bluuebunny/crossref_metadata_2025 huggingface dataset:
Treeline dynamics in relation to climatic variability in the central Tianshan Mountains, northwestern China
Authors: Wang Ting , Zhang Qi‐Bin , Ma Keping
Published: May 2006

Aim  Climate variability may be an important mediating agent of ecosystem dynamics in cold, arid regions such as the central Tianshan Mountains, north‐western China. Tree‐ring chronologies and the age structure of a Schrenk spruce (Picea schrenkiana) forest were developed to examine treeline dynamics in recent decades in relation to climatic variability. Of particular interest was whether tree‐ring growth and population recruitment patterns responded similarly to climate warming.

Location  The study was conducted in eight stands that ranged from 2500 m to 2750 m a.s.l. near the treeline in the Tianchi Nature Reserve (43°45′−43°59′ N, 88°00′−88°20′ E) in the central Xinjiang Uygur Autonomous Region, northwestern China.

Methods  Tree‐ring cores were collected and used to develop tree‐ring chronologies. The age of sampled trees was determined from basal cores sampled as close as possible to the ground. Population age structure and recruitment information were obtained using an age–d.b.h. (diameter at breast height) regression from the sampled cores and the d.b.h. measured on all trees in the plots. Ring‐width chronologies and tree age structure were both used to investigate the relationship between treeline dynamics and climate change.

Results  Comparisons with the climatic records showed that both the radial growth of trees and tree recruitment were influenced positively by temperature and precipitation in the cold high treeline zone, but the patterns of their responses differed. The annual variation in tree rings could be explained largely by the average monthly minimum temperatures during February and August of the current year and by the monthly precipitation of the previous August and January, which had a significant and positive effect on tree radial growth. P. schrenkiana recruitment was influenced mainly by consecutive years of high minimum summer temperatures and high precipitation during spring. Over the last several decades, the treeline did not show an obvious upward shift and new recruitment was rare. Some trees had established at the treeline at least 200 years ago. Recruitment increased until the early 20th century (1910s) but then decreased with poor recruitment over the past several decades (1950–2000).

Main conclusions  There were strong associations between climatic change and ring‐width patterns, and with recruitments in Schrenk spruce. Average minimum temperatures in February and August, and total precipitation in the previous August and January, had a positive effect on tree‐ring width, and several consecutive years of high minimum summer temperature and spring precipitation was a main factor favouring the establishment of P. schrenkiana following germination within the treeline ecotone. Both dendroclimatology and recruitment analysis were useful and compatible to understand and reconstruct treeline dynamics in the central Tianshan Mountains.
Simultaneous Wavelet Deconvolution in Periodic Setting
Authors: DE CANDITIIS DANIELA , PENSKY MARIANNA
Published: May 2006

Abstract.  The paper proposes a method of deconvolution in a periodic setting which combines two important ideas, the fast wavelet and Fourier transform‐based estimation procedure of Johnstone et al. [J. Roy. Statist. Soc. Ser. B66 (2004) 547] and the multichannel system technique proposed by Casey and Walnut [SIAM Rev. 36 (1994) 537]. An unknown function is estimated by a wavelet series where the empirical wavelet coefficients are filtered in an adapting non‐linear fashion. It is shown theoretically that the estimator achieves optimal convergence rate in a wide range of Besov spaces. The procedure allows to reduce the ill‐posedness of the problem especially in the case of non‐smooth blurring functions such as boxcar functions: it is proved that additions of extra channels improve convergence rate of the estimator. Theoretical study is supplemented by an extensive set of small‐sample simulation experiments demonstrating high‐quality performance of the proposed method.
Comparison of Regression Curves with Censored Responses
Authors: PARDO‐FERNÁNDEZ JUAN CARLOS , KEILEGOM INGRID VAN
Published: May 2006

Abstract.  In this article, we introduce a procedure to test the equality of regression functions when the response variables are censored. The test is based on a comparison of Kaplan–Meier estimators of the distribution of the censored residuals. Kolmogorov–Smirnov‐ and Cramér–von Mises‐type statistics are considered. Some asymptotic results are proved: weak convergence of the process of interest, convergence of the test statistics and behaviour of the process under local alternatives. We also describe a bootstrap procedure in order to approximate the critical values of the test. A simulation study and an application to a real data set conclude the paper.
On the Limits of a Realist Conception of Knowledge: A Pragmatist Critique of Archerian Realism
Authors: Kivinen Osmo , Piiroinen Tero
Published: May 2006

In her book Being Human (2000), Margaret Archer presents intriguing pragmatist emphases on practice, embodiment and non-linguistic knowing-how, as regards to understanding humanity. However, as Archer attempts to conjoin these ideas with the morphogenetic realism she has been working on for the last few decades, she ends up holding on to a subject–object dualism, which makes things complicated. The authors' alternative pragmatist account defended in the article flows from Deweyan pragmatist and Rortian antirepresentationalist insights. The main issues in the article concern Archer's complicated tripartite concept of knowledge, which is contrasted with a (Deweyan–Rylean) distinction between linguistic knowledge-that and embodied knowing-how. It is argued that knowledge is a natural, sophisticated tool that human organisms use when coping with their environment; it is always acquired on the strength of embodied knowing-how, from some actor's point of view, but the term ‘knowledge’ itself should be reserved for the propositional, linguistic knowledge-that.
Getting Onboard: Women, Access and Serious Leisure
Authors: Raisborough Jayne
Published: May 2006

