Cytology of Caltha palustris L. (Ranunculaceae) from Cold Regions of Western Himalayas

Caltha palustris L. (Ranunculaceae), popularly known as Kingcup or Marsh Marigold is a polymorphic species distributed in the cold temperate regions of western Himalayas. The species exhibits considerable amount of intraspecific morphological and chromosomal diversity involving polyploidy, aneuploidy and hybridization. Besides, some individuals also show the presence of B-chromosomes. Presently three populations from the cold desert region of Kullu and Lahaul-Spiti districts of Himachal Pradesh have been studied for detailed meiotic studies. These populations which uniformly show the presence of 16 bivalents at M-1 are tetraploid on x=8. Presence of eight large sized and eight small sized bivalents at M-1, suggest these populations to be allotetraploid. Majority of the individuals in one of the populations show normal meiotic course and high pollen fertility. However, in the other two populations, the individuals show inter PMC transfer of chromatin material at various stages of meiosis and associated meiotic irregularities such as chromosome stickiness, pycnotic chromatin, late disjunction of bivalents, micronuclei and chromatin bridges at anaphases and telophases. Besides, the chromatin migration also results in the formation of aneuploid with 8, 11 and 13 bivalents and anucleated PMCs. Although the phenomenon of cytomixis does not affect apparent pollen fertility but it surely resulted into heterogenous sized pollen grains. Although the genetic constitution and fate of such apparently fertile heterogenous sized pollen grains is yet to be ascertained, but their possible role in the development of individuals with varied chromosome number could not be ruled out. The phenomenon of chromatin transfer in the species seems to be under direct genetic control as the individuals with and without cytomixis found to grow in the same environmental conditions.