The crosstalk between SL and auxins is altered in PDR1 OE plants and thus exerts a role in shaping PDR1 OE plant phenotypes. GR24 treatments cause the removal of the auxin carrier PIN1 from the plasma membrane (Shinohara et al., 2013) and PIN1 protein abundances are down‐regulated in PDR1 OE root tips (Sasse et al., 2015). On the other hand, the auxin carrier PIN2 is positively regulated by SL (Pandya‐Kumar et al., 2014; Sasse et al., 2015). Also, the expression of DAD1 is negatively regulated by SL but positively regulated by auxins (Hayward et al., 2009). Auxin transport/allocation could be influenced in several tissues by PDR1 overexpression, thus also changing DAD1 expression and consequently SL biosynthesis. Analyses of the auxin patterns in PDR1 OE root tips showed that changes in endogenous SL concentrations can alter auxin transport and patterning, thus affecting cell length in the EZ and consequently root hair density close to the root tip. Several pin mutants were indeed reported to inhibit cell elongation in the EZ (Blilou et al., 2005). In root tips SL might influence the abundances of several PIN proteins at the plasma membrane either directly or by acting on auxin flows directed by PIN1 and PIN2. Additional auxin and PIN quantifications in specific plant tissues such as root hairs, lateral roots, lateral buds and leaves might elucidate in detail the mechanisms behind the crosstalk between SL and auxin transporters. Based on the results shown here, we propose that SL regulates cell expansion by changing the efficiency of auxin transport: this change reduces cell expansion (as seen in the EZ of PDR1 OE root tips) or allows cell expansion (as seen in leaf epidermal cells of PDR1 OE plants).