bluuebunny/crossref_metadata_2025 huggingface dataset:
Transformation and regeneration of transgenic aspen plants via shoot formation from stem explants
Authors: Tzfira Tzvi , Jensen Christian Sig , Vainstein Alexander , Altman Arie
Published: May 2006

An Agrobacterium‐mediated transformation procedure for aspen (Populus tremula L.), involving the direct regeneration of shoot‐buds from stem explants, is described. Disarmed Agrobacterium tumefaciens strain EHA101 harboring the binary plasmid pKIW1105 (which carries the uidA and nptII genes, coding for β‐glucuronidase [GUS] and neomycin phosphotransferase II, respectively) was used for the transformation of stem explants. An incubation period of 48 to 72 h was found to be most effective in terms of transient GUS expression on the cut surface of the stem explants. Adventitious shoots regenerated after 2–3 weeks of culture in a woody plant medium (WPM) supplemented with TDZ (1‐phenyl‐3‐[1,2,3‐thiadiazol‐5‐yl]‐urea, Thidiazuron) and carbenicillin. Three different kanamycin‐based selection schemes were evaluated for optimization of transformation efficiency: (1) Kanamycin was added only to the rooting medium (5 to 6 weeks post‐inoculation), or (2) to the regeneration medium 10–14 days after inoculation, or (3) after 2 days of co‐cultivation. The third selection scheme was found to be optimal for adventitious shoots with regard to both the time required and the transformation efficiency, the latter being much higher than with the other schemes. Leaf samples from kanamycin‐resistant shoots and plantlets were tested for GUS expression, and subjected to polymerase chain reaction (PCR) analysis of uidA and nptII genes. A Southern blot of the corresponding PCR‐amplified fragments confirmed their authenticity and Southern blots of total plant DNA confirmed integration of the nptII gene into the plant genome.
A reconsideration of terminology in Frankia research: A need for congruence
Authors: Akkermans A. D. L. , Hirsch A. M.
Published: May 2006

Progress in understanding the Frankia‐actinorhizal symbiosis has paralleled that of the Rhizobium‐legume symbiosis. Previously, these two nitrogen‐fixing symbioses have been considered as distinct and unrelated entities. However, it seems likely that many of the developmental stages, and perhaps even the molecular signals, are shared between these two apparently independent associations. For this reason, we propose to emphasize the similarities between the two symbioses by calling for a uniformity of terminology to describe nodule development.
Transformation of Papaver somniferum cell suspension cultures with sam1 from A. thaliana results in cell lines of different S‐adenosyl‐L‐methionine synthetase activity
Authors: Belny Muriel , Hérouart Didier , Thomasset Brigitte , David Hélène , Jacquin‐Dubreuil Annie , David Alain
Published: May 2006

We have developed a procedure for opium poppy (Papaver somniferum) transformation using Agrobacterium tumefaciens‐mediated gene delivery. Hypocotyl‐derived cell suspension cultures of P. somniferum were cocultivated with A. tumefaciens strain GV3101(pMP90) harbouring either the binary vector pTHW136 or the binary vector pO35SSAM. The former contained the uidA reporter gene and the nptII selectable gene, encoding the enzymes β‐glucuronidase and neomycin phosphotransferase II, respectively. The latter contained the sam1 gene encoding the enzyme S‐adenosyl‐L‐methionine (SAM) synthetase and the nptII gene. Putatively transformed cell lines were selected on media supplemented with paromomycin. Integration of the foreign genes was confirmed by Southern blot analysis with and without PCR amplification prior to hybridization. SAM synthetase activity was measured in extracts of 5 transformed cell lines. One of them expressed a significant overactivity while two others had a lower activity than the control cell line, leading us to question the possible partial cosuppression of both the resident and the foreign sam genes. To our knowledge, this is the first report of Agrobacterium tumefaciens‐mediated transformation of Papaver somniferum cell suspension cultures.
Effect of chilling on the diurnal rhythm of enzymes involved in protection against oxidative stress in a chilling‐tolerant and a chilling‐sensitive maize genotype
Authors: Kocsy Gábor , Owttrim George , Brander Karl , Brunold Christian
Published: May 2006

The effect of chilling on diurnal changes in activity of adenosine 5′‐phosphosulfate sulfotransferase, glutathione reductase (EC 1.6.4.2) and glutathione transferase (EC 2.5.1.18) was analysed in the second leaf of Z 7, a chilling‐tolerant, and Penjalinan, a chilling‐sensitive maize (Zea mays L.) genotype. Nitrate reductase (EC 1.6.6.1) was measured for comparison. All enzyme activities examined changed with a typical diurnal rhythm in both genotypes cultivated at 25°C. Adenosine 5′‐phosphosulfate sulfotransferase and nitrate reductase activity peaked during the light period, then decreased and reached lowest levels at the end of the dark period. Glutathione reductase activity increased in the dark and decreased during the light period. Maximum glutathione transferase activities were measured in the middle of the light period, minimal ones in the middle of the dark period. At 12°C these diurnal changes were eliminated in all enzymes examined of both genotypes.

