BIOMECHANICS OF ISOLATED PLANT CUTICLES

The mechanical properties of isolated cuticles of leaves (Yucca aloifo lia, Clusia fluminensis, Nerium oleander, Hedera helix) and one fruit (Lycopersicon esculentum) were investigated by means of a tensile test . Samples of the leaves and the fruit were cut to identical size (12.5 x 50 mm) and the cuticles were enzymatically isolated, cleaned, and a ir dried. The morphology of the isolated cuticular membranes (CM) was investigated by scanning electron microscopy (SEM) and showed consider able differences. The thickness of the CM was determined by a digital image analysis system and ranged between 2.4 and 13.4 mu m. The CM wer e subjected to a tensile test and the results are presented as stress- strain diagrams. From the latter, Young's moduli were calculated, a me asure for the stiffness which allows the direct comparison of differen t materials. The obtained values ranged between 0.1 and 1.3 GPa. Hydra tion of CM caused a decrease of Young's moduli of about 35-50%. A poss ible role of the cuticle as a factor for the stabilization of plant or gans is discussed.