The pollen dispersal characteristics of Hemarthria compressa

Abstract: The daily changes of pollen density and the dispersal patterns of Hemarthria compressa were measured by air pollen trapping method. The results showed that there were two peaks of flowering time during 6:00-8:00 and 15:30-19:00, and the highest amounts of pollen grains collected was during 16:00-18:00. We found that wind speed affected the distances of the pollen grains distributions. The pollen grains distributed within the circle of 5 m from the pollen grain originate place,when the wind speed was lower thatn 1 km/h (0 grade) or between 1-5 km/h (1 grade), and within the circle 21 m when the wind speed was between 12-19 km/h (3 grade). The plant stands comes from the same mother plant in the areas of pollen distributed, so the crosspollination in the same plant stand was common. The dilemma between pollen distribution pattern and cross pollination reproduction system was one of the reason of low seed set.