Figure 9.

Growth-induced curvature changes in stalk of rhubarb for different radius-to-length ratios. A decrease in the surface-to-volume growth ratio $\widehat{\vartheta }$ increases tissue tension and induces an increase in relative curvature κ/κ₀. At a relative curvature of κ/κ₀ = 1.0, indicated throughout the solid dots, each stalk forms a closed loop. The surface-to-volume growth ratio $\widehat{\vartheta }$ required to form a closed loop, as shown in Figure 10, bottom row, decreases with increasing radius-to-length ratios, from $\widehat{\vartheta }=0.894$, to $\widehat{\vartheta }=0.887$, $\widehat{\vartheta }=0.872$, $\widehat{\vartheta }=0.853$, and $\widehat{\vartheta }=0.838$, from blue to red.