ORGANIZED DEVELOPMENT IN PLANTS
79
in callus cultures from elm (Gautheret, 1942) and work of Buvat (1944,
1945) on bud initiation in callus from roots of chicory
(Cichorium).
Bud initiation was described also in callus tissue cultures of Crambe
maritima (Camus, 1949), in Ulmus (Jacquiot, 1951), in Sequoia
sempervirens (Ball, 1950), in Daucus carota (Levine, 1947; Steward et al.,
1958; and Pilet, 1961), in Convolvulus
arvensis root callus (Earle and
Torrey, lS65b), and in other callus tissues derived from normal plants
[in Solanum tuberosum
(Fellenberg, 1963), Pelargonium
and
Cyclamen
(Mayer, 1956; Stichel, 1959), and others (Wurm, I960)]. Organ initiation, especially of buds and leaves, had been described in a number of
tumorous tissues and teratomata derived from callus of crown-gall origin
or from genetic tumors (cf. review of Braun and Stonier, 1958; Kehr and
Smith, 1954; Kupila, 1963; Hagen et al, 1961; Hagen, 1962). Anatomical
analyses are included in some of these studies. A review of shoot morphogenesis, particularly with respect to the anatomical aspects, was
recently completed by Cutter (1965).
In all of the diverse cases of bud or leaf initiation in callus tissues,
one is concerned once again with the fundamental problem of the causal
basis for the first setting aside of cell lineages directed to a newly
organized meristematic center. The problem is not fundamentally different from those discussed above, and the evidence points to the general
conclusion that the initial steps are under control of the same physiological parameters as those active in root initiation, in the initiation of
vascular tissues, or the initiation of embryoids in vitro.
Anatomical studies by Sterling (1951) of bud initiation in tobacco
stem segments showed that buds originated in relation to existing differentiated vascular tissues, i.e., internal or external phloem or from callus
derived from phloem. Although nests of meristematic cells giving rise to
centers of mature xylem and phloem tended to occur internal to the
surface, bud primordia were formed close to the callus surface. In
studies of organ initiation in carrot callus tissue derived from cell suspension cultures, Steward et al. (1958) described the initial development
of internally located vascular tissue in nests of cells and the origin of
root primordia from such cell aggregates. When such fragments with
roots were transferred to agar medium, organized shoots with leaves developed. Detailed ontogenetic studies of this phase of bud initiation
were not made, so that it was not possible to relate the shoot primordia
to other existing structures. In his anatomical studies, Buvat (1944)
illustrated a sequence in the initiation of buds in callus tissue of chicory
which was remarkably similar to the sequence described in its early
stages by Reinert for embryo initiation in carrot callus, or for early
responses to kinin-auxin treatment described by Das et al. (1956). A
79
in callus cultures from elm (Gautheret, 1942) and work of Buvat (1944,
1945) on bud initiation in callus from roots of chicory
(Cichorium).
Bud initiation was described also in callus tissue cultures of Crambe
maritima (Camus, 1949), in Ulmus (Jacquiot, 1951), in Sequoia
sempervirens (Ball, 1950), in Daucus carota (Levine, 1947; Steward et al.,
1958; and Pilet, 1961), in Convolvulus
arvensis root callus (Earle and
Torrey, lS65b), and in other callus tissues derived from normal plants
[in Solanum tuberosum
(Fellenberg, 1963), Pelargonium
and
Cyclamen
(Mayer, 1956; Stichel, 1959), and others (Wurm, I960)]. Organ initiation, especially of buds and leaves, had been described in a number of
tumorous tissues and teratomata derived from callus of crown-gall origin
or from genetic tumors (cf. review of Braun and Stonier, 1958; Kehr and
Smith, 1954; Kupila, 1963; Hagen et al, 1961; Hagen, 1962). Anatomical
analyses are included in some of these studies. A review of shoot morphogenesis, particularly with respect to the anatomical aspects, was
recently completed by Cutter (1965).
In all of the diverse cases of bud or leaf initiation in callus tissues,
one is concerned once again with the fundamental problem of the causal
basis for the first setting aside of cell lineages directed to a newly
organized meristematic center. The problem is not fundamentally different from those discussed above, and the evidence points to the general
conclusion that the initial steps are under control of the same physiological parameters as those active in root initiation, in the initiation of
vascular tissues, or the initiation of embryoids in vitro.
Anatomical studies by Sterling (1951) of bud initiation in tobacco
stem segments showed that buds originated in relation to existing differentiated vascular tissues, i.e., internal or external phloem or from callus
derived from phloem. Although nests of meristematic cells giving rise to
centers of mature xylem and phloem tended to occur internal to the
surface, bud primordia were formed close to the callus surface. In
studies of organ initiation in carrot callus tissue derived from cell suspension cultures, Steward et al. (1958) described the initial development
of internally located vascular tissue in nests of cells and the origin of
root primordia from such cell aggregates. When such fragments with
roots were transferred to agar medium, organized shoots with leaves developed. Detailed ontogenetic studies of this phase of bud initiation
were not made, so that it was not possible to relate the shoot primordia
to other existing structures. In his anatomical studies, Buvat (1944)
illustrated a sequence in the initiation of buds in callus tissue of chicory
which was remarkably similar to the sequence described in its early
stages by Reinert for embryo initiation in carrot callus, or for early
responses to kinin-auxin treatment described by Das et al. (1956). A