Stochastic dynamics in determining fertilization outcomes in plants: effect of gamete number and pollen tube travel path length.

Plants may enhance seed fitness by favoring fertilization by pollen grains with superior genetic qualities. Pistil traits, such as style length and stigmatic area, are thought to influence this selection, but the mechanisms remain unclear. The impact of stochastic factors on pollen germination time variations is also not fully understood. To investigate this, we simulated a biophysical model using the Monte Carlo method to study how gamete number and pollen tube travel path length affect pollen selection. Our results show that longer travel paths (style lengths) and greater pollen loads on the stigma increase the probability of genetically superior pollen fertilizing ovules. It is because longer styles and more pollen load suppress stochastic effects, promoting seed fitness by favoring superior pollen. We also identify a tradeoff between the benefits of increased path length or pollen load and the resource costs incurred.