Abstract
Embryological characters of Siparunaceae, which are poorly understood, were studied on the basis of two constituent genera, an African Glossocalyx and a South American Siparuna, to better understand their evolution within Laurales. These two genera have many embryological characteristics in common with the other lauralean families. Noticeably, they share the multi-celled ovule archesporium (uncertain in Glossocalyx) as a synapomorphy with all the other lauralean families except Lauraceae, the anthers dehisced by valves as a synspomorphy with all the other lauralean families except Calycanthaceae and Monimiaceae, and the bisporangiate anther as a synapomorphy with Gomortegaceae and Atherospermataceae. Siparunaceae are, however, distinct from all other laularean families in having unitegmic ovules that were derived from bitegmic ovules, probably due to an elimination of the outer integument. Likewise, the lack of the testa (i.e., developed outer integument), the "endotegmic" seed coat, and the perichalazal seed at maturity are also characteristics of Siparunaceae. Within the family, Siparuna differs from Glossocalyx in having plural tetrads of megaspores and plural, starchy-rich, one-nucleate, tubular embryo sacs (autapomorphies). On the other hand, Glossocalyx is characterized by having bilaterally flattened seeds (autapomorphy). Although functional aspects of those autapomorphies are uncertain, both Glossocalyx and Siparuna show evolution in different embryological characters.
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Acknowledgements
We are grateful to Peter H. Raven, James C. Solomon, Peter C. Hoch, Williams A. Haber, Susanne S. Renner, and M. Kropffand for their assistance in obtaining materials used in the present study, and to Kweon Heo and Ryoko Imaichi for their technical advice in the use of Technovit. The present study was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (no. 14405012).
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Kimoto, Y., Tobe, H. Embryology of Siparunaceae (Laurales): characteristics and character evolution. J Plant Res 116, 281–294 (2003). https://doi.org/10.1007/s10265-003-0091-9
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DOI: https://doi.org/10.1007/s10265-003-0091-9