Ontogenetic studies on the determination of the apical meristem in racemose inflorescences [Elektronische Ressource] / Kester Bull-Hereñu

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2010
• Nombre de lectures: 15
• Langue: English
• Poids de l'ouvrage: 11 Mo

Extrait

Ontogenetic studies on the determination of the apical meristem in
racemose inflorescences
D i s s e r t a t i o n
Zur Erlangung des Grades
Doktor der Naturwissenschaften
Am Fachbereich Biologie
Der Johannes Gutenberg-Universität Mainz
Kester Bull-Hereñu
geb. am 19.07.1979 in Santiago
Mainz, 2010CONTENTS
SUMMARY OF THE THESIS............................................................................................ 1
ZUSAMMENFASSUNG.................................................................................................. 2
1 GENERAL INTRODUCTION......................................................................................... 3
1.1 Historical treatment of the terminal flower production in inflorescences....... 3
1.2 Structural understanding of the TF................................................................... 4
1.3 Parallel evolution of the character states referring the TF............................... 5
1.4 Matter of the thesis.......................................................................................... 6
2 DEVELOPMENTAL CONDITIONS FOR TERMINAL FLOWER PRODUCTION IN
APIOID UMBELLETS...................................................................................................... 7
2.1 Introduction...................................................................................................... 7
2.2 Materials and Methods..................................................................................... 9
2.2.1 Plant material..................................................................................... 9
2.2.2 Measurements................................................................................... 9
2.2.3 Statistical analysis.............................................................................. 10
2.3 Results.............................................................................................................. 12
2.3.1 Ontogeny of the umbellets................................................................ 12
2.3.2 Measurements................................................................................... 12
2.4 Discussion ......................................................................................................... 17
2.5 Summary........................................................................................................... 19
2.6 Appendix........................................................................................................... 20
3 OPEN AND CLOSED INFLORESCENCES: MORE THAN SIMPLE OPPOSITES.................... 22
3.1 Introduction...................................................................................................... 22
3.2 A determinate inflorescence meristem does not imply a terminal flower....... 22
3.3 Histology of IMs support two kinds of open inflorescences............................. 26
3.4 What represses terminal flower formation in MC inflorescences?.................. 30
3.5 Concluding remarks.......................................................................................... 34
3.6 Summary........................................................................................................... 34
4 ONTOGENETIC COURSE AND SPATIAL CONSTRAINTS IN THE APPEARANCE
AND DISAPPEARANCE OF THE TERMINAL FLOWER IN INFLORESCENCES....................... 36
4.1 Introduction...................................................................................................... 36
4.2 Material and Methods...................................................................................... 38
4.2.1 Plant material..................................................................................... 38
4.2.2 Measurements................................................................................... 41
4.2.3 Parameter calculation........................................................................ 43
4.2.4 Inflorescence bud age........................................................................ 45
4.2.5 Statistical analysis.............................................................................. 46
4.3 Results.............................................................................................................. 46
4.3.1 Inflorescence ontogeny by systematic groups .................................. 46
4.3.1.1 Berberidaceae..................................................................... 46
4.3.1.2 Papaveraceae-Fumarioideae .............................................. 49
4.3.1.3 Rosaceae............................................................................. 574.3.1.4 Campanulaceae....................................................................62
4.3.2 Comparison between closed and open inflorescences...................... 68
4.3.2.1 T test for the initial and final states of the meristems.........68
4.3.2.2 Correlation analysis............................................................. 68
4.4 Discussion..........................................................................................................72
4.4.1 Spatial and shape requisites of the inflorescence meristem
(IM) for terminal flower (TF) production.................................................... 72
4.4.2 One common ontogeny for closed inflorescence and at
least two ontogenies in open inflorescences............................................. 73
4.4.3 Histophysiological correlates............................................................. 77
4.4.4 Concluding remarks........................................................................... 79
4.5 Summary........................................................................................................... 80
4.6 Appendix........................................................................................................... 82
5 GENERAL CONCLUSIONS........................................................................................... 92
6 REFERENCES.............................................................................................................. 94
ACKNOWLEDGEMENTS...............................................................................................105SUMMARY
SUMMARY OF THE THESIS
This thesis presents a comparative developmental study of inflorescences and focuses on
the production of the terminal flower (TF). Morphometric attributes of inflorescence
meristems (IM) were obtained throughout the ontogeny of inflorescence buds with the aim
of describing possible spatial constraints that could explain the failure in developing the TF.
The study exposes the inflorescence ontogeny of 20 species from five families of the
Eudicots (Berberidaceae, Papaveraceae-Fumarioideae, Rosaceae, Campanulaceae and
Apiaceae) in which 745 buds of open (i.e. without TF) and closed (i.e. with TF) inflorescences
were observed under the scanning electron microscope.
The study shows that TFs appear on IMs which are 2,75 (se = 0,38) times larger than the
youngest lateral reproductive primordium. The shape of these IMs is characterized by a leaf
arc (phyllotactic attribute) of 91,84° (se = 7,32) and a meristematic elevation of 27,93° (se =
5,42). IMs of open inflorescences show a significant lower relative surface, averaging 1,09
(se=0,26) times the youngest primordium size, which suggests their incapacity for producing
TFs. The relative lower size of open IMs is either a condition throughout the complete
ontogeny (‘open I’) or a result from the drastic reduction of the meristematic surface after
flower segregation (‘open II’).
It is concluded that a suitable bulge configuration of the IM is a prerequisite for TF
formation. Observations in the TF-facultative species Daucus carota support this view, as the
absence of the TF in certain umbellets is correlated with a reduction of their IM dimensions.
A review of literature regarding histological development of IMs and genetic regulation of
inflorescences suggests that in ‘open I’ inflorescences, the histological composition and
molecular activity at the tip of the IM could impede the TF differentiation. On the other side,
in ‘open II’ inflorescences, the small final IM bulge could represent a spatial constraint that
hinders the differentiation of the TF. The existence of two distinct kinds of ontogenies of
open inflorescences suggests two ways in which the loss of the TF could have occurred in the
course of evolution.
1ZUSAMMENFASSUNG
ZUSAMMENFASSUNG
Die Dissertation beinhaltet eine vergleichende Studie zur Entwicklung von Blütenständen,
wobei der Schwerpunkt auf der Bildung bzw. dem Fehlen von Endblüten (EB) liegt.
Morphometrische Veränderungen, die während der Ontogenie der Blütenstandsknospen am
Infloreszenzmeristem (IM) auftreten, wurden erstmals ermittelt und quantifiziert, um
eventuelle räumliche Zwänge, die das Ausfallen der EB erklären könnten, zu beschreiben.
Die Studie umfasst die Infloreszenzontogenie von 20 Arten aus fünf Familien der
Eudicotyledonae (Berberidaceae, Papaveraceae-Fumarioideae, Rosaceae, Campanulaceae
and Apiaceae) mit offenen (ohne EB) und geschlossenen (mit EB) Blütenständen. Sie basiert
auf der Analyse von 745 Infloreszenzknospen unter dem Rasterelektronmikroskop.
Die Ergebnisse zeigen, dass sich Endblüten nur an Infloreszenzmeristemen entwickeln, die
2,75 (se = 0,38) Mal so groß sind wie ihr jüngstes