Large Rosettes Research Articles

EVIDENCE FOR NATURAL BIOLOGICAL CONTROL: INSECTS DECREASE SURVIVAL AND GROWTH OF A NATIVE THISTLE

Native thistles, in contrast to exotic species, are seldom noxious weeds. In this study, we evaluated one hypothesis for this difference: that the growth and fitness of native thistles are limited by natural enemies. Specifically, we tested the effect of insect foliage feeding on the survival and growth of large and small rosettes of tall thistle, Cirsium altissimum, using an insecticide exclusion experiment. Large juveniles were proportionally more damaged than were small ones. Insecticide reduced insect feeding, including overall intensity of plant damage and area removed or damaged on each of the two longest leaves, compared to controls treated only with water. As a result, both leaf growth and plant size increased significantly by the end of the growing season. Growth parameters showing major increases with the reduction in insect herbivory included upper rootcrown diameter, the total number of leaves, and the length of the two longest leaves on both large and small rosettes. Insecticide also reduced the mortality of large juveniles to half that of the controls. Thus, the study shows that the suite of naturally occurring, coevolved, foliage-feeding insects significantly reduces the growth and survival of rosettes of this native thistle under field conditions. The results provide strong support for the hypothesis underlying biological control of weeds programs.

Cervical cord ependymoma with numerous microrosettes

"Microrosette ependymoma," which is ependymoma with numerous microrosettes throughout the tumor, has rarely been reported. We describe an autopsy case of cervical cord ependymoma with two unusual features: the presence of numerous microrosettes and the formation of trabecular architecture. The tumor originated in the C2 segment of a man aged 23 years and gradually expanded over the following 15 years and 10 months until the entire cervical cord was involved. Beside the low grade of malignancy, the tumor cells exhibited a strong tendency to form microrosettes and trabecular architecture, which formed many perivascular pseudorosettes. The microrosettes mostly consisted of only two or a few more cells, in the absence of large rosettes. Thus the constituent cells were those forming perivascular pseudorosettes. Electron microscopy and immunohistochemistry characterized the ependymal properties of the microrosettes, whose lumina frequently contained fibril bundles similar to those of the Reissner's fiber fibrils, in addition to cilia and microvilli. The pathogenesis of the occurrence of numerous microrosettes is unknown; however, a defect in the mechanism of regulation of rosette formation and enlargement is the most likely explanation.

A new species ofMelanagromyza(Diptera: Agromyzidae) mining leaves ofBromelia pinguin(Bromeliaceae) in a dry forest in Costa Rica

Melanagromyza rosales, sp. nov., from Costa Rica is described and its natural history is summarized. Larvae are miners in leaves of Bromelia pinguin, a large terrestrial rosette plant. They form conspicuous longitudinal mines that may be over 1 m long. Adult emergence is virtually simultaneous for all individuals, probably triggered by temperature cues. Populations are low for many generations with brief periods of abundance.

Structural and ultrastructural characteristics of human pineal gland, and pineal parenchymal tumors.

We have studied 20 pineal parenchymal tumors (PPT) and 4 normal or cystic pineal glands both by light and electron microscopy and immunohistochemistry with antibodies against glial markers [glial fibrillary acidic protein (GFAP) and protein S-100] or neural/neuroendocrine markers [neurofilaments (NF), synaptophysin and chromogranin A]. Light microscopy revealed the cellular organization of pinealocytes in the normal gland and in different morphological types of pineal tumors (typical pineocytomas, PPT with intermediate differentiation, mixed PPT exhibiting elements of both pineocytoma and pineoblastoma and pineoblastomas). Immunohistochemistry showed the presence of GFAP and protein S-100 in interstitial cells in non-neoplastic pineal gland. Cell processes were labeled with anti-synaptophysin and anti-NF antibodies. No immunoreactivity was found for chromogranin A in non-neoplastic pineal gland. In pineocytomas, GFAP and protein S-100 were observed in interstitial cells. Synaptophysin and NF were present in the large rosettes of pineocytomas. Synaptophysin, NF and chromogranin A were present in pineocytomas with a lobular arrangement of cells. Anti-chromogranin A immunoreactivity was also seen in lobular areas of some PPT with intermediate differentiation. Analysis of normal human pineal gland by electron microscopy showed the presence of vesicle-crowned rodlets (VCR or synaptic ribbons), fibrous filaments (F), paired twisted filaments but few dense-core vesicles (DCV) in normal pinealocytes. Tumoral pineal cells appeared to differentiate either towards a neurosensory pathway characterized by the presence of sensory cells elements (VCR and F), or towards a neuroendocrine pathway, with the occurrence of many DCV. Immunogold labeling demonstrated the presence of chromogranin A in neurosecretory granules.

