Embryogenesis in sexual and asexual species of Zeuxine (Orchidaceae)

The development of the zygote following sexual union in Zeuxine longilabris exhibits a predetermined polarity and patternized sequence of developmental stages leading to the initiation of cotyledonary and epicotylary activity in adjacent sectors, both being terminal on the embryonal axis. The cotyledonary growth is incipient and the epicotylary sector is distinguishable only by histological distinctivity. The initiation and trend of growth of the asexual embryo totally deviates from that of its sexual counterpart. Although incipient and inconsistent polarity becomes established in the dividing nodular cell system eventually the embryos end up as a spindle-shaped structure of homogeneous cells where not even the initiation of root and shoot polar differentiation is seen either within or without. Under these circumstances the asexual embryos are broadly comparable to the earlier stages in the development of embryoids in free cell cultures. © 1981 Indian Academy of Sciences