bluuebunny/crossref_metadata_2025 huggingface dataset:
A SECTORIAL ENTIRE‐PINNATE LEAF CHIMERA IN THE POTATO VARIETY MAJESTIC
Authors: HOWARD H. W.
Published: May 2006

Summary

The docken‐ (entire‐) leaf sport in the potato variety Majestic is a periclinal chimera in which L2 and L3 have a mutation for entire leaf but in which L1 has the unchanged genotype for normal pinnate leaves. A shoot was found after X‐ray treatment which had pinnate, entire and sectorial leaves. The arrangement of leaves on this shoot would fit a hypothesis postulating only two initial cells for L2. The L2 of leaf primordia may trace back to only two cells at a time when the L2 has about sixteen or thirty‐two cells as seen in transverse section.
THE OCCURRENCE OF LIVING AND SUB‐FOSSIL REMAINS OF BETULA NANA L. IN UPPER TEESDALE
Authors: HUTCHINSON T. C.
Published: May 2006

Summary

A small colony of the arctic‐alpine dwarf birch, Betula nana, has been discovered in Upper Teesdale, this being the only English station for the species. It is elsewhere in Britain confined to the Scottish Highlands. The plant associations with which the species occurs throughout its range are of two types, tundra vegetation in the north, and sub‐alpine dwarf shrub vegetation in the south of its range. In Teesdale the species is confined to the sub‐alpine dwarf shrub type although an open tundra type is also present. Sub‐fossil leaf remains of B. nana have been found in Teesdale close to the living colony, in a fen peat. The leaf remains are associated with deposits later than the commencement of Zone Vila, thus indicating that the species has probably been continuously present in Teesdale since Atlantic times. The Late‐glacial finding of the species in Lower Teesdale suggests that the present colony may have a continuity in Upper Teesdale from Late‐glacial times to the present day (approximately 12,000 years).
SOME EFFECTS OF ADENINE ON GROWTH, RESPIRATION, ADENOSINE DIPHOSPHATE AND TRIPHOSPHATE CONCENTRATIONS IN PLANT TISSUES
Authors: MERRETT M. J. , HANDOLL C.
Published: May 2006

Summary

Conditioned callus tissues of Nicotiana tabacum type White Burley variety Judy's Pride were grown on basal media supplemented with purine or pyrimidine bases. A substantial increase in ATP concentration in the tissues occurred only with adenine. The accumulation of ATP was not the result of growth inhibition and the ATP concentration of the tissues was increased by adenine concentrations which did not inhibit growth. When exogenous adenine was added to tissues grown on basal media, the respiration rate was not increased. The respiration rate of tissues grown on adenine‐containing media was the same as that of tissues grown on basal media. Although adenine increased the total amount of ATP in the tissue, the ADP concentration was unatfected. Dinitrophenol stimulated the respiration rate and this, taken together with the unaltered ADP concentration, suggests that the availability of phosphate acceptors still controls the respiration rate of tissues grown with adenine in the medium. The response of tobacco callus tissue to adenine infected with tobacco mosaic virus was similar to that of non‐infected tissue.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J. , KHAN M. A. A. , SOLOMOS T.
Published: May 2006

Summary

The changes of glucose‐6‐phosphate, fructose‐6‐phosphate, fructose diphosphate, dihydroxy‐acetonephosphate, 3‐phosphoglycerate, 2‐phosphoglycerate, phosphoenolpyruvate, adenosine triphosphate, adenosine diphosphate, adenosine 5′‐monophosphate and oxidized co‐enzyme I were determined in shelled green peas held in air and in nitrogen. In anoxia 3‐phosphoglycerate, 2‐phosphoglycerate, phosphoenolpyruvate, adenosine triphosphate and oxidized co‐enzyme I, each decreased markedly to new steady levels after ahout 15 minutes; except in one experiment, adenosine diphosphate increased markedly for about 15 minutes. Similarly, the development of the Pasteur effect in shelled green peas is rapid, i.e. less than 30 minutes (Wager, 1961). In contrast, glucose‐6‐phosphate decreased for some 24 hours of anoxia, while fructose diphosphate and dihydroxyacetonephosphate first increased, then decreased and finally might rise again.

From our results, the metabolic fate of adenosine diphosphate appears to be of primary importance in controlling the rate of glycolysis. Thus, with transfer to anoxia, the most consistent ehange in the glycolytic intermediates is the rapid decrease in the contents of 3‐phosphoglycerate and of phosphoenolpyruvate. One explanation of these changes is that the pyruvate kinase reaction is accelerated, due possibly to a local increase of adenosine diphosphate. With a faster pyruvate kinase reaction, the additional adenosine triphosphate formed might hasten glycolysis and this faster rate might then be maintained.

The fact that, in anoxia, smaller amounts of adenosine triphosphate support a higher rate of glycolysis than in air has suggested that in air this nucleotide is not readily available to the sugar‐phosphorylating enzymes. Similarly, the present results could be explained if the glycolytic enzymes were mainly confined to an organized structure showing a difference in accessibility for adenosine di‐ and triphosphates.

