On the Nature of the Dye Penetrating Nitella from Cresyl Blue.

Abstract

(1) Measurements of the sap of Nitella B with the glass electrode made with actively growing cells collected in early summer confirmed those formerly obtained 1 , 2 and showed that there were no seasonal changes affecting the results. Living cells were placed in cresyl blue solution at pH 9 until 0.07% dye had penetrated the vacuole, causing an increase of about 0.4 pH in the sap. This corresponded to the increase when 0.07% dye base was dissolved in the sap in vitro, but not to the behavior of the dye salt which did not raise the pH value. These results show that the dye does not penetrate as a salt (undissociated DCl or D ⁺ + Cl^-).

They also show that in case D ions penetrated by an exchange of cations, they must have exchanged with H ions to account for the increase in the pH value of the sap. In this case more H ions must diffuse than K ions. But this is very improbable, owing to the fact that the concentration of H ions is several thousand times lower than that of the K ions in the sap while there is no indication that the mobility of the H ions in the protoplasm is very different from that of the K ions. It must therefore be concluded that the dye penetrates as a base. Whether it does so in an undissociated form or as an ion pair must be left undecided.

(2) If the dye penetrates as D ions we should expect their mobility in the protoplasm to be very high since the dye penetrates rapidly even from a very dilute solution. This was tested by measurements of potential difference on living cells, employing 0.01 M CaCl₂ and cresyl blue at pH 8 and pH 9 made up in diluted borate buffer mixtures containing no K.