bluuebunny/crossref_metadata_2025_split huggingface dataset:
PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: BRADBEER J. W. , GYLDENHOLM A. O. , SMITH J. W. , REST J. , EDGE H. J. W. 
Published: May 2006

SummaryThe effects of short exposures to low intensities of red, far‐red, blue and white light, applied separately and in certain combinations, have been studied with respect to plastid development in dark‐grown beans. ‘Rapid’ effects, occurring within a few hours of illumination, were the transformation and loss of the prolamellar bodies together with changes of the thylakoid area per plastid. All light treatments except blue, effectively transformed the prolamellar body and all the light treatments induced falls in prolamellar body volume. Red light, or illumination treatments containing red light, gave a ‘rapid’ stimulation to thylakoid development while blue and far‐red given alone were inhibitory.‘Slow’ effects on plastid development appeared to be primarily controlled by phytochrome, in addition to which there was some indication that low intensity treatments with blue light partially reversed the phytochrome effects. These ‘slow’ effects were on plastid expansion, plastid division and the formation of the internal membranes of the plastids.
NUMERICAL ZONATIONS OF FLANDRIAN POLLEN DATA
Authors: BIRKS H. J. B. 
Published: May 2006

SummaryFive numerical zonation methods have been applied to two sets of pollen data from deposits of Flandrian age at Scaleby Moss, Cumberland and Red Moss, Lancashire. The zonations suggested by these methods generally correspond to the conventional Flandrian pollen zones with the exception that the ‘elm‐decline’ is not consistently distinguished as a zone boundary. Reasons for this omission are discussed in terms of the weightings implicit in the various numerical methods.
EFFECTS OF VITAMINS AND NITROGEN SOURCES ON ASYMBIOTIC GERMINATION AND DEVELOPMENT OF ORCHIS LAXIFLORA AND OPHRYS SPHEGODES
Authors: MEAD J. W. , BULARD C. 
Published: May 2006

SummaryIn order to assess the role of endophytic fungi in the germination and growth of wild European orchids, Orchis laxiflora Lamk. and Ophrys sphegodes Mill, were tested on asymbiotic strictly defined media. In spite of minor differences between the two species, a good development was obtained with both, if sucrose, organic nitrogen and vitamins were added to a basic mineral medium containing ammonium nitrate. Casein hydrolysate as an organic nitrogen source could be replaced successfully by a reconstitution of its amino acids or by glutamine. Among the vitamins tested thiamine proved to be necessary to Orchis laxiflora.
REGENERATES FROM EXCISED PSEUDOLATERAL BRANCHES OF HETEROSIPHONIA PLUMOSA (ELLIS) BATT.
Authors: BONEY A. D. 
Published: May 2006

SummaryExcised pseudolaterals of Heterosiphonia plumosa showed rhizoid formation from surviving basal cells and regenerate formation either from the region of the rhizoid in close proximity to a basal cell, or directly from the basal cell. Survival of pseudolaterals and regenerate formation was obtained with fluorescent illuminations of 205 and 270 lux, but the majority of detached filaments failed to survive in illuminations of 320 lux and above, and at 105 lux and in the dark.
THE EFFECTS OF SPORE AGE ON GERMINATION AND GAMETOPHYTE DEVELOPMENT IN POLYPODIUM VULGARE L.
Authors: SMITH D. L. , ROBINSON P. M. 
Published: May 2006

SummaryIn the fern Polypodium vulgare L. increasing spore age leads to a decline in spore viability. It is suggested that the sigmoidal form of the survival curve is related to the fact that the spores of the cytotype used in the investigation are probably triploid. The other effects of increasing age include an increasing delay in germination, a decrease in the rate of germination, and an increase in the proportion of abnormal gametophytes. To some extent these effects are alleviated by high population density and low light intensity. Evidence is presented that the effects of age may be partly attributable to the declining ability of the spores to synthesize metabolites essential for germination and gametophyte development.
BREEDING SYSTEMS IN COTULA III. DIOECIOUS POPULATIONS
Authors: LLOYD DAVID G. 
Published: May 2006

