ORGANIZED DEVELOPMENT IN PLANTS
49
the subsequent stages can be cultured, and something may be gained in
reviewing the present state of knowledge concerning the nutritional control of embryo development from recent work on embryo, ovule, and
ovary culture. An extensive review of plant embryo culture by Narayanaswami and Norstog (1964) has been published recently.
A. Ovary and Ovule Culture
The excision and cultivation of intact ovaries or dissected-out ovules
is relatively simple and can be performed at precisely timed stages
following pollination. Much of this work is directed toward solution of
problems other than that of embryo development. However, it is interesting to find that ovaries or ovules isolated and cultured at the stage
just after fertilization do not necessarily or easily give rise to normal
embryos. Failure of the embryo to develop was common in isolated ovules
of a number of genera unless the embryo had already reached the globular stage. The presence of placental tissue had a beneficial effect on
ovule development and on embryo growth (Chopra and Sabharwal,
1963; Sabharwal, 1963). Kapoor (1959) was able to culture ovules of
Zephyranthus
to maturity when the ovules were isolated with the embryo
at the zygote stage in a coconut-milk medium. Thus, the ovule structure, adequately nourished in vitro, is capable of supporting the development of the zygote to maturity. This is not surprising and points out
that isolation procedures in themselves establish limitations which must
be overcome, here, for example, to provide the normal adequate nutrition of the isolated ovule comparable to its intact state within the ovary.
Melnick et al. (1964) demonstrated that young fertilized ovules of different species, genera, and even families can be transplanted onto the
placenta of fruits of Capsicum and grown to mature seeds, which indicates that the physiological requirements of the ovules are not speciesspecific.
B. Isolated Embryo Culture
According to the work of Rijven (1952) on Capsella and of Rietsema
and Blondel (1959) on Datura, the smaller the embryo at the time of
isolation, the more complex the nutrient requirements, i.e., the more
heterotrophic is the embryo. Thus torpedo-shaped embryos required sugar
and vitamins in addition to an appropriate inorganic nutrient medium.
Heart-stage embryos required these nutrients and, in addition, a list of
some eighteen amino acids. Although these substances were not established critically as required, the evidence favored the idea that preformed organic nitrogen was essential for embryo development. Later,
Rijven (1955, 1956) reported that L-glutamine served as an adequate
49
the subsequent stages can be cultured, and something may be gained in
reviewing the present state of knowledge concerning the nutritional control of embryo development from recent work on embryo, ovule, and
ovary culture. An extensive review of plant embryo culture by Narayanaswami and Norstog (1964) has been published recently.
A. Ovary and Ovule Culture
The excision and cultivation of intact ovaries or dissected-out ovules
is relatively simple and can be performed at precisely timed stages
following pollination. Much of this work is directed toward solution of
problems other than that of embryo development. However, it is interesting to find that ovaries or ovules isolated and cultured at the stage
just after fertilization do not necessarily or easily give rise to normal
embryos. Failure of the embryo to develop was common in isolated ovules
of a number of genera unless the embryo had already reached the globular stage. The presence of placental tissue had a beneficial effect on
ovule development and on embryo growth (Chopra and Sabharwal,
1963; Sabharwal, 1963). Kapoor (1959) was able to culture ovules of
Zephyranthus
to maturity when the ovules were isolated with the embryo
at the zygote stage in a coconut-milk medium. Thus, the ovule structure, adequately nourished in vitro, is capable of supporting the development of the zygote to maturity. This is not surprising and points out
that isolation procedures in themselves establish limitations which must
be overcome, here, for example, to provide the normal adequate nutrition of the isolated ovule comparable to its intact state within the ovary.
Melnick et al. (1964) demonstrated that young fertilized ovules of different species, genera, and even families can be transplanted onto the
placenta of fruits of Capsicum and grown to mature seeds, which indicates that the physiological requirements of the ovules are not speciesspecific.
B. Isolated Embryo Culture
According to the work of Rijven (1952) on Capsella and of Rietsema
and Blondel (1959) on Datura, the smaller the embryo at the time of
isolation, the more complex the nutrient requirements, i.e., the more
heterotrophic is the embryo. Thus torpedo-shaped embryos required sugar
and vitamins in addition to an appropriate inorganic nutrient medium.
Heart-stage embryos required these nutrients and, in addition, a list of
some eighteen amino acids. Although these substances were not established critically as required, the evidence favored the idea that preformed organic nitrogen was essential for embryo development. Later,
Rijven (1955, 1956) reported that L-glutamine served as an adequate