Increased pollen viability resulting from transport to the upper boundary layer

Pollen viability has typically been measured using meteorological conditions at the Earth's surface. Some pollen grains, however, are lifted throughout the atmospheric boundary layer to heights where temperature and moisture differ markedly from near the surface. This transport may affect pollen viability because viability in maize is linked to its moisture content (Aylor, 2003).

We have used Large-Eddy Simulation to examine the effect of boundary layer transport on pollen viability. We simulated pollen dispersion and predicted pollen viability using surface measurements at the pollen source and using the atmospheric conditions a pollen grain experienced along its trajectory as it moved through the atmospheric boundary layer. Viability was predicted following Fonseca and Westgate (2005).

The two methods of predicting viability produced similar results for pollen grains deposited within a kilometer of their source, but surface temperature and humidity underpredicted pollen viability up to 20% for pollen that traveled several kilometers. The difference is attributed to the tendency for longer range transport to require lofting of pollen grains into the upper part of the atmospheric boundary layer, where cooler temperature and higher relative humidity are conducive to increased viability. Based on our results, viable pollen may be transported many more kilometers than previously estimated.

References:

Aylor, D.E., 2003. Rate of dehydration of corn (Zea mays L.) pollen in the air. J Exp Botany 54, 2307-2312.

Fonseca, A.E., Westgate, M.E., 2005. Relationship between desiccation and viability of maize pollen. Field Crops Res. 94, 114-125.