(Only submitting this because Dniste's video is MIA. Credits to whomever this strat is due to. If any mods feel my explanation needs clarification, please feel free. I've updated this with a better video using the emulator.)

When you enter the plant room, do a quick turn, then tap the knife button. Then just run along the wall until you have to turn for the key. Grab the key quickly, otherwise the plant will start whipping you back away from the key. The plant will whip you on the way out (sometimes the plant will whip you all the way out too).