bluuebunny/crossref_metadata_2025_split huggingface dataset:
LIGHT AND ELECTRON MICROSCOPE OBSERVATIONS ON ALGAL LYSIS BY BACTERIUM CP‐I
Authors: DAFT M. J. , STEWART W. D. P. 
Published: May 2006

SummaryBacterium CP‐I isolated from Scottish waters is an aerobic prokaryote with a high guanine: cyto‐sine ratio (68%), which causes lysis of a variety of blue‐green algae. When suspensions of algae and bacteria are mixed the bacteria can be seen to glide towards the algae where they become attached end‐on round the algal cells. There is evidence that the bacteria produce substances at the point of contact with the algae which are necessary for algal lysis to occur. Lysis of vegetative cells may occur within 30 minutes of the bacteria becoming attached. Heterocysts do not lyse in this way although their intracellular contents may eventually degenerate. When vegetative cells rupture, the protoplasmic contents, including gas vacuoles when present, are released and empty‐looking ‘ghosts’ which retain the original cell shape may remain for a time although these too eventually break down. There is some evidence that the mode of filament lysis may be random, intercalary or terminal.At the ultrastructural level the initial effect of CP‐I is to cause lysis of the L2 layer of the algal cell wall and this effect is similar to that obtained using lysozyme. This is followed by rupture or disintegration of the other cell wall layers, and ‘scroll’‐like structures, either of coiled up cell wall material (Microcystis) or of the plasmalemma (Nostoc) may be found scattered throughout the preparations of lysed cells. In fully lysed cells there is a loss of polyphosphate bodies, structured granules, gas vacuoles, and most other cellular inclusions. Released gas vesicles can be collected from the surface of the solution of lysed cells, and there is evidence that these vesicles may fracture easily near the conical ends. In fully lysed cells, the thylakoid membranes remain, often with wide lumens between. This thylakoidal system is contorted and branched, ramifies through the cell and shows constrictions of the membrane system at intervals. Continuity between the plasmalemma and the thylakoidal system can be seen clearly, Lipid droplets which are resistant to CP‐I treatment are found in the lumen of the thylakoidal system. Heterocysts are not as markedly affected by CP‐I as are vegetative cells, but eventually heterocyst disorganization also occurs. The use of CP‐I provides a technique for preparing material for the study of algal membranes and gas vesicles.
QUANTITATIVE INTERFEROMETRY OF ONION EPIDERMAL NUCLEI IN DEVELOPMENT AND IN SENESCENCE
Authors: KULFINSKI F. B. , PAPPELIS A. J. 
Published: May 2006

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

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

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

SUMMARYAn intensive 3‐month study of nitrogen fixation by Lupinus arboreus grown on open sand dunes and under different aged stands of Pinus radiata in New Zealand has been carried out. Nodule samples were obtained either by digging whole seedlings or by sieving 0.01 m3 soil cores. Nitrogen fixation as estimated by the acetylene reduction assay and 15N analysis agreed well with published data from biomass studies. On open dunes nodule growth and activity increased rapidly during spring and estimated nitrogen fixation reached a peak of 11.5 kg N ha‐1 week‐1 at about flowering. When fruits began to swell, both on open dunes and in forest sites, nitrogen fixation by lupins decreased.Light transmission in forest sites was not correlated with the time of pine thinning. Lupin growth, nodule biomass and nitrogen fixation in non‐flowering lupins was closely related to the amount of light transmitted. When the sand became very dry nitrogen fixation was reduced and moisture stress was considered to be a factor likely to limit nitrogen fixation in drier parts of the year.Nitrogen fixation by lupin within forest stands on sand dunes is sufficient to make a significant contribution to the nitrogen economy of the forest.
THE EFFECTS OF IMBIBITION DRYING TREATMENTS ON WHEAT SEEDS
Authors: HANSON A. D. 
Published: May 2006

