Sorghum barrier did not decrease the maximum distance ofpollen flow on the whole . The maximum distance of pollenflow was different in eight directional transects. Compared to theopen site, the maximum distance of pollen flow in the Sorghum sitewas nearer at four directions (south, north, northeast and south-west), the same at west and southeast, and further at east andnorthwest . The furthermost distance of pollen flow was250 m at north and northeast directions in the open experiment,and 150 m at east and north directions in the Sorghum experiment. This partially coincided with the wind direction, northerlyand southwesterly wind, over the three days of pollen capture .
The speed of wind affected the distance of pollen flow. The max-imum distance at each direction was shorter on the first day thanon the late two days of pollen capture. The mean speed of windduring the three days was 0.45 m/s, 1.81 m/s and 1.05 m/s .
The number of transgenic pollen at collecting locationsdecreased against the distance from transgenic maize .Power model predicted that the maximum distance at which nopollen was 175 m in the open experiment using total observed val-ues, whereas it was 71 m when Sorghum barrier was introduced.Students’ t-test showed that the Sorghum barrier significantlydecreased predicted distances (P < 0.001). Linear model predictedthat the maximum distance at which no pollen was 464 and 226 min the open and Sorghum experiment respectively. The differenceof predicted distance between open and Sorghum experiments wasnot significant (Students’ t-test, P = 0.07). Diffslope showed that lin-ear regression lines were not different between open and Sorghumregression lines at each direction.