Comparative study of gametophyte development in the some species of the genus Onobrychis: Systematic significance of gametophyte futures

Abstract

Male and female gametophytes have special characters that show a great variety in different taxa. In this study, gametophytes of four species belonging to three sections of the genus Onobrychis Mill. were studied with light microscopy. Results showed that the ovular primordium is tetra-zonate and gives rise to an anatropous ovule. The archesporium may consist of one or more archeosporial cells, but only one of them undergoes meiosis, forming a linear or T-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 hemi-anatropous but the mature is anatropous, crassinucellar and bitegmic; integuments form a zig-zag micropyle. A 7-celled embryo-sac is formed corresponding to the Polygonum type. Based on our results, the ovular variable characters are the form and condition of ovary, presence or absence of ovary peduncle, the number and condition of ovule in ovary, length and width of ovule, length and width of embryo sac, number of layers in outer integument, condition of megaspore, alignment pattern of the integuments, asymmetrical initiation of the outer integument, shape of tetrad with the presence of one functional megaspore and so on. The separator characters in male gametophyte are including tri-cellular pollen grains and the number of tapetum nuclei. According to our study the female gametophyte characters are more variable than male gametophyte. The present study provides the first report on embryological description in the genus Onobrychis and also in section Heliobrychis.

Embryology ofOnobrychis persicaSirj. and Rech.f. (Fabaceae) and its systematic implications

“…The present study indicates that the chalazal megaspore is functional like other species of Onobrychis that we studied before (Chehregani et al 2011) and Vigna unguiculata L. Walp. (Salinas-Gamboa et al 2016).…”

“…In O. persica, there is just one middle layer in the anther the mature legume contains one seed, but every so often the legume contains two seeds. Typically Onobrychis is identified and separated from the other groups because of its one seed legume (Mabberley 1990;Lock 2005) and there are numerous seeds in different Fabacean species (Riahi and Zarre 2009;Chehregani et al 2011). It is a remarkable finding that we have observed two seeds in legume of O. persica.…”

“…In O. persica, the inner integument, as our previous studies on Onobrychis (Chehregani and Tanaomi 2010;Chehregani et al 2011) and most Fabaceae, consists of two cell layers (Smith 1956;Dnyansagar 1957;Hindmarsh 1964;Deshpande and Bhasin 1976;Rembert Junior 1977;Pullaiah 1994, 1999;Moço and Mariath 2003;Riahi and Zarre 2009;Vardar 2013). However, in Glycine javanica L., Tephrosia, Clitoria ternata L., Pongamia glabra Vent.…”

“…The tetrads of megaspores in O. persica, most legumes and our previous study on Onobrychis except for O. schahuensis are T-shaped (Table 1) (Chehregani and Majd 1992;Faigo´n-Soverna et al 2003;Riahi et al 2003;Chehregani et al 2011). But the tetrad shape in Fabaceae can be different (Moço and Mariath 2003;Galati et al 2006;Rodriguez-Pontes 2008).…”

“…Embryological studies in Papilionoideae (Ashrafunnisa and Pullalah 1999;Riahi et al 2003;Faigo´n-Soverna et al 2003;Moço and Mariath 2003;Zulkarnain 2005;Galati et al 2006;Rezanejad 2007;Rodriguez-Pontes 2008;Riahi and Zarre 2009;Salinas-Gamboa et al 2016) and a few embryological studies in Onobrychis (Chehregani et al 2011;Ghassempour and Majd 2012) have provided useful characters in embryogenesis and classification. Therefore, in this study we investigate detailed embryological processes in O. persica using bright field, polarizing and fluorescence microscopy and compare them with some spices in this genus.…”