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Abstract Detail



Developmental and Structural Section

Taylor, Mackenzie L. [1], Cooper, Ranessa L. [2], Schneider, Edward L. [3], Osborn, Jeffrey M. [4].

Pollen Structure and Development in Nymphaeales (Water Lilies): Insights into Character Evolution in an Ancient Angiosperm Lineage.

Nymphaeales, or water lilies, is an early-divergent angiosperm lineage that comprises three families (Cabombaceae, Hydatellaceae, Nymphaeaceae) with eight-to-nine genera and <100 aquatic species. Despite the limited number of taxa, there is great variation in morphological and ecological traits within the lineage. Consequently, Nymphaeales are particularly well-suited for studies of the evolution of reproductive traits, including pollen characters, in early angiosperm lineages. Mature pollen characters for all water lily genera and developmental characters for select taxa will be described and traits such as pollen size, exine ultrastructure, aperture morphology, and tapetum type will be discussed. Pollen grains are monosulcate in Cabombaceae, Hydatellaceae, and in Nuphar, whereas all other Nymphaeaceae have a ring-like aperture. The exine is tectate-columellate in all water lilies, but Barclaya, Brasenia, Cabomba, and Trithuria have a thick infratectum and robust columellae, whereas those in ‘core’ Nymphaeaceae exhibit a thin infratectum and narrower columellae. Cabomba and some genera of Nymphaeaceae have exine microchannels that are first apparent in the free microspore stage, concurrent with tapetum disassociation. Pollen grains of two genera exhibit major sculptural elements: supratectal rods in Cabomba and spines in Nuphar. The spines of Nuphar differ in ultrastructure and have an earlier ontogenetic origin than the sculptural rods of Cabomba. Tapetum ontogeny and structure also varies within water lilies, with secretory, invasive, and transitional types all present. This indicates that tapetal development is more labile in basal angiosperms than previously thought and that this lability was likely present early in angiosperm history. Nymphaeales exhibit variation in carpel structure and a wide range of pollination mechanisms, including beetle, bee, fly, and wind pollination, as well as cleistogamy. Thus, water lilies are an excellent system within which to study the functional correlations and evolution among pollen characters, pollination mechanisms, and post-pollination development. In particular, these will be discussed for dispersal unit size, exine ultrastructure, and pollination or post-pollination biology.  


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1 - Creighton University, Department Of Biology, 2500 California Plaza, Omaha, NE, 68178, USA
2 - HILLSDALE COLLEGE, 33 E COLLEGE ST, HILLSDALE, MI, 49242, USA
3 - University of Minnesota, Twin Cities, and The Landscape Arboretum, Department of Horticultural Sciences, 3675 Arboretum Drive, Chaska, MN, 55318, USA
4 - The College Of New Jersey, School Of Science, 2000 Pennington Road, P.O. Box 7718, Ewing, NJ, 08628-0718, USA

Keywords:
exine ultrastructure
Cabombaceae
Character evolution
Hydatellaceae
Nymphaeaceae
pollen
Pollen development
pollination
tapetum.

Presentation Type: Oral Paper:Papers for Sections
Session: 25
Location: Pines North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 11:15 AM
Number: 25005
Abstract ID:375
Candidate for Awards:None


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