Auxin [/SIZE]as the plant hormone produced by the apical meristem in the zone of cell division of shoot and root tends to escape from the sunlight. Now if the Zone of cell division(tips) of the shoot of the plant is totally covered from sunlight supposedly the horizontal diffusion of auxin in the zone of cell division will not happen. Consequently the auxin diffuses uniformly downwards to the zone of cell elongation of the shoot. Now, will the horizontal diffusion of auxin happens in the zone of cell elongation ?? if it happens, then no use cover the tips of the shoot consisting of the zone of cell division only right ?