Patterns of change in floral color and odor of Lonicera calcarata are in relation to pollinator behavior

Floral color and odor serve as attractants for pollinators. It remains
unclear how changes in these traits in color-change species interact with
pollinators and impact plants’ reproductive success. Lonicera calcarata
flowers change from white (night 1, day 1) through yellow and orange
(night 2, day 2) to orange-red (night 3, day 3). Our research showed that
floral characters, stigma activity, nectar production and floral spectral
reflectance decreased through flowering phases. Floral odor mainly
comprised fatty acids, aldehydes, monoterpenes and alcohols, especially
n-hexadecanoic acid, hexadecanal and 3-carene. Total response intensity of
floral odor was significantly higher on nights 1 and 3 than in other
flowering phases, largely due to presence of fatty acids. The emission of
n-hexadecanoic acid was higher on nights 1 and 3 compared to other phases,
while hexadecanal emission remained constant throughout the flowering
stages. The emission of 3-carene was highest on night 1. L. calcarata was
mainly pollinated by the moth Chorodna strixaria, the butterfly Acosmeryx
naga and three bumblebees (Bombus melanurus, B. eximius, B. sonani) and
they all preferred to visit white (younger) flowers. Moths had a
preference for 3-carene and no significant preference for n-hexadecanoic
acid and hexadecanal. Seed sets of nocturnal pollination and control
treatments were not significantly different. L. calcarata could produce
seeds by self-pollination, and cross-pollination significantly increased
seed set. Floral color guides pollinators to visit younger flowers with
more floral rewards and higher stigma activity. Different chemical
compounds in floral odor may not only attract pollinators but also avoid
herbivore damage.