Thistles have thigmonastic staminal filaments as part of their pollination mechanism. When pollinators (bees and bumble bees) forage on their flowers they either touch the filaments directly or bend the anthers. Either movement triggers a rapid (less than 2 seconds) and strong contraction of the five filaments, which pulls down the anthers over the style and thereby exposes the insect to large quantities of pollen that they then carry to other flowers.

The video shows the contraction of a filament after touching

We are particularly interested in the highly elastic staminal filaments. What are their sensory mechanism? How often can they contract and which force do they generate? What is the recovery time ?

elastic behavior

In addition to the interesting pollination system, the different rigidity of the floral parts allows a mechano-elastic study of the cell walls of the same plant that have developed at the same time yet have very different mechanical properties. The filaments and the basal style are soft whereas the flower leaves (corolla), and anthers are ridgid.