Ephedra pollination and other gnetalean oddities
Stevenson, Dennis .
Embryological Oddities in Gnetales.
Most of the oddities occur in megagametophyte development,fertilization and embryogenesis. While much of the development of the megagametophyte and earlier stages of the embryo follow the pattern of other gymnosperms, the Gnetales show very unusual departures in the later stages. There is no alveolar stage in the megagametophyte of Gnetum and Welwitschia, yet there is the cellularization that starts at the chalazal end and results in multinucleate cells and polyploid cells where the nuclei fuse. There are no archegonia produced in these genera and the latter has the peculiar formation of gametophytic tubes. Both genera produce embryonic tubes that give rise to multiple embryos are unique in plants.Ephedra has odd production of multiple embryos forming from each of the free nuclei of the free nuclear stage of embryogenesis. There is a very good body of descriptive literature, but a paucity of repeated observations. Thus, we really do not know if these oddities are occasional teratisms or fixed. If fixed, then some of these processes could be studied and compared easily to Ginkgo, cycads and conifers as well as Selaginella via genomic approaches. Examples of this will be explored.
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1 - THE NY BOTANICAL GARDEN, 2900 SOUTHERN BLVD, BRONX, NY, 10458-5126, USA, 718/817-8632
Presentation Type: Symposium or Colloquium Presentation
Location: Delaware A/Hyatt
Date: Monday, July 9th, 2012
Time: 10:30 AM