02233nas a2200241   4500008004100000245008100041210006900122260001200191300001600203490000800219520151000227653001201737653001601749653001201765653001901777653001301796653001501809653001501824653000901839100001401848700001301862856011601875       2001                        eng d00aBasal meristem and root development in Isoetes asiatica and Isoetes japonica0 aBasal meristem and root development in Isoetes asiatica and Isoe  c2001///  a1225 - 12350 v1623 aWe studied the anatomy of the basal meristem and root development in Isoetes asiatica and Isoetes japonica to better understand the Isoetes rhizomorph, an enigmatic organ. The basal (root-producing) meristem of the rhizomorph is continuous with the lateral meristem, and both comprise a single meristem. The basal meristem with a layer of thin initials has both organogenetic and thickening meristem attributes. A combination of these attributes indicates that the basal meristem is distinctive among the vascular plant meristems, including cambium. The root primordia develop from young derivative cells organized in three to four radial fines, and their main body is composed of a three-layered apical meristem. The primordia, unlike the roots, produce a small number of derivative cells as well as a procambium and future root cap, and they do not form a cortex and epidermis. Prior to developing into roots, the primordia are shifted closer to the corm surface through further development of cortical tissues from the basal meristem and sloughing of surface cells. This unique developmental pattern is established through the subendogenous origin of the second embryonic root and the endogenous origin of the third root. The meristem and pattern of root development in Isoetes is compared with that indicated for the lepidodendrid and isoetalean rhizomorphs and contrasted with that in the Selaginella rhizophore. The comparison seems not to support the interpretation of the roots as leaf homologues.10aCambium10aDevelopment10aIsoetes10aLepidodendrids10aMeristem10aRhizomorph10aRhizophore10aRoot1 aYi, S.-Y.1 aKato, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0034749638&partnerID=40&md5=1887916a18c476c09780d6d6ad7f78b6