RESPIRATION RATE IN PLANTS
239
clear to which one of these respiratory increases the term "wound
respiration" has been applied. In many instances both rises have been
encompassed in the term; more often, tacitly or otherwise, only the
respiratory increment developed during a period of incubation has been
considered to be the wound respiration.
"Wound respiration" is at best an infelicitous term, since it implies a
stimulation evoked as a consequence of a trauma, and hence presumed
to be transient, unnatural, or both. Historically, furthermore, the onset
of wound respiration has frequently been attributed to some wound substance released by injured tissue. Currently available evidence suggests
that it is the change in the internal gaseous environment following the
preparation of thin tissue slices which on the one hand educes an immediate increase in respiration, and on the other permits the onset of metabolic events which result in time in a further respiratory increment of an
entirely different nature. The first effect can be observed in a short time
in potato tubers which are simply quartered (see Johnstone, 1925; Hopkins, 1927) or peeled (Appleman, 1916). The second effect, in potato
at least, is in fact limited to the superficial layers of tissue, and it is the
second effect which controls the relation between the specific respiration
rate and the specific surface (see below).
If the respiration of freshly cut tissue should turn out to be qualitatively similar to that of the intact tuber, this respiration may properly
be called the "basal respiration." The respiration which arises with time,
on the other hand, defies a simple, explicit appellation. However, the
term "induced respiration" or "developed respiration," when considered
in context, appears to be an improvement over the misleading designation which implicates wounding as a responsible factor.
Barker (see Burton, 1950) has calculated the rate of C0 2 evolution of
intact potato tubers at 25° C. to be about 0.012 mg. C0 2 /g./hour (6.0
/xl./g./hour; Qoo = 0.03). The respiration rate may be expressed in terms
of oxygen consumption, since the R.Q. has been shown by Barker to be
1.0 (James, 1953a). The rate for intact tubers is precisely the rate deduced by Steward et al. (1932) for tissue in bulk by extrapolation of the
respiratory rate of potato disks for ever-decreasing values of specific
surface.
However, in the view of Steward and his co-workers the diminution
in specific respiration rate with increasing disk thickness is the consequence of an inadequate supply of oxygen to tissue buried below the
surface. The logical extension of this point of view implies that the rate
of C0 2 evolution for tissue in bulk obtained by extrapolation must represent C0 2 evolution in the complete absence of oxygen, and must perforce
represent fermentative rather than respiratory C0 2 . However, there is
239
clear to which one of these respiratory increases the term "wound
respiration" has been applied. In many instances both rises have been
encompassed in the term; more often, tacitly or otherwise, only the
respiratory increment developed during a period of incubation has been
considered to be the wound respiration.
"Wound respiration" is at best an infelicitous term, since it implies a
stimulation evoked as a consequence of a trauma, and hence presumed
to be transient, unnatural, or both. Historically, furthermore, the onset
of wound respiration has frequently been attributed to some wound substance released by injured tissue. Currently available evidence suggests
that it is the change in the internal gaseous environment following the
preparation of thin tissue slices which on the one hand educes an immediate increase in respiration, and on the other permits the onset of metabolic events which result in time in a further respiratory increment of an
entirely different nature. The first effect can be observed in a short time
in potato tubers which are simply quartered (see Johnstone, 1925; Hopkins, 1927) or peeled (Appleman, 1916). The second effect, in potato
at least, is in fact limited to the superficial layers of tissue, and it is the
second effect which controls the relation between the specific respiration
rate and the specific surface (see below).
If the respiration of freshly cut tissue should turn out to be qualitatively similar to that of the intact tuber, this respiration may properly
be called the "basal respiration." The respiration which arises with time,
on the other hand, defies a simple, explicit appellation. However, the
term "induced respiration" or "developed respiration," when considered
in context, appears to be an improvement over the misleading designation which implicates wounding as a responsible factor.
Barker (see Burton, 1950) has calculated the rate of C0 2 evolution of
intact potato tubers at 25° C. to be about 0.012 mg. C0 2 /g./hour (6.0
/xl./g./hour; Qoo = 0.03). The respiration rate may be expressed in terms
of oxygen consumption, since the R.Q. has been shown by Barker to be
1.0 (James, 1953a). The rate for intact tubers is precisely the rate deduced by Steward et al. (1932) for tissue in bulk by extrapolation of the
respiratory rate of potato disks for ever-decreasing values of specific
surface.
However, in the view of Steward and his co-workers the diminution
in specific respiration rate with increasing disk thickness is the consequence of an inadequate supply of oxygen to tissue buried below the
surface. The logical extension of this point of view implies that the rate
of C0 2 evolution for tissue in bulk obtained by extrapolation must represent C0 2 evolution in the complete absence of oxygen, and must perforce
represent fermentative rather than respiratory C0 2 . However, there is