MEGAGAMETOPHYTE AND EMBRYO DEVELOPMENT IN FIVE SPECIES OF ASTRAGALUS (FABACEAE)

The development of the megagametophyte, embryo and the endosperm in astragalus eriocarpus (sect. malacothrix), a. glaucacanthus (sect. poterion), a. remotijugus (sect. caprini), a. chrysostachys (sect. hymenostegis) and a. compactus (sect. rhacophorus) were examined. the ovule are campylotropous, bitegmic and crassinucellate; integuments form a zig-zag shaped microphyle. the embryogenesis was similar in the species. megagametophyte development follows the monosporic polygonum type and the embryo development follows the onagrad type. the fusion of the polar nuclei, development of the endosperm, digestion of the nucellus, seed abortion and suspensor development show major differences among studied species. furthermore, the size and shape of the suspensor is quite variable among the five species. these characters are compared with the other species of astragalus and also their phylogenetic significance is discussed. also we describe a case of polyembryony for the first time in a. remotijugus.