V. NEW APPROACH TO WATER RELATIONS OF DESERT PLANTS
253
TABLE V I I I
GROWTH AND W A T E R SUPPLY OF Hordeum
a
Water
supply
(mm)
157
257
307
357
Osmotic
potential
6
Ψ.
(atm)
- 3 0 . 0
- 2 9 . 1
- 2 6 . 5
- 2 5 . 7
Fraction
contributed
to NaCl
c
(atm)
- 8 . 1
- 7 . 3
- 7 . 1
- 6 . 7
Root
length
(cm)
35
33
30
25
Plant
height
(cm)
20
27
29
34
a After Abd El Rahman et al. (1966, pp. 265-266).
6 At the end of the vegetation period.
c Indicates that fraction of the osmotic potential which can be attributed to the
osmotic activity of NaCl found in the press sap and determined quantitatively.
field experiments with Hordeum vulgäre var. mariutis (Abd El Rahman,
et al, 1966, p. 264ff; Table VIII). The nonirrigated control plot had a
total rainfall of 157 mm; the total water supply to the three irrigated experimental plots corresponded to 257, 307, and 357 mm, respectively. With
decreasing water supply the length of the shoots decreased from 34 to 20
cm, and that of the roots increased from 25 to 35 cm. With an increase in
available water the number of branch roots increased.
A decrease of 40% in dry matter production was found in Trifolium
incarnatum when grown for 25 days at soil moisture of 30% field capacity
and compared with plants cultivated at 80% field capacity (Simonis, 1948,
p. 212). The relative contribution of the stem material to total dry matter
produced was about the same under both conditions. Root growth was
enhanced and leaf growth decreased under dry conditions.
The relation between osmotic potenital ψ 8 and plant yield was first
investigated on Triticum vulgäre (winter wheat, var. Trubilo) by
Stieglitz (1936). The ψ 3 values for the main part of the growth period
(middle of May to July) were considerably lower for 1934 (which had a
dry period during the summer) than for 1933, a year with normal precipitation (Fig. 22). Grain yield in 1934 was only 56% of that in 1933,
and production of straw decreased even more drastically.
Irrigation tests in the Canadian Prairie (Alberta) proved that yield of
various agricultural crops decreased with lowering of mean osmotic
potential ψ 8 of the vegetation period (Table IX).
The work of Lobov (1951, p. 27) (see Walter, 1955) on irrigated plots
in the Don region (Russia) and the results of Kreeb (1957) also confirm
the close relation between ψ 8 and yield.
253
TABLE V I I I
GROWTH AND W A T E R SUPPLY OF Hordeum
a
Water
supply
(mm)
157
257
307
357
Osmotic
potential
6
Ψ.
(atm)
- 3 0 . 0
- 2 9 . 1
- 2 6 . 5
- 2 5 . 7
Fraction
contributed
to NaCl
c
(atm)
- 8 . 1
- 7 . 3
- 7 . 1
- 6 . 7
Root
length
(cm)
35
33
30
25
Plant
height
(cm)
20
27
29
34
a After Abd El Rahman et al. (1966, pp. 265-266).
6 At the end of the vegetation period.
c Indicates that fraction of the osmotic potential which can be attributed to the
osmotic activity of NaCl found in the press sap and determined quantitatively.
field experiments with Hordeum vulgäre var. mariutis (Abd El Rahman,
et al, 1966, p. 264ff; Table VIII). The nonirrigated control plot had a
total rainfall of 157 mm; the total water supply to the three irrigated experimental plots corresponded to 257, 307, and 357 mm, respectively. With
decreasing water supply the length of the shoots decreased from 34 to 20
cm, and that of the roots increased from 25 to 35 cm. With an increase in
available water the number of branch roots increased.
A decrease of 40% in dry matter production was found in Trifolium
incarnatum when grown for 25 days at soil moisture of 30% field capacity
and compared with plants cultivated at 80% field capacity (Simonis, 1948,
p. 212). The relative contribution of the stem material to total dry matter
produced was about the same under both conditions. Root growth was
enhanced and leaf growth decreased under dry conditions.
The relation between osmotic potenital ψ 8 and plant yield was first
investigated on Triticum vulgäre (winter wheat, var. Trubilo) by
Stieglitz (1936). The ψ 3 values for the main part of the growth period
(middle of May to July) were considerably lower for 1934 (which had a
dry period during the summer) than for 1933, a year with normal precipitation (Fig. 22). Grain yield in 1934 was only 56% of that in 1933,
and production of straw decreased even more drastically.
Irrigation tests in the Canadian Prairie (Alberta) proved that yield of
various agricultural crops decreased with lowering of mean osmotic
potential ψ 8 of the vegetation period (Table IX).
The work of Lobov (1951, p. 27) (see Walter, 1955) on irrigated plots
in the Don region (Russia) and the results of Kreeb (1957) also confirm
the close relation between ψ 8 and yield.