bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous senescence in the MDA‐MB‐231 cell line
Authors: Ćukušić A. , Ivanković M. , Škrobot N. , Ferenac M. , Gotić I. , Matijašić M. , Polančec D. , Rubelj I.
Published: May 2006

Abstract.  Normal human somatic cells have a limited division potential when they grow in vitro. It is believed that shortening of telomeres, specialized structures at the ends of chromosomes, controls cell growth. When one telomere achieves a critical minimal length, the cell cycle control mechanism recognizes it as DNA damage and causes the cell's exit from the cycle in G1‐phase. Because it is not possible to extend telomeres in normal cells, this non‐dividing state is prolonged indefinitely, and is known as cellular senescence. The immortal cell line MDA‐MB‐231 has active telomerase, which prevents telomere shortening and allows cells’ permanent divisions. However, there is a fraction of cells that do not divide over several days in culture as documented for some other tumour cell lines. Combination of methods has made it possible to isolate these non‐growing cells and compare them with the fraction of fast‐growing cells from the same culture. Although the non‐growing fraction contains a significant percentage of typical senescent cells, both fractions have equal telomerase activity and telomere length. In this paper we discuss possible mechanisms that cause the appearance of this non‐growing fraction of cells in cultures of MDA‐MB‐231, which indicate stress and genome instability rather than variation in telomerase activity or telomere shortening to affect individual cells.
Interrelated overexpression of endothelial and inducible nitric oxide synthases, endothelin‐1 and angiogenic factors in human papillary thyroid carcinoma
Authors: Donckier Julian E. , Michel Luc , Delos Monique , Havaux Xavier , Van Beneden Ronald
Published: May 2006

Objective  Nitric oxide (NO) and endothelin‐1 (ET‐1) are involved in carcinogenesis. Overexpression of the ET‐1 axis has been demonstrated in papillary thyroid carcinoma (PTC). This study investigated the expression of NO synthases (NOS) and their relationship with expression of ET‐1 and angiogenic markers in PTC.

Design and Patients   Expression of NOS, angiogenic markers [vascular endothelial growth factor (VEGF), angiopoietin‐1 and angiopoietin‐2] and their receptors was studied in surgical thyroid samples obtained from 22 patients aged 15–68 years. Three groups were constituted: normal thyroid (n = 5), Hashimoto's thyroiditis (n = 9) and PTC (n = 8). 

Results   Immunohistochemistry disclosed NOS2 and NOS3 immunoreactivity in PTC cells, the percentage of positive cells being greater than normal (P < 0·02). Real‐time quantitative polymerase chain reaction (RTQ‐PCR) showed that NOS2 and NOS3 mRNA levels were, respectively, increased (P < 0·02) by 2·6 ± 0·6 and 4·2 ± 1·1 times in PTC. RTQ‐PCR demonstrated that VEGF, its receptors VEGFR‐1 and VEGFR‐2, and angiopoietin‐2 and its receptor (Tie2) were also overexpressed (P < 0·05) in PTC. Correlations were found between ET‐1 expression and that of NOS2, angiopoietin‐1 and ‐2 (P < 0·05). NOS2 mRNA levels also correlated with those of NOS3 and angiopoietin‐2 (P < 0·05). In thyroiditis, NOS2 immunoreactivity was observed in inflammatory cells whereas NOS2 mRNA levels were 12·1 ± 1·6 times higher than normal (P < 0·005).

Conclusions   This study revealed an activation of the NO pathway in thyroid carcinoma, which is interrelated to the ET‐1 axis, both systems being overexpressed in concert with angiogenic factors. This global system might play a role in carcinogenesis and constitutes a potential target for anticancer therapy.
Anisotropic shrinkage and swelling of some organic and inorganic soils
Authors: Peng X. , Horn R.
Published: May 2006

Shrinkage and swelling affect hysteretic changes of soil volume as a function of water content. The processes complicate the precise description of changes to soil structure during cycles of wetting and drying, particularly the interpretation for pore structure from water retention characteristics. We investigated soil shrinkage and swelling curves and the hysteresis of void ratio as a function of moisture ratio of four soils (Eutric Histosol, Histic Gleysol, Calcic Gleysol and Dystric Gleysol), and illustrated the anisotropy of soil shrinkage and swelling in two dimensions. We used a model we had developed previously to fit and to define the endpoints of different shrinkage or swelling ranges. The two organic‐rich soils showed only structural and proportional shrinkages, whereas the two inorganic Gleysols covered all four shrinkage ranges. Of all the shrinkage ranges, proportional shrinkage contributed to 60.2–96.8% of total decrease in volume. A typical soil swelling curve was composed of two distinct parts, which were defined as virgin swelling and residual swelling with separation of the wet‐side maximum curvature. The virgin swelling accounted for 81.2–91.9% of the total increase in soil volume. We found pronounced hysteresis during shrinkage and swelling. A single cycle of wetting and drying lost 10–78% of the soil volume. Shrinkage of the organic‐rich soils was significantly greater than that of inorganic Gleysols. The geometry factor, depicting the relationship between the vertical and horizontal deformation, increased from 1.0 to 3.2–4.0 during drying but decreased from 4.6–21.7 to 3.5–5.6 during wetting. The dependence of water content on the geometry indicates anisotropic shrinkage and swelling of the soils. Our results improve the understanding of the alteration of soil structure during shrinkage and swelling and can be also applied to predict hydraulic properties more accurately.
The contribution of fresh litter to dissolved organic carbon leached from a coniferous forest floor
Authors: Fröberg M. , Berggren Kleja D. , Hagedorn F.
Published: May 2006

