Easter egg: If you own the DVD highlight the THX logo in sound setup and quickly press 1138 on your DVD remote to enter a hidden goof reel (This works on Attack of the Clones as well.).
Easter egg: On the first two deleted scenes, highlight Main Menu and hit right. You'll get a different feature for each scene.
Chosen answer: According to "Inside the Worlds of Star Wars: Episode I" by Kristin Lund, they are "laser doors which lock into position in response to potentially lethal power outputs that occur intermittently during plasma activation process" (the fight takes place in a plasma energy processing plant). There are six laser doors in deference to an ancient Naboo legend in which Chaos is held back by six inpentrable gates. As you say though, they're really just a plot device to add dramatic tension to the duel!
Sierra1 ★