Origin and evolution of the unusual leaf epidermis of Caryodaphnopsis (Lauraceae) |
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| Institution: | 1. State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, Beijing 200093, China;2. University of Chinese Academy of Sciences, Beijing, China;3. Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, USA;4. Department of Paleontology, University of Vienna, 1090 Vienna, Austria;1. Institute of Geonics of the CAS, Institute of Clean Technologies, 708 00 Ostrava-Poruba, Czech Republic;2. University of Wollongong, Faculty of Engineering and Information Sciences, Wollongong, Australia;1. Fakultät für Mathematik, Universität Wien, Oskar-Morgenstern-Platz 1, A-1090 Wien, Austria;2. FB 12 – Institut für Mathematik, Goethe-Universität, Robert-Mayer-Straße 10, D-60325 Frankfurt am Main, Germany;1. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China;2. Natural History Museum of Guangxi Zhuang Autonomous Region, Nanning 530012, China;1. Unité “Ecologie et Dynamique des Systèmes Anthropisés” (EDYSAN, FRE 3498 CNRS-UPJV), Université de Picardie Jules Verne, 1 rue des Louvels, F-80037 Amiens Cedex 1, France;2. Université de Bangui, Cerphameta, BP 1450 Bangui, République Centrafricaine;3. UR B&SEF, CIRAD, Campus International de Baillarguet, F-34398 Montpellier, France;1. Department of Biology, Wilfrid Laurier University, 75 University Avenue W, Waterloo, ON, Canada N2L 3C5;2. Instituto Politécnico Nacional (CIIDIR-IPN Michoacán), Justo Sierra 28, Jiquilpan CP 59510, Michoacán, Mexico |
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| Abstract: | We studied leaf epidermal anatomy of Caryodaphnopsis Airy Shaw, a genus disjunct between tropical Asia and tropical America, using light microscope and scanning electron microscope. We sampled 10 species of Caryodaphnopsis and 52 species of other Lauraceous genera. Our observations suggest that this genus possesses a unique lower leaf epidermis. Compared with other leaves of Lauraceae, this genus has an additional layer covering the lower leaf epidermis and the stomatal apparatus. The additional layer is either closed or poriferous/reticulate. The outer periclinal walls of the lower leaf epidermis protrude outside forming hollow domes or columns, and the distal endings of these domes or columns are expanded and fused, which forms the additional covering layer. Three different types are recognized in the genus: (1) the middle portion of the protuberances is not contracted and the distal endings are free or adnate to each other, with only limited space between the two layers; (2) the middle portion is slightly contracted in the outer part, the distal endings are fused, with more space between the two layers; (3) the middle portion is conspicuously contracted and elongated into columns, the distal endings are fused and it is roomy between the two layers. The structure of the leaf lower epidermis is reconstructed and illustrated for the first time. This unusual leaf lower epidermis of Caryodaphnopsis is derived in Lauraceae and is an autapomorphic character. Outward protrusions of the outer periclinal walls forming papillate protuberances surrounding the stomatal apparatus are also found in a few other genera including Neocinnamomum, a genus closely related to Caryodaphnopsis, but the distal endings of these protrusions are not expanded and connected. We hypothesize that the periclinal wall of the lower leaf epidermis has been gradually modified in Lauraceae, from a smooth pattern in most genera, to papillate pattern (e.g. Neocinnamomum), and to the double layered lower leaf epidermis in Caryodaphnopsis. The origin and evolution of this unique lower epidermis might have been related to the climatic cooling and aridification since the late Eocene. |
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| Keywords: | Anatomy Light microscope (LM) Scanning electron microscope (SEM) Systematics Lauraceae |
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