238
GEORGE G. LATIES
cytochrome oxidase activity. Since cytochrome oxidase has been found
almost exclusively in particles which have been shown both to oxidize
pyruvate (Millerd, 1953) and to phosphorylate (Laties, 1953a; Bonner
and Millerd, 1953), and since other terminal oxidases have not as yet
been linked to phosphorylative systems, nor to the oxidation of pyruvate,
the most tenable explanation for the absence of aerobic fermentation
under conditions where respiration is inhibited by the reduced partial
pressure of oxygen would be that the inhibited oxidative system is not
a phosphorylative one.
Fidler (1951) has demonstrated that a clear effect of aerobiosis in
apple fruits is to conserve, carbohydrate substrate—the fundamental criterion of the Pasteur effect. However, there is no indication in Fidler's
work whether conservation was achieved by a resynthesis of carbohydrate or by a diminished utilization of it. Simon (1953a, 1953b) and
James (1953a) have discussed evidence from yeast metabolism which
appears to rule out the oxidative resynthesis theory. No evidence is now
7
available to warrant the assumption that the Pasteur mechanism in higher
plants differs from that in yeast.
III. PHYSIOLOGICAL ASPECTS OF RATE REGULATION
1. Wound
Respiration
The difficulties inherent in establishing a comprehensive explanation
for the many examples of so-called wound respiration will be evident
in an examination of the latter phenomenon as it occurs in tissues of
tubers and tuberous roots. There is evidence at hand that wound respiration represents a fundamental change in the metabolic pattern of these
tissues, the change being concerned primarily with the biochemical
mechanisms which control the rates at which certain respiratory systems
function. Rate control in these instances appears to be of the type which
has been described in the introduction as truly regulatory in nature.
The term wound respiration, as applied to tubers and tuberous roots,
pertains to the increase in respiratory activity exhibited by relatively
thin slices of tissue compared to the respiration of an equivalent quantity of tissue in the intact tuber or root. Even this very simple definition
involves some ambiguity. Thus, when the respiration of thin disks of
potato or carrot is measured immediately following the preparation of
the disks, the respiratory rate is at once several fold higher than that of
an equivalent quantity of tissue within the tuber or root. When the
disks are subsequently incubated at room temperature for 24 hours or
longer, whether in moist air or in running water, an additional respiratory increment develops, which, as will be shown below, is different in
nature from the respiration in freshly cut disks. It has not always been
GEORGE G. LATIES
cytochrome oxidase activity. Since cytochrome oxidase has been found
almost exclusively in particles which have been shown both to oxidize
pyruvate (Millerd, 1953) and to phosphorylate (Laties, 1953a; Bonner
and Millerd, 1953), and since other terminal oxidases have not as yet
been linked to phosphorylative systems, nor to the oxidation of pyruvate,
the most tenable explanation for the absence of aerobic fermentation
under conditions where respiration is inhibited by the reduced partial
pressure of oxygen would be that the inhibited oxidative system is not
a phosphorylative one.
Fidler (1951) has demonstrated that a clear effect of aerobiosis in
apple fruits is to conserve, carbohydrate substrate—the fundamental criterion of the Pasteur effect. However, there is no indication in Fidler's
work whether conservation was achieved by a resynthesis of carbohydrate or by a diminished utilization of it. Simon (1953a, 1953b) and
James (1953a) have discussed evidence from yeast metabolism which
appears to rule out the oxidative resynthesis theory. No evidence is now
7
available to warrant the assumption that the Pasteur mechanism in higher
plants differs from that in yeast.
III. PHYSIOLOGICAL ASPECTS OF RATE REGULATION
1. Wound
Respiration
The difficulties inherent in establishing a comprehensive explanation
for the many examples of so-called wound respiration will be evident
in an examination of the latter phenomenon as it occurs in tissues of
tubers and tuberous roots. There is evidence at hand that wound respiration represents a fundamental change in the metabolic pattern of these
tissues, the change being concerned primarily with the biochemical
mechanisms which control the rates at which certain respiratory systems
function. Rate control in these instances appears to be of the type which
has been described in the introduction as truly regulatory in nature.
The term wound respiration, as applied to tubers and tuberous roots,
pertains to the increase in respiratory activity exhibited by relatively
thin slices of tissue compared to the respiration of an equivalent quantity of tissue in the intact tuber or root. Even this very simple definition
involves some ambiguity. Thus, when the respiration of thin disks of
potato or carrot is measured immediately following the preparation of
the disks, the respiratory rate is at once several fold higher than that of
an equivalent quantity of tissue within the tuber or root. When the
disks are subsequently incubated at room temperature for 24 hours or
longer, whether in moist air or in running water, an additional respiratory increment develops, which, as will be shown below, is different in
nature from the respiration in freshly cut disks. It has not always been