bluuebunny/crossref_metadata_2025_split huggingface dataset:
EARLY‐AND MID‐FLANDRIAN ENVIRONMENTAL HISTORY OF THE BRECON BEACONS, SOUTH WALES
Authors: WALKER M. J. C. 
Published: May 2006

SUMMARYPollen‐stratigraphic data are described from two sites on the northern face of the Brecon Beacons escarpment in South Wales, U.K. Pollen percentage, pollen concentration and deteriorated pollen diagrams are presented which contain details of vegetational changes in this part of Britain from the time period immediately following the wastage of the Loch Lomond Advance glaciers around 10000 radiocarbon years ago, until the establishment of oak and alder woodland in the mid‐ Flandrian some 4000 years later. An initial phase of juniper scrub was followed by the expansion of birch woodland over much of the area, and these forests were subsequently invaded by large numbers of hazel. Quercus, Ulmus and Pinus were present throughout the mid‐Flandrian, but increasing climatic wetness, possibly beginning around 7000 radiocarbon years ago, led to the decline of elm, pine and birch as woodland components in this part of South Wales, and to the expansion of Quercus and particularly Alnus. These vegetational changes are discussed in terms of vegetational developments at other sites in upland Wales and western Britain.
POTENTIATION OF SULPHUR DIOXIDE INDUCED INHIBITION OF PROTEIN SYNTHESIS BY DESICCATION
Authors: OKOLOKO G. E. , BEWLEY J. DEREK 
Published: May 2006

SUMMARY In vivo protein synthesis in the gametophyte apices of Tortula ruralis (Hedw.) Gaertn, Meyer and Scherb was studied in relation to desiccation and sulphur dioxide stress. The latter was applied in aqueous form, at three levels (0.1, 0.5 and 1.0 mol m−3), while two drying regimes (slow and rapid) were employed. Desiccation by itself caused only a slight inhibition of protein synthesis following 30 min rehydration. SO2 at 0.1 mol m−3 was stimulatory to protein synthesis when applied alone (20%) or in combination with slow desiccation (14%). Combining 0.1 mol m−3 SO2 with rapid desiccation not only abolished this stimulation but further reduced protein synthesis to 70% of control. SO2 at both 0.5 and 1.0 mol m−3 was inhibitory to protein synthesis in the absence of desiccation. Desiccation applied after pretreatment in 0.5 mol m−3 and 1.0 mol m−3 SO2 caused a potentiation of SO2 inhibition, rapid desiccation having a stronger effect in this regard than slow desiccation.
TRANSPORT, TRANSLOCATION AND METABOLISM OF 14C‐PHOTOSYNTHATES AT THE HOST‐PARASITE INTERFACE OF PISUMSATIVUM AND ERYSIPHE PISI
Authors: MANNERS J. M. , GAY J. L. 
Published: May 2006

SUMMARYHaustorial complex, mycelial and host (leaf without mycelia) samples were obtained from leaves of Pisum sativum infected with Erysiphe pisi either immediately following a 20 min exposure to 14CO2 (‘pulse’) or after a further 20 h ‘chase’ in 12CO2. After the ‘pulse’, labelled ethanol‐soluble sugars (glucose, fructose and sucrose) and mannitol predominated in the host and mycelial fractions respectively and lipids (mainly triglycerides) and an ethanol‐insoluble glucan (not α‐1, 4 linked) contained most of the 14C in the haustorial complexes. Ethanol‐soluble carbohydrates contained only 3% of the total 14C in the haustorial complexes with sucrose and glycerol as the major components. After the ‘chase’, the total 14C in host and mycelium declined but the proportions in starch or glycogen, protein, cell wall and nucleic acid fractions increased. Total 14C in haustorial complexes increased but that contained in sucrose and glycerol decreased and that in mannitol increased. During both ‘pulse’ and ‘chase’, the quantity of 14C in the haustorial complexes was small compared with that in the mycelial and leaf fractions.These results indicate that transport of host sugars to the fungus is mediated by haustoria. Sucrose and glycerol are either translocates or metabolic intermediates in this process and mannitol is the major primary sink of the fungus. Glycogen and other macromolecules are produced at a later stage in the fungus. Polysaccharides and lipids are important sinks at the host‐haustorial interface. These results are discussed in relation to the regulation of transport at the host‐parasite interface.
Studies ON MUCORALEAN MYCOPARASITES
Authors: EVANS G. H. , COOKE R. C. 
Published: May 2006

