Seed morphological diversity of Pedicularis (Orobanchaceae) and its taxonomic significance

Mature seeds of 109 species of Pedicularis representing 13 groups according to Tsoong's infra-generic classification were investigated using light microscopy (LM) and scanning electron microscopy (SEM). The largest seeds occurred in P. superba (4.82 +/- A 0.32 mm x 2.18 +/- A 0.18 mm) and the smallest in P. crenata (0.95 +/- A 0.16 mm x 0.72 +/- A 0.08 mm). The individual seed weight ranged from 0.20 to 9.52 mg. There were two types of primary ornamentation, i.e. reticulate and undulate. Reticulate seeds were found in all examined species except for P. pantlingii and P. confluens. The reticulate seeds were divided into three subtypes, i.e. cristate-reticulate, regular-reticulate and membranous-reticulate. Among them, the cristate-reticulate and the undulate primary ornamentation are firstly reported. The inner tangential wall ornamentation was categorized into granulate, ruminate or striate. Seed characters seem to support the transfer of Pedicularis to Orobanchaceae from traditional Scrophulariaceae. Seed length, individual seed weight, primary ornamentation and inner tangential wall ornamentation were considered as potentially useful characters for infra-generic classification. Non-metric multidimensional scaling (NMDS) analyses indicated a clustering of some species in group 1 (Sceptrum) and all species in group 6 (Cyathophora), respectively. However, seed data were not highly congruent with Tsoong's classification for delimitation of existing groups. Some characters, such as seed shape, primary ornamentation, inner tangential wall ornamentation and epidermal cell shape could be applied to identification of some species in this genus.