This paper explores women's experiences of accessing serious leisure. It responds to a perceived tendency in contemporary feminist theories of leisure to celebrate women's ability to weave potentially empowering identities from discursive resources in leisure spaces and experiences. While this work creates much needed theoretical space for the exploration of women's agency and self determination within leisure, there is little critical attention given to how women may first negotiate the complexity of their gendered lives to gain access to these sites and experiences. By drawing on the accounts of forty women involved in the Sea Cadet Corps, a form of serious leisure, this paper argues that accessing leisure is still an important aspect of women's leisure experiences. Women cited here engage in active and conscious practices and performances to both justify their access to leisure and to enable their disengagement from demands associated with normative femininity. This paper concludes that to sideline questions of access serves to conceptually dislocate leisure from the wider patterns of women's everyday lives and limits our understanding of how women perceive, use and give meaning to their serious leisure participation.
Investigating Consumption Anxiety Thesis: Aesthetic Choice, Narrativisation and Social Performance
Authors: Woodward Ian
Published: May 2006

Warde's (1994) theoretical analysis of possible anxieties provoked in the act of consumption synthesises a large body of contemporary literature on uncertainty, social change and consumption. In doing so, it offers a predominantly structural model of the anxiety provoking tensions and forces individual consumers may be exposed to. Drawing on the work of contemporary figurehead theorists of social change, and proposing his own application of Durkheim's model of suicide to the problem of consumption anxiety, Warde presents a model of how anxieties and their mitigation are embedded within configurations of contemporary consumer culture. Though Warde's analysis illustrates the structural, theoretical context of potential consumption anxieties for particular social groups, it is unable to specify how such anxieties are manifested and managed – or performed – by individuals within specific social and consumption settings. This paper takes an interpretive approach, conceptualising consumption anxiety as a discursive, narrative phenomenon likely to surface within particular social settings that are conducive to generating expressions of anxiety. The paper also considers the relation between narrativisation and objects, arguing that the cultural capacity of objects must be understood within local settings where objects are afforded a capacity to act through various discourses. The argument is drawn using selections of face-to-face interview data collected from a sample of middle-class householders on the practice of home decoration.
'When I'm in the Garden I Can Create My Own Paradise': Homes and Gardens in Later Life
Authors: Bhatti Mark
Published: May 2006

This paper brings together recent work on later life and considers the effects of ageing in relation to participation and interest in gardening. Whilst there is considerable research and literature on issues such as health, housing, and social care, the significance of the garden in process of home-making is less well understood. Using qualitative data from the Mass Observation Data Archive, key physical, psycho-social processes that impact on the use of the garden and gardening activities are examined. It will be suggested that the garden can have major significance in the (re) creation of ‘home’ in later life.
Navigation, Interaction and Bridge Team Work
Authors: Bailey Nicholas , Housley William , Belcher Phillip
Published: May 2006

During the course of this paper we explore the interaction of seafarers engaged in navigation on the bridge of a merchant ship. More specifically we examine how ‘bridge teams' utilise a range of practical conversational methods and devices in carrying out the days work within a context where temporal and spatial considerations are paramount. Utilising the principles of ethnomethodologically informed conversation analysis we analyse transcribed materials gathered from a working bridge. The business of bridge team-work is the generation of a mutual frame of navigational perspective and decision making. A central aspect of this interactional accomplishment is a confirmatory form of talk that is utilised in order to avoid confusion and maritime disaster. The paper also explores empirical examples of interaction and identifies the way in which bridge team-work is accomplished, organised and sustained. The paper suggests how consideration of these features may inform further enquiry and modify training practice.
Normobaric Hypoxia and Nitroglycerin as Trigger Factors for Migraine
Authors: Schoonman GG , Sándor PS , Agosti RM , Siccoli M , Bärtsch P , Ferrari MD , Baumgartner RW
Published: May 2006

Migraine prevalence is increased in high-altitude populations and symptoms of acute mountain sickness mimic migraine symptoms. Here we tested whether normobaric hypoxia may trigger migraine attacks. As positive control we used nitrolgycerin (NTG), which has been shown to induce migraine attacks in up to 80± of migraineurs. Sixteen patients (12 females, mean age 28.9 ± 7.2 years) suffering from migraine with ( n = 8) and without aura ( n = 8) underwent three different provocations (normobaric hypoxia, NTG and placebo) in a randomized, cross-over, double dummy design. Each provocation was performed on a separate day. The primary outcome measure was the proportion of patients developing a migraine attack according to the criteria of the International Headache Society within 8 h after provocation onset. Fourteen patients completed all three provocations. Migraine was provoked in six (42±) patients by hypoxia, in three (21±) by NTG and in two (14±) by placebo. The differences among groups were not significant ( P = 0.197). The median time to attacks was 5 h. In conclusion, the (remarkably) low response rate to NTG is surprising in view of previous data. Further studies are required to establish fully the potency of hypoxia in triggering migraine attacks.
Botulinum Toxin Type A in the Prophylactic Treatment of Chronic Tension-Type Headache: A Multicentre, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study
Authors: Silberstein SD , Göbel H , Jensen R , Elkind AH , DeGryse R , Walcott JMCM , Turkel C
Published: May 2006

