B. R. Chaudhary

Effects of EMS and SA on meiotic cells and thymoquinone content of Nigella sativa L. cultivars

The genotoxic effects of EMS (ethyl methane sulphonate) and SA (sodium azide) were examined on meiotic cell division of Nigella sativa L. using two stable cultivars BHUVN-1 and NRCSSAN-1. The percentage of abnormal pollen mother cells (PMCs) increased as the concentration of both mutagens increased. SA turned out to be a superior mutagenic agent to EMS, inducing fewer chromosomal aberrations and more desired mutational changes. Cultivar NRCSSAN-1 proved to be more sensitive than BHUVN-1 to SA treatment; a reverse response, however, was noted with EMS treatment. The study found no perfect correlation between the chromosomal anomalies and pollen sterility. Of the diverse array of mutant populations screened for morphological and biochemical changes, total oil and thymoquinone content were found to be significantly enhanced in NSM8 (a dwarf mutant line).

Nutritional control on sex differentiation in the filamentous green alga Oedogonium hatei Kam.

Summary Effects of various nutrients constituting the Godward and Chu 10 media on oogonial development in Oedogonium hatei , a macrandrous heterothallic alga were studiedWhile Godward medium supported massive vegetative growth, the Chu 10 medium favoured sex differentiation in Ohatei Of the various nutrients of the Godward medium tested deficiency of only NO 3 -N was found inductive for the differentiation of sexContrarily, omission of other nutrients of the Chu 10 medium as well resulted into an increase in the percentage of oogonium which, however, decreased in the medium deficient in K 2 HPO 4 Extra addition of all other nutrients except K 2 HPO 4 , on the other hand, reduced the percentage of oogoniumThe alga grown in the medium containing 3- to 10-fold Ca(NO 3 ) 2 exhibited complete inhibition of sexual differentiation. That the level of NO 3 -N in the nutrient medium is the most crucial factor in the differentiation of sexual structures, whereas PO 4 -P has either no or little effects on the process of sex differentiation was concludedBesides, NO 3 -N and PO 4 -P seemed to exert opposite effects on oogonial differentiation, for which no explanations can be offered at least for the present.

An Investigation on the Cytology of Ulva fasciata Delile

Gametophytic plantsof Ulvafasciata Delile, collected during spring tides from Visakhapatnam, were studicd cytologi cally. The chromosome number was determined to be ten, which is the first record for this species. Nuclear divisions preceding gamete formation in the gametophytic plants were all found to be mitotic. An invariable association beiween one long chromosome and nucleolus at late prophase, presumably representing N.O.-chromosome, is noteworthy.

Intervarietal karyotypic variation in Vicia faba L.

Karyotype analysis of the seven varieties of Vicia faba L., namely BPL-4070, HBP-A, L-82009, IC-526385, IC-424900, IC-391651 and IC-361499 procured from Indian Agricultural Research Institute, New Delhi, was carried out to ascertain whether varietal differences are marked by chromosomal features. All the varieties exhibited diploid status with 2n = 12 chromosomes each, with perceptible differences in the conventional karyotypic features, total chromatin length (TCL) and the total form percentage (TF%). The assessment revealed the asymmetric nature of the karyotypes; telocentric chromosomes are most frequent, representing the advanced status of the V. faba varieties studied. A pair of satellite chromosome was observed in mitotic metaphase in all the varieties except L-82009, in which secondary constriction could not be discerned.

Genome flexibility in a local clone of Chara corallina grown in laboratory cultures

SUMMARYThis communication deals with chromosomal variability in a local clone of Chara corallina Klein ex Wildenow grown under laboratory conditions. Chromosome counts of n = 14, 21, 28, 36 and 42 were made from a single individual plant, the variability existing in different antheridial filaments and even in the adjacent cells of a single antheridial filament. On the basis of frequency, n = 6 chromosomes was assumed to represent the actual chromosome number for the taxon, from which the other numbers had been derived probably by chromosomal non-disjunction. Such a high degree of vulnerability of the sporogenous cells resulting into an astounding variability in the genomic constitution of spermatogenous cells is assumed to possess great genetic potential in the speciation and evolution of the Chara corallina complex.

Nuclear Cytology of Enteromorpha compressa (L.) Grev. from Indian Water

Enteromorpha compressa (L.) Grev. was collected from the coast of Okha (Saurashtra) and the cytology of the alga was studied, using material from nature. It showed normal mitosis. A count of 18 chromosomes was made at late prophases in the somatic cells. The presence of two chromosomes in association with that of the nucleolus, presumably representing the N. O.-chromosomes is a new observation for the species. The results of the present study were discussed in the light of earlier findings.