The average adenosine 5′‐phosphosulfate sulfotransferase and glutathione reductase activity were higher in the chilling‐tolerant Z 7 than in the sensitive Penjanilan at 12°C in the light. Increased levels of both enzymes may contribute in establishing increased levels of cysteine and reduced glutathione in the chilling‐tolerant Z 7. Indeed it has been shown before that the chilling‐tolerant maize genotypes contain higher levels of both compounds at low temperatures than chilling‐sensitive ones.
A Lupinus albus root glycoprotein homologous to the polygalacturonase inhibitor proteins
Authors: Manuela Ribeiro Costa M. , Costa Júlia , Pinto Ricardo Cândido P.
Published: May 2006

A glycoprotein with an apparent molecular mass of 42 kDa (GP42), detected in the roots of Lupinus albus L. (cv. Rio Maior), was found to increase along the root axis with increasing distance from the apex and to be induced in roots cultured in vitro upon exogenous supply of high IAA (10‐3M). GP42 is ionically bound to the cell wall, it has a pl>8.3, and it is N‐glycosylated. The purification of GP42 was accomplished by affinity chromatography (ConA‐Sepharose) followed by cation‐exchange chromatography (Mono S). The amino acid sequence of the amino terminal part of the protein shows 70% identity to that of polygalacturonase inhibitor proteins (PGIPs) from other species. GP42 inhibits the polygalacturonase activity from Aspergilltus niger in vitro suggesting that it is a PGIP. The possible relationship between the L. albus PGIP and root development is discussed.
Carotenoid‐deficient young wheat etioplasts are able to bind precursor proteins on the plastid surface but are impaired in their translocation ability
Authors: Dahlin Clas , Franzén Lars‐Gunnar
Published: May 2006

Young carotenoid‐deficient etioplasts, isolated from Norflurazon (NF)‐treated wheat seedlings, were used to study the role of coloured carotenoids in the binding and import reactions of different nuclear‐encoded plastid proteins. Plastids from control seedlings exhibited significantly higher import efficiencies than did plastids from NF‐treated plants. Etioplasts containing normal levels of carotenoids imported approximately 2000 and 800 molecules per plastid of the precursors of the small Rubisco subunit (pSS) and the Rieske FeS protein (pFeS), respectively. Plastids from NF‐treated plants imported approximately 100 and 70 pSS and pFeS molecules per plastid, respectively. In addition, a maximum binding capacity of NF‐treated plastids of 1200 protein molecules per plastid was observed for both pSS and pFeS when assayed at 25°C: and a maximum binding capacity of approximately 1300 molecules per plastid was noted at 4°C. For control plastids, a similar amount of binding, or approximately 1400 protein molecules per plastid, could only be observed if import was inhibited by low ATP concentrations at 4°C. When these plastids were washed and transferred to conditions promoting import at 25°C and 10 mM Mg‐ATP, close to 60% of the envelope‐associated precursor protein molecules were imported. These results indicate that control and NF‐treated young etioplasts contain similar amounts of binding sites for precursor proteins. However, only in the case of control plastids the binding was productive and lead to import and processing in the stroma upon transfer to conditions promoting import. Plastids isolated from wheat seedlings grown in weak red light and containing different amounts of carotenoids, were assayed for their ability to bind and import a protein with unusual import characteristics, the Chlamydomonas reinhardtii PsaF precursor of PSI (pPsaF) and transit peptide deletion constructs. The PsaF protein was imported in a transit peptide‐dependent manner into control etioplasts, whereas import of pPsaF into young wheat etioplasts isolated from NF‐treated plants was inhibited at low levels of plastid carotenoids.
Superoxide dismutase, catalase and nitrogenase activities of symbiotic Frankia (Alnus incana) in response to different oxygen tensions
Authors: Alskog Gunnar , Huss‐Danell Kerstin
Published: May 2006

Presence and activity of the enzymes superoxide dismutase (SOD) and catalase were studied in Frankia in symbiosis with Alnus incana (L.) Moench. Analysis on native PAGE gels indicated that symbiotic Frankia contained an FeSOD and catalase. The activity of the enzymes was in the same range as reported for cultured Frankia. Attempts to characterize SOD by western blots with antisera from Escherichia coli and Azotobacter vinelandii did not give clear‐cut results with the antibodies used. Alnus incana plants were grown with the root system in 5, 10, 21 or 40% O2 for up to 6 days. Nitrogenase activity, measured as ARA (acetylene reducing activity) dropped within 3 h when roots were exposed to low or high oxygen. At 40% O2 ARA was almost completely lost while at 5 and 10% O2 ARA decreased to 69 and 74% of the inital value, respectively, Nitrogenase activity recovered at ail oxygen tensions. Recovery rates resembled the continuous increase in ARA in plants continuosly kept at 21% O2, and suggests that new vesicles with envelopes of appropriate thickness were formed. The ARA measurements confirm results from an earlier study where nitrogenase activity was measured as H2 evolution. There was a tendency for increased SOD and catalase activities in Frankia from root systems exposed to 40% O2 for 24 h but not earlier or later than this. When data from all experimental times were pooled. SOD activity increased significantly with increased oxygen tension whereas catalase activity decreased. Although ARA per plant varied with oxygen tension, there was no statistically significant correlation between ARA and SOD or between ARA and catalase. It seems that being linked to nitrogenase activity is only one role of SOD and catalase in this symbiotic Frankia.
Differential expression of Bcl‐2, Bcl‐XL and p53 in colorectal cancer
Authors: Han Hye Seung , Park Young‐Mee , Hwang Tae Sook
Published: May 2006

Aims:  The balance between proliferation and apoptosis is often disturbed in cancer. The aim of this study was to investigate the possible role of Bcl‐2 gene family members and p53 as prognostic factors in a series of colorectal cancer.

