260
H. WALTER AND E. STADELMANN
ε
jz
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o
c
o
(Λ
Ό
JD
ΓΤ
16
14
12
10
8
6
4
2
0
Month
Fig. 28. Change of the rib distance on the south side (
) and north side
(
) of Carnegiea gigantea after rainfall on February 6 (arrow). The expansion
of the stem begins at the south side immediately after rainfall, at the north side,
it is delayed for several days. After data from E. Spalding (Walter, 1931, p. 145).
The water uptake in the cells of the water storage tissue at the south side
causes an increase of the osmotic potential which may become temporarily
higher than that of storage tissue of the north side of the stem (Fig. 29).
These water relations were determined for the water-storage parenchyma
tissue only, and it is not established if such a temporary reversal in the ψ 8
values of the north and south side of the stem occurs in the assimilatory
parenchyma also. Data of only one observation are available (Table X ) .
The φ 8 values on the north and south sides of the stem show reversal for
the water-storage tissue only.
The asymmetry of the isosmotic curves in the stem sections of Carnegiea
gigantea is caused only by the differences in the environmental conditions
between the north and south sides. The vertically growing branches show
the same characteristic rib distribution and ψ 8 values as the main stem
when they are equally exposed in all directions to light and atmosphere.
Branches shadowed on their south side by the main stem or other
branches, however, develop equidistant ribs and have uniform ψ 3 values
throughout the water-storage tissue. Also the columnar cacti in Venezuela,
where the sun shines from the south during the winter and from the north
in the summer, show equal distribution of ribs.
The difference in hydrature between the southwest and the northeast
sides of the columnar cacti from Arizona also leads to differences in distribution of flowers on the apical parts of their stems. Flower buds develop
first, and they open first on the ribs of the southwest side of the plant.
Blooming progresses from the southwest side of the stem in both direc-
H. WALTER AND E. STADELMANN
ε
jz
0)
o
c
o
(Λ
Ό
JD
ΓΤ
16
14
12
10
8
6
4
2
0
Month
Fig. 28. Change of the rib distance on the south side (
) and north side
(
) of Carnegiea gigantea after rainfall on February 6 (arrow). The expansion
of the stem begins at the south side immediately after rainfall, at the north side,
it is delayed for several days. After data from E. Spalding (Walter, 1931, p. 145).
The water uptake in the cells of the water storage tissue at the south side
causes an increase of the osmotic potential which may become temporarily
higher than that of storage tissue of the north side of the stem (Fig. 29).
These water relations were determined for the water-storage parenchyma
tissue only, and it is not established if such a temporary reversal in the ψ 8
values of the north and south side of the stem occurs in the assimilatory
parenchyma also. Data of only one observation are available (Table X ) .
The φ 8 values on the north and south sides of the stem show reversal for
the water-storage tissue only.
The asymmetry of the isosmotic curves in the stem sections of Carnegiea
gigantea is caused only by the differences in the environmental conditions
between the north and south sides. The vertically growing branches show
the same characteristic rib distribution and ψ 8 values as the main stem
when they are equally exposed in all directions to light and atmosphere.
Branches shadowed on their south side by the main stem or other
branches, however, develop equidistant ribs and have uniform ψ 3 values
throughout the water-storage tissue. Also the columnar cacti in Venezuela,
where the sun shines from the south during the winter and from the north
in the summer, show equal distribution of ribs.
The difference in hydrature between the southwest and the northeast
sides of the columnar cacti from Arizona also leads to differences in distribution of flowers on the apical parts of their stems. Flower buds develop
first, and they open first on the ribs of the southwest side of the plant.
Blooming progresses from the southwest side of the stem in both direc-