DOI: 10.5061/dryad.mc72688
title: Data from: Using quantum dots as pollen labels to track the fates of individual pollen grains

description: 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
 (&lt;$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.
description: Proportion of pollen
 grains labelled with Qdots per speciesTo test whether quantum
 dots physically attach to pollen grains, we applied quantum-dot solutions
 to five different anthers from five different individuals for each of the
 four species we tested. Each line in this data-frame represents the
 proportion of pollen grains labelled with quantum dots (indicated in the
 "proportion_labelled" column) within one of five subsamples
 taken from an individual anther (the individual ID is indicated in the
 "individual_anther_lD" column) for each of the four species we
 tested (indicated in the "species" column)—Wachendorfia
 paniculata is coded as "Wp"; Sparaxis villosa is coded as
 "Sv"; Arctotheca calendula is coded as "Ac"; Oxalis
 purpurea is coded as "Op".Pollen transfer trial
 dataTo test whether
 quantum-dots influence pollen transport, we conducted multiple
 pollen-transfer trails with labelled and unlabelled S. villosa pollen
 using honey bees Apis mellifera capensis as pollen vectors. Each trial
 consisted of a single bee transferring pollen from a Qdot-labelled or
 -unlabelled donor (indicated by the "treatment" column) to a
 sequence of recipient flowers. Each trial is uniquely coded (column
 "trial_ID") and has an associated anther height measurement
 (measured in mm; see "anther_height" column) which indicates the
 height of the donor flower's anthers and the lower lip of the flower.
 Each row in the data-frame shows the number of pollen grains transferred
 (column "pollen_count") to a specific recipient flower in in the
 visit sequence (the sequence number is indicated in the
 "seq_num" column), with a measurement of each recipient
 flower's stigma height above the lower lip of the flower (column
 "stigma_height" measured in mm).