Abstract Detail

Developmental and Structural Section

Losada, Juan M. [1], Bachelier, Julien [2], Friedman, William [1].

Seed development in Austrobaileya scandens, an angiosperm liana endemic to the Australian tropical rainforest.

Ever since the first collection of Austrobaileya scandens in 1929 in the tropical forest of Queensland (Australia), the ontogeny of the seeds of this monotypic angiosperm genus has remained understudied. This is partly a result of the paucity of reproductive individuals in greenhouse and botanical garden collections, the need to climb (up to 40 feet) to acquire reproductive materials in the field, and the year-long interval between flowering and fruit dehiscence. Mature fallen fruits are eagerly eaten by cassowaries, so wild seeds are difficult to find before seedling emergence. Nevertheless, we have surmounted these obstacles. Following double fertilization, starch first accumulates in the nucellus, similar to what occurs in plants where a perisperm is the predominant tissues for storage of embryo-nourishing reserves. However, this transient phase of modest starch accumulation in the nucellus is quickly followed by a major expansion of the (ab initio cellular) endosperm. By the time the globular stage of embryo development has been reached, the endosperm occupies most of the seed volume but is largely comprised of vacuolate cells. At maturity, seeds of A. scandens contain a massive ruminate starchy diploid endosperm, a tiny embryo with two differentiated cotyledon primordia and a large hypocotyl. Following abscission of the fruit, the growing embryo is fed by the gradually obliterated starchy endosperm. The embryo hypocotyl enlarges and a large shoot apical meristem becomes apparent. Several leaves also are formed during the twelve months between dispersal of the seed and the emergence of the seedling primary root. Our work clearly demonstrates that Austrobaileya does not form a perisperm - nor do any other members of the Austrobaileyales studied to date. It is however intriguing to note that like many other members of ancient angiosperm lineages, the nucellus in Austrobaileya has the potential to store modest amounts of starch, suggesting that this tissue may broadly have played a critical role in the acquisition and (at least transient) storage of carbohydrates during the earliest phases of flowering plant evolution. Thus, the homoplasious origins of an embryo-nourishing perisperm (nucellus) in ancient angiosperm lineages Nymphaeales and the clade Saururaceae + Piperaceae may not be entirely surprising.

1 - Harvard University, Arnold Arboretum, Organismic and Evolutionary Biology, 1300 Centre Street, Boston, MA, 02131, USA
2 - State University of New York – SUNY Oswego, 30 Centennial Drive, Oswego, NY, 13126, United States

Keywords:
Austrobaileya scandens
Endosperm
Nucellus
Perisperm
seed
Seed germination.

Presentation Type: Oral Paper:Papers for Sections
Session: 69
Location: Salon 11/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 1:30 PM
Number: 69001
Abstract ID:1061
Candidate for Awards:None