12,164 research outputs found
Charlie May Simon materials
No full textThis collection contains materials relating to Arkansas author Charlie May Simon
Morphogenesis in the moss physcomitrella patens
No full textA method was developed for recording the development of moss protonema using time-lapse video microscopy. This has provided a detailed record of the time-course of development from spore germination to the production of gametophores. Detailed records of the growth of primary and secondary chloronema, the transition of primary
chloronema to caulonema, and the development of side-branches were obtained. Filaments were found to undergo the transition to caulonema earlier than previously
thought. The majority of caulonemas ide-branches were found to begin as chloronema and switch to caulonema after one or two cell cycles. The early cell divisions of bud
formation were found to follow a distinct pattern, which was upset by high concentrations of cytokinin and lanthanum. The response of caulonema apical cells to
polarotropic light was recorded and compared to the gravitropic response.
The time-lapse studies provided the basis for the further development of the quantitative analysis of protonemal branching patterns to include second and third
side-branches of a sub-apical cell, and transitional caulonema. Analysing side-branch patterns should allow the detection of developmental mechanisms underlying the
determination of side-branch fate. The potential of this method for assessing the effect of hormone treatments and for analysing more precisely mutant phenotypes was
explored. An analysis of bud spacing was carried out to determine if the formation of a bud on a filament was inhibitory to other buds forming on the same filament. It was found, to the contrary, that buds tended to form in clusters.
The hypothesis that the primary mode of action of cytokinin is an enhanced influx of calcium ions into the cell was investigated. Classical electrophysiology was used in
order to detect any change in membrane potential suggestive of ionic fluxes in response to cytokinin treatment. No definitive changes in membrane potential were detected in response to cytokinin. This appeared to rule out the involvement of voltage-regulated channels in cytokinin action. The effects of some inhibitors used in
studies of calcium on the moss protonemal system were examined. It is suggested that the concentrations commonly used had toxic effects that were not specific to calcium
channels. The ionophore A23187 was used to characterise the protonemal response to a sustained influx of calcium. Some mutant strains were found to have a differential
response to the ionophore. This may mean that they have mutations affecting their calcium regulatory system.
Two new techniques of imaging calcium were used in order to detect changes in intracellular calcium in response to cytokinin. A method was developed for loading the dual wavelength fluorescent dye Indo-1 into moss protonema using iontophoretic microinjection, and intracellular calcium was imaged using ratio-image technology. Wild-type moss and some mutant strains were also successfully transformed with the gene for apoaequorin, and calcium luminescence measured in response to cold-shock and plant hormones. Some different responsesto temperatures hock were apparent in
one of the transformed mutants. Preliminary experiments did not reveal any aequor independent calcium luminescence in response to cytokinin
An ecophysiological study on the moss hydrogoniuh fontanum from the Asir mountains, Saudi Arabia
No full textThe thesis describes a study on the ecophysiology of the moss Hydrogonium fontanum (C. Mail.) Jaeg., the dominant plant at a waterfall in Saudi Arabia. The influence of environmental variables and water stress on the growth, stress metabolite accumulation and phosphatase activities of the moss was studied in laboratory axenic culture along with observations and experiments conducted in the field. The variables chosen for growth experiments were light flux, flooding, nutrient concentrations and water stress. For phosphatase activities, the influence of temperature, pH, ions, water stress were studied. Differences were found in phosphatase activities for rhlzoids, protonema and leafy shoots of the moss and, therefore, the phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities of these fractions were also investigated. H. fontanum was originally collected from the tufa-depositing waterfall (Water chemistry - 44 mg 1(^-1) Na, 44 mg 1(^-1) Ca). High Na and Ca had significant positive effect on yield of the protonema under the laboratory conditions. Low light intensity (10 µmol photon m(^-2) s(^-1)) decreased the yield, but high light intensity (90 µmol photon m(^-2) s(^-1)) increased the yield of the protonema. The moss showed no response to water stress in respect to praline accumulation. Protein content decreased significantly over 48 h with increase in water stress. The Influence of water stress was greater in terms of dry weight and chlorophyll content changes in protonema than in leafy shoots. The protonema was capable of using various organic P substrates as sources of phosphorus and showed both PMEase and PDEase activities. PMEase and PDEase activities were detectable in all moss fractions (rhizoids, protonema, leafy shoots). Laboratory grown material showed higher activities than field grown material. Rhizoids produced the highest PMEase and PDEase activities among the moss fractions. Some leafy shoots collected from the field had low phosphorus content with high phosphatase activities, while others had high phosphorus content with low phosphatase activities. Changes in phosphatase activities in batch culture were studied in relation to growth rate. PMEase activity was first evident when cellular P was 1.15% with low activity (0.117 µmol pNP mg d. wt(^-1) h(^-1)) and PDEase appeared 4 days later when cellular P was 0.54%. The activities increased up to day 12 after which the activities maintained this level. The optimum temperatures, measured over a period of 1 h, for PMEase and PDEase activities were 60 ºC and 65 ºC with pH optima of 5.5-6.0 and 6.4-6.8, respectively. Of the six ions tested, Ca, Zn and P had significant inhibitory effects on the activities at the highest concentration used (10 mM).Drying the moss decreases PMEase and PDEase activities by about 23% and 21% (5-d) and 3.7 and 2,8 times (3 months), respectively. Water stress (PEG treatment) also reduced significantly the activities of PMEase and PDEase with a greater effect on the activity of the latter. A brief comparison in PMEase activity using two different substrates p- nitrophenyl phosphate (pNPP) and 4-methylumbelliferyl phosphate (4-MUP) was made to investigate the pH optima and time course. PMEase activity measured using 250 µM 4-MUP was about 60% of that measured using the same concentration of pNPP
Simon Nyakot
No full textabstract: Simon Nyakot left his village when he was six years old.
