This is the top of a chemically cleared pistil from a thale-cress flower. You can see the stigma on top of the pistil in orange (1), with several round pollen grains stuck to it (2). The transparent ...

This is a single pollen grain (1) attached to the stigma (2) atop the central stalk of a morning ... which is located at the base of the pistil. Biology in the background Morning glories are flowering ...

The study described how a plant's floral tubes produce volatile compounds to sterilize their stigma, the part of the pistil that collects pollen, to protect against attack by pathogens.