First detection of cytomixis and its consequences in Thalictrum cultratum Wall. (Ranunculaceae)

Resumo

In current paper, we studied the meiotic chromosome number and details of cytomixis recorded for the first time in Thalictrum cultratum Wall. from the high altitude areas of northwest Himalaya (India). Cytomixis, the phenomenon of inter PMC (pollen mother cell) migration of chromatin material has been reported in many angiosperms and other groups of plants, but there is no published report in Thalictrum cultratum. All the presently studied accessions of the species existed at diploid level (x = 7). The present chromosome count of n = 14 has been reported for the first time from the study area. The cytological stability of any plant is an important consideration in view of its existence in nature. Meiotic disturbances can impose threat to the reproductive potential of plant. Current study reveals the occurrence of inter PMC migration of chromatin material. In present investigation, the phenomenon of cytomixis can be observed between 2 to 9 PMCs. Chromatin migration occurs through narrow and broad cytoplasmic channels or occasionally fused together during metaphase-I and anaphase-I. Cytomixis resulted in the formation of hypo- (n = 2, 2 + 1 small fragment, n = 3 + 3 small fragments, 4, 5 + extra mass of chromatin, 13) and hyperploid (n = 7 + 2 small fragments, 8 + 2 small fragments, 14, 14 + 2 small fragments, 15) PMCs, variable sized pollen grains and pollen sterility (20%). The current study reveals that cytomixis is responsible for formation of PMCs with variable chromosomes (hypoand hyperploid) and pollen grains of heterogeneous sizes and pollen sterility in T. cultratum. This is the first report of cytomixis in the species.