56
JOHN G. TORREY
(D'Amato, 1952), need not prevent the expression of organized development since such tissues are capable of regeneration of organized shoots.
(A common procedure for producing polyploid plants for horticultural
use is to induce bud formation from callus formed on decapitated stems.)
Polyploid tissues in culture are still capable of forming organized structures at the higher ploidy level, e.g., roots (Torrey, 1965b).
IV. Plant Cell Culture
Division of Single Isolated Cells in Culture
What is the nature of the effect of isolating a cell which allows it to
express itself? Isolation alone is not enough. Root cap cells isolated in a
sterile nutrient medium do not divide (Gautheret, 1933, 1937). The isolated cell must be ready and able to divide, either through its own internal impetus or from an external stimulus or both. Much interest has
centered on the problem of making a single cell in isolation divide. The
problem has been studied intensively by both animal and plant cell
culturists, and with some success. One of the major problems is that cells
are leaky, that is, they tend to lose important cell metabolites by
diffusion to the medium.
1. Nurse
Cultures
One answer is to prevent the cells from losing metabolites rapidly by
diffusion to the medium. This idea led to the technique of Muir et al.
(1954, 1958) of placing a cell on a raft of filter paper above a nurse
callus tissue piece. The cell lost less by diffusion and received nutrients
in a gradient which favored movement of materials upward from the
nurse tissue toward the isolated cell. A similar approach was to reduce
the volume of medium to a minimum and provide the cell with a medium
already "conditioned" by having other cells grow in it (Torrey, 1957;
Jones et al., 1960; see also review by Street and Henshaw, 1963, and
recent studies by Benbadis, 1964).
2. Cell Suspension
Cultures
Another and different answer to the problem of cell loss by diffusion is
to surround isolated cells with proper concentrations of everything they
are going to lose if placed in a dilute medium. This is part of the problem of cell nutrition. To surround cells with coconut milk in a nutrient
medium seems to be one good answer. This complex nutrient and ones like
it (yeast extract or malt extract media) provide the complex mixture of
metabolites (and probably many more) easily lost from cells. This is
JOHN G. TORREY
(D'Amato, 1952), need not prevent the expression of organized development since such tissues are capable of regeneration of organized shoots.
(A common procedure for producing polyploid plants for horticultural
use is to induce bud formation from callus formed on decapitated stems.)
Polyploid tissues in culture are still capable of forming organized structures at the higher ploidy level, e.g., roots (Torrey, 1965b).
IV. Plant Cell Culture
Division of Single Isolated Cells in Culture
What is the nature of the effect of isolating a cell which allows it to
express itself? Isolation alone is not enough. Root cap cells isolated in a
sterile nutrient medium do not divide (Gautheret, 1933, 1937). The isolated cell must be ready and able to divide, either through its own internal impetus or from an external stimulus or both. Much interest has
centered on the problem of making a single cell in isolation divide. The
problem has been studied intensively by both animal and plant cell
culturists, and with some success. One of the major problems is that cells
are leaky, that is, they tend to lose important cell metabolites by
diffusion to the medium.
1. Nurse
Cultures
One answer is to prevent the cells from losing metabolites rapidly by
diffusion to the medium. This idea led to the technique of Muir et al.
(1954, 1958) of placing a cell on a raft of filter paper above a nurse
callus tissue piece. The cell lost less by diffusion and received nutrients
in a gradient which favored movement of materials upward from the
nurse tissue toward the isolated cell. A similar approach was to reduce
the volume of medium to a minimum and provide the cell with a medium
already "conditioned" by having other cells grow in it (Torrey, 1957;
Jones et al., 1960; see also review by Street and Henshaw, 1963, and
recent studies by Benbadis, 1964).
2. Cell Suspension
Cultures
Another and different answer to the problem of cell loss by diffusion is
to surround isolated cells with proper concentrations of everything they
are going to lose if placed in a dilute medium. This is part of the problem of cell nutrition. To surround cells with coconut milk in a nutrient
medium seems to be one good answer. This complex nutrient and ones like
it (yeast extract or malt extract media) provide the complex mixture of
metabolites (and probably many more) easily lost from cells. This is