Study on the formation mechanism of ornamentation patterns in spores and pollen as revealed by finite element method

Abstract

Spores (especially fungal and plant spores) and pollen usually adopt an approximately spheroidal shape and are characterized by variable and distinct ornamentation patterns. However, the mechanisms responsible for the formation of these patterns have not been thoroughly studied. In this study, spores and pollen were simplified into spheroidal core/shell systems. By using finite element method (FEM), the anisotropic stress-driven wrinkles on the systems were evaluated under different ratios of equatorial/polar radii and ratios of effective size/exine thickness, which were in comparison with spore and pollen ornamentation patterns of given species under electron microscopy. We demonstrated that anisotropic stress-driven wrinkles can reproduce various anisotropic patterns of spores and pollen from a mechanical point of view, suggesting that stress is definitely the primary determinant of ornamentation. The ratio of equatorial/polar radii and the ratio of effective size/exine thickness mainly govern the ornamentation patterns. This study provided new insights into the formation and evolution of spores and pollen ornamentation patterns in nature.