What test should I use?


I am trying to do a statistical analysis on some data I collected at Uni and I am really confused about which test to use. I applied a range of shear stresses (60s, 140s, 250s, 500s, 1000s, 2000s, 3000s and 4000s) to some cells and then I recorded whether a cell marker was present or not. The outcomes are percentages i.e. percentage of cell population with a particular marker.
Now I want to do a statistical test to see if there is a relationship between shear stress and cell marker. Which test do you think I should use and can you give me the rationale behind this decision?

Thanks :)