Flowering habits and pollen dispersal in Pensacola Bahia grass, Paspalum notatum, Flugge

Counts were made on the number of florets flowering at hourly intervals on 20 panicles for three successive nights. Hourly pollen collections were made at panicle height and at ground level. Records were taken each hour on temperature, relative humidity, and average wind velocity. The major flowering peak in June occurred previous to midnight, depending upon the hour the optimum temperature was reached. Relative humidity and wind velocity had no apparent effect on flowering but did affect the rate at which dehiscence occurred. Pollen dispersal was measured by releasing a mixture of corn and pearl millet pollen and Lycopodium spores to determine the relative concentrations of pollen and spores at various distances down-wind. After 50 yards of isolation, further increases in distance resulted in very small decreases in pollen density. Pollen size had no apparent effect on dispersal. Pollen dispersal was measured by utilizing an albino genetic marker in Pensacola Bahia grass. Data were presented showing the percentage of albinos at various distances from a contamination source. It was concluded that 25 rods of isolation were sufficient for the production of seed of this grass for use by farmers for hay or pasture purposes but not for the production of foundation seed. Significant differences occurred between isolations but not beyond 25 rods. The amount of outcrossing at all distances may have been higher than under field conditions because of the relative sizes of the contamination area and the isolation blocks. The study of pollen dispersal by using genetic characters is probably the best means of determining isolation requirements. This method is hampered by the lack of satisfactory genetic markers. Markers which can be carried in a homozygous recessive condition are to be desired.