Developmental and Structural Section
Bachelier, Julien , Friedman, William .
Embryology in Trithuria submersa (Hydatellaceae) and relationships between embryo, endosperm, and perisperm in early-diverging flowering plants.
The discovery that Hydatellaceae are members of Nymphaeales has led to an intense focus on the circumscription of theirbiological features. Despite their highly reduced vegetative and reproductive morphology, Hydatellaceae bear the unmistakable embryological signature of water lilies: the seeds are filled with a copious starch-rich genetically maternal perisperm that occupies most of the seed, and a very small biparental endosperm and embryo. We examined the development of the embryo, endosperm,and perisperm, from fertilization through germination in Trithuria submersa. We found that the embryo development and seed germination in T. submersa and other Nymphaeales are similar. The embryo in T. submersa initiates two cotyledons prior to seed maturity/dormancy and their tips remain in the seed in contact with the endosperm throughout germination. The endosperm persists as a single layer of cells and serves as the interface between the embryo and the perisperm for at least six weeks after germination. The perisperm of T. submersa contains both carbohydrates and proteins and functions as the main nutrient storage tissue. The endosperm does not accumulate carbohydrates, but rather proteins and aleurone grains, and functions as a transfer cell layer, as opposed to a storage tissue.In Nymphaeales, the multiple roles of a more typical angiosperm endosperm(nutrient acquisition, nutrient storage, nutrient mobilization and transfer to the embryo) are thus separated into two different tissues and genetic entities: a maternal nucellus (nutrient acquisition, nutrient storage, nutrient mobilization) and a highly reduced endosperm (nutrient transfer to the embryo).The presence of perisperms among several ancient lineages of angiosperms (e.g.,Nymphaeales, Piperales, Acoraceae, and possibly Trimeniaceae and Ceratophyllaceae) suggests that there may have been a modest degree of developmental and functional lability for the nutrient storage tissue (nucellus or endosperm) within seeds during the early evolution of flowering plants.
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1 - Arnold Arboretum Of Harvard University, Arnold Arboretum - Organismic And Evolutionary Biology, 1300 CENTRE STREET, BOSTON, MA, 02131, USA
2 - Arnold Arboretum of Harvard, 1300 Centre St, Boston, MA, 02131, USA
origin of angiosperms.
Presentation Type: Oral Paper:Papers for Sections
Location: Union D/Hyatt
Date: Monday, July 9th, 2012
Time: 3:15 PM