New dimensions in palaeobotanical research: ultrastructural studies on plant fossils

Abstract

In recent years palaeobiology has developed from a primarily descriptive science into a technically advanced and intellectually attractive field, with ramifications applicable to phylogeny, evolution, taphonomy and palaeoclimate. A combination of light microscopy (LM) with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) is often used in the study of fossilised organs and organelles. Details of the surface microtopography, which can be seen only through SEM provide evidence of taphonomic processes and influences. Ultrastructural investigation of palynofossils can help resolve a number of problems concerning the interpretation of morphology, development and biology of fossil spores and pollen, and provide new significant data about their systematics. Studies of fine structure of fossil plant cuticles can be help determine the degree of cuticle preservation and organisation of structural components, and interpret the physical environment in which the plants lived and thrived. Ultrastructural studies of fossil plant cuticle may also reveal the presence of delicate structures such as infection pegs formed as a result of fungal infection or changes in the ultrastructure of the cuticle proper due to fungal infection. SEM study of Late Cretaceous fusainised angiosperm flowers has enabled their identification in terms of modern orders and families, thus greatly improving our knowledge of angiosperm evolution and radiation. SEM study of fossil charcoals (fusain) is also useful in understanding the past role of wildfire and ancient fire-prone plant communities.