RESPIRATION RATE IN PLANTS
247
agent responsible either for the repression of respiration in the intact
tuber, or for the inhibition of the development of the age-induced respiratory increment in potato slices. Since all experiments point to an endogenously produced, volatile substance as the controlling agent in the
phenomena discussed above, attention may profitably be focused on the
volatile alcohols which are produced by potatoes and which suppress
their sprouting (Burton, 1952, 1956).
Although it has been pointed out that water injection of the intercellular air spaces does not appear to occur to a great extent, there is
some evidence that contact with water slightly alters the diffusion characteristics of gases into or out of the tissue. For Steward et al. (1932)
have shown that when disks are cut and immediately suspended in air
they respire maximally at a surface-volume ratio less than that required
by disks washed 3 hours in water and then placed in air; and the respiration of the latter in turn at a comparable surface-volume ratio exceeds
that of disks kept in water.
As has already been indicated, after disks or tissue slices are removed
from certain fleshy organs, a respiratory rise develops upon incubation,
as an increment in addition to that achieved immediately upon removal
of the slices from the interior of the tissue. This increment is of particular interest, since there are numerous indications that it represents a
qualitative change from the basal respiration.
The respiratory rise which occurs when potato tissue is incubated
in water has been studied by Steward et al. (1932), Stiles and Dent
(1947), Schade and Levy (1949), Thimann et al. (1954), Sharpensteen
(1953), and Hackett (1956b). There is general agreement with respect
to the pattern followed by this rise. The respiration increases to a
maximum within 20 or 30 hours, and remains at that high level for at
least 80 hours (Stiles and Dent). The respiration increase may be three
to fivefold. The respiratory quotient remains approximately 1.0 throughout the experimental period. The respiratory trends exhibited by carrot
and beet disks following cutting are in some respects similar to that
exhibited by potato. However, there is considerable variability, depending upon the age and state of the tuberous material at the time the disks
are prepared (Turner, 1940; Turner and Hanly, 1949; Stiles and Dent,
1947).
There is evidence that in beets, as well as in carrots, metabolic conditions vary in disks freshly cut from the root. Robertson et al. (1947)
found a respiratory peak in beet disks after some 50 hours of incubation
in distilled water. The increase was approximately 150%. Stiles and
Dent, and Bennet-Clark and Bexon (1943), on the other hand, found a
rise in respiration which continued for 210 hours.
247
agent responsible either for the repression of respiration in the intact
tuber, or for the inhibition of the development of the age-induced respiratory increment in potato slices. Since all experiments point to an endogenously produced, volatile substance as the controlling agent in the
phenomena discussed above, attention may profitably be focused on the
volatile alcohols which are produced by potatoes and which suppress
their sprouting (Burton, 1952, 1956).
Although it has been pointed out that water injection of the intercellular air spaces does not appear to occur to a great extent, there is
some evidence that contact with water slightly alters the diffusion characteristics of gases into or out of the tissue. For Steward et al. (1932)
have shown that when disks are cut and immediately suspended in air
they respire maximally at a surface-volume ratio less than that required
by disks washed 3 hours in water and then placed in air; and the respiration of the latter in turn at a comparable surface-volume ratio exceeds
that of disks kept in water.
As has already been indicated, after disks or tissue slices are removed
from certain fleshy organs, a respiratory rise develops upon incubation,
as an increment in addition to that achieved immediately upon removal
of the slices from the interior of the tissue. This increment is of particular interest, since there are numerous indications that it represents a
qualitative change from the basal respiration.
The respiratory rise which occurs when potato tissue is incubated
in water has been studied by Steward et al. (1932), Stiles and Dent
(1947), Schade and Levy (1949), Thimann et al. (1954), Sharpensteen
(1953), and Hackett (1956b). There is general agreement with respect
to the pattern followed by this rise. The respiration increases to a
maximum within 20 or 30 hours, and remains at that high level for at
least 80 hours (Stiles and Dent). The respiration increase may be three
to fivefold. The respiratory quotient remains approximately 1.0 throughout the experimental period. The respiratory trends exhibited by carrot
and beet disks following cutting are in some respects similar to that
exhibited by potato. However, there is considerable variability, depending upon the age and state of the tuberous material at the time the disks
are prepared (Turner, 1940; Turner and Hanly, 1949; Stiles and Dent,
1947).
There is evidence that in beets, as well as in carrots, metabolic conditions vary in disks freshly cut from the root. Robertson et al. (1947)
found a respiratory peak in beet disks after some 50 hours of incubation
in distilled water. The increase was approximately 150%. Stiles and
Dent, and Bennet-Clark and Bexon (1943), on the other hand, found a
rise in respiration which continued for 210 hours.