bluuebunny/crossref_metadata_2025 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

Summary

Cavitation 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

Summary

Methods 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

Summary

An 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

Summary

A 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

Summary

The 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

The 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

The 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

In 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

Seedlings 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

Uninfected 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

After 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

Salt 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

Pollen 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

Laboratory 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

Cells 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

Changes 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

Infections 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

The 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

Four 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

The 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

The 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

Summary

Light‐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.
THE EFFECT OF MECHANICAL FORCES ON THE EXUDATION OF ORGANIC SUBSTANCES BY THE ROOTS OF CEREAL PLANTS GROWN UNDER STERILE CONDITIONS
Authors: BARBER D. A. , GUNN K. B.
Published: May 2006

Summary

Cereal plants were grown for 3 weeks under sterile conditions in solution culture with their roots either unrestricted or growing between glass ballotini.

The exudation of both amino acids and carbohydrates was increased when the roots were grown through a solid medium and the total quantity exuded was equivalent to about 9% of the dry matter increment of the roots.
THE RESPONSE OF MYCORRHIZAL AND NONMYCORRHIZAL ROOTED CUTTINGS OF HEATHER (CALLUNA VULGARIS (L.) HULL) TO VARIATIONS IN NUTRIENT AND WATER REGIMES
Authors: BANNISTER P. , NORTON W. M.
Published: May 2006

Summary

Rooted cuttings of heather showed their best dry matter production in drained regimes with a frequent addition of nutrients. Mycorrhizal plants generally showed a decreased production when compared with equivalent non‐mycorrhizal plants, except on drained regimes low in nutrients where the mycorrhizal plants grew better. Concentrations of nitrogen in the shoot and potassium and phosphorus in the root were higher in mycorrhizal than in non‐mycorrhizal plants, effects most marked in well‐drained regimes with the minimum addition of nutrients. In general, alterations in nutrient and water regimes had more significant effects on dry matter production than did the presence or absence of mycorrhiza. It is concluded that mycorrhizal infection may have a beneficial effect in freely drained, infertile, soils that are characteristic of well‐developed heathland.
THE ABSORPTION OF IONS BY MICROORGANISMS AND EXCISED ROOTS
Authors: BARBER D. A.
Published: May 2006

Summary

Micro‐organisms are present in sufficient numbers on barley roots to account for the differences previously attributed to them in experiments comparing the uptake of rubidium by sterile and non‐sterile excised roots. Experiments with thallium, which is highly phytotoxic at concentrations above 0.2 mM, provide further grounds for rejecting the postulate, based on‘dual absorption isotherms’, that under physiological conditions different mechanisms of absorption operate depending on the external concentration.
MICROBIAL ACTIVITY IN FLORIDA EVERGLADES PEAT
Authors: DICKINSON C. H. , WALLACE B. , GIVEN P. H.
Published: May 2006

Summary

Populations of viable bacteria and fungi were shown to exist in various strata of peat formed in the Florida Everglades. The populations present were quantitatively and qualitatively different in three distinct peat‐forming habitats and at various depths in the peat profiles. Relatively few pieces of peat taken from horizons below the surface were colonized by actively growing fungi or actinomycetes. Direct observation of peat confirmed some features of the cultural studies. Bacteria were mostly present in small groups of two to six cells and most of the hyphae recorded were apparently formed by Actinomycetales rather than the fungi. The significance of these data in relation to possible long‐term changes in the peats is discussed.
THE DEVELOPMENT OF CONIDIOPHORES AND CONIDIA IN THE IMPERFECT FUNGUSOEDOCEPHALUM ROSEUM
Authors: COOK BERYL E.
Published: May 2006

