With Emmanuel de Langre and Paul-Henry Cournède, we studied the mechanical response of plants to draught. Water stress on plants is known to induce simultaneous thermal changes in leaves, hydraulic changes in plant flows, and mechanical changes in tissues. The mechanical response is coupled with the hydrous and thermal states, through the inclination of leaves and light interception. We developed a theoretical model of these mechanical couplings to investigate the short term response of an isolated tree to a sudden water stress. Our model results indicate that coupling between mechanics and hydraulics has a protective effect for trees. Leaf wilting may thus be a mechanism that increases water use efficiency and protects the tree from cavitation.