Determinants of thermal balance in the Hawaiian giant rosette plant, Argyroxiphium sandwicense.

The effects of leaf pubescence and rosette geometry on thermal balance were studied in a subspecies of a Hawaiian giant rosette plant, Argyroxiphium sandwicense. This species, a member of the silversword alliance, grows above 2000 m elevation in the alpine zone of two Hawaiian volcanoes. Its highly pubescent leaves are very reflective (absorptance in the 400-700 nm waveband=0.44). Temperature of the expanded leaves was very similar to, or even lower than, air temperature during clear days, which was somewhat surprising given that solar radiation at the high elevation sites where this species grows can exceed 1100 W m-2. However, the temperature of the apical bud, which is located in the center of the parabolic rosette, was usually 25°C higher than air temperature at midday. Experimental manipulations in the field indicated that incoming solar radiation being focussed towards the center of the rosette resulted in higher temperatures of the apical bud. Attenuation of wind speed inside the rosette, which increased the thickness of the boundary layer surrounding the apical bud, also contributed to higher temperatures. The heating effect on the apical bud of the large parabolic rosette, which apparently enhances the rates of physiological processes in the developing leaves, may exclude the species from lower elevations by producing lethal tissue temperatures. Model simulations of apical bud temperatures at different elevations and laboratory estimates of the temperature threshold for permanent heat injury predicted that the lower altitude limit should be approximately 1900 m, which is reasonably close to the lower limit of distribution of A. sandwicense on Haleakala volcano.

Induction of sclereid differentation in the pith ofArabidopsis thaliana(L.) Heynh

Differentiation of sclereids was induced in the pith of Arabidopsis thaliana by repeated cutting of developing inflorescences for 4 weeks. This is the first report of sclereids in A. thaliana. The treatment also resulted in large rosettes and enhanced cambial activity that formed considerable amounts of secondary xylem.

Trypanosoma manulis n. sp. from the Russian Pallas cat Felis manul.

The morphology of Trypanosoma manulis n. sp. is described from living and stained specimens obtained from the blood of a Pallas cat, Felis manul, from Kazakhstan. The cat was also infected with a Hepatozoon sp. and feline immunodeficiency virus. The morphology of the trypanosome most closely resembles that of Trypanosoma mpapuense Reichenow and Trypanosoma heybergi Rodhain found in bats. Trypanosoma manulis does not grow well in conventional media, but co-culture with African green monkey kidney cells in Eagle's Minimum Essential Medium supplemented with 10% fetal calf serum at approximately 27 degrees C resulted in luxuriant growth of trypanosomes. Under these growth conditions, epimastigotes adhered to the surface of the culture flask and to African green monkey kidney cells, as well as forming large rosettes. At 37 degrees C, although growth was poor, transformation of the epimastigotes into the bloodstream forms occurred. This represents the first report of a trypanosome of the subgenus Megatrypanum in a felid.

Microstructural evolution of Pb(Zr, Ti)O3 thin films prepared by hybrid metallo-organic decomposition

We report on the microstructural analyses of chemically prepared Pb(Zr0.53Ti0.47)O3 (PZT 53/47) films. Although several techniques were used to analyze films, transmission electron microscopy (TEM) was emphasized. Phase evolution of these films, fabricated using hybrid metallo-organic decomposition (HMD), was determined by processing films at temperatures ranging from 500 °C to 650 °C. Our films, when observed with an optical microscope, appeared to consist of two distinct phases: (1) a featureless matrix and (2) 1–2 μm diameter “rosettes”. PZT films fired at 500 °C consisted of a pyrochlore containing phase (featureless matrix) and contained no perovskite, whereas films fired at 600 °C were ferroelectric and were approximately 90% perovskite (rosettes) by volume. Our TEM analysis showed that the pyrochlore-containing phase consisted of interpenetrating nanocrystalline pyrochlore and amorphous phases, both with dimensions on the order of 5 nm. For PZT films processed at 650 °C, the perovskite phase was observed in two forms: (1) large (≍2 μm) rosette structures containing 30 nm pores and (2) dense equiaxed particles on the order of 100 nm. We propose that phase evolution—with increasing temperature of HMD PZT 53/47 films—consists of the following steps: (1) phase separation, probably occurring in solution, (2) pyrochlore crystallization, (3) heterogeneous nucleation of perovskite PZT, and (4) homogeneous nucleation of perovskite PZT.

