DIRECT EMBRYOGENESIS FROM FEMALE HAPLOID PROTOPLASTS OF GINKGO-BILOBA L, A MEDICINAL WOODY SPECIES

Haploid protoplasts isolated from prothallus (i.e. female gametophyte) of Ginkgo biloba, at densities ranging from 5x10(4) to 10(5) protoplasts per milliliter, were able to divide and form microclones which directly evolved into embryos, when they were cultured in two different liquid media. These were : the Murashige and Tucker medium (1969) modified by omitting ammonium ions and supplementing with glutamine, benzyladenine and various levels of naphthaleneacetic acid ; or the Bourgin and Nitsch medium (1967) without growth regulators, supplemented with coconut milk. Three months later, the number of embryos ranged from 165 to 1900 embryos ml-1 depending on the culture medium. After four months, embryos at whatever stage (globular, oblong or heart) exhibited a slow growth, which delayed the transfer onto solid media.