SummarySome male and female plants of dioecious populations of seven Cotula species are strictly unisexual, or constant; other plants of the same populations are inconstant, with a low proportion of florets of the opposite sex (minority‐sex florets) which function normally. The distribution of minority‐sex florets among heads of male and female plants is shown by rank‐frequency curves. The average inconstancies of males and females are quantified as the proportions of genes transmitted via gametes of the minority‐sex florets, estimated by the proportions of minority‐sex florets. The average inconstancy of males is 9.9 × 10−4; that of females is 4.3 × 10−4. The Primary Sex Index, 0.9993, is the average constancy (1—inconstancy) of all individuals. This provides a measure of the degree of separation of male and female gamete functions in the two sexes, on a scale from 0.5 (sexual monomorphism) to 1.0 (complete separation of the sexes).The sex Asymmetry Index, male inconstancy–female inconstancy/male inconstancy + female inconstancy, + 0.39, measures the relative magnitude of inconstancies of the two sexes on a scale from –1.0 (androdioecy) to + 1.0 (gynodioecy). Male and female heads differ in several secondary characters. The progeny of experimental crosses show that females are heterogametic and males are homogametic for sex‐determining chromosomes. Males and females occur in equal numbers in the progeny of male × female crosses and in natural populations.The distribution and experimental manipulation of sex inconstancies provide considerable information on the origin and genetic maintenance of dioecy. The evolution of dioecy in Cotula has been accomplished by divergence in the sexes of the timing of the switch from male floret to female floret formation during head development, rather than by the introduction of male‐ and female‐sterility genes. No genes essential for female reproduction are restricted to the Y chromosome. A polyploid series in the dioecious populations (2n= 52 to 2n=c.312) indicates an ‘active Y’ mechanism, and may have been facilitated by the regeneration of sexual dimorphism from inconstant females with new chromosome numbers.
BREEDING SYSTEMS IN COTULA IV. REVERSION FROM DIOECY TO MONOECY
Authors: LLOYD DAVID G. 
Published: May 2006

SummaryIn both Cotula dioica and C. dispersa there are dioecious populations and simple‐monoecious populations (in which all heads of all plants are bisexual, with numerous male and female florets.) In addition, in C. dioica and also in C. rotundata, there are complex‐monoecious populations in which all plants have both male heads and bisexual heads with one or a few female florets and many male florets; the plants resemble inconstant males of dioecious populations in their sex expression, secondary sex characters and genetical behaviour, but they are not associated with females and are therefore equisexual (contribute equally via male and female gametes during sexual reproduction). In C. dispersa, there are also ‘unisexual male’ and ‘unisexual female’ populations resembling one or other sex of dioecious populations. ‘Unisexual’ populations sometimes have a small proportion of florets of the opposite sex and hence may produce a few seeds; when they reproduce sexually, the plants are functionally equisexual. One population of C. dispersa has a single patch of males in a large area of females.It is postulated that ‘unisexual female’ populations arise by the loss of males from a dioecious population. Rare seeds produced on these females (the heterogametic sex in dioecious populations) may lead to the reappearance of males, producing a dimorphic population. Further male × female crosses regenerate normal dioecy by equalizing the numbers of males and females. Following the loss of females from a dioecious population, ‘unisexual male’ populations may restore seed production by selection for increased proportions of female florets. In this way, dioecy reverts to simple‐monoecy via ‘unisexual male’ populations and complex‐monoecy. Reversion to monoecy has probably occurred independently in the three species.
NITROGEN FIXATION IN THE ROOT NODULES OF VICIA FABA L. IN RELATION TO THE ASSIMILATION OF CARBON
Authors: LAWRIE ANN C. , WHEELER C. T. 
Published: May 2006

SUMMARYNitrogenase activity of the root nodules of field‐grown Vicia faba increased during plant growth until 3–4 weeks after the onset of flowering. The subsequent decline in activity was never greater than to 20% of the maximum, until finally plants were killed by frost. Nodules of medium size (100–200 mg fresh weight) showed greatest nitrogenase activity.After photosynthesis in 14CO2 for 30 min, maximum accumulation of 14C‐assimilates in the nodules occurred within 90 min of synthesis. The relatively low levels of radioactivity associated with the organic acid fraction of the nodules, the absence of sucrose which is present in large quantities in the roots and the appearance of radioactivity in the nodule amino acids within 30 min of feeding the shoot 14CO2 show that photosynthates are rapidly metabolized on arrival in the nodules. The distribution of radioactivity among the constituents of the basic fraction confirms the importance of glutamate, glutamine and aspartate as early products of the metabolism of the fixed nitrogen in broad bean nodules receiving ample supplies of new photosynthates.
DEVELOPMENTAL STAGES IN A NONHETEROCYSTOUS FILAMENTOUS CYANOPHYTE
Authors: LADHA JAGDISH K. , KUMAR H. D. 
Published: May 2006

