a Schematic summary of the proposed interaction between the canonical auxin pathway (black) and the CLSY1-RdDM mediated backup pathway (red). Existence of the latter only becomes apparent when the auxin pathway interrupted by environmental or genetic perturbation. b Average root phenotypes and lateral root number of Col-0 wild type, clsy1, tir1 and clsy1tir1 double mutants in control (C, blue) and low K (LK, red) conditions. The depicted average root architectures (scale bar 1 cm) were generated with EZ-Root-Vis software from individual plants grown in three independent experiments. The number of plants analysed (n) is indicated above the box plots. The centre lines are the medians of the data and crosses are the means; box edges are the first and third quartiles; the whiskers extend to 1.5 time the interquartile range. Different letters denote significant differences at P < 0.05 (one-way ANOVA). The source data of b are provided in a Source Data file.