Pollen morphology of <i>Kalmia</i> L. (Phyllodoceae, Ericaceae) and its taxonomic significance

Abstract

Pollen morphology of seven taxa of Kalmia was examined using light and scanning electron microscopy (LM and SEM, respectively), or SEM alone, in search of new characters that might contribute to infrageneric classification of the genus. The Kalmia species are stenopalynous and characterized by 3-colpor(oid)ate, medium, oblate pollen united in tetrahedral tetrads with rugulate exine sculpture. However, a continuous and serial variation in all the quantitative characters and exine sculpture was revealed within the genus. Kalmia buxifolia is characterized by having the smallest pollen tetrads, largest aperture, largest 2f/D ratio and septum thicker than apocolpial exine. On the other hand, K. latifolia produces the largest pollen tetrads with smallest aperture and smallest 2f/D ratio. An evolutionary trend from rugulate to psilate has also been observed in apocolpial exine sculpture of the genus Kalmia. On the basis of acetolysed pollen characteristics, a dichotomous key for Kalmia was prepared.

Pollen morphology of the tribe Phyllodoceae (Ericoideae, Ericaceae) and its taxonomic significance

“…> 0.5 µm) gemmate-pilate (Type MG; The present study reveals that in Phyllodoceae, both medium or minute and oblate pollen grains are united usually in tetrahedral tetrads (Table 2; Sarwar and Takahashi, 2012). Pollen tetrads of this tribe are generally characterized by the presence of viscin threads except in some species (Table 2; Sarwar and Takahashi, 2012). Results of the present study, in general, support previous palynological observations, however, in several instances, marked differences among the observations are apparent e.g., viscin threads on pollen tetrads of Epigaea.…”

“…These palynological features might imply an evolutionary tendency to a reduced (smaller) ectoaperture (Warner and Chinnappa, 1986), and might be an apomorphic pollen character state for this genus as well as the family Ericaceae . Among the other genera of the tribe Phyllodoceae, the systematic significances of pollen morphological features of Kalmia have previously been discussed in details (Sarwar and Takahashi, 2012).…”

“…Pollen morphology of the genus Kalmia has been studied in details (Sarwar and Takahashi, 2012) and the data has been included in discussion. The remaining genus Kalmiopsis is endemic to Oregon State, USA and could not be included due to unavailability of pollen samples.…”

“…Abbreviations of names of the herbaria are according to the Index Herbariorum (Holmgren et al, 1990). The preparation of pollen grains for LM and SEM, and pollen parameter studied follow Sarwar and Takahashi (2012). Pollen slides of all collection are deposited at the Hokkaido University Museum, Sapporo, Japan.…”

“…Among the genera of Phyllodoceae, the pollen morphology of Kalmia has already been reported (Sarwar and Takahashi, 2012), but fragmentary palynological information is only available for other genera of this tribe (Sladkov, 1954;Oldfield, 1959;Stevens, 1971;Bohm et al, 1978;Comtois and Larouche, 1981;Clements, 1995;Kron et al, 2002;Radcliffe et al, 2010). Light microscopy (LM) was mainly employed in these studies; and scanning electron microscopy (SEM) was employed in a few cases.…”