262
GEORGE G. LATIES
respiratory changes which occur when disks are aged in air are a prerequisite to the absorption of water by these tissues. Just as lithium, and
to some extent rubidium, prevent these respiratory changes in chicory
(Laties, 1954, and in press), so rubidium prevents or delays the
ability of artichoke disks to absorb water in response to auxin (Hanson
and Bonner, 1955). Since the respiratory changes which occur during
incubation occur independently of the presence of auxin, those changes
cannot in themselves result in metabolic water uptake. Hackett and
Thimann (1952a) have presented an interesting experiment which suggests that certain preliminary auxin-dependent metabolic events, which
in potato disks lead ultimately to the subsequent absorption of water in
response to auxin, may go on at a lower oxygen concentration than that
which permits water absorption. Disks kept for 6 days in 7% 0 2 -93% N 2
(a condition excluding appreciable water uptake) when transferred to
air, immediately absorb water at a rate equal to the maximum rate
evinced by disks which had been kept continuously in air.
In conclusion, it may be said that the obligatory relationship between
auxin-induced growth and respiration is not restricted to the visible stages
of growth. In some tissues (Avena, Bonner, 1949; potato, Hackett and
Thimann, 1952a, 1953; carrot, Steward et al, 1952) an auxin-induced
increase in respiration accompanies cell enlargement, while in other
tissues (tobacco pith, Newcomb, 1954) an auxin-induced stimulation
of respiration precedes visible growth. These observations favor the
previously stated contention that water movement into growing cells is
osmotic, and that the effect of respiration on growth is to supply energy
for the endergonic reactions which bring about plasticization of the
cell wall.
3. The Relation of Salt Absorption to Respiration
The mechanisms of ion absorption and accumulation have been much
discussed of late. A survey nf the extensive literature, together with discussions of the salient aspects of salt movement into cells and tissues,
may be obtained from reviews by Sutcliffe (1954), Lundegárdh (1955a),
Epstein (1956), Kramer (1956a), and Robertson (1956), and from the
volume edited by Clarke and Nachmansohn (1954) dealing with ion
transport across membranes.
The simultaneous accumulation of both members of an ion pair when
the latter are freely dissociated within the cell is a process clearly dependent upon the respiratory metabolism. In the higher plants the
dependence is, more specifically, upon the aerobic respiration. Accumulation of ions, whether both members of a salt pair are equally
accumulated or not, is usually energy-dependent, except perhaps where
Donnan equilibria exist. Adsorption, whether by ionic forces or co-
GEORGE G. LATIES
respiratory changes which occur when disks are aged in air are a prerequisite to the absorption of water by these tissues. Just as lithium, and
to some extent rubidium, prevent these respiratory changes in chicory
(Laties, 1954, and in press), so rubidium prevents or delays the
ability of artichoke disks to absorb water in response to auxin (Hanson
and Bonner, 1955). Since the respiratory changes which occur during
incubation occur independently of the presence of auxin, those changes
cannot in themselves result in metabolic water uptake. Hackett and
Thimann (1952a) have presented an interesting experiment which suggests that certain preliminary auxin-dependent metabolic events, which
in potato disks lead ultimately to the subsequent absorption of water in
response to auxin, may go on at a lower oxygen concentration than that
which permits water absorption. Disks kept for 6 days in 7% 0 2 -93% N 2
(a condition excluding appreciable water uptake) when transferred to
air, immediately absorb water at a rate equal to the maximum rate
evinced by disks which had been kept continuously in air.
In conclusion, it may be said that the obligatory relationship between
auxin-induced growth and respiration is not restricted to the visible stages
of growth. In some tissues (Avena, Bonner, 1949; potato, Hackett and
Thimann, 1952a, 1953; carrot, Steward et al, 1952) an auxin-induced
increase in respiration accompanies cell enlargement, while in other
tissues (tobacco pith, Newcomb, 1954) an auxin-induced stimulation
of respiration precedes visible growth. These observations favor the
previously stated contention that water movement into growing cells is
osmotic, and that the effect of respiration on growth is to supply energy
for the endergonic reactions which bring about plasticization of the
cell wall.
3. The Relation of Salt Absorption to Respiration
The mechanisms of ion absorption and accumulation have been much
discussed of late. A survey nf the extensive literature, together with discussions of the salient aspects of salt movement into cells and tissues,
may be obtained from reviews by Sutcliffe (1954), Lundegárdh (1955a),
Epstein (1956), Kramer (1956a), and Robertson (1956), and from the
volume edited by Clarke and Nachmansohn (1954) dealing with ion
transport across membranes.
The simultaneous accumulation of both members of an ion pair when
the latter are freely dissociated within the cell is a process clearly dependent upon the respiratory metabolism. In the higher plants the
dependence is, more specifically, upon the aerobic respiration. Accumulation of ions, whether both members of a salt pair are equally
accumulated or not, is usually energy-dependent, except perhaps where
Donnan equilibria exist. Adsorption, whether by ionic forces or co-