Auxin travels by diffusion towards:

Explanation

Auxin is a plant hormone that is primarily produced in the shoot tips and young leaves. It travels downwards through the plant by the process of diffusion and active transport, primarily moving towards the base of the plant. This movement is crucial for processes such as cell elongation and root development. The other options are incorrect because auxin does not specifically travel towards the shoot, flowers, or leaves, but rather it moves downwards to the base for broader distribution and effect.