We studied the safety and efficacy of 0 U, 50 U, 100 U, 150 U (five sites), 86 Usub and 100 Usub (three sites) botulinum toxin type A (BoNTA; BOTOX®; Allergan, Inc., Irvine, CA, USA) for the prophylaxis of chronic tension-type headache (CTTH). Three hundred patients (62.3± female; mean age 42.6 years) enrolled. For the primary endpoint, the mean change from baseline in the number of TTH-free days per month, there was no statistically significant difference between placebo and four BoNTA groups, but a significant difference favouring placebo vs. BoNTA 150 was observed (4.5 vs. 2.8 tension headache-free days/month; P = 0.007). All treatment groups improved at day 60. Although efficacy was not demonstrated for the primary endpoint, at day 90, more patients in three BoNTA groups had ≥50± decrease in tension headache days than did placebo ( P ≤ 0.024). Most treatment-related adverse events were mild or moderate, and transient. BoNTA was safe and well-tolerated in the study.
Voluntary Disclosure of Information in a Setting in which Endowment of Information has Productive Value
Authors: Frantz Pascal , Instefjord Norvald
Published: May 2006

Abstract:  This paper introduces a model capturing managers' disclosure policies in settings in which disclosure is rewarded by the financial market because disclosure implies that managers are endowed with information and endowment of information may potentially improve the firm's productive efficiency. It provides sufficient condition for a threshold disclosure equilibrium to obtain and compares disclosure policies in a setting in which endowment of information improves the firm's productive efficiency with disclosure policies in a setting in which endowment of information has no impact on the firm's productive efficiency. Managers' disclosure policies are shown to depend crucially on whether the endowment of information is exogenous or endogenous. When the endowment of information is exogenous, an increase in the usefulness of information in improving the firm's productive efficiency leads to a decrease in the disclosure threshold and hence an increase in the amount of information disclosed. In contrast, when the endowment of information is endogenous, an increase in the usefulness of information in improving the firm's productive efficiency has no effect on the disclosure threshold but leads to a decrease in the probability with which information is acquired and hence a decrease in the amount of information disclosed. As, in the threshold disclosure equilibrium, the net present value of information acquisition arising from any increase in production efficiency is negative, an increase in the usefulness of information in improving the firm's productive efficiency thus reduces the inefficiency caused by information acquisition.
CYTOTAXONOMIC STUDIES IN HOLCUS
Authors: JONES KEITH
Published: May 2006

summary

Studies have been made of the relative frequency and distribution in parts of Britain of the chromosome races of Holcus mollis (2n= 28, 35, 42, 49). These show that the penta‐ploid is the most common race and that the distribution of the races as a whole is a reflection of varying degrees of adaptability to moisture content of the soil.

Chromosome studies at meiosis and mitosis show that the tetraploid is an allopolyploids and that the hexaploid is derived from it. The penta‐ploid appears to be derived from a hybrid of H. lanatus (2n=14) and H. mollis (2n= 28).

The hybrid nature of the penta‐ploid is confirmed by the discovery of natural triploid hybrids (2n= 21) from which it is presumed to have been derived by backcrossing to the tetraploid parent.

With the exception of the tetraploid, the races of H. mollis reproduce almost exclusively by vegetative means. The tetraploid is fertile but is also likely to reproduce mainly by rhizomes.

The success of the penta‐ploid is attributed to its hybrid vigour in both growth and adaptability to soil moisture. In addition its spread is favoured by the fact that its tetraploid parent does not offer much seed competition in the colonization of new areas. There is no competition from the H. lanatus parent, which has different ecological requirements.

It is considered feasible that the vigorous penta‐ploid could eventually supersede the other races of H. mollis.
THE STUDY OF POLLEN GRAIN SURFACES IN THE ELECTRON MICROSCOPE
Authors: BRADLEY D. E.
Published: May 2006

summary

1. The application of the electron microscope to the study of pollen grains is discussed.

2. Two carbon replica methods suitable for the study of pollen grain surfaces are briefly described.

3. Examples are given of the surfaces of various pollen specimens, and a distinction between the submicroscopic structures of Corylus and Myrica is reported. Structures within the furrows of some grains are described.

The high resolving power of the electron microscope is of considerable value in the study of pollen, and the sub‐microscopic structure revealed is of interest in problems of identification and of pollen morphology. However, the difficulties encountered in the preparation of pollen specimens for the electron microscope have limited the amount of research carried out in this field.

Pollen grains cannot be examined directly in the instrument because of their size and consequent density to electrons, and even in the case of acetolysed grains the remaining wall is still far too thick to allow the passage of electrons through it. It is therefore necessary to employ either thin sections or surface replicas. The first method has been used extensively by Mühlethaler (1953), Afzelius, Erdtman and Sjöstrand (1954) and Afzelius (1950) in studies of pollen and spore walls. Surface replicas have been employed by Mühlethaler (1955) who used the carbon replica method (Bradley, 1954a). The present author has also made some preliminary studies using this technique (Bradley, 1956). This paper is concerned with the potentialities of the carbon replica in the study of pollen grain surfaces.
ON THE STRATIGRAPHY AND PALAEOBOTANY OF A LATE‐PLEISTOCENE ORGANIC DEPOSIT AT CHELFORD, CHESHIRE
Authors: SIMPSON I. M. , WEST R. G.
Published: May 2006

summary

The stratigraphy of the Pleistocene deposits in the area of Chelford is described.