SUMMARYWheat seeds were imbibed and re‐dried under conditions that did not give rise to radicle protrusion through the seed coat. When seeds pre‐treated in this way were planted in moist vermiculite, coleoptile emergence was faster than from untreated seeds. This advancing effect on coleoptile emergence (‘seed invigoration’) was most marked when the seedlings were grown at low temperature or under osmotic stress (i.e. under unfavourable conditions). The seed‐borne pathogen Septoria nodorum was not affected by an imbibing‐drying treatment.Conditions of imbibition and drying giving optimal invigoration are described and data on the metabolism of untreated and invigorated seeds are presented. Oxygen uptake and [14C]‐leucine incorporation into protein were more enhanced in aleurone layers than in embryos isolated from invigorated seeds. Both untreated and invigorated seeds showed very low α‐amylase levels when dry, although a‐amylase activity developed more rapidly in invigorated seeds during germination. Gibberellic acid alone was not able to replace an imbibing‐drying treatment.
EXUDATION OF 14C‐LABELLED COMPOUNDS FROM WHEAT ROOTS: INFLUENCE OF NUTRIENTS, MICRO‐ORGANISMS AND ADDED ORGANIC COMPOUNDS
Authors: ROVIRA A. D. , RIDGE E. H. 
Published: May 2006

SUMMARYWhen tops of 6‐day wheat seedlings grown in nutrient solution, sterile or inoculated with soil, received 14CO2, it was found that the radioactivity of the solution measured after 24 and 48 hours was reduced by the presence of micro‐organisms. Omission of phosphate from the sterile growth medium reduced the radioactivity of the root solution to 47% of the control. The addition of acetate buffer at pH 5 greatly increased exudation whereas the adjustment to a similar pH with H2SO4 or universal buffer or the addition of sodium acetate at pH 7 significantly reduced exudation.These results demonstrate that exudation of organic compounds from roots can be affected by the addition of substrates and butters used in root enzyme studies. From these results, it appears that some organic compounds in soil could influence the loss of carbon compounds from roots growing under natural conditions.
INHIBITOR LEVELS ASSOCIATED WITH GROWTH IN SEEDLINGS OF PINUS RADIATA
Authors: SWEET G. B. , ROOK D. A. 
Published: May 2006

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

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

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

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

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

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

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

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

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

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

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

SummaryLabelling index (LI) was determined in the cap, epidermis, cortex and stele over the apical mm of newly emerged, 0.2, 0.5 → 2 and 4 cm long secondary roots of Vicia faba. This parameter increased in each of the tissues investigated as the roots lengthened. These results have been discussed with respect to the onset of meristematic activity in more or less quiescent lateral root primordia about the time they elongate to form secondary roots.LI was also different in the epidermis, cortex and stele in roots of any one length. These differences were more evident in the more basal parts of the laterals examined and they increased with root elongation. On the basis of these results and others in the literature, it is suggested that changes in LI reflect one of the initial events taking place at the onset of cell differentiation and that it may be possible to study differentiation by examining cells from comparable parts of lateral roots which are at different stages of development.
LICHEN PHYSIOLOGY
Authors: GREEN T. G. A. , SMITH D. C. 
Published: May 2006

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

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

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

SummaryTwo methods for studying the role of stomata in controlling leaf water status are compared, using data for field grown spring wheat (Triticum aestivum L.). The first is based on comparisons of leaf water potential and stomatal conductance and their responses to different soil water treatments as obtained by irrigation or by placing plastic rainwater gutters between rows to remove a proportion of the incident rainfall. The second method exploits the varying potential evaporation and the consequent changing leaf water potential and stomatal conductance during the course of a day. Good stomatal control is indicated by large values of the ratio of the amount of variation in stomatal conductance to that of leaf water potential. A particular advantage of the latter method is that it does not require a range of soil water treatments, and it can therefore be more readily used to compare the degree of stomatal control in a range of genotypes. There was generally good agreement between the methods, with the second method showing greater sensitivity.Stomatal conductances were measured with a continuous flow diffusion porometer which had a thermostatically controlled leaf chamber. This feature had the advantage that conductances could be obtained directly from the output of the humidity sensor without the necessity for routine measurement of, and correction for, leaf temperature.