Flowers Facing Upwards Attract More Pollinators, Researchers Say

Plants with flowers pointing towards the sky may be more likely to attract moth pollinators, compared to shy sideways-facing flowers, a recent study revealed.  

Researchers from the University of California Irvine, and the University of KwaZulu-Natal, South Africa, discovered the disadvantages of being "shy" when examining two species of flowering plants: Zaluzianskya natalensis, whose flowers point upwards, and Zaluzianskya microsiphon, whose flowers point to the side, according to a news release.

Hawk moths primarily pollinate Z. natalensis and Z. microsiphon flowers, researchers explained. Hawk moths are known to have the longest tongues of all moths and butterflies, measuring upwards of 14 inches long, which they use to sip nectar from flowers, and in turn, pick up and disperse pollen grains. Flowers of Z. natalensis and Z. microsiphon open at night and day, respectively, but they overlap during early evening. However, this does not seem to make a difference for hawk moths that still prefer to feed on the upward-facing flowers of Z. natalensis when given the choice.

While the flowers of Z. natalensis have a stronger scent that draws pollinators, researchers found that artificially adding scent to the side-turning flowers of Z. microsiphon did not help attract any more moths. Next, researchers manipulated Z. microsiphon flowers to point upwards to increase their pollination appeal, and directed Z. natalensis flowers sideways to reduce their appeal. The white portion of petals is more visible when flowers point upwards, which added to researchers' hypothesis that flower direction plays a larger role in attracting pollinators than scent.

"The results show that orientation of flowers can result in reproductive isolation between closely related species," Dr. Diane Campbell, lead author of the study, explained in the release.

Reproductive isolation is often imposed by pollinators who prefer specific floral traits that may differ among related species.

Their study was recently published in the journal New Phytologist.

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