Embryological studies in the composite astereae-II

Abstract

The embryology of Felicia bergeriana O. Hoffm, Conyza stricta Willd. and Erigeron bonariensis L. has been studied. The anthers are tetrasporangiate in C. stricta and F. bergeriana and bisporangiate in E. bonariensis. The anther wall consists of epidermis, endothecium, middle layer and tapetum. Binucleate, tetranucleate and 12 nucleate tapetal cells have been observed respectively in E. bonariensis, C. stricta and F. bergeriana. The tapetum forms periplasmodium and endothecial thickenings are formed in all the species studied. Pollen grains are shed at 3 celled stage. The ovule is anatropous, unitegmic and tenuinucellate. The mature embryo sac is 8 nucleate polygonum type in all the species studied. As many as 6 antipodal cells in Erigeron bonariensis and 12 in C. stricta are observed due to secondary multiplication. In F. bergeriana the antipodal cells become 2–4 nucleate. The persistence of antipodal tissue and its penetration into chalazal region confirm haustorial nature. The endosperm is nuclear in E. bonariensis and C. stricta and cellular in F. bergeriana. The outer cells of endosperm form jacket layer which persists surrounding the mature embryo. The embryo development is of the asterad type and resembles the Senecio variation.