Richard Rush, “Investigation of Primula meadia Pollen Germination Using Fluorescent Microscopy”
Mentor: Jeff Karron, Biological Sciences
Poster #138

Shooting star flowers are pollinated by bees that vibrate the flower at high velocity, causing the pollen to be released violently from the anthers onto the underside of the bee. Since most buzz pollinated flowers are pendent, foraging bees visiting flowers deposit pollen onto stigmas by forcing pollen between the stigmatic papillae. Recent scanning electron microscopy work has shown that the stigmatic papillae of shooting star differ markedly from most other flowering plants. The papillae of most plants are rod shaped, but the papillae of shooting star are mushroom shaped. I hypothesized that this unusual shape prevents self-pollen from pushing between the stigmatic papillae and successfully germinating and fertilizing ovules. To investigate this question, I used widefield and confocal fluorescence microscopy to elucidate whether pollen grains need to be inserted past the heads of the mushroom-like cells to germinate and pollinate the plant. I hand-pollinated plants and stained the stigmas to visualize pollen grains and determine their placement on the stigma. Germinating pollen grains are visualized by their pollen tubes which grow down the plant towards the ovules. If pollen needs to be inserted past the heads of the mushroom-shaped cells to germinate, the cell shape may be a strategy that evolved to limit self-pollination in buzz-pollinated plants.