Staining of invertase activity. (A, B) – cortex cells in the transverse sections in the basal part of the maize root meristem, (C) the border cells liberated from the maize root caps into the medium. All sections were treated with 0.7 M mannitol previously. The reaction with (A, C) or without (B) sucrose in the incubation medium. Bar – 25 µm.