bluuebunny/crossref_metadata_2025_split huggingface dataset:
TERNEUZEN AND BURIED FORESTS OF THE EAST ANGLIAN FENLAND
Authors: GODWIN H. 
Published: May 2006

SummaryAt Terneuzen in south‐west Holland, Munaut has described a buried pine forest overgrown by Sphagnum bog. Dendrochronology has shown the forest to be a single generation stand lasting for 300 years or so, and radiocarbon measurement has given it a date between about 2600 and 2300 B.C. These conclusions and associated pollen analyses are here considered in relation to palaeoecological and geological studies in comparable deposits in coastal Britain, especially in the East Anglian Fenland. The natural ecological status of the yew (Taxus baccata) and the pine (Pinus sylvestris) are seen to be similar in these sites, and the role of the latter in the induction of raised bog is clarified.
THE EFFECTS OF PHOTOPERIOD AND NIGHT TEMPERATURE ON FLOWERING AND GROWTH IN SOME AFRICAN TRIFOLIUM SPECIES
Authors: MANNETJE L. 'T , PRITCHARD A. J. 
Published: May 2006

SummaryThirteen species and varieties of African Trifolium were used in a glasshouse and a phytotron experiment to determine their flowering behaviour. T. baccarinii, T. pseudostriatum and T. usambarense behaved as sensitive short‐day plants and T. burchellianum var, burchellianum and T. africanum behaved as sensitive long‐day plants. The other species were either day‐neutral or could not be clearly classified because of strong eflfects of night temperature on flowering. Conditions favourable for flowering were usually also best for growth except in the case of some species which did not flower at certain photoperiods.
THE LATE‐ AND POST‐GLACIAL HISTORY OF THE GORDANO VALLEY, NORTH SOMERSET
Authors: JEFFERIES R. L. , WILLIS A. J. , YEMM E. W. 
Published: May 2006

SummaryThe stratigraphy and palaeobotany of the Late‐glacial and Post‐glacial deposits in the Gordano valley, North Somerset, have been investigated. At the west end of the valley there is a lake basin which is cut off from the east end by a transverse sand bar. This bar appears to have prevented the sea from penetrating to the head of the valley during the main eustatic rise in sea level. The local conditions have allowed peat formation from Late‐glacial times in the basin which contains a record of vegetational history not hitherto recorded in Somerset. In the Somerset Levels the pre‐Atlantic peat deposits are either out of reach beneath estuarine clays or have been eroded away.During the Late‐glacial period the vegetation present in the Gordano valley was the same type of open herbaceous calcicolous vegetation recorded elsewhere in southern Britain. The pollen record from the profiles further shows that the Middle and Late Boreal stages of forest development are also similar to those in other parts of southern Britain. The main phase of peat formation in the Gordano valley dates from the onset of the Atlantic period. The upper peat layers are indicative of the establishment of fen communities and not raised bog as occurred in parts of the Somerset Levels. Peat which is representative of Zone VIII is missing, partly on account of human activities but also because the sea entered the east end of the valley during the Romano‐British marine transgression.
CHANGES IN GROWTH AND METABOLISM OF EXCISED PEA ROOTS ASSOCIATED WITH IRON DEFICIENCY
Authors: ABBOTT A. J. 
Published: May 2006

SummaryThe effects of iron deficiency on the growth and metabolism of isolated pea roots grown in sterile culture have been analysed. Changes were followed in whole routs sampled at intervals and in successive sections of roots sampled at a critical stage of deficiency. Transfer of deficient roots to complete nutrient after varying periods in the absence of iron showed the growth restriction was reversible for at least 6 days. Results suggest that the complete cessation of cell division after 6 days in iron‐deficient culture was due primarily to a disturbance localized in the apical meristematic cells. Changes which occurred in the levels of protein nitrogen, ethanol‐soluble nitrogen, amino acids, soluble carbohydrates and respiration are mainly attributed to the cessation of cell division rather than the cause of it. The rate of cell expansion was unaffected by iron deficiency but the final size of mature cells was reduced. Addition of iron to deficient roots stimulated cell division more rapidly than protein synthesis or respiration rate. Insofar as the serial‐sectioning technique used enabled separation to be made of cell division and cell enlargement, the results suggest that the effect of iron deficiency is confined primarily to the former. In addition, the final phase of cell maturation may also be affected but the evidence was inconclusive and these effects may not be determined directly by depletion of the iron supply. Evidence is presented showing that the metabolic changes associated with the transition from cell division through cell expansion to cell maturation depend on the source of root inocula used. Seedling roots showed marked changes in metabolism and meristem size when first isolated due to the depletion of metabolites translocated from the germinated seed, and it was necessary to use inocula taken from cultured excised roots to provide valid data on the changes due to increasing cell age.
HEMIPARASITIC NUTRITION IN ANGIOSPERMS
Authors: GOVIER R. N. , BROWN J. G. S. , PATE J. S. 
Published: May 2006