Methods:  The immunohistochemical expression of Bcl‐2 gene family members (Bcl‐2 and Bcl‐XL) and p53 was evaluated in 81 surgical specimens of primary human colorectal cancers to establish the role of these genes in colorectal cancer and to evaluate their prognostic importance.

Results:  The expression of Bcl‐2 correlated with early clinical stage and lack of lymphovascular invasion and lymph node involvement. The expression of p53 correlated with less differentiated status and with perineural invasion. p53 expression showed negative correlation with Bcl‐XL expression (P = 0.025) and no correlation with Bcl‐2 expression

Conclusions:  p53 expression may be a less favorable marker and Bcl‐2 expression a more favorable marker of behavior. Bcl‐2 and Bcl‐XL may play an independent role in disease progression, and the expression of these proteins may be under independent regulatory control in colorectal cancer.
New growth factor therapies aimed at improving intestinal adaptation in short bowel syndrome
Authors: Pereira Prue M , Bines Julie E
Published: May 2006

Short bowel syndrome (SBS) is used to describe a condition of malabsorption and malnutrition resulting from the loss of absorptive area following massive small bowel resection. The key to improved clinical outcome after massive small bowel resection is the ability of the residual bowel to adapt. Although still in experimental stages, a major goal in the management of SBS may be the augmented use of growth factors to promote increased adaptation. A number of growth factors have been implicated in promoting the adaptation process. The best‐described growth factors are reviewed: glucagon‐like peptide‐2 (GLP‐2), epidermal growth factor (EGF), and growth hormone (GH). This article reviews the ability of recombinant GLP‐2, EGF and GH to modulate structural and functional aspects of intestinal adaptation following small bowel resection. Although these growth factors have shown promise, small sample size, inconsistent measurement parameters and uncontrolled study designs have hampered the acquisition of strong data advocating the use of growth factor treatment for SBS. Multicenter trials using well‐defined outcome measures to assess clinical efficacy are needed to direct the clinical indications, timing and duration of therapy and assess potential risks associated with growth factor therapies.
Inference on Survival Data with Covariate Measurement Error – An Imputation‐based Approach
Authors: LI YI , RYAN LOUISE
Published: May 2006

Abstract. We propose a new method for fitting proportional hazards models with error‐prone covariates. Regression coefficients are estimated by solving an estimating equation that is the average of the partial likelihood scores based on imputed true covariates. For the purpose of imputation, a linear spline model is assumed on the baseline hazard. We discuss consistency and asymptotic normality of the resulting estimators, and propose a stochastic approximation scheme to obtain the estimates. The algorithm is easy to implement, and reduces to the ordinary Cox partial likelihood approach when the measurement error has a degenerate distribution. Simulations indicate high efficiency and robustness. We consider the special case where error‐prone replicates are available on the unobserved true covariates. As expected, increasing the number of replicates for the unobserved covariates increases efficiency and reduces bias. We illustrate the practical utility of the proposed method with an Eastern Cooperative Oncology Group clinical trial where a genetic marker, c‐mycexpression level, is subject to measurement error.
Semiparametric Global Cross‐ratio Models for Bivariate Censored Data
Authors: GHOSH DEBASHIS
Published: May 2006

Abstract. Multivariate correlated failure time data arise in many medical and scientific settings. In the analysis of such data, it is important to use models where the parameters have simple interpretations. In this paper, we formulate a model for bivariate survival data based on the Plackett distribution. The model is an alternative to the Gamma frailty model proposed by Clayton and Oakes. The parameter in this distribution has a very appealing odds ratio interpretation for dependence between the two failure times; in addition, it allows for negative dependence. We develop novel semiparametric estimation and inference procedures for the model. The asymptotic results of the estimator are developed. The performance of the proposed techniques in finite samples is examined using simulation studies; in addition, the proposed methods are applied to data from an observational study in cancer.
STUDIES IN THE BEHAVIOUR OF THE RHIZOME OF AGROPTRON REPENS(L.) BEAUV.
Authors: PALMER J. H.
Published: May 2006

(1) The mode of growth of the rhizomatous grass Agropyron repens (Couch Grass) is described. The plant produces new rhizomes in the spring from basal lateral buds. The tip of each rhizome grows in a horizontal direction below the soil surface during the spring and summer before erecting in the autumn to form a primary aerial shoot. This shoot develops into a mature plant during the following year.

By sampling a mature stand of Agropyron plants it is shown that the development of the primary shoot is marked by the production of a succession of leaves, internodes and lateral shoots which vary in length or form according to a well‐defined pattern. Usually 7 lateral buds at the base of the primary shoot grow out in the spring to form lateral shoots. Of these, the four most basal ones develop into rhizomes and the remainder into tillers. Plants growing in open communities develop differently in that secondary tillers and rhizomes are formed during the first growing season. Rhizome growth is not related to flower formation.

(2) From experiments it is found that:

(a) Rhizome growth can be induced during the winter under warm greenhouse conditions by increasing the intensity of illumination of the plants to within the range 500–2000 ft. candles.

(b) No rhizome growth occurs under natural conditions when the illumination intensity is reduced to approximately 3 per cent of the noon summer value.

