Taxonomic importance of SEM and LM foliar epidermal micro-morphology: A tool for robust identification of gymnosperms

Abstract

The current study reports the implication of scanning electron microscopy (SEM) and light microscopy (LM) epidermal micro-morphological characters in the identification of gymnosperms of Pakistan. A number of characters were found to be of great taxonomic significance and can be used to distinguish different species of gymnosperms with its help. Here, the foliar cuticular features of 44 gymnosperm species were assessed, in which 32 were hypostomatic, 6 were epistomatic and 6 were amphistomatic. Four different types of guard cells were observed, 27 species having crescent shaped, 10 species having rectangular, 5 species having dome-shaped, and 2 species having triangular guard cells. Sunken type stomata were very frequent in all gymnosperm species. 27 species have different types of phytoliths, while in the remaining 17 species no phytoliths were seen. In the current study, we have recognized seven types of Florin rings, named as Type A, Type B, Type C, Type D, Type E and Type F. Three types (Type I, Type II and Type III) of epicuticular wax were also observed in the investigated species. The quantitative character showed diversity and was useful in the complete assessment and key making. A taxonomic key based on these micro-morphological characters was prepared. The study characters (stomatal index, stomatal density, epidermal cell density and stomatal area) were also analyzed by different statistical methods. SEM and LM foliar epidermal studies were found very useful in taxonomic identification. Based on current results we recommend such studies for accurate taxonomic identification and complete phylogeny.