242
H. WALTER AND E. STADELMANN
XI. Osmotic Quantities and Importance of Hydrature
for Growth and Xeromorphism
The different terminologies used in the designation of the osmotic
parameters of the plant cell have caused considerable confusion and their
definition is still not yet precisely settled (cf. Stadelmann, 1966, p. 146;
Taylor, 1968). Ursprung and Blum (1916, p. 530) were the first to clearly
point out the meaning of the different osmotic quantities by establishing
the relation
Suction force _
suction force
,,
of the cell
of the cell content
(all indicated in atm)
Since then, osmotic quantities have been named differently. Instead of
"suction force," suction tension was introduced because a "force" cannot
be given in atmospheres. To avoid confusing suction tension of the cell
with the suction tension of the cell content, the latter was designated as
the osmotic value (Walter, 1931, p. llff). Previously the term "osmotic
value" had been introduced to indicate the cell sap concentration
(Ursprung and Blum, 1916, p. 88) and was measured by an isotonic concentration of a standard solute, e.g., glucose or saccharose (Höfler, 1920,
p. 288). Wall pressure was replaced by turgor pressure (P) which is equal
in magnitude and opposite in direction. When the absolute value for the
turgor pressure (P) is used the above equation reads (Walter, 1962,
p. 61):
Suction tension (S) = osmotic value (W) — turgor pressure (P) (3)
Instead of "osmotic value" also the term "potential osmotic pressure (ir*)"
was introduced (Kreeb and Borchard, 1967, p. 189).
Meyer (1938, p. 535) developed the concept of a physically not measurable "diffusion pressure" and the equation
DPD = OP - TP
(4)
where DPD is the diffusion pressure deficit, OP is the osmotic pressure,
and TP is the turgor pressure.
Taylor and Slatyer (1961, p. 344) emphasized a need for a thermodynamic terminology in plant water relations. When the matric potential,
which is generally zero for plant cells, is omitted and the new symbols
(Slatyer, 1967, p. 82) are applied, the following equation results:
Ψ = Ψ, + ΨΡ
(5)
H. WALTER AND E. STADELMANN
XI. Osmotic Quantities and Importance of Hydrature
for Growth and Xeromorphism
The different terminologies used in the designation of the osmotic
parameters of the plant cell have caused considerable confusion and their
definition is still not yet precisely settled (cf. Stadelmann, 1966, p. 146;
Taylor, 1968). Ursprung and Blum (1916, p. 530) were the first to clearly
point out the meaning of the different osmotic quantities by establishing
the relation
Suction force _
suction force
,,
of the cell
of the cell content
(all indicated in atm)
Since then, osmotic quantities have been named differently. Instead of
"suction force," suction tension was introduced because a "force" cannot
be given in atmospheres. To avoid confusing suction tension of the cell
with the suction tension of the cell content, the latter was designated as
the osmotic value (Walter, 1931, p. llff). Previously the term "osmotic
value" had been introduced to indicate the cell sap concentration
(Ursprung and Blum, 1916, p. 88) and was measured by an isotonic concentration of a standard solute, e.g., glucose or saccharose (Höfler, 1920,
p. 288). Wall pressure was replaced by turgor pressure (P) which is equal
in magnitude and opposite in direction. When the absolute value for the
turgor pressure (P) is used the above equation reads (Walter, 1962,
p. 61):
Suction tension (S) = osmotic value (W) — turgor pressure (P) (3)
Instead of "osmotic value" also the term "potential osmotic pressure (ir*)"
was introduced (Kreeb and Borchard, 1967, p. 189).
Meyer (1938, p. 535) developed the concept of a physically not measurable "diffusion pressure" and the equation
DPD = OP - TP
(4)
where DPD is the diffusion pressure deficit, OP is the osmotic pressure,
and TP is the turgor pressure.
Taylor and Slatyer (1961, p. 344) emphasized a need for a thermodynamic terminology in plant water relations. When the matric potential,
which is generally zero for plant cells, is omitted and the new symbols
(Slatyer, 1967, p. 82) are applied, the following equation results:
Ψ = Ψ, + ΨΡ
(5)