Fig. 6: Late boundaries are labeled by water stress marker histone H1.3.

A Inflorescence meristem localization. B Pattern of pH1.3::H1.3-GFP localization (green) right after dissection: maximum intensity projections (left), orthogonal section of the same image stack (middle), and number of H1.3 positive cells at the boundary of each primordium stage (right). C Vegetative meristem localization. D Pattern of pH1.3::H1.3-GFP localization (green) right after dissection: maximum intensity projections (left), orthogonal section of the same image stack (middle), and number of H1.3 positive cells at the boundary of each primordium stage (right). E–G Time series of new organs growing out of a non-dissected pin-like meristem 2 days after transferring to NPA-free medium at T0, T4, T8, and T24 hours. (G) Magnified transversal section of the T24 with inset showing 2 cells with H1.3 positive nuclei at the boundary. Representative images of n = 5, repeated at least once. M, meristem, LP, leaf primordium, FP, flower primordium. White arrows indicate H1.3 positive cell nuclei. Magenta corresponds to PI staining (B) or the plasma membrane marker pUBQ10::LTi6B-TdTomato (D, F, G). H Maximum intensity projections of pin-like meristems showing the temporal H1.3 inducibility after mannitol. Hyperosmotic stress evoked by mannitol treatment (300 mM) induced H1.3 after 48 h (n = 5), while induction was observed as early as 8 h after treatment with mannitol 600 mM (n = 5). No induction was observed in the hypoosmotic treatment (controls). The green channel shows pH1.3::H1.3:GFP, and magenta corresponds to chlorophyll. Scale bars = 50 μm.