SUMMARYDiffusible, non‐volatile factors from hyphae of Mortierella vinacea and Mycotypha microspora directed growth of Piptocephalis fimbriata germ tubes towards them. Such factors were also present in Y‐phase cells of Mycotypha microspora but were not released from them. They were absent from hyphae of Circinella mucoroides which was nevertheless susceptible to attack by Piptocephalis fimbriata. Growth‐directing factors were extracted from sporelings of Mortierella vinacea and partially characterized. They were hydrophilic, thermo‐labile, positively charged and appeared to be either proteinaceous or bound to proteins. The consequences of directed growth of Piptocephalis fimbriata towards its hosts are discussed in relation to the process of mycoparasitism.
COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.
Authors: LACK ANDREW J. 
Published: May 2006

SUMMARYIf competition for pollinators is an important influence on populations of Centaurea scabiosa and C. nigra sensu lato one of the characters most likely to be affected is flowering time. Observations were made on the flowering period of several populations of the two species growing sympatrically and in isolation, and on plants from these and further populations transplanted into the Botanic Garden.Conclusions from the study are:

Where C. scabiosa and C. nigra grow sympatrically, C. nigra flowers slightly later than C. scabiosa but there is a considerable period of overlap.
Populations of C. scabiosa differ slightly in flowering time, but there are large differences between C. nigra populations growing in isolation from C. scabiosa.
In many populations of both species there are large differences in flowering time between individuals.
The differences observed between plants in the field are maintained in cultivation.
Small differences are apparent between years and between aspects.

The large range of flowering time seen in C. nigra may be partly attributable to differences between ssp. nigra and ssp. nemoralis and hybridization between them, but local ecological factors are important influences on some populations. Competition for pollinators between C. scabiosa and C. nigra may maintain the difference in flowering time between the two species in some areas.
THE LATE DEVENSIAN VEGETATIONAL HISTORY OF THE WHITLAW MOSSES, SOUTHEAST SCOTLAND
Authors: WEBB J. A. , MOORE P. D. 
Published: May 2006

SUMMARYLate Devensian Late‐glacial deposits are described from the Whitlaw Mosses, near Melrose, Roxburghshire (now Borders). Pollen diagrams and macro fossil lists are given for the bottom sediments of Beanrig Moss and Blackpool Moss, two small fens lying in hollows in the undulating boulder clay of Tweeddale. The succession of taxa through the sediments indicates interstadial conditions followed by stadial conditions.Critical determinations of certain microfossil and macrofossil indicator taxa, permits the identification of certain plant communities. These are as follows: Communities identified from within the stadial are;(1) bare‐ground communities of open, wind‐exposed areas with Artemisia cf. norvegica and Papaver spp. of the section scapiflora as the main indicator types;(2) bare‐ground communities in sheltered areas of long snow‐lie with such species as Salix herbacea, Polytrichum norvegicum and P. alpinum.The main communities identified in the interstadial are as follows:(1) scrub with abundant Juniperus and sparse tree birches (e.g. B. pubescens);(2) base‐rich, well‐drained short turf with abundant Helianthemum;(3) damp, tall‐herb meadows in which Rumex acetosa is important;(4) dwarf‐shrub heath with Dryas octopetala and Betula nana;(5) open‐ground communities with Artemisia spp. and Hippophaë.Communities identified from both the stadial and interstadial are:(1) short‐turf calcareous flushes or springs with Selaginella and various mosses;(2) fens and marshy lake margins with, e.g. Homalothecium nitens.Several taxa have not hitherto been found in the Late Devensian of the British Isles, amongst which are Artemisia cf. campestris, A. sect. dracunculus, A. cf. maritima s.l., Gypsophila repens/fastigiata, Hedysarum cf. hedysaroides, Minuartia rubella, Rhacomitrium cf. canescens and Vactinium vitis‐idaea. The identification of the pollen grains and macro fossils is discussed and comments are made on the biogeographical and ecological implications of the records, especially of those species which are now no longer part of the British flora.
EVALUATION OF PUTRESCINE AS A BIOCHEMICAL INDICATOR OF THE POTASSIUM REQUIREMENTS OF LUCERNE
Authors: SMITH G. S. , LAUREN D. R. , CORNFORTH I. S. , AGNEW M. P. 
Published: May 2006