On the other hand, our results may be related to a feed‐back mechanism not yet specified. How important such mechanisms might be is shown by the complex effeets of adenosine nucleotides, of inorganic phosphate and of other compounds on the activity of phospho‐fruetokinase in vitro.

The changes m anoxia, stated above, of glueose‐6‐phospliate, of fructose diphosphate and of dihydroxyacetone phosphate are considered.

A difference in the metabolic fate of adenosine triphosphate in aerobie and anaerobie conditions is described. The difference is readily explained in terms of a glyeolytic structure but could also be due to an acceleration of the hexokinase and phosphofructokinase reaetions in anaerohiosis either by activation or by a decrease in the inhibition of these enzymic stages.

While the existence of a glycolytic structure has not been proved beyond doubt, evidence that such a strueture may exist is accumulating.
NATURAL SELECTION IN AN ARTIFICIAL POPULATION OF SORDARIA FIMICOLA
Authors: COX B. S. , PARRY ELIZABETH M.
Published: May 2006

Summary

A strain of Sordaria fimicola carries a reciprocal translocation which results in the formation of aborted ascospores in perithecia hybrid between this and the normal strain. Petri‐dish populations of the two strains were propagated by ascospore samples and the frequency of hybrid perithecia formed in each generation was followed. It was found that there was a rapid decrease in their frequency over eight generations. This was accounted for by the progressive elimination of normal nuclei by natural selection. Reasons for this selection are discussed.
A CHROMOSOMAL TRANSLOCATION IN SORDARIA FIMICOLA AND IRREGULAR SEGREGATION OF CHROMOSOMES
Authors: COX B. S. , GILL J. J. B.
Published: May 2006

Summary

A strain of Sordaria fimicola has been isolated which has normal black spores with 98% viability, but which, when crossed with wild‐type Sordaria, gives rise to aborted spores in the majority of asci in hybrid perithecia. The pattern of spore abortion is consistent with the hypothesis that the abnormal strain contains a reciprocal translocation and this is supported by the cytological data and also by tetrad analysis data. Consideration of a few exceptions in the tetrad analysis and in the chromosome preparations suggests that irregular segregation following a failure of pairing may sometimes occur at meiosis.
CO2 FIXATION, ORGANIC ACIDS AND SOME ENZYMES IN GREEN AND COLOURLESS TISSUE CULTURES OE KALANCHOË CRENATA
Authors: MCLAREN L , THOMAS D. R.
Published: May 2006

Summary

Measurements of gaseous exchange between green callus tissue cultures of Kalanchoe crenata and air showed that photosynthesis occurred in the green callus. Feeding experiments with 14CO2 showed that 14C was incorporated by green callus into sugars and sugar phosphates in the light, and some 14C was incorporated into organic acids. Organic acids were the main products of dark fixation of 14CO2 by green callus but no activity was detected in sugars or sugar phosphates. The products of 14CO2 fixation in colourless callus were primarily organic acids both in the light and dark and no activity was detected in sugars or sugar phosphates.

Green callus did not show a diurnal fluctuation of acid content. This, coupled with the observations that green callus did not show a net fixation of CO2 in the dark, suggested that the green callus did not exhibit crassulacean acid metabolism. Green callus, however, contained greater quantities of malate, citrate and isocitrate than did colourless callus. Enzyme assays suggested that the presence of PEP carboxylase in green callus and its absence in colourless callus might in part contribute to the higher acid levels of green callus.
EVOLUTION OF THE ENDOSPERM IN PROTEACEAE
Authors: RAO C. VENKATA
Published: May 2006

Summary

The endosperm development in several genera of both sub‐families of Protcaceae is studied. The scanty nuclear endosperm and large persistent nucellus (perisperm) seem to represent the most primitive conditions. The general absence of endosperm haustoria in Proteoideae and their universal occurrence in Grevilleoideae are attributed to the different methods of the post‐fertilization growth of their ovules. The probable factors which led to the origin of the endosperm haustorium in Grevilleoideae are suggested and the trends in its evolution are outlined.
TAXONOMY AND TAXIMETRICS OF STELLARIA MEDIA (L.) VILL., S. NEGLECTA WEIHE AND S. PALLIDA (DUMORT.) PIRÉ
Authors: WHITEHEAD F. H. , SINHA R. P.
Published: May 2006

Summary

Three species of Stellaria (S. media, S. neglecta and S. pallida) have different ecological amplitudes, S. media is ubiquitous and S. pallida and S. neglecta have well‐defined and circumscribed ecological niches. They also differ in phenological behaviour and Cytology. In morphological attributes, the differences are less marked so tbat they have always presented difficulties in identification.

The present paper is concerned with the morphometrical aspect of an integrated approach to the taxonomy of the Stellaria media complex. Twelve variables were used and data were collected from the floral parts of 253 British herbarium specimens. The data were employed in both canonical variate and principal component analyses utilizing a computer. The three species were shown by these methods to be quite distinct. Morphometrically, S. pallida was found to be clearly separable from the other two species. These latter, although separable, were found to have intergrading morphometric features. The characters seed length, seed weight, length of tubercles and pollen diameter were shown to be the most significant in discrimination and, therefore, suitable for the construction of a key to separate the three species.