The relative contributions of litter and humified organic matter as the source of dissolved organic carbon (DOC) leached from organic layers of forest soils are poorly understood. In the present investigation, 13C labelled spruce litter was used to study the role of recent litter in the leaching of DOC from a coniferous forest floor in southern Sweden, while litterbags were used to quantify the total loss of C from the labelled litter. The labelled litter applied on bare lysimeters released considerable amounts of DOC during the first weeks, but the concentration of DOC originating from labelled litter decreased gradually from 176 mg litre−1 during the first sampling period in May to 5 mg litre−1 in the last sampling period in October. Only a moderate flush of DOC from the labelled litter occurred under the Oe and Oa horizons, with concentrations of 20 and 6 mg litre−1 from labelled litter, equal to 19 and 9% of the total DOC flux, respectively, during the first sampling period. Total flux of DOC from labelled litter from May to September was 16 g m−2, whereas only 2.2 and 0.9 g m−2 were captured under the Oe and Oa horizons, respectively. The almost complete loss of new DOC implies that DOC leached from the Oe and Oa horizons consists not of recent litter‐derived carbon, but of DOC produced in these two horizons themselves. Water‐extractable organic carbon from labelled litter left in litterbags in the field for 4 months consisted of about one‐third native carbon from external sources at the experimental site and two‐thirds of the labelled litter. In contrast, the 13C content of the bulk litter from the litterbags was not changed by the incubation in the field. We suggest that the soluble native carbon in water extracts originated from throughfall DOC that had been assimilated by microorganisms in the litterbags.
Occurrence, prediction and hydrological effects of water repellency amongst major soil and land‐use types in a humid temperate climate
Authors: Doerr S. H. , Shakesby R. A. , Dekker L. W. , Ritsema C. J.
Published: May 2006

Knowledge of soil water repellency distribution, of factors affecting its occurrence and of its hydrological effects stems primarily from regions with a distinct dry season, whereas comparatively little is known about its occurrence in humid temperate regions such as typified by the UK. To address this research gap, we have examined: (i) water repellency persistence (determined by the water drop penetration time method, WDPT) and degree (determined by the critical surface tension method, CST) for soil samples (0–5, 10–15 and 20–25 cm depth) taken from 41 common soil and land‐use types in the humid temperate climate of the UK; (ii) the supposed relationship of soil moisture, textural composition and organic matter content with sample repellency; and (iii) the bulk wetting behaviour of undisturbed surface core samples (0–5 cm depth) over a period of up to 1 week. Repellency was found in surface samples of all major soil textural types amongst most permanently vegetated sites, whereas tilled sites were virtually unaffected. Repellency levels reached those of the most severely affected areas elsewhere in the world, decreased in persistence and degree with depth and showed no consistent relationship with soil textural characteristics, organic matter or soil moisture contents, except that above a water content of c. 28% by volume, repellency was absent. Wetting rate assessments of 100 cm3 intact soil cores using continuous water contact (–20 mm pressure head) over a period of up to 7 days showed that across the whole sample range and irrespective of texture, severe to extreme repellency persistence consistently reduced the maximum water content at any given time to well below that of wettable soils. For slightly to moderately repellent soils the results were more variable and thus hydrological effects of such repellency levels are more difficult to predict. The results imply that: (i) repellency is common for many land‐use types with permanent vegetation cover in humid temperate climates irrespective of soil texture; (ii) supposedly influential parameters (texture, organic matter, specific water content) are poor general predictors of water repellency, whereas land use and the moisture content below which repellency can occur seem more reliable; and (iii) infiltration and water storage capacity of very repellent soils are considerably less than for comparable wettable soils.
Reverse immunology approach for the identification of CD8 T‐cell‐defined antigens: Advantages and hurdles
Authors: Viatte Sebastien , Alves Pedro M , Romero Pedro
Published: May 2006

One of the challenges of tumour immunology remains the identification of strongly immunogenic tumour antigens for vaccination. Reverse immunology, that is, the procedure to predict and identify immunogenic peptides from the sequence of a gene product of interest, has been postulated to be a particularly efficient, high‐throughput approach for tumour antigen discovery. Over one decade after this concept was born, we discuss the reverse immunology approach in terms of costs and efficacy: data mining with bioinformatic algorithms, molecular methods to identify tumour‐specific transcripts, prediction and determination of proteasomal cleavage sites, peptide‐binding prediction to HLA molecules and experimental validation, assessment of the in vitro and in vivo immunogenic potential of selected peptide antigens, isolation of specific cytolytic T lymphocyte clones and final validation in functional assays of tumour cell recognition. We conclude that the overall low sensitivity and yield of every prediction step often requires a compensatory up‐scaling of the initial number of candidate sequences to be screened, rendering reverse immunology an unexpectedly complex approach.
Trait and Social Processes in the Link Between Social Support and Affect: An Experimental, Laboratory Investigation
Authors: Neely Lynn C. , Lakey Brian , Cohen Jay L. , Barry Robin , Orehek Edward , Abeare Christopher A. , Mayer Wendy
Published: May 2006