SummaryThe structure of the root haustorium and the hairs of the shoot of Odontites has been examined by light microscopy. The haustorium provides a direct xylem‐xylem link between root of host and hemiparasite. Tracer studies show that solutes move across this pathway from the host to the shoot of the hemiparasite.Three types of hair clothe the shoot. They develop precociously, commencing to function in guttation before the stomata are perforated and the vascular tissues are differentiated.Guttation fluid and bleeding sap of members of associations of Odontites with barley or Stellaria media were analysed for phosphate, nitrate, calcium, potassium, amides and amino acids. The results suggest that the shoots of the hemiparasite and its host can absorb selectively the solutes supplied from their roots.Microautoradiographic studies of the distribution of [3H]leucine fed to shoots of Odontites through the xylem show that cells bordering on the transpiration pathway actively assimilate the radiosubstrate. Mesophyll cells and glandular hairs of the leaf are particularly active in this respect. It is suggested that glandular secretion plays a relatively important role in directing solutes mto young parts of the shoot.
UPTAKE AND METABOLISM OF EXOGENOUSLY SUPPLIED SUGARS BY BROWN ALGAE
Authors: DREW EDWARD A. 
Published: May 2006

SummaryIn nine of eleven species of brown algae tested, much of the 14C‐glucose taken up from aqueous media was readily leached out again during subsequent washing in ice‐cold seawater. Whilst none of the unleachable fraction was converted to 14C‐mannitol, a considerable proportion was incorporated into insoluble glucose polymers and some was lost in respiration.Two species—Ascophyllum nodosum and Pelvetia canaliculata—were very different in that very little accumulated 14C‐glucose could be leached out. Most of the 14C‐glucose in the tissues of these two algae was rapidly converted to 14C‐mannitol, the remainder being either incorporated into insoluble compounds or respired.These two species were also able to convert exogenously supplied 14C‐mannose to mannitol, and Pelvetia incorporated much 14C from exogenous mannitol into a disaccharide compound. Fucus, as a representative of the other species investigated, was unable to metabolize either exogenous mannose or mannitol.None of the eleven species converted either galactose or fructose, supplied exogenously, to mannitol.
EXPERIMENTS ON THE JUVENILE‐ADULT PHASE CHANGE IN SOME WOODY SPECIES
Authors: ROBINSON L. W. , WAREING P. F. 
Published: May 2006

SummaryThe transition from the juvenile to the adult condition (‘phase change’) in woody plants normally occurs at an age and a size characteristic for the species and flowering does not occur until this change has taken place. By experiments with seedlings of birch (Betula verrucosa) grown either continuously under long days in a glasshouse, or periodically under alternating periods of long and short days in association with chilling treatments, it was shown that flowering occurs much sooner in the seedlings grown continuously (i.e. without periods of dormancy) than in seedlings of this species grown under normal outdoor conditions, or in the experimental seedlings grown ‘periodically’. Similar results were obtained with Japanese larch (Larix leptolepis) and black currant (Ribes nigrum) when flower‐inducing treatments appropriate for the species, viz. horizontal training or short days, respectively, were applied after continuously grown seedlings had attained a certain size. Further experiments were carried out with black currant to determine whether the attainment of a certain minimum size is necessary for phase change. The shoot tips of seedlings were removed when they had attained a size at which flowering does not occur and were rooted as cuttings; the latter plants were similarly treated and this process was repeated again twice. The final series of plants which had been derived in this manner initiated flowers in response to short days and thus had attained the adult condition, although at no stage had any of the successive rooted cuttings attained the minimum size at which phase change normally occurs in this species. It is concluded that size, per se, is not the primary factor determining the stage at which phase change occurs.Experiments were carried out with Japanese larch and European larch (Larix decidua) in which scions from juvenile (non‐coning) seedling trees were grafted on to mature trees which produced abundant cones but little evidence was obtained that phase change was hastened by this treatment. On the other hand, a considerable proportion of scions from young trees, which were approaching the adult condition, initiated cones following grafting on to adult trees.Phase change takes place in the shoot apical meristems, which appear to behave as autonomous units in the sense that their transition to the adult condition is apparently not determined by the amount of already differentiated tissue. It is suggested that phase change occurs after the meristems have undergone a certain number of cell divisions, so that the change is correlated with, but not determined by, the attainment of a certain size.
SOME EXPERIMENTAL OBSERVATIONS ON THE CLONE STRUCTURE OF A NATURAL POPULATION OF FESTUCA RUBRA L.
Authors: HARBERD D. J. , OWEN MYRFYN 
Published: May 2006