The palaeobotany of a layer of organic mud within the Middle Sands of the Pleistocene sequence is described, and it is shown that the organic mud was deposited during a cool period in which a Betula‐Pinus‐Picea forest was the local dominant vegetation. The climatic indications given by the flora and vegetation are discussed.

The organic mud is tentatively correlated with an interstadial period early in the Last Glaciation; the implications of this correlation are briefly mentioned.
TWO LACUSTRINE DEPOSITS IN THE SOUTH OF THE ENGLISH LAKE DISTRICT
Authors: SMITH A. G.
Published: May 2006

Summary

It is shown that the lowermost deposits at Helton Tarn and at the former lake near Witherslack Hall, Westmorland, date from Late‐glacial times and that zones I, II and III correspond roughly to layers of laminated clay, clay mud, and clay, respectively. There is little evidence for solifluction in zone III. Pollen analysis reveals a Late‐glacial flora comparable with floras of similar date which have already been described. A minor oscillation, in which herb pollen becomes predominant over tree and shrub pollen, occurs at both sites during zone II. At Helton Tarn some of the pollen types characteristic of the Late‐glacial period occur sporadically until Boreal and Atlantic time; at both sites pollen of those weed and ruderal types which are plentiful in the early deposits constantly recurs throughout Post‐glacial time.

Stratigraphical and pollen analytical evidence suggests that at the maximum of the early Post‐glacial marine transgression, the sea overflowed a rock bar that is now at about + 5 m. O.D. into the Helton Tarn basin and laid down a layer of clay during the earliest part of Atlantic time.

In contrast to the findings of Walker (1955a), at the sites investigated, Finns appears to have been relatively successful in Boreal time and Tilia pollen, although not appearing until early Atlantic time, is present in quantity throughout most of post‐Boreal time. The relatively high proportion of Tilia pollen suggests that the lime was growing as far north as southern Westmorland in post‐Boreal time.

At the opening of the Sub‐boreal period, at the first decline of Ulmus pollen, the presence of small amounts of Plantago lanceolata pollen is taken to indicate the first agricultural activity in the region.
THE ECOLOGY OF FUNGI IN CALLUNA‐HEATHLAND SOILS
Authors: SEWELL GEOFFREY W. F.
Published: May 2006

Summary

The fungi occurring in some Calluna‐heathland soils in England and Wales were studied by the soil plate method. A small proportion of the fungi isolated were of constant occurrence and are considered to be representative members of the heath land fungus flora as demonstrated by the soil plate method. The distribution of fungi in area could be related to the known habitat characteristics in a few instances: these relationships were obtained mainly with fungi which tended to dominate the immediate subsurface populations.

The numbers of species decreased with depth and only five species were at their most frequent occurrence in horizons below the surface: four of these were species of high constancy of occurrence in these soils. Evidence suggested that the presence of illuviated horizons in the soil profile restricted the vertical distribution of sporing species. The deepest soil levels were colonized largely by a miscellany of sterile mycelia.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: CHARLES H. P.
Published: May 2006

Summary

A study has been made of the effects of 2‐naphthoxyacetic acid (2‐NOA) on excised roots from various strains of groundsel. The roots were grown in medium containing lysine and 2‐NOA for one passage and were then subcultured into arginine medium for their second passage.‘Directly’ the effect of 2‐NOA was to increase, though to different levels, the growth of the roots of all strains.‘Indirectly’ and at a concentration appropriate to each strain, it increased the growth of all four strains up to the same high level. The hypothesis is advanced that a major factor responsible for the different growth rates of the roots of the different strains is their content of a natural growth substance whose physiological properties are simulated by 2‐NOA.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: SHEAT D. E. G. , FLETCHER B. H. , STREET H. E.
Published: May 2006

Summary

The composition of the inorganic fraction of White's medium has been modified to permit studies in nitrogen nutrition. A preparation of ferric sodium ethylenediamine tetra‐acetate is described which enables an addition of 1 p.p.m. iron to meet the iron requirement of exised tomato roots in culture media whose pH is below 7.5.

The content of calcium and magnesium in the medium has been reduced to one‐tenth the standard concentration in order to prevent precipitation at pH values above 6.0, particularly when using enhanced phosphate concentrations.

Techniques whereby the pH of root culture medium can be adjusted aseptically or stabilized by the addition of soluble phosphates or of sparingly soluble salts of calcium (phosphate, carbonate) are described and evaluated.

These techniques have made possible a high level of growth of excised tomato roots receiving ammonium as their sole source of nitrogen. The ability of the roots to grow with nitrite as their sole nitrogen source has also been demonstrated. In contrast, hydroxylamine, even at low concentrations, inhibited the extension growth which otherwise occurs on absence of external nitrogen and caused death of the root apices.

pH‐growth response curves with ammonium and with nitrate as nitrogen sources indicate pH 4.7–4.9 as optimum for growth with nitrate nitrogen and pH 7.0–7.2 as optimum for growth with ammonium nitrogen. Less complete data indicates pH 5.0–6.0 as the optimum region for growth with nitrite.

