A history of back and forth
Fascination with solar tracking dates back at least to the time
of ancient Greece, and the Roman poet Ovid penned the myth of
the nymph Clytie in his Metamorphoses [21]. After being jilted by
her lover, the sun god Helios, the languishing Clytie stared at the
sun from the same outcrop for nine days, after which she transformed into a rooted, heliotropic plant. Ovid could not have drawn
his inspiration from sunflower because H. annuus and its relatives
are native to North America, and he most likely had a member of
the genus Heliotropium in mind. Many other plants have similar
forms ofinflorescence or floral heliotropism, including Chrozophora
tinctoria (Euphobiaceae), Xanthium strumarium (Asteraceae), and
diverse arctic and alpine species [5,22].
Sunflower derives its name in many languages from its reputation for solar tracking (Spanish: girasol is a compound of “to spin”
and “sun”; French: tournesol is a compound of“to turn” and “sun”).
Nonetheless, due to the common misconception that heliotropism
continues past anthesis, the status of sunflower as a solar tracking plant has frequently been questioned. This dates back as early
as European herbalists’ descriptions of New World plants in the
1500s: “some have reported it to turn with the sun, the which I
could never observe, although I have endeavored to find out the
truth ofit” [23]. In the late 1800s, several reports claimed that sunflowers did not track the sun and argued that the name was instead
derived originally from the resemblance of the flower’s disk and