http://www.bbc.co.uk/schools/gcsebitesiz...rev1.shtml negative geotropism negative geotropism http://www.bbc.co.uk/schools/gcsebitesiz...rev1.shtml BBC Bitesize: Controlling plant growth BBC Bitesize: Controlling plant growth http://www.bbc.co.uk/schools/gcsebitesiz...rev1.shtml Tropisms and Auxin Experiment (BBC) negative geotropism