LAX3::GUS expression during AR development in 14-day-old Col seedlings grown under different hormonal conditions. (A–F; HF) Expression at stage III (A) and IV (B), at the base of a stage VII ARP (C), in the forming vasculature of emerging (D) and elongating ARPs (E) and in a few cap cells, and the differentiating vasculature of a mature AR (F). (G–K; NAA) High and uniform expression at stage IV (G) and VI (H), in the ARP basal half, before (I) and after (J) protrusion, and in cap cells and precociously differentiated tissues in a mature AR (K). (L–P; IBA + Kin) High expression at stage III (L) and V (M), in the basal half of an emerging ARP (N), in the vasculature of an elongating ARP (O) and a mature AR (P), and in some cap cells in the latter (P). (Q–U; Kin, hypocotyl transition zone) LAX3 expression at stage II (Q) and IV (R), at the base of a stage VII ARP (S), in the developing vasculature of elongating ARPs (T) and mature ARs (U), and faintly in the AR cap (U). Scale bars: (A, B, H, I, K, M, Q–S) = 10 µm; (D, G, L, N–P, U) = 20 µm; (C, E, F, J, T) = 30 µm.