The plant cuticle as a stage for plant-pollinator interactions

Abstract

Pollinators shape the world around us. They have driven the remarkable evolution of the flowering plants, and the resulting diversity of plants adorn gardens across the planet. They are often chosen by us for their smell or their scent, but the pollinators themselves pick up more detail. The shape of the floral cells, the architecture of the stamen, the nectar-reproduction rate, and more, are all important pieces of information which the pollinators integrate in their quest for efficient foraging. In this work, we have looked at how plant-pollinator interactions might shape the composition of the floral waxy cuticles. By analysing the cuticular composition of flowers and leaves, we have looked at how these organs’ cuticular compositions differ, and related this to the varying selection pressures leaves and petals experience. In particular, petals were shown to have fewer wax crystals as well as a lower overall wax load than leaves, and we argue this is due to the selection for floral surfaces which are easy for pollinators to handle. We also present the first known case of structural colouration created by cuticular wax crystals acting as a pollinator signal. The wax crystals on the flower associated bracts of Cerinthe major purpurascens in coordination with underlying purple pigments create a strong, blue colour. Removing these wax crystals leads to a strong reduction in pollinator visitation. Finally, we identify volatile compounds in bumblebee foragers’ headspace, and shed some light onto the identity of the bumblebee “chemical footprints” which for 20 years have been, we argue incorrectly, identified as long chain hydrocarbons. The volatile compounds identified here are passively released by foragers and disappear within a pollination-relevant timeframe, and we argue that they are more likely to be the constituents of the timestamp.

Date of Award	24 Jan 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Heather M Whitney (Supervisor), Ian D Bull (Supervisor) & Keara A Franklin (Supervisor)