SummaryIt is confirmed that a worker observing for a season a pair of spaced plants of Festuca rubra growing alongside each other in an experimental garden can conclude with considerable reliability whether or not the two plants are of the same genotype. Out of over 3000 such comparisons made only nineteen proved to be difficult and, even in these cases, the opinion formed after the season's observations proved to be right sixteen times.Sampling patterns more complicated than simple paired isolates are more productive of information and are not too difficult for observation so long as the number of isolates being compared at a time is less than about eight to twelve. The more complicated patterns are more difficult to collect, especially where species cover is low or variable and, for this reason, their use can lead to bias in the observations.The clonal constitution of the population is not uniform over the site. There is a tendency for F. rubra to be more abundant in those parts of the site where the local population is dominated numerically by a single clone. The element of non‐randomness introduced by any sampling method which utilizes isolates from discrete parts of the site is likely to generate serious bias in the results.Small portions of the site are colonized by several different clones intermixed with each other—the mean number of clones present in a 15 × 15 cm turf being 5.2. The chances of two isolates from the population being of the same genotype fall off with distance from about 42% at 2.5 cm apart to 1% at 320 cm.By contrast with a population described earlier, this population is made up of very many clones, several of them being extensively reduplicated, but none of them so extensively as to numerically dominate the population. There are many differences between the two populations in ecology and probably in history but the causes of the different constitutions were not investigated.
SPORE DEVELOPMENT IN THE BROWN ROT FUNGI (SCLEROTINIA SPP.)
Authors: WILLETTS H. J. , CALONGE F. D. 
Published: May 2006

SummaryDevelopment of macro‐ and microconidia of several species of Sclerotinia causing brown rot of rosaceous fruits was studied by light and electron microscopy.Macroconidia are produced by budding and develop in acropetal succession. Septa form centripetally across the constricted regions between the spore initials of a chain. A single pore in each septum permits movement of cytoplasm and organelles along the chains of spores and these pores are probably not plugged until just before the spores are liberated. The ultrastructure of the mature macroconidia is similar to that of the vegetative hyphae, indicating the unspecialized nature of these spores.Microconidia are formed in succession by extrusion from the tips of terminal phialides. The developing spore is protected by a thin wall and is finally cut off by formation of a basal septum. An uneven splitting of this septum occurs, the thicker part becoming the basal wall of the spore. The latter remains loosely attached to the phialide until another spore is produced. Extrusion of the spores leaves a collar or rim just behind the apex of the phialide. The mature spore contains a large lipid body, a single large nucleus, a small amount of cjrtoplasm and one or two small mitochondria. It is thus of simpler organization than the macroconidium.The development and structure of the two types of spore are compared and the differences correlated with function.
STRUCTURAL VARIATIONS IN PEAT
Authors: STEWART J. M. , DURNO S. E. 
Published: May 2006

