Embryology of Illigera and Sparattanthelium (Hernandiaceae, Laurales): Family Characteristics and Relationships

Abstract

The Hernandiaceae, a small family comprising five genera that are closely related to the Lauraceae and Monimiaceae, exhibit highly diverse morphological characters. Here, we present the first embryological study of Illigera and Sparattanthelium and, by comparing those data to those from Gyrocarpus and Hernandia, discuss the relationships in the Hernandiaceae and related families. Our embryological data indicate that the Hernandiaceae, which are characterized by a multiplicative outer integument, share several features (apomorphies) with the Lauraceae, including an amoeboid tapetum, a lack of hypostase, and exalbuminous seeds, suggesting a close relationship between them. Within the Hernandiaceae, Hernandia/Illigera (Hernandioideae) exhibit radially elongated tapetal cells in the anthers, monolayered pollen mother cells, anthers dehisced by laterally hinged valves, thick parietal tissue in the nucellus, a nucellar beak, a vascularized outer integument or testa, and a thick, persistent mesotesta. In comparison, Gyrocarpus/Sparattanthelium (Gyrocarpoideae) are characterized by an embryo sac protruding from the nucellus and a nonspecialized chalaza. Such marked diversity of embryological characters in the Hernandiaceae, as well as the great embryological gap between its two subfamilies, corroborates previous evidence of a deep split and early divergence of the family.

Diversity and Lability of Floral Phyllotaxis in the Pluricarpellate Families of Core Laurales (Gomortegaceae, Atherospermataceae, Siparunaceae, Monimiaceae)

“…Thus, simple-whorled floral phyllotaxis is not so common in pluricarpellate families of core Laurales. In contrast, it is pervasive in unicarpellate core Laurales, where, in addition, the floral whorls are not dimerous but largely trimerous in Lauraceae (e.g., Mez 1889; Singh and Singh 1985;Hyland 1989;Rohwer 1993;Buzgo et al 2007) and trimerous, tetramerous, and pentamerous in Hernandiaceae (Kubitzki 1969;Endress and Lorence 2004;Kimoto and Tobe 2008). Tetramerous flowers of Lauraceae and Hernandiaceae also begin with two dimerous whorls (Endress 1987;Endress and Lorence 2004).…”

“…In Atherospermataceae, whorled flowers are predominant, but in three genera (from both major clades) lability between whorled and spiral phyllotaxis occurs. In Hernandiaceae and Lauraceae spiral flowers are not known; in all extant species studied, phyllotaxis is whorled (Mez 1889;Kubitzki 1969;Hyland 1989;Endress and Lorence 2004;Buzgo et al 2007;Kimoto and Tobe 2008), except for a few derived Lauraceae (species of Lindera and Litsea) that have lost their perianth and have an irregular phyllotaxis (Endress 1990). In floral fossils ascribed to Lauraceae, phyllotaxis is also whorled (trimerous; Mauldinia [Drinnan et al 1990;Viehofen et al 2008], Perseanthus [Herendeen et al 1994], Neusenia [Eklund 2000], Lauranthus [Takahashi et al 2001], and Potomacanthus [von Balthazar et al 2007]).…”

Embryology of Japonolirion (Petrosaviaceae, Petrosaviales): a comparison with other monocots

“…A similar nucellar cap is known in Ceratophyllum (Shamrov 1997), whose phylogenetic relationship with the monocots and magnoliids is controversial (Qiu et al 2005), and in the magnoliids: for instance, Piperales pro parte (Tobe et al 1993), Canellales pro parte (Tobe and Sampson 2000), Laurales pro parte, and Magnoliales pro parte (Kimoto and Tobe 2001). In Sparattanthelium (Hernandiaceae, Laurales; Kimoto and Tobe 2008), the two-cell-layered nucellar cap is formed early in ovule development, as in Japonolirion. However, a two-cell-layered nucellar cap is not formed in the basal angiosperms, i.e., Amborellaceae, Nymphaeaceae, and Austrobaileyaceae (Tobe et al , 2007Fig.…”