Summary

The development of conidiophores and botryose solitary blastospores was studied inOedocephalum roseumby light and electron microscopy, and for convenience was divided into several stages. Development was a continuous process with no pause at any stage, although increase in volume of the sporing structure was much reduced during production of the denticles. Cytochemical light microscopy supported electron microscopic observations of distribution of organelles and storage substances in the sporing structure at each stage of development. A Spitzenkörper, comprising two types of unit membrane‐bounded vesicles of different size, was present at the tip of the growing conidiophore. At the time of blow‐out of the denticles, small vesicles, thought to contain wall‐softening enzymes, accumulated in groups around the periphery of the ampulla, and the wall in these regions stretched, becoming thinner, and bulged to form the wall of the denticle initials. Exposed sulphydryl groups were detected in the wall of these bulges. The denticles grew to become tubular, and spherical conidium initials formed at their tips. Electron microscopy showed that membrane‐bounded vesicles were present in all regions of growth and development, and to the exclusion of all other organelles in the tip of the conidiophore, in denticle blow‐outs, in conidium initials and in tips of elongating conidia. In these regions much RNA was detected. The sequence of first occurrences of organelles and storage substances from the young conidiophore tip backwards was also the sequence of their entry into the developing conidia, nuclei being the last of the organelles to enter. During development and growth the wall around the whole sporing structure was not broken at any stage. However, there was a succession of wall layers in each structure during its development, new layers being formed internally and being progressively displaced towards the outside. The new inner wall layer formed by the hypha at the inception of the conidiophore gave rise to the three outer layers of the conidial wall, the inner layer of the conidium being a continuation of the inner layer of the ampulla wall, which was formed before denticle production. Blastospore formation resembled the process of budding in yeasts, in that vesicles probably containing wallsoftening enzymes were present in the region of denticle blow‐out and of budding, and the walls of the denticle and of the yeast bud were made up of parent cell wall material.
PRIMARY PENETRATION PROCESS IN POWDERY MILDEWED BARLEY RELATED TO HOST CELL AGE, CELL TYPE, AND OCCURRENCE OF BASIC STAINING MATERIAL
Authors: LIN M.‐R. , EDWARDS H. H.
Published: May 2006

Summary

The primary infection process of four near‐isogenic lines of Manchuria barley by Erysiphe graminis f. sp. hordei race CR‐3 was studied. An unknown substance,‘basic staining material’, was associated with papillae when penetration by germinated conidia was unsuccessful but not in penetrated papillae. Genes conferring resistance (ML‐a, Ml‐g, and Ml‐p) delay or reduce the frequency of penetration. The gene Ml‐k has no effect during penetration. Resistance to penetration increased significantly in both susceptible and resistant hosts with increasing cell age. The type of host epidermal cell exhibited different degrees of resistance to penetration. The cells furthest from the guard cells showed the highest degree of resistance. Guard cells were never penetrated.
AN ULTRASTRUCTURAL STUDY OF THE PYRENOID IN CULTURED CELLS OF CHLORELLA VARIEGATA (CHLOROCOCCALES)
Authors: SILVERBERG B. A. , SAWA T.
Published: May 2006

Summary

Electron microscopical examination of cultured Chlorella variegata, a facultatively heterotrophic species of the genus, revealed the presence of electron‐opaque spheres, or pyrenoglobuli, in the pyrenoid. The pyrenoglobuli, observed both in vegetative cells and autospores, are associated with the pyrenoid thylakoids which are single thylakoidal elements penetrating into the homogeneously granular matrix of the pyrenoid. There appear to be more pyrenoglobuli present in the pyrenoids without starch plates.
EFFECTS OF ROOTSTOCKS AND INTERSTOCK ON CELL DIMENSIONS IN SCION STEMS OF APPLE (MALUS PUMILA MILL.)
Authors: DOLEY D.
Published: May 2006