ABSTRACT
This study investigated the extent to which the link between perceived social support and affect reflected support recipients' trait perceived support as well as three distinct social processes: the objective supportiveness of providers, the unique relationships among recipients and providers that were stable over occasions, as well as the unique relationships that varied across occasions. Ten recipients interacted with each of the same four providers on five separate occasions, for a total of 200 interactions. Recipients and independent observers rated recipient affect and provider support. Greater perceived support was related to greater positive affect for recipients' trait perceived support, as well as for relationships that were stable over occasions and relationships that varied across occasions. No social support effects were found for negative affect. Perceived similarity was a consistent predictor of recipients' support perceptions. Implications for social support models and interventions were discussed.
A (New) Country Insurance Facility*
Authors: Cordella Tito , Levy Yeyati Eduardo
Published: May 2006

To cope with the self‐fulfilling liquidity runs that have triggered many recent financial crises, we propose the creation of a country insurance facility. The facility, which we envisage as complementary to the existing multilateral lending facilities, would provide eligible countries with automatic access to a credit line at a predetermined interest rate. Eligibility criteria should be easily verifiable, focus on debt sustainability, and take into account the currency and maturity composition of the debt. Other critical design issues considered here include the size of the facility, its duration and charges, and the exit costs for a country that loses eligibility.
Psychological health in patients with genital and oral erosive lichen planus
Authors: Lundqvist EN , Wahlin YB , Bergdahl M , Bergdahl J
Published: May 2006

Background  Erosive lichen planus is a severe, recurrent and recalcitrant disease that affects several mucosal areas, mostly the genital area and the mouth, but also, for example, the oesophagus and perianal area. The disease causes serious symptoms, because of the raw, de‐epithelialized mucosa and healing with scars/adhesions, which affect the patient's life in many ways. It causes, for example, difficulties in eating, drinking and going to the bathroom. Treatment is complicated and, so far, few therapeutic drugs other than steroids have been reported.

Objectives  As the disease has severe implications on the patient's life it is important to investigate the psychological health of the patients, as well as the influence of stress on their health and wellbeing, in order to improve treatment.

Study design, subjects and methods  Forty‐nine consecutive patients with erosive lichen planus were included during a 1‐year period. The study was carried out as ‘state‐of‐the‐last‐month’, and stress, state anxiety, depression and ‘erosive lichen planus factors’, i.e. symptoms affecting daily life, were assessed.

Results  Eighty‐seven per cent of the patients had symptoms, severely affecting daily life. Unexpectedly, oral symptoms seemed to be the most prominent. Our results showed that depression, anxiety and stress were more common in patients with erosive lichen planus than in a control group.

Discussion and conclusions  Erosive lichen planus is a severe disease with symptoms and complications affecting the patient's life. Our results indicate that their psychological health is also affected and emphasize the need for close collaboration between physicians, dentists with special knowledge in oral medicine and counsellors/psychologists to optimize handling of these patients.
Managing Earnings with Intercorporate Investments
Authors: Bøhren Øyvind , Haug Jørgen
Published: May 2006

Abstract:  We explore to what extent firms deliberately manage their financial reports by exploiting the flexibility of generally accepted accounting principles. Using a sample of Oslo Stock Exchange‐listed firms with 20–50% equity holdings in other firms, we find that firms with high financial leverage tend to maximize reported earnings from these investments through their choice between the cost method and the equity method, possibly in an attempt to reduce debt renegotiation costs or to avoid regulatory attention. In contrast, managers do not systematically bias reported earnings to extract private benefits or to signal revised expectations about future cash flows. Firms use different earnings management tools in a consistent way, as the earnings effect of the cost/equity choice is not offset by discretionary accruals.
SYNTHESIS OF AMINO ACIDS AND PROTEINS IN BARLEY SEEDLINGS
Authors: COCKING E. C. , YEMM E. W.
Published: May 2006

Summary

A study has been made of the assimilation of ammonium salts by young barley seedlings grown under controlled conditions in water culture. The synthesis of amino acids, amides and proteins in the roots was traced by means of isotopic labelling with 15N. Chromatographic analysis on ion‐exchange resins was used to separate the free and combined amino acids of the root tissues.

There was evidence of the synthesis of proteins in the roots under the experimental conditions. After short periods of assimilation, the soluble amides and amino acids, especially glutamine and glutamic acid, were highly labelled with 15N, indicating a rapid synthesis of these constituents. Subsequently, the abundance of 15N in the amino acids combined in the root proteins showed a marked increase. The data are consistent with the occurrence of an extensive synthesis and interconversion of amino acids and their utilization as precursors in the synthesis of proteins.

The importance of glutamic acid and glutamine in the assimilation of nitrogen and synthesis of amino acids is shown by the rapid incorporation of 15N into both the amide and amino groups. Other amino acids are more slowly labelled and may be formed secondarily by transamination or interconversion. γ‐Aminobutyric acid appears to play a significant part in the metabolism of the roots, since it is formed at an early stage of assimilation. The labelling of γ‐aminobutyric acid with 15N indicates that, in barley seedlings, it is a secondary product, rather than a precursor of glutamic acid or glutamine.
OBSERVATIONS ON POPULATION STRUCTURE AND LONGEVITY OF FESTUCA RUBRA L.
Authors: HARBERD D. J.
Published: May 2006

Summary

The basic material of this study was two collections of Festuca rubra from the local hills. The one collection was of 1481 plants all gathered from within a 100 square‐yard quadrat; the other of 340 plants was of wider distribution.

