For long treatments, t‐CA or c‐CA was added immediately after the transfer of the 2‐day‐old seedlings to 50‐ml tubes, and analysis was done 1–8 days after transfer (DAT). For short treatments, the isomers were added at 3 DAT, and analysis was done 1, 3, 6, 12, or 24 h after the start of the treatment. After several hours/days of growth in 50‐ml tubes, coleoptiles were dissected from the seedlings and cleared using a protocol adjusted from Nelissen et al. (2013 (link)). Coleoptiles were treated with ethanol:acetic acid (3:1) for 2 days before being positioned on a square dish (245 × 245 mm; SPL Life Sciences) filled with 0.66% (w/v) Plant Tissue Culture Agar (Neogen) and scanned (in color at 600 dpi). The obtained coleoptile images were analyzed using Plength, an in‐house developed program for the automated analysis of rice seedling lengths (Vlaminck et al., 2020 (link)). For contrast purposes and as a reference, a black background with a 2‐cm scale bar in one of the lower corners was placed behind the plate with coleoptiles before scans were made.