Figure 1.

Simplified Overview of the Shade Avoidance Syndrome

High planting densities lead to a reduction of the ratio between red and far-red light (R:FR), resulting in shoot elongation growth and slightly reduced root development. At the molecular level, low R:FR conditions result in reduced activity of phytochrome B (phyB). Inactive phyB allows phytochrome interacting factors (PIFs) to induce shoot elongation in an auxin-dependent manner. In parallel, gibberellin (GA) levels are increased, leading to the inhibition of the growth repressors, DELLA proteins, also leading to shoot elongation.