Culture of Ovaries of Plants

Culture of Ovaries:

Rau (1956) attempted to culture pollinated ovaries of Phlox drummondii and studied the influence of extraneous chemicals on the pattern of development of the endosperm and embryo.

The addition of colchicine to the medium caused aberrant divisions, fusion and aggregation of endosperm nuclei and finally a degeneration of the endosperm. In 12 to 14-days old cultures the embryo also aborted and the seeds were malformed.

Nirmala Maheshwari and Lal (1961) excised the flowers of Iberis amara one day after pollination and planted them on agar nutrient media. Fruits of normal size were obtained in two weeks on a medium containing Knop’s mineral salts + Nitsch’s trace elements + sucrose + B vitamins.

The seeds formed in vitro contained viable embryos. Removal of the sepals slowed down the growth of the ovaries showing that the calyx is by no means an unessential structure but has an important role in the physiology of the fruit.

Pollinated ovaries of a few other plants have also been reared into fruits, but when unpollinated ovaries are taken, the fruits are either not formed or are seedless.

Johri and Sehgal (1963) cultured the ovaries of Anethum graveolens at the zygote stage on White’s basal medium containing yeast extract and /or casein hydrolysate thirteen to twenty weeks later, a polyembryonate mass developed by the proliferation of the zygotic proembryo and ruptured the pericarp.

Further growth resulted in the production of multiple shoots some of which flowered in the test tube after about seven months. Thus this was possible to obtain several seedlings from a single fertilized ovule.

However, it is easier to maintain ovules in sterile culture when they are left in situ within the ovary. The physiological requirements of fertilized ovules do not appear to be species specific, since young ovules of widely different species have grown to mature seeds following transplantation on to the placenta of Capsicum fruits.

Culture of Ovules and Parts of Ovules:

White (1932) was the pioneer to culture the ovules. White and La Rue cultured ovules of Erythronium and Antirrhinum on White basic medium containing indole acetic acid lAA.

Nirmala Maheshwari and Lal (1961) cultured the ovules of Papaver somniferum excised six days after pollination when they contained only a 2-celled proembryo and a free nuclear endosperm. These grew to maturity in twenty days and even germinated and produced seedlings in the culture tubes.

Several genera, such as Citrus, Eugenia and Mangifera show the occurrence of nucellar embryos. Since they have the same genetical composition as the maternal parent, they are of much importance for the clonal propagation of desirable varieties.

Rangaswamy (1961) reported that if the nucellar tissue of Citrus microcarpa is grown on a suitable nutrient medium containing casein hydrolysate, it proliferates profusely and on subculturing produces embryo-like regenerants termed “pseudobulbils”, which can develop into seedlings so that an indefinite number of new plants can be obtained from a single nucellus.

A. N. Rao (1963) successfully germinated seeds of an interspecific hybrid of Vanda on a simple agar nutrient medium. Some of the fertilized ovules directly produced seedlings; others gave rise to a callus from which new plants arose subsequently.