Mary Claire McGlynn
Project Description
"The Pollen Tube Pathway in Victoria: Implications for Flower Evolution in Water Lilies (Nympheaceae)"
Victoria is a charismatic genus in the water lily family Nymphaeaceae. Victoria is unique among water lilies in that it exhibits flowers up to 50 cm in diameter, much larger than those of other Nymphaeaceae. One primary function of the flower is to facilitate the growth of a pollen tube from the stigmatic surface to the ovule, where it delivers the sperm to the egg. Changes in flower morphology, therefore, have consequences for the reproductive events critical for successful fertilization. In order to understand the evolutionary consequences of increased flower size in Victoria, we first characterized the pollen tube pathway and pollen tube development in both species of Victoria, Victoria amazonica and V. cruziana. We then compared the pollen tube pathway in Victoria to that of other Nymphaeaceae, particularly, Nymphaea and Nuphar. These comparative data will provide insight into how flower evolution in Nymphaeaceae has affected reproductive development. In Victoria, pollen germinated across the entire stigmatic surface (853 um2 in V. amazonica, 1013 um2 in V. cruziana). Pollen germination was slow compared to other Nymphaeaceae, reaching 40% germination at 8 hours after pollination compared to 90% within an hour in Nymphaea odorata. Following germination, Victoria pollen tubes grew laterally until they reached the zone of postgenital fusion, where they penetrated the stigmatic tissue and then grew down through the substigmatic transmitting tissue. The average shortest distance to the first ovule was 5.3 mm in V. amazonica and 4.5 mm in V. cruziana, compared to 2.0 mm in N. odorata. The time to ovule entry is longer in Victoria, due to both slower pollen tube growth rates and a longer pollen tube pathway.
Victoria is a charismatic genus in the water lily family Nymphaeaceae. Victoria is unique among water lilies in that it exhibits flowers up to 50 cm in diameter, much larger than those of other Nymphaeaceae. One primary function of the flower is to facilitate the growth of a pollen tube from the stigmatic surface to the ovule, where it delivers the sperm to the egg. Changes in flower morphology, therefore, have consequences for the reproductive events critical for successful fertilization. In order to understand the evolutionary consequences of increased flower size in Victoria, we first characterized the pollen tube pathway and pollen tube development in both species of Victoria, Victoria amazonica and V. cruziana. We then compared the pollen tube pathway in Victoria to that of other Nymphaeaceae, particularly, Nymphaea and Nuphar. These comparative data will provide insight into how flower evolution in Nymphaeaceae has affected reproductive development. In Victoria, pollen germinated across the entire stigmatic surface (853 um2 in V. amazonica, 1013 um2 in V. cruziana). Pollen germination was slow compared to other Nymphaeaceae, reaching 40% germination at 8 hours after pollination compared to 90% within an hour in Nymphaea odorata. Following germination, Victoria pollen tubes grew laterally until they reached the zone of postgenital fusion, where they penetrated the stigmatic tissue and then grew down through the substigmatic transmitting tissue. The average shortest distance to the first ovule was 5.3 mm in V. amazonica and 4.5 mm in V. cruziana, compared to 2.0 mm in N. odorata. The time to ovule entry is longer in Victoria, due to both slower pollen tube growth rates and a longer pollen tube pathway.
Presentations and Published Abstracts
2014 Creighton Biology Department Research Colloquium
2015 Nebraska Academy of Sciences Creighton Biology Department Research Colloquium Creighton University Research Day |
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