Showing papers on "Nigella damascena published in 1969"
TL;DR: It is interpreted that the observed differences between Vicia and Nigella are due to the presence and absence of heterochromatin in their chromosome complements respectively.
Abstract: The chromosome breaking effect of mitomycin C, methyl methanesulfonate, maleic hydrazide, 8-ethoxycaffeine and gamma rays on the primary root meristematic cells of Nigella damascena was studied. All the agents tested except 8-ethoxycaffeine, produced relatively fewer aberrations, when compared to Vicia faba cells, though both the species have nearly similar total chromosomal length. Test for the presence of heterochromatin in Nigella gave negative results and it is interpreted that the observed differences between Vicia and Nigella are due to the presence and absence of heterochromatin in their chromosome complements respectively. The role of heterochromatin in the production of chromosome aberrations and its significance in evolution are briefly discussed.
78 citations
TL;DR: It is suggested that this vacuolar structure associated with the onset of flowering in Nigella damascena represents an accumulation, in the cells of the floral apex, of some synthetic pro...
Abstract: Both light and electron microscope observations were recorded of a vacuolar structure which is associated with the onset of flowering in Nigella damascena. This structure has been observed in both chemically fixed and fresh-frozen sections. It is a spherical, occasionally lobed, rough-surfaced structure found in both dividing and non-dividing cells of the corpus and pith – rib meristem of the prefloral and floral apex. Less frequently these structures were located in the cells of the floral organs and occasionally at the tips of young bracts and leaves. The slight differential staining response of these structures suggests some internal differentiation and this is supported by electron micrographs. At least three regions of differing electron density can be recognized. While small pieces of unit membrane can be found attached to the outer surface, this structure is not membrane bound. We suggest that this vacuolar structure represents an accumulation, in the cells of the floral apex, of some synthetic pro...
9 citations
01 Jan 1969
TL;DR: The genus Nigella is unique in exhibiting connation of carpels and an involucre of much dissected leaves beneath each flower, which prompted the present investigation on Nigella damascena L.
Abstract: Introduction In the order Banales, Ranunculaceae are the largest family comprising about 49 genera and about 500 species. The family is characterised for its remarkable combination of primitive and advanced characters viz. actinomorphic or zygomorphic flower; free or fused carpels; multiovulate follicles or uniovulate achenes; crassior tenuinucellar ovules which may be ategmic, unitegmic or bitegmic; persistent or ephemeral antipodal cells and occurrence of mono, bi, and tetrasporic embryo sac development. The genus Nigella is unique in exhibiting connation of carpels and an involucre of much dissected leaves beneath each flower. Although many taxa of this family have been investigated from the point of comparative embryology, information on Nigella is meagre. This is particularly so with regard to the microsporangium, microsporogenesis and male gametophyte. This prompted us to take up this present investigation on Nigella damascena L. We are grateful to Professor B. M. JOHRI for encouragement and Dr. K. M. M. DAKSHINI for valuable suggestions.
1 citations