Plants of many species, in quite different lineages, are characterized by the regular production of hollow stems with septate nodes; bamboos are classical examples, as are horsetails (the genus Equisetum). Among species of the grass or bamboo family, hollow stems predominate over solid stems; among species of the ancient horsetail family, all extant species produce hollow stems. In order to examine the biomechanical properties of hollow stems, Dr. Karl Niklas of Cornell University will use an engineering technique known as multiple resonance frequency spectra (MRFS) analysis in the study of several species of horsetails and of grasses. The mechanical rigidity, or flexural rigidity, of stems is thought to be related to light-interception and to reproduction (either spores or seeds borne on that stem). At issue is the hypothesized trade-off between efficiency in construction (hollow stems presumed to be "cheaper" metabolically) and safety from breakage (solid stems presumed to provide greater strength). The mechanical properties of stems will be analyzed, and aspects of rigidity quantified and measured, in an array of species from the grass and horsetail families. Common features of hollow-stem construction in these two phyletically distant groups of plants may well provide examples of convergent evolution.
