How do viscin threads help Rhododendron pollen attach to pollinators?

In Rhododendron and related plants, viscin threads are very fine, sticky structures that function by holding pollen grains together in clumps known as tetrads.1

These threads facilitate pollination by entangling the pollen tetrads, which allows them to adhere to the bodies of visiting pollinators—such as large insects, birds, or bats—as the animals move between flowers and dislocate the strands. This mechanism ensures that a significant amount of pollen is effectively transferred to the pollinator, increasing the likelihood of successful fertilization.12