450e8c1c_Plant_Hormone_Theory__Effects
[Name] Auxin (IAA) [Speculated Role] Abundance of oxygen and maybe carbon dioxide [Effects] 
Induces new root formation that are sinks of oxygen. High amounts externally applied induce ethylene perhaps by stimulating then exhausting the supplies of oxygen. With cytokinin induces cell division. Levels peak during the day when oxygen is given off by the process of photosynthesis. Attracts all nutrients and hormones (maybe actually the ones that stimulate shoot growth, CK, SA, GA and Eth?) to the site of its synthesis, inducing positive feedback and apical dominance. Transported from the shoot through the phloem to the root perhaps with its super strong attraction of oxygen causing oxygen to tag along?
Plant Hormone Theory
Effects