Figure 4.

Process of finite-element (FE) simulation. (a) The outline of the leaf section and the bulliform cells were directly transferred from a microscopic image. (b) Pre-stresses in the leaf tissues are responsible for the folding of the leaf in the event of a drought-stress-induced volume reduction in the bulliform cells. To reproduce this effect in the numerical model, an external horizontal force is applied to the outer edge of the leaf segment considered here. (c) The geometry in a closed position serves as the starting point for the subsequent FE simulation. (d) An increase in pressure, exclusively in the bulliform cells, causes an increase in the opening angle of the leaf lamina.