(c) When rhizome growth is induced to begin approximately 4 weeks prematurely, then rhizome growth ceases in Mid‐July.

(3) These results are discussed. It is concluded that rhizome growth is dependent upon the plant being brightly illuminated and that rhizome initiation in the spring is controlled by environmental factors, while rhizome cessation among plants in closed communities is most probably the result of the parent aerial shoots becoming senescent.

The problem of the orientation of the rhizome and its depth adjustment in the soil will be considered in a later paper.

The work described here was carried out in the University of Sheffield, England. The author is indebted to Professor A. R. Clapham for much invaluable advice and criticism. Grateful acknowledgment is made to the Department of Scientific and Industrial Research for a maintenance allowance which made this investigation possible.
THE SODIUM, POTASSIUM AND PHOSPHORUS CONTENTS OF TREE SPECIES GROWN IN CLOSE STANDS
Authors: OVINGTON J. D. , MADGWICK H. A. I.
Published: May 2006

Summary

The percentages of sodium, potassium and phosphorus on a dry weight and ash basis at different positions in the boles and canopies of a number of trees from three experimental areas are given.

The total weights of sodium, potassium and phosphorus in the individual trees and in the tree crop are estimated.

Comparisons are made of the sodium, potassium and phosphorus contents of the various components of the ecosystems in different woodland types.

The balance of nutrients in woodlands is discussed in relation to the need for soil conservation.

We should like to express our gratitude to the Forestry Commission who allowed us to sample the trees in the experimental plots. Unfortunately, it is not possible to include all the primary data that have been collected but they can be obtained on application to the Nature Conservancy or to the authors.
THE BASIDIOMYCETES OF SKOKHOLM ISLAND XIV. STABILITY OF THE MYGOTA
Authors: PARKER‐RHODES A. F.
Published: May 2006

Summary

A method of estimating the stability of fungal populations from suitable field records is described, applicable to the Basidiomycetes. When significant instability is found the method also allows one to estimate the rate of change involved, and over a sufficient period also changes in the rate of change, at least qualitatively. These methods have been applied to data on the Basidiomycetes of Skokholm Island, collected from 1947 to 1956 inclusive.

It was found that the lignicolous species were increasing, but that there was no overall change for practicolous, pteridietal, or coprophilous species. Within the praticolous group, however, two families, Agaricacei and Lycoperdacei, were in decline, while three, Clavariacei, Tricholomatacei and Cortinariacei, were increasing. There was evidence also of a change in composition of the mycota in the lignicolous group and among praticolous Cortinariacei (which were mainly Stropharioidei). The fungi of the Armerietum, a small group, appeared to be rapidly increasing. Temporary fluctuations in numbers, not much less in magnitude than these overall changes, ha'd occurred also in the pteridietal species and in the praticolous Hygrophoracei and Rhodophyllacei. No adequate evidence was found that any of these changes were accelerating or decelerating during the period.

The magnitudes of the rates of change observed, on a per species basis, were mostly less than 1 per cent per annum; but the Clavariacei had increased and the Lycoperdacei decreased at considerably greater rates, but these were both small groups. The general conclusion was that the Skokholm mycota is in a rather stable condition.
ON THE MECHANISM OF SUGAR UPTAKE BY FLOATING LEAF DISKS
Authors: PENNELL G. A. , WEATHERLEY P. E.
Published: May 2006

Summary

Sugar uptake by leaf disks of Atropa belladonna floating on sugar solution was measured as increase in dry weight of the disks.

Evidence of the importance of metabolism in sugar uptake was established as follows:

(a) Uptake was reduced by as much as 75 per cent under anaerobic conditions. Uptake equal to that in air took place with a partial pressure of oxygen as low as 2 per cent. At this oxygen concentration 65 per cent of the full rate of aerobic respiration occurred.

(b) Uptake was considerably reduced by cyanide, azide and 2–4‐di‐nitro‐phenol.

(c) The relationship between rate of uptake and external concentration was not linear, the increment in rate getting progressively less with increasing concentration.

(d) Competition occurred between sugars of similar structure.

(e) Chemical structure of the absorbed sugar played an important part in defining penetrability.

The uptake persisting under anaerobic conditions was designated ‘passive’, and this subtracted from the uptake in air gave the ‘active’ component of the uptake in air.

Chromatographic carbohydrate analyses of the disks revealed that ‘passive’ uptake resulted solely in an increase in sucrose content which reached a constant level within 2 hours. This is interpreted as equilibration of the apparent free space with the external solution.

Under aerobic conditions a higher level of sucrose content was achieved. This is thought to be due to transfer of sucrose into an ‘inner‐space’, possibly the vacuole. In addition synthesis of polysaccharide occurred and it was this continued synthesis which led to persistent sucrose uptake from the medium.

When disks which had been floating on sugar solution were transferred to water, they lost sugar. The quality and quantity of this leakage is consistent's with the hypothesis outlined above.

It is concluded that the processes involved in sugar uptake were (a) diffusion into the outer space, (b) facilitated diffusion into an inner space, (c) synthesis of polysaccharide. There was no evidence of any ‘uphill’ transport being involved.
AESTIVATION IN RANUNCULUS REPENS L.
Authors: CUNNELL G. J.
Published: May 2006

Summary

The aestivation of the calyx and corolla in 640 mature flower buds of Ranunculus repens from two sites near London is recorded.

Only two forms of quincuncial arrangement of the calyx are found and in almost equal numbers. One form is the mirror‐image of the other and they continue the spiral from the prophylls in the left or right direction respectively.

All thirty‐two possible arrangements of the corolla are found in both samples but their frequencies are very unequally distributed. There are more quincuncial and less apotactous and convolute forms than is expected by chance alone.

At the three posterior positions the two possible overlaps are more or less equally frequent overall, but there is a high correlation between the type of calyx and direction of the overlap. The predominating overlap is the eutopic one, i.e. the overlap at each position found in the corolla arrangement which continues the 2/5 spiral from the calyx. Overlaps involving the anterior petal appear to be entirely due to chance although in the site 1 sample there is a significant tendency to metatopy where the anterior and right lateral petals overlap.

These observations are compared with published work on aestivation in other species with variably imbricate pentamerous corollas and their significance is briefly discussed.
POST‐GLACIAL DEPOSITS IN SOUTH YORKSHIRE AND NORTH LINCOLNSHIRE
Authors: SMITH A. G.
Published: May 2006

Summary

The stratigraphy and pollen analysis of Hatfield Moors, Yorkshire, about ten miles south of Goole, are described. These moors are the residue of an old raised bog which lies on the Triassic sandstones and has no underlying deposits indicative of an initial phase of reed‐swamp. The bog, which has at least four flooding horizons, began to grow in early Atlantic times. Early agricultural practices are revealed by the pollen analyses at the opening of Sub‐boreal times, and at the same time small amounts of charcoal are found in the peat. Agricultural activity increased at the beginning of Sub‐atlantic times, but was afterwards curtailed. It is suggested by comparison with a site at South Ferriby in the Ancholme Valley, Lincolnshire, that this curtailment may well date from the end of Romano‐British times.

The stratigraphy and archaeology at Island Carr, Brigg, in the Ancholme Valley are brought together, and a correlation is made between the Bronze Age‐Iron Age transition; the opening of Sub‐atlantic times; and the onset of a marine transgression of the Ancholme Valley. This transgression occurs during a period of relative emergence in the East Anglian Fenland and it is possible that differential isostatic or tectonic movements have taken place between the two areas during the later part of the post‐glacial period. The possibility of the presence of offshore bars, however, complicates the problem. The transgression is also manifested at Redbourne Hayes, a site some five miles to the south of Brigg where the maximum of the transgression is shown, at a rather later date. The peat overlying the transgression clay at Redbourne Hayes probably dates from Romano‐British times and is—perhaps within rather wide limits—contemporaneous with the upper organic deposits at South Ferriby (where Romano‐British remains were found in situ) at Weston Road, Goole, and at Ingoldmells on the Lincolnshire coast.

A reassessment is made of the dating of the site at Ingoldmells in which it appears that the deposits are more comparable with those of the Humber region than with those of the Fenland.
THE RELATION OF LEAF WATER DEFICIT TO SOIL MOISTURE TENSION IN PINUS SYLVESTRIS L.
Authors: RUTTER A. J. , SANDS K.
Published: May 2006

Summary

Diurnal variation in the water balance of 2–3 year Pinus sylvestris in pots has been compared at four levels of soil moisture during 24 hours.

The physical component of the soil moisture suction was measured with tensiometers and gravimetric gypsum blocks and estimated as o.1, 0.5, 1–2 and >5 atmospheres for the four levels. Leaf water deficit was expressed as a percentage of the water at turgidity, transpiration as the loss in fresh weight of a leaf sample during 1–11 minutes after cutting, and stomatal opening was measured by infiltration with alcoholic gentian violet.

Increase in soil moisture tension caused a progressive increase in leaf water deficit, and a decrease in transpiration and stomatal opening, the latter being reduced both in number of open stomata and in the time for which they remained open during the day.

The relative value of these measurements as indices of plant water balance and of soil moisture conditions is discussed together with a brief consideration of the relation between transpiration rate and soil moisture.

It is concluded that leaf water deficit, transpiration and stomatal opening all reflect increase in soil moisture suction but that, during the day, they are affected also by other factors which obscure the direct effect of soil moisture. However, in the case of leaf water deficit an equilibrium is attained between plant and soil before sunrise. If measured in the morning, before the onset of stomatal transpiration, leaf water deficit appears to be closely related to the soil moisture conditions experienced by the plant. This measurement is suggested as the best plant index of the soil moisture suction in the vicinity of the roots.

The persistence of appreciable deficits in wet, drained soil indicates that factors other than the physical soil moisture tension oppose water uptake.
NATURAL HYBRIDIZATION OF AGROSTIS TENUIS SIBTH. AND A. STOLONIFERA L.
Authors: BRADSHAW A. D.
Published: May 2006

Summary

There seems to be little barrier to natural hybridization between Agrostis tennis Sibth. and A. stolonifera L. The F1 hybrid is vigorous: but it is relatively sterile.

The analysis of natural mixed populations of these two species from an old grazing meadow by means of a morphological index and by pollen fertilities shows that over a large central area of the meadow, plants indistinguishable from Fl hybrids are very abundant, to the virtual exclusion of the parental species which would be expected in such a habitat. A more elaborate morphological and cytological analysis confirms this, but suggests that there is also a small percentage of plants belonging to F2 and backcross generations.

