Contents lists available at ScienceDirect Flora journal homepage: www.elsevier.com/locate/flora Taxonomic importance of SEM and LM foliar epidermal micro-morphology: A tool for robust identifcation of gymnosperms Raees Khan a,b, ⁎ , Sheikh Zain Ul Abidin c , Mushtaq Ahmad c , Muhammad Zafar c , Jie Liu d , Lubna c , Shayan Jamshed c , Ömer Kiliç e a Department of Plant Sciences, Quaid-i-Azam University Islamabad, Pakistan b Zoological Survey of Pakistan, Ministry of Climate Change, Pakistan c Department of Plant Sciences, Quaid-i-Azam University Islamabad, Pakistan d Kunming Institute of Botany, Chinese Academy of Sciences, Yunnan, PR China e Department of Park and Garden Plant, Bingol University, Turkey ARTICLEINFO Edited by Alessio Papini Keywords: Taxonomy Gymnosperms Foliar epidermal morphology Florin rings Epicuticular wax Phytoliths ABSTRACT The current study reports the implication of scanning electron microscopy (SEM) and light microscopy (LM) epidermal micro-morphological characters in the identifcation of gymnosperms of Pakistan. A number of characters were found to be of great taxonomic signifcance and can be used to distinguish diferent 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 diferent 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 diferent 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 diferent statistical methods. SEM and LM foliar epidermal studies were found very useful in taxonomic identifcation. Based on current results we recommend such studies for accurate taxonomic identifcation and complete phylogeny. 1. Introduction The systematic implications of leaf epidermal morphology are evi- dent from previous studies on diferent groups e.g. angiosperms (Diane et al., 2003; Moon et al., 2009; Zhou and Xia, 2012; Khan et al., 2017), ferns (Nayar, 1962; Sen and Mukhopadhay, 2011; Luján et al., 2011) and bryophytes (Heinrichs et al., 2009; Vanderpoorten and Gofnet, 2009; Sukkharak, 2011; Ju Árez-martÍnez et al., 2016). Unlike other groups, in gymnosperms besides some preliminary work, no compre- hensive studies have investigated the systematic value of foliar epi- dermal morphology (Dörken, 2012). Although macro-morphological characters are commonly used in the description of species in foras, the use of foliar epidermal micro- morphology can be a helpful additional tool to aid description and to distinguish many complex taxa (Khan et al., 2018). Florin (1931) paid special attention to foliar epidermal morphology in his systematic stu- dies of living gymnosperms. Pant and Mehra (1964) described the foliar epidermal features of Ephedra foliata and reported the presence of longitudinal epidermal cells and stomata in rows. Stockey and Taylor, (1978) studied the foliar epidermal features of genus Araucaria through the scanning electron microscope and found it useful taxonomically. Ickert-Bond (2000) investigated the foliar cuticle morphology of several Pinus species and reported a foliar epidermal feature that is of sig- nifcant value for the taxonomic assessment of this genus. Mickle et al. (2011) conducted a scanning electron microscopy (SEM) study of Cycas cuticle characteristics and found that this feature can be used along with macro-morphology for taxonomic assessment. Even a single foliar epidermal character may have wide taxonomic and paleobotanical implications. From a paleobotanical perspective, foliar epidermal micro-morphological studies are considered more robust than https://doi.org/10.1016/j.fora.2019.03.016 Received 2 October 2018; Received in revised form 24 March 2019; Accepted 25 March 2019 ⁎ Corresponding author. E-mail address: raeeskhan@bs.qau.edu.pk (R. Khan). Flora 255 (2019) 42–68 Available online 02 April 2019 0367-2530/ © 2019 Elsevier GmbH. All rights reserved. T