Cytology ofRanunculus laetusWall. ex Royle from cold desert regions and adjoining hills of North-west Himalayas (India)

Abstract

-Present work pertains to the cytological investigations performed in Ranunculus laetus for the fi rst time from Indian cold deserts and adjoining high hills of North-west Himalayas which covers Chamba, Kinnaur, Kullu and Lahaul-Spiti districts of Himachal Pradesh. We here also report for the fi rst time the presence of 1 B-chromosome in two accessions studied from Dalhousie hills. Twelve accessions scored presently from these regions uniformly shared the same meiotic chromosome number, n=14 and existed at tetraploid level (based on x=7). Of these, eight accessions showed abnormalities during male meiosis, such as pollen mother cells (PMCs) involved in chromatin transfer at different stages of meiosis, chromosome stickiness, pycnotic chromatin material, out of plate bivalents at metaphase-I, nonsynchronous disjunction of some bivalents, and laggards at anaphases/telophases. Consequent to these meiotic irregularities, microsporogenesis in meiocytes is abnormal characterized by the presence of dyads, polyads, and micronuclei and included micronuclei in sporads. These irregularities during meiotic course resulted into varying percentage of pollen sterility (9-31%) and pollen grains of heterogeneous sizes. The remaining four accessions showed regular meiotic course, normal microsporogenesis and nearly cent percent pollen fertility (97.90-100%).

Occurrence of Syncytes: A Possible Mechanism Owing to the Origin of Polyploid Cytotypes in <i>Achillea millefolium</i> L. within Indian Himalayas

“…Spontaneous occurrence of syncytes due to the fusion of adjacent meiocytes had been reported for the first time by Gates and Rees (1921) in Lactuca sativa. Since then, the phenomenon has been reported in a number of flowering plants by Levan (1941), Price (1956), Katayama (1964), Mehra and Kalia (1973), Rao and Koduru (1978), Sarbhoy (1980), Padmaja (1988), Caetano-Pereira et al (1999), Mendes-Bonato et al (2001, Boldrini et al (2006); Risso-Pascotto et al (2006), Singhal and Kumar (2008; Kim et al (2009), Singhal et al ( , 2011; Kumar et al (2010Kumar et al ( , 2011; Malik et al (2014). In the present study, we report for the first time the formation of syncytes through fusion of two to three adjacent PMCs in the diploid populations of Achillea millefolium.…”