54
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
The minimum length of time that is required before the bacteria can
cause an effective cell transformation is also of interest. The experiments
of Braun and Mandle (1948) showed that after an incubation period the
active presence of bacteria was necessary for 10 hr at 25°C for any
visible tumors to be produced (cf. also Braun and Stonier, 1958). Lipetz
(1966) reached the conclusion that the time required for the actual transformation process was 8-10 hr and, in addition, a preceding period of
8-10 hr was necessary for the environmental adjustment of the bacteria.
Lippincott et al. (1966) used
3 2
P-labeled bacteria to determine the
exact time after wounding when the cells could effectively be transformed
as well as the time required for the alteration. They found that tumor
initiation could occur in less than 2 hr; the point of 50% tumor initiation, however, was not reached until 16 hr after inoculation. This time
could be shortened to 8.5 hr by pretreatment at 32°C.
IV. Factors Affecting the Developmental Phase
The site of the inoculation in a plant determines the developmental
capacity of the tumors. Thus no tumors are produced in vigorously
growing meristematic tissues, and the impression is obtained from the
descriptions of the tumors that galls growing on the leaves often are
smaller than galls on the stems.
That the morphological characteristics of crown gall tumors are
affected by their position and, thus, the correlative factors of the plant,
has been shown especially by Braun (1953, 1954a) on tobacco. He inoculated the fresh surfaces of the cut internodes with crown gall bacteria
of a moderately virulent strain and observed that the base of the upper
half developed a roundish, more or less smooth-surfaced gall, whereas
the tip of the lower half produced a complex tumor with abnormal leafand budlike structures. When cultivated in vitro the tumor tissues maintain these characteristics. When grafted back to the same type of site,
they grew according to the original pattern. When, however, tissue of a
complex tumor, usually called a "teratoma," was implanted into an internode of an uncut tobacco plant, a roundish, smooth-surfaced tumor resulted. The development of different kinds of outgrowths seems to be dependent on the regenerative power of the plant as well as the virulence of
the bacteria. For example, the sunflower is unable to produce any teratomata.
In this connection a recent report of Chen and Venketeswaran (1965)
is of interest. According to them, the growth type of the teratomata in
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
The minimum length of time that is required before the bacteria can
cause an effective cell transformation is also of interest. The experiments
of Braun and Mandle (1948) showed that after an incubation period the
active presence of bacteria was necessary for 10 hr at 25°C for any
visible tumors to be produced (cf. also Braun and Stonier, 1958). Lipetz
(1966) reached the conclusion that the time required for the actual transformation process was 8-10 hr and, in addition, a preceding period of
8-10 hr was necessary for the environmental adjustment of the bacteria.
Lippincott et al. (1966) used
3 2
P-labeled bacteria to determine the
exact time after wounding when the cells could effectively be transformed
as well as the time required for the alteration. They found that tumor
initiation could occur in less than 2 hr; the point of 50% tumor initiation, however, was not reached until 16 hr after inoculation. This time
could be shortened to 8.5 hr by pretreatment at 32°C.
IV. Factors Affecting the Developmental Phase
The site of the inoculation in a plant determines the developmental
capacity of the tumors. Thus no tumors are produced in vigorously
growing meristematic tissues, and the impression is obtained from the
descriptions of the tumors that galls growing on the leaves often are
smaller than galls on the stems.
That the morphological characteristics of crown gall tumors are
affected by their position and, thus, the correlative factors of the plant,
has been shown especially by Braun (1953, 1954a) on tobacco. He inoculated the fresh surfaces of the cut internodes with crown gall bacteria
of a moderately virulent strain and observed that the base of the upper
half developed a roundish, more or less smooth-surfaced gall, whereas
the tip of the lower half produced a complex tumor with abnormal leafand budlike structures. When cultivated in vitro the tumor tissues maintain these characteristics. When grafted back to the same type of site,
they grew according to the original pattern. When, however, tissue of a
complex tumor, usually called a "teratoma," was implanted into an internode of an uncut tobacco plant, a roundish, smooth-surfaced tumor resulted. The development of different kinds of outgrowths seems to be dependent on the regenerative power of the plant as well as the virulence of
the bacteria. For example, the sunflower is unable to produce any teratomata.
In this connection a recent report of Chen and Venketeswaran (1965)
is of interest. According to them, the growth type of the teratomata in