Question
Auxin(IAA) is the main hormone involved in plant photosynthesis.  Explain how the distribution of this hormone can stimulate growth towards light?

Answer
Andi,
My expertise is not in botany.  My expertise is in horticulture.  This sounds like a school project and you need to learn how to use the Internet to research these subjects.  I will tell you what I know.  Auxins are hormones that plants use in their growth cycles just as humans and animals use hormones in their growth cycles.  The auxins are distributed throughout the plant but mainly in the leaves to catch the sunlight which reacts with chlorophyl to induce photosynthesis.  You can perform basic experiments to prove this by looking at sunflowers and daffodils whose blooms always face in the direction of the sun.  Another experiment you can do to prove that the auxins are stimulated by light is to plant some bean seeds (which are quick to germinate) in a pot and put them in the windowsill.  They will quickly germinate and aim towards the sun or other light source.  I hope this helps.
Tom