SUMMARYThe diamine putrescine was found to be a sensitive indicator of potassium requirements of lucerne. There was an inverse relationship between the concentration of putrescine and that of potassium and the lowest concentrations of putrescine occurred only in plants which produced in excess of 90 % of the maximum dry matter yield. Using the point where the concentration of putrescine reached a minimum as an indication of healthy growth, it was established that a potassium concentration of 3 % of the dry matter of the leaves would be required for optimum dry matter production of lucerne at the early bloom stage of development; the corresponding value in the stem was estimated to be 5 % of the dry matter. While a low supply of magnesium enhanced the accumulation of putrescine in potassium deficient plants, potassium was shown to be the major factor influencing the concentration of putrescine. The advantages of using the concentration of putrescine as a basis for estimating the potassium requirements of lucerne are discussed in relation to the difficulties encountered with the conventional critical levels concept.
COMPARISONS BETWEEN THE GROWTH RATES OF MYCORRHIZAS, UNINFECTED ROOTS AND A MYCORRHIZAL FUNGUS OF EUCALYPTUS ST‐JO HNII R. T. BAK
Authors: CHILVERS G. A. , GUST L. W. 
Published: May 2006

SUMMARYOn soil‐grown seedlings in pots, and on pure‐cultured seedlings in bottles, mycorrhizas grew at approximately one‐fifth the rate of equivalent uninfected apices. It was seen in bottle cultures that, because the growth rates of primary and secondary roots usually exceeded the growth rate of the fungus, only a few of these apices came into contact with the inoculum. The slower growth rate, later appearance and the positioning of tertiary root apices, led to many of these becoming invested by fungal mycelium and a considerable proportion of them became converted to mycorrhizas. Mycorrhizal apices were seen to remain active for longer periods, and to grow at more constant rates, than uninfected apices. Possible reasons for this are discussed.
FACTORS AFFECTING BUD INDUCTION IN THE MOSS HYOPHILA INVOLUTA
Authors: RAHBAR KAVITA , CHOPRA R. N. 
Published: May 2006

SUMMARYProtonema of Hyophila involuta remains bud‐free on basal medium (Knop's Major and Nitsch's Minor salts). Auxins, gibberellic acid, abscisic acid, chelates, vitamin B12, activated charcoal, coconut milk; and altered hydration, pH, temperature, light intensity and duration do not induce buds. Cytokinins initiate multicellular gemmae on the protonema. Buds are induced only by the interaction of IAA with kinetin or DMAAP, and these develop into normal gametophores.
PRODUCTION OF HAPLOID PLANTS FROM ANTHER CULTURES AND SECONDARY EMBRYOIDS OF WINTER OILSEED RAPE, BRASSICA NAPUS SSP. OLEIFERA
Authors: CHIANG SHIONG LOH , INGRAM D. S. 
Published: May 2006

SUMMARYFollowing anther culture of a range of cultivars of winter oilseed rape, Brassica napus ssp. oleifera, approximately 15 to 70 % of the resulting embryoids developed directly into plants. The rest grew abnormally in culture, giving rise to abnormal plantlets which formed large numbers of secondary embryoids on their surfaces (up to 100 per abnormal plantlet). The secondary embryogenic plantlets were haploid, and the secondary embryogenic potential was maintained for over a year in culture without diminution. More than 70% of the secondary embryoids, and the plants regenerated from them, were haploid. These results are discussed in connection with the possibility of producing large numbers of haploid plants throughout the year for breeding purposes and for the production of novel disease resistant plants through genetic manipulation in culture.
CRYSTALLINE STRUCTURE OF PLANT EPICUTICULAR WAXES DEMONSTRATED BY CRYOSTAGE SCANNING ELECTRON MICROSCOPY
Authors: JEFFREE C. E. , SANDFORD A. P. 
Published: May 2006

SUMMARYThe epicuticular wax structure of several species was investigated, using plant material frozen rapidly in liquid nitrogen, and observed by means of a cryogenic specimen stage fitted to a scanning electron microscope. The wax was found to have a crystalline fine structure identical with that observed using conventional techniques for the preparation of plant surface specimens for transmission and scanning electron microscopy. The findings are discussed in relation to recent reports that the waxes are amorphous at low temperatures, and that the generally‐accepted crystalline fine structure of plant epicuticular waxes is an artefact of conventional specimen preparation procedures.
NIACIN BIOSYNTHESIS IN LEAF DISCS AND SEEDLINGS OF CATTLEYA SKINNERI (ORCHIDACEAE)
Authors: COOPER JAN L. , HILTON BRENDA L. , ARDITTI JOSEPH , TARR JOHN B. 
Published: May 2006