From studies of the pH drifts occurring as a result of root growth in media containing various ammonium: nitrate ratios and from direct determinations of nitrate and ammonium uptake at high and low pH, it is concluded that the differing pH optima for these two nitrogen sources are not explicable in terms of the direct effects of pH upon the uptake of these ions.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: HANNAY J. W. , FLETCHER B. L. , STREET H. E.
Published: May 2006

Summary

Excised tomato roots supplied their nitrogen as nitrate in media of pH 4–5 or pH 7 have an essential requirement for molybdenum. Their growth is markedly stimulated and their continued culture made possible by the addition of 0.000005 p.p.m. Mo. The minimum addition which fully satisfies the molybdenum requirement is 0.001 p.p.m. The depression of growth resulting from a deficiency of molybdenum is not due to the toxicity of accumulating nitrate.

Excised roots supplied their nitrogen as nitrite, ammonium, urea, casein hydrolysate or as a mixture of L(+)— arginine and glycine are capable of growth in molybdenum‐omitted medium. Their growth is stimulated by addition of molybdenum and a similar addition is required for optimum growth whether nitrogen is supplied as nitrate or as ammonium.

The tolerance of excised tomato roots to excess manganese at pH 7.0 is greater in ammonium than in nitrate media. The optimum manganese addition is increased by supraoptimal concentrations of ammonium. Optimum growth is only achieved when the medium has a satisfactory magnesium: manganese ratio. The deleterious effects of excess manganese can be counteracted by increasing the concentration of magnesium. At low manganese concentration, growth is depressed by enhancing the magnesium concentration.

Using a medium buffered with calcium carbonate (pH 7) and with a manganese addition of 0.01 p.p.m. the continuous culture of excised tomato roots supplied their nitrogen solely as ammonium has been achieved. No improvement of the very poor growth occurring in ammonium media at pH 4–5 has been achieved by altering the absolute and relative concentrations of a number of macronutrient elements.
POPULATION DIFFERENTIATION IN AGROSTIS TENUIS SIBTH
Authors: BRADSHAW A. D.
Published: May 2006

Summary

In order to investigate the pattern of population differentiation in Agrostis tennis, sixty tillers were collected from each of thirty‐three areas mainly in central Wales. These were grown under garden conditions in Aberystwyth. In a subsequent experiment five of these areas were sampled again by tillers, and at the same time sampled by seed. These samples were grown under garden conditions in Bangor.

Numerous differences between these population samples were recorded. The main conclusions are as follows:

(i) The environment is the dominating factor in determining population differentiation.

(ii) Although the distribution is continuous, distances of about 50 m or less are sufficient to effectively isolate populations from one another.

(iii) Thus the species is able to evolve under the influence of natural selection in response to very local variations in environment.

(iv) Since the environment is a graded patchwork of different conditions, the pattern of differentiation is similar.

(v) It is, therefore, not possible to classify effectively such interspecific variation.

(vi) It is likely that this situation is to be found in most other out breeding continuously distributed plant species occupying a wide range of habitats.
EFFECT OF VESIGULAR‐ARBUSCULAR MYCORRHIZAS ON GROWTH OF GRISELINIA LITTORALIS (CORNACEAE)
Authors: BAYLIS G. T. S.
Published: May 2006

Summary

The endophyte of Griselinia littoralis is a vesicular‐arbuscular Phycomycete which could not be induced to make more than transient growth into agar, but which survived in soil kept moist for 26 months.

In two consecutive experiments using sterilized soil in which ectotrophic mycorrhizas were necessary for sustained growth of Pinus radiata the endotrophic mycorrhizas of Griselinia littoralis proved necessary for sustained growth of that species. Under the same conditions seedlings of a non‐mycotrophic tree, Myrsine australis, grew steadily.

The technique used to establish mycorrhizas upon Griselinia did not stimulate its growth when mycorrhizas were not formed. It produced no symbiotic infection in Pinus and only traces of it in Myrsine, and it depressed the growth of both these species.

In both Pinus and Griselinia percentage composition of mycorrhizal plants was consistently higher in phosphorus and lower in nitrogen than that of non‐mycorrhizal plants. Enhanced phosphorus uptake thus appears to have been the main favourable effect of both types of mycorrhiza.
POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: WAREHAM, DORSET AND NURSLING, HAMPSHIRE
Authors: SEAGRIEF S. C.
Published: May 2006

Summary

Pollen analytic investigations made at two sites in southern England, Wareham, Dorset and Nursling, Southampton, show in each instance valley fen deposits extending over a considerable part of Post‐glacial time. The general trends of the tree‐pollen curves conform closely to the pattern established by Godwin (1940 and later papers). At Nursling the earliest deposits were formed in zone III and exhibit a typical range of Late‐glacial pollen types.

Lists of macroscopic remains are given for each site. Remains of Pinus sylvestris in zones III, IV and V establish the early presence of this tree in southern England and Fagus sylvatica also appears to have been present from early Atlantic time. There is some evidence for the presence of open heath and grassland in Wareham from the same period onwards.
AMINO ACIDS AS NITROGEN SOURCES FOR THE GROWTH OF EXCISED ROOTS OF RED CLOVER
Authors: HARRIS G. P.
Published: May 2006

Summary

Two clones of excised roots of red clover have been established and maintained in culture. One of these (Clone A) was selected as showing a satisfactory level of growth in the standard medium and the other (Clone Z) as being relatively resistant to growth inhibition by L‐aspartic acid.