The advantages of canonical variate and principal component analyses in the future development of taxonomy are discussed.
THE USE OF SCANNING ELECTRON MICROSCOPY IN THE STUDY OF CARBONIFEROUS MIOSPORES
Authors: HIBBERT F. A.
Published: May 2006

Summary

Techniques for the study of fossil spores using the scanning electron microscope are outlined. The structure of Tetrapterites visensis is discussed from micrographs obtained with the Cambridge ‘Stereoscan’ electron microscope.
THE APICAL MERISTEM OF FUCUS
Authors: MOSS BETTY
Published: May 2006

Summary

Studies on young vegetative apices of Fucus show that after the large apical cell is differentiated it becomes surrounded by an extensive meristematic zone, the pro‐meristem. It is suggested that this is the main zone of cell division at the apex and that the apical cell itself rarely segments. But the apical cell is the main seat of control, for without it the apex shows no further growth. The size of the apical cell and of the pro‐meristem increases during growth of the vegetative branch. A new apical cell becomes associated with a portion of the pro‐meristem when forking of a branch occurs. Morphologically there is sudden change from vegetative to reproductive growth at an apex. Apical initials and a pro‐meristem function in a receptacle until all concept‐acles are laid down. Following conceptacle development there is a loss of meristematic activity at the apex, and after gamete discharge the tissues gradually disintegrate.
ANATOMY OF THE STIGMA AND STYLE OF SWEET POTATO
Authors: MARTIN F. W. , ORTIZ SONIA
Published: May 2006

Summary

The stigma and style are the sites where self‐incompatibility and hybrid sterility reactions occur in the sweet potato. The stigma is a highly branched structure covered with a specialized papillate epidermis which exudes a sticky fluid. The cells of the body of the stigma are arranged in gradually narrowing columns which conduct the pollen tubes from stigma to style. The style contains a central, uniform core of pollen‐tube conducting tissue. The junction of style and ovary provides a continuous but contorted pathway of conducting tissue which pollen tubes follow. The incompatibility reaction, which occurs at the stigmatic surface, is hypothesized to be due to interactions of substances in the pollen and in the stigmatic exudate. Sterility, on the other hand, may be due to pollen tube disorientation or failure at the stigma‐style junction and the style‐ovary junction, where passage may be mechanically more difficult.
THE DEVELOPMENT OF ORCHIS PURPURELLA IN ASYMBIOTIC AND INOCULATED CULTURES
Authors: HARVAIS G. , HADLEY G.
Published: May 2006

Summary

In asymbiotic cultures Orchis (Dactylorchis) purpurella seed germinated freely on deionized water agar and on defined and undefined media. Germination was enhanced by prolonged sterilization periods and high temperatures but was inhibited by light. Asymbiotic protocorms never attained the photosynthetic stage except on undefined media.

Several Rhizoctonia solani strains enhanced seed germination at low temperatures. The further development of the relationship between host and endophyte varied with the strain; two pathogenic isolates from tomato and rice were strongly symbiotic to protocorms while other strains although stimulating growth ultimately became parasitic.

Symbiosis was most stable at low temperatures but with any one strain there was a general pattern of infection in which nutrient depletion in the protocorm was often followed by parasitism. Drip feeding with carbohydrate delayed parasitism but in some conditions led to intense growth of the fungus. It is suggested that a careful balance of nutrients is important in the maintenance of a stable relationship between host and endophyte. The significance of this is discussed in relation to conditions in nature.
THE SIGNIFICANCE OF MYCORRHIZAL NODULES OF AGATHIS AUSTRALIS
Authors: MORRISON T. M. , ENGLISH D. A.
Published: May 2006

Summary

Experiments using excised nodules of kauri showed that vesicular‐arbuscular mycorrhizal infection markedly stimulated phosphate absorption by these organs. Small but significant fixation of nitrogen was also noted in excised nodules, whether mycorrhizal or not.
SURGICAL INVESTIGATION OF THE ROLE OF IAA AND GA IN THE ELONGATION OF‘METEOR’PEA INTERNODES
Authors: ARNEY S. E. , MANCINELLI P. A.
Published: May 2006

Summary

The elongation of the second internode of Meteor pea seedlings and the relationship of this elongation to cell division and cell elongation in the epidermis and cortex has been determined after treatment with either IAA or GA or both together, and in combination with decapitation, and removal of the first or second leaves either separately or together. The cells from the side of the internode subtending the second leaf are consistently longer than on the other side, and this effect is intensified by application of GA and abolished by application of IAA. Decapitation and defoliation together abolish the usual stimulation of cell elongation by GA. It is concluded that the results are in harmony with the hypothesis that the cell elongating effect of GA is the result of an increased production of auxin in the apical regions and young leaves.
THE MECHANISM OF SPORANGIAL DISCHARGE IN PYTHIUM MIDDLETONII
Authors: WEBSTER J. , DENNIS C.
Published: May 2006