Summary

Fibre and vessel element dimensions were studied in Cox's Orange Pippin scion stems grafted directly on to the dwarfing M.8 and M.9 rootstocks, or on to the vigorous MM. 104 rootstock with interstocks of MM.104 or the very dwarfing M.20 varieties. In the xylem formed in trees aged between 5 and 7 years, the total cross‐sectional areas of fibres and the lumen of vessels were very closely related to the width of the growth rings. Variations in the ratio (total cell area):(lumen area) and in fibre wall thickness were mostly attributable to intrinsic seasonal effects, as reflected by the position of sampling within the growth ring. Differences in cell length and mean wall thickness of fibres between the rootstocks M.8, M.9 and MM.104/MM.104 were relatively small, whereas the M.20 interstock was associated with significantly smaller values for these attributes. The effects of the rootstocks studied appeared to be exerted through changes in the rate of stem growth as a whole, whilst the very dwarfing interstock altered the relationships between the lateral expansion of cells and the elongation and wall thickening of fibres.
NUMERIGAL METHODS IN QUATERNARY PALAEOECOLOGY
Authors: GORDON A. D. , BIRKS H. J. B.
Published: May 2006

Summary

Comparison of pollen diagrams is an important stage in pollen analytical Investigations as it is the basis for the recognition of regional pollen assemblage zones. Three numerical approaches to the problem of comparing stratigraphical sequences are presented. Their use is illustrated by two contrasting sets of data, one from two sites of Late‐Wisconsin age in central Minnesota, the other from a transect of sites in north‐west Minnesota extending from Late‐Wisconsin to present times. The first approach compares pollen zones at the different sites on two numerical criteria, information radius and concordance. The other two approaches compare sequences on a level by‐level basis; the second method by means of non‐metric multidimensional scaling and the third by a slotting procedure by which levels at one site are slotted between levels at another site on the basis of similarities in pollen composition. The advantages and disadvantages of the three approaches are discussed.
PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: BRADBEER J. W. , GYLDENHOLM A. O. , IRELAND H. M. M. , SMITH J. W. , REST J. , EDGE H. J. W.
Published: May 2006

Summary

For 14‐day‐old dark‐grown beans a quantitative study of plastid membrane formation has been made for light‐induced chloroplast development in the primary leaves. During the first 10 h of illumination, thylakoid formation resulted from the rearrangement of the membranes of the prolamellar body. De novo thylakoid formation commenced between 10 and 15 h after the beginning of illumination and resulted, in the course of 160 h of illumination, in a ten‐fold increase in thylakoid membrane. During the course of greening no cell division occurred in the mesophyll cells, plastid expansion took place in all of the mesophyll cells but plastid division only occurred in the spongy mesophyll cells to result in an 11 % increase in the plastid number of the whole leaf during the first 18 h of illumination.

When leaves were supplied with d‐threo‐chloramphenicol during greening there was a severe inhibition of thylakoid formation, vesicles were formed in the plastid stroma and rather fewer and larger grana than normal were produced. However, the proportion of thylakoid material in grana was normal. As l‐threo‐chloramphenicol yielded exactly normal chloroplasts it is concluded that thylakoid synthesis was inhibited by d‐threo‐chloramphenicol by the inhibition of the synthesis of one or more thylakoid proteins on the 708 ribosomes of the plastids.
REVERSIBLE EFFECTS OF BORON ON THE ABSORPTION AND INCORPORATION OF PHOSPHATE IN VICIA FABAL.
Authors: ROBERTSON G. A. , LOUGHMAN B. C.
Published: May 2006

Summary

Boron deficiency reduced absorption of phosphate in whole plants and root segments of Vicia faba. The overall phosphate metabolism of the whole root was unaffected but both the equilibrium pattern and initial rates of esterification were altered in the root tip region. The equilibrium ratio of inorganic phosphate to organic phosphate was not affected. Addition of boron at 10 μM to the deficient plants for 1‐2 h prior to absorption reversed the effects of boron deficiency in both absorption and metabolism of phosphate although it did not stimulate the initial rates of esterification of the absorbed phosphate.
THE EFFECT OF KINETIN AND ABSCISIC ACID ON WATER AND ION TRANSPORT IN ISOLATED MAIZE ROOTS
Authors: COLLINS J. C. , KERRIGAN A. P.
Published: May 2006

