Developmental and Structural Section
Taylor, Mackenzie L. , Williams, Joseph H. .
Pollination to Fertilization Biology of Trithuria (Hydatellaceae).
Trithuria, the sole genus in Hydatellaceae, comprises 12 species of minute aquatic plants distributed primarily in Australia and New Zealand. Molecular evidence indicates Hydatellaceae is sister to Nymphaeales (water lilies) and that this lineage diverged from the basal-most or next most basal node of the angiosperm phylogenetic tree. Very little is known about the reproductive ecology and post-pollination biology of Trithuria. Both dioecy and monoecy occur in Trithuria, but several species have bisexual reproductive units and may exhibit selfing. Pollination is hypothesized to occur via wind or water. In order to investigate pollination biology and breeding system in Trithuria, we carried out field studies in bisexual Trithuria submersa near Manjimup, Western Australia. We characterized reproductive events, including anther dehiscence, stigma receptivity, pollen reception and germination, as well as pollen production and natural pollen loads. Our data indicate that T. submersa exhibits wind-pollination, rather that water-pollination. In this species natural out-cross pollen loads were low, the period of stigma receptivity was long, and delayed selfing occurred. The strategy of having a long period of stigma receptivity followed by automatic selfing as a mechanism for reproductive assurance is in contrast to the strategy exhibited by Brasenia schreberi, another wind-pollinated taxon in Nymphaeales. Brasenia has larger pollen loads, an extremely short period of stigma receptivity that is highly synchronized with anther dehiscence at the population level, a much larger stigmatic surface, and no potential for selfing. In both taxa, anther dehiscence depends on flower emergence and the subsequent drying of anthers. However, Trithuria submersa inhabits an environment in which ‘flower’ emergence is contingent upon evaporation of ephemeral lakes and wetlands, whereas Brasenia inhabits lakes with stable water levels and flower emergence is a predictable consequence of developmental timing.
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1 - University of Tennessee, Department of Ecology and Evolutionary Biology, 569 Dabney Hall, Knoxville, Tennessee, 37996, USA
2 - University of Tennessee, Department of Ecology and Evolutionary Biology, 442 Hesler Biology, Knoxville, Tennesee, 37996, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Wasatch B/Cliff Lodge - Level C
Date: Tuesday, July 28th, 2009
Time: 2:45 PM