Cyto-morphological features of Portulaca tuberosa Roxb.

Abstract

The development of the microsporangium of Portulaca tuberosa, Roxb., is described. Multinucleate tapetal cells and tapetal nuclear fusion are met with. The diploid number of chromosomes was found to be 18, which was confirmed by the meiotic counts. Diploid chromosome numbers of two other species of Portulaca are also recorded for the first time. Meiosis is normal and the microspore is two-celled at the shedding time. Development of the ovary and the ovules is described in some detail. Embryo-sac formation and embryo development are of the normal type. The possible meaning of the tapetal nuclear fusion is discussed from the view-point of the nutritive function of the tapetal cells. The importance of recounting morphological details in spite of their repetition, is discussed in the light of observations recorded in this paper. The position of Portulacaceœ is considered cyto-taxonomically.