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Figure 6. Differences among models.Hypothetical stress (left), creep compliance (middle), and deformation (strain, ε; right) in the tissue. (A) The generalized model (Model 1) assumes the relative timing (ô) and the strains, of all events (1, 2, 3,…) are independent of temperature (cool (blue) vs warm (red)), as in a movie played faster. The generalized model does not specify the developmental course of strain or stress, only that timing scales with temperature. The generalized model predicts how stress and compliance vary together as temperature changes (Model 1, eqn.16). (B) Step and ramp models (Models 2A & 2B). The step and ramp models assume morphogenetic stresses are stepped (top) or ramped (bottom) with time. For a step stress (upper), the change in tP with temperature does not affect the time tC to reach strain εC (when the blastopore closes) because peak stress and compliance are unchanged (Model 2A, eqns. 21–22). A ramp is the sum of stress increments (gray lines; bottom left). Stress timing (hence the slope of the ramp) scales with tP, and therefore with temperature (red, warm; blue, cool). The time tC varies with tP (and therefore temperature) for the ramp model (upper; Model 2B, eqns. 25–26), because strain increments follow the change in timing of stress increments (gray lines). Image published in: von Dassow M et al. (2014) Image reproduced on Xenbase with permission of the publisher and the copyright holder. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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