White chrysanthemum flowers (Chrysanthemum sp.) in plain water and dyed blue. The flower stem at right was placed in water that had blue food colouring added to it. The petals on the flower transpire, they allow water to evaporate as an outcome of the process of gaining carbon dioxide from the air. Water flows upward through the stem by a combination of capillary action and the difference in hydrostatic pressure. Water enters the stem and roots by osmosis, bringing with it dissolved nutrients or, in this case, food colouring.