Thirteen species among eight genera in Cupressaceae sensu stricto were studied on somatic chromosome bandings by sequential fluorescent staining with chromomycin A3 (CMA) and 4',6-diamidino-2-phenylindole (DAPI). All species were diploid (2n=22) and had symmetric and homogeneous karyotype. Two CMA-bands appeared on chromosome complements of Callitris rhomboidea, Chamaecyparis obtsusa, Ch. pisifera, Cupressus lusitanica, Juniperus rigida, Microbiota decussate, Platycladus orientalis, Thuja plicata, and T. standishii. Actinostrobus pyramidalis, Ch. lawsoniana, and Cup. duclouxiana had four CMA-bands. Cupressus macrocarpa had six CMA-bands. CMA-bands appeared at interstitial region of chromosomes and their location was coincided with the site of secondary constrictions in all species. Microbiota decussate had unique weak CMA-bands at the proximal regions of 10 chromosomes in addition to two bright CMA-bands. After DAPI-banding whole chromosome arms of each species fluoresced excepting for region of CMA-bands. Cupressus duclouxiana had weak DAPI-bands on few chromosomes.
Meiotic behaviour of plant chromosomes is influenced by both genetic and environmental factors. The present paper shows the affect of abnormal meiosis on pollen fertility. Meiotic restitution is considered to be a common mechanism of polyploidization in plants and hence is one of the most important processes in plant speciation. Pollen mother cells (PMCs) of diploid potato from anthers at different stages of meiotic process were analyzed for their chromosomal behaviour and irregularities. Pollen morphology was also studied through SEM as it is significantly helpful at the generic and specific level. Various meiotic irregularities were observed: univalent and multivalent formation, chromosome bridges, fragments, lagging chromosomes etc. B-chromosome was first time reported in wild diploid potato, though the frequency of the same was less. Specie was identified as Solanum chacoense.
Male meiotic studies in ten species of grasses (Poaceae) were carried out from District Kinnaur, Himachal Pradesh, India, between the altitudinal ranges of 2000 to 3080 m. All the species were worked out cytologically for the first time from the study area. The hexaploid cytotype in Thysanolaena agrostis (n=33) made new addition for the species on a worldwide basis, supplementing the earlier report of n=11 and 12. The meiotic course in all the species studied was found to be abnormal. Cytomixis in two species, Apluda mutica and Elymus dahuricus was reported here for the first time. Besides abnormal meiotic course the microsporogenesis was found to be normal in all the species but these abnormalities results in the reduction of pollen fertility in the plants.
The present meiotic study is on four accessions from Sirohi District, Rajasthan show the same chromosome number 2n=40 which is at octaploid level based on x=5. These populations are characterized with highly abnormal meiotic behavior with the presence of multivalent, laggards, secondary associations, abnormal spindle formation, precocious disjunction of chromosomes, abnormal microsporogenesis and heterogenous sized sterile and fertile pollen grains. These anomalies lead to low pollen fertility.