Summary

Methods are described for inducing zoospore formation in Pythium middletonii. Stages in the discharge of the sporangial contents into the vesicle have been followed by means of a sequence of photomicrographs. The mechanism of sporangial emptying is discussed. Photomicrographs at various stages of zoosporangial discharge have been measured to give estimates of sporangial and vesicle volumes. Shrinkage in sporangial volume by about 46% and increase in cytoplasmic volume of about 58% presumably caused by water uptake, occur during discharge. During movement of cytoplasm from the sporangium into the vesicle the residual cytoplasm assumes a spherical shape, and it is suggested that surface energy is responsible for the emptying of the sporangium. This hypothesis is supported by photomicrographic evidence showing that separation of the cytoplasm from the sporangium wall does not occur until the vesicle diameter is almost equal to that of the shrunken sporangium. It is further postulated that the liquid surrounding the cytoplasm in the vesicle must exert a higher surface tension than water. The difficulties of alternative hypotheses are discussed.
POLYPHENOL OXIDASE ACTIVITY AND THE METABOLISM OF GLYCINE BY POTATO TUBER SLICES
Authors: ABUKHARMA D. A. , WOOLHOUSE H. W.
Published: May 2006

Summary

Glycine and catechol when added separately to both fresh and washed potato‐tuber slices stimulated their oxygen uptake and CO2 production. Glycine and catechol added together produced an additive stimulation of the respiration of fresh tuber‐slices but gave no stimulation of respiration by washed slices. The inhibitory effect of 3,4‐dichlorophenyl serine on the oxidation of glycine by unwashed slices suggests that this step in the degradation was probably mediated by polyphenol oxidase.
ELECTRICAL POTENTIAL MEASUREMENTS, ION PUMPS AND ROOT EXUDATION—A COMMENT AND A MODEL EXPLAINING CATION SELECTIVITY BY THE ROOT
Authors: JENNINGS D. H.
Published: May 2006

Summary

The value of measurements of the electrical potential difference between the external solution and the xylem sap for determining the presence or absence of an active ion flux in a root is discussed. It can be shown that the presence of an ion pump within the cells of the root is by no means incompatible with electrochemical equilibrium between the exuding sap and the external solution. A model is proposed for an exuding root of which the important features are a sodium pump at the tonoplast and the absence of any role for the endodermis. This model is shown to explain many experimental facts of which detailed consideration is given to the selective effect of the root on the cation composition of the exudate and the effect of an induced water flow through the root in reducing this selectivity.
CARBOHYDRATE TRANSLOCATION IN ORCHID MYCORRHIZAS
Authors: SMITH SARAH E.
Published: May 2006

Summary

The soluble sugars of uninfected regions of Dactylorchis purpurella were found to be glucose, fructose and sucrose. Mycelium of three mycorrhizal fungi, isolated from this orchid, was found to contain glucose and trehalose. Two of the fungi also contained mannitol. Mycorrhizal seedlings of D. purpurella contained carbohydrates contributed by both orchid and fungal partners.

The incorporation of 14C into mycorrhizal seedlings was followed, after [14C]glucose had been supplied to infective hyphae some distance from the seedlings. 14C incorporation into soluble and insoluble materials continued throughout the 7‐day experimental period. The results were consistent with the hypothesis that a carbohydrate, possibly trehalose, is translocated by the fungal hyphae into the seedlings. The fungal sugar, trehalose, was the first to become labelled, and the proportion of label in this sugar declined as 14C was incorporated into other carbohydrates, notably sucrose. As sucrose was not found in fungal mycelium, movement of a 14C‐labelled compound from internal fungal hyphae to orchid cells must have taken place.
ONTOGENY AND CYTOCHEMISTRY OF THE CHALAZAL PROLIFERATING CELLS OF CAPSELLA BURSA‐PASTORIS (L.) MEDIC.
Authors: POLLOCK E. G. , JENSEN W. A.
Published: May 2006

Summary

This paper describes the ontogenic development and cytochemistry of a group of cells which proliferate from the chalaza of the ovule of Capsella bursa‐pastoris. These cells arise from nucellar tissue in the chalaza at the time of embryo development and develop a consistent morphology which seems to protrude into the embryo sac. Azure B staining and intensity of incorporation of nucleic acid precursors indicates a high rate of activity of these cells up to the time that the embryo is in the heart stage. They then begin to disintegrate quickly with but a few cells remaining in the mature seed. The evidence suggests that they may play a physiological role in early embryo development.
MOVEMENT OF GROWTH REGULATORS IN PLANTS
Authors: McCREADY C. C. , JACOBS W. P.
Published: May 2006

