to sperm‐whale oil (Yermanos and Duncan, 1976). In this work, the ability of the fruit to synthesize the wax esters has been studied from a very early stage to ripening.
AN ANATOMICAL STUDY OF ROOT INITIATION IN STEM CUTTINGS OF HYBRID LARCH
Authors: JOHN ALLAN 
Published: May 2006

SUMMARYThe stages in the development of roots in stem cuttings of Hybrid larch have been investigated. Callus develops from a new meristem after the establishment of a cortical vascular system. Roots arise from near the tip of this cortical vascular system and emerge as partially differentiated structures after approximately 42 days.
OCCURRENCE OF HELICAL THICKENINGS IN THE VESSELS OF NEW ZEALAND WOODS
Authors: MEYLAN B. A. , BUTTERFIELD B. G. 
Published: May 2006

SUMMARYHelical thickenings were observed on the vessel walls of ninety woods indigenous to New Zealand. They were not observed in a further eighty‐eight species. Four types of thickenings are described: faint striations, light helical thickenings sometimes merging with the vessel wall, prominent helical thickenings and very prominent close helical thickenings. These types are illustrated with scanning electron micrographs.Although the helical winding orientation was predominantly in the S‐direction, considerable variation was observed in the helical winding angle both between adjacent vessel members of similar dimensions, and also within individual cells.Vestures were observed adhering to the helical thickenings in three species.
VARIATION IN BRASSICA OLERACEA L. SUBSP. OLERACEA (WILD CABBAGE) DETECTED BY THE PICRATE TEST
Authors: MITCHELL N. D. , RICHARDS A. J. 
Published: May 2006

SUMMARYVariation in response to the Guignard pictate test may be detected within wild British populations of Brassica oleracea L. subsp. oleracea. Plants with the greatest reaction are the least frequent. In different seasons, individuals react differently to the test, possibly in response to temperature fluctuations. In B. oleracea the picrate test is perhaps responding to allyl derivatives of the glucosinolate sinigrin; HCN was not detected.
EFFECT OF ABSCISIC ACID AND BENZYL ADENINE ON THE INORGANIC AND ORGANIC COMPOSITION OF THE DUCKWEED, LEMNA GIBBA L.
Authors: DEKOCK P. C. , VAUGHAN D. , HALL A. 
Published: May 2006

SUMMARYThe inhibition of growth of Lemna gibba fronds by abscisic acid is accompanied by typical changes in mineral composition such that the ratios of phosphorus to iron and potassium to calcium are lowered compared with normal growing fronds. Benzyl adenine added with abscisic acid tends to reduce these changes and re‐establish growth causing the above ratios to be increased.
MYCORRHIZAL DEPENDENCY OF SEVERAL CITRUS CULTIVARS UNDER THREE NUTRIENT REGIMES
Authors: MENGE J. A. , JOHNSON E. L. V. , PLATT† R. G. 
Published: May 2006

SUMMARYSix citrus cultivars were grown with and without the mycorrhizal fungus Glomus fasciculatus under three fertilizer regimes all without phosphorus. The average mycorrhizal dependency (Gerdemann 1975) of Rough lemon and Brazilian sour orange were greater than the mycorrhizal dependecies of Alemow, Troyer citrange, Bessie sweet orange and Trifoliate orange. The mycorrhizal dependency of each cultivar, except Bessie sweet and Trifoliate orange, was substantially altered by at least one of the fertilizer regimes, and therefore the order of mycorrhizal dependency was different at all three fertilizer regimes. On the average, citrus rootstocks exhibited the greatest mycorrhizal dependency with the least fertilization. The average percentage phosphorus in non‐mycorrhizal leaf tissues was inversely correlated with the mycorrhizal dependency of citrus cultivars at the medium fertilizer regime. An inverse correlation was observed between the dry weights of non‐mycorrhizal roots of the citrus cultivars and the mycorrhizal dependency of the citrus cultivars.
INFLUENCE OF BACTERIA IN THE PHYLLOSPHERE OF CAMELINA SATIVA (L.) CRANTZ ON GERMINATION OF LINUM USITATISSIMUM L.
Authors: LOVETT J. V. , SAGAR G. R. 
Published: May 2006

SUMMARYIn a series of experiments, aqueous washings of the leaves of Camelina sativa (L.) Crantz consistently stimulated the growth in length of radicles of germinating seeds of Linum usitatissimum L. The presence of free‐living nitrogen‐fixing bacteria in the Camelina phyllosphere was necessary for the production of the stimulation.
THE GREEN HYDRA SYMBIOSIS
Authors: JOLLEY ELIZABETH , SMITH D. C. 
Published: May 2006

