SULFURIC ACID IN DESMARESTIA

¹ Hopkins Marine Station of Stanford University, Pacific Grove, California

1. Brilliant cresyl blue accumulates in the vacuoles of Desmarestia munda and D. herbacea and the accumulated dye appears purple, indicating that the pH of the vacuolar sap is less than 1.0 or greater than 7.5. However, the expressed saps of these two brown algae have pH 1.0 or less and about 2.0, respectively. The outer cell membranes are injured by the low pH of the sap and methylene blue is not reduced by tissue homogenates at such low pH values.

2. Sodium cyanide, dinitrophenol, iodoacetate, and p-chloromercuribenzoate induce the release of acid from the cells, in which potassium, normally the cation most abundant in brown algal cells, is largely replaced by hydrogen. In D. munda hydrogen accounts for 75 per cent of the intracellular cation content. Tissue sodium is largely bound and contributes little to the cellular cation content.

3. The simplest interpretation of these data is that the acid is localized within the vacuoles of Desmarestia cells.