Morel (1960) noticed that when protocorms of Cymbidium were divided new protocorms were formed from the pieces, whereas if they were not divided, original and regenerated protocorms developed into new plantlets. Morel (1960, 1964) suggested that meristem or shoot tip explants could be used to establish cultures for the clonal propagation of orchids, providing thereby the basis of the method which is now used for many orchid genera. Rates of propagation are improved through the use of slightly more complex media than used by Morel, and by including growth regulators. However, many commercial micropropagation laboratories do not favour the use of protocorms for micropropagation because of the lack of clonal fidelity.
Some orchids not only form protocorms on apical meristems, but also directly on explants such as leaves (Churchill et al., 1971; 1973; Tanaka et al., 1975), or flower stalks (Flamee and Boesman, 1977; Arditti et al., 1977), or they may be formed from callus or callus via suspension cultures (see the section on orchids in Volume 2).
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