Carnation flowers dyed with food colouring. Transpiration occurs in living plants starting at the roots. In plants xylem cells move water up the plant and phloem cells move soluble food products around the plant. Capillary action refers to the process where liquids such as water ascend the sides of narrow tubes through cohesion and adhesion. The leaves and petals transpire and replacement liquid is drawn up the plant even when stems have been cut. Since the 'nutrients' in the water are dyed, the dye also travels up the stem of the flower. This demonstrates capillary action in plants called transpirational pull. The amount of colouring will dictate how strong the petals are dyed. The water was very dark to achieve this strength of colour but a lighter water was used in the final photograph.