SUMMARYThe Chlorella symbiont of the ‘European’ strain of green hydra has been isolated into pure culture using conventional microbiological techniques. The symbiont grew well on Bold's basal medium, indicating that it had no fastidious nutritional requirements. It grew rapidly on liquid media, but very slowly on agar–which may explain why previous authors have failed to isolate it. The ultra structure of the cultured isolate agrees closely with published descriptions of the symbiont. The cultured isolate could also reinfect aposymbiotic hydra, and a cycle of reisolation and reinfection was followed. The cultured isolate lacked the property of maltose excretion normally shown by symbionts, but this property was restored after reinfection. A hypothesis is advanced to explain the induction of maltose synthesis and release by host animal cells.
INHIBITION BY ZINC OF SOLUBLE AND CELL WALL ACID PHOSPHATASES OF ZINC‐TOLERANT AND NON‐TOLERANT CLONES OF ANTHOXANTHUM ODORATUM
Authors: COX R. M. , THURMAN D. A. 
Published: May 2006

SUMMARYInhibitor constants, Ki and K'i for zinc have been determined for a number of soluble and cell‐wall‐bound acid phosphatases of two zinc‐tolerant and two non‐tolerant clones of Anthnxanthum odoratum. The values of Ki for the soluble enzymes of both clones approached infinity which suggested that the inhibition was mainly of an uncompetitive nature. The tolerant clones possessed Ki values for soluble and cell wall enzymes which were significantly higher than the corresponding values for the non‐tolerant clones. K'i values of the cell wall enzymes of tolerant and non‐tolerant clones were not significantly different from one another. It was concluded that non‐tolerant clones possess acid phosphatases which form more stable complexes with zinc than tolerant ones. The relevance of this observation to metal tolerance mechanisms is discussed.
THE EFFECTS OF AIR POLLUTION ON PLANT GROWTH WITH SPECIAL REFERENCE TO SULPHUR DIOXIDE
Authors: CRITTENDEN P. D. , READ D. J. 
Published: May 2006

SUMMARYA glasshouse for the study of the effects of ambient levels of air pollution on plant growth is described. Two sealed sub‐sections were force‐ventilated, one received SO2‐polluted ambient air while a second received air that had been passed through an activated carbon filter to remove SO2. Potential diffuse and direct incoming radiation, air temperature and humidity were examined in both chambers in order to determine whether differences in microclimatic factors other than air quality existed between the two ail treatments. Daily mean concentrations of SO2 and suspended particulate matter were measured in the two chambers and outside the glasshouse. During 2 years of continuous monitoring neither pollutant was detected in the filtered air while levels in the unfiltered section were usually below 100 μg m−3SO2 and 50 μg m−3 particulates. Discrepancies between the two chambers in the predicted light conditions and humidity and differences in environmental conditions between the glass enclosures and the open air are discussed critically. The possible occurrence of secondary gaseous pollutants in the unfiltered air in addition to SO2 is also considered.
ENVIRONMENTAL INFLUENCES ON PHOTOSYNTHESIS AND GROWTH IN FRAG ARIA VESCA
Authors: CHABOT BRIAN F. 
Published: May 2006

SUMMARYGrowth of Fragaria vesca under several conditions of temperature and light was closely related to rates of net photosynthesis calculated for the growing conditions. This suggests that the rate of photosynthetic carbon accumulation is limiting for the overall success of the individual and that metabolic acclimation of net photosynthesis to the environment may be an important adaptation for improving general carbon balance. Growth rate showed differing sensitivity to the five environmental factors investigated; variation in light produced the greatest changes while nutrient levels had little effect. There was good buffering of physiological processes at moderate temperatures with growth reduction pronounced only at temperature extremes.Under all treatments there was a reduction in the proportion of biomass allocated to reproduction as total biomass accumulation became limited. Temperature treatments shifted reproductive allocation from flowering at low temperatures, to vegetative propagation at higher temperatures. Plants were capable of growing vegetatively under the most limiting conditions without reproducing. It is possible, therefore, that natural limits to distribution may coincide with limits to physiological performance and dispersal rather than to the ability of a population to reproduce itself in place.
FACTORS AFFECTING ABSCISSION IN SPIRODELA OLIGORHIZA (LEMNACEAE)
Authors: WITZTUM A. , KEREN O. 
Published: May 2006

SUMMARYExposure of plants of Spirodela oligorhiza to ultraviolet light results in a high percentage of abscission of daughter colonies. The levels of endogenous ABA and ethylene released in irradiated plants were similar to those of the non‐irradiated controls. Pre‐incubation on IAA very significantly reduced UV‐induced abscission in spite of causing a large release of ethylene.
SCANNING ELECTRON MICROSCOPY OF SURFACE FEATURES OF EUCALYPT MYCORRHIZAS
Authors: SEVIOUR R. J. , HAMILTON D. , CHILVERS G. A. 
Published: May 2006

SUMMARYScanning electron micrographs of surface features are a useful aid for distinguishing mycorrhizas formed by different fungal components. Some of these features raise important questions about mycorrhizal morphogenesis and associated hyphal wall structure.
EFFECTS OF HANDLING AND SURGICAL TREATMENTS ON NITROGENASE ACTIVITY IN ROOT NODULES OF ALNUS GLUTINOSA, WITH SPECIAL REFERENCE TO THE APPLICATION OF INDOLE‐ACETIC ACID
Authors: WHEELER C. T. , CAMERON ELIZABETH M. , GORDON J. C. 
Published: May 2006

