Aberrant Male Meiosis, Pollen Sterility and Variable Sized Pollen Grains in Clematis montana Buch.-Ham. ex DC. from Dalhousie hills, Himachal Pradesh

摘要

Chromosomal studies on Clematis montana from Dalhousie hills, Himachal Pradesh, India have led to the identification of an accession that exhibited aberrant male meiosis, pollen sterility and heterogeneous sized fertile pollen grains. The accession, which exists at diploid level (n=8), depicts the phenomenon of cytomixis involving chromatin transfer among proximate meiocytes (PMs). The chromatin transfer in the PMCs has also caused various meiotic irregularities like chromatin stickiness, interbivalent connections, unorganized and pycnotic chromatin, laggards/chromatin bridges during anaphases/telophases, micronuclei and included micronuclei in microspores, triads and polyads. Consequent to cytomixis and associated meiotic irregularities, the products of PMCs result in some pollen sterility and variable sized fertile pollen grains. Though the Cytological status of such variable sized pollen grains could not be ascertained at present, the large sized pollen grains, which are almost double sized, may be of '2n' constitution and play an important role in the origin of intraspecific polyploidy in the species. The small sized fertile pollen grains which are the products of hypoploid PMCs could lead to the origin of aneuploids. Similar effects of cytomixis on meiotic course resulting in pollen malformation have been reported earlier in a number of species by the authors from this laboratory.