Central Neurocytomas

We report herein the clinical and pathological features of 20 patients with central neurocytomas. Investigations for various differentiation antigens and cell type-specific markers were performed by immunohistochemistry using paraffin-embedded tissue. In addition, the expression of L1 adhesion molecule and of the various N.CAM (neural cell adhesion molecule) isoforms were investigated by immunoblotting studies in two frozen specimens. Central neurocytomas are clinically characterized by their intraventricular localization, occurrence in young adults, and good prognosis. It rarely occurs in patients over 50, but such cases have a poor prognosis. Total surgical excision is the best treatment. Radiotherapy is appropriate if surgery is incomplete or contraindicated. Histologically, central neurocytomas display the following features: an oligo-like pattern, usually associated with large fibrillary rosettes or perivascular arrangement, and a rich endocrine-type vasculature. Central neurocytomas have a remarkably homogeneous antigenic profile. GFAP expression is only found in scattered reactive astrocytes, S100 protein in reactive astrocytes and rare tumor cells. Among the pan-neuroendocrine markers, central neurocytomas always express neuron-specific enolase; they frequently express synaptophysin but never chromogranin A. Synaptophysin is the most reliable immunohistological marker for central neurocytomas; however, immunoreactivity could be lost with long formalin fixation. In these cases, electron microscopy is used to support the neuronal nature of the tumor cells. The expression of L1 adhesion molecule and the isoform 180 of N.CAM, indicates that central neurocytomas are formed by cells committed to neuronal phenotype. Nevertheless, advanced neuronal differentiation may be absent, as suggested by the persistence of embryonic N.CAM, the nonexpression of neurofilament proteins, and the absence of mature synapses in numerous cases. Central neurocytomas and neuroblastomas share some biochemical properties, but their respective clinicopathological features and biological behavior are dramatically different.

Carbon Relations of Flowering in a Semelparous Clonal Desert Perennial

Agave deserti is a long—lived, semelparous perennial of the northwestern Sonoran Desert that flowers after °50—55 yr. Measurements of CO2 exchange over 24—h periods indicated that leaves of flowering rosettes had 24% more net CO2 uptake than leaves of adjacent nonflowering rosettes during the first month of inflorescence production. Net CO2 uptake for leaves of flowering rosettes was 32% less thereafter than for leaves of nonflowering rosettes, as senescing leaves of flowering rosettes exhibited dramatic reductions in nitrogen and chlorophyll contents. During the course of flowering, levels of total nonstructural carbohydrate (TNC) in the leaves of flowering rosettes dropped from 38 to 6% of the leaf dry mass, indicating substantial translocation of stored carbon to the inflorescence. TNC reserves of the rosette provided 70% of the carbon required to produce the 1.53 kg inflorescence, and CO2 uptake by the leaves and the inflorescence provided the remaining 30%. Rosettes must attain a minimum size (> 1000 g dry mass) to initiate flowering, unless they are connected to a large flowering rosette. Small rosettes did not produce inflorescences when their rhizome connection to a large rosette was severed °4 wk before inflorescences emerged, suggesting that a chemical signal is transmitted through the rhizome that induces the small rosette to flower precociously. Small flowering rosettes could not complete formation of the inflorescence unless partially supported by carbon supplied by the connected large rosette. The contribution of the large rosette declined from 74% for a 0—30 g dry mass connected rosette to 35% for a 200—600 g rosette. For both small and large flowering rosettes, the translocation of substantial carbohydrate reserves from the leaves is essential for production of the inflorescence.

