MORPHOGENESIS OF CROWN
GALL
65
walls of the canals. The significance of this wall structure is not known
and does not at present help in the interpretation of tumor formation.
Gee et al. (1966, 1967) have maintained that the bacterial wall disintegrates and releases fibrillar material into the host cytoplasm. Whether
this phenomenon has anything to do with the type of lysis described by
Stonier (1960) and others is not clear. In any case this interesting claim
ought to be followed up, for instance, by means of autoradiography in
combination with electron microscopy.
An increase in the number of ribosomes during and after the inception
phase has been observed in the crown gall of the sunflower petioles (Gee
et al, 1966, 1967). Earlier, a change in the appearance of mitochondria
has also been reported (Fogelberg et al., 1957), but this has not been
confirmed.
Various kinds of particles have often been described in crown gall
cells (Therman, 1956; Braun and Stonier, 1958; Kupila, 1958,
1963; Rasch et al., 1959). The nature of these particles and their
significance for the tumor formation is not understood. Unfortunately,
most of the studies in which the particles have been described have
been limited either to wounded tissue or to crown gall tissue. The study
by Hohl (1961) forms one of the few exceptions. According to him the
main difference between healthy plant cells and the actively dividing
tumor cambium or parenchymatous tumor cells is to be found in the
plastids. The tumor cells contain not only the normal proplastids and
young chloroplasts but also hypertrophic proplastids, plastids with
invaginations, plastids with inclusion bodies, and degenerated forms.
The most common type of the abnormal plastids exhibit inclusion bodies.
The inclusions appear to be roundish and of more or less homogenous
material which Hohl assumes to be of a proteinaceous nature. The
inclusion bodies have not been observed to divide but they do not inhibit
the division of the plastids. However, the abnormal plastids are by no
means specific for the crown gall cells but appear also in wounded tissue.
They can be seen after 24 hr and their number increases during the first
few days. Since the time when Hohl (1961) described abnormal plastids,
they have repeatedly been observed in crown gall tissue (Albertini et al.,
1961; Gee et al, 1966, 1967).
Further studies on the plastid behavior in crown gall tissue have been
made by Hoffmann and Karsten (1966). They studied the light-grown
and the dark-grown tumors on the young leaves of Bryophyllum.
In
contrast to the report of Lippincott and Heberlein (1965), according to
GALL
65
walls of the canals. The significance of this wall structure is not known
and does not at present help in the interpretation of tumor formation.
Gee et al. (1966, 1967) have maintained that the bacterial wall disintegrates and releases fibrillar material into the host cytoplasm. Whether
this phenomenon has anything to do with the type of lysis described by
Stonier (1960) and others is not clear. In any case this interesting claim
ought to be followed up, for instance, by means of autoradiography in
combination with electron microscopy.
An increase in the number of ribosomes during and after the inception
phase has been observed in the crown gall of the sunflower petioles (Gee
et al, 1966, 1967). Earlier, a change in the appearance of mitochondria
has also been reported (Fogelberg et al., 1957), but this has not been
confirmed.
Various kinds of particles have often been described in crown gall
cells (Therman, 1956; Braun and Stonier, 1958; Kupila, 1958,
1963; Rasch et al., 1959). The nature of these particles and their
significance for the tumor formation is not understood. Unfortunately,
most of the studies in which the particles have been described have
been limited either to wounded tissue or to crown gall tissue. The study
by Hohl (1961) forms one of the few exceptions. According to him the
main difference between healthy plant cells and the actively dividing
tumor cambium or parenchymatous tumor cells is to be found in the
plastids. The tumor cells contain not only the normal proplastids and
young chloroplasts but also hypertrophic proplastids, plastids with
invaginations, plastids with inclusion bodies, and degenerated forms.
The most common type of the abnormal plastids exhibit inclusion bodies.
The inclusions appear to be roundish and of more or less homogenous
material which Hohl assumes to be of a proteinaceous nature. The
inclusion bodies have not been observed to divide but they do not inhibit
the division of the plastids. However, the abnormal plastids are by no
means specific for the crown gall cells but appear also in wounded tissue.
They can be seen after 24 hr and their number increases during the first
few days. Since the time when Hohl (1961) described abnormal plastids,
they have repeatedly been observed in crown gall tissue (Albertini et al.,
1961; Gee et al, 1966, 1967).
Further studies on the plastid behavior in crown gall tissue have been
made by Hoffmann and Karsten (1966). They studied the light-grown
and the dark-grown tumors on the young leaves of Bryophyllum.
In
contrast to the report of Lippincott and Heberlein (1965), according to