I have a new MacBook Pro with iPhoto installed. I edit photos, mainly photo orientation via rotating, but when I go back to run a slideshow the changes weren't saved and the photo is back to vertical...please help...thanks

I have a new MacBook Pro with Iphoto installed when purchased. When editing a photo, primarily orientation changes, the slideshow initially displays the photos in proper orientation. However, after leaving Iphoto and shutting down the computer, and then going back to run a slideshow the photo displays back to its' original orientation, that is, the edit-change was not saved. Please help...the program information says all edit-changes are automatically save and therefore there is no save command, but my changes are not being saved...thank you for any suggestions...HM