Early reproductive developmental anatomy in Decaisnea (Lardizabalaceae) and its systematic implications.
OBJECTIVE
Decaisnea insignis, known as 'dead man's fingers' (Lardizabalaceae), is widely distributed in China and the Himalayan foothill countries. This economically important plant, which is the only species in the genus, has not been the subject of any embryological studies aside from one brief, older paper that lacks micrographs. Data on Decaisnea are also important because its systematic position has been unstable since the genus was established in 1855. Therefore, the objectives of this study were: (a) to use modern microscopy to document early reproductive anatomical development in Decaisnea; and (b) to compare qualitatively these early embryological characters with allied taxa in a systematic context.


METHODS
Decaisnea insignis floral buds and inflorescences were regularly collected from Shaanxi Province, China and prepared for light microscopy. The embryological characters studied were qualitatively compared with those of allied taxa via a thorough examination of the existing literature.


RESULTS
Early reproductive anatomy in Decaisnea was documented and novel revelations made. It was discovered that the pollen is shed when three-celled (not two-celled, as previously reported), and that endosperm formation is nuclear (not cellular or helobial, as previously reported). These two newly revealed embryological characters are not found in any other members of Lardizabalaceae. Furthermore, neither are persistent antipodal cells, which we confirmed to be present in Decaisnea.


CONCLUSIONS
Decaisnea and other Lardizabalaceae characteristically have tetrasporangiate anthers, a secretory tapetum, simultaneous microsporocyte cytokinesis, primarily bitegmic, crassinucellate ovules, and a Polygonum type embryo sac. However, in the family, persistent antipodals, nuclear endosperm, and pollen shed at the three-celled stage are only found in Decaisnea. These embryological data prompted the suggestion that Decaisnea needs elevation above the level of genus.
Wang
Hua-Feng
HF
Beijing Urban Ecosystem Research Station, State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 100085 Beijing, China.
Friedman
Cynthia Ross
CR
Zhu
Zhi-Xin
ZX
Qin
Hai-Ning
HN
D056625:Endosperm / Q000166:cytology / Q000196:embryology; D056130:Gametogenesis, Plant; D056771:Ovule / Q000166:cytology / Q000196:embryology; D011058:Pollen / Q000166:cytology / Q000196:embryology; D029626:Ranunculaceae / Q000033:anatomy & histology* / Q000145:classification / Q000166:cytology / Q000196:embryology*; D012098:Reproduction