[Polarity of cell permeability and its control by phytochrome]

Growing chloronema and rhizoid cells of the intact protonema of Funaria hygrometrica absorb luminescent stains selectively. The cation stains--acridine orange and neutral red, at pH 5.0 are absorbed by growing tips of the apical cells. The anion stain (uranine) is absorbed by the basal end of the apical cells and by intercalary cells of the protonema filaments. Red light inactivates the cell permeability to the cation and anion stains. Far-red light partly reversed the action of the red light solely on the initial stages of the irradiation. During the red light induced branching of apical cells the cation stains enter the cells through a new originated growing point.