274
GEORGE G. LATIES
considerations favor a direct association of salt accumulation with the
phosphorylative processes of the cell. Bartley and Davies (1954) have
studied the accumulation of Na+ and K+ by mitochondria from the
cortex of sheep kidneys. Accumulation proved to be completely dependent upon active metabolism, any of the components of the tricarboxylic acid cycle serving as suitable substrates. Significantly for the
favored theory, when pyruvate was oxidized anaerobically, the addition
of ATP raised the level of accumulation. With respect to the accumulation of cations in general, Lundegardh's hypothesis suggests that it is
simply an obligatory consequence of anion accumulation. That is, following the active uptake of an anion into the cell a cation must follow
to maintain electrical neutrality. Epstein (1954), however, has prepared
cation-bearing resins and has shown that cations are capable of eliciting
a salt respiration under conditions in which anion uptake is impossible.
Epstein and Leggett (1954) have shown that, in barley roots, the initial
rapid adsorption of cations, unaccompanied by anion uptake, is not related to the basic accumulation process in which cations and anions are
taken up alike. The earlier work of Epstein and Hägen (1952) strongly
suggests that there are specific carriers for cation accumulation. Such
carriers, and not binding sites on the surface of the protoplast (Lundegárdh, 1955a), are considered to provide for the known specificity of the
accumulation process.
The redox pump, as envisaged by Lundegárdh, should logically apply
to any electron-transporting system in which transient unsatisfied charges
arise as a consequence of single electron transfers. However, it appears
that in most of the plant tissues which have been studied, with the
possible exception of barley root tips from week-old barley seedlings
(Russell, 1954), salt accumulation is linked to the functioning of the
cytochrome oxidase system in particular, and not to any other. This
is so even when the nonsalt respiration of a tissue is cyanide-sensitive,
and hence mediated by a heavy metal terminal oxidase. Middleton
(1955) has shown that polyphenolase activity has nothing to do with
salt absorption in potato tissue. Since in most instances the respiration
associated with the functioning of the cytochrome oxidase system is
accompanied by oxidative phosphorylation, it would appear that the
latter process is the critical requirement for salt accumulation, rather
than the alternation of valence of a metal prosthetic group. Such a supposition would fit better the known effect of dinitrophenol on the accumulation process, and would also allow for a single interpretation of the
accumulation phenomenon, whether it occurs in aerobic organisms, facultative organisms, obligate anaerobes, or in aerobic organisms with a
cyanide-resistant respiration (Österlind, 1951). This interpretation an-
GEORGE G. LATIES
considerations favor a direct association of salt accumulation with the
phosphorylative processes of the cell. Bartley and Davies (1954) have
studied the accumulation of Na+ and K+ by mitochondria from the
cortex of sheep kidneys. Accumulation proved to be completely dependent upon active metabolism, any of the components of the tricarboxylic acid cycle serving as suitable substrates. Significantly for the
favored theory, when pyruvate was oxidized anaerobically, the addition
of ATP raised the level of accumulation. With respect to the accumulation of cations in general, Lundegardh's hypothesis suggests that it is
simply an obligatory consequence of anion accumulation. That is, following the active uptake of an anion into the cell a cation must follow
to maintain electrical neutrality. Epstein (1954), however, has prepared
cation-bearing resins and has shown that cations are capable of eliciting
a salt respiration under conditions in which anion uptake is impossible.
Epstein and Leggett (1954) have shown that, in barley roots, the initial
rapid adsorption of cations, unaccompanied by anion uptake, is not related to the basic accumulation process in which cations and anions are
taken up alike. The earlier work of Epstein and Hägen (1952) strongly
suggests that there are specific carriers for cation accumulation. Such
carriers, and not binding sites on the surface of the protoplast (Lundegárdh, 1955a), are considered to provide for the known specificity of the
accumulation process.
The redox pump, as envisaged by Lundegárdh, should logically apply
to any electron-transporting system in which transient unsatisfied charges
arise as a consequence of single electron transfers. However, it appears
that in most of the plant tissues which have been studied, with the
possible exception of barley root tips from week-old barley seedlings
(Russell, 1954), salt accumulation is linked to the functioning of the
cytochrome oxidase system in particular, and not to any other. This
is so even when the nonsalt respiration of a tissue is cyanide-sensitive,
and hence mediated by a heavy metal terminal oxidase. Middleton
(1955) has shown that polyphenolase activity has nothing to do with
salt absorption in potato tissue. Since in most instances the respiration
associated with the functioning of the cytochrome oxidase system is
accompanied by oxidative phosphorylation, it would appear that the
latter process is the critical requirement for salt accumulation, rather
than the alternation of valence of a metal prosthetic group. Such a supposition would fit better the known effect of dinitrophenol on the accumulation process, and would also allow for a single interpretation of the
accumulation phenomenon, whether it occurs in aerobic organisms, facultative organisms, obligate anaerobes, or in aerobic organisms with a
cyanide-resistant respiration (Österlind, 1951). This interpretation an-