Summary

This paper describes the effects on auxin transport of treatments which changed the rate of elongation of the transporting tissues. The inclusion of mannitol in blocks of agar gel applied to each end of segments cut from petioles of Phaseolus vulgaris L. reduced elongation of the segments. This treatment also increased basipetal movement of 2,4‐dichlorophenoxyacetic acid (2,4‐D) from donor blocks through the segments into receiver blocks and decreased net acropetal movement, so that the polarity of 2,4‐D transport was raised, Gibberellic acid applied in the donor blocks promoted elongation but decreased the basipetal movement of 2,4‐D and increased its net acropetal movement, so that the polarity of 2,4‐D transport was lowered. It is concluded that polar transport of this auxin is not dependent on elongation of the transporting tissues.
A METHOD OF ABSOLUTE POLLEN COUNTING
Authors: JØRGENSEN SVEND
Published: May 2006

Summary

Determination of absolute pollen frequency in recent and fossil material is carried out by counting all pollen (and spores) in weigbed aliquots of tbe samples.
PHOTOSYNTHESIS AND RESPIRATION IN RELATION TO LEAF AGE IN PERILLA FRUTESCENS (L.) BRITT
Authors: HARDWICK K. , WOOD M. , WOOLHOUSE H. W.
Published: May 2006

Summary

The rate of photosynthesis in the third pair of leaves of Perilla frutescens declined gradually from the time of completion of expansion of the leaves until approximately I week from abscission when there was a more rapid decrease. The decrease in rate of photosynthesis first became apparent in the parts of the lamina proximal to the petiole and gradually extended to the more distal regions. The rate of respiration of the leaf remained approximately constant until I week from abscission when there was a transient rise prior to the final decrease in rate, The gradual decline in photosynthesis was accompanied by a similar decline in the RNA and protein content of the leaf although the chlorophyll content did not change during this period. Measurements of photosynthesis by means of 14CO2 incorporation showed a similar pattern of change and further revealed that the rate of incorporation of label into protein declined more rapidly than did the total protein content, The data are interpreted as suggesting the cessation of synthesis of proteins essential for photosynthesis rather than an increased rate of proteolysis as the cause of the senescence changes.
STUDIES OF THE POST‐GLACIAL HISTORY OF BRITISH VEGETATION
Authors: GODWIN H.
Published: May 2006

Summary

Two boreholes in the organic deposits of Old Buckenham Mere, Norfolk show that accumulation began in the Late‐Glacial period. The rich pollen flora from two boreholes shows great similarities with that of three other Late‐Glacial sites in the region, and differs from that of the Late‐Weichselian at Colney Heath mainly in the prevalence of tree birches. Above a depositional hiatus shown to correspond with most of pollen Zones V, VI and Vila, borehole 2 has 7 m of uniform organic muds to which a conjectural timescale has been applied. Thus the detailed pollen diagrams can be correlated with pre‐historic and historic events from early Neolithic to the present day. For this period the diagrams yield evidence of the changing kind and intensity of forest exploitation and destruction, and particularly the great extension of arable cultivation in Anglo‐Saxon times. The re‐expansion of many Late‐Glacial plants as weeds and ruderals is evident and analysis of the changing frequencies of trees and shrubs accords with explanations in terms of anthropogenic rather than climatic effects. There is now remarkable continuity of evidence of the character of East Anglican vegetation from Full‐Weichselian time to the present day.
A LARGE CAPACITY HAND‐OPERATED PEATO SAMPLER
Authors: SMITH A. G. , PILCHER J. R. , SINGH G.
Published: May 2006

Summary

A sampler is described that will take 12 cm cores, 1.5 m long, from peat and compacted organic lake sediments. The sampler tube has a longitudinal slit to obviate compression and is provided with a plastic liner. The sampler is driven by lever chain‐hoists. For insertion, the hoists are attached to basal members of a scaffold‐pole rig secured to the deposit by long pins.
THE INFLUENCE OF DIURNAL TEMPERATURE FLUCTUATIONS ON THE GROWTH OF FUNGI
Authors: BURGESS L. W. , GRIFFIN D. M.
Published: May 2006

Summary

A theoretical relationship is developed relating growth of a fungus during one cycle of a diurnal temperature fluctuation to the growth at relevant constant temperatures. The theory involves the assumption that the growth‐rate of the fungus at a given temperature in the cycle is unaffected by its previous temperature experience. Growth of Gibberelta zeae, Cochliobolus sativus and C. spicifer was measured at each of sixteen diurnal temperature regimes differing in median temperature and amplitude. The measured growth was compared with the expected growth. In general, the analysis supports the derived theoretical relationship. In some instances, growth at a fluctuating temperature is greater than or less than that at the corresponding median and the difference is anticipated, and explained, by the theory.
THE NUTRITIONAL REQUIREMENTS OF EXCISED ROOTS OF THREE GENOTYPES OF ARABIDOPSIS THALIANA (L) HEYNH.
Authors: NEALES T. F.
Published: May 2006

Summary

Methods are described for the culture of excised roots of Arabidopsis thaliana. Cultures of the roots of three genotypes (EST, PI and 1018/6) were established. The genotypes PI and 1018/6 each differ from the wild‐type, EST, by a single gene mutation. It is shown that there are differences between the excised roots of the three genotypes in growth rate and in the requirement for the vitamins, thiamin and biotin. The vitamin requirements of the excised roots largely reflect those of intact plants, as established by Langridge. However, roots of the genotype PI responded to thiamin and biotin, whilst whole plants of this strain respond only to biotin.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J. , KHAN M. A. A.
Published: May 2006

Summary

In eleven experiments with apples and potatoes phosphoenolpyruvate decreased during anoxia in nine experiments. The data were thus, in general, in accord with the ‘localization’ theory of the Pasteur effect.

