Sporogenesis and gametogenesis in Agapanthus praecox Willd. orientalis (Leighton) Leighton and their systematic implications
2010
Zhang, Di | Zhuo, Li-Huan | Shen, Xiao-Hui
Micro- and megasporogenesis as well as male and female gametogenesis in genus Agapanthus are reported for the first time. The results are as follows: The anther wall, whose development is of dicotyledonous type, consists of four layers: the epidermis, the endothecium, one or two middle layers, and the secretory tapetum. Fibrous thickenings are developed in the endothecium when shed. Successive cytokinesis during microsporogenesis results in a decussate tetrad of microspores. Ellipsoidal pollen grains are 2-celled when anthers dehisce, with monosulcate extending to polar area; pollen ornamentation is pitted and reticulate. Ovary is superior and trilocular, with axial placenta. The ovule is anatropous, bitegmic, and tenuinucellate. The archesporial cell below nucellus epidermis functions directly as the megasporocyte. Successive cytokinesis in the megasporocyte usually produces a T-shape tetrad, and the chalazal megaspore of the tetrad develops into a Polygonum-type embryo sac. The systematic significance of embryological characters of Agapanthus is discussed.
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