Development of Male and Female Gametophyte in Symphytum orientale L. (Boraginaceae)

Abstract

The presented study elucidates developmental features of male and female gametophyte in Symphytum orientale L. (Boraginaceae). Flower buds were collected from natural habitats (İstanbul-Turkey) in March-April. The anthers of S. orientale were tetrasporangiate with a persistent epidermis and its wall development conformed to the Dicotyledonous type. The endothecium developed fibrous wall thickenings. The middle layer was short-lived and the cells of the glandular tapetum became double nucleated. In the microspore mother cells cytokinesis originated simultaneously after meiosis and the microspore tetrads were tetrahedral or isobilateral. The mature pollen grains were 3-celled when spread to environment. The ovule was hemianatropous, unitegmic and tenuinucellar. The megaspore mother cell functioned directly from the archesporial cell. Polygonum type embryo sac developed from the chalazal megaspore of a linear tetrad generated after meiosis. The synergids were pyriform and the polar nuclei fused shortly before fertilization. The antipodal cells were large and persistent at the stage of globular embryo. Embryogenesis followed the Chenopodiad type and the endosperm represented cellular type. The detailed embryological data of Symphytum orientale L. (Boraginaceae), which is a herbaceous and perennial flowering plant will improve our knowledge of its reproductive behaviour, and provide to comprehend taxonomic connection with related taxa within the Symphytum/Boraginaceae.