Embryo and endosperm development in Billbergia nutans H. Wendl. ex Regel (Bromelioideae - Bromeliaceae) and its implications for the embryonomy of Bromeliaceae

Abstract The proposition of patterns, types, and variations for embryogenic events is one of the objectives of embryonomy. Bromeliaceae is a diverse neotropical plant family for which this approach has been ambiguously and rarely discussed in detail. In this study, we analyzed the embryogeny and endospermogenesis of Billbergia nutans H. Wendl. ex Regel, a bromeliad worldwide known as ornamental and with no embryogenic studies recorded to date. Seeds of B. nutans were periodically collected after manual pollination and processed with standard methods for analysis under light microscopy. Among other embryogenic characteristics, we highlight the longitudinal division of ca and its major contribution to the formation of the embryo, the presence of hypophysis derived from m, and the formation of the first internal cells of the proembryo from q. Endospermogenesis is helobial, and the cellularization in each chamber occurs at specific stages of the embryogenesis. The embryonic number is 211 and the embryonomic formula ca = pco + phy + pvt + icc; cb = iec + ico + co + s, typical of the Onagrad Type. This classification is unprecedented for Bromeliaceae, although it can be contradictorily applied to other species of the family. Special embryogenic characteristics of B. nutans, as the contribution of n in the formation of the root cap and the longitudinal divisions in the suspensor cells, led to the proposal of a new variation for this type: the Billbergia Variation, which also can be applied to some other Bromeliaceae species.