Floral histogenesis in the monocotyledons. III. The Juncaceae

1958 ◽  
Vol 6 (4) ◽  
pp. 285 ◽  
Author(s):  
C Barnard
Keyword(s):  
Cell Division ◽  
The Other ◽  
Flower Primordia ◽  
Other Hand ◽  
Tunica Layer ◽  
Morphological Nature ◽  
Floral Histogenesis

An account is presented of floral histogenesis in Luzula campestris (L.) DC., Juncus articulatus L., and Juncus vaginatus R. Br. The pattern of floral histogenesis in these species is similar to that in species of the Gramineae and Cyperaceae. Bracts, bracteoles, perianth members, and carpellary tissue arise by divisions of cells of the tunica. Periclinal divisions in the outer tunica layer (dermatogen) always occur in the initiation of these "foliar" type organs. The primordia of inflorescence branches, flower primordia, and stamens, on the other hand, arise as a result of cell division in the outer layers of the corpus and the inner layer of the tunica. Periclinal divisions in the dermatogen are not involved in the differentiation of these "cauline" type structures. The morphological nature of the placentas in Juncus is discussed; they appear to arise independently of the carpellary tissue and after the manner of "cauline" structures. The ovules in both Luzula and Juncus arise in similar fashion.

Floral histogenesis in the monocotyledons. I. The Gramineae

1957 ◽  
Vol 5 (1) ◽  
pp. 1 ◽  
Author(s):  
C Barnard
Keyword(s):  
Periclinal Division ◽  
The Other ◽  
Flower Primordia ◽  
Stamen Primordia ◽  
Other Hand ◽  
Previous Communication ◽  
Representative Species ◽  
Constant Feature ◽  
Floral Histogenesis

The pattern of floral histogenesis in a representative species from each of six tribes of the Gramineae is shown to be similar to that described in a previous communication for Triticum. Periclinal division of sub-hypodermal cells characterizes the origin of spikelet, flower, and stamen primordia. Periclinal divisions also occur in hypodermal cells during flower and stamen formation; and such divisions are more frequent at stamen initiation than at the initiation of flower primordia. Periclinal division of dermatogen cells never occurs during the formation of these organs, but is, on the other hand, a constant feature in the formation of glumes, lemma, palea, lodicules, and carpel. The hypodermis always contributes to the tissues of the glume and lemma primordia; it less frequently contributes to the tissues of the lodicule and palea, and only occasionally to that of the carpel. The morphology of the gramineous flower is discussed on the basis of floral histogenesis and the pattern of prorascular tissues in the gynaeceum. The literature dealing with floral histogenesis and the pattern of prorascular tissues in the gynaeceum.

Floral histogenesis in the Monocotyledons. IV. The Liliaceae

1960 ◽  
Vol 8 (3) ◽  
pp. 213 ◽  
Author(s):  
C Barnard
Keyword(s):  
Early Ontogeny ◽  
Periclinal Division ◽  
Flower Primordia ◽  
Independent Origin ◽  
Tunica Layer ◽  
Floral Histogenesis ◽  
In Cells

An account is presented of floral histogenesis in Bulbine bulbosa R.Br. and Stypandra glauca R.Br. The apex of the floral axis in both species has a two-layered tunica, and bracts arise through the periclinal division of cells of the inner layer of the tunica (hypodermis). In Bulbine, axillary flower primordia are initiated in the periclinal division of subhypodermal cells; in Stypandra the flower primordia are terminal and arise directly from the apices of branches of the inflorescence. In both species the perianth'members originate, in the same manner as the bracts, through periclinal divisions in cells of the hypodermis. Periclinal divisions may occur in the cells of the outer tunica layer (dermatogen) after the prinlordia are well formed. Divisions in subhypodermal cells in the area of perianth initiation are associated with the formation of a provascular strand and it is doubtful if such divisions contribute anything to the tissue of the perianth primordium itself. The stamens are initiated in the periclinal division of both hypodermal and subhypodermal cells. In Bulbine the carpels develop through periclinal divisions in the hypodermis and dermatogen. The placentas appear to arise through divisions in subhypodermal cells as structures adnate to the carpels. In Stypandra the carpels arise in a quite different manner through the periclinal division of subhypodermal cells. The margins of the carpels develop as the placentas and there is no suggestion in the early ontogeny of the gynaecium that the placentas have an independent origin.

