PT  - JOURNAL ARTICLE
AU  - Ya Li
AU  - Wei Du
AU  - Shuai Wang
AU  - Xiao-Fan Wang
TI  - Organogenesis and Vasculature of <em>Anaxagorea</em> and its Implications for the Integrated Axial-Foliar Origin of Angiosperm Carpel
AID  - 10.1101/2020.05.22.111716
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.05.22.111716
4099  - http://biorxiv.org/content/early/2020/06/19/2020.05.22.111716.short
4100  - http://biorxiv.org/content/early/2020/06/19/2020.05.22.111716.full
AB  - The carpel is the definitive structure of angiosperms, the origin of carpel is of great significance to the phylogenetic origin of angiosperms. Traditional view was that angiosperm carpels were derived from structures similar to macrosporophylls of pteridosperms or Bennettitales, which bear ovules on the surfaces of foliar organs. In contrast, other views indicate that carpels are originated from the foliar appendage enclosing the ovule-bearing axis. One of the key differences between these two conflicting ideas lies in whether the ovular axis is involved in the evolution of carpel. The aim of this paper is to investigate whether the axial homologs remain in the carpel of extant angiosperms, and thereby to prove the carpel is integrated axial-foliar originated. Two Anaxagorea species was used for organogenesis and comparative anatomical study due to its outstanding and unusually long carpel stipe. The continuous change of vascular bundles at carpel stipe in different developmental stages was described in detail. Organogenesis study shows that the carpel stipe of Anaxagorea occurs at the early stage of carpel development. Vascular bundles at the base of Anaxagorea carpel are a set of discrete ring-arranged collateral bundles (RACBs), which branch out at the upper portion into two sets of RACBs below each ovule. The ring-arranged collateral bundles indicates a clear morphological evidence for the existence of the axial homologs in the carpel and thus support the idea that carpels originated from the integration of the ovular axis and foliar parts. This finding may also promote reconsiderations of the phylogenetic relationship between angiosperms, gnetophytes and Cordaitales.Competing Interest StatementThe authors have declared no competing interest.