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SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
Bopp and Leppla (1964) named this the "primary tumor tissue." Certain
single cells in this tissue differentiate into tracheids, and continuing differentiation forms out of such cells tracheid strands. Cell division is rapid
in the apex of these strands giving rise to spherical growth centers. These
growth centers the authors call the "secondary tumor tissue." Inside the
centers only a few cells differentiate into tracheids.
An interesting description of the way different tissues react in
Kalanchoe
has been given by Bopp and Leppla (1964). The tumors
originate mainly in the cortex. The epidermis does not react, and the
conductive tissue is less proliferative than the cortex tissue. Cell rows
originate in the pith, but since similar cell rows arise also after sterile
wounding, the authors do not regard them to be tumor cells. This opinion
is supported by an experiment in which the bacteria are inoculated
through a thin tube straight into the pith so that outer tissues remain
uninfected. According to the authors no tumor effect is visible, although
the wound reaction is strong.
A difference in the reaction rate between different tissues has been
demonstrated by Rasch (1964) who used tritiated thymidine to label the
nuclei in Vicia faba stems. She observed that in 2 days only the nuclei
of the vascular parenchyma adjacent to the path of the needle showed
label, compared to 5-9 days before the cortex or pith revealed incorporation.
Several recent crown gall experiments have been made using the
leaves of different plants. Thus Bopp and Leppla (1964) have investigated the gall development in the leaves of Kalanchoe
daigremontiana
and Lippincott and Heberlein (1965) in the primary leaves of the pinto
bean. The leaves of Kalanchoe contain mesophyll of more or less evensized cells and, under the epidermis, a two-layered hypodermis on both
sides of the leaf. The inoculation causes all the cells around the wound
to divide. In 9-11 days a number of cells, especially in the hypodermal
area, have divided many times forming groups of small cells. The continuous proliferation of these may result in the development of small
protuberances. Conductive tissue differentiates as continuation of the
nearby bundles. This induces rapid cell division which gives rise to
growth centers. Separate tracheid strands appear; later these interconnect and form connections with the original bundles of the leaves.
Sieve elements are also present. At a later stage, bundles containing a
core of xylem elements, a meristematic layer, and an outside phloem,
differentiate in the tumor tissue. The rows of larger cells between the
growth centers lignify.
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
Bopp and Leppla (1964) named this the "primary tumor tissue." Certain
single cells in this tissue differentiate into tracheids, and continuing differentiation forms out of such cells tracheid strands. Cell division is rapid
in the apex of these strands giving rise to spherical growth centers. These
growth centers the authors call the "secondary tumor tissue." Inside the
centers only a few cells differentiate into tracheids.
An interesting description of the way different tissues react in
Kalanchoe
has been given by Bopp and Leppla (1964). The tumors
originate mainly in the cortex. The epidermis does not react, and the
conductive tissue is less proliferative than the cortex tissue. Cell rows
originate in the pith, but since similar cell rows arise also after sterile
wounding, the authors do not regard them to be tumor cells. This opinion
is supported by an experiment in which the bacteria are inoculated
through a thin tube straight into the pith so that outer tissues remain
uninfected. According to the authors no tumor effect is visible, although
the wound reaction is strong.
A difference in the reaction rate between different tissues has been
demonstrated by Rasch (1964) who used tritiated thymidine to label the
nuclei in Vicia faba stems. She observed that in 2 days only the nuclei
of the vascular parenchyma adjacent to the path of the needle showed
label, compared to 5-9 days before the cortex or pith revealed incorporation.
Several recent crown gall experiments have been made using the
leaves of different plants. Thus Bopp and Leppla (1964) have investigated the gall development in the leaves of Kalanchoe
daigremontiana
and Lippincott and Heberlein (1965) in the primary leaves of the pinto
bean. The leaves of Kalanchoe contain mesophyll of more or less evensized cells and, under the epidermis, a two-layered hypodermis on both
sides of the leaf. The inoculation causes all the cells around the wound
to divide. In 9-11 days a number of cells, especially in the hypodermal
area, have divided many times forming groups of small cells. The continuous proliferation of these may result in the development of small
protuberances. Conductive tissue differentiates as continuation of the
nearby bundles. This induces rapid cell division which gives rise to
growth centers. Separate tracheid strands appear; later these interconnect and form connections with the original bundles of the leaves.
Sieve elements are also present. At a later stage, bundles containing a
core of xylem elements, a meristematic layer, and an outside phloem,
differentiate in the tumor tissue. The rows of larger cells between the
growth centers lignify.