The phylogenetic potential of orbicules in angiosperms

Abstract

The distribution of orbicules was investigated for eleven taxa of six genera in Lamiaceae and four taxa of three genera in Verbenaceae using scanning electron microscopy. A literature survey to evaluate the phylogenetic potential of the orbicules and their possible correlations with tapetum types was also conducted. The orbicules are consistently absent in all investigated taxa of Lamiaceae, while small orbicules of an average size of less than 1 µm are densely distributed in Verbenaceae. In fact, orbicules appear consistently in 123 of 150 angiosperm families when investigated in at least one species. Thus, the distribution patterns of orbicules could be a useful diagnostic character in angiosperms. In addition, orbicules occur in 84% taxa of the secretory tapetum type, while they are commonly absent in the amoeboid tapetum type (ca. 80%). The presence of orbicules may be correlated with the secretory tapetum type. However, the study of orbicules is restricted in 150 families and the tapetum type within these families can be applied for 92 families out of a total of 416 angiosperm families. Thus, further investigation of orbicules is necessary in extended taxa to address the questions pertaining to orbicules.

Micromorphological differentiation of Korean Disporum species using light and scanning electron microscopy

“…Detailed micromorphology of the orbicules in the Korean Disporum species is described here for the first time (Table 4). As in other orbicular studies in angiosperms (Huysmans et al, 1998; Huysmans, Verstraete, Smets, & Chatrou, 2010; Verstraete et al, 2014; Verstraete, Groeninckx, Smets, & Huysmans, 2011), globular orbicules with psilate surface ornamentation were the most frequent type observed, which reflects the general pattern in early‐diverged taxa as a plesiomorphic character state (Moon, 2018; Ruggiero & Bedini, 2020). Individual orbicule size presented here is generally consistent with the spectrum of observations (0.085–15 μm) in angiosperms to date (Nilsson & Robyns, 1974; Vinckier & Smets, 2002).…”

“…Although most orbicule characters in angiosperms have continuously been a subject of systematic studies due to taxonomic importance (Moon, 2018; Ruggiero & Bedini, 2020), the presence of orbicules has only been described in one species from the genus Disporum ( D. smilacinum ; Takahashi & Sohma, 1979). Detailed micromorphology of the orbicules in the Korean Disporum species is described here for the first time (Table 4).…”

A Comprehensive Study of the Genus Sanguisorba (Rosaceae) Based on the Floral Micromorphology, Palynology, and Plastome Analysis

“…Orbicules (or Ubisch bodies) are small and granular particles found in the inner locule wall of mature anthers and are composed of sporopollenin [68][69][70][71]. In the Rosaceae, the occurrence of orbicules represents the consistency within the tribe in Sorbarieae [31], Neillieae [32], and genera in Luetkea, Sibiraea, and Xerospiraea [33].…”

Micromorfología y ultraestructura de las anteras y los granos de polen en diez genotipos élite de Theobroma cacao (Malvaceae)

“…En el caso de Malvaceae, el tapete secretor es el más común (Lattar et al, 2014), pero se ha registrado en esta familia de plantas la presencia de orbículas en especies que tienen tapete plasmodial e invasivo no sincitial (Strittmatter & Galati, 2001;Galati et al, 2007;Galati et al, 2011). Teniendo en cuenta lo anterior, se puede indicar que las orbículas se encuentran ampliamente distribuidas en diferentes grupos de plantas (Verstraete et al, 2014;Moon, 2018;Ruggiero & Bedini, 2020) y la relación entre estas estructuras y los tipos de tapete, no ha sido aún claramente dilucidada.…”