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Summary Heracleum pinnatum C. B. Clarke (Apiaceae) collected from the cold deserts of Ladakh Himalaya, Jammu and Kashmir, India, is cytologically analyzed for the first time, revealing a diploid chromosome count of 2n=22. During meiosis, the majority of the pollen mother cells (PMCs) exhibited 11 bivalents, equal segregation of chromosomes during anaphases, regular tetrads, and normal-sized pollen grain formation. Occasionally, two proximate PMCs fused during the early stages of prophase-I and resulted in the formation of syncytes. The frequency of such syncytic meiocytes was low (3.72-3.96%) but these could be easily detected in the preparations due to their large size compared to typical PMCs. Also, the syncytes depicted a meiotic chromosome count of 2n= 44 as confirmed from the presence of 22 normal bivalents. Further, meiotic course in such tetraploid PMCs was also observed to be perfectly regular, leading to the formation of 2n or larger-sized pollen grains that are almost double the size of typical n pollen grains. Such larger-sized 2n pollen grains could also be differentiated on the basis of their shape. Additionally, a significant frequency of PMCs also showed the phenomenon of cytomixis involving transfer of chromatin material resulting in aneuploid meiocytes. Whole chromatin transfer during cytomixis among neighboring PMCs at early stage of meiosis-I lead to the formation of PMCs with double the chromatin material. Syncytes resulted as a consequence of fusion of meiocytes during the early stages of meiosis-I could be attributed to low temperature stress conditions prevailing at the time when the plants enter the flowering stage. It is quite possible that such apparently fertile 2n pollen grains originating from syncytes might play a role in the origin of polyploids in the species.

The present communication reports the meiotic analysis on three wild populations of Rorippa palustris collected from Ladakh division, Jammu & Kashmir and records the existence of first ever intraspecific euploid cytotypes, the diploid (2n=14) and hexaploid (2n=42). Beside chromosome number, the two cytotypes also differ in morphometric parameters such as flower color, plant height, size of leaf and number of leaves per plant. The 6x plants grow much taller and robust compared to those of 2x and size of stomata and pollen grains are also significantly larger in the 6x compared to the 2x. Both cytotypes exhibit normal meiotic behavior characterized by normal chromosome pairing, regular segregation of chromosomes and nearly perfect pollen fertility.

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Meiotic studies have been carried out on three plants of Leontopodium jacotianum from Cold deserts of Ladakh. The chromosome number of n=24 counted in all the plants adds a new tetraploid cytotype for the species. The plants collected from Zoji-La showed a normal meiotic course leading to high pollen fertility. However, the plants collected from Sankoo region of cold deserts of Ladakh, Jammu, and Kashmir showed abnormal meiosis caused by structural heterozygosity for reciprocal translocations. The structural heterozygosity was observed for the first time in the species. Chiasma frequency was also calculated by using one-way analysis of variance (ANOVA) in the plants to see the effect of reciprocal translocations. Besides reciprocal translocation, the plant also showed various meiotic abnormalities in the form of early disjunction of bivalents, chromatin bridges, and laggards. Structural heterozygosity and other meiotic abnormalities in the plant seem to be responsible for a reduction in pollen fertility.