ORGANIZED DEVELOPMENT IN PLANTS
55
and then plants. Such plants always showed the normal diploid chromosome number, although numerous cytological abnormalities, differences
in chromosome numbers, etc., would be found in the callus tissue grown
on coconut-milk medium (Mitra et al., 1960; Mitra and Steward, 1961;
Reinert and Torrey, 1961). In the more recent studies of Steward et al.
(1964) with embryos from carrot callus, a high proportion of cells went
on to form more or less normal embryos or embryoids (embryo-like
meristematic masses), and one must assume that in a high proportion
of such cells the normal genome was expressing itself. On the present
evidence one can conclude that to a remarkable degree viable differentiated somatic plant cells retain the capacity to form the whole organism when given the opportunity by experimental manipulation.
Somehow related to the phenomenon of embryo development from
disorganized tissue cultures are the observations of Waris (1959, 1962)
on the initiation of numerous, rather deformed plantlets from seedlings
of certain species of the family Umbelliferae which have been given
prolonged immersion in rather concentrated solutions of certain amino
acids. The high concentrations of the amino acid led to death of some tissues of the seedlings of Oenanthe, but after months in continued culture
new meristematic centers developed and formed plants with distorted
vegetative structures. Although detailed anatomical studies of this
material have not been made, the so-called "neomorphs" look very much
like the embryoids figured by Reinert (1959), by Steward et al. (1964),
and by Halperin and Wetherell (1964) for wild carrot. It is a matter of
considerable interest that these responsive genera all belong together in
the same family. To this list may be added Anethum studied by Johri
and Sehgal (1963). It should be noted that high levels of casein hydrolyzate especially favored adventive embryo formation in
Anethum.
Waris (1962) illustrated embryonic structures remarkably similar to
globular precursors of embryos. The perpetuation of abnormal development of the embryoid structures even after removal of the inciting concentrated amino acid is interpreted by Waris as a permanent change
which appeared to be correlated with an increased chromosome number.
In a sense, Waris achieved physiological isolation of cells in the population of the whole plant when parts of the original plant structure became necrotic and died. This process may be an essential part of his
successful treatment. Further studies bringing together tissue culture
procedures with those employed by Waris for seedling culture should
make possible a clear interpretation of the relationship between these
two different types of systems.
Increases in chromosome number associated with endomitotic reduplication in somatic cells, a common occurrence in plant cell differentiation
55
and then plants. Such plants always showed the normal diploid chromosome number, although numerous cytological abnormalities, differences
in chromosome numbers, etc., would be found in the callus tissue grown
on coconut-milk medium (Mitra et al., 1960; Mitra and Steward, 1961;
Reinert and Torrey, 1961). In the more recent studies of Steward et al.
(1964) with embryos from carrot callus, a high proportion of cells went
on to form more or less normal embryos or embryoids (embryo-like
meristematic masses), and one must assume that in a high proportion
of such cells the normal genome was expressing itself. On the present
evidence one can conclude that to a remarkable degree viable differentiated somatic plant cells retain the capacity to form the whole organism when given the opportunity by experimental manipulation.
Somehow related to the phenomenon of embryo development from
disorganized tissue cultures are the observations of Waris (1959, 1962)
on the initiation of numerous, rather deformed plantlets from seedlings
of certain species of the family Umbelliferae which have been given
prolonged immersion in rather concentrated solutions of certain amino
acids. The high concentrations of the amino acid led to death of some tissues of the seedlings of Oenanthe, but after months in continued culture
new meristematic centers developed and formed plants with distorted
vegetative structures. Although detailed anatomical studies of this
material have not been made, the so-called "neomorphs" look very much
like the embryoids figured by Reinert (1959), by Steward et al. (1964),
and by Halperin and Wetherell (1964) for wild carrot. It is a matter of
considerable interest that these responsive genera all belong together in
the same family. To this list may be added Anethum studied by Johri
and Sehgal (1963). It should be noted that high levels of casein hydrolyzate especially favored adventive embryo formation in
Anethum.
Waris (1962) illustrated embryonic structures remarkably similar to
globular precursors of embryos. The perpetuation of abnormal development of the embryoid structures even after removal of the inciting concentrated amino acid is interpreted by Waris as a permanent change
which appeared to be correlated with an increased chromosome number.
In a sense, Waris achieved physiological isolation of cells in the population of the whole plant when parts of the original plant structure became necrotic and died. This process may be an essential part of his
successful treatment. Further studies bringing together tissue culture
procedures with those employed by Waris for seedling culture should
make possible a clear interpretation of the relationship between these
two different types of systems.
Increases in chromosome number associated with endomitotic reduplication in somatic cells, a common occurrence in plant cell differentiation