Abstract:

Seed morphology in 57 species and 5 varieties representative of the main Chinese groups of Aconitum (Ranunculaceae) was investigated under scanning electron microscope (SEM) in an attempt to evaluate its taxonomic significance. The results are: (1) Great constancy of seed coat microcharacteristics was observed within the genus. All the taxa studied exhibit a warty ornamentation of the integument epidermal cells. (2) Marked differences of seed grossmorphology were observed among the three subgenera (Lycoctonum, Aconitum, and Gymnaconitum) of the genus. In particular, seeds of subgen. Gymnaconitum are distinctly different by having round or ellipticshaped integument epidermal cells from those of subgenera Aconitum and Lycoctonum which have rectangularshaped epidermal cells. (3) Seeds of the species studied within subgen. Lycoctonum fall into two types. Seeds in A.novoluridum (the only species in sect. Alatospermum) are longitudinally very narrowly winged along three ridges and hardly squamate, and may represent the most primitive seed type of the genus Aconitum. Seeds in sect. Lycoctonum are commonly 1ridged, and more or less transversely squamate. Seeds within subgen. Aconitum are divisible into four types. Those in A.tanguticum (ser. Tangutica), which are provided with three equally developed longitudinal wings along the edges and with smooth faces, may be regarded as the simplest type within the subgenus. Another seed type with three edges and smooth faces but with some tubercles arranged transversely on the surface of epidermal cells, is apparent in species of ser. Brachypoda. Aconitum hicksii (ser. Bullatifolia) and A.brunneum (ser. Brunnea) also have this seed type. In the third and fourth types, the complete disappearance of the two longitudinal wings is coupled with considerable development of transverse membranous wings, but the third type (only found in A.pulchellum of ser. Rotundifolia) has much narrower wings than the fourth type (occurring in A.nagarum of ser. Bullatifolia, and in all species studied of ser. Stylosa, ser. Racemulosa, ser. Volubilia, ser. Inflata, ser. Ambigua, and ser. Grandituberosa). These results confirm the important potential value of seed morphology for the infrageneric division of Aconitum, and further studies should be carried out.

Key words: Aconitum, Seed morphology, Seed coat micromorphology, Systematic implication, Taxonomy