Faivre, Amy , Weekley, Carl W. .
Low pollen germination and pollen tube growth in the rare endemic Florida ziziphus (Ziziphus celata).
Habitat loss and fragmentation have reduced Florida ziziphus (Ziziphus celata) to fewer than a dozen mostly uniclonal populations. In addition, this federally-endangered shrub has a gametophytic self-incompatibility system (GSI) which limits the availability of mates. Previous research has shown that even after hand-pollination of compatible genotypes, fruit set is low and fruits often abort or contain inviable seeds. Though flowers are retained on the plant for more than 10 days, pollen tubes can grow to the ovules within 48 hours of pollination. We hypothesized that pollen sterility, ineffective pollen tube growth, and post-zygotic failure contribute to sexual reproductive failure in Florida ziziphus. Approximately 400 flowers were hand-pollinated in January 2005 and 2006 with self pollen, pollen from incompatible donors, or pollen from compatible donors. To document pollen germination and tube growth, we used fluorescence microscopy to observe flowers stained with aniline blue. In 2005, only 41% of hand-pollinated flowers retained pollen grains on the stigma surface after staining; 86% did so in 2006. A small percentage of flowers appeared to have fungal growth on the stigma surface, especially those that were collected 10 days following hand-pollination. As expected for a GSI species, on average 23% of the self crosses and crosses between incompatible genotypes resulted in pollen tube inhibition in the style. Between 7% (2005) and 13% (2006) of hand-pollinated flowers had pollen tube growth continue to the ovules, including a few selfs and crosses between putatively incompatible genotypes. However, these results were isolated to two plants notable for their high rates of fruit set. Thus it appears that low levels of reproduction in Florida ziziphus are influenced by a number of factors including pollen sterility, fungal infestation, and ineffective pollen tube growth. Future research will involve dissections of aborted fruits to learn more about potential sources of post-zygotic failure.
Log in to add this item to your schedule
1 - Cedar Crest College, Department of Biological Sciences, 100 College Drive, Allentown, Pennsylvania, 18104, USA
2 - Archbold Biological Station, Plant Ecology Lab, P.O. Box 2057, Lake Placid, Florida, 33862, USA
Lake Wales Ridge
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM