Dissertation committee:
Κώστας Α. Θάνος Καθηγητής (Επιβλέπων), Κυριάκος Γεωργίου Αναπληρωτής Καθηγητής, Γρηγόρης Ιατρού Καθηγητής
Summary:
The aim of this dissertation is to determine the germination characteristics in
a large number of representative species of the Campanulaceae family from
across its entire geographical distribution. The thesis focuses on: 1)
germination in a range of constant (throughout) temperatures, alternating
(diurnally) or simulating natural ones, 2) induction and release of
thermodormancy, 3) light mediation, examined under diurnal white light / dark
conditions (control in continuous darkness), 4) phytochrome action, 5)
substitution of light requirement, 6) induction, kinetics and release of
skotodormancy, 7) germination in the field and formation of a soil seed bank,
8) analysis of results based on distribution, climatic conditions and habitat
type, 9) afterripening, 10) bradychory and 11) embryo length increase before
radical protrusion.
In total, 187 seed samples were studied (149 taxa, 144 species, 27 genera, 3
subfamilies). Small seed mass is a noteworthy trait of the family; the embryo
usually occupies less than half of the interior of the seed. For the majority
of the studied taxa successful germination was achieved at least at one of the
temperatures tested. The temperature range and the favorable germination
conditions are correlated with the climatic type and the altitude of the seed
collection sites. Light requirement for germination, observed in virtually all
taxa examined, constitutes a collective characteristic of the family, while
alternating temperatures can fully or partially substitute for light
requirement in certain taxa, especially for larger-seeded species.
Skotodormancy, from dark incubation, is induced in a large number of species.
Campanulaceae seeds form permanent soil seed banks primarily due to their small
size and light-requiremnet. Skotodormancy induced from dark incubation in the
soil, can consequently fine-tune the optimal timing of seed germination in the
field.
Keywords:
Germination, Campanulaceae, Photorequirement, Skotodormancy