SUMMARYDevelopmental stages broadly similar to those previously reported in Nostoc have been seen in an Oscillatoria‐like cyanophyte isolated from nature and grown in unialgal cultures. Apparent cell fusions and anastomoses occurred in cultures raised from single filaments.
SOME OBSERVATIONS ON F2 AND BACKCROSS PLANTS DERIVED FROM HYBRIDS BETWEEN PAPAVER DUBIUM L. AND P. LECOQII LAM.
Authors: HUMPHREYS M. O. 
Published: May 2006

SUMMARYPlants of the F2 and backcross generations derived from F1 hybrids between Papaver dubium L. (2n= 42) and P. lecoqii Lam. (2n= 28) were studied. It was deduced from the chromosome numbers of the F2 and backcross plants that the successful F1 gametes possess high chromosome numbers. This phenomenon is explained in terms of‘genomic buffering’, i.e. F1, gametes with large numbers of chromosomes are better buffered than those with small numbers of chromosomes to withstand the effects of a mixture of alien chromosome material resulting from meiosis in F1 hybrids between polyploids. The importance of this phenomenon is discussed in relation to the evolution of polyploid species of Papaver in Section Orthorhoeades.
CRITERIA OF INTACTNESS AND THE PHOTOSYNTHETIC ACTIVITY OF SPINACH CHLOROPLAST PREPARATIONS
Authors: LILLEY R. McC. , FITZGERALD M. P. , RIENITS K. G. , WALKER D. A. 
Published: May 2006

SUMMARYChloroplast preparations capable of rapid rates of photosynthesis contain large numbers of intact (Class A) chloroplasts and smaller numbers of ruptured (Class C) chloroplasts. It is suggested that there is also a third or intermediate class in which the envelope has re‐sealed following rupture and release of stromal protein. The number of re‐sealed chloroplasts seems to be lowest in preparations containing the largest proportion of Class A chloroplasts. Assays for intactness based on the ability of Class C chloroplasts to utilize ferricyanide as a Hill oxidant are quick and convenient but do not distinguish between Class A and re‐sealed chloroplasts. If it is assumed that there is an inverse linear relationship between percentage intactness and ability to react with ferricyanide, such assays over‐estimate the proportion of intact chloroplasts and, therefore, underestimate their photosynthetic activity and protein content when these are expressed on a chlorophyll basis.
SOURCES OF ATP FOR ACTIVE PHOSPHATE TRANSPORT IN HYDRODICTYON AFRICANUM: EVIDENCE FOR PSEUDOCYCLIC PHOTOPHOSPHORYLATION IN VIVO
Authors: RAVEN J. A. , GLIDEWELL S. M. 
Published: May 2006

SUMMARYActive, ATP‐dependent phosphate influx in Hydrodictyon africanum can occur when pseudo‐cyclic photophosphorylation is the only plausible source of ATP. The conditions used for the elimination of other ATP sources involve illumination in air in the presence of cyanide and antimycin; the inhibitors prevent oxidative photophorylation, cyclic phosphosphorylation and non‐cyclic photophosphorylation with carbon dioxide or nitrate as electron acceptor. The relationship between phosphate influx and oxygen concentration under these conditions indicates a lower affinity for oxygen in pseudocyclic electron flow than that found for electron flow via cytochrome oxidase. Experiments with salicylhydroxamic acid, an inhibitor of the ‘alternate oxidase’ pathway of plant mitochondria which also has a low oxygen affinity and is cyanide‐insensitive, suggest that this oxidase is not involved in pseudocyclic photophosphorylation. This evidence for pseudocyclic photophosphorylation in vivo is consistent with measurements reported elsewhere on tracer oxygen uptake in. H africanum.
THE INFLUENCE OF ASPECT ON THE PATTERN OF SEASONAL GROWTH IN THE LICHEN PARMELIA GLABRATULA SSP. FULIGINOSA (FR. EX DUBY) LAUND
Authors: ARMSTRONG R. A. 
Published: May 2006

