Preliminary Research On Characteristics Of Maize Pollen Dry Deposition

The dry deposition velocity of pollen, which would impacts its effective diffusion distance, is one of the main research objects in the biology security assessment of transgenic maize. In order to provide the foundation and scientific basis for the establishment of pollen diffuse model and predicting the pollen diffusion concentration, we should make a fully understanding the distribution and evaluate the deposition velocity of pollen accurately.The characteristic of microclimatology in the ground layer was analyzed on the basis of the microclimatology observation in the maize field. The regular pattern of maize pollen dispersal was described through the observation of pollen dispersal. The temporal and spatial distributions of pollen dry deposition flux in and out of the source were analyzed through the experiment of maize pollen dry deposition test. At last, the dry deposition velocity of maize pollen was calculated, and the Resistance Model used to simulate the deposition velocity of maize pollen was modified and validated based on the test data.The main conclusions are as following:(1). The pollen dispersal had a feature of low-high-low during the whole period. The shape of the curve reflects the assumption that the flowering strength of the cornfield is approximated by a parabolic curve. The daily pollen dispersal also has a characteristic of low-high-low in the peak days. The peak, medium and low time of each day appear in 7:00～9:00,9:00～12:00,15:00～6:00 in next day.(2). On the horizontal orientation, the pollen dry deposition flux was impacted by the wind direction and speed. The deposition flux exponential decreased along with the increasing distance from the source, most pollen deposited in 0～10m distance, and the unstable stratification appeared in 6～16m, and a "long tail" phenomenon was appeared sometimes. In addition, different directions have different pollen deposition flux. The deposition flux in the prevailing wind direction zone was generally higher than that in the crosswind with a higher risk of gene flow. On the vertical orientation, the differences of deposition fluxes at different height were significantly too, and the coefficient of variation ranged between 50 to 100.(3). According to the Dry Deposition Flux Model, the dry deposition flux of maize pollen was simulated using the observational data of the dry deposition flux at different distance from the pollen resource and the responding microclimatology conditions. Because of the instability of wind direction and the variedness of wind speed will change the pollen deposition flux, a simulation functional model would be used to predict the amount of pollen deposition.(4). Values of deposition velocity ranged between 0.5 and 1.4 m/s, and had a feature of low-high-low. Turbulence on the transition enhanced the pollen deposition evidently, and made bigger deposition velocities. With the relative humidity increasing, maize pollen deposition velocity presented a linear increase. Compared the observed values of the dry deposition velocity to the simulated values of that simulates by the "Deposition Model", there was a very good linear correlation between them, but with significant differences. The mathematic model for calculating regional dry deposition velocity could not be used to simulate the deposition velocity of maize pollen accurately.