248
GEORGE G. LATIES
The time required for the full respiratory increment to develop in
slices clearly indicates that merely to supply oxygen, or to remove carbon dioxide or some other volatile metabolic product, cannot per se
cause the observed respiratory increase, whether or not one imputes
to such a cause the original higher specific respiratory level of disks
compared to that of tuber. Steward, Wright, and Berry have described
some of the profound changes within the tissue which accompany the
development of the respiratory increment. The starch granules are seen
to disappear from the superficial, actively respiring cell layers,
cyclosis begins in these same cells and an active protein synthesis may be demonstrated there (Steward et al, 1940; Steward and
Preston, 1941). The disappearance of starch proceeds to a depth of
0.8 mm. (6 to 7 cells) in unwashed disks respiring in moist air, and to
but 0.22-0.24 mm. in disks respiring under water. The suberization and
cambial development which may be expected to occur in potato slices in
air occur only to a limited extent or not at all in water (Steward et al,
1932; Hackett and Thimann, 1952a). Steward (1932) has calculated
that the depth of tissue in which active metabolism occurs is 4 cells
(0.47 mm.) in water, 8-9 cells (0.92 mm.) in air, following a short washing in water, and 12 cells (1.44 mm.) in air after superficial rinsing. In
each case the level of visible starch depletion is rather less than the calculated depth of actively metabolizing tissue.
With respect to the respiratory rise which gradually develops during
the incubation of disks in air or aerated solutions, interest centers upon
the changes of internal factors, since, in sufficiently thin disks, there is
no question of an inadequate oxygen supply. Regarding the nature
of the developed respiration relatively little has been said until recently,
except perhaps for the induced respiration in carrot disks, in which a
portion of the initial and all of the subsequent respiration can be inhibited by cyanide, although a certain relatively constant component of
the respiration is resistant to cyanide at all times. It is of particular
interest that the cyanide-sensitive fraction of the respiration in carrot is
also completely inhibited by malonate, whereas the so-called basal
respiration is resistant to malonate (Hanly et al, 1952). The induced
respiration in those tissues in which the entire respiration is initially
repressed by cyanide has in the past tacitly been assumed to represent
simply a quantitative change. However, the recent descriptions by
Schade and Levy (1949), and by Thimann et al. (1954), of the change
during incubation in the characteristics of the terminal oxidase of
potato slices have emphasized that qualitative changes occur during
aging.
Some insight into the nature of those changes in intermediary metab-
GEORGE G. LATIES
The time required for the full respiratory increment to develop in
slices clearly indicates that merely to supply oxygen, or to remove carbon dioxide or some other volatile metabolic product, cannot per se
cause the observed respiratory increase, whether or not one imputes
to such a cause the original higher specific respiratory level of disks
compared to that of tuber. Steward, Wright, and Berry have described
some of the profound changes within the tissue which accompany the
development of the respiratory increment. The starch granules are seen
to disappear from the superficial, actively respiring cell layers,
cyclosis begins in these same cells and an active protein synthesis may be demonstrated there (Steward et al, 1940; Steward and
Preston, 1941). The disappearance of starch proceeds to a depth of
0.8 mm. (6 to 7 cells) in unwashed disks respiring in moist air, and to
but 0.22-0.24 mm. in disks respiring under water. The suberization and
cambial development which may be expected to occur in potato slices in
air occur only to a limited extent or not at all in water (Steward et al,
1932; Hackett and Thimann, 1952a). Steward (1932) has calculated
that the depth of tissue in which active metabolism occurs is 4 cells
(0.47 mm.) in water, 8-9 cells (0.92 mm.) in air, following a short washing in water, and 12 cells (1.44 mm.) in air after superficial rinsing. In
each case the level of visible starch depletion is rather less than the calculated depth of actively metabolizing tissue.
With respect to the respiratory rise which gradually develops during
the incubation of disks in air or aerated solutions, interest centers upon
the changes of internal factors, since, in sufficiently thin disks, there is
no question of an inadequate oxygen supply. Regarding the nature
of the developed respiration relatively little has been said until recently,
except perhaps for the induced respiration in carrot disks, in which a
portion of the initial and all of the subsequent respiration can be inhibited by cyanide, although a certain relatively constant component of
the respiration is resistant to cyanide at all times. It is of particular
interest that the cyanide-sensitive fraction of the respiration in carrot is
also completely inhibited by malonate, whereas the so-called basal
respiration is resistant to malonate (Hanly et al, 1952). The induced
respiration in those tissues in which the entire respiration is initially
repressed by cyanide has in the past tacitly been assumed to represent
simply a quantitative change. However, the recent descriptions by
Schade and Levy (1949), and by Thimann et al. (1954), of the change
during incubation in the characteristics of the terminal oxidase of
potato slices have emphasized that qualitative changes occur during
aging.
Some insight into the nature of those changes in intermediary metab-