ON THE REPRODUCTIVE BIOLOGY OF TRIBULUS TERRESTRIS L. (ZYGOPHYLLACEAE): EMBRYOLOGICAL FEATURES; POLLEN AND SEED VIABILITY

An embryological study of Tribulus terrestris from the Bulgarian flora was carried out. The anther is tetrasporangiate and its wall, the development of which follows the Dicotyledonous type, consists of epidermis, fibrous endothecium, two middle layers and glandular tapetum. Different types of microspore tetrads are formed after simultaneous microsporogenesis. The mature pollen grains are two-celled. The mature ovule is anatropous, bitegmic, crassinucellate with one-celled archesporium. The development of the embryo sac follows the Polygonum (monosporic) type. The formation of endothelium and hypostase were reported. The legitimate embryo and endosperm develop after double fertilization. Initially, the endosperm is nuclear. The embryogenesis runs according to the Solanad type. A high pollen and embryo viability was estimated.