Pollen Viability and Longevity of Switchgrass (Panicum virgatum L.)

Pollen is essential for seed production and serves as the primary means of gene flow in outcrossing species like switchgrass (Panicum virgatum L.). There is a lack of information on basic pollen biology in switchgrass. This study investigated pollen viability, pollen longevity, and pollen size using different materials, including the tetraploid cultivar Alamo, the octoploid cultivar Cave-in-Rock, and transgenic Alamo plants. Pollen grains were collected from field-grown Alamo and Cave-in-Rock plants, and greenhouse-grown transgenics. Pollen size was in the range of 42.5 to 54.0 mu m; no significant difference was observed in average pollen size between transgenic and control plants. Increasing temperature and ultraviolet-B irradiation negatively affected pollen viability and longevity, while relative humidity had only limited impact. Weather conditions had a large impact on pollen longevity. Under sunny atmospheric conditions, pollen longevity of both cultivars decreased rapidly, with a half-life of <4.9 min and a complete loss of viability in 20 min. Under cloudy atmospheric conditions, the half-life of pollen was more than fivefold longer than under sunny conditions, and it took approximately 150 min to lose viability completely. No difference in pollen viability and longevity was found between transgenic and nontransgenic control plants.