The success of the hybrid is due to its growth habit, which is better adapted to grazing conditions than that of either parent. Under grazing conditions reproductive sterility is no disadvantage.

The hybrid populations are made up of a large number of different individual F1 hybrid plants, and cannot be due to the spread of one hybrid plant throughout the meadow, but to the repeated formation of the hybrid. Preliminary examination of other habitats suggests that the hybrid is more common than previously suspected.

Discussion from an ecological standpoint suggests that the success of natural sterile hybrids depends on the possession of strong powers of vegetative propagation originally derived from the parental species. For this reason Agrostis tennis stolonifera is particularly successful. There are, however, other contributory factors.

Discussion from a genetical standpoint suggests that since the hybrid is sterile and subsequent generations are uncommon, the two species are likely to remain quite distinct, but that gene flow between them cannot be ruled out without further investigation.
THE NUCLEOLI AND RELATED STRUCTURES IN THE DESMIDS*
Authors: KING G. C.
Published: May 2006

Summary

The nucleoli of nineteen species from thirteen genera of desmids have been investigated, and in these, four main types of nucleolar structure have been found. The activity of the nucleoli during mitosis and the presence of nucleolar‐organizing chromosomes is described. The presence of a substance resembling Geitler's ‘nucleolar substance’ in Spirogyra is recorded.
THE BALLISTICS OF SORDARIA
Authors: INGOLD C. T. , HADLAND SUSAN A.
Published: May 2006

Summary

The structure of the perithecium of S. fimicola is redescribed. The horizontal distance of spore discharge is studied. Spores may be shot to a distance of up to 10.5 cm. The spore deposit from horizontal discharging perithecia contains spore groups (projectiles) of all possible sizes (i.e. with 1, 2, 3, 4, 5, 6, 7 or 8 spores). The more spores in a group the greater the mean distance of discharge. The existence of the different sizes of projectile in the deposit suggests that the spores tend to stick together, but separation may occur during discharge at any of the seven intervals in the row of eight escaping spores. On the assumption that a break is equally likely at any of these intervals, it is shown that the numbers of projectiles of the different sizes agree closely with expectation. The tendency of spores to stick together is greater at low than at high temperature. The mean distance of horizontal discharge of 8‐spore projectiles is about 20% higher at 21–24°C than at 7–10°C.

Ascus jets discharging vertically have been analyzed by catching them on a rapidly rotating (c. 24 rev. per sec) horizontal disk of transparent ‘Perspex’. The results confirm the view that a break in the row of eight escaping spores can occur at any of the seven possible points of breakage.

The initial velocity of the ascus jet is computed by two independent methods, both giving values of the same general order of magnitude.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: CHARLES H. P. , STREET H. E.
Published: May 2006

Summary

Yeast extract was found to enhance the growth of the excised roots of a Czechoslovakian strain of groundsel. Effects of yeast extract were reproduced by a mixture of L(‐)‐tryptophane and DL‐methionine. β‐indolylacetic acid (IAA) had similar growth‐promoting effects to tryptophane.

When roots were grown in medium containing either tryptophane or IAA for one passage and then subcultured into arginine medium they showed a marked stimulation of growth, particularly of their lateral roots. This growth stimulation, referred to as the ‘indirect’ effect of tryptophane and IAA, was greater than that observed when the roots were subculture into the same tryptophane or IAA medium for their second passage rather than into arginine medium.

1‐naphthoxyacetic acid (1‐NOA) was not directly stimulatory in Passage 1 but caused an ‘indirect’ stimulation of growth in a subsequent passage in arginine medium. 2‐naphthoxyacetic acid (2‐NOA) caused a much greater ‘direct’ enhancement of growth in Passage 1 than tryptophane, methionine or IAA. This strong stimulation was also shown ‘indirectly’ after subculture of the roots into arginine medium.

The hypothesis is advanced that the growth of excised roots from this strain of groundsel is limited by a suboptimal concentration of some natural auxin‐like substance.
ANALYSIS OF THE SPATIAL DISTRIBUTION OF FOLIAGE BY TWO‐DIMENSIONAL POINT QUADRATS
Authors: WILSON J. WARREN
Published: May 2006

Summary

‘Relative frequency’, yielded by point quadrat analysis of vegetation, is a measure of the area of the foliage in vertical projection. Because this projected area varies according to the foliage angle (i.e. the angle between foliage and horizontal), values of relative frequency fluctuate as attitudes change with environmental variation; also, misleading estimates are obtained when comparisons are made between species of different habit. By using horizontal as well as vertical point quadrats it is possible to estimate the foliage angle and the foliage denseness (i.e. total area of foliage per unit volume of space). If the frequencies of contacts with foliage per unit length of point quadrat are F90 and F0 for vertical and horizontal quadrats respectively, foliage angle (α) is given by tan α/2(F0/F90) and foliage denseness (F) by F=F90 sec α.

The vegetation is analysed within horizontal layers. An apparatus is described which can give the required data, and which avoids the errors inherent in point quadrat methods that use needles of appreciable thickness.

The total area of foliage per unit area of ground can be obtained by summation of F for all layers.

Trials show that the method is practicable in the field, and that it gives values of α and F which reflect the character of the vegetation.

Values of F obtained by this method agreed with direct estimates for the same vegetation within 2.5%.

