Asplenium ruta-muraria, Woodsia asiatica and Cheilanthes argentea collected in Russian Altai showed the chromosome numbers of n=72_II, 2n=82 and 2n=60 (n=30_II), respectively. Sporophytes of Asplenium ruta-muraria and Woodsia asiatica were produced apogamously on agar medium and their mitotic chromosome numbers were 2n=72 and 2n=41, respectively. The haploid sporophyte formation of Asplenium ruta-muraria and that of Woodsia asiatica were reported here for the first time.

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This study deals with the detailed analysis on various meiotic abnormalities in the tetraploid cytotype (2n=4x=48) of Physalis peruviana L. The meiotic abnormalities include secondary associations of bivalents, stickiness of chromosomes, multivalents and univalents, and unoriented bivalents during metaphase-I, non-synchronization in the separation of some bivalents, laggards, chromatin bridges and cytomixis at various meiotic stages besides aberrant microsporogenesis. In spite of all these abnormalities, distribution of chromosomes at anaphases found to be normal. Microsporogenesis includes monads, dyads and tetrads with micronuclei besides normal tetrads, consequently reducing the pollen fertility (76%).

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Heavy metals are one of the important classes of environmental hazards. They become toxic, when they are not metabolized by the body and accumulate in the soft tissues. Heavy metals may enter the human body through food, water, air, or absorption through the skin when they come in contact with humans in agriculture and in manufacturing, pharmaceutical, industrial, or residential settings. As many heavy metals are mutagenic and clastogenic, they cause teratogenic or carcinogenic effects. Dhaincha [Sesbania cannabina (Rets.) Pors., Fabaceae] is a multipurpose legume crop and is adaptable to adverse climatic conditions such as water logging, drought etc. and is widely used as green manure crop. Effects of lead on germination percentage, survival percentage, pollen fertility and meiotic divisions of S. cannabina were studied. For this purpose soaked seeds of S. cannabina were treated with different concentrations of lead nitrate solution i. e. 25, 50, 100 and 200 ppm for 3 h and treated seeds were sown to raise the population. There was dose dependent effect of the mutagenic treatments on chromosomal aberrations and pollen fertility. Increase in various types of meiotic aberrations and reduction in pollen fertility percentage were observed at all the doses of treatment. Higher frequency of chromosomal anomalies was observed at maximum dose of treatment.

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An attempt has been made to study the potential of mutagenic effects of gamma rays and sodium azide (NaN₃) on the meiotic cells of Vigna unguiculata (cowpea). Cowpea being a self-pollinated vegetable crop has very limited genetic variability therefore induced mutation can provide additional source of mutation in recent plant breeding programmes. Chromosomal aberrations like unorientation, multivalents, laggards, bridges, micronuclei, stickiness and precocious movement etc. were noticed in mutagen treated populations. Chromosomal aberrations were found to be correlated with the concentrations of physical and chemical mutagens individually as well as in combination. On the basis of our experimental results it can be concluded that the combined treatment proved to be more effective in inducing abnormalities and pollen sterility as compared to individual treatment sets.

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Gametogenesis is cytologically affected by a large number of genes. Mutations induced in these genes by mutagenic environmental hazards such as gamma rays, chemical such as EMS may cause anomalies that may appear in form of pollen sterility. Due to effect of maximum dose of combination treatment of gamma rays and ethyl methane sulfonate (500Gy+ 0.5% EMS) applied on the seeds of Linum usitatissimum L., there is appearance of phenomenon known as chromosome elimination which is resulted in form of small microcytes resulting into sterile pollen grains. Migration of micronuclei towards the wall of microspore and its separation as a bud or microcyte might be the possible cause of pollen sterility.

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Rheum, common name rhubarb is a source of number of chemical compounds like emodin, rutin and rhein. Plants are used as drugs, laxative and purgative. The two species of this genus viz R.emodi and R.webbianum grow wild in the Kashmir Himalaya. Keeping the threat status and the economic importance of these two species into consideration, an attempt was made to study their detailed meiotic course. Meiotic analysis revealed n=11 (2x) and n=22 (4x) as the chromosome numbers in R.emodi and R.webbianumi respectively. Cytological study for R.webbianum has been carried out for the first time from the study area also it is the first report of structural heterozygosity in R. emodi.

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Chromosome numbers of 24 species (34 populations) of eight families under subclass Monochlamydeae of the dicots, collected from North India are presented. Seven new chromosome counts are recorded for six species: Aerva scandens (n=27), Croton bonplandianum (n=25), Euphorbia helioscopia (n=14), Euphorbia hirta (n=20), Boerhavia diffusa (n=26, 52) and Mirabilis jalapa (n=27). Indian populations of Polygonum multiflorum (n=11, 22) are counted for the first time. Number of total species and their chromosome numbers of presently investigated genera and their families have been reviewed to find out polyploidy percentage and probable base numbers in India.

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