58
JOHN G. TORREY
tial vitamin for Convolvulus
cells is myoinositol, which serves an essential but unknown role. No essentiality was demonstrated for nicotinic
acid or pyridoxine or any other of the several vitamins studied in plated
cell suspensions. The fourth essential component was some form of
organic nitrogen—best and most simply provided as L-glutamine, although an appropriate mixture of amino acids and amides also served
effectively. Probably a supply of L-glutamine serves to protect the cells
from deleterious effects of loss by diffusion of amino-nitrogen compounds.
The fifth group of essential components includes compounds which are
hormone-like in their activity : an auxin, such as IAA, a-naphthaleneacetic
acid (NAA), or (2,4-dichlorophenoxy) acetic acid (2,4-D) ; a kinin, such
as kinetin or benzyladenine ; and another purine, adenine sulfate, which
plays an unspecified role perhaps in some way associated with effective
kinin action. Under the best conditions Convolvulus
cell suspensions
plated on the synthetic medium showed 30% of the cell units forming
cell colonies. The addition of complex mixtures such as yeast extract to
the medium increased the plating efficiency somewhat, so there may well
be one or more other hormone-like substances not yet identified. Improvements in techniques of preparing cell suspensions and in preparing
the medium may lead in the future to plating efficiencies on synthetic
media approaching 100%.
As will be discussed later, cell colonies of Convolvulus which developed
on synthetic medium were capable of initiating organized shoots or roots,
depending on the hormonal constitution of the medium. It should be
possible from what is now known to devise a similar, completely defined, synthetic medium for wild carrot cells which will give rise to
embryos. On the other hand, it should be equally possible to manipulate
Convolvulus
cells in such a way that they will form normal embryos
from the early globular structures they have already been observed to
form as they develop into cell colonies.
In comparing the embryo culture studies reviewed briefly above with
the cell suspension studies, it is a striking fact that the two quite independent lines of research come together, even to specific detail as to
nutrient culture requirements. The specific nutrient requirements for
Capsella embryos are remarkably close to those for plated
Convolvulus
cells. Clearly, the major categories of essential metabolites and hormones
have been provided in these media. In both cases, the isolation of heterotrophic structures has determined the requirements for mineral salts,
carbohydrate, and organic nitrogen. In the intact system these requirements are met by the surrounding tissues. One of the still unanswered
questions is whether the honnones provided in vitro are in this same
general category. As will be pointed out repeatedly in subsequent discus-
JOHN G. TORREY
tial vitamin for Convolvulus
cells is myoinositol, which serves an essential but unknown role. No essentiality was demonstrated for nicotinic
acid or pyridoxine or any other of the several vitamins studied in plated
cell suspensions. The fourth essential component was some form of
organic nitrogen—best and most simply provided as L-glutamine, although an appropriate mixture of amino acids and amides also served
effectively. Probably a supply of L-glutamine serves to protect the cells
from deleterious effects of loss by diffusion of amino-nitrogen compounds.
The fifth group of essential components includes compounds which are
hormone-like in their activity : an auxin, such as IAA, a-naphthaleneacetic
acid (NAA), or (2,4-dichlorophenoxy) acetic acid (2,4-D) ; a kinin, such
as kinetin or benzyladenine ; and another purine, adenine sulfate, which
plays an unspecified role perhaps in some way associated with effective
kinin action. Under the best conditions Convolvulus
cell suspensions
plated on the synthetic medium showed 30% of the cell units forming
cell colonies. The addition of complex mixtures such as yeast extract to
the medium increased the plating efficiency somewhat, so there may well
be one or more other hormone-like substances not yet identified. Improvements in techniques of preparing cell suspensions and in preparing
the medium may lead in the future to plating efficiencies on synthetic
media approaching 100%.
As will be discussed later, cell colonies of Convolvulus which developed
on synthetic medium were capable of initiating organized shoots or roots,
depending on the hormonal constitution of the medium. It should be
possible from what is now known to devise a similar, completely defined, synthetic medium for wild carrot cells which will give rise to
embryos. On the other hand, it should be equally possible to manipulate
Convolvulus
cells in such a way that they will form normal embryos
from the early globular structures they have already been observed to
form as they develop into cell colonies.
In comparing the embryo culture studies reviewed briefly above with
the cell suspension studies, it is a striking fact that the two quite independent lines of research come together, even to specific detail as to
nutrient culture requirements. The specific nutrient requirements for
Capsella embryos are remarkably close to those for plated
Convolvulus
cells. Clearly, the major categories of essential metabolites and hormones
have been provided in these media. In both cases, the isolation of heterotrophic structures has determined the requirements for mineral salts,
carbohydrate, and organic nitrogen. In the intact system these requirements are met by the surrounding tissues. One of the still unanswered
questions is whether the honnones provided in vitro are in this same
general category. As will be pointed out repeatedly in subsequent discus-