Motte, H., Vanneste, S., & Beeckman, T. (2019). Molecular and Environmental Regulation of Root Development.
Annual Review of Plant Biology, 70(1). doi:10.1146/annurev-arplant-050718-100423
"4.1.3. Other nutrients. In addition to nitrogen and phosphate, other nutrients may also have
a clear effect on the root system, but very little is known about the controlling mechanisms.
In Arabidopsis, sulfur, magnesium, and iron deficiencies lead to a reduction in lateral root density,
whereas deficiencies in potassium, calcium, zinc, manganese, and boron result in an increased
lateral root density (50, 67, 68).
With the exception of zinc-deficient roots, the increase in lateral
root density is accompanied by an inhibition of primary root growth; therefore, it is not always
clear to what extent lateral roots are effectively induced by the nutrient deficiency. Manganese
excess is shown to have a negative effect on auxin biosynthesis and PIN4 and PIN7 expression,
which is probably associated with the reduction in lateral root density (164). Similarly, an excess
of iron represses PIN2 and negatively affects lateral root formation (73) while it induces AUX1 to
trigger root elongation (45). Multiple other genes involved in root development might, however,
be affected by iron deficiency as indicated by an in silico analysis showing iron-deficiency-specific
differential expression profiles for PIN4, TIR1, LBD16, and LBD29 (45)"