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SUMMARYEmbryoids as embryonic cell masses, globular, heart and torpedo forms were grown on medium in the presence and absence of the growth regulators, 2,4-dichlorophenyoxyacetic acid (2,4-D) and kinetin. The early phase, up to the globular stage of development, was dependent on a supply of 2,4-D and kinetin for continued cell division and growth, whereas the later stages did not require an external supply of growth regulators and their development was in fact inhibited if an external supply was provided. The early dependent phase and the later independent phase in the embryoids corresponded to the heterotrophic and autotrophic phases of embryo development in the intact plant. An analysis of endogenous auxin and cytokinin in the different stages of embryoid development showed a relatively low auxin content with little change at each stage. The cytokinins however showed both quantitative and qualitative changes with an increase in total cytokinin in the mature embryoids and plantlets then a decline in the intact plant.

SUMMARYThe formation of globular, heart-shaped and torpedo-shaped embryoids was initiated in a cell suspension culture of differentiating celery caUus. Sections of these embryoids were examined for cell differentiation. Sections were also taken from plantlets, seedlings and mature plants. No cell differentiation was seen in the globular and heart-shaped stages but cell differentiation and tissue organization were present at the torpedo stage. The structure of the plantlet was simpler than that of the seedling but this may have been due to the conditions in the culture flask. Both plantlet and seedling leaf showed comparable levels of organization. It is concluded that biochemical development in the embryoid may be related to the onset of cell differentiation.