Search

Settlingvelocityofmaize(ZeamaysL.)pollenplaysanimportantroleinitsdispersaland,therefore,cross-pollination. Estimated probability density functions (PDFs) of settling velocity based on experimentalmeasurements show strong variation between early morning and noon. The variation is correlated tothe time-integrated vapor pressure deficit (VPDT) and reflects the drying of pollen grains. A model forthe decrease in germination rate of pollen grains exposed to atmospheric conditions suggests that thedecrease in settling velocity is accompanied by a decrease in pollen viability. A simple dispersion modelis used to illustrate the possible consequences of changes in settling velocity and germination rate forpollen dispersal and cross-pollination of maize. Results suggest that current models of pollen dispersalthat do not account for these changes overestimate cross-pollination rates.© 2011 Elsevier B.V. All rights reserved. 1. IntroductionQuantifying and predicting gene flow and rates of cross-pollination in maize (Zea mays L.) have been the focus of muchresearch in the past few decades. This information is important inthe development of strategies for gene flow management, whichare required to ensure maximum kernel set and high levels ofgeneticpurityinhybridseedproduction(Aylor,2003;FonsecaandWestgate, 2005) and to minimize risks associated with the spreadof genetically modified traits (Wolfenbarger and Phifer, 2000). Acomplete model of cross-pollination has to account for pollen pro-duction and release at the source, pollen entrainment into theturbulent atmosphere, pollen dispersion and deposition, pollenviability, competition with local pollen at the receptor plant, andfertilization (e.g., see Aylor et al., 2003). The entrainment, disper-sion and deposition processes are governed by the characteristicsof atmospheric turbulence and physical properties of pollen grainssuch as shape, size, density and surface characteristics (Chameckietal.,2007).Pollenpropertiesdeterminetheinertiaofpollengrainsand, therefore, their response to turbulent motion. Typically, dis-persion models neglect pollen inertia using its settling velocity instillfluidtorepresenttheeffectsofthepollenpropertiesondisper-sion (Jarosz et al., 2004; Dupont et al., 2006; Chamecki et al., 2009;Viner and Arritt, 2010). In this simplified modeling approach, the