Of the eleven experiments, only two showed the decrease in glucose‐6‐phosphate and increase in fructose diphosphate in anoxia which are accepted as evidence that the ‘activation/inactivation’ theory is operating. The data were thus, in general, not in accord with the ‘activation/inactivation’ theory of the Pasteur effect.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J.
Published: May 2006

Summary

The contents of glucosc‐6‐phosphate, fructose diphosphate, 3‐phosphoglycerate and phos‐phoenolpyruvate were substantially unchanged during the ‘climacteric’ rise in CO2 output in apples. The mechanism of the ‘climacteric’ increase in respiration in apples thus appears to differ from that in bananas.
THE ONSET OF PHOTOPHOSPHORYLATION IN CHLOROPLASTS ISOLATED FROM DEVELOPING BEAN LEAVES
Authors: GYLDENHOLM A. O. , WHATLEY F. R.
Published: May 2006

Summary

Photophosphorylation has been achieved in isolated chloroplasts of Phaseolus, without inhibition, by the addition of bovine serum albumin. Cyclic and non‐cyclic photophosphorylation and four partial reactions of photosynthetic phosphorylation were studied in the system with chloroplasts of different ages. There seems to be evidence for a correlation between a minimum structural complexity of the chloroplast and the ability to carry out the reactions studied.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J.
Published: May 2006

Summary

Transferring potatoes, peas and strawberry leaves from 10 to 1° C produced initial increases in the contents of glucose‐6‐phosphate and fructose‐6‐phosphate and, in some experiments, the amounts of fructose diphosphate and of dihydroxyacetonephosphate. In contrast the contents of 3‐phosphoglycerate and of phosphoenolpyruvate decreased at 1° C. The above changes in phosphate esters appeared not to affect the rate of respiration.
CHANGES IN THE ENZYME ACTIVITY OF SOLUBLE PROTEIN FRACTIONS IN THE COURSE OF FOLIAR SENESCENCE IN PERILLA FRUTESCENS (L.) BRITT.
Authors: KANNANGARA C. G. , WOOLHOUSE H. W.
Published: May 2006

Summary

Separation of the soluble proteins from leaves of Perilla by means of gel filtration on a Sephadex Groo column yielded two protein bands with molecular weights of approximately 400,000 and 23,000, which appear to correspond to the well‐known Fraction I and Fraction II proteins respectively. The amount of Fraction I protein in the leaves decreased progressively from the time that the leaves became fully expanded whilst the amount of Fraction II protein decreased only in the later stages of senescence. Aleasurements of the activity of several enzymes in successive 4 ml fractions from the column showed that each occupied a different peak position within the two main protein fractions. Fach of the enzymes assayed showed a different pattern of change in the course of senescence of the leaves. These changes in protein content and enzyme activity are discussed in relation to earlier observations on the physiological functioning of senescing leaves of Perilla.
STUDIES ON THE α‐l‐ARABINOFURANOSIDASE OF PHYTOPHTHORA PALMIVORA (BUTL.) BUTL.
Authors: AKINREFON O. A.
Published: May 2006

Summary

The properties of the extra‐cellular enzyme, α‐l‐arabinofuranosidase, produced by Phytophthora palrmivora was studied in some detail. The optimum pH for the enzyme activity was 4.0, a level which is typical of the host plant tissues. Activity was stable over a considerable range of pH (2.0–8.0) depending on the length of time of e.Kposure to this condition. The optimum temperature was 50° C, higher than that recorded for its production. The activity was thermostable between 10 and 50° C; thermal inactivation was recorded at 70° C. The data from the Q10 values indicated that thermal inactivation beyond 60° C might be due to the denaturation of the enzyme protein.

The molecular weight determination indicated that the enzyme existed in two major molecular units of 63, 100 and 15, 850, respectively.

The enzyme activity was proportional to the log enzyme concentration. The enzyme was highly specific for its substrate; the average Km value was 0.65 mM. The activity was inhibited by arabinogalactan competitively, the Ki value being 5.83 mM. The activity was enhanced by the presence of calcium arabonate tetrahydrate. The activation was due to Ca2+. Plant metabolic analogues affected enzyme activity; L‐arabinose was the most inhibitory sugar, and L‐glutamine the most inhibitory amino acid. Oxidized phenolics were more potent than the unoxidized forms.

