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Journal ArticleDOI

Über das Antherentapetum mit besonderer Berücksichtigung seiner Kernzahl

01 Feb 1954-Vol. 101, Iss: 1, pp 1-63
TL;DR: In der vorliegenden Arbeit wurden zur Prufung der jungst aufgeworfenen Frage, ob dem Vorkommen des einkernigen Tapetums eine gewisse systematischen Bedeutung zukame, nicht nur die Angaben uber das Einkernige Tapetum (vgl. die Zusammenstellung S. 15−17) kritisch gesichtet, sondern auch alle Angabens uber e
Abstract: Da in den letzten Jahren die Beobachtungen uber ein einkerniges Tapetum weiter zugenommen haben, liegt die Vermutung nahe, das dieses eine weitere Verbreitung hat, als bisher angenommen wurde. In der vorliegenden Arbeit wurden zur Prufung der jungst aufgeworfenen Frage, ob dem Vorkommen des einkernigen Tapetums eine gewisse systematische Bedeutung zukame, nicht nur die Angaben uber das einkernige Tapetum (vgl. die Zusammenstellung S. 15–17) kritisch gesichtet, sondern auch alle Angaben uber ein mehrkerniges Tapetum gesammelt und beide Vorkommen einander gegenubergestellt (vgl. den systematischen Teil). Es schien auch angezeigt, auf die verschiedenartigen Abweichungen von der normalen Tapetumentwicklung hinzuweisen, da in einzelnen solchen Fallen (bei weiblichen Pflanzen und pollensterilen Apomikten) ein Unterbleiben oder Verzogern von Kernteilungen in den Tapetumzellen beobachtet werden konnte, wodurch eine Einkernigkeit vorgetauscht sein kann. — Das Vorhandensein sowohl eines inneren als auch eines mehrschichtigen Tapetums ist in den vorliegenden Fallen nicht an eine bestimmte Kernzahl geknupft.
Citations
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01 Jan 2016
TL;DR: An eclectic ramble through phylogenetic aspects of floral structure includes the following: Sterling's view that the ancestral flowers of Rosaceae had only two ovules per carpel is examined and rejected, and it is concluded that centrifugality is not as valuable a phylogenetic indicator as some systematists had hoped it would be.
Abstract: An eclectic ramble through phylogenetic aspects of floral structure includes the following: (1) Sterling's view that the ancestral flowers of Rosaceae had only two ovules per carpel is examined and rejected. (2) Recent observations on the direction of androecial development in various taxa are reviewed, and it is concluded that centrifugality is not as valuable a phylogenetic indicator as some systematists had hoped it would be. (3) An attempt is made to reinterpret the inverted placental bundles of Capparales and the inverted "recurrent" bundles of Nestronia along morphogenetic lines. It is suggested that the inverted orientation is causally related to the initiation and differentiation of these bundles in isolation from previously formed vascular tissue. Floral anatomy turns some botanists into fantasts, others into iconoclasts. But despite the frequent speculative excesses, the occasional overreaction, and the recurring disagreements that are a part of the field, serially sectioned and cleared flowers continue to provide essential phylogenetic information. To begin with a straightforward example, consider Cronquist's (1968) suggestion concerning the origin of the Proteales, which he defines as Proteaceae plus Elaeagnaceae. Stressing similarities between the Proteales and the Thymelaeaceae (a point of difference with Takhtajan, 19702), Cronquist postulates that the origin of the order was in the Myrtales. For this to be true, the gynoecium in Proteaceae and Elaeagnaceae must be pseudomonomerous; in other words, it must be a syncarpous gynoecium that has acquired through evolutionary processes the superficial appearance of a single carpel. Noting that the Myrtales, which are syncarpous, must be excluded as possible ancestors if the gynoecium of the Proteales should turn out to be a solitary carpel, Cronquist adds: "The most likely origin of the Proteales would then be in the -Rosales." Serial cross sections through the gynoecia of various Proteaceae make Cronquist's favored position for the Proteales untenable, for there is no sign of pseudomonomery. Instead, each gynoecium has the three major vascular bundles and the ventral suture of

33 citations

Journal ArticleDOI
TL;DR: Kerne in den Antipoden von Eranthis hiemalis, Helleborus niger, Corydalis cava, CoryDalis nobilis, Dicentra spectabilis, Kleinia ficoides and Othonna crassifolia machen — nach Fertigstellung des haploiden Embroysackes — eine Periode des endomitotischen Wachstums durch.
Abstract: Es wurden je 3 Vertreter der Ranunculaceen, Papaveraceen und Kompositen in Hinblick auf ihren Antipodialapparat genau untersucht, wobei der Kernstruktur spezielles Augenmerk galt.

31 citations

Journal ArticleDOI
01 Jun 2005-Grana
TL;DR: The intermediate type of tapetum development in Bromeliaceae was probably derived secondarily from a secretory type, which occurs in most other Poales except Typhaceae.
Abstract: Bromeliaceae possess several features of pollen and anther wall development that are plesiomorphic for Poales, consistent with their putatively basal or near‐basal placement in this order. For example, successive microsporogenesis and the monocotyledonous type of anther wall formation are both plesiomorphic features that occur commonly in other Poales, with a few notable exceptions, notably the simultaneous type of microsporogenesis in Rapateaceae. The intermediate type of tapetum development in Bromeliaceae was probably derived secondarily from a secretory type, which occurs in most other Poales except Typhaceae.

