Modelling diurnal and seasonal patterns of maize pollen emission in relation to meteorological factors

Modelling the risk of cross-pollination between maize crops can help to define efficient isolation methods to reduce the risk of gene flow between these crops. However, the use of such models over the pollen emission season is limited by poor estimations of pollen emission. In this study, we present a model that predicts hourly pollen emission fluxes over the pollen season and that accounts for effects of both meteorological conditions and crop variety. It consists of two sub-models that predict: (i) the seasonal pattern on a daily basis and (ii) the normalized diurnal pattern on an hourly basis. To assess the variability of pollen emission, ten field experiments were carried out in July and August over four years using three crop varieties. The model was built from (i) a parameterisation of the measured diurnal and seasonal patterns of pollen emission followed by (ii) a quantification of the relationships between parameter values and meteorological conditions. Total production of pollen was fairly constant for a given variety over years and sowing dates, while patterns of emission varied with meteorological conditions. The pollen emission season was longer when temperature was low and humidity was high. In most cases, the diurnal pattern was unimodal: the onset and the peak of emission were delayed when relative humidity was high or wind speed was low. In some cases, a second peak of emission occurred during the afternoon. This was observed more frequently when temperatures were high.