Usually shoot tips and nodal segments (3rd and 4th nodes) are used as explants. Cytokinins (e.g.. BAP) are used in culture medium to promote the formation of axillary branches by overcoming the phenomenon of apical dominance. Therefore, they support multiple shoot development from each explant. The technique also called as multiple shoot culture.
Such shoots develop more easily over nodal segments. For developing multiple shoots from shoot tips, salt and NAA are often added to culture medium. Shoots of 2- 3 cm are excised and transferred to medium rich in auxin for induction of rooting. The plantlets thus obtained are subjected to hardening and ultimately established in the field.
Meristem cultures are used for rapid clonal multiplication, for production of virus free plants, for germplasm conservation and for production of transgenic plants.
Excision of young embryos from developing seeds and their development on culture medium is called embryo culture. The embryo culture allows the young embryos to complete development and ultimately give rise to seedlings. Applications are:
1. Embryo rescue:
i.e., taking out the fragile embryos from fertilised ovules of interspecific crosses before their abortion and culturing them to form viable hybrid seedlings, e.g.. Tomato (Lycopersicon peruvianum x L. lycopersicuni). Bean (Phaseolus vulgaris x P. angustissimus) etc.
Orchids lack stored food. Empbryo culture allows seedling development from most of the embryos. This method in orchids also used for rapid clonal propagation.
3. Dormant seeds:
Seeds in some species may remain dormant due to presence of inhibitors in the endosperm or seed coat. Embryo culture allows the embryo to develop into seedlings by eliminating the inhibitors and the dormancy.
4. Rare plants:
Embryo culture is useful in multiplication of some rare plants e.g., Makapuno nut.