L‐aspartic acid, L‐asparagine, L‐glutamic acid and L‐α‐alanine were each effective as sole sources of nitrogen for the growth of excised roots of Clone Z but not for roots of Clone A.

L‐aspartic acid, L‐glutamic acid and L‐α‐alanine each depressed the growth of the roots when supplied in the presence of nitrate. Roots of Clone Z were more resistant to growth inhibition by these amino acids than roots of Clone A.

L‐valine and glycine were ineffective as sole sources of nitrogen for growth of roots of either clone and were inhibitory to growth when supplied in the presence of nitrate.

L‐arginine was effective as a sole source of nitrogen for the growth of roots of both Clone A and Clone Z. With increasing concentrations of the amino acid supplied in the presence of nitrate, growth of roots of both clones was first stimulated and then depressed.

In experiments with Clone A, it was shown that D‐arginine was similar to L‐arginine in its effects on growth, but that DL‐alanine was more inhibitory than L‐alanine.

When amino acids were supplied as sole sources of nitrogen, growth was always inferior to that obtained with nitrate. Urea, however, supported a level of growth similar to that supported by nitrate.

The technique of excised root culture is suited to the study of the utilization of amino acids as nitrogen sources for plant growth. Nitrogen deficiency can be developed rapidly in excised root‐tips and the technique permits work with clonal material under sterile, controlled conditions. A number of investigations of the nutrient requirements of excised roots have included an examination of effects of amino acids on growth (White, 1937, 1939; Baylor and Rappaport, 1950; Boll, 1954; Skinner and Street, 1954; Roberts and Street, 1955). In these cases the primary objective has been to test amino acids as potential growth factors rather than as nitrogen sources for the roots. However, Skinner and Street (1954), working with excised roots of groundsel, established that L‐arginine, L‐ornithine, L‐citrulline and L‐lysine, which were stimulatory to growth in the presence of nitrate, were also effective in supporting growth in the absence of other nitrogen sources.
THE COMPARATIVE BIOLOGY OF CLOSELY RELATED SPECIES LIVING IN THE SAME AREA
Authors: MCNAUGHTON I. H. , HARPER JOHN L.
Published: May 2006

Summary

It has been demonstrated that in Britain five species of Papaver (a) frequently occur together, (b) flower over the same general period, (c) are normally insect‐pollinated and possess insect visitors in common. Hybrids are rare under natural conditions although some can easily be produced artificially.

The external barriers reducing the chances of natural hybridization are the facts that (a) some of the species have mechanisms facilitating self‐pollination, and (b) specific selection by the principal insect visitor, the honey‐bee, tends to reduce the chances of cross‐pollination between the species.
THE MATHEMATICAL RELATIONSHIP BETWEEN THE LENGTHS OF LATERAL NERVES AND THEIR POSITIONS ON A LEAF
Authors: BURTON R. F.
Published: May 2006

Summary

An equation is proposed which has been successfully applied to the leaves or leaflets of fifteen species, relating the lengths of the main lateral nerves to their positions on the midrib. Certain constants arising from the equation are shown to be interrelated or correlated with the position of the leaf on the shoot.

The validity of the equation and the possibility of more general application among Dicotyledons is discussed. No explanation in terms of the growth processes of the leaf has been found.
THE INFLUENCE OF ENVIRONMENTAL CONDITIONS ON INFLORESCENCE DEVELOPMENT IN SOME LONG‐DAY GRASSES
Authors: EVANS L. T.
Published: May 2006

Summary

There is a reasonably close relation between the length and the stage of morphological development of the inflorescences of Lolium temulentum and L. perenne over a wide range of environmental conditions. Since inflorescence length increases exponentially under constant conditions the relative growth rate of the inflorescence provides a suitable index of the rate of inflorescence development.

The rate of inflorescence development in various grasses has been found to be unaffected by the extent of vernalization, and to be increased by increasing temperature, photoperiod length and number of long days given.

Under standardized temperature and photoperiod conditions during inflorescence development there is a hyperbolic relation between the rate of inflorescence development and the number of inductive long days given to plants of L. temulentum, and to fully vernalized plants of Cynosurus cristatus. Lolium temulentum plants require exposure to only I long day for induction to occur.

The rate of inflorescence development is only slightly affected by the interpolation of short days between the inductive long days given to plants of L. temulentum.

Cynosurus cristatus plants exposed to only 4 to 8 long days bore inflorescences with proliferous fertile spikelets, while in those given 9 to 11 long days, vegetative proliferation was restricted to the sterile spikelets. With Lolium perenne plants teratological features of the inflorescence were associated with the interpolation of a period in short days at moderately high temperatures between vernalization and exposure to long‐day conditions.

