Gravitropism in flowering plants

- Cells in root tip produce IAA, transported along root - IAA initially transported to all sides of root - Gravity influences movement of IAA from upper side to lower side of root - Greater conc. of IAA builds up on lower side of root than upper side - As IAA inhibits elongation of root cells, greater conc. of IAA on lower side, cells on this side elongate less - The relatively greater elongated cells on upper side causes root to bend downwards towards force of gra.