Detailed morphological examination of the material growing as spaced plants suggested that relatively few genotypes were present. Further work, involving a replicated field trial and an investigation of self‐and cross‐incompatibility corroborates this view. One of the genotypes occurs abundantly within an area of more than 240 yards diameter.

Among the genotypes there were considerable differences of colony size and density. There were also indications of differences in ecological requirements.

In the field trials there is no indication that plant characters within a clone are in any way affected by the environment from which the material was gathered.

A consideration of the presumed age of the genotypes and the vigour of their vegetative spread suggests that very little ecotypic differentiation can be taking place in F. rubra at the present time. Any observable differentiation must have taken place either before colonization or during its early stages.
ABSORPTION OF PHOSPHORUS FROM SOILS BY MYGORRHIZAL PLANTS
Authors: MORRISON T. M.
Published: May 2006

Summary

Transfer of 32P to the shoots of non‐mycorrhizal and mycorrhizal plants of Pinus radiata growing in soil and in expanded perlite has been comparedby assaying the amount reaching the shoot apex.

In expanded perlite and in soils with low phosphorus‐sorption capacities movement of 32P to the shoot apex of non‐mycorrhizal plants was rapid during an initial phase but reduced in rate during a prolonged second phase. Movement of 32P to the shoot‐tip of mycorrhizal plants, however, was at a relatively steady rate, which eventually exceeded that in non‐mycorrhizal plants.

In soils of high phosphorus‐sorption capacity the rate of movement was reduced but followed the same course as that from expanded perlite. Transfer of 32P to the shoots of both mycorrhizal and non‐mycorrhizal plants was negligible over a short period from a soil of very high phosphorus‐sorption capacity.

It is suggested that the apparent solubilizing effects of mycorrhizas on soil phosphorus may simply be a consequence of the rapid withdrawal of labile phosphorus by the mycorrhizal sheath.
SOME OBSERVATIONS ON NATURAL CLONES IN FESTUCA OVINA*
Authors: HARBERD D. J.
Published: May 2006

Summary

Evidence is presented in support of the hypothesis that ramets of the same natural clone of Festuca ovina in hill grazings may be collected from points up to 10 yd apart. When a reasonable estimate is made of the annual rate of growth of such clones it appears that their age is to be measured in centuries.

During the first stage of the work, which is not described in detail, 1050 plants were collected from defined points within a 10‐yd square quadrat and examined morphologically. Several fairly homogeneous groups were recognized and four are described. In the second stage, experiments were conducted with these groups to determine which plants could be regarded as isoclonal.

In ‘cloned clone’trials some of the characters were noticeably discontinuous in distribution and using these a more satisfactory clonal classification of the groups was achieved. From cross‐pollination tests it was concluded that morphologically distinct plants were cross‐compatible whereas morphologically similar plants were cross‐incompatible and yielded no more seed from this crossing than they did on selfing. This type of test, therefore, confirmed the reality of the morphological groupings.

Characters with a more continuous distribution in the ‘cloned clone’trials behaved differently. There were statistically significant differences between isolates within supposed clones in these characters but some, and it is assumed all, of the difference could be traced to a virus infection of the material. A separate trial, where infection was introduced in a controlled manner from plants derived from the ‘cloned clone’experiments, indicated that this interpretation was not unreasonable.

When allowance is made for the differences between the two species it is evident that natural clones of F. ovina closely parallel those of F. rubra in respect of their temporal and spatial distribution in hill grazings.
ETHYLENE‐STIMULATED GROWTH AND AUXIN ANSPORT IN RANUNCULUS SCELERATUS PETIOLES
Authors: MUSGRAVE ALAN , WALTERS JOHN
Published: May 2006

Ranunculus sceleratus petioles elongate rapidly when submerged or treated with ethylene. The concentration of ethylene in submerged plants is approximately 7 nl ml‐, sufficient to account for the submerged response. Ethylene (50 nl ml‐1) enhances IAA transport through petiole sections within 1 hour of treatment.
LIGHT AND ELECTRON MICROSCOPE OBSERVATIONS ON ALGAL LYSIS BY BACTERIUM CP‐I
Authors: DAFT M. J. , STEWART W. D. P.
Published: May 2006

Bacterium CP‐I isolated from Scottish waters is an aerobic prokaryote with a high guanine: cyto‐sine ratio (68%), which causes lysis of a variety of blue‐green algae. When suspensions of algae and bacteria are mixed the bacteria can be seen to glide towards the algae where they become attached end‐on round the algal cells. There is evidence that the bacteria produce substances at the point of contact with the algae which are necessary for algal lysis to occur. Lysis of vegetative cells may occur within 30 minutes of the bacteria becoming attached. Heterocysts do not lyse in this way although their intracellular contents may eventually degenerate. When vegetative cells rupture, the protoplasmic contents, including gas vacuoles when present, are released and empty‐looking ‘ghosts’ which retain the original cell shape may remain for a time although these too eventually break down. There is some evidence that the mode of filament lysis may be random, intercalary or terminal.

