66
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
which the tumor tissues develop a green color and maintain it even
when the leaf blades lose theirs, Hoffmann and Karsten observed the
amount of chlorophyll to be small in tumor tissue when compared to the
leaf blade. The localization of the chloroplasts in the tumor tissue is
described as characteristic; they appear only in the small growth centers
called the secondary tumor tissue. The tumor chloroplasts are only 3.5 /A
or less in diameter, whereas the normal ones reach a diameter of 10 /i.
Radical changes in the chloroplasts during tumor inception as well as
during the developmental phase have been observed by Gee et al. (1966,
1967; cf. also Hohl, 1961). The disintegration of the lamella system and
the swelling of the grana and the plastid itself is followed by the formation of a number of inclusions in the plastids.
Although the nature of the inclusion bodies in the plastids of the
crown gall tissue has remained unknown, plastids with starch grains
have been observed in the reacting cells around a normal wound (KupilaAhvenniemi, 1966). When the wounded internodes of Vicia faba are
stained with periodic acid Schiff (PAS) reagent the first sign of the
abnormal accumulation of starch is observed after 7-12 hr. At 24 hr it
is evident that the leukoplasts of the pith cells that are affected by the
wound accumulate starch. At 36-48 hr the increased cell proliferation
in the cortex is accompanied by an increase in the starch content. The
starch grains remain small and do not fill the leukoplasts. At a later
stage, the impression is obtained that some plastids break down releasing
the grains which become attached to the walls. The accumulation of
starch suggests that the plant is continuously transporting more material
to the wounded area than is required for cell division and growth. Unpublished investigations in the laboratory of Kupila-Ahvenniemi have
indicated that the accumulation of the PAS-staining material takes place
in the wounded tissue of the tulip also. Since crown gall tumors cannot
be produced in this plant, or other monocots, it seems probable that the
observed accumulation of the polysaccharide has no close connection to
the phenomenon of the cell conditioning.
2. Cytology of the Differentiated
Cells and of the Effects of Wounding
For 40 years, attention has been paid to the fact that the nuclei in
the cells of many differentiated tissues vary in size, the volumes often
forming series of multiples of the size of the diploid nuclei. This variation
reflects to some extent different levels of polyploidy, although it is known
that other factors besides the chromosome number influence the nuclear
size. The ploidy levels are best expressed as DNA classes, 2C representing
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
which the tumor tissues develop a green color and maintain it even
when the leaf blades lose theirs, Hoffmann and Karsten observed the
amount of chlorophyll to be small in tumor tissue when compared to the
leaf blade. The localization of the chloroplasts in the tumor tissue is
described as characteristic; they appear only in the small growth centers
called the secondary tumor tissue. The tumor chloroplasts are only 3.5 /A
or less in diameter, whereas the normal ones reach a diameter of 10 /i.
Radical changes in the chloroplasts during tumor inception as well as
during the developmental phase have been observed by Gee et al. (1966,
1967; cf. also Hohl, 1961). The disintegration of the lamella system and
the swelling of the grana and the plastid itself is followed by the formation of a number of inclusions in the plastids.
Although the nature of the inclusion bodies in the plastids of the
crown gall tissue has remained unknown, plastids with starch grains
have been observed in the reacting cells around a normal wound (KupilaAhvenniemi, 1966). When the wounded internodes of Vicia faba are
stained with periodic acid Schiff (PAS) reagent the first sign of the
abnormal accumulation of starch is observed after 7-12 hr. At 24 hr it
is evident that the leukoplasts of the pith cells that are affected by the
wound accumulate starch. At 36-48 hr the increased cell proliferation
in the cortex is accompanied by an increase in the starch content. The
starch grains remain small and do not fill the leukoplasts. At a later
stage, the impression is obtained that some plastids break down releasing
the grains which become attached to the walls. The accumulation of
starch suggests that the plant is continuously transporting more material
to the wounded area than is required for cell division and growth. Unpublished investigations in the laboratory of Kupila-Ahvenniemi have
indicated that the accumulation of the PAS-staining material takes place
in the wounded tissue of the tulip also. Since crown gall tumors cannot
be produced in this plant, or other monocots, it seems probable that the
observed accumulation of the polysaccharide has no close connection to
the phenomenon of the cell conditioning.
2. Cytology of the Differentiated
Cells and of the Effects of Wounding
For 40 years, attention has been paid to the fact that the nuclei in
the cells of many differentiated tissues vary in size, the volumes often
forming series of multiples of the size of the diploid nuclei. This variation
reflects to some extent different levels of polyploidy, although it is known
that other factors besides the chromosome number influence the nuclear
size. The ploidy levels are best expressed as DNA classes, 2C representing