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Sporophyte development in Rhynia gwynne-vaughanii, an Early Devonian vascular land plant from the Rhynie chert, Aberdeenshire, UK

Morphologische Entwicklung in den frühesten Landpflanzen ist weitgehend undokumentiert. Diese Arbeit beschreibt die Entwicklung von Rhynia gwynne-vaughanii, einer Gefäßpflanze aus dem Unteren Devonischen Rhynie Chert. Propagulen und Pflanzenachsen wurden mit petrographischem Dünnschnitt, Lichtmikroskopie und Synchrotron-Röntgen-Tomographie Mikroskopie untersucht. Die Entwicklung in Rhynia gwynne-vaughanii wurde vom Sprossapikalmeristem (SAM) aus gesteuert. Die Entwicklung von spezialisierten Geweben und Organen könnte ebenfalls beschrieben werden. Die SAM der nicht-vaskulären Rhynie Chert-Pflanze Aglaophyton major wurde ebenfalls untersucht und unterscheidet sich strukturell von der von Rhynia gwynne-vaughanii. Unterschiede in der SAM-Struktur in diesen fossilen Pflanzen spiegeln den beobachteten Trend zu einer komplexeren SAM in bestehenden und morphologisch komplexeren Pflanzengruppen wider.

Morphological development in the earliest land plants is largely undocumented. This work describes the development of Rhynia gwynne-vaughanii, a vascular plant from the Lower Devonian Rhynie chert. Asexual propagules and plant axes were studied using petrographic thin sectioning, light microscopy and synchrotron X-ray tomographic microscopy. Development in Rhynia gwynne-vaughanii was directed from the shoot apical meristem (SAM). The development of specialised tissues and organs could also be described. The SAM of the non-vascular Rhynie chert plant Aglaophyton major was also examined and is structurally different to that of Rhynia gwynne-vaughanii. Differences in SAM structure in these fossil plants reflects the observed trend towards a more complex SAM in extant and more morphologically complex plant groups.

Titel: Sporophyte development in Rhynia gwynne-vaughanii, an Early Devonian vascular land plant from the Rhynie chert, Aberdeenshire, UK
Verfasser: Kearney, Patricia GND
Gutachter: Kerp, Hans
Organisation: FB 14: Geowissenschaften
Dokumenttyp: Dissertation/Habilitation
Medientyp: Text
Erscheinungsdatum: 2015
Publikation in MIAMI: 25.05.2018
Datum der letzten Änderung: 25.05.2018
Schlagwörter: Rhynia gwynne-vaughanii; Rhynie chert; frühe Landpflanzen; Pflanzenentwicklung; Unterdevon
Rhynia gwynne-vaughanii; Rhynie chert; early land plants; plant development; Early Devonian
Fachgebiete: Geowissenschaften, Geologie
Sprache: Englisch
Format: PDF-Dokument
URN: urn:nbn:de:hbz:6-58159732076
Permalink: https://nbn-resolving.org/urn:nbn:de:hbz:6-58159732076
Onlinezugriff:
Inhalt:
Declarations i–iii
Summary iv
Acknowledgements vi
Main vii
List of figures and tables xi
Appendix Figures xiv
Main
Chapter 1
Introduction and review: Land plant biology, phylogeny and evolution
1.0 Introduction 1
1.1 Land plant groups 2
1.1.1 Phylogeny of land plants - algae, bryophytes and vascular plants 3
1.1.2 Alternation of generations and reproductive biology in land plants 5
1.2 Physiological adaptation to land 6
1.2.1 Evolution of the terrestrial sporophyte shoot 7
1.2.2 Sporopollenin and a delay in spore production 8
1.2.3 Stomata 8
1.2.4 Water acquisition and physical support 9
1.3 Fossil evidence for early land plants 11
1.3.1 Lack of macrofossils for early land plants 12
Chapter 2
The Rhynie chert: History of research, geology, flora and analytical techniques
2.0 The Rhynie chert: Discovery and main scientific contributors 18
2.1 Stratigraphy and structural geology 19
2.2 Plant biota 19
2.2.1 Rhynia gwynne-vaughanii 21
2.2.2 Aglaophyton major 22
2.3 Analytical techniques 22
2.3.1 Light microscopy 22
2.3.2 Synchrotron X-ray tomographic microscopy 23
Chapter 3
Results: Light microscopy and synchrotron X-ray tomographic microscopy of asexual
propagules of Rhynia gwynne-vaughanii , and light microscopy of Aglaophyton major
3.0 Introduction 31
3.1 Development of asexual propagules in Rhynia gwynne-vaughanii 31
3.1.1 Propagules developing from epidermal cells 32
3.1.2 Propagules developing from hemispherical projections 33
3.2 Stages of Development 34
3.2.1 Pre-propagules Stage I 34
3.2.2 Early Globular Stage II 34
3.2.3 Late Globular Stage III 35
3.3 Synchrotron X-ray tomographic microscopy of Rhynia gwynne-vaughanii 35
3.3.1 Specimen RTK 4a/RTK4b 36
3.3.2 Specimen RTK 8 37
3.3.3 Specimen RTK 10 37
3.3.4 Specimen RTK 15 38
3.3.5 Specimen RTK 17 38
3.3.6 Specimen RTK 18 39
3.4 Light microscopy and the structure of the shoot apical meristem of Rhynia gwynne-vaughanii and
Aglaophyton major 39
3.5 Sporophyte development: shoot apical meristem, stomata, rhizoids and tracheids
40
3.5.1 Cell division in the shoot apical meristem 40
3.5.2 Stomatal guard cell and rhizoid development 40
3.5.3 Tracheid development in Rhynia gwynne-vaughanii 41
Chapter 4
Sporophyte development in Rhynia gwynne-vaughanii and the evolution of sporophyte
morphological complexity
4.0 Introduction 63
4.1 Asexual reproduction 63
4.1.1 Asexual reproduction in Rhynia gwynne-vaughanii via somatic cells 64
4.1.2 Universal growth regulators controlling plant development 65
4.1.3 Developmental pattern of asexual propagules 67
4.2. Comparative developmental morphology: Rhynia gwynne-vaughanii and extant land plants
69
4.2.1 Bryophytes 69
4.2.2 Lycophytes and Monilophytes 70
4.2.3 Gymnosperms and Angiosperms 71
4.3 Structural evolution of the shoot apical meristem 72
4.4. Developmental pattern in shoot ontogeny 76
4.4.1 Gametophyte development 77
4.5 Development of specialised tissues in Rhynia gwynne-vaughanii 78
4.5.1 Stomata 78
4.5.2 Rhizoids 79
4.5.3 Tracheids 80
Chapter 5
Conclusions, critique and future work
5.0 Conclusions and critique 95
5.1 SRXTM and the Rhynie chert 96
5.2 Rhynie chert and role in future work on early land plant evolution 97
Bibliography 99
Appendix 119
SRXTM Settings 126
Curriculum Vitae 129