At the ultrastructural level the initial effect of CP‐I is to cause lysis of the L2 layer of the algal cell wall and this effect is similar to that obtained using lysozyme. This is followed by rupture or disintegration of the other cell wall layers, and ‘scroll’‐like structures, either of coiled up cell wall material (Microcystis) or of the plasmalemma (Nostoc) may be found scattered throughout the preparations of lysed cells. In fully lysed cells there is a loss of polyphosphate bodies, structured granules, gas vacuoles, and most other cellular inclusions. Released gas vesicles can be collected from the surface of the solution of lysed cells, and there is evidence that these vesicles may fracture easily near the conical ends. In fully lysed cells, the thylakoid membranes remain, often with wide lumens between. This thylakoidal system is contorted and branched, ramifies through the cell and shows constrictions of the membrane system at intervals. Continuity between the plasmalemma and the thylakoidal system can be seen clearly, Lipid droplets which are resistant to CP‐I treatment are found in the lumen of the thylakoidal system. Heterocysts are not as markedly affected by CP‐I as are vegetative cells, but eventually heterocyst disorganization also occurs. The use of CP‐I provides a technique for preparing material for the study of algal membranes and gas vesicles.
QUANTITATIVE INTERFEROMETRY OF ONION EPIDERMAL NUCLEI IN DEVELOPMENT AND IN SENESCENCE
Authors: KULFINSKI F. B. , PAPPELIS A. J.
Published: May 2006

Nuclei of onion (Allium cepa L.) bulb scale inner epidermal cells were found to increase in area, dry mass per unit area, and total dry mass with increasing age and distance of the scales from the centre of the bulb. The above nuclear characteristics reached maxima which were, respectively 4.1, 1.4, and 5.0 × those of the youngest scale studied (the oldest unemerged leaf). A sharp increase in these three characteristics in scale 2 is interpreted as reversible change due to senescence. The outermost turgid scale, i.e. the oldest, exhibited the increased nuclear dry mass concentration and decreased nuclear area and nuclear dry mass which characterize nuclear pyenosis. The outermost scale is therefore interpreted as exhibiting irreversible change due to senescence.
MAINTENANCE OF THE RUST, PUCCINIA POARUM, ON ITS ALTERNATE HOSTS UNDER CONTROLLED CONDITIONS
Authors: MCGEE E. E. M. , HOLLIGAN P. M. , FUNG A. K. , LEWIS D. H.
Published: May 2006

Methods by which the rust, Puccinia poarum, may be maintained on its alternate hosts, Tussilago farfara and Poa spp., are described. Telial material collected in the autumn requires extensive washing and drying before teliospores will infect Tussilago, but telial material collected after a winter in the field, in mid‐summer or from plants infected in the laboratory do not require this treatment. Infection of Poa pratensis and P. trivialis can readily be achieved from aeciospores or urediospores. Some advantages of this rust for research and teaching are stated.
APICAL WALL STRUCTURE IN HYPHAE OF PHYTOPHTHORA PARASITICA
Authors: HUNSLEY D.
Published: May 2006

Apical hyphal walls in rapidly growing 48‐hour cultures of Phytophthora are significantly thinner than mature non‐apical walls from 7‐day cultures. Enzymic treatments have shown that in young apices the outer layer of wall glucan is attenuated as compared with mature regions and it is suggested that there is less protein associated with the cellulose microfibrils in the inner part of the wall.
NITROGEN FIXATION BY LUPINUS ARBOREUS GROWN IN THE OPEN AND UNDER DIFFERENT AGED STANDS OF PINUS RADIATA
Authors: SPRENT JANET I. , SILVESTER W. B.
Published: May 2006

An intensive 3‐month study of nitrogen fixation by Lupinus arboreus grown on open sand dunes and under different aged stands of Pinus radiata in New Zealand has been carried out. Nodule samples were obtained either by digging whole seedlings or by sieving 0.01 m3 soil cores. Nitrogen fixation as estimated by the acetylene reduction assay and 15N analysis agreed well with published data from biomass studies. On open dunes nodule growth and activity increased rapidly during spring and estimated nitrogen fixation reached a peak of 11.5 kg N ha‐1 week‐1 at about flowering. When fruits began to swell, both on open dunes and in forest sites, nitrogen fixation by lupins decreased.

Light transmission in forest sites was not correlated with the time of pine thinning. Lupin growth, nodule biomass and nitrogen fixation in non‐flowering lupins was closely related to the amount of light transmitted. When the sand became very dry nitrogen fixation was reduced and moisture stress was considered to be a factor likely to limit nitrogen fixation in drier parts of the year.

Nitrogen fixation by lupin within forest stands on sand dunes is sufficient to make a significant contribution to the nitrogen economy of the forest.
THE EFFECTS OF IMBIBITION DRYING TREATMENTS ON WHEAT SEEDS
Authors: HANSON A. D.
Published: May 2006

Wheat seeds were imbibed and re‐dried under conditions that did not give rise to radicle protrusion through the seed coat. When seeds pre‐treated in this way were planted in moist vermiculite, coleoptile emergence was faster than from untreated seeds. This advancing effect on coleoptile emergence (‘seed invigoration’) was most marked when the seedlings were grown at low temperature or under osmotic stress (i.e. under unfavourable conditions). The seed‐borne pathogen Septoria nodorum was not affected by an imbibing‐drying treatment.