SummaryThe macro‐ and microscopic structure of an upland bog in north‐east Scotland was examined at two sites, where four main horizons were recognized according to dominant botanical constituents, degree of decomposition and texture after weathering. The botanical composition varied most markedly in the first and second horizons, decomposition in the second and third horizons, and texture in the third and fourth horizons. Microscopic examination of profiles from both sites was based on identifiable leaf cuticular patterns, assorted plant tissues (mainly roots and stems), and the pollen and spore record. The macro‐ and microfossil records from both sites differed in the distribution of Sphagnum spp., Hypnum cupressiforme, Calluna vulgaris and Betula spp., within certain horizons. Regional palynological data, supplemented by radiocarbon dating, placed the initiation of peat accumulation about the Atlantic Sub‐Boreal transition (N.P.L. 94. 5020 ± 95 B.P.). The results of this investigation indicated that isolation of the cuticular components of peat can provide useful supplementary data in the study of upland bogs, in which the regional pollen record is often poorly represented.
THE ACTIVITIES OF THE PHOTOSYNTHETIC CARBON CYCLE ENZYMES OF GREENING BEAN LEAVES
Authors: BRADBEER J. W. 
Published: May 2006

SummaryAfter the transfer of 14‐day old dark‐grown bean seedlings into continuous illumination the etioplasts of the primary leaves develop into chloroplasts in a synchronous manner. Levels of activity in the leaves of most of the enzymes which have been implicated in the photosynthetic carbon cycle have been determined during the first 45 hours of chloroplast development. All of the enzymes investigated were present in etiolated leaves and the activities of most of them increased in response to illumination. One of the early effects of illumination was a rise in the protein content of the leaves, the level of which continued to rise throughout the 45 hours of illumination. Increases in the activity of some of the enzymes, notably phosphoglycerate kinase, fructosediphosphate aldolase, transketolase, NAD‐linked triosephosphate dehydrogenase and triosephosphate isomerase, appeared to begin soon after the commencement of illumination. The onset of light‐induced increases in the activities of ribosephosphate isomerase, phosphori‐bulokinase and ribulosediphosphate carboxylase, showed lag periods of similar duration to the ‘positive’ photoresponse described by Mohr (1966). The longer lag period before an increase of NADP‐Iinked triosephosphate dehydrogenase occurred is consistent with the suggestion of Ziegler and Ziegler (1965) that photosynthetically formed ATP and NADPH may be essential prerequisites for the synthesis of this enzyme. Possible mechanisms of control of the enzyme levels are discussed.The data do not provide any evidence in support of the participation of phosphopyruvate carboxylase, hexosediphosphatase and transaldolase in an important role in connection with the photosynthetic carbon cycle of bean leaves.
LEAF RESISTANCE IN A GLASSHOUSE TOMATO CROP IN RELATION TO LEAF POSITION AND SOLAR RADIATION
Authors: HURD R. G. 
Published: May 2006

SummaryLeaf resistances were measured in a glasshouse tomato crop, using a mass flow porometer. With plants of different age the sixth to eleventh leaf from the top of the plant had the lowest leaf resistance, both within the stand and at its perimeter. Full leaf expansion occurred at the twelfth to fourteenth leaf. Older leaves had high leaf resistances, especially within the crop.Raising the CO2 concentration of the glasshouse to approximately 1000 vpm tended to increase leaf resistance but this increase was seldom significant and was sometimes not observed at all.On sunny days, leaf resistances were higher for much of the day than resistances on dull days. This was believed to be due to a form of the midday stomatal closure observed in some plants under high insolation.
INTERACTION OF INDOLYL ACETIC ACID AND GIBBERELLIC ACID IN THE SYNTHESIS OF α‐AMYLASE BY BARLEY ALEURONE
Authors: MACLEOD ANNA M. , PALMER G. H. 
Published: May 2006

SummaryWhen slices of barley endosperm were supplied with a mixture of 10−4 M gibberellic acid and indolyl acetic acid (10−4 or 10−10 m) continuously for 36 hours the amount of α‐amylase formed was significantly less than that formed in response to gibberellic acid alone. However, pre‐treatment of slices with a mixture of 10−10 M indolyl acetic acid + gibberellic acid for 8 hours followed by incubation in gibberellic acid alone resulted in enhanced levels of production of α‐amylase.Removal of coleoptile tips from germinating grains was followed by diminished synthesis of α‐amylase in the endosperm, but the level of α‐amylase formed could be restored to that found in the intact grain by supplying 10−7 M indolyl acetic acid to the coleoptile stump.It is suggested that indolyl acetic acid, migrating from the coleoptile tip, is involved not only in the process of lignification in the scutellum but also in the preliminary stages of gibberellin‐mediated α‐amylase formation in the aleurone.
TEMPERATURE RESPONSES IN ALTITUDINAL POPULATIONS OF EUCALYPTUS PAUCIFLORA SIEB. EX SPRENG
Authors: GREEN J. W. 
Published: May 2006