29 citations

Journal ArticleDOI
01 Jul 1957-Planta
TL;DR: Das Tapetum ist bei beiden untersuchten Arten sporogenen Ursprungs and wird in Form einer peripheren Lage and von 1–2 Zellen breiten Balken gebildet, die den Loculus in unterschiedlich große Kammern aufteilen.
Abstract: Die Entstehung des Balkentapetums beiGentiana cruciata undImpatiens glandulifera wird beschrieben und in Beziehung zu den ubrigen Tapetumtypen gesetzt. BeiGentiana verlauft die Wandschichtenbildung meist zentripetal, oft (in 30% aller untersuchten Falle) auch zentrifugal. Die Entstehung der Zwischenschichten schreitet an der Loculus-Innenseite von einem Placentoid aus peripher fort. BeiImpatiens entstehen das Endothecium und die beiden Zwischenschichten stets in zentrifugaler Folge. Das Tapetum ist bei beiden untersuchten Arten sporogenen Ursprungs und wird in Form einer peripheren Lage und von 1–2 Zellen breiten Balken gebildet, die den Loculus in unterschiedlich grose Kammern aufteilen. Pollenmutter- und Tapetumzellen unterscheiden sich cytologisch und karyologisch (Kern- und Nucleolusvolumina und Chromozentrengrose). Kurz vor oder zu Beginn der Meiosis beginnen bei beiden Arten die karyologischen Veranderungen im Tapetum: seine Zellen werden beiGentiana durch Endomitose tetraploid, beiImpatiens durch freie Kernteilung zweikernig. Entgegen fruheren Literaturangaben bleiben sie bis zur Degeneration zellig. Beide Arten besitzen also ein cellulares Sekretionstapetum. — Der Nachweis der Endomitose im Tapetum vonGentiana cruciata erfolgte durch Strukturanalyse der Kerne (Endo-Inter- und Endo-Prophase) und den Nachweis der periodischen Wiederkehr dieser Strukturen in verschiedenen Kern-Grosenklassen.

26 citations

Journal ArticleDOI
TL;DR: The complete ontogenetic sequence for pollen in Cabomba caroliniana is characterized, showing the character plasticity that occurs in basal angiosperms and supporting the hypothesis that these elements function in entomophily.
Abstract: Cabomba is a small water lily genus that is native to the New World. Studies of pollen development and associated changes in the anther yield valuable characters for considering the evolution of reproductive biology in seed plants. Here we characterized the complete ontogenetic sequence for pollen in Cabomba caroliniana. Anthers at the microspore mother cell, tetrad, free microspore, and mature pollen grain stages were studied using scanning electron, transmission electron, and light microscopy. Tetragonal and decussate tetrads both occur in C. caroliniana, indicating successive microsporogenesis. The exine is tectate-columellate, and the infratectal columellae are the first exine elements to form, followed by a continuous tectum and a thin foot layer. A lamellate endexine initiates in the early free microspore stage, but becomes compressed in mature grains. Tectal microchannels and sculptural rods also initiate during the early free microspore stage, and significant pollenkitt deposition follows, supporting the hypothesis that these elements function in entomophily. The tapetum is morphologically amoeboid, with migratory tapetal cells directly contacting developing free microspores within the anther locule. Results from this study illustrate the importance of including ontogenetic data in analyzing pollen characters and in developing evolutionary and ecological hypotheses. The new palynological data also emphasize the character plasticity that occurs in basal angiosperms.

26 citations

References
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Journal ArticleDOI
J. Hutchinson1

1,036 citations

Journal ArticleDOI
TL;DR: The variation in structure of styles and stamens is described and discussed in separate sections, while their functions in the pollen-presenting mechanism is considered partly in section D of the present chapter and partly in Chapter III which deals with the irritability of the mechanism.
Abstract: I the Compositas the mechanism involved in the presentation of pollen to the insect visitor includes both styles and stamens. These essential oi'gans ai-e discussed, therefore, in the present chapter, but for convenience the variation in structure of styles and stamens is described and discussed in separate sections, while their functions in the pollen-presenting mechanism is considered partly in section D of the present chapter and partly in Chapter III which deals with the irritability of the mechanism.

109 citations

Journal ArticleDOI
Dontcho Kostoff1
01 Jan 1930-Genetica
TL;DR: NICOTIANA SPECIES-CROSSES Crosses in which the pollen-tubes do not reach the ovary, penetrate the micropyle, and induce parthenocarpy.
Abstract: NICOTIANA SPECIES-CROSSES . . . . . . . . . . . . . 35 1. Crosses in which the pollen-tubes do not reach the ovary 36 2. Crosses in which the pollen-tubes reach the ovary, penetrate the micropyle, and induce parthenocarpy 38 3. Crosses in which the/ertilization occurs, but in which the embryos usually die in a very early stage . . . . 42 4. Crosses in which the seeds germinate, but the plants die in the seedling stage . . . . . . . . . . . . . . 44 5. Crosses/rom which mature hybrids are obtained . . . 45 I I I . T H E S L O W G R O W T H O F T H E H Y B R I D E M B R Y O S A N D T H E

100 citations