It is concluded that the rate of inflorescence development may, under standardized conditions, provide an index of the intensity of photoperiodic induction, although the way in which the inductive stimulus influences this rate is not clear.
THE DIATOM FLORA OF A SALT MARSH ON THE RIVER DEE
Authors: ROUND F. E.
Published: May 2006

Summary

The diatom flora of a salt marsh at Neston, Cheshire, and its seasonal cycle has been investigated. The flora on the surface of sand, silted sand, a stream and in pans has been recorded. The differences in the flora of the habitats on the salt marsh and the variation in the flora from the upper to the lower marsh have been examined and the data as a whole compared with that of earlier workers.
CULTURE STUDIES OF BANGIA ATROPURPUREA (ROTH) AG.
Authors: BELCHER J. H.
Published: May 2006

Summary

The freshwater Bangia atropurpurea (Roth) Ag. and the marine B. fuscopurpurea (Dillw.) Lyngb. have both been studied in unialgal culture. They are morphologically similar and have been united by some authors under the former name, but a comparison of salinity ranges in cultures has shown that they differ, only showing optimum growth in freshwater and marine media respectively.

B. atropurpiirea has also been kept under observation in the field for three years and little seasonal periodicity has been noticed. In cultures of this species branched filaments and Conchocelis‐stages have been obtained, both bearing monospores. These stages are described in detail.
STUDIES OF THE LICHEN SYMBIOSIS
Authors: SCOTT G. D.
Published: May 2006

Summary

Culture studies and field observations on Peltigera praetextata (Flk.) Vain, provide evidence of the existence of a delicate state of balance between the co‐symbionts of this lichen.

Excessive supply of nutrients to discs of the lichen results in the outgrowth of the phycobiont and consequent destruction of the symbiotic relationship.

The conjoint effect of excessive moisture and light is shown to bring about similar symbiotic breakdown.

It is suggested that these three factors acting together as a growth‐regulating system are chiefly responsible for the success of the lichen symbiosis.
THE POSITION OF REGENERATING GAMBIA A NEW HYPOTHESIS
Authors: JOHN  , WARREN WILSON PAMELA M.
Published: May 2006

Summary

When young stems are wounded or grafted so that the cambium is interrupted, new vascular cambia tend to regenerate in the callus proliferating from the wounded surfaces. The position in which such cambia arise varies according to the type of wound, but usually is such as to restore locally the normal condition of a closed cambial cylinder. Two theories have hitherto been proposed to define how the positions of these regenerating cambia are controlled. This paper presents evidence that neither of these theories is valid in all situations, and proposes a new working hypothesis. This ‘gradient induction’ hypothesis is stated at the end of the paper. It is in agreement with all types of wound and graft so far studied, and seems also to extend to cambium formation in tissue culture and perhaps to procambium formation in normal apices.
MERICLINAL CHIMERAS IN THE POTATO VARIETY GLADSTONE
Authors: HOWARD H. W.
Published: May 2006

Summary

The potato variety Gladstone, which has white‐splashed‐pink tubers, produces very rarely tubers which have a nearly full red periderm. These tubers are periclinal chimeras, only layer I at the growing point having changed.

A study of mericlinal tubers suggested a minimum number of six initial cells for layer I at the stem apex of axillary buds.

The rarity of mericlinal tubers is due to tubers being formed by axillary meristems which originate as only a small part of the main stem.
STUDIES IN SYSTEMATIC BARK MORPHOLOGY
Authors: WHITMORE T. C.
Published: May 2006

Summary

The production of xylem and phloem sets up tangential stretching forces through the bark. In the living inner bark the resulting strains are mainly accommodated in Dipterocarpaceae by the formation of expansion tissue. The strain set up by a given annual girth increment decreases with increasing girth to a low steady amount at about 90 cm (3 ft) girth. Phloem formation in a mature tree only sets up small strains. These increase from zero at the cambium to a maximum at the surface. Many barks have more expansion tissue than this accounts for; the rest accommodates the strains set up by xylem formation. The tangential extent of the expansion tissue at a given distance from the cambium in any bark is in fact a measure of the ratio of the xylem and phloem growth rates. The three groups of Bark Types in Dipterocarpaceae with different amounts of expansion tissue (Whitmore, 1962a) are therefore groups with different xylem/ phloem ratios.

Phloem growth rate determines periderm pattern and sometimes sloughing rate too. Fissure shape is controlled by periderm pattern and sloughing rate. The xylem growth rate is similar in different groups of dipterocarps. Thus the xylem/phloem ratio is an inverse measure of the phloem growth rate which cannot be measured directly. There is therefore a correlation between the xylem/phloem ratio and periderm pattern, sloughing and fissure shape.

Similarities within the three groups of Bark Types in Dipterocarpaceae arise, therefore, from the dependence of periderm pattern, sloughing and fissure shape on the xylem/phloem ratio. Differences within the three groups arise from features, which are independent of the ratio: inter alia the phloem proliferation tissue, which probably varies phenotypically, and the sloughing mechanism.

It follows that the xylem/phloem ratio is an important factor in the interpretation of diptero‐carp bark construction.

There is no evidence of growth periodicity in the barks examined. Calculations show that the phloem is often conducting for more than 1 year to an observed maximum of 11.4 years; this is in marked contrast with most reports for temperate phloems.
UPTAKE OF SULPHUR BY EXCISED BEECH MYCORRHIZAS
Authors: MORRISON T. M.
Published: May 2006

Summary

Excised mycorrhizas of Fagus were immersed in 35S solution for varying periods after which fungal mantles were dissected from host roots and both components were assayed separately for activity. In general 50% of the sulphur absorbed by mycorrhizas was found in the fungal mantle after 2 hours but this percentage was higher after shorter periods of immersion. Separation of mantle and cores before immersion in the active solution made little difference to absorption by either component.

