Mechanical behaviour of plant tissues: Composite materials or structures?

The mechanical characteristics of the strengthening tissue of young axes of Aristolochia macrophylla were studied in successive loading-unloading cycl es in tension. Elastic, viscoelastic and plastic deformations could be dist inguished. After the first cycle, the material was in a state different fro m its original state, to which it returned only partially and/or slowly. In ternal 'microstructural' prestresses are considered as an explanation for t he mechanical behaviour seen in Aristolochia macrophylla and several other plants.