Abstract Detail

Reproductive biology

Schoonderwoerd, Kristel [1], Friedman, William [1].

Prolonged zygotic dormancy in Franklinia alatamaha, a most unusual phenological pattern of seed development among angiosperms.

In 1794, plant collector William Bartram commented on the phenology of a natural population of Franklinia alatamaha (Theaceae) in Georgia when he wrote that he had seen plants “in perfect bloom, as well as bearing ripe fruit”. Today, Franklinia, a deciduous tree species, is extinct in the wild and receives much horticultural attention, but little is known about the timing of ovule and seed development in the process of the species’ lengthy fruit development. Anthesis and pollination of flowers take place in late summer and fall. Ovules were found to be mature before pollination and double fertilization occurs soon thereafter. Endosperm development progresses slowly for up to three months after fertilization, but is then brought to a standstill at the onset of winter. During winter dormancy, early developing seeds remain in the same developmental stage; they contain cellularized endosperm, but a yet undivided zygote. Over the course of the fall and winter months, growth of the fruit is minimal. At the start of the following growing season, endosperm development is reinitiated and the first proembryonic stages were observed. By mid-July, the dicotyledonous embryo occupies most of the space enclosed by the seed coat and mature seeds are exalbuminous. Full maturation of seeds is cotemporaneous with anthesis of this subsequent year. The timing of key ontogenetic events in Franklinia seeds is markedly different from all (but perhaps one) other angiosperm species with prolonged periods of time between pollination and seed maturation. In these other angiosperms, which include several members of Fagales, a scenario of delayed fertilization with intermittent pollen tube growth underlies the prolonged lapse of time between pollination and fruit growth. Thus, the short interval between pollination and fertilization, combined with a nearly seven-month dormancy of the resulting zygote (with minimal endosperm development) in Franklinia, is unique. Given the pronounced tropical and subtropical distribution of Theaceae, and the fact that Franklinia is the only member of its tribe that is deciduous, the fall flowering of Franklinia followed by extensive winter dormancy suggests a unique solution to developmental challenges and constraints associated with adaptation to prolonged periods of cool weather, along with a newly acquired deciduous habit.

1 - Harvard University, Arnold Arboretum, Organismic and Evolutionary Biology, 1300 Centre Street, Boston, MA, 02131, USA
2 - Harvard University, Arnold Arboretum, Organismic and Evolutionary Biology, 1300 Centre Street, Boston, MA, 02131, USA

Keywords:
Theaceae
embryogenesis
Dormancy
Seed Development
Franklinia.

Presentation Type: Oral Paper:Papers for Topics
Session: 2
Location: Salon 1/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 9:15 AM
Number: 2006
Abstract ID:1358
Candidate for Awards:None