Seed morphological study in relation to taxonomy of Sedum s.l. (Crassulaceae) in Iran

The cosmopolitan genus sedum L. comprising ca. ۴۲۰ species belongs to the family Crassulaceae and subfamily Sedoideae. This genus has a very confused systematic position and it’s delimitation has been a matter of controversy. In spite of a number of previous studies, seed characters of the genus were poorly understood. The aime of this study is to represent a detailed account in seed morphology of ۲۲ species of Sedum s.l. in Iran using light (LM) and scanning electron microscopy (SEM). The seeds are black, brown or yellow in color and long elliptic to ovate in shape. Their length ranged from ۴۵۶.۸ to ۹۷۱.۷ μm. Three types of seed coat ornamentation (Tenuicostate, Laticostate and Tectocostate) were recognized according to costae thickness and degree of lateral fusion of the papillae. Anticlinal walls are prominent and the shape of periclinal walls varied from concave to weakly convex. Our findings revealed that among the examined characters, seed color and size, total number of costae on both surface of the seed, the width of the space between longitudinal costae, thickness of transverse connections and the shape of periclinal walls were taxonomically usefull in the intergeneric classification and segregation of the genera Phedimus, Hylotelephium and Prometheum from Sedum s.s. Our results also support the alliance of two sections Sedum and Epeiteum due to several identical seed traits existing within these sections. It is suggested to carry out further systematic researches on this large genus such as anatomical, palynological and cytological studies.

کلیدواژه ها:

Phedimus ، Costae ، Epeiteum ، Periclinal walls