Ovule ontogenesis and megagametophyte development in Onobrychis schahuensis Bornm. (Fabaceae)

Authors : Abdolkarim CHEHREGANI, Nayereh TANAOMI

Pages : 241-248

View : 23 | Download : 12

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :The ovule ontogenesis and the megasporogenesis events in Onobrychis schahuensis Bornm. were studied with light microscopy. The primordium is tetra-zonate and gives rise to an anatropous ovule. The archesporium may consist of one or more archesporial cells, but only one of them undergoes meiosis, forming a linear shaped tetrad. Normally, only a single megaspore is functional, which is located in the chalazal position, while the others degenerate very soon. The young ovule is hemianatropous but the mature one is anatropous, crassinucellar, and bitegmic; integuments form a zig-zag micropyle. A 7-celled embryo-sac is formed corresponding to the Polygonum type. The present study provides the first report on embryological characteristics in O. schahuensis. Based on our results and in comparison with prior studies, several characters may have potential taxonomic significance for the Hymenobrychis section, such as the tetra-zonate ovule primordium, anatropous ovule type, dermal origin of the integuments, asymmetrical initiation of the outer integument, linear shaped tetrad with the presence of one functional megaspore, and having 2 young ovules but degeneration of one of them.
Keywords : Key words Embryology, Fabaceae, megaspore, Onobrychis, Hymenobrychis, ovule