Conditions of imbibition and drying giving optimal invigoration are described and data on the metabolism of untreated and invigorated seeds are presented. Oxygen uptake and [14C]‐leucine incorporation into protein were more enhanced in aleurone layers than in embryos isolated from invigorated seeds. Both untreated and invigorated seeds showed very low α‐amylase levels when dry, although a‐amylase activity developed more rapidly in invigorated seeds during germination. Gibberellic acid alone was not able to replace an imbibing‐drying treatment.
EXUDATION OF 14C‐LABELLED COMPOUNDS FROM WHEAT ROOTS: INFLUENCE OF NUTRIENTS, MICRO‐ORGANISMS AND ADDED ORGANIC COMPOUNDS
Authors: ROVIRA A. D. , RIDGE E. H.
Published: May 2006

When tops of 6‐day wheat seedlings grown in nutrient solution, sterile or inoculated with soil, received 14CO2, it was found that the radioactivity of the solution measured after 24 and 48 hours was reduced by the presence of micro‐organisms. Omission of phosphate from the sterile growth medium reduced the radioactivity of the root solution to 47% of the control. The addition of acetate buffer at pH 5 greatly increased exudation whereas the adjustment to a similar pH with H2SO4 or universal buffer or the addition of sodium acetate at pH 7 significantly reduced exudation.

These results demonstrate that exudation of organic compounds from roots can be affected by the addition of substrates and butters used in root enzyme studies. From these results, it appears that some organic compounds in soil could influence the loss of carbon compounds from roots growing under natural conditions.
INHIBITOR LEVELS ASSOCIATED WITH GROWTH IN SEEDLINGS OF PINUS RADIATA
Authors: SWEET G. B. , ROOK D. A.
Published: May 2006

The conditioning of Pinus radiata D. Don seedlings to withstand transplanting stress involves the use of a mechanical root undercutting technique. Using the Avena coleoptile bioassay the differences in hormone levels in acidic extracts of the shoots and roots of conditioned and control seedlings were determined. Conditioned seedlings had roots with higher relative growth rates and lower levels of inhibitors per unit of root weight than non‐conditioned seedlings.
THEORY AND PRACTICE OF INDUCED ANDROGENESIS
Authors: PANDEY KAMLA K.
Published: May 2006

The recently discovered technique of producing haploid plants from the culture of immature anthers of flowering plants (androgenesis) is potentially of great significance in plant breeding and genetics. Although rare haploid plants have been obtained by this method in a variety of species thus demonstrating the wide applicability of the technique, the method so far has been successful for only a very few species in producing a large number of haploid plants with ease and certainly. New variations of the technique involving, in general, modifications in the nutrient media and other environmental factors of anther culture, are being tried in different laboratories. Here, some of the theoretical aspects of anther culture are discussed with a view to contributing towards a better understanding of the phenomenon, and thus possibly to help in expediting practical androgenesis.
ARILS AND ARIL‐LIKE STRUCTURES IN WOODY RANALES
Authors: ENDRESS P. K.
Published: May 2006

The arils and aril‐like structures of one species of all woody Ranalean families, in which ‘arils’ are reported, have been investigated ontogenetically and comparatively. In Myristicaceae and some Annonaceae soft enations occur on the seeds, in Siparuna (Monimiaceae 8.1.) on the carpels, and in Hedyosmum (Chloranthaceae) even on the outer side of the flower. In these examples both the evolutionary possibilities, convergence and transference of function, are compared. It seems that the different sites of such enations are due to convergence, whereas the change of the dispersal units themselves and of their protecting organs are due to transference of function. We are drawn to the conclusion that arils are probably neither especially primitive nor homologous in all angiosperms, because such convergences already occur within one single order–an order which is generally considered, moreover, to be particularly primitive.
A NOTE ON THE EVOLUTIONARY STATUS OF TAPETAL TYPES IN DICOTYLEDONS
Authors: SPORNE KENNETH R.
Published: May 2006

The glandular type of tapetum in dicotyledons is shown statistically to be correlated with four primitive characters. It is concluded, therefore, that this kind of tapetum is primitive, while the amoeboid type is advanced.
THE SURVIVAL OF ARCHAIC DICOTYLEDONS IN TROPICAL RAIN‐FORESTS
Authors: SPORNE KENNETH R.
Published: May 2006

Twelve characters are more abundant among rain‐forest families of dicotyledons than they are in the flora of the world. Nine of these were more abundant in pie‐Tertiary or pre‐Oligocene times than they are at the present day. It is argued, therefore, that these characters are archaic survivals in present‐day rain‐forests.
CARBON TRANSFER FROM THE BLOOM NODE LEAF TO THE FRUIT OF VICIA FABA L.
Authors: KIPPS A. , BOULTER D.
Published: May 2006

14CO2 was fed to the bloom node leaf subtending 30‐35‐day‐old broad bean pods, and the leaf, pod and seeds harvested during 19 hours. An immediate transfer of label from leaf to fruit was observed. During the night, a second peak of activity occurred in the fruit owing to an influx of labelled carbohydrate into the seed, but this was not at the expense of leaf carbon. Possible sources of this carbohydrate are discussed.
THE EFFECTS OF LOW CONCENTRATIONS OF SULPHUR DIOXIDE ON STOMATAL BEHAVIOUR IN VICIA FABA
Authors: BISCOE P. V. , UNSWORTH M. H. , PINCKNEY H. R.
Published: May 2006

The stomatal resistance of leaves of Vicia faba L., measured using a diffusion porometer, rapidly decreased when plants were exposed to air containing SO2. The stomatal resistance decreased by 20% for the SO2 concentrations used (140, 290 and 1430 μg m‐3) and the minimum concentration to which stomata responded was 72 μg m‐3. Although stomatal resistance increased with leaf age, when exposed to 290 μg‐3 SO2, the opening response was larger and more rapid in the older leaves. Exposure to 290 μg m‐3 SO2 throughout a day suppressed the normal diurnal variation in stomatal behaviour and reduced the stomatal resistance by 25%. It was estimated that the measured stomatal responses to SO2 would increase the transpiration rate by 32% for single leaves in a growth room and by 23% for a field crop.
THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE
Authors: PEARSON V. , READ D. J.
Published: May 2006