SummaryThe effects of temperature variation on germination and seedling growth in populations from different altitudes of Eucalyptus pauciflora were investigated by means of experiments in controlled environments and under natural conditions in the field.Germination and seedling growth showed no statistically significant variation in optimum temperature according to altitude. On the other hand, there was strong evidence of differential resistance to freezing temperatures whereby seedlings from high‐altitude seed proved considerably more resistant than those from low‐altitude seed. This was reflected, to a certain extent, in the survival of reciprocal transplants over winter.The relative uniformity of temperature optima suggested that in the field germination and early seedling growth would occur later with increasing altitude, thus bearing out casual field observations. The marked altitudinal variation in tolerance to low temperatures suggested that natural selection may have operated under the influence of winter temperature gradients to bring about adaptive changes related to altitude of occurrence.
SOFTWOOD STRUCTURE AND THE CLASSIFICATION OF CONIFERS
Authors: YOUNG D. J. , WATSON L. 
Published: May 2006

SummaryComputational analysis of anatomical data for 113 species and forty‐two genera of Coniferae shows a marked distinction between Pinaceae and the rest, not reflected in taxonomic systems but consistent with other information. Most accepted genera and families, and the sections of Pinus, have anatomical support. Cupressaceae, however, fall into two widely separated groups, southern members joining the Podocarpaceae and Araucariaceae and the rest associating with northern families. The order Taxales is not distinguished by wood structure.
AEROPALYNOLOGY IN BRITAIN—AN OUTLINE
Authors: HYDE H. A. 
Published: May 2006

SummaryThe author reasserts his original definition of palynology as the study of plant spores and their dispersal and applications thereof, and here considers aeropalynology as that branch of palynology which is concerned with the dissemination of plant spores in both theory and practice. During the present century important advances in methods of sampling atmospheric spores have been made and have been applied at a limited number of locations in England, Wales and Scotland either with a view to assessing the general (outdoor) aerospora of the region concerned or of various special habitats. Variation both ‘circadian’and annual in the incidence of various spore types has been studied. The atmospheric transport of microbes (dispersal in the wider sense) which embraces take‐off (liberation), free flight (dispersion proper) and landing (deposition) has occupied the attention of several workers. Advances have been made also in intramural palynology. The fact that the aerospora is a reflex of the vegetation has been recognized but not worked out in detail despite the abundant data available. Finally the author claims that the many applications of aeropalynology both potential and actual, would amply justify further long‐term observation and assessment of the aerospora.
THE FINE STRUCTURE OF GYMNODINIUM FUSCUM (DINOPHYCEAE)
Authors: DODGE J. D. , CRAWFORD R. M. 
Published: May 2006

SummaryThe large freshwater dinoflagellate Gymnodinium fuscum (Ehrenberg) Stein, which is the type species of the genus, has flagella, chloroplasts, mitochondria, golgi bodies and chromosomes with typically dinophycean fine structure. It has an elaborate pusule with a large central vesicle, into which numerous small vesicles open, and a spiral canal which connects the central vesicle to the exterior. The nuclear envelope is complex with many flattened vesicles built into it which are perforated only towards the nucleus. The theca consists of three membranes, enclosing beneath the outer two a thin plate‐like structure homologous with the plates of armoured dinoflagellates. Beneath the third membrane numerous microtubules are found. G. fuscum does not possess pyrenoids or trichocysts.
PARTIAL IDENTIFICATION OF DARK 14CO2 FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)
Authors: KNAUFT ROBERT L. , ARDITTI JOSEPH 
Published: May 2006

SummaryFollowing exposure of Cattleya leaves to 14CO2 in the dark, labelled malate, citrate and an unidentified compound were detected by thin layer chromatography. This is interpreted to suggest the existence in Cattleya leaves of a dark CO2 fixation pathway which may be similar to that found in other plants which can fix large amounts of carbon in the dark.