Phenomenon of “Siamese embryos” in cereals in vivo and in vitro: Cleavage polyembryony and fasciations

Abstract

The genesis of wheat microsporial polyembryoids in vitro was analyzed in detail. The nature of different phenotypes of cereal polymeric embryos was identified. They represent the class “multiple shoot meristems,” which results from a cleavage polyembryony and is accompanied by organ fasciations of all known types (radial, flat, or ring). The morphological nature of cereal embryonic organs has been clarified: shoot meristem—axial organ; scutellum—lateral outgrowth of this axis; coleoptile—derivative of shoot meristem but fused with scutellum; terminality of scutellum—the result of linear fasciation that occurred historically. An explanation is given on how the structural model of an auxin polar transport works during the establishment of bilateral symmetry in a cereal embryo that is associated with the inverted polarization of the carrier protein PIN1 on cell membranes and, correspondingly, with the inverted auxin transport performed by this carrier (Fischer-Iglesias et al., 2001; Forestan et al., 2010).