Fruit anatomy of the genus Anabasis (Salsoloideae, Chenopodiaceae)

Abstract

The fruit anatomy and morphology of 22 representatives of the genus Anabasis L. were studied, with the aim of clarifying the taxomomic importance of carpological characters in the genus. As shown in cross-sections, the pericarp of Anabasis is differentiated into the following four zones: (i) outer epidermis, (ii) subepidermal hydrated parenchyma, (iii) crystalliferous layer with lignified U-shaped cell walls and (iv) inner epidermis. Anatomical differences mainly relate to the outer epidermal structure. Fruit anatomy does not confirm the separation of the genera Brachylepis and Esfandiaria. A combination of carpological characteristics separates A. annua and A. setifera from the other species studied. Also, characters of reproductive organs in representatives of Anabasis are shown. When vegetative and reproductive features are considered, the genus Fredolia appears rather distant from Anabasis s.l. The pericarp histology of almost all the Salsoloideae (incl. Anabasis) is fully presented in the upper third of the fruit. In the lower parts of the fruit, some histological layers are either reduced or absent altogether. On the basis of the anatomical structures in the upper third of the fruit, the common carpological features of the Salsoloideae can be defined. These include a pericarp consisting of several, usually well-differentiated layers and the presence of crystalliferous cells with U-shaped walls. The two- to four-cell layered outer epidermis of three Anabasis representatives (A. eriopoda, A. jaxartica, A. turkestanica) seems to be an apomorphic feature in the Salsoloideae. The seed coat is thin (two cell layers thick) and non-differentiated. Owing to the pericarp and seedcoat structure, the fruit and seed covers have low resistance to environmental degradation processes and, therefore, are unlikely to be found among fossil remnants.