Other studies have shown that 850 nm light (which can be considered either Far Red or Near Infra Red), stimulates cell division in both the tips of branches and the tips of the roots.
I had assumed (love that word) specific control chemicals were assembled in the leaves and transported to the roots. The discovery of NIR receptors in the roots makes good evolutionary sense.
A great many ideas that make good sense prove to be false so having this positive result is a first step in further research.