Pollen shows a particular type of plant species and a particular type of environmental condition or habitat condition under which it was living. This type of study of pollen and spores called palynological study.
This type of study comes under the microfossil study, and now it is a very trending topic in determining the paleo-climate. Microfossil study is having more benefits because here we can do both qualitative and quantitative study.
Generally, nowadays we are doing a pollen study to know the glacial and inter glacial events. Because we know under different climatic condition different types of plant will grow. After their death, their pollen's get preserved under sediments and now we are analyzing them to construct the paleo-environment. But remember pollen preservation requires a very quick burial of sediments otherwise they are so susceptible that they can't be preserved .
