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Abstract Detail



Celebrating More Than Three Decades of Research in Nymphaeales: A Colloquium Honoring Ed Schneider

Osborn, Jeffrey M. [1], Taylor, Mackenzie L. [2].

The Pollen Life Cycle in Nymphaeales: From Microsporogenesis to Fertilization.

The pollen life cycle begins with microsporogenesis in the anther, encompasses microgametogenesis, pollination, pollen germination, and concludes with delivery of the sperm cell to the egg via the pollen tube. Understanding the pollen life cycle in early-diverging angiosperm lineages is essential for understanding patterns of pollen evolution and the role of pollen in angiosperm diversification. Among early-diverging angiosperms, Nymphaeales (water lilies) exhibit variation in reproductive traits and are an excellent system within which to study the functional correlations and evolution among pollen characters, pollination mechanisms, and post-pollination development. In this presentation, we will review the pollen life cycle—inclusive of the ontogenetic phase (within the anther), the dispersal phase (pollination), and the progamic phase (from germination to fertilization)—in Nymphaeales within a comparative, phylogenetic context. Nymphaeales exhibits diversity in key pollen characters, including dispersal unit size, ornamentation, aperture morphology, and tapetum type. Pollen grains of all Nymphaealean genera are tectate-columellate, exhibiting one of two distinct patterns of infratectal ultrastructure — a thick infratectal space with robust columellae or a thin infratectal space with thin columellae. All genera exhibit a lamellate endexine that becomes compressed in the proximal, but not distal wall. Nymphaeaceae also exhibits a membranous granular layer, which is a synapomorphy of the family. Variation in pollen characters indicates that significant potential for lability in pollen development was present in Nymphaeales at the time of its divergence from the rest of angiosperms. Nymphaealean genera employ a wide range of pollination mechanisms, including beetle, bee, fly, and wind pollination, as well as cleistogamy, and the mechanism is often correlated with key pollen and floral characters. Variation in carpel structure among water lilies, in turn, affects the timing of post-pollination development. Pollen tubes of Nymphaeales share several important traits, including rapid pollen germination, the ability to penetrate stigmatic tissue, and accelerated pollen tube growth rates relative to other basal angiosperms. These innovations in pollen development, therefore, likely preceded the divergence of Nymphaeales and allowed subsequent evolution in reproductive structures. This supports the hypothesis that innovations in male gametophyte development facilitated angiosperm diversification.


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1 - The College Of New Jersey, School Of Science, 2000 Pennington Road, P.O. Box 7718, Ewing, NJ, 08628-0718, USA
2 - Creighton University, Department Of Biology, 2500 California Plaza, Omaha, NE, 68178, USA

Keywords:
Nymphaeales
Nymphaeaceae
Cabombaceae
Hydatellaceae
pollen
ontogeny
Development
pollination
pollen tube
post-pollination development.

Presentation Type: Colloquium Presentations
Session: C3
Location: Salon 12/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:30 AM
Number: C3007
Abstract ID:761
Candidate for Awards:None


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