The possible role of the enzyme in plant pathogenesis was discussed.
THE INFLUENCE OF ROOT PRUNING ON THE GROWTH AND TRANSPIRATION OF WHEAT UNDER DIFFERENT SOIL MOISTURE CONDITIONS
Authors: ANDREWS ROSALIE E. , NEWMAN E. I.
Published: May 2006

Summary

Two similar experiments were conducted with winter wheat growing in pots of soil. Plants about 5 weeks old were placed in a growth chamber under constant conditions. On half of the plants 60% of the roots were cut at their origins; thus the root density was altered, but not the volume of soil. Half of these pruned pots and half of the unpruned were maintained at field capacity. The remainder were allowed to dry out to somewhat drier than —15 bars soil matric potential (this took 8 and 13 days in the two experiments), and the plants were then harvested. In the dry treatment root pruning did not reduce growth. There is some indication that root pruning increased growth in the dry treatment and reduced it in the wet; but this is not conclusive. When the mean of wet and dry treatments together is considered, root pruning had no detectable effect on either root or shoot growth. In the wet treatments root pruning reduced transpiration by about 25–30%. In the dry treatments as the soil dried out the relative difference in transpiration rate between pruned and unpruned plants decreased. This result differs from a previous expectation that root density would have more effect on transpiration in dry soil than in wet.
LOW‐POWER ELECTRON MICROSCOPY OF THE ROOT CAP REGION OF EUCALYPT MYCORRHIZAS
Authors: CHILVERS G. A.
Published: May 2006

Summary

Low‐power electron micrographs of a eucalypt mycorrhiza are presented which show how root cap cells are progressively decomposed by invasion of fungal hyphae. The development of tannin‐like deposits in cells of the root cap and epidermis is discussed briefly.
TERNEUZEN AND BURIED FORESTS OF THE EAST ANGLIAN FENLAND
Authors: GODWIN H.
Published: May 2006

Summary

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

Summary

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

Summary

The stratigraphy and palaeobotany of the Late‐glacial and Post‐glacial deposits in the Gordano valley, North Somerset, have been investigated. At the west end of the valley there is a lake basin which is cut off from the east end by a transverse sand bar. This bar appears to have prevented the sea from penetrating to the head of the valley during the main eustatic rise in sea level. The local conditions have allowed peat formation from Late‐glacial times in the basin which contains a record of vegetational history not hitherto recorded in Somerset. In the Somerset Levels the pre‐Atlantic peat deposits are either out of reach beneath estuarine clays or have been eroded away.

During the Late‐glacial period the vegetation present in the Gordano valley was the same type of open herbaceous calcicolous vegetation recorded elsewhere in southern Britain. The pollen record from the profiles further shows that the Middle and Late Boreal stages of forest development are also similar to those in other parts of southern Britain. The main phase of peat formation in the Gordano valley dates from the onset of the Atlantic period. The upper peat layers are indicative of the establishment of fen communities and not raised bog as occurred in parts of the Somerset Levels. Peat which is representative of Zone VIII is missing, partly on account of human activities but also because the sea entered the east end of the valley during the Romano‐British marine transgression.
CHANGES IN GROWTH AND METABOLISM OF EXCISED PEA ROOTS ASSOCIATED WITH IRON DEFICIENCY
Authors: ABBOTT A. J.
Published: May 2006

Summary

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

Summary

The structure of the root haustorium and the hairs of the shoot of Odontites has been examined by light microscopy. The haustorium provides a direct xylem‐xylem link between root of host and hemiparasite. Tracer studies show that solutes move across this pathway from the host to the shoot of the hemiparasite.

Three types of hair clothe the shoot. They develop precociously, commencing to function in guttation before the stomata are perforated and the vascular tissues are differentiated.

Guttation fluid and bleeding sap of members of associations of Odontites with barley or Stellaria media were analysed for phosphate, nitrate, calcium, potassium, amides and amino acids. The results suggest that the shoots of the hemiparasite and its host can absorb selectively the solutes supplied from their roots.

Microautoradiographic studies of the distribution of [3H]leucine fed to shoots of Odontites through the xylem show that cells bordering on the transpiration pathway actively assimilate the radiosubstrate. Mesophyll cells and glandular hairs of the leaf are particularly active in this respect. It is suggested that glandular secretion plays a relatively important role in directing solutes mto young parts of the shoot.
UPTAKE AND METABOLISM OF EXOGENOUSLY SUPPLIED SUGARS BY BROWN ALGAE
Authors: DREW EDWARD A.
Published: May 2006

Summary

In nine of eleven species of brown algae tested, much of the 14C‐glucose taken up from aqueous media was readily leached out again during subsequent washing in ice‐cold seawater. Whilst none of the unleachable fraction was converted to 14C‐mannitol, a considerable proportion was incorporated into insoluble glucose polymers and some was lost in respiration.

Two species—Ascophyllum nodosum and Pelvetia canaliculata—were very different in that very little accumulated 14C‐glucose could be leached out. Most of the 14C‐glucose in the tissues of these two algae was rapidly converted to 14C‐mannitol, the remainder being either incorporated into insoluble compounds or respired.

These two species were also able to convert exogenously supplied 14C‐mannose to mannitol, and Pelvetia incorporated much 14C from exogenous mannitol into a disaccharide compound. Fucus, as a representative of the other species investigated, was unable to metabolize either exogenous mannose or mannitol.