SummarySeedlings and leaf discs of Cattleya skinneri incorporated label from 14C‐ and 3H‐labelled tryptophan into niacin. Label from [14C]glycerol and[14C]aspartate was not significantly incorporated into the vitamin.
THE ROLE OF ORGANIC ACIDS IN ZINC TOLERANCE IN DESCHAMPSIA CAESPITOSA
Authors: THURMAN D. A. , RANKIN J. L. 
Published: May 2006

SummaryThe relationship between metal tolerance and accumulation of organic acids has been investigated using zinc‐cadmium tolerant and non‐tolerant clones of Deschampsia caespitosa. Zinc significantly increased citrate and malate levels in the roots of the tolerant clone but had no significant effect on the levels of these acids in the roots of the non‐tolerant clone. Cobalt, copper, mercury and nickel had no significant effect on the levels of these acids in either clone. A number of enzymes involved in organic metabolism were extracted from the roots of the two clones, but no difference in their sensitivities to zinc was found. Changing the citrate levels in the roots by growing plants under different iron regimes did not change tolerance indices. Grown in the presence of zinc, both clones contained enough citrate and malate to complex only approximately half of the zinc present in their roots.
PHYTOLECTINS FROM THE NITROGEN‐FIXING LICHEN PELTIGERA HORIZONTALIS: THE BINDING PATTERN OF PRIMARY PROTEIN EXTRACT
Authors: PETIT PATRICE 
Published: May 2006

SummaryA protein fraction containing phytolectins was isolated from the nitrogen‐fixing lichen Peltigera horizontalis. These lectins were thermostable, truly non‐specific and were more effective on human erythrocytes A, B and O than concanavalin A. Phytolectins originate from the mycobiont and do not bind any of the freshly isolated phycobionts tested, but with slight differences bind the cultured phycobionts isolated from three Peltigera spp. It is suggested that the production of phytolectins may be characteristic of the lichen symbiosis and that they may be involved in the recognition or initial interactions between compatible lichen symbionts.
CHANGES IN CELL POPULATION KINETICS IN AN OPEN MERISTEM DURING ROOT GROWTH
Authors: CLOWES F. A. L. 
Published: May 2006

SummaryThe problem of root meristems, previously considered to exchange cells between the stele and the cap as well as between cortex and cap, has been solved by using DNA‐labelling and stathmokinetic methods to observe the change in behaviour of the meristem as the primary root ages in Cucurbita pepo L.The stelar pole is quiescent and can contribute few, if any, cells to the cap. During early growth the tiers of cells of the columella meristem are intermittently quiescent and active. This causes the highest average rate of mitosis in the cap to occur in a tier of the columella that is not adjacent to the stelar pole. It also interrupts the patterns of cells in the columella to form up to four complexes of cells along its length. As the root ages, rates of mitosis become generally lower, except in the quiescent stelar pole, and fewer tiers of the columella stay meristematic. The proximal tier of the columella, adjacent to the stelar pole, now acquires the highest rate of mitosis in the meristem. This simplifies the columella pattern, but the meristem never becomes closed because no quiescent buffer establishes itself between the stele and the central cap meristem and so a boundary between the cortex and peripheral cap meristems never becomes stabilized.
THE GENETIC CONTROL OF A NON‐RADIATE CONDITION IN SENECIO SQUALIDUS L. AND SOME OBSERVATIONS ON THE ROLE OF RAY FLORETS IN THE COMPOSITAE
Authors: INGRAM RUTH , TAYLOR LYNN 
Published: May 2006

SummaryThe genetic control of a non‐radiate mutant of Senecio squalidus has been found to be identical with the genetic control of the non‐radiate character in S. vulgaris. The biological effects of the same gene in the two species are discussed. The morphology of the radiate florets in the heterozygotes of 5. squalidus has been investigated, and some implications for the evolution of protogyny are discussed.
ULTRASTRUCTURE OF TALL FESCUE (FESTUCA ARUNDINACEA SCHREB. CV. S170) CELLS FIXED WHILE EXPOSED TO LETHAL OR NON‐LETHAL EXTRACELLULAR FREEZING
Authors: PEARCE R. S. 
Published: May 2006

