Plant is a professional wrestling term for a trained wrestler or actor who poses as a fan, usually seated in the front row of an event. Plants are a good tool for a heel wrestler to gain heat from the crowd.
One prime example is during Heidenreich's in-ring promo in the WWE, where the crowd continued to heckle him while he attempted to cut a promo in the ring. Out of anger, he exited the ring, went into the crowd and confronted a 'fan' who was heckling him. He proceeded to physically attack him, giving him a large amount of heat from the crowd. Earthquake, Test, Rob Conway, Steve Blackman, Tori, Beth Phoenix, Christopher Nowinski, Santino Marella, and in another sense, Zach Gowen and Kurt Angle all debuted as plants. Even Paul London was at one time a plant, when he was hit by Ric Flair during the spring of 2002.
Another famous plant was Jamison, who spoofed the dyed-in-the-wool mark wrestling fan in 1991 at WWF events. He was introduced as a nerd who dressed funny and acted as though he were borderline autistic. Eventually, Jamison became the mascot of the fan-favorite The Bushwhackers (after getting bullied by the jock-like Beverly Brothers).
Santino Marella made his WWE debut as a plant in April 2007, as an Italian fan chosen by Vince McMahon to face the then-reigning Intercontinental Champion Umaga in a No-Holds Barred Match for Umaga's title. With assistance from Bobby Lashley, Marella was victorious.
One recent plant in TNA Wrestling was independent wrestler Sal Rinauro. Rinauro was planted as a Jeff Jarrett fan in the front row of the iMPACT! Zone on the pre-show prior to TNA Slammiversary 2005. During a segment where Raven appeared to confront Jeff Jarrett (at which point the latter bailed out of the ring), the "fan" repeatedly prodded and heckled Jarrett, prompting Jarrett to throw the fan over the rail to the ringside area and smash his trademark guitar over the head of the fan. Jarrett was "arrested" for attacking the fan, allowing him to be removed from the King of the Mountain match. Raven went on to take his place, win the match, and become NWA World Heavyweight Champion.
A stunt granny is an obvious plant. The term comes from the NBC television special Exposed! Pro Wrestling's Greatest Secrets, which claimed to expose many of the secrets of pro wrestling, including the use of plants. One memorable scene showed heel wrestlers attacking an elderly woman, which the narrator explained by stating, "She's a stunt granny! How's that for piledriving Miss Daisy?"