[The dependence of the differentiation potentials of fragments of the marginal zone in early gastrulas of the clawed toad on their morphogenetic movements].

Using Xenopus early gastrulae, we studied the dependence of differentiation potential of tissue fragments explanted from different regions of the marginal zone on the conditions promoting or preventing convergent-intercalation movements (CIM). Previously it has been shown that CIM are stimulated by surface tension usually produced in the embryo by folding (involuting) edge of cell layer. In the first experimental series, we prevented involution of tissue explanted from the region above blastopore by enveloping it in ectoderm of more advanced developmental stages. As the result, percentage of axial organs developed in such explants drastically decreased, whereas that of more ventral structures increased. In the second experimental series, an increase in percentage of axial structures that differentiated in tissue fragments explanted from the lateral part of marginal zone was achieved by stimulating involution of its dorsal edge. In the third series, it was shown that percentage of axial structures formed in ventral halves of embryos becomes significantly greater under the conditions that stimulate stretching of the surface and involution of the free edge of explants. A conclusion is drawn that regional specificity of differentiation potential, which is observed within the marginal zone, greatly depends on surface tension in the explants and, therefore, on morphogenetic movements proceeding in them.