282
H. WALTER AND E. STADELMANN
p. 592) It is also low in cells of halophytes (Repp, 1958, p. 472), and
passive permeation could not account for the degree of accumulation found
in living cells. Rather, some species of ions are taken up actively and transported into the vacuole by (probably immobile) carriers of the plasmalemma and/or the tonoplast (cf. Sitte, 1969, p. 341; Hill, 1969). Other
ion species (of opposite charge) move along passively to maintain electroneutrality. Many species of ions are present in the vacuole in a higher
concentration than in the external solution. While there is certainly a relationship between ion concentration in the protoplasm and in the cell sap,
little is known about the absolute concentration values (cf. MacRobbie,
1962, p. 867, Table III; Gutknecht, 1966, p. 34). Salts seem to enter
the protoplasm much easier than they can penetrate into the vacuole
(Repp, 1958, p. 483). It may be thought that ions which enhance imbibition of protoplasm will be at a higher concentration there than in the
vacuole (positive absorption into the cytoplasm). Such an assumption is
in agreement with the findings of MacRobbie (1962) that potassium and
sodium ion concentrations in the cytoplasm are higher than in the vacuole.
On the other hand, exclusion (negative absorption) may occur for ions
which decrease protoplasmic hydration.
The presence of ions in protoplasm will modify the capacity of the
protoplasm for hydration. For higher ionic concentrations the action depends on the kind of ions (lyotropic or Hofmeister series, see Bull, 1964,
p. 79ff). Swelling is increased more by univalent ions (cations or anions)
than by bivalent or trivalent ions. If an intermediate degree of protoplasmic
imbibition is already present, addition of monovalent ions will further hydration, while bivalent ions will decrease it. Ion effects on protoplasm can
be most easily demonstrated by microscopical observation of plasmolysis
forms of cells after addition of ions to the plasmolyticum or after plasmolyzing directly in salt solutions. Alkali salts (e.g., KN0 3 ) increase water
absorption by the protoplasm and cause cap plasmolysis, convex plasmolysis, or vacuolar contraction (tonoplast plasmolysis, see Stadelmann,
1956, p. 89ff), while alkaline-earth salts (e.g., CaCl 2 ) increase viscosity
and cause concave plasmolysis forms.
Pure salt solutions often are poisonous for protoplasm of many species
(cf. Kaho, 1923, p. 140ff; De Haan, 1933, p. 254ff; Iliin, 1935; Stadelmann, 1956, p. 192) while in mixtures of solutions of alkali and alkaline
earth salts (cf. LaHaye and Epstein, 1969, 1970; Bernstein, 1970) or
more complex salt mixtures, the damaging effect of the single salt is reduced or nullified (ion antagonism). The compensating effect by a low
concentration of an added ion is shown in the equilibrated salt solutions
where the addition of a relatively small amount of other ions is sufficient
to neutralize the damaging effect of an excessively high concentration of
H. WALTER AND E. STADELMANN
p. 592) It is also low in cells of halophytes (Repp, 1958, p. 472), and
passive permeation could not account for the degree of accumulation found
in living cells. Rather, some species of ions are taken up actively and transported into the vacuole by (probably immobile) carriers of the plasmalemma and/or the tonoplast (cf. Sitte, 1969, p. 341; Hill, 1969). Other
ion species (of opposite charge) move along passively to maintain electroneutrality. Many species of ions are present in the vacuole in a higher
concentration than in the external solution. While there is certainly a relationship between ion concentration in the protoplasm and in the cell sap,
little is known about the absolute concentration values (cf. MacRobbie,
1962, p. 867, Table III; Gutknecht, 1966, p. 34). Salts seem to enter
the protoplasm much easier than they can penetrate into the vacuole
(Repp, 1958, p. 483). It may be thought that ions which enhance imbibition of protoplasm will be at a higher concentration there than in the
vacuole (positive absorption into the cytoplasm). Such an assumption is
in agreement with the findings of MacRobbie (1962) that potassium and
sodium ion concentrations in the cytoplasm are higher than in the vacuole.
On the other hand, exclusion (negative absorption) may occur for ions
which decrease protoplasmic hydration.
The presence of ions in protoplasm will modify the capacity of the
protoplasm for hydration. For higher ionic concentrations the action depends on the kind of ions (lyotropic or Hofmeister series, see Bull, 1964,
p. 79ff). Swelling is increased more by univalent ions (cations or anions)
than by bivalent or trivalent ions. If an intermediate degree of protoplasmic
imbibition is already present, addition of monovalent ions will further hydration, while bivalent ions will decrease it. Ion effects on protoplasm can
be most easily demonstrated by microscopical observation of plasmolysis
forms of cells after addition of ions to the plasmolyticum or after plasmolyzing directly in salt solutions. Alkali salts (e.g., KN0 3 ) increase water
absorption by the protoplasm and cause cap plasmolysis, convex plasmolysis, or vacuolar contraction (tonoplast plasmolysis, see Stadelmann,
1956, p. 89ff), while alkaline-earth salts (e.g., CaCl 2 ) increase viscosity
and cause concave plasmolysis forms.
Pure salt solutions often are poisonous for protoplasm of many species
(cf. Kaho, 1923, p. 140ff; De Haan, 1933, p. 254ff; Iliin, 1935; Stadelmann, 1956, p. 192) while in mixtures of solutions of alkali and alkaline
earth salts (cf. LaHaye and Epstein, 1969, 1970; Bernstein, 1970) or
more complex salt mixtures, the damaging effect of the single salt is reduced or nullified (ion antagonism). The compensating effect by a low
concentration of an added ion is shown in the equilibrated salt solutions
where the addition of a relatively small amount of other ions is sufficient
to neutralize the damaging effect of an excessively high concentration of