Microstructural Characterization of Ferroelectric Thin Films for Non-Volatile Memory Applications

ABSTRACTFerroelectric thin films are now being used in conjunction with semiconductor CMOS technology to produce non-volatile IC memory devices. Three film compositions across the lead-zirconate-titanate (PZT) phase diagram were examined by transmission electron microscopy (TEM). The films are produced using organo-metallic sol-gels and sintered using standard semiconductor processing techniques. The grain structure of these thin films differ greatly from bulk ceramic crystals and thin films prepared using other deposition techniques. For two compositions, Pb1.1 (Zr0.75Ti0. 25)O3 and Pb1.1 (Zr0.50Ti0.50)O3, the perovskite structure was found in large rosettes surrounded by the polycrystalline pyrochlore phase. In the Pb1.1(Zr0.25Ti0.75)O3 sample, perovskite grains were found with no evidence of the pyrochlore phase. Ferroelectric domains were imaged in all three samples.

Deep-sea lebensspuren: remarks on some echiuran traces in the Porcupine Seabight, northeast Atlantic

During an exploration of the Porcupine Seabight aboard the French submersible Cyana, large rosettes attributed to echiurans were observed on the muddy bottom, sometimes associated with clumped mounds showing tension gashes. The intrusion of cores into the gashed mounds resulted in the creation of a fountain-like current of water flowing out of the center hole of the rosette, illustrating a direct connection. These two types of traces, which are classified under distinct generic names in recent classifications of deep-sea lebensspuren, are presumed to be produced by the echiuroid worm, being the two ends of an L-shaped burrow. A sketch of deep-sea echiurans' mode of life is proposed.

Density Dependent Simulation of the Population Dynamics of a Perennial Grassland Species, Hypochaeris radicata

Hypochaeris radicata L. is a rosette-forming herb that often attains dominance after a number of years in newly established grassland like roadverges, but decreases afterwards. To evaluate the possible causes of its success and eventual decline, a transition matrix model was constructed simulating different management regimes, with parameter values estimated from preliminary field data. Mowing twice a year results in the largest initial population growth rate and the largest equilibrium density compared with the other simulated mowing frequencies (mowing once a year, uncut verge). Elasticity analysis indicated that the parameters that together form the pathway of sexual reproduction and those that represent vegetative ramification, are balanced with respect to their impact on population growth. This balance shifts with decreasing mowing frequency towards vegetative ramification. This is largely the result of variation in transitions of the pathway of sexual reproduction. Large rosette densities are maintained only when these variable transitions, such as germination and establishment of seedlings are optimal. This characterizes H. radicata as a fugitive species, rather than as a competitor, and helps to understand its replacement in a succession.

Water Relations and Plant Size Aspects of Flowering for Agave deserti

The percentage of rosettes of the monocarpic perennial Agave deserti that flowered annually in the northwestern Sonoran Desert varied ca. 50-fold for the 8 yr considered. The number of days when the soil water potential in the root zone was above -0.5 MPa, enabling A. deserti to take up water, was approximately linearly related to the annual precipitation, which also varied considerably year-to-year. The percentage of flowering in a particular year could not be predicted from the number of wet days in that year, the year before, or 3 yr before (r2 ≤ .10, P > .5), but there was a positive correlation between percentage of flowering and the number of wet days 2 yr previously (r2 = .33, P = .1). Also, years with much flowering tended to alternate with those of little flowering (r2 = .64, P = .05). Indeed, 95% of the annual variation in the percentage of the rosettes that flowered could be accounted for by the year-to-year alternations together with the number of wet days 2 yr before the flowering (P = .01). Although over 90% of the rosettes with inflorescences were large, averaging 66 leaves and inflorescences 4 m tall, flowering also occurred for a few small rosettes, averaging only nine leaves and inflorescences only 0.8 m tall. The small flowering rosettes were all attached to large flowering rosettes by rhizomes with living cortical cells, suggesting that a hormone or other chemical signal/condition could be passed to the small rosettes leading to their precocious flowering.

Vegetative reproduction as a stabilizing feature of the population dynamics of Yucca glauca.

The life history of Yucca glauca in the Great Plains was the subject of a four year field study. Data were incorporated in a stage transition model (based on rosette size) to explain how populations are maintained in spite of large regional and temporal variation in sexual reproductive success. Rosette size was found to be a good predictor of flowering effort, but a poor predictor of fruit set. Large rosettes that failed to set fruit, however, exhibited an increased capacity for vegetative reproduction. Asexual reproduction contributes to population stability by reducing the variance in annual recruitment, and perhaps by damping oscillations caused by departures from a stable stage distribution.

