Variations in Maize Pollen Emission and Deposition in Relation to Microclimate

Abstract

ABSTRACT. The co-existence of genetically modified (GM) crops with conventional crops has become a subject of debate and inquiry. Maize (Zea mays L.) is one of the most cultivated crop plants in the world and there is a need to assess the risks of cross-pollination. Concentration and deposition rate downwind from different-sized maize crops were measured during three flowering seasons, together with micrometeorological conditions in the surrounding environment. Pollen release started once the air vapour pressure deficit (VPD) increases above 0.2 to 0.5 kPa. Moreover, the dynamics of release was correlated with the dynamics of VPD surrounding the tassels. Horizontal deposition appeared to follow a power law over short distance downwind from the source, and the dispersal distance increased with the source canopy height, and the roughness length of the downwind canopy. This work also provides a data set containing both pollen measurements and contrasting weather conditions to validate dispersal models and further investigate maize pollen dispersal processes.

Scientific Opinion on an application from Pioneer Hi‐Bred International and Dow AgroSciences LLC (EFSA‐GMO‐NL‐2005‐23) for placing on the market of genetically modified maize 59122 for food and feed uses, import, processing and cultivation under Regulation (EC) No 1829/2003

“…Owing to their characteristics, maize pollen grains settle to the ground rapidly and have usually a short flight range (Jarosz et al, 2005). Approximately 95-99 % of the released pollen is deposited within about 50 m from the source.…”

Applications (EFSA‐GMO‐RX‐MON810) for renewal of authorisation for the continued marketing of (1) existing food and food ingredients produced from genetically modified insect resistant maize MON810; (2) feed consisting of and/or containing maize MON810, including the use of seed for cultivation; and of (3) food and feed additives, and feed materials produced from maize MON810, all under Regulation (EC) No 1829/2003 from Monsanto

“…Due to their characteristics, maize pollen grains settle to the ground rapidly (Aylor et al, 2003) and have usually a short flight range (Jarosz et al, 2005). Although vertical wind movements or gusts during pollen shedding can lift pollen up high in the atmosphere and distribute it over significant distances, concentrations of viable pollen considerably decrease with height (Aylor et al, 2006) and distance (Jarosz et al, 2005) from the source.…”

“…Due to their characteristics, maize pollen grains settle to the ground rapidly (Aylor et al, 2003) and have usually a short flight range (Jarosz et al, 2005). Although vertical wind movements or gusts during pollen shedding can lift pollen up high in the atmosphere and distribute it over significant distances, concentrations of viable pollen considerably decrease with height (Aylor et al, 2006) and distance (Jarosz et al, 2005) from the source. Hence, low levels of cross-pollination can occur over longer distances under suitable climatic conditions (Bannert and Stamp, 2007;Delage et al, 2007), but most cross-pollination events occur within 50 m of the pollen source (reviewed by Eastham and Sweet, 2002;Devos et al, 2005Devos et al, , 2009bvan de Wiel and Lotz, 2006;Hüsken et al, 2007;Sanvido et al, 2008).…”

Three-dimensional prediction of maize pollen dispersal and cross-pollination, and the effects of windbreaks

“…To determine the diurnal variation, we invoked the time derivative of the air temperature. The pollen emission rate of maize increases rapidly after sunrise, and it decreases gradually after late morning (Jarosz et al, 2005;Kawashima et al, 2004Kawashima et al, , 2007. As shown in Kawashima et al (2004), the pollen emission rate from maize tassels is associated with Prediction of maize pollen dispersal the temporal variation in the air temperature.…”