None of the eleven species converted either galactose or fructose, supplied exogenously, to mannitol.
EXPERIMENTS ON THE JUVENILE‐ADULT PHASE CHANGE IN SOME WOODY SPECIES
Authors: ROBINSON L. W. , WAREING P. F.
Published: May 2006

Summary

The transition from the juvenile to the adult condition (‘phase change’) in woody plants normally occurs at an age and a size characteristic for the species and flowering does not occur until this change has taken place. By experiments with seedlings of birch (Betula verrucosa) grown either continuously under long days in a glasshouse, or periodically under alternating periods of long and short days in association with chilling treatments, it was shown that flowering occurs much sooner in the seedlings grown continuously (i.e. without periods of dormancy) than in seedlings of this species grown under normal outdoor conditions, or in the experimental seedlings grown ‘periodically’. Similar results were obtained with Japanese larch (Larix leptolepis) and black currant (Ribes nigrum) when flower‐inducing treatments appropriate for the species, viz. horizontal training or short days, respectively, were applied after continuously grown seedlings had attained a certain size. Further experiments were carried out with black currant to determine whether the attainment of a certain minimum size is necessary for phase change. The shoot tips of seedlings were removed when they had attained a size at which flowering does not occur and were rooted as cuttings; the latter plants were similarly treated and this process was repeated again twice. The final series of plants which had been derived in this manner initiated flowers in response to short days and thus had attained the adult condition, although at no stage had any of the successive rooted cuttings attained the minimum size at which phase change normally occurs in this species. It is concluded that size, per se, is not the primary factor determining the stage at which phase change occurs.

Experiments were carried out with Japanese larch and European larch (Larix decidua) in which scions from juvenile (non‐coning) seedling trees were grafted on to mature trees which produced abundant cones but little evidence was obtained that phase change was hastened by this treatment. On the other hand, a considerable proportion of scions from young trees, which were approaching the adult condition, initiated cones following grafting on to adult trees.

Phase change takes place in the shoot apical meristems, which appear to behave as autonomous units in the sense that their transition to the adult condition is apparently not determined by the amount of already differentiated tissue. It is suggested that phase change occurs after the meristems have undergone a certain number of cell divisions, so that the change is correlated with, but not determined by, the attainment of a certain size.
SOME EXPERIMENTAL OBSERVATIONS ON THE CLONE STRUCTURE OF A NATURAL POPULATION OF FESTUCA RUBRA L.
Authors: HARBERD D. J. , OWEN MYRFYN
Published: May 2006

Summary

It is confirmed that a worker observing for a season a pair of spaced plants of Festuca rubra growing alongside each other in an experimental garden can conclude with considerable reliability whether or not the two plants are of the same genotype. Out of over 3000 such comparisons made only nineteen proved to be difficult and, even in these cases, the opinion formed after the season's observations proved to be right sixteen times.

Sampling patterns more complicated than simple paired isolates are more productive of information and are not too difficult for observation so long as the number of isolates being compared at a time is less than about eight to twelve. The more complicated patterns are more difficult to collect, especially where species cover is low or variable and, for this reason, their use can lead to bias in the observations.

The clonal constitution of the population is not uniform over the site. There is a tendency for F. rubra to be more abundant in those parts of the site where the local population is dominated numerically by a single clone. The element of non‐randomness introduced by any sampling method which utilizes isolates from discrete parts of the site is likely to generate serious bias in the results.

Small portions of the site are colonized by several different clones intermixed with each other—the mean number of clones present in a 15 × 15 cm turf being 5.2. The chances of two isolates from the population being of the same genotype fall off with distance from about 42% at 2.5 cm apart to 1% at 320 cm.

By contrast with a population described earlier, this population is made up of very many clones, several of them being extensively reduplicated, but none of them so extensively as to numerically dominate the population. There are many differences between the two populations in ecology and probably in history but the causes of the different constitutions were not investigated.
SPORE DEVELOPMENT IN THE BROWN ROT FUNGI (SCLEROTINIA SPP.)
Authors: WILLETTS H. J. , CALONGE F. D.
Published: May 2006

Summary

Development of macro‐ and microconidia of several species of Sclerotinia causing brown rot of rosaceous fruits was studied by light and electron microscopy.

Macroconidia are produced by budding and develop in acropetal succession. Septa form centripetally across the constricted regions between the spore initials of a chain. A single pore in each septum permits movement of cytoplasm and organelles along the chains of spores and these pores are probably not plugged until just before the spores are liberated. The ultrastructure of the mature macroconidia is similar to that of the vegetative hyphae, indicating the unspecialized nature of these spores.

Microconidia are formed in succession by extrusion from the tips of terminal phialides. The developing spore is protected by a thin wall and is finally cut off by formation of a basal septum. An uneven splitting of this septum occurs, the thicker part becoming the basal wall of the spore. The latter remains loosely attached to the phialide until another spore is produced. Extrusion of the spores leaves a collar or rim just behind the apex of the phialide. The mature spore contains a large lipid body, a single large nucleus, a small amount of cjrtoplasm and one or two small mitochondria. It is thus of simpler organization than the macroconidium.

The development and structure of the two types of spore are compared and the differences correlated with function.