A morphological, anatomical and palynological study of Aethionema lepidioides (Brassicaceae) - an endangered species endemic to Turkey

Abstract

Aethionema lepidioides Hub.-Mor. is an endangered endemic species in Turkey with a very narrow natural distribution area. The present study aims to reveal the structural features of this species. For this purpose, its unknown morphological features – such as leaf, petal, sepal dimensions and shapes, filament and anther lengths, as well as seed dimensions, shape, colour and micromorphology – have been studied for the first time. To reveal the pollen characteristics of Ae. lepidioides, light microscope and SEM studies were conducted. Additionally, in the present study the anatomical features of Ae. lepidioides were also studied for the first time. The Ae. lepidioides leaves were found to be linear-oblanceolate, with an entire margin and a subacute to obtuse apex. The seeds were found to be dark brown and oval-shaped, with reticulated surface ornamentation. Anatomical studies found roots in the secondary growth stage, with xylem-filled pith. The stem was in the primary growth stage, featuring a multi-layer cortex under its outermost single-layered epidermis, a pronounced endodermis and a central cylinder beneath. The leaves were thick, amphistomatic and covered with a prominent wax layer. Their mesophyll was equifacial, and their stoma type was anisocytic. A stomatal index of 26 was found for the upper epidermis, while a corresponding index of 28.4 was found for the lower epidermis. The pollens were monad, radially symmetrical and isopolar. The pollen type was colpate, and the pollen shape was found to be prolate-spheroidal with a P/E ratio of 1.08.