Translocation of nutrients is demonstrated in mycorrhiza of ericaceous plants. [14C]glucose and [32P]orthophosphate are translocated over limited distacnes by the endophyte in pure culture. 32P is translocated to mycorrhizal host plants over distances and at rates which are related to the size of the host plants. Photosynthates from the higher plant are translocated from the roots to the external mycelium of the endophyte. The possible ecological significance of these findings is discussed.
MAGNESIUM ACTIVATION OF PHOTOSYNTHETIC CO2‐FIXATION IN A RECONSTITUTED CHLOROPLAST SYSTEM
Authors: LILLEY R. McC. , HOLBOROW K. , WALKER D. A.
Published: May 2006

Summary

Measurements of O2‐evolution by a reconstituted chloroplast system showed that photosynthetic electron transport and 3‐phosphoglycerate reduction proceed at rapid rates in the presence of 0.5‐1 ran MgCl2. However, to obtain maximal rates of CO2‐dependent O2‐evolution under these conditions, it was necessary to increase the Mg concentration to 5 mM (70‐90% of the maximum rate was observed at 2.5 mM Mg). Rapid rates of CO2‐dependent O2 evolution were also recorded at 1 mM Mg when the bicarbonate concentration was increased from 1 to 40 mM. Simultaneous measurements of 14CO2 fixation and O2 evolution in the presence of ribulose‐1, 5‐diphosphate confirmed that the additional Mg was required for the carboxylation step and showed that the Mg activation was a more rapid process than the kinetics of CO2‐dependent O2 evolution might suggest.
STOMATAL MOVEMENTS IN EXCISED LEAVES: SOME EFFECTS OF SODIUM AZIDE
Authors: PEMADASA M. A.
Published: May 2006

Summary

The effect of sodium azide upon the stomatal behaviour in excised leaves of Stachytarpheta indica was studied by microscopic examination of epidermal strips fixed in absolute ethanol. Azide was found to retard stomatal opening on both illumination of turgid leaves and wilting of excised leaves; it did not, however, affect stomatal closure. Carbon dioxide‐free air was effective in compensating the azide effect. It appears that, in addition to the leaf water balance, changes in the rates of such processes as photosynthesis resulting from leaf excision also have controlling effects on stomatal movements by disturbing the level of carbon dioxide in the intercellular spaces and it is concluded that azide may retard stomatal opening by its effect on these processes. Changes in starch in the guard cells apparently play a subsidiary role in these stomatal responses.
RESPONSES OF CALLUS FROM ZYGOTAL AND MICROSPORAL TOBACCO (NICOTIANA TABACUM L.) TO VARIOUS COMBINATIONS OF INDOLE ACETIC ACID AND KINETIN
Authors: de FOSSARD R. A.
Published: May 2006

Summary

Calluses from zygotal and microsporal plants of Nicotiana tabacum L.cv. Maryland Mammoth exhibited similar growth and morphogenetic responses to culture on twelve media consisting of a basal medium and all combinations of IAA (0, 1 × 10−5 M, 2 × 10 −5 M) and kinetin (0, 10−7 M, 10−6 M, 10−5 M). Five types of callus morphology are described, ranging from a loose soft‐textured type to a compact more or less radially symmetrical type and to a nodular type which was associated with regeneration of shoots. Anatomically the cell types ranged from thin‐walled isodiametric cells to elongated cells and to parenchyma of various shapes showing organized development. Particularly interesting was the induction of numerous individual tracheid‐like cells of diverse shapes making up about 60% of the cell population in calluses grown on 10−5 M kinetin medium with cither 1 or 2 × 10−5 M IAA. This contrasted with the complete absence of tracheary elements in calluses reared on kinetin‐free 10−5 M IAA medium, and the development of xylem on auxin‐free 10−5 M kinetin medium. The need for the introduction of the words microsporal and zygotal in connection with plants derived from anther, microspore and pollen grain culture is discussed.
THE EFFECTS OF VARIOUS AUXINS AND CYTOKININS ON THE IN VITRO CULTURE OF STEM AND LIGNOTUBER TISSUES OF EUCALYPTUS BANCROFTII MAIDEN*
Authors: LEE EDWARD C. M. , de FOSSARD R. A.
Published: May 2006

Summary

Calluses from stem tissues and from lignotubers were grown on various combinations of auxins (1AA*. NAA, 2,4‐D, NOA)and cytokinins(kinetin, BAP) in an attempt to induce regeneration of organs. Regeneration was not achieved, but substantial differences in growth were obtained. Best growth occurred on basal medium with 2 × 10 −5 M NOA and 16 × 10−6 M BAP (for stem calluses) and 2 × 10−5 M 2,4‐D and 2 × 10−6 M BAP (for lignotuber calluses).
LATERAL ROOT ELONGATION IN VICIA FABA L.: CHANGES IN LABELLING INDEX IN THE CAP, EPIDERMIS, CORTEX AND STELE
Authors: MACLEOD R. D. , McLACHLAN S. M.
Published: May 2006

Summary

Labelling index (LI) was determined in the cap, epidermis, cortex and stele over the apical mm of newly emerged, 0.2, 0.5 → 2 and 4 cm long secondary roots of Vicia faba. This parameter increased in each of the tissues investigated as the roots lengthened. These results have been discussed with respect to the onset of meristematic activity in more or less quiescent lateral root primordia about the time they elongate to form secondary roots.

