Cover illustration: Secondary growth induces stresses and strains in the tissues of the liana Aristolochia macrophylla (background). In the axes of A. macrophylla, following an increase in the volume of the secondary tissues, the outer sclerenchymatous cylinder ruptures. Two different mechanical tests were undertaken to test the point of failure of the outer cortical cylinders, comprising the outer sclerenchymatous cylinder. In a first experiment, transverse compression loads were applied to the outside of the cortical cylinders (lower left) causing ovalization of the cylinder until failure. In a second set of experiments, radial hydraulic pressure was applied to the inside of the cortical cylinders (lower right), mimicking the mechanical effects of internal growth processes due to secondary vascular growth. The increase in the internal pressure finally led to rupturing of the sclerenchymatous and collenchymatous cortical cylinders. (Images by T Masselter; see Masselter and Speck, pp. 2955-2967.)
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