glass electrode measurements of the ph value of the sap of cells of nitella show that azure b in the form of free base penetrates the vacuoles and raises the ph value of the sap to about the same degree as the free base of the dye added to the sap in vitro , but the dye salt dissolved in the sap does not alter the ph value of the sap .
C0007634
cells
C0042219
vacuoles