Summary

Exudation from the xylem of excised maize roots was studied in roots bathed in solutions containing kinetin or abscisic acid (ABA). Kinetin reduced the water permeability of the roots whilst ABA increased it. The action of both hormones was reversible and both were effective at concentrations of 10‐6M and below. The possible in vivo role of these two hormones is discussed.
EFFECT OF KINETIN ON PLANT‐RESPONSE TO SALINITY
Authors: BENZIONI A. , MIZRAHI Y. , RICHMOND A. E.
Published: May 2006

Summary

Kinetin applied to tobacco plants had a marked dwarfing effect and, in suitable concentration, prevented the appearance of saline‐induced leaf‐necrosis. In experiments lasting for 24 h, kinetin effected a reduction of salt transport from the roots to the shoot, without affecting salt uptake. However, Na+ and Cl‐ analysis of plants exposed to 6 weeks of salination revealed that kinetin accentuated salt accumulation in the shoot and thus the necrosis‐prevention effect of kinetin did not stem from retardation of salt accumulation in the plant. It is suggested that the effect of salinity on leaf‐necrosis was related to its effect on acceleration of leaf senescence and that kinetin prevented salinity damage by retarding cellular senescence and breakdown.
CHARACTERIZATION OF EUCALYPT MYCORRHIZAS BY PYROLYSIS–GAS CHROMATOGRAPHY
Authors: SEVIOUR R. J. , CHILVERS G. A. , CROW W. D.
Published: May 2006

Summary

The chemotaxonomic potential of pyrolysis–gas chromatography is evaluated in relation to eucalypt mycorrhizas. The sensitivity of the technique permits good elution patterns to be obtained even from samples as small as single mycorrhizal apices. A simple quantitative measure of dissimilarity between such pyrograms, based on heirarchical analysis of peak heights, is described. Dissimilarity measures obtained from comparisons between defined materials are shown to be correlated with their degree of taxonomic affinity but experimental variability between replicate samples currently limits the comparative value of this method.
INTERGENERIC HYBRIDIZATION AMONG THREE SPECIES OF HETERANTHELIUM, EREMOPYRUM AND HORDEUM, AND ITS SIGNIFICANCE FOR THE GENETIC RELATIONSHIPS WITHIN THE TRIBE TRITICEAE*
Authors: SAKAMOTO SADAO
Published: May 2006

Summary

Heteranthelium is a monotypic genus in the tribe Triticeae represented by an annual diploid species, H. piliferum. The spike of this species is quite different from other members of the tribe. In an attempt to elucidate the genetic relationships to other genera of the tribe, H. piliferum was crossed with various species of Aegilops, Agropyron, Eremopyrum, Henrardia and Hordeum.

From these crosses F1 hybrids of (i) Heteranthelium piliferum (2x) ×Eremopyrum bonaepartis (2x) and (2) Heteranthelium piliferum×Hordeum depressum (4x) were produced. At the same time F1 hybrids of (3) Eremopyrum bonaepartis×Hordeum depressum was also obtained. The hybrid under (i) showed subnormal growth and the shape of the spikes was of Eremopyrum type, while the spikelets were intermediate. Growth of the hybrid under (2) was vigorous and the spike morphology was intermediate between the parents. A solitary spikelet with two glumes and a single spikelet at each rachis node like the Heteranthelium parent was observed but no rudimental spikelets which are the characteristic of Heteranthelium were found.

Growth of the hybrid under (3) was very vigorous and the shape of the spikes was of Hordeum type. However, floral construction at each rachis node was very complicated. Rachis nodes with three glumes and a single spikelet were the most common. Sterility of all three combinations was complete.

Average chromosome pairing per cell of the F, hybrids was in (i) 0.04 bivalents and 13.93 univalents, in (2) 0.00 trivalents, 5.06 bivalents and 10.88 univalents, and in (3) 0.00 quadrivalents, 0.01 trivalents, 5.50 bivalents and 9.97 univalents. Judging from the chromosome pairing in (i), (2) and (3), a high bivalent formation in (2) and (3) is attributable to autosyndesis of chromosomes derived from the Hordeum parent. It is concluded that there is no homology among the genomes of those three species.