A comparison was made between absorption of 32P and 35S in both excised and intact mycorrhizas. This showed that the two elements had different absorption patterns and it is concluded that the benefit due to possession of mycorrhizas lies in the large reservoir of phosphorus in the fungal component and in the increased rate of absorption of phosphorus even after this reservoir has been established.
STUDIES IN BRITISH PRIMULAS
Authors: VALENTINE D. H. , WOODELL S. R. J.
Published: May 2006

Summary

Crosses between three diploid species Primula veris, P. vulgaris and P. elatior show marked seed incompatibility. Crosses between the corresponding three autotetraploids give results which are closely comparable with those for the diploids. In both, reciprocal interspecific crosses always produce different and characteristic syndromes of seed development.

Crosses between a diploid and its autotetraploid also show marked seed incompatibility of a similar kind. The data can be interpreted in terms of a hypothesis which assigns different genetic values to the genomes of the species and in which it is assumed that the genetic value of an autotetraploid is twice that of its diploid. The degree of seed failure can then be shown to be related to the difference in the genetic values of the paternal and maternal contributions to the tissues of the seed (embryo and endosperm).

The hypothesis has been tested by making crosses between a diploid species and the autotetraploid of a different species (P. veris 2n—P. elatior 4n), in which there are both qualitative and quantitative differences in the genetic contributions of the parents. The results agree fairly well with expectation, but not exactly.

The results are discussed in the light of current theories of seed incompatibility, and suggestions for further work, both in Primula and other genera, are made.
STUDIES IN SYSTEMATIC BARK MORPHOLOGY
Authors: WHITMORE T. C.
Published: May 2006

Summary

The bark structure and surface pattern of mature trees of Fagus sylvatica L., Quercus robur L. and Castanea sativa Mill, are described in detail and the rate of phloem growth calculated. Differences between Fagus and the other two species are ascribed largely to its slower phloem growth rate. Similarities between the bark of these Fagaceae and certain Dipterocarpaceae are described, and the significance of differences is explored. Comparison with other Fagaceae shows variation in bark in the family to be as wide as in Dipterocarpaceae. It is suggested that phloem growth rate is an important factor controlling bark surface pattern and has been important in bark evolution.
STUDIES IN POTENTILLAL.
Authors: SMITH GORDON L.
Published: May 2006

Summary

The mechanism of reproduction by seed in five British topodemes of Potentilla tabernaemontani has been investigated by means of crossing experiments and embryologically. With a variety of Potentilla species as pollen plants, crossing experiments yield progenies, which, except for the occasional aberrant, are uniform and resemble the female parent in morphology. Embryological preparations show meiosis to be suppressed in all topodemes. In all except one topodeme, the majority of unreduced embryo sacs are diplosporous in origin, in the other they are predominantly aposporous. Although the egg cell is capable of autonomous parthenogenetic development, functional seed is never formed without previous pollination. The conclusion to be drawn from embryology and crossing experiments is therefore that the seed produced is almost completely pseudogamous, thereby reproducing faithfully the genotype of the parent. The topodeme from Fleam Dyke, Cambridge, differed from the others investigated in a number of important respects. These included chromosome number, male sterility, the origin of unreduced embryo sacs and the precocious development of parthenogenetic embryos.
CONSEQUENCES OF ULTRAVIOLET RADIATION ON THE DIFFERENTIATION AND GROWTH OF FERN GAMETOPHYTES
Authors: KATO YUKIO
Published: May 2006

Summary

The effects of ultraviolet light (u.v.), principally at 2537 Å, on the differentiation and growth of gametophytes in Pteris vittata, Osmunda japonica and Dryopteris varia were investigated. It was ascertained that a single cell may be isolated by u.v.‐irradiation and that a normal gametophyte can be regenerated from such a cell.

When gametophytes grown under low intensity (150 lux) white light before u.v.‐irradiation were irradiated with a high dose, an apico‐basal gradient of ability to survive was clearly shown. The survival of each of the cells composing a protonema seems to be related to two different factors; a marked ability for cell division or rapid recovery from the damage of u.v. at the apical region and a high resistance to u.v. at the basal region.

Under both culture conditions, cells of a definite length alone survive. General effects induced by the u.v.‐irradiation include reversal of the polarity in a protonema and modification of the developmental axis. In addition, swelling of the rhizoid and protonema cells, and occurrence of ‘rhizoidal protonema’ were also described.
THE METABOLISM OF [1,3‐14C] ACETONE BY HIGHER PLANT TISSUES
Authors: COSSINS E. A.
Published: May 2006

Summary

The metabolism of [1,3‐14C] acetone by plant tissues has been examined. Under the experimental conditions used, 14C of methyl labelled acetone was rapidly incorporated into CO2, organic acids, amino acids, lipids and into the insoluble residue. In pea cotyledons and beet leaves, acetate and formate together contained the bulk of the radioactivity of the organic acid fraction. The possibility is discussed that acetone, accumulating during the early stages of germination in peas may be subsequently metabolized as seedling development takes place.