Experimental studies have clearly shown that poly embryony can be induced in plants 'in vitro'. From lust twenty years,'it has been clearly established that any cell in capable of developing into embryo under suitable nutri tional environmental conditions. The embryos formed in cultures are called embryoids,
Embryoids are obtained by culturing zygotic embryos of Dendrophthoe falcata, Solanum melangena, nucelius of Citrus sps., root segments of Daucus carota stem segments of Nicotiana leaves of Macldeya cordata, fruit tissues of Cucurbita pepo ana anther of Datura and Oryza sativa.
Butter-cup and carrot plants have proved especially suitable for embryoid formation. Any part of these two plants will form embryoids in tissue culture.
Konar and Nataraja (1969) grew embryoids from young floral buds of Ranunculus scleratus on white's medium. The buds proliferated to form an amorphous mass of tissue called callus. Later, embryoids differentiated from the callus. Addition of coconut milk induced rapid formation of embryoids in the callus. These embryoids independently grew into plantlets.
13-8 Polyembryony in cultured tissues of Ranunculus scleratus.
A - Callused explant.
B - Six-week old culture, showing numerous embryoids
arising from the callus. C - Five-week-old plantlets formed by the embryoids ; D - Portion of the hypocotyl enlarged from C to show
embryoids.
Embryoids from epidermal cells of the hypocotyl have also been observed in carrot.
Guha and Maheswari (1966), for the first time deniim strated the possibility of obtaining embryoids from pollen grains in anther culture of Datura.
This technique has now attracted the attention, because it opens up the possibility of obtaining a large number of haploids in a short time. In cultures, the pollen grains undergo a number of repeated divisions forming multi¬cellular grains each of which bursts open to either form a single embryoid or the tissue may further proliferate resulting into a callus mass. Finally the callus differentiates numerous embryoids or shoots.
In Capsicum annum microspores may give rise to embryoids, either directly or through the formation of callus. Several investigators have shown that enrichment of the medium with growth hormones or yeast extract or coconut milk in conjunction with auxins or cytokinins is essential for callus or embryoid formation in cultured anthers of some species.
