Embryology of the dioecious Australian endemic Lomandra longifolia (Lomandraceae)
Nabil M. Ahmad A , Peter M. Martin A B and John M. Vella AA Amenity Horticulture Unit, University of Sydney Plant Breeding Institute, PMB 11, Camden, NSW 2570, Australia.
B Corresponding author. Email: pmartin@camden.usyd.edu.au
Australian Journal of Botany 56(8) 651-665 https://doi.org/10.1071/BT07222
Submitted: 17 December 2007 Accepted: 30 October 2008 Published: 15 December 2008
Abstract
Microsporogenesis, embryogeny and endosperm development of Lomandra longifolia Labill. are described in detail. The formation of the anther wall is the basic type composed of four cell layers, namely an epidermis, an endothecium, one middle layer and a tapetum. The tapetum layer has glandular, uninucleate cells. Successive cytokinesis follows meiosis, subsequently forming a tetrahedral tetrad of microspores. The ovule in each carpel is hemitropous, crassinucellate and bitegmic, with the micropyle formed by the inner integument. The archesporial cell divides periclinally to form the primary parietal and primary sporogenous cells. The sporogenous cell functions as the megaspore mother cell, whereas the parietal cell divides to give rise to two parietal layers. The mature megagametophyte, which has enlarged synergids and antipodals, is of the Polygonum type, with the normal complement of seven cells and eight nuclei. Nucellar tissue in the mature ovule consists of enlarged dermal cells and irregular subdermal cells surrounding a central strand of markedly smaller cells. Endosperm development is of the nuclear type. Embryo development is of the Graminad type, characterised by oblique zygotic and early pro-embryonic divisions.
Acknowledgements
We express our deep gratitude to Dr Jane Radford, manager of the Histopathology Laboratory at the University of Sydney, for permission to work in her laboratory and for her help on numerous practical matters. Thanks are also due to Professor R. A. McIntosh and Miss Alexandra Freebairn for assistance in the preparation of the manuscript. Finally we thank Leppington Speedy® Seedlings Pty Ltd for the provision of plant material and financial support.
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