Physics explains how pollen gets its stunning diversity of shapes
The varied patterns can all be explained by a process called phase separation
Pollen grains sport a variety of snazzy shapes, from golf ball–like divots to prickly knobs or swirls that evoke a peppermint candy. But these myriad patterns may all be due to one simple trick of physics, scientists report in the Feb. 7 Cell.
That trick: phase separation, in which a mixture naturally breaks up into separate parts, like cream floating to the top of milk (SN: 7/21/18, p. 14). As pollen develops in a flowering plant, a material called primexine is deposited at the grain’s surface, inside a temporary cell wall. Formed from a mixture of materials including cellulose and pectin — the stuff that makes jam set — the primexine clumps together in denser and less dense regions “like bad gravy,” says biophysicist Alison Sweeney of the University of Pennsylvania.