The first Meckel oration: on the causes of morphological differences in a population of guinea pigs.

The first morphological abnormality considered here was of a very superficial sort: deviations from the smooth coat of wild cavies and most guinea pigs. The deviations of "rough-furred" individuals range from a single irregularity or a single pair of rosettes to the "full rough" pattern. Roughness may be restricted to the hind toes, forehead, or hair around the eyes or belly, or (very rarely) to a small area on one side of the back. There is no indication of gene control in the last, and no analysis of the only strain (in Professor Castle's laboratory) that I have seen, of roughness restricted to the belly. A dominant gene, R, in combination with a semidominant modifier, M, account for the fancier roughs (R-MM toes only, R-mm full rough). A gene, st, that is completely dominant in the absence of R, semidominant in its presence, was descended from 3 animals from outside the colony. It accounts for a large forehead rosette, usually with a small white spot in front of its center. A statistically semidominant gene, Re, with extremely irregular, often asymmetric penetrance tends to cause rosettes about the eyes. This arose by mutation late in the history of the Whitman colony. It is strengthened by presence of R MM. Considerable variation occurs in the numbers of dorsal rosettes of R Mm and R mm. These have not been analyzed satisfactorily because the genetic differences are confounded by nongenetic ones. It is not practicable to summarize briefly all of the complex interaction effects of these factors, but it may be noted that the most surprising one had to do with genes St and R. The forehead rosette due to rr St closely resembles that of R mm (except for the absence of the pleiotropic white spot). The combination, R mm St St, shows none of the expected enhancement but instead shows nearly complete cancellation of the rosette. Moreover, the anterior dorsal rosettes of R mm st st are much reduced and seemingly shoved backward and laterally to give a large smooth shield back of the ears. St St also reduces the usual dorsal pair of rosettes of R Mm. With St st, all of these antagonistic effects are weaker and less regular. Another morphological deviation to be considered was the fairly common restoration of an atavistic little toe.(ABSTRACT TRUNCATED AT 400 WORDS)

Frost avoidance and freezing tolerance in Afroalpine ‘giant rosette’ plants

Abstract. The large leaf rosettes of the so‐called ‘giant rosette’ plants which inhabit the alpine region of tropical mountains are composed of a great number of adult leaves surrounding a central cone of developing leaves. Upon onset of the nocturnal frost period the adult leaves nyctinastically bend inwards and form a night‐bud around the central leaf bud. The insulating effect of the night‐bud was analysed in four species: Senecio keniodendron, Senecio brassica. Lobelia keniensis and Lobelia telekii which grow on Mt Kenya (Kenya). Freezing is avoided by a delay of cooling which is sufficient until rewarming by the next day's sunshine. A consequence of this delay is that the temperature in the nocturnal bud remains higher than that of the outer leaves which are often stiffly frozen after cold nights. Only one freezing point was detected on the leaf temperature recordings. Depending on the water state, the freezing points were in the range — 1°C to —4.2°C. Sucrose, amounting to 38% of the leaf dry weight, may act as a cryoprotectant for the cell membranes. Frost hardiness of the leaves, as determined with a laboratory method, was sufficient to enable the plants to survive during the nocturnal frost temperatures as measured in the field.

Juxtanuclear globule of the human fimbrial epithelium ciliary cell: a histo- and cytochemical study.

Microbiopsies of human Fallopian tube fimbrial epithelium were obtained during routine gynecological operations, and during pregnancy while undergoing hysterectomy in the first trimester or cesarean section in the third trimester. Specimens were studied under light and electron microscopes utilizing histo- and cytochemical techniques. Large juxtanuclear globules were demonstrated in the ciliary cell at all stages of the cycle. During the proliferative phase, these globules contained large lipid droplets and glycogen rosettes. The content of the globules in the early luteal phase was mostly amorphous electron-lucid material which failed to stain with PAS, alcian blue and the Millon reaction. However, reaction products of acid phosphatase as well as calcium precipitate were scattered in them as discrete granules. The same type of globule was found in early pregnancy. During late luteal phase and late pregnancy, the content of the globule was once again composed of lipids and glycogen. It seems that lipid and glycogen accumulate during the preovulatory phase, while depletion and dispersion of these substances occur in the periovulatory phase, probably due to increased energy utilization. Late luteal phase revealed subsequent replenishment of these reserves, as was also revealed in late pregnancy.