LI was also different in the epidermis, cortex and stele in roots of any one length. These differences were more evident in the more basal parts of the laterals examined and they increased with root elongation. On the basis of these results and others in the literature, it is suggested that changes in LI reflect one of the initial events taking place at the onset of cell differentiation and that it may be possible to study differentiation by examining cells from comparable parts of lateral roots which are at different stages of development.
LICHEN PHYSIOLOGY
Authors: GREEN T. G. A. , SMITH D. C.
Published: May 2006

Summary

The pattern of 14C fixation and release by algae after isolation from lichens was studied using Nostoc from Peltigera canina, Hyalococcus from Dermatocarpon miniatum. Coccomyxa from Peltigera aphthosa and Trebouxia from Xanthoria aureola; cultured strains of these algae were also investigated. In all cases, the following changes occur as soon as the algae are isolated: (a) release of fixed 14C to the medium declines sharply; (b) the proportion of released 14C incorporated into simple carbohydrates also falls rapidly; and (c) incorporation into ethanol‐insoluble material in the cell rises substantially. The direction of these changes is towards the behaviour of cultured algae. It is concluded the lichen algae begin to show substantial changes from their behaviour in symbiosis as soon as they are separated from the fungus.
THE ACCLIMATIZATION OF PLANTS TO CHILLING TEMPERATURES IN RELATION TO THE FATTY‐ACID COMPOSITION OF LEAF POLAR LIPIDS
Authors: WILSON J. M. , CRAWFORD R. M. M.
Published: May 2006

Summary

An examination was made of the effects of low‐temperature acclimatization on the fatty‐acid composition of the polar lipids of two chill‐sensitive species Gossypium hirsutum and Phaseolus vulgaris which harden readily against chilling injury. As controls, the effect of hardening temperatures on a chill‐resistant species, Hordeum vulgare, and a chill‐sensitive species, Episcia reptans, which did not harden were also investigated. The degree of unsaturation of the fatty acids associated with the phospholipid fraction increased during hardening of Gossypium hirsutum and Phaseolus vulgaris. Furthermore, the degree of unsaturation and weight of phospholipids decreased in the leaves of these species with increase in physiological age at 25° C and was related to the increased susceptibility of older leaves to chilling injury. The acclimatization treatment produced no effects on the fatty‐acid composition of the glycolipids of these plants and this agreed with earlier observations which showed no increase in unsaturation of the total leaf fatty acid on hardening (Wilson and Crawford, 1974). Therefore, in leaves, it was the phospholipid fraction alone and representing only 22% of the total leaf fatty acids that had its degree of unsaturation positively related to the chilling tolerance of the species investigated. These findings are discussed in relation to similar ones made on the acclimatization of animals to low temperatures.
STUDIES ON TUBERIZATION OF SOLANUM ANDIGENA
Authors: KUMAR D. , WAREING P. F.
Published: May 2006

Summary

The role of various growth‐regulating substances in tuberization in Solarium andigena was studied (1) by application of exogenous growth regulators, and (2) by studying variation in the levels of endogenous hormones under tuber‐inducing and non‐inducing conditions. In short‐day induced cuttings tuberization was inhibited by gibberellic acid; indole acetic acid and kinetin (6‐furfuryl amino purine) caused slight stimulation of tuber growth at low concentrations, but inhibited it at higher concentrations. Application of (2‐chloroethyl) trimethyl‐ammonium chloride (CCC) promoted tuberization in plants growing under non‐inducing long‐day conditions and in buds produced on isolated plugs of tuber tissue. The tuber‐inducing effects of CCC were not reversed by simultaneous application of GA3. Levels of endogenous gibberellins decreased markedly under short‐day conditions, but there was no difference in the levels of endogenous abscisic acid under long and short days. The reduced levels of gibberellins were maintained for at least 2 weeks when induced plants were transferred from short‐day to long‐day conditions. Application of CCC under conditions which promoted tuberization caused a reduction in gibberellin levels. The role of growth hormones in the regulation of tuberization is discussed.
ASSESSMENT OF STOMATAL CONTROL OF PLANT WATER STATUS
Authors: JONES HAMLYN G.
Published: May 2006

Summary

Two methods for studying the role of stomata in controlling leaf water status are compared, using data for field grown spring wheat (Triticum aestivum L.). The first is based on comparisons of leaf water potential and stomatal conductance and their responses to different soil water treatments as obtained by irrigation or by placing plastic rainwater gutters between rows to remove a proportion of the incident rainfall. The second method exploits the varying potential evaporation and the consequent changing leaf water potential and stomatal conductance during the course of a day. Good stomatal control is indicated by large values of the ratio of the amount of variation in stomatal conductance to that of leaf water potential. A particular advantage of the latter method is that it does not require a range of soil water treatments, and it can therefore be more readily used to compare the degree of stomatal control in a range of genotypes. There was generally good agreement between the methods, with the second method showing greater sensitivity.

Stomatal conductances were measured with a continuous flow diffusion porometer which had a thermostatically controlled leaf chamber. This feature had the advantage that conductances could be obtained directly from the output of the humidity sensor without the necessity for routine measurement of, and correction for, leaf temperature.