The taxonomic significance of pollen morphology in Andromedeae s.s., Gaultherieae, Lyonieae and Oxydendreae (Ericaceae: Vaccinioideae)

Andromedeae s.s.

日本花粉学会会誌

The pollen morphology of 41 species in 12 of the 13 genera constituting tribes Andromedeae s.s., Gaultherieae, Lyonieae and Oxydendreae of Ericaceae, subfamily Vaccinioideae, was investigated with light (LM) and scanning electron microscopy (SEM). The pollen of the species included in these tribes is stenopalynous: 3-colopor (oid) ate grains in oblate permanent tetrads. Pollen characteristics do not show notable correlation with the tribal classification, although it is observed that the pollen tetrads tend to be compact in Andromedeae s.s., Gaultherieae and Oxydendreae, but usually lobed in Lyonieae, especially in Lyonia. The compact tetrads of tribe Andromedeae are characterized by a thin, perforated septum. Apocolpial exine sculpture of individual grains within the pollen tetrad varies from psilate to coarsely rugulate, the rugulae have a 'secondary sculpture' of faint to well-defined fine or coarse striae. Two main R and S types, six subtypes and seven sub-subtypes of exine are recognized based on the primary sculpture and distinctness of secondary sculpture on the rugulae. A continuous series of variation in both qualitative and quantitative characters of the pollen was observed within all four tribes. Sometimes exine sculpture shows little variation in some genera within these tribes; e.g. Leucothoe (S2 and S2**) within the tribe Gaultherieae, and Agarista (R2-3 and R4) and Lyonia (R3, R3* and R3**) within the tribe Lyonieae. Exine sculpture, degree of tetrad compactness, tetrad size and septum thickness proved to be the most useful characters for helping to clarify the infrageneric classification in Gaultheria, Agarista and Lyonia. An exine surface with secondary striate sculpture is apparently characteristic of subfamily Vaccinioideae, based on our general palynological survey of the Ericaceae.