Spines, microspines and electric fields: A new look at the possible significance of sculpture in pollen of basal and derived Asteraceae

Abstract

Effective adherence of pollen grains on the surface of the stigma is a crucial condition for tube germination and subsequent fertilization of ovules. We provide evidence, through computer simulations, that echinate and microechinate sculpture of pollen in Asteraceae could play an important role in that process. We show that electrostatic interaction increases in grains with few ornamental elements (echinate pollen typical of derived lineages) when compared with grains that have a large number of ornamental elements (microechinate pollen typical of basal lineages). We also show that grains of smaller size are more significantly affected by the electrostatic force. Although experimental studies are necessary to ascertain the real effect of electrostatic forces on pollen capture by the stigma in Asteraceae, our contribution suggests that these forces might have great biophysical significance in the evolution of the family.