Stem extension and mechanical stability in Xanthium

There seems to be a trade-off between height growth and mechanical stability in plants growing in crowded habitats. Watari et al. measure extension growth and mechanical properties of internodes in Xanthium canadense plants grown at different densities and show that tissue stiffness (Young’s modulus of elasticity) and strength (modulus of rupture) play crucial roles in maintaining stability in herbaceous species that lack the capacity for secondary growth. This differs from woody species where diameter growth has been considered more important.