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Abstract

Despite the increasing evidence for biosynthetic connections between flower pigments and volatiles, examples of such
relationships in polymorphic plant species remains limited. Here, we
investigated color-scent associations in flowers from Papaver
nudicaule (Papaveraceae). We determined the spectral reflectance
and the scent composition of flowers of four color cultivars. We found
that pigments and volatiles occur in specific combinations in flowers
of P. nudicaule. The presence of indole in the bouquets is strongly
associated with the occurrence of yellow pigments called nudicaulins,
for which indole is one of the final biosynthetic precursors. While
yellow flowers emit an excess of indole, orange flowers consume it
during nudicaulin production and lack the substance in their bouquet.
Using the honeybee, Apis mellifera, we evaluated how color and scent
affect the discrimination of these flowers by pollinators. Honeybees
were able to discriminate artificial odor mixtures resembling the
natural flower odors. Bees trained with stimuli combining colors and
odors showed an improved discrimination performance. Our results
indicate that the indole moiety of nudicaulins and emitted indole might
be products of the same biochemical pathway. We propose that
conserved pathways account for the evolution of color-scent
associations in P. nudicaule and that these associations positively
affect flower constancy of pollinators.