Considering morphological features, geographical distribution, intergeneric cross‐ability and genetic relationships of Heteranthelium piliferum, it is concluded that the monotypic genus Heteranthelium is a distinct entity in the tribe Triticeae. This taxon has evolved as an annual during the process of adaptation to rather dry habitats of the Mediterranean climatic regions in the course of generic differentiation of the tribe.
A STATIC NON‐OVERLOAD POLLEN COLLECTOR
Authors: TAUBER HENRIK
Published: May 2006

Summary

A static pollen collector developed for unpowered field operation was subjected to wind tunnel tests to assess its sampling efficiency for a range of pollen sizes and varying wind velocities. The pollen collector and the testing procedure is described. It was found that the catch of particles is independent of whether the collector is operated with or without a roof. Within experimental errors the collection of pollen and spores is proportional to the orifice area. The collection efficiencies vary somewhat with size of pollen grains and with wind velocity, but in most cases less so than would be the case with a static sampler operated by impaction. At wind velocities around 2 m/s, which is close to average natural wind speeds in the lower atmosphere in forested areas, collection efficiencies thus are the same for big and small pollen grains. The overall efficiency of the collector is low, as is always the case with an unpowered collector that operates mainly by gravity settling. In return, the collector is designed to give a smooth flow of air over the orifice at all wind velocities and therefore a fairly predictable catch of pollen grains with varying conditions.
GROSS CHEMICAL CHANGES OCCURRING IN THE LEAF OF SIN APIS ALBA DURING PHOTOPERIODIC INDUCTION OF FLOWERING
Authors: KINET J. M.
Published: May 2006

Vegetative plants of Sinapis alba L. were induced to flower by exposure to a single 22‐h long day. At various time intervals after the start of the inductive treatment, leaves were collected and their gross chemical composition analysed. Chlorophyll and RNA contents were determined spectrophotometrically, starch content was determined by means of the anthronc method, proteins by the biuret method and DNA using the diphenylamine reaction. No change was found in fresh weight, chlorophyll, RNA and DNA contents of leaves of induced plants. There was, however, a tremendous increase in dry weight, starch, and protein contents of these leaves, culminating around 3.0 h after the start of the long day. The significance of these events is discussed in relation to photoperiodic induction in Sinapis.
ULTRASTRUCTURE OF THE INTERACTION BETWEEN PHYTOPHTHORA INFESTANS AND LEAVES OF TWO CULTIVARS OF POTATO (SOLANUM TUBEROSUM L.) ORION AND MAJESTIC
Authors: SHIMONY CARMELA , FRIEND JOHN
Published: May 2006

Electron microscopy was used to follow the course of infection of leaves of a susceptible (Majestic‐r) and a resistant (Orion‐R1) potato variety by Phytophthora infestans (race 4). Shortly after penetration, an infection vesicle was formed in both varieties but the subsequent stages of infection differed. In Majestic, hyphae spread both intra‐and intercellularly and even 48 h after inoculation there were still juvenile‐type hyphae inside mesophyll cells which appeared undamaged. In Orion juvenile parts of hyphae were not seen in or near intact cells later than 7–12 h after inoculation. Orion cells died at an early stage, but death of the fungus only occurred more than 12 h after inoculation.

