ORGANIZED DEVELOPMENT IN PLANTS
57
the procedure used by Steward and others on liquid cell suspension cultures; it was also used successfully by Bergmann (1960).
In order to understand what makes an isolated cell undergo division
and follow a particular course in the development of a multicellular structure, it is important to know in specific detail what an isolated cell needs
from its environment before it can develop. Bergmann (1960) worked out
the technique which made such a study feasible with higher plant cells.
He adapted the well-established procedure of cell plating, used in
microbial studies, to the filtered cell suspensions of callus tissue cells.
He was able to plate out filtered cell suspensions from carrot
(Daucus)
and bean (Phaseolus)
callus cultures onto an agar plate poured with a
coconut-milk nutrient medium. Under the microscope he was able to
follow the divisions of single isolated cells into two cells, then filaments,
and finally cell colonies. His plating technique was successful because he
used cells in suspension in the midst of their dividing phase and plated
them out on a complex medium which provided favorable concentrations
of all the essential nutrients the cells needed (i.e., were unable to synthesize) or might otherwise have lost to the medium. In addition, he provided them with stimulants to cell division. The same procedure was
used by Blakely (1964) and Blakely and Steward (1964) in a detailed
study of the fate of single cells in culture and their progress toward cell
colony formation. Using this technique, Gibbs and Dougall (1963) have
reported that they were able to achieve division of up to 100% of the
plated cell suspension units, i.e., filtered cells or small aggregates of cells.
Reinert (1963) described successful culture in a synthetic medium of
single isolated cells derived from crown-gall callus tissue of Vitts vinifera. Using the Bergmann technique, Earle and Torrey (1965a,b) have
devised a completely defined nutrient medium in which cell plating can
be accomplished with a useful plating efficiency with normal cells of
Convolvulus
root callus.
From all these studies one can begin to add up what it takes to make
a single isolated cell divide—and to follow a particular course of development. In the case of Convolvulus there are five major groups of components required. Essential inorganic macro- and micronutrient elements
must, of course, be supplied externally. These may be critical and, if precipitated out of solution by unfavorable pH or made unavailable by chelation by an organic component of the medium, could limit or prevent
cell division and cell colony formation. The tissue also requires an energy
and carbon source for which sucrose serves effectively at relatively low
concentration. Vitamins are also essential. For Convolvulus
root callus,
thiamine must be provided since the isolated root (Bonnett, 1964) and
the callus root tissue (Earle, 1964) do not synthesize it. Another essen-
57
the procedure used by Steward and others on liquid cell suspension cultures; it was also used successfully by Bergmann (1960).
In order to understand what makes an isolated cell undergo division
and follow a particular course in the development of a multicellular structure, it is important to know in specific detail what an isolated cell needs
from its environment before it can develop. Bergmann (1960) worked out
the technique which made such a study feasible with higher plant cells.
He adapted the well-established procedure of cell plating, used in
microbial studies, to the filtered cell suspensions of callus tissue cells.
He was able to plate out filtered cell suspensions from carrot
(Daucus)
and bean (Phaseolus)
callus cultures onto an agar plate poured with a
coconut-milk nutrient medium. Under the microscope he was able to
follow the divisions of single isolated cells into two cells, then filaments,
and finally cell colonies. His plating technique was successful because he
used cells in suspension in the midst of their dividing phase and plated
them out on a complex medium which provided favorable concentrations
of all the essential nutrients the cells needed (i.e., were unable to synthesize) or might otherwise have lost to the medium. In addition, he provided them with stimulants to cell division. The same procedure was
used by Blakely (1964) and Blakely and Steward (1964) in a detailed
study of the fate of single cells in culture and their progress toward cell
colony formation. Using this technique, Gibbs and Dougall (1963) have
reported that they were able to achieve division of up to 100% of the
plated cell suspension units, i.e., filtered cells or small aggregates of cells.
Reinert (1963) described successful culture in a synthetic medium of
single isolated cells derived from crown-gall callus tissue of Vitts vinifera. Using the Bergmann technique, Earle and Torrey (1965a,b) have
devised a completely defined nutrient medium in which cell plating can
be accomplished with a useful plating efficiency with normal cells of
Convolvulus
root callus.
From all these studies one can begin to add up what it takes to make
a single isolated cell divide—and to follow a particular course of development. In the case of Convolvulus there are five major groups of components required. Essential inorganic macro- and micronutrient elements
must, of course, be supplied externally. These may be critical and, if precipitated out of solution by unfavorable pH or made unavailable by chelation by an organic component of the medium, could limit or prevent
cell division and cell colony formation. The tissue also requires an energy
and carbon source for which sucrose serves effectively at relatively low
concentration. Vitamins are also essential. For Convolvulus
root callus,
thiamine must be provided since the isolated root (Bonnett, 1964) and
the callus root tissue (Earle, 1964) do not synthesize it. Another essen-