Biosynthesis and transport of SLs and consequently SL amounts and allocation in planta and in the rhizosphere are regulated by external and internal cues. An important external factor is the availability of inorganic phosphate (Pi) in the soil (reviewed in Brewer et al., 2013). On Pi‐poor substrates, plants react to starvation by inducing SL exudation into the soil as a beacon for AMF; by lateral root formation and root hair elongation for improving the rhizosphere exploration; and by inhibiting shoot lateral branching. It has been shown that PDR1 and DAD1 expression levels are both up‐regulated by low Pi conditions as well as by auxins (Lopez‐Raez et al., 2008; Kretzschmar et al., 2012), thus suggesting that SLs act as integrators of plant nutrient uptake with plant growth regulation.