SUMMARYThe radial growth of samples of thalli of Parmelia glabratula ssp. fuliginosa were measured in situ on a south‐facing and a northwest‐facing rock surface each month from August 1973 to July 1974. In the periods August to October 1973 and March to July 1974 the radial growth of thalli in the northwest population was greater than in the south population. In the period November 1973 to February 1974 the radial growth of thalli in the south population was greater than in the northwest population. A physiological basis for the differences in seasonal growth in the two populations was suggested. The mean annual radial growth rate (in units of mm/year) was not significantly different in the two populations. However, the variability in radial growth rate between thalli was significantly larger in the northwest than in the south population. These results may be explained by genetic differences between the populations and environmental differences between the rock surfaces.
ENDOPOLYPLOIDY IN MAIZE SMUT NEOPLASMS INDUCED BY THE MAIZE SMUT Fungus, USTILAGO MAYDIS
Authors: CALLOW J. A. 
Published: May 2006

SUMMARYInfection of maize seedlings by Ustilago maydis results in neoplasia. The response of host nuclei and nucleoli to infection in these neoplasms has been examined in detail by Feulgen microspectrophotometry and quantitative interferometry. Seven days after infection, two distinct tissue zones could be recognized within the neoplastic leaf sheaths. Small cells around the vascular stele contained nuclei of 2C and 4C DNA content suggesting a meristematic function. Larger, vacuolate cells that form the bulk of the tissue contained nuclei of 16C, 32C, and 64C DNA levels, indicating substantial endopolyploidy. Nucleolar dry mass was substantially increased in infected cells (up to ten‐fold compared with controls), indicating enhanced ribosome synthesis. These results are discussed in relation to the hormonal control of DNA synthesis and mitosis.
THE GIANT LOBELIAS: TOXICITY, INFLORESCENCE AND TREE–BUILDING IN THE CAMPANULACEAE
Authors: MABBERLEY D. J. 
Published: May 2006

SUMMARYAn hypothesis on the origin of (i) the distribution of alkaloids and thorns, (ii) the position of the inflorescence, and (iii) arborescent forms in the Campanulaceae, considered in the light of recent studies onLobeliasect.Rhynchopetalum(Fres.) Benth. & Hook, f., is proposed. It is suggested that the primitive Campanulaceae were pachycaul forest plants and that it is possible to argue that on the continents those with alkaloids (Lobelioideae) were tolerant of browsing herbivores until the rise of alkaloid tolerance in herbaceous mammals when only armed forms could survive in lowland rainforest. In theLobelioideae., the terminal inflorescence is considered more primitive than the lateral which can be derived from the lowermost branches of the terminal with the onset of periodic inception of fertile primordia. In this way, non‐hapaxanthic shoots and the capacity for ‘tree‐building’ arise.
CALCULATION OF THE PRIMARY TRAJECTORIES OF DUST SEEDS, SPORES AND POLLEN IN UNSTEADY WINDS
Authors: BURROWS F. M. 
Published: May 2006

SUMMARYThe movement of dust seeds, spores and pollen released into winds which fluctuate in both speed and direction is considered in terms of the aerial mechanics of a small spherical particle moving under the Stokes' law of resistance and in a gravitational field. Equations of motion are established from which the aerial paths followed may be determined whenever it is possible to specify the movement of the environment accurately and in sufficiently fine detail. Example calculations show how deposition may arise on account of wind fluctuations, in addition to the normal process of gravitational sedimentation, and how very complicated trajectory geometry can result in quite simple flows which vary in both time and in space and time. It is also shown that very different positions of ultimate migration may be occupied at a particular time by particles released from positions quite close to one another in space and into unsteady winds.
COMPARISON OF THE EFFECTS OF A LOCALISED SUPPLY OF PHOSPHATE, NITRATE, AMMONIUM AND POTASSIUM ON THE GROWTH OF THE SEMINAL ROOT SYSTEM, AND THE SHOOT, IN BARLEY
Authors: DREW M. C. 
Published: May 2006

