Construction and economy of plant stems as revealed by use of the Bic-method

Abstract

The Bic-method, developed by F. Otto for the investigation and classification of light-weight structures in architecture and then also applied to constructions in nature, can be used for mechanical analysis of plants. It allows statements on tension and pressure stability of plant stems and a direct comparison of stems with different anatomy. The multiplication of the Bic-value by an energy value (construction cost or energy content of the plant organ) results in a dimensionless constructive expenditure value, which is comparable to the value of the construction economy in architecture. This value may then be related to the average lifespan of the plant organ. Stems of Ephedra foeminea, Pachysandra terminalis, and Taxus baccata as well as flower stalks of Cyclamen persicum and Taraxacum officinale are investigated to show the applicability of the method. The lowest Bic- values (highest mechanical stability) are found for the lignified stems of Ephedra and Taxus. The constructive expenditure values are higher in herbaceous than in woody axes; in relation to the average life span the long-living lignified tissues show by far the lowest values. The very high values of the flower-stalks are attributed to the fact that short-lived organs also need a minimum expenditure of materials and energy for their construction.