SUMMARYThe possible effects of applied indole‐acetic acid upon nitrogenase activity and respiration in alder nodules could not be distinguished from the effects of the manipulative procedures themselves. The extent to which plants were handled during the acetylene reduction assay had a large inhibitory effect upon the apparent nitrogenase activity of the nodules.
THE ONSET OF NITROGEN FIXATION IN YOUNG ALDER PLANTS AND ITS RELATION TO DIFFERENTIATION IN THE NODULAR ENDOPHYTE
Authors: MIAN SALMA , BOND G. 
Published: May 2006

SUMMARYThe acetylene assay was used to find how soon nitrogenase activity could be detected in young, nodulating alder plants. Samples taken at intervals initially of 2–3 days were assayed, starting as soon as external signs of nodulation were seen, and continuing for a further 33 days. Squash preparations made from the nodules of the assayed plants were examined microscopically to detect whether there was any relation between nitrogenase activity and the stage of differentiation of the nodule endophyte.No nitrogenase activity was detected on the first two assay occasions, on which the endophyte was confined to the hyphal stage in all the nodules present. Activity was detected on the subsequent occasions, its onset coinciding with the production of vesicles by the endophyte. Activity rose as the vesicles became more abundant, and in agreement with the limited previous evidence it was concluded that the vesicles, but not the hyphae, are nitrogen‐fixing. The third type of structure produced by the alder endophyte, namely the bacteroid stage, was not detected in the young nodules studied here.The onset of nitrogenase activity in the nodules preceded by 16 days the increased greening of the leaves signifying the arrival in the shoot of products of nitrogen fixation. Ethylene production per plant increased in exponential manner over the period of the experiment, while ethylene production per unit weight of nodule tissue rose ten‐fold
ANALYSIS OF EFFECTS OF THE BIRD CHERRY‐OAT APHID ON THE GROWTH OF BARLEY: UNRESTRICTED INFESTATION
Authors: MALLOTT P. G. , DAVY A. J. 
Published: May 2006

SUMMARYInfestation with the bird cherry‐oat aphid considerably reduced the dry weight yield, the leaf area, the number of tillers and the number of leaves of barley plants. Growth analysis revealed that the major effect of infestation was to reduce unit leaf rate. However, infested plants compensated partially for this by allocating a greater proportion of their dry weight to the production of leaf laminae than did the control plants.Rates of net photosynthesis in individual, attached leaves were measured using the carbon dioxide exchange method; infested and control plants were found to have very similar rates of photosynthesis. Thus the reduction of unit leaf rate did not result from an effect of photosynthesis. It is suggested that the decreased growth of the barley plants is explicable in terms of cumulative assimilate loss due to aphid feeding.
THE ANT‐PLANTS MYRMECODIA AND HYDNOPHYTUM (RUBIACEAE), AND THE RELATIONSHIPS BETWEEN THEIR MORPHOLOGY, ANT OCCUPANTS, PHYSIOLOGY AND ECOLOGY
Authors: HUXLEY CAMILLA R. 
Published: May 2006

SUMMARYThe history of investigation of the ant‐plants is briefly reviewed and the external morphology of the plants described. Within Papua New Guinea ant‐plants are abundant in open‐canopied environments and less common but more diverse in rain forest. They also occur terrestrially above 2400 m. Initial tuber development was found to be similar that described by Treub (1883). Later cavities are formed by successive, increasingly complex phellogens. In certain Myrmecodia spp. later cavities are differentiated into regions with distinct surface characteristics, shapes and positions. Cavities in Hydnophytum are simpler in shape but sometimes differentiated in other ways. The anatomy of the cavity surfaces, especially the putative absorption sites ('warts') is described.The ant Iridomyrmex cordatus, which is common in ant‐plants in other regions, is found in ant‐plants in open habitats in Papua New Guinea, but is replaced by I. cf. scrutator in rain forest and above 2000 m. Two fungi, known also from ant‐plants in Java (Miehe, 1911a), occur in the cavities of ant‐plants throughout Papua New Guinea. Arthrocladium sp. Papend. grows on cavity surfaces where ant faecal material is present and the other (an unidentified Monilialine fungus) is parasitic on smooth, clean surfaces. The former is most common and the latter almost confined to Myrmecodia spp. occupied by Iridomyrmex cordatus.Experiments suggested that both Hydnophytum under artificial conditions and Myrmecodia under field conditions grow better in the presence than absence of Iridomyrmex cordatus and that the stimulus might be that of minerals supplied by the ants. Radioisotopes in both organic and inorganic compounds fed to I. cordatus were deposited preferentially by the ants on the warted cavity surfaces where ant faecal material was present, and were absorbed by the plants. In the discussion it is argued that the plant/ant relationship has had a considerable influence on both the ecology and evolution of the plants, but that this varies in different species.