SUMMARYBarley plants were grown for 21 days in sand culture, continuously irrigated with nutrient solution. The rooting depth was divided into three compartments, one above another, such that different zones of the root system could be supplied with very low or high concentrations of a single inorganic nutrient, all other nutrients being maintained at a high concentration.Exposure of parts of the main seminal roots (axes) to high concentrations of phosphate caused a localized promotion of the initiation and subsequent extension of both first and second order laterals, compared with zones receiving very low concentrations of phosphate. This resulted in considerable modification to root form, but with only a small depression in shoot growth, compared with control plants receiving an ample supply to all parts of the root system. The extension of seminal axes was little affected by the concentration of phosphate to which they were exposed.Similar responses to those described for phosphate occurred with variation in concentration of nitrate or ammonium, but with potassium a localized supply promoted the growth of laterals to approximately the same extent as controls throughout the entire root system.The experiments show that adequate external concentrations of nitrogen and phosphorus are required by any part of the root system for optimal growth of laterals, but not axes. Possible mechanisms which compensate shoot growth when nutrients are supplied to only part of the root system, and agronomic implications, are discussed.
THE ROLE OF SEED PARTS IN THE INDUCTION OF DORMANCY OF HAZEL (CORYLUS AVELLANA L.)
Authors: JARVIS B. C. 
Published: May 2006

SUMMARYEmbryo dormancy is induced during the dry storage of hazel seed. During this inductive dry storage, it appears that inhibitors of germination move from the testa and pericarp through the cotyledons and into the embryonic axis. Microdrop applications of GA3 and ABA suggest that both have early affects on stimulation and inhibition of axis growth respectively. However, since both are transported in the seed affects on the cotyledons cannot be discounted.
TEMPERATURE AND THE GROWTH OF IMPATIENS PARVIFLORA DC.
Authors: ELIAS C. O. , CAUSTON D. R. 
Published: May 2006

SUMMARYThe growth of Impatiens parviflora DC. under four temperature regimes (13°C, 16°C, 20°C and 23°C) and a constant 18 h photoperiod was analysed using the traditional methods of growth analysis. Temperature had a very marked effect upon the growth rate, but the net assimilation rate was not markedly temperature‐dependent. The results are discussed in the context of previous work on I. parviflora, notably that by Evans and Hughes in respect of light intensity and also in the light of a simple model presented by Warren Wilson (1972), in which the main growth analysis parameters were related to source and sink activities in the plant.
BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)
Authors: BAKER N. R. , HARDWICK K. 
Published: May 2006

SUMMARYA quantitative study is made of the changes in the soluble sugar content of developing cocoa leaves. Fructose, glucose, inositol and sucrose were the major sugars present. The possibility that endogenous sucrose concentration can affect chloroplast development is considered.Estimates of the net daily sucrose synthesis in a developing cocoa leaf are made from photo‐synthetic and respiration rate measurements, and it is shown that the leaf does not become self‐dependent for respiratory substrate until after the termination of leaf expansion.
ULTRASTRUCTURE AND RECRYSTALLIZATION OF PLANT EPICUTICULAR WAXES
Authors: JEFFREE C. E. , BAKER E. A. , HOLLOWAY P. J. 
Published: May 2006

SUMMARYA wick feed method was used to recrystallize a range of different plant epicuticular waxes from solutions in organic solvents. Using the scanning electron microscope the ultrastructure of the recrystallized wax from each species was compared with that of the wax on the corresponding intact plant surface and in many cases was found to be similar. It is concluded that the crystal structure of epicuticular waxes is greatly influenced by their inherent chemical and physical properties rather than by properties of the underlying cuticular membrane or by any mechanism of extrusion or transport of the wax to the plant surface.
CORRELATION BETWEEN THE BREEDING SYSTEM AND RECOMBINATION INDEX IN FIVE SPECIES OF SENECIO
Authors: GIBBS P. E. , MILNE C. , CARRILLO M. VARGAS 
Published: May 2006

SUMMARYThe species Senecio aetnensis Jan., S. joppensis Dinsm., S. squalidus L., S. viscosus L. and S. vulgaris L. have been compared for automatic selfing ability, capitulum conspicuousness, pollen yield, chromosome number and chiasma frequency. It has been established that the species S. aetnensis, S. joppensis and S. squalidus which have low automatic selfing ability have large, showy capitula, high pollen output and low recombination indices. The species S. viscosus and S. vulgaris which have a high selfing ability have relatively inconspicuous capitula, low pollen yields and a high recombination index. The differences in recombination index values are mainly due to the fact that the selfing species are polyploids but it may be significant that the highest average chiasma frequencies per bivalent were found in some S. vulgaris plants. The adaptive significance of a high recombination index in inbreeding taxa is discussed and it is suggested that a high chiasma frequency and/or polyploidy may have a preadaptive value in facilitating the change from outbreeding to inbreeding in some species.