Like the book and other bloggers have mentioned PR practitioners and reporters need each other in order to complete a full days work. It's like a guy, you can't live with him, but you can't live without him. Although they need each other, they both have their separate agenda that they need to accomplish and it is easy for them to get into each others way.
Their relationship is symbolic because they can not "function" without each other. Each area as their own duty. PR is to the companies they work for, to make them look good and put them into the spot light when possible. It works in their advantage to use the media as a means of getting their information/story to the public. In terms PR uses the media for their audience. Journalists have a duty to report to the public and report stories that the public has an interest in knowing. The reporters would not be able to collect and cover all of the day's news if they did not have PR practitioners to write press releases, that contribute to the publics knowledge of business topics, entertainment, and travel. By having press releases, it frees the media to cover other stories.
Although it seems like they benefit well from each other, there is still tension that exists between the two. Sometimes the information that PR wants to report is not exactly what journalists want to report. They like the stories that involve dirt and scandals, stories that most of the audience will read about. Because it is the duty of a PR to protect and company and make them look good this causes a conflict.