“Lost Boys Found” is an ongoing, interdisciplinary project that is collecting, recording and archiving the oral histories of the Lost Boys/Girls of Sudan. The collection is a work-in-progress, seeking to record the oral history of as many Lost Boys/Girls as are willing, and will be used in a future book.Age: 27Region: LakeThis picture and bio was donated to the Lost Boys Found project from The Arizona Lost Boys Cente
Cahiers Saint-Simon
No full texthttps://www.persee.fr/renderCollectionCover/simon.pngThe Société Saint-Simon was founded in 1972 in order to promote studies about the Duke of Saint-Simon (1675-1755), namely about the work, life, and thinking of the Mémoires’s author. Each year it issues a Cahier Saint-Simon. It contains the Acts of the annual Journée d’étude in Versailles, but also Notes and Documents, News of the Society and Book reviews.Fondée en 1972, la Société Saint-Simon a pour but de développer les études concernant l'oeuvre, la personne et la pensée du duc de Saint-Simon (1675-1755), l’auteur des Mémoires. Chaque année, paraît un numéro de Cahiers Saint-Simon contenant les actes de la journée annuelle de Versailles, ainsi que des Mélanges, des Notes et Documents et une Chronique bibliographique détaillée
Cahiers Saint-Simon
No full texthttps://www.persee.fr/renderCollectionCover/simon.pngThe Société Saint-Simon was founded in 1972 in order to promote studies about the Duke of Saint-Simon (1675-1755), namely about the work, life, and thinking of the Mémoires’s author. Each year it issues a Cahier Saint-Simon. It contains the Acts of the annual Journée d’étude in Versailles, but also Notes and Documents, News of the Society and Book reviews.Fondée en 1972, la Société Saint-Simon a pour but de développer les études concernant l'oeuvre, la personne et la pensée du duc de Saint-Simon (1675-1755), l’auteur des Mémoires. Chaque année, paraît un numéro de Cahiers Saint-Simon contenant les actes de la journée annuelle de Versailles, ainsi que des Mélanges, des Notes et Documents et une Chronique bibliographique détaillée
Molecular support for Pleistocene persistence of the continental Antarctic moss Bryum argenteum
No full textWe examined sequence variation of ITS and phy2 for Bryum argenteum from Antarctica, sub-Antarctic, New Zealand and Australia to understand better taxonomic delimitations and resolve relationships between these geographic regions. Bryum argenteum has been recorded as two species, B. argenteum and B. subrotundifolium, in all four regions with the latter now referred to as B. argenteum var. muticum. We found disagreement between taxon delimitations (based on morphology) and molecular markers. All continental Antarctic specimens consistently formed a monophyletic sister group that consisted of both morphologically identified B. argenteum varieties, separate to all non-Antarctic specimens (also consisting of both varieties). We suggest, contrary to previous records, that all continental Antarctic (Victoria Land) populations are referable to B. argenteum var. muticum, while sub-Antarctic, Australian and New Zealand populations included here are B. argenteum var. argenteum. Additionally, since there was less genetic diversity within Victoria Land, Antarctica, than observed between non-Antarctic samples, we suggest that this is, in part, due to a potentially lower rate of DNA substitution and isolation in northern and southern refugia within Victoria Land since the Pleistocene.Simon F. K. Hills, Mark I. Stevens and Chrissen E. C. Gemmil
Simon Weir - The Sydney Surrealist
No full textExhibition catalogue of "Simon Weir - The Sydney Surrealist", Exhibition at Disorder Gallery, Darlinghurst NSW, Australia, in April 2024. The catalogue contains images of exhibited works and statements by the artist Simon Weir, the gallery Director Elliott Cole, and author and journalist Margie Smithurst
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