ORGANIZED DEVELOPMENT IN PLANTS
77
initiation of leaves and buds at relatively high kinin concentrations.
Thus, the initiation of meristematic tissues and the channeling of their
activity in a particular morphological direction could be controlled by
slight changes of auxin-kinin ratios over a range as small as tenfold
at absolute concentrations of 1 ppm or less. This same type of manipulation of organ initiation has been observed in a number of tissue culture
systems, usually under less well-defined conditions. Skoog and his associates showed also that the initiation of organs under control of interacting growth substances can be modified in tobacco tissues by a variety
of chemical components of the medium, e.g., sugar levels, phosphate,
sources of nitrogen (such as amino acids), and other constituents such
as purines. Certain aspects of this work were reviewed by C. 0. Miller
(1961) and discussed by Steward and Mohan Ram (1961).
A. Root Initiation
Tissues of carrot (Daueus carota L.) have been grown in culture for
many years and studied in many laboratories. Buvat (1941) described
the anatomical origins of root primordia in carrot callus tissue. Gautheret
(1945) reported that addition of IAA at optimum concentration induced
root initiation in callus tissue cultured in vitro. At high auxin levels, no
meristems were initiated, only giant cells. Wiggans (1954) showed that
carrot tissue cultured in vitro could initiate either roots or buds. Root
initiation occurred in the presence of optimum levels of IAA, but bud
initiation was inhibited by auxin. Callus tissue, which had been cultured
in a medium containing adenine, would initiate buds after the tissue was
transferred to a medium lacking adenine. Such studies foreshadowed the
successful manipulations of carrot callus tissue in vitro achieved by
Steward and Shantz (1955), who reported root initiation in carrot callus
tissue cultured in complex nutrient medium. It was only a step further to
so manipulate the development of carrot tissues cultured in vitro by control of the chemical and physical environment that patterns of cell
division would lead to the embryonic structures described by Reinert
(1959), and in wild carrot by Steward et al. (1964) and Halperin and
Wetherell (1964).
Root initiation in callus tissue has been reported in a number of
different tissues in addition to carrot callus: in Topinambour
(Gautheret,
1961), in endive (Gautheret, 1961; Vasil et al., 1964), in
Armoracia
rusticana
(Sastri, 1963), in Pisum sativum
(Torrey and Shigemura,
1957), and in Convolvulus
arvensis L. (Earle and Torrey, 1965b).
Root initiation in stem or callus tissue in vitro is subject to a number of limiting factors, as is true also of lateral root initiation in
isolated roots grown in culture. In studies of root initiation in isolated
77
initiation of leaves and buds at relatively high kinin concentrations.
Thus, the initiation of meristematic tissues and the channeling of their
activity in a particular morphological direction could be controlled by
slight changes of auxin-kinin ratios over a range as small as tenfold
at absolute concentrations of 1 ppm or less. This same type of manipulation of organ initiation has been observed in a number of tissue culture
systems, usually under less well-defined conditions. Skoog and his associates showed also that the initiation of organs under control of interacting growth substances can be modified in tobacco tissues by a variety
of chemical components of the medium, e.g., sugar levels, phosphate,
sources of nitrogen (such as amino acids), and other constituents such
as purines. Certain aspects of this work were reviewed by C. 0. Miller
(1961) and discussed by Steward and Mohan Ram (1961).
A. Root Initiation
Tissues of carrot (Daueus carota L.) have been grown in culture for
many years and studied in many laboratories. Buvat (1941) described
the anatomical origins of root primordia in carrot callus tissue. Gautheret
(1945) reported that addition of IAA at optimum concentration induced
root initiation in callus tissue cultured in vitro. At high auxin levels, no
meristems were initiated, only giant cells. Wiggans (1954) showed that
carrot tissue cultured in vitro could initiate either roots or buds. Root
initiation occurred in the presence of optimum levels of IAA, but bud
initiation was inhibited by auxin. Callus tissue, which had been cultured
in a medium containing adenine, would initiate buds after the tissue was
transferred to a medium lacking adenine. Such studies foreshadowed the
successful manipulations of carrot callus tissue in vitro achieved by
Steward and Shantz (1955), who reported root initiation in carrot callus
tissue cultured in complex nutrient medium. It was only a step further to
so manipulate the development of carrot tissues cultured in vitro by control of the chemical and physical environment that patterns of cell
division would lead to the embryonic structures described by Reinert
(1959), and in wild carrot by Steward et al. (1964) and Halperin and
Wetherell (1964).
Root initiation in callus tissue has been reported in a number of
different tissues in addition to carrot callus: in Topinambour
(Gautheret,
1961), in endive (Gautheret, 1961; Vasil et al., 1964), in
Armoracia
rusticana
(Sastri, 1963), in Pisum sativum
(Torrey and Shigemura,
1957), and in Convolvulus
arvensis L. (Earle and Torrey, 1965b).
Root initiation in stem or callus tissue in vitro is subject to a number of limiting factors, as is true also of lateral root initiation in
isolated roots grown in culture. In studies of root initiation in isolated