ENDOGENOUS AUXIN AND CYTOKININ CHANGES DURING EMBRYOID DEVELOPMENT IN CELERY TISSUE-CULTURES

Embryoids 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. Copyright © 1979, Wiley Blackwell. All rights reserved