All about pollen

What is pollen?

Plants release pollen in the form of pollen grains as part of their reproduction cycle. Both flowering (angiosperms) and cone-bearing plants (gymnosperms) make pollen. Each individual pollen grain acts as a container, used to transport plant DNA. The male part of a flower (the stamen) is responsible for producing pollen grains, received by the female flower component (the carpel).

Pollen grains are microscopic and measured in micrometres (microns). One millimetre contains a thousand microns. Pollen size can vary from less than 10 to more than 100 microns. Plants produce large quantities of pollen to ensure at least some grains transfer from flower to flower and successful pollination takes place. Many plants rely on wind dispersal, but pollen can also be transported by water and animals. Without pollen and pollination, plants would not be able to produce seeds or fruit.

Palynology

Palynology is a field of science focused on the study of pollen. It is interested in the structure and formation of pollen grains, their classification and identification, and with pollen dispersal and preservation within the environment. Palynology is an important tool in agriculture, archaeology, botany and ecology, chemistry, climatology, entomology, forensics, geology and medicine.

This project is interested in fossilised pollen for information about past environments, to trace vegetation histories, and the past climatic conditions under which ancient plants grew. Understanding fossil pollen is based on the nature and behaviour of today’s pollen.

Why fossil pollen?

Pollen grains are unique to the plants they come from and can be identified under a microscope by their shape, size, surface patterns and ornamental features. It is possible to identify a plant according to its family and genus, and sometimes species level, based on its pollen.

Every pollen grain has an inner and outer wall. These layers are highly durable and serve to protect pollen from damage during the pollination process. Once a pollen grain falls to the ground, the majority of its material decompose but the wall layers are left behind and these eventually fossilise. Pollen can survive in sediments for many thousands to hundreds of thousands of years.

With distinctive shape, size and sculpturing, and because of their high resistance to decay, widespread dispersal, and their abundant production by plants, pollen makes an excellent fossil type.

The pollen-vegetation relationship

Plant surveys are needed to help understand the relationship between vegetation and a pollen assemblage. To know how representative fossil pollen is of a vegetation community in the past we need to see how well pollen from a pollen trap reflects vegetation from around the trap.  Studies dealing specifically with pollen-plant-vegetation relationships are rare.

This project therefore includes pollen trapping as well as vegetation surveys. Around each pollen trap we will survey plant species presence, their cover abundance, vegetation community structure, the physical environment, and the presence/absence of environmental disturbances.