Modeling the transient electric field produced by a charged pollen cloud entering a flower

A fuller understanding of the transient electrical phenomena that occur during a charged-pollen transfer process is essential to the successful development of an effective electrostatic pollination system for greenhouse crops. This paper describes a 3D model for computing the electric field produced by a pollen cloud having unipolar space charge as it approaches and enters a flower. The 3D finite element model is coupled with the dynamic space charge and the resulting transient boundary potential on the flower surface. These transients were based upon charge relaxation of individual flower components calculated using experimental values for component conductivity and permittivity. With an initial space charge density of 25 pC/m/sup 3/, a model squash flower and charged-pollen system was analyzed. For instantaneous introduction of the space charge, results show that the initial electric field is 38% of the maximum electric field which subsequently occurs as displacement currents return the flower components to earth potential. The calculated electric field at the location immediately above the flower stigma is found to be approximately 3-fold greater than field values above the petal edges. The demonstrated focusing of the electric field onto the flower stigma is of considerable biological significance since this is the desired target for pollen deposition. The results provide additional important information needed for prediction of the movement of charged pollen particles within flowers and are useful in specifying design criteria for engineering an effective electrostatic pollen deposition process.