Some assumptions made by the method are discussed; provided that certain precautions are taken, the errors resulting from these are small or none.
THE MIRES OF SOUTH WESTERN WESTMORLAND: STRATIGRAPHY AND POLLEN ANALYSIS
Authors: SMITH A. G.
Published: May 2006

Summary

The stratigraphy is described of three examples of the ‘Estuarine Moor’ of Munn Rankin (1910). The mires lie on a deposit of estuarine clay. The conclusion of Erdtrnan (1928), that the oldest layers date from Atlantic times, is confirmed. It is shown that the marine transgression represented by the estuarine clay came to an end early in zone VIIa of the pollen analytical zone scheme.

The mires began as fens and reedswamps with some open water at first, and later became converted into raised bogs. At two of the sites there was a transition phase of birch fen wood. The transition from fen to bog took place at different times during the Atlantic and Sub‐boreal periods at the three sites. At two sites a boundary horizon in the Sphagnum peat occurs at the opening of Sub‐atlantic times. The relationships between the stratigraphy at the three sites is shown in Fig. 11.

Pollen of Tilia cordata is present in quantity throughout the pollen diagrams, except at the base. The curve for Tilia pollen declines at the opening of zone VIII which has been sub‐divided where the Ulrmus curve declines and the Betula curve begins to rise to a maximum. It is suggested that this maximum of the Betula curve is likely to be due to the colonization by Betula of abandoned fields. At the opening of zone VIIIb, abundant pollen of weeds indicates a period of intense agricultural activity; this period occurs at a time when dryness of the bog surface is indicated by retardation layers at least at two of the sites. Pollen of weeds again becomes abundant as recent times are approached. The indications of early agricultural activity are rather sparse, but pollen of Plantago lanceolata is present at the opening of Sub‐boreal time, and the curves for this pollen tend to increase near the opening of zone VIII.
STRUCTURE AND DISTRIBUTION OF SCLEREIDS IN THE LEAVES OF PALMS
Authors: TOMLINSON P. B.
Published: May 2006

Summary

Foliar sclereids have been found in four genera of palms. They are short, lignified and columnar in Eugeissona, but long, unlignified and fibre‐like in Bactris and Licuala. In Daemonorops hystrix fibre‐like sclereids are present which may be homologous with the fibres sheathing the transverse veins, as is indicated by transitional types found in other species of Daemonorops. The phylogenetic implications of these observations are discussed. Sclereids in palm leaves have no obvious biological function. They are quite useful in diagnosis. Interesting points for comparison between palm leaves and the leaves of the Quiinaceae are reviewed. No development studies have been made, but morphogenetic considerations are discussed briefly.
THE EFFECT OF SOME GROWTH REGULATORS ON THE VASCULAR SYSTEM OF LEMMA MINOR*
Authors: SARGENT JOHN A. , WANGERMANN ELISABETH
Published: May 2006

Summary

When TIBA is added to the culture solution in which fronds of Lernna minor are growing, the vascular system of the fronds becomes more elaborate.

The amount of elaboration increases with concentration up to a maximum, beyond which no further increase is obtained.

TIBA must be present at an early primordial stage to be effective, and sections of pri‐mordia showed that in the presence of TIBA a greater percentage of meristematic cells becomes procambial.

IAA and NAA alone cause only a slight increase in amount of vascular tissue, but added with TIBA they modify the response to TIBA in a way which bears a complex relationship to their concentration.

Pre‐treatment of the fronds with IAA does not alter their response to the mixtures of IAA and TIBA.

It is concluded that TIBA is not acting as an anti‐auxin, but that an unknown inhibitor of vascular tissue may be present in the fronds which is counteracted by TIBA.

Other halogenated benzoic acids have similar effects.

It was reported in a previous paper (Wangermann and Lacey, 1953) that the vascular system of fronds of L. minor, which is normally very simple, becomes much more elaborate when 2,3,5‐tri‐iodobenzoic acid (TIBA) is added to the culture solution, and that this effect of TIBA is modified by simultaneous addition of indole‐acetic acid (IAA). These effects have been investigated further in an attempt to gain some insight into the way in which the normal pattern is determined.
DEVELOPMENT OF THE INFLORESCENCE AND SPIKELETS OF ANTHOXANTHUM ODORATUM L.
Authors: SHARMAN B. C.
Published: May 2006

Summary

The sequence of events in the development of the inflorescence and spikelets of Anthoxanthum odoratum is described and illustrated.

The shoot‐apex becomes longer and bears more leaf primordia during spring, becoming extremely elongated just prior to inflorescence initiation.

Primary panicle buds are borne in two rows in the axils of alternate small collar‐like leaf primordia.

These buds bear rudimentary leaf primordia in whose axils secondary buds are initiated. Similar repeated branching leads to the development of the panicle type of inflorescence.

Spikelet differentiation begins at the tip of the inflorescence and later occurs at the ends of the individual panicle branches.

The two glumes and the four lemmas arise in an orderly alternate sequence, followed by the two stamen primordia.

The stamen primordia appear to be axial in nature and are not leaf primordia.

The two stamens are probably the axillary buds of the last two lemmas.

The carpel arises on the side of the spikelet apex in the plane of the lemmas and glumes, continuing their strictly alternate sequence.

In origin the carpel appears to be homologous with a single leaf.