scholarly journals CENP-C is a blueprint for constitutive centromere–associated network assembly within human kinetochores

2015 ◽  
Vol 210 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Kerstin Klare ◽  
John R. Weir ◽  
Federica Basilico ◽  
Tomasz Zimniak ◽  
Lucia Massimiliano ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
The Other ◽  
Microtubule Binding ◽  
Kinetochore Assembly ◽  
Binding Interface ◽  
Other Hand ◽  
Spindle Microtubules ◽  
Data Point

Kinetochores are multisubunit complexes that assemble on centromeres to bind spindle microtubules and promote faithful chromosome segregation during cell division. A 16-subunit complex named the constitutive centromere–associated network (CCAN) creates the centromere–kinetochore interface. CENP-C, a CCAN subunit, is crucial for kinetochore assembly because it links centromeres with the microtubule-binding interface of kinetochores. The role of CENP-C in CCAN organization, on the other hand, had been incompletely understood. In this paper, we combined biochemical reconstitution and cellular investigations to unveil how CENP-C promotes kinetochore targeting of other CCAN subunits. The so-called PEST domain in the N-terminal half of CENP-C interacted directly with the four-subunit CCAN subcomplex CENP-HIKM. We identified crucial determinants of this interaction whose mutation prevented kinetochore localization of CENP-HIKM and of CENP-TW, another CCAN subcomplex. When considered together with previous observations, our data point to CENP-C as a blueprint for kinetochore assembly.

scholarly journals VII. Further experiments and histological investigations on intumescences, with some observations on nuclear division in pathological tissues

1906 ◽  
Vol 198 (239-250) ◽  
pp. 221-263 ◽  
Keyword(s):  
Cell Division ◽  
Nuclear Division ◽  
The Other ◽  
No Formation ◽  
Other Hand ◽  
External Conditions ◽  
Stems And Leaves ◽  
Pathological Tissues

In a paper published in 1900 a description was given of certain pathological outgrowths, first called intumescences by Sorauer, but known as œdemata to American writers, occurring spontaneously on Hibiscus vitifolius , Linn. The paper is mainly anatomical , and the various modifications of intumescences found on the stems and leaves are described. On the stem the outgrowths originate by cell division, which is followed by the elongation of the cells concerned. At a later stage the stem intumescence is cut off by cork, so that the cells above the layer of cork die and collapse. In leaf intumescences there is less cell division and no formation of cork. Preliminary experiments were made to determine the conditions under which intumescences arise, and showed the importance of changes in the external conditions in connection with the question of the formation of outgrowths. Strong and healthy plants, grown in the open air , did not develop intumescences, nor did very weakly plants grown in a cool and poorly lighted, though damp, greenhouse. On the other hand, plants grown in warm, damp, well-lighted greenhouses produced intumescences in varying number and degree.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

Don’t Put Me in This Group

2019 ◽  
Vol 50 (2) ◽  
pp. 80-93
Author(s):  
Jort de Vreeze ◽  
Christina Matschke
Keyword(s):  
Positive Emotions ◽  
Negative Emotions ◽  
Negative Information ◽  
The Self ◽  
The Other ◽  
Other Hand ◽  
Group Memberships

Abstract. Not all group memberships are self-chosen. The current research examines whether assignments to non-preferred groups influence our relationship with the group and our preference for information about the ingroup. It was expected and found that, when people are assigned to non-preferred groups, they perceive the group as different to the self, experience negative emotions about the assignment and in turn disidentify with the group. On the other hand, when people are assigned to preferred groups, they perceive the group as similar to the self, experience positive emotions about the assignment and in turn identify with the group. Finally, disidentification increases a preference for negative information about the ingroup.

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