SUMMARYA freeze‐substitution method was used to fix tissues (from roots, leaf laminae and leaf meristem of tall fescue) subjected to lethal or non‐lethal extracellular freezing, which induced intracellular dehydration. There was no evidence of direct (tearing) damage by extracellular ice. In the tissues fixed while so frozen, the cytoplasm was coherent and the plasmalemma was present but the trilamellar structure of membranes was not always evident, e.g. it was usual in thylakoid membranes but was rare in the peripheral membranes of chloroplasts. An abnormal feature was the presence of strongly osmiophilic material, often associated with membranous structures and possibly of more than one type. The appearance of the frozen tissues and the amount of strongly osmiophilic material did not vary with hardiness. When a lethal freezing treatment was given, strongly osmiophilic material occurred at the same sites in both frozen and thawed tissues, but it was largely absent from thawed non‐lethally frozen tissues, though present in the same material before thawing. The occurrence of intact plasmalemmata in tissues fixed while lethally frozen and of strongly osmiophilic material in tissues fixed while non‐lethally frozen, are in contrast to some other recent work.
ROOT CONTRACTION IN TRANSPIRING PLANTS
Authors: FAIZ S. M. A. , WEATHERLEY P. E. 
Published: May 2006

SUMMARYExperimental data published previously (Faiz and Weatherley, 1977) emphasized the existence of considerable hydraulic resistance in the perirhizal soil of rapidly transpiring plants. This was evident when soil water potential (Ψs in the root zone was as high as −2 or −3 bars. In a further paper (Faiz and Weatherley, 1978) the hypothesis was put forward that it is the soil‐root interface which presents a high resistance to the flow of water through the soil‐plant system. This resistance, it was thought, could increase as a result of contraction of stressed‐roots, with the formation of vapour gaps between soil and root.In this paper we demonstrate that the root tissues may contract by as much as 25 % of their turgid volume when the water potential of the leaves (Ψl) falls to around −15 bars. Under such conditions the extensive formation of vapour gaps would be expected and a reduction of water stress should therefore follow if the gaps could be closed mechanically. Such closure was attempted by either squeezing or vibrating the soil mass containing the root system. Both of these treatments led to a temporary reduction in water stress in the plants and the existence of vapour gaps was thus supported.
EFFECT OF LOCAL CONCENTRATIONS OF ACETIC ACID AROUND BARLEY ROOTS ON SEEDLING GROWTH
Authors: GUSSIN E. J. , LYNCH J. M. 
Published: May 2006

SUMMARYAcetic acid was applied to localized regions of barley roots. Treating a single root tip with a small concentration (5 mol m−3) of the acid stimulated root and shoot growth. No stimulation was observed when more than one root was treated or with greater concentrations of the acid. Treating 2 cm lengths along the root axis distal to the root tip region (2 cm long) gave a greater inhibitory effect on root and shoot growth than the corresponding root tip treatment. Treatment of tips and 2 cm lengths resulted in some compensatory growth in the non‐treated roots.
RELATIVE PERFORMANCE OF CONIFER POPULATIONS IN VARIOUS TESTS FOR SENSTIVITY TO SO2, AND THE IMPLICATIONS FOR SELECTING TREES FOR PLANTING IN POLLUTED AREAS
Authors: GARSED S. G. , RUTTER A. J. 
Published: May 2006

SUMMARYThe sensitivity of five Pinus and three Picea populations to SO2 was compared in various types of fumigation experiment (i) > 9 months at 200 μg m−3, (ii) 6 h at 8000 μ m−3, (iii) 9 weeks at 800 μg m−3, (iv) 12 h (overnight) at 17 000 μg m−3 preceded by either 42 days or 6 h at 800 μg m−3. To complement the fumigation experiments the growth of four of the populations was compared at a polluted (London) and a control site (Silwood Park).There was no relationship between the relative sensitivity of the populations to 200 μg m−3(measured as relative growth rate) and the degree of acute injury at 8000 μg m−3. In general the populations of Picea were more sensitive to low concentrations of SO2 but more resistant to acute injury than those of Pinus. At 800 μg m−3 the initial symptoms were of acute injury, but later whole needles died and were shed. Populations prone to the initial injury were not necessarily sensitive to the later type, and vice versa.Leaf fall was accelerated and dry wt gain depressed at the polluted site compared with the control and these effects were much greater in Picea than in Pinus populations.It is concluded that the order of sensitivity obtained in screening experiments depends largely on the conditions used, and that short‐term experiments with high concentrations of SO2 cannot be used to predict the responses of conifers to low concentrations of SO2 in the field.