The two stigmas arise one on each side of the carpel as the latter encloses the spikelet tip.

In the terminal spikelet the carpel appears to be the last leaf on the whole shoot and is in strict distichous continuity with (a) the lemmas and glumes of that spikelet, (b) the collar‐like rudimentary leaf primordia subtending the primary spikelet‐branches below, and (c) the vegetative leaves at the base.
POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: CRANE MOOR, HAMPSHIRE
Authors: SEAGRIEF S. C.
Published: May 2006

Summary

Pollen analyses have been made from three parts of a New Forest valley bog system, Hampshire, England. The wide valleys excavated in the preceding Full‐glacial or Late‐glacial time were shown to be filled by organic deposits accumulated rapidly during the Pre‐boreal and Boreal periods. Pinus is shown to have been strongly dominant throughout this time, and the sub‐zones a, b and c of pollen zone VI are clearly and characteristically displayed. The beech (Fagus sylvatica) is shown to have been present already in the Boreal period. These results conform with those already reported from southern England. Although at the site there is evidence of the persistence of open habitat plants of the Late‐glacial into the early Post‐glacial, thereafter the record is one of closed woodland. Deposits later than early zone VII (Atlantic) are not present.
POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: ELSTEAD, SURREY
Authors: SEAGRIEF S. C. , GODWIN H.
Published: May 2006

Summary

A small peat bog at Elstead, Surrey, has been investigated stratigraphically, by pollen analysis and by identification of macroscopic plant remains. The organic infilling was largely completed in zones IV, V and VI of the Post‐glacial period. At the close of zone III and in zone IV both pollen and macroscopic remains testify to a varied and open vegetation containing many typical Late‐glacial plants. Zone III was dominated by birch and zones IV, V and VI by pine. The sub‐zones a, b and c of zone VI are recognizable and the general picture of forest history conforms to that of other sites in the south of England, permitting a date to be placed upon the main stages of infilling of the lake‐basin, notably a phase of deposition of mineral material in sub‐zone Vic, and a possible hiatus immediately afterwards.
NEW OR RARE BRITISH GHRYSOPHYCEAE
Authors: LUND J. W. G.
Published: May 2006

Summary

Pseudokephyrion klarnetii, P. pseudospirale, P. ovum, P. ellipsoideum and an unnamed species figured by Williams (1933) are recorded and described. The records of sexuality in such algae are reviewed and the similarity between this and asexual budding considered. The taxonomic histories of Kephyrion, Pseudokephyrion, Kephyriopsis and Stenocalyx are summarized. A consideration of the characters utilized by various authors leads to the conclusion that until these algae are better known their generic limits must be uncertain. Specific limits can be clearer, particularly if sexually reproducing populations are found.
THE GENUS TAENIOMA IN WEST AFRICA
Authors: LAWSON G. W.
Published: May 2006

Summary

The existence of two species in the genus Taenioma is confirmed from West African material. T. nanum occurs in Sierra Leone and T. perpusillum in Ghana. In West African material of T. nanum the determinate branches invariably end in two hairs. In T. perpusillum, though the majority of determinate branches end in three hairs, two‐haired branches are quite common. They are usually, however, morphologically quite distinct from the two‐haired branches of T. nanum.
NITROGEN METABOLISM IN THE‘ROOT’OF BRASSICA NAPUS L.
Authors: BOSWELL J. G.
Published: May 2006

Summary

The recorded observations are interpreted on the basis that part at least of the protein in the tissue is maintained by a metabolic system in which synthesis and breakdown of protein occur simultaneously, and that these two processes are not two phases of a reversible system but are composed of two separate groups of reactions. The data obtained indicate that protein breakdown is controlled by an iron‐containing enzyme system which may well involve cytochrome and that this is associated with the Krebs cycle of organic‐acid metabolism. The synthesis of protein appears to be controlled by a copper‐containing enzyme system which in the swede ‘root’ may well involve ascorbic acid. C4 and C6 organic acids are utilized in the process of protein synthesis.
THE CASE FOR EXTENSIVE RATHER THAN INTENSIVE SAMPLING IN GENECOLOGY
Authors: HARBERD D. J.
Published: May 2006

Summary

This paper is primarily concerned with the technique of genecological investigation.

The data refers to thirteen taxa sampled at the rate of up to five individuals per site, and in up to eighty sites, all within the Agrostis‐Festuca grassland community. Most of the fifty‐four species‐characters recorded are significantly different between populations using the within‐population variance as error, but on further investigation little of this is found to have genecological significance: it is believed to be due to genotype reduplication in sampling.

Basing analyses on population means and either employing the analysis of variance of grouped data or correlation with a habitat factor, few of the characters reach significance and for the most part these characters seem to be indubitable examples of genecological differentiation. The genecological conclusions were that within the local Agrostis‐Festuca grassland the more leached sites carry the earlier populations of Cerastium vulgatum and Poa trivialis and the longer‐leaved or taller vegetative plants of Carex caryophyllea and Poa trivialis. There was some evidence in Galium spp. that apparently genecological differentiation could result from introgression.

Interspecific correlation of genetical characters was investigated but no significance interpretable genecologically was found in this study. It seems likely that the species showing differentiation in the flushed to leached series of sites are differentiated in relation to different underlying environmental factors.

The place of extensive methods in genecology is discussed and possible developments indicated.