Search engine results are not only Pr but alot of other factors. Some would be content and keywords and links to the site.
pr does not depent on the serp results. pr is only related backlinks. more backlinks means better pr . focus on backlinks
As everyone said there's no relation between PR and SERPs. To gain high pr you should have high quality backlinks. In case of PR Quantity doesn't matters but Quality backlinks matters.