Data from: Using quantum dots as pollen labels to track the fates of individual pollen grains

1. Despite a long history of significant advances in understanding natural
selection and evolution, the field of plant reproductive biology has
largely studied plant mating without directly tracking pollen movement due
to a lack of suitable pollen-tracking methods. 2. Here, we develop and
test a novel pollen-tracking technique using quantum dots as pollen-grain
labels. Quantum dots are semiconductor nanocrystals that are so small,
they behave like atoms. When exposed to UV light, they emit extremely
bright light in both visible and infrared wavelengths We tested the
suitability of non-toxic CuInSexS2-x/ZnS (core/shell) quantum dots with
oleic acid ligands as pollen-grain labels.Using a micropipette, we
dispensed quantum dots dissolved in hexane in minute volumes (0.15–0.5 µl)
directly onto dehisced anthers of four different plant species from four
different families [Wachendorfia paniculata (Haemodoraceae), Sparaxis
villosa (Iridaceae), Arctotheca calendula (Asteraceae), Oxalis purpurea
(Oxalidaceae)]. 3. After application, the hexane solvent evaporated
immediately, leaving behind quantum dots that remained attached to pollen
grains of the four different plant species even after agitation in a polar
solvent. This suggests a lipophilic interaction between oleic-acid ligands
on quantum dots, and pollenkitt surrounding pollen grains. We also showed
that most pollen grains within anthers of the same four plant species were
labelled with quantum dots after applying a volume of quantum-dot solution
sufficient to cover an individual anther. To test whether quantum-dot
pollen-labels influenced pollen transport, we conducted pollen transfer
trials (one donor, ten sequential recipients) on S. villosa using
captively-reared honey bees to ensure bees were free of external pollen
prior to experiments. We found no difference in pollen transport to
recipients from donor flowers with labelled or unlabelled pollen grains.
4. We demonstrate that quantum dots can be used as pollen labels allowing
subsequent tracking of pollen fates. This method is relatively inexpensive
(<$500 for equipment and ca. $0.02 per labelled anther thereafter)
and can be simply and directly applied to anthers of most flowers in the
lab and field. The ability to track pollen grain movement in situ, may
help to address an historically neglected aspect of plant reproductive
ecology and evolution.