Home‎ > ‎

Pollen Morphology

Acanthogilia gloriosa (Brandegee) A.G. Day and Moran

    The pollen of Acanthogilia gloriosa has been described by
Stuchlik in Day & Moran (1986), but was not included in either Stuchlik's (1967) pollen classification or that of Taylor & Levin (1975). Here I consider it to be a unique pollen type in the family, the Acanthogilia-type. Day & Moran (1986) suggest that the verrucae of Acanthogilia's pollen and the insulae of Cantua are homologous structures, indicating a close relationship. However, Acanthogilia's pollen is zonotreme, while the pollen of Canuta (also Bonplandia and Cobaea) is pantotreme.
    Pollen grains 5–8 colporate (zonocolporate), suboblate to spheroidal; diameter 55–64
micrometers polar diameter, 61–71 micrometers equatorial diameter. Colpi short, slightly longer than the diameter of the pores. Pores lalongate to circular; diameter 5–7 micrometers polar length  7–10 micrometers equatorial length. Exine 2.4–2.9 micrometers thick; nexine 0.8–1.2 micrometers thick, thicker at the pore margin, up to 1 .7 micrometers, finely perreticulate. Lumina variable in shape and size; diameter less than 0.5 micrometers up to 1 micrometers; muri supported by densely spaced, simple bacula, sometimes 2–3 merged together. Diameter of bacula ca. 0.5 micrometers. Reticulum supraverrucate. Verrucae on surface of exine variable in shape and size, from very small and flat with diameter ca. 1 micrometers to spherical or ovaloidal with diameter to 10 micrometers; in developing pollen grains very densely spaced. Verrucae surface ultra-finely striate or rugulate. (Stuchlik in Day & Moran 1986)

     The pollen in the Cantua (Cantueae) is unusual relative to other members of Polemoniaceae. The pollen is large. Monfils & Prather (2004) note that the largest mean pollen diameter is that of Cantua quercifolia at 84.7–87.2 micrometers, while the smallest is C. volcanica (62.3–62.6 micrometers). In general the pollen grains are pantoporate*, spheroidal, with circular to oval pores that range in number from 4–27. The exine (or more correctly the sexine) is semitectate with irregularly shaped insulae (verrucae). The verrucae may be regularly spaced or more or less irregularly distributed, but are usually finely striate. In Subgenus Huthia, the verrucae also bear irregular, wart-like processes.

            Stuchlik (1967) examined Cantua buxifolia, C. candelilla, C. quercifolia, and Huthia longiflora (=C. mediamnis). He concluded that there were two pollen types (Cantua I and II). The later, present only in C. quercifolia, was distinguished by the greater number of pores (i.e., 28–34); however, Monfils & Prather 2004 failed to find such a distinction. The first SEM study including Cantua (Taylor & Levin 1975) examined only C. quercifolia, and Huthia coerulea (=C. volcanica). The most extensive survey of pollen in Cantua is that of Monfils & Prather (2004), who examined Cantua bicolor, C. buxifolia, C. candelilla, C. cuzcoensis, C. flexuosa, C. sp. nov. (near C. pyrifolia), C. pyrifolia, C. quercifolia, and C. volcanica. They found a distinction between the pollen of C. quercifolia, and C. volcanica and all other Cantua sampled (though they did not refer these to different pollen types). Cantua quercifolia, and C. volcanica have insulae that are both suprastriate and also bear irregular processes; whereas, all other Cantuas lack the processes. Interestingly, Stuchlik (1967) noted that Huthia longiflora (=Cantua mediamnis) phas insulae that bear “minute spinule-like processes,” but did not note this feature in C. quercifolia.

 * For an excellent glossary of pollen terminology see Punt et al. 2007.

Cantua quercifolia Juss.

    Pollen of Cantua quercifolia has been described by Stuchlik (1967), Taylor & Levin (1975) and Monfils & Prather (2004). The presence of both microstriae and minute, irregular processes on the insulae have been interpreted as a synapomorphy for Cantua quercifolia, C. mediamnis and C. volcanica (see Monfils & Prather 2004).

    Pollen grains pantoporate, spheroidal, varying in size, (76–)78.4–93.1 mm in diameter. Pores 16–27 (according to Stuchlik 1967, pores 28–34), circular or oval, 6.1–8.5 mm in diameter. Exine 5.3-7.6 micrometers thick. Sexine 4.2-5.5 thick, semitectate (insulous). Insulae enlarged and rounded in shape, evenly distributed, about 1.6 micrometers thick, supported by densely spaced bacula (2.6-3.0 micrometers long; diameter 1.0-1.3 micrometers).  Supratectal surface with microstriae and bearing irregular processes. Isolated, free bacula also present, standing between the insulae (about 2.3 micrometers long and about 0.5 micrometers in diameter). Classified by Stuchlik (1967) as Cantua II pollen type.

    SEM of pollen of Cantua quercifolia: the upper image illustrates the baculae supporting the microstriate insulae, with free-standing baculae; the lower image illustrates the abundant pollenkitt, that usually obscures the surface micromorphology.

Bonplandia geminiflora Cav.

    The pollen of Bonplandia geminiflora has been described by Stuchlik (1967) and Taylor and Levin (1975).  This pollen has been classified apart from other members of Polemoniaceae (Bonplandia-type; Stuchlik 1967).  In general, the genus has pollen that is pantoporate and reticulate, with broad, flat elements making up the reticulum.  The following characterization makes use of previous descriptions, but also incorporates additional measurement data of B. geminiflora, using light and electron microscopy.
Pollen grains pantopororate (Fig. 9), spheroidal, 53–78 m in diameter.  Apertures 20–32, the inner pore circular or slightly oval, 5–6 micrometers in diameter, the outer pore somewhat irregular, circular to oval, 3.5–4.6 micrometers polar diameter, 4.6–8.3 micrometers equatorial diameter .  Exine 3.5–4.2 micrometers thick.  Sexine striato-reticulate, outer lirae 1.5–2.0 micrometers  wide and strongly flattened, often with one or a row of a few rounded, irregular
or acute spinule-like verrucae, 0.5–1.0 X 0.5–1.9 micrometers; stria narrow, less than 0.5(–0.6) micrometers.  Outer lirae connected by an inner lirae, forming a reticulum.