Auxin is one of the major five plant hormones, mostly present natively as free or conjugated indole-acetic acid (IAA), a tryptophan ... such as shoot and root growth, development, cell expansion ...

This is just like phototropism, in that auxin in the root inhibits growth and auxin in the stem promotes growth.

Plant hormones play a major role in plant growth and development ... found in the cytosol and nucleus (abscisic acid, gibberellins and auxins). For the most part, the major signaling components ...

In a stem, the cells on the shaded side contain more auxin and grow longer than the cells on the light side. This causes the stem to grow towards the light. It is vital to note that the plant does ...