These results are discussed in relation to current hypotheses concerning hypersensitivity and it is suggested that a toxin is produced by the interaction of the fungus with Orion.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDR YP HI ELLA SALINA V. THE PATTERN OF LABEL IN ARABITOL AND POLYSACCHARIDE AFTER GROWTH IN THE PRESENCE OF SPECIFICALLY LABELLED CARBON SOURCES
Authors: LOWE D. A. , JENNINGS D. H.
Published: May 2006

Dendryphiella salina was grown in a sea‐water nitrate medium with the following specifically labelled carbon sources: [1‐14C]‐, [2‐14C]‐, [6‐14C]‐glucose, [1‐14C]‐ribose and [1‐14C]‐glycerol. The data for distribution of 14C in polysaccharide hydrolysable with 1.0 N H2SO4 indicate that much of it is produced directly from glucose but there is confirmation of other studies that some is synthesized from mannitol. The distribution of label in arabitol is consistent with synthesis from ribose via xylulose. High activity is consistently found in carbon 3 of arabitol which is only explicable in terms of randomization in glycerol and the transketolase exchange reaction previously demonstrated to occur in rat liver.
THE EXTENSION ZONE OF STAGE I SPORANGIOPHORES OF PHYCOMYCES BLAKESLEEANUS
Authors: TRINCI A. P. J. , HALFORD ELIZABETH A.
Published: May 2006

The length of the extension zone of stage I sporangiophores of Phycomyces blakesleeanus was determined from measurements of the apical region which responded phototropically to unilateral illumination; the extension zone varied in length from 50 to 950 μm. A significant relationship was observed between extension zone length and growth rate. The length of the extension zone of the sporangiophores could also be determined by measuring the length of the tapered region of their tips.
EFFECT OF LIGHT ON ASCOSPORE DISCHARGE BY FIVE FUNGI WITH BITUNICATE ASCI
Authors: BROOK P. J.
Published: May 2006

Experiments on ascospore discharge from naturally developed perithecia were conducted in a wind tunnel. Discharge by Venturia pirina, V. rumicis and Venturia sp. was stimulated by light, particularly by red, but also by green and blue. There was always a sharp decline in discharge rate after perithecia of these species and of V. inaequalis were plunged from light into darkness. In V. inaequalis a high rate of discharge persisted for several minutes after the change to darkness. It is postulated that in these bitunicate fungi a photoreaction is involved in the rupture of the exoascus tip.

Coleroa circinans, another bitunicate species, discharged its ascospores equally readily in light and darkness.
MOVEMENT OF ETHYLENE FROM ROOTS TO SHOOTS, A FACTOR IN THE RESPONSES OF TOMATO PLANTS TO WATERLOGGED SOIL CONDITIONS
Authors: JACKSON MICHAEL B. , CAMPBELL D. JOAN
Published: May 2006

Epinastic growth by petioles of tomato (Lycopersicon esculentum Mill., cv. Moneymaker) is stimulated by waterlogging the soil and the responding leaves and other shoot parts contain higher concentrations of ethylene than those of non‐waterlogged plants. Waterlogged soil also contains increased amounts of ethylene in solution and the possibility that ethylene from this source can move to the shoots of waterlogged plants has been tested by applying the gas to the roots of plants growing in water culture. When concentrations of 2 ppm and above are supplied in this way, petiole epinasty develops in association with increases in ethylene extracted from the responding petioles. When 100 ppm is applied to the roots, increases in ethylene in the petioles precede the development of epinastic growth. Use of [14C] labelled ethylene indicates that the gas can move rapidly, unchanged from roots to shoots. The movement of ethylene and epinastic growth are both reduced if plants are previously steam‐girdled near the base of the stem, suggesting that much ethylene moves by a route other than the transpiration stream. Ethylene supplied to the roots is shown to promote adventitious rooting and downward rolling of the young leaf laminae and to modify the orientation of shoot growth in the tomato mutant‘diageotropica’.

It is proposed that increases in soil ethylene and movement of the gas to the shoot system are factors contributing to the development of epinasty and other responses of the shoots to waterlogging the soil.
CHLOROPLAST STRUCTURE IN COILED AND UNCOILING CROZIERS OF PILULARIA GLOBULIFERA
Authors: WHATLEY JEAN M.
Published: May 2006

The sequence of development of chloroplasts in coiled and newly uncoiled croziers of Pilularia globulifera L. is described. Changes in chloroplast shape and lamellar orientation could be correlated with particular states of crozier coiling or unfolding.