ADAPTIVE RADIATION IN THE HAWAIIAN SILVERSWORD ALLIANCE (COMPOSITAE-MADIINAE). I. CYTOGENETICS OF SPONTANEOUS HYBRIDS.

The silversword alliance of the Hawaiian Islands comprises one of the most spectacular arrays of life forms known in a relatively small, clearly natural plant group. Perhaps the best known member of this alliance is the Haleakala silversword (Argyroxiphium macrocephalum Gray). However, A. macrocephalum is only one of six species in a genus which includes plants called greenswords as well as those called silverswords (cf. St. John, 1973). They ordinarily form large basal rosettes of attractive silver or green leaves for a number of years before they finally produce an elongated inflorescence. Argyroxiphium macrocephalum normally does not branch and dies after producing its massive inflorescence (cf. Kobayashi, 1973a). It is thus, under normal conditions, an essentially herbaceous, monocarpic plant. The floral heads of sword plants are characteristically large (>3 cm) and radiate. Argyroxiphium occurs primarily as a pioneer plant on volcanic pumice or in bogs and is restricted to the islands of Hawaii and Maui. In marked contrast to Argyroxiphium the related endemic genus Dubautia of this alliance (sensu Keck, 1936) is comprised largely of woody, branched shrubs that produce small (<1.5 cm), discoid heads year after year. However, the genus shows a truly remarkable spectrum of variation from somewhat herbaceous, low-growing forms through woody shrubs to trees. Moreover, the recently rediscovered D. latifolia (Gray) Keck from Kauai is a large liana. Altogether there are about 25 species of Dubautia, some of which, like Argyroxiphium may also be found as pioneers on volcanic pumice or in bogs, but others are found in dry forests or in rain forests. Its distribution extends throughout the entire system of major islands from Hawaii to Kauai. A third, related Hawaiian endemic genus, Wilkesia, is comprised of two species, one of which is often monocarpic and produces a rosette of leaves at the summit of a usually unbranched woody stem (cf. St. John, 1971). The second species branches rather freely from the base and presumably flowers repeatedly. The heads of Wilkesia are fairly large and discoid. Wilkesia is found on dry slopes, primarily in Waimea Canyon, only on the island of Kauai. The remarkable array of life forms within the silversword alliance exploits almost every conceivable terrestrial habitat in Hawaii. Its representatives occur from near sea level to timberline and from areas that receive less than 45 cm of annual precipitation to perhaps the wettest place on earth, receiving about 1,300 cm of annual precipitation. These habitats range from very recent lava flows on Hawaii to mature rain forests on Kauai. In spite of the spectacular morphological and ecological diversity exhibited by the members of the silversword alliance, the occurrence of many natural intergeneric, intersubgeneric, and interspecific hybrids (Sherff, 1935, 1944; Kobayashi, 1973b; and Carr, 1978a) attests to the fact that they form a natural, genetically cohesive group that has in all probability resulted from rapid evolutionary differentiation after a single colonization by a progenitor, possibly in less than 10 million years (see Macdonald and Abbott, 1970 for a discussion of Hawaiian geology). Collectively, these plants constitute what may be considered an unparalleled ex-

Differential Changes in Isoenzyme Pattern of 6-Phosphogluconate Dehydrogenase in Individual Plants of Senecio sylvaticus L. during Development

The isoenzyme patterns of individual plants from a population of the annual Senecio sylvaticus was determined at four stages of development, i.e. small rosette stage, large rosette stage, shooting stage and flowering stage, by gelelectrophoresis. Changes of isoenzyme pattern occurred only in 6-phosphogluconate dehydrogenase, the other six enzymes tested, remained constant throughout life cycle. The isoenzymes of 6-phosphogluconate dehydrogenase were compartmentated in the cytosol and chloroplast. With ageing activity of the isoenzymes in the chloroplast decreased and that of those in the cytosol increased.