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SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
as a stimulant. In the roots of Allium it has been found that the higher
the ploidy, the higher concentration or the longer growth substance
treatment is needed to induce a differentiated cell to divide (Therman,
1951). The Viennese school (cf. Geitler, 1953; Tschermak-Woess, 1956)
has mainly used wounding to study the cytology of differentiated tissues.
In this case there is no way to intensify the treatment, and as a result
the more highly polyploid cells do not divide. Geitler (1953, p. 48) has
summarized the findings as follows: As a rule, at the utmost, 16-ploid
cells divide; usually the limit is much lower. An exception are the
succulent leaves of certain plants in which 32-ploid cells have been seen
to divide, and the stem of a cactus, Cereus, in which up to 64-ploid
mitoses have been induced by wounding. When cells with a higher than
4C DNA level divide for the first time, they commonly show diplochromosomes or larger bundles of chromatids as a result of the preceding
endoreduplications.
These studies have confirmed the widespread occurrence of somatic
polyploidy in differentiated plant tissues, which earlier had been inferred
from the nuclear sizes. In his review D'Amato (1952) mentions that of
56 plants studied, only two Crinum species, representing the family
Amaryllidaceae, did not show any somatic polyploidy in their differentiated root cells. The corresponding numbers given a few years later by
Tschermak-Woess (1956, p. 812) are as follows: Somatic polyploidy
had been found in 140 species representing 24 families, whereas 39
species seemed to be devoid of it. The presence versus absence of somatic
polyploidy seems to be correlated with taxonomic relationships. For
instance, plants belonging to the family Compositae are, as a rule,
diploid throughout.
3. Cytology of Crown Gall
a. The Beginning Tumor. Therman (1956) described the first cytological reaction around a 2-day-old crown gall wound in Vicia faba: the
nuclei became inflated and better stainable with the Feulgen technique.
This has been confirmed by Kupila (1958) in the 24-hr-old crown
gall wound of the pea, in which in one stem even a number of
mitoses were seen at this stage; these appeared at somewhat later stages
in the tomato and the sunflower. Rasch et al. (1959) have found in the
broad bean that tumor cells differ, as early as 24 hr after the inoculation,
from normal wound cells in a marked increase in nucleolar as well as
nuclear volumes even in 2C cells.
In part these changes reflect DNA synthesis as shown with direct
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
as a stimulant. In the roots of Allium it has been found that the higher
the ploidy, the higher concentration or the longer growth substance
treatment is needed to induce a differentiated cell to divide (Therman,
1951). The Viennese school (cf. Geitler, 1953; Tschermak-Woess, 1956)
has mainly used wounding to study the cytology of differentiated tissues.
In this case there is no way to intensify the treatment, and as a result
the more highly polyploid cells do not divide. Geitler (1953, p. 48) has
summarized the findings as follows: As a rule, at the utmost, 16-ploid
cells divide; usually the limit is much lower. An exception are the
succulent leaves of certain plants in which 32-ploid cells have been seen
to divide, and the stem of a cactus, Cereus, in which up to 64-ploid
mitoses have been induced by wounding. When cells with a higher than
4C DNA level divide for the first time, they commonly show diplochromosomes or larger bundles of chromatids as a result of the preceding
endoreduplications.
These studies have confirmed the widespread occurrence of somatic
polyploidy in differentiated plant tissues, which earlier had been inferred
from the nuclear sizes. In his review D'Amato (1952) mentions that of
56 plants studied, only two Crinum species, representing the family
Amaryllidaceae, did not show any somatic polyploidy in their differentiated root cells. The corresponding numbers given a few years later by
Tschermak-Woess (1956, p. 812) are as follows: Somatic polyploidy
had been found in 140 species representing 24 families, whereas 39
species seemed to be devoid of it. The presence versus absence of somatic
polyploidy seems to be correlated with taxonomic relationships. For
instance, plants belonging to the family Compositae are, as a rule,
diploid throughout.
3. Cytology of Crown Gall
a. The Beginning Tumor. Therman (1956) described the first cytological reaction around a 2-day-old crown gall wound in Vicia faba: the
nuclei became inflated and better stainable with the Feulgen technique.
This has been confirmed by Kupila (1958) in the 24-hr-old crown
gall wound of the pea, in which in one stem even a number of
mitoses were seen at this stage; these appeared at somewhat later stages
in the tomato and the sunflower. Rasch et al. (1959) have found in the
broad bean that tumor cells differ, as early as 24 hr after the inoculation,
from normal wound cells in a marked increase in nucleolar as well as
nuclear volumes even in 2C cells.
In part these changes reflect DNA synthesis as shown with direct