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. DOI: http://dx.doi.org/10.3329/bjpt.v19i2.13126 Bangladesh J. Plant Taxon. 19(2): 123-133, 2012 (December)
Highlights
Kalmia L. (Family Phyllodoceae, subfamily Ericaceae) comprises eleven quite distinct species of evergreen or deciduous shrubs and is restricted to North America and Cuba, the only circumboreal species is K. procumbens (Kron et al, 2002; Stevens et al, 2004)
General pollen morphology In LM, the medium pollen grains are united in tetrahedral tetrad (Fig. 1A-C); viscin threads present in some species; D 24.4-36.6 μm, P 12.8 -18.8 μm, E 17.3-26.3 μm, D/d 1.31-1.52, P/E 0.70-0.80, oblate or suboblate; 3-colpor(oid)ate, 2f 11.6-19.6 μm, W 0.4-1.2 μm, 2f/D 0.32-0.67, costae present and distinct, colpus margin distinct; endocracks present; endoaperture distinct and lalongate; apocolpial exine 1.6-2.1 μm thick, septum 0.7-1.9 μm thick (Table 2); tectate, apocolpial exine sculpture from fine verrucate to rugulate
Specific pollen description K. angustifolia In LM, pollen grains are in lobed tetrahedral tetrad; viscin threads present; oblate, nonacetolysed grains suboblate; exine sculpture rugulate (Table 2)
Summary
Kalmia L. (Family Phyllodoceae, subfamily Ericaceae) comprises eleven quite distinct species of evergreen or deciduous shrubs (rarely tree) and is restricted to North America and Cuba, the only circumboreal species is K. procumbens (Kron et al, 2002; Stevens et al, 2004). Linnaeus described the genus Kalmia (Linnaeus, 1753, 1754) as well as its first two species, K. latifolia and K. angustifolia. Drude (1889) placed Kalmia in the tribe Phyllodoceae, and its position has not been changed by most of the subsequent authors (see Ebinger, 1974). Kuntze (1891) used Catesby's pre-Linnean name of Chamaedaphne and made numerous transfers to it, while Small (1914) divided Kalmia into two genera. He proposed the genus Kalmiella, segregating Kalmia hirsuta and K. ericoides in the latter genus on the basis of their inflorescence structure (i.e., solitary flowers) and deciduous calyx (Small, 1914). All subsequent authors (Copeland, 1943; Wood, 1961), except Alain (1957), have treated Kalmiella as a synonym of Kalmia
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