DeVol, Joe , Rebert, April , Greer, Gary , Dietrich, Margaret .
Effects of Exogenous Cytokinin Application on Morphological Development of Gametophytes of the Fern Osmunda regalis .
Most fern gametophytes pass through a series of distinctive stages ending with a heart-shaped morphology. Transition from a paddle to a heart-shaped morphology is characterized by the formation of a notch at its anterior end where the apical meristem resides. Archegonia are produced only after attaining a notch-meristem. We used cytokinin, a plant hormone known to stimulate cell division, to determine its effects on morphological development and gender expression of fern gametophytes. We predicted that application of exogenous cytokinin would accelerate notch formation and the attainment of a spherical profile, because attainment of a notch-meristem has been associated with high rates of cell division. To test this hypothesis, spores of Osmunda regalis were sown onto plates of nutrient agar containing 0, 0.001 µM, 0.1 µM, 10 µM cytokinin concentrations. After five weeks of growth gametophytes were mounted as semi-permanent slides, gametangia counted and whole gametophyte images digitally captured. Gametophyte size, sphericity, notch-depth: gametophyte length ratio were digitally measured. Gametophytes grown on the 10 µM cytokinin treatment were significantly smaller, produced fewer archegonia (after correcting for developmental status by dividing by notch-depth: gametophyte length ratio) and produced more antheridia (after correcting for size) as compared to all lesser concentrations, with the exception of the number of antheridia produced in the 0.1?M treatment. Antheridia were produced only in multispore cultures possessing some cordate individuals, indicating O. regalis, a basal filicalean fern, possesses an antheridiogen system. Our results indicate that cytokinin is not involved in notch formation and directly or indirectly stimulates antheridia production.
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1 - Grand Valley State University, Biology Department, 1 Campus Drive, Allendale, Michigan, 49401, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM