Developmental and Structural Section
Holloway, Samuel J. , Friedman, William E. .
Embryological features of Tofieldia glutinosa and their bearing on the early diversification of monocotyledonous plants.
Although much is known about the vegetative traits associated with the origin of monocotyledonous plants, far less attention has been paid to the origin and early diversification of defining reproductive features of ancient monocot lineages. We studied the embryology of Tofieldia glutinosa, a member of an early divergent monocot clade (Tofieldiaceae), and compared aspects of its development to that of other early divergent monocot clades in order to gain insight into defining reproductive features of early monocots. Development of the female gametophyte in T. glutinosa is of a modified Polygonum-type. At maturity the female gametophyte is seven-celled and eleven-nucleate with a standard three-celled egg apparatus, a binucleate central cell (where ultimately, the two polar nuclei will fuse into a diploid secondary nucleus) and three binucleate antipodal cells. The antipodal nuclei persist past fertilization, and the process of double fertilization yields a zygote and triploid primary endosperm cell, as is characteristic of plants with Polygonum-type female gametophytes. Endosperm development is helobial, and free-nuclear proliferation proceeds at equal rates in both the micropylar and chalazal endosperm chambers. Our analysis suggests that the shared common ancestor of monocots possessed persistent and proliferating antipodals similar to those found in T. glutinosa and members of other early-divergent monocot clades (e.g. Acorus and members of the Araceae). In addition, helobial endosperm among monocots evolved once in the common ancestor of all monocots excluding Acorus and is homoplasious with the helobial endosperms found among some water lilies and eudicots.
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1 - University of Colorado, Ecology and Evolutionary Biology, Boulder, CO, 80309, United States
2 - University of Colorado, Ecology and Evolutionary Biology, Boulder, CO, 80309, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 2:15 PM