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Summary Cytological investigations carried out on a population basis in Astragalus chlorostachysLindl. which exists at diploid level (n=8) revealed the presence of quadrivalents, the late disjunction of 1-4 bivalents and some pollen sterility (34%) in 1 accession collected from Koksar, at 3140 m in the Lahaul Valley (Lahaul-Spiti, Himachal Pradesh). The presence of quadrivalents in this diploid species seems to be a consequence of reciprocal translocations. The occurrence of structural heterozygosity in the species has been reported here for the first time. All of the other populations showed normal bivalent formation and regular sporad generation and 100% pollen fertility. The paper here discusses in detail the course of meiosis and the effect of multivalent formation and non-synchronous disjunction of bivalents on meiotic course and pollen fertility.

SummaryThe phenomenon of cytomixis involving chromatin transfer and spindle abnormalities were recorded for the first time in the diploid (nϭ6) accession of Plantago lanceolata scored from Parvati Valley, Kullu District, Himachal Pradesh (India). Cytomixis with chromatin transfer involved 2-3 PMCs (pollen mother cells) at different stages of meiosis from early prophase-I to T-II, but the maximum frequency of PMCs involved in cytomixis was recorded during the early prophase stages of meiosis-I (11.03%). The transfer of chromatin material among meiocytes was observed to be both partial and complete resulting into PMCs with hypo-and hyperploid chromosome numbers (2nϭ14, 15). During cytomixis, nucleolus also transmigrated to neighbouring PMCs and the PMCs with supernumerary nucleoli also resulted. Other meiotic abnormalities associated with cytomixis included chromatin stickiness, out of plate bivalents, laggards, bridges, unoriented chromosomes during A-I/T-I and A-II/T-II, and micronuclei. The effect of chromatin transfer, spindle abnormalities and associated meiotic anomalies on meiotic behaviour, pollen fertility and pollen size has been discussed. The cytomixis in P. lanceolata seems to be a natural phenomenon under genetic control and certainly have played a role in the origin of aneuploids and polyploids. Plantago lanceolata L. (Family: Plantaginaceae), a common weed of cultivable lands, is known by several different local names at different places including, English plantain, Ribble grass, Black plantain, Snake plantain, Ribwort plantain, and Lambs's tongue. The species, which is highly polymorphic, is widely distributed in Europe from South Iceland and east to Spain, and Northern and Central Asia. Besides, it had also been introduced into several countries and is considered as an invasive weed in North America. In India, the species commonly occurrs from Kashmir to Shimla between 1500-3000 m along roadsides, meadows, ditches and wastelands. Its leaves and seeds have been used extensively as antibacterial, antidotic, astringent, antihaemorrhagic, demulcent, expectorant, laxative, ophthalmic, poultice and diuretic treatments. Internally, these have been used in the treatment of a wide range of complaints including diarrhoea, gastritis, enteritis, peptic ulcers, irritable bowel syndrome, haemorrhage, haemorrhoids, cystilis, goitre, liver disorders, worms and hay fevers (Brown 1995, Chevalier 1996. Externally, plants have been used in treating skin inflammations, malignant ulcers, cuts, dog bites, eczema, herpes, and stings (Grieve 1984). Because of its immense medicinal importance and wide distribution, the species has been studied chromosomally by several researchers from different regions of the world depicting an array of chromosome numbersϭ2nϭ12, 13, 14, 24, 96 (Darlington and Wylie 1955, Löve and Löve 1956, 1975, Fedorov 1969, Moore 1973, 1977, Goldblatt 1981, 1985, 1988, Kumar and Subramanian 1986, Goldblatt and Johnson 1990, 1991, 1994, 1998, 2000, 2003 * Corresponding author, e-mail: vksinghal53@gmail....

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Despite the presence of intraspecific polyploidy (2x, 4x, 5x and 6x) in Agrimonia eupatoria, origin of these cytotypes has never been addressed adequately. The aim of the present study was to record the original chromosome counts and characterize chromosomal pairing during meiosis and microsporogenesis in the 5x cytotype, and discussing the hypothesis regarding the possible origin of polyploid cytotypes (4x, 5x and 6x) in the species. The geographical distribution pattern of cytotypes in the Indian Himalayas and elsewhere has also been analyzed. The present meiotic analysis revealed three chromosomes counts, the tetraploid (2n = 4x = 56), the pentaploid (2n = 5x = 70) and the hexaploid (2n = 6x = 84) cytotypes based on x = 14. Meiotic course was perfectly normal in the 4x and 6x cytotypes resulting into high pollen fertility (94-100 %). Meiotic course in the imbalanced 5x cytotype has been found to be irregular characterized by the presence of high frequency of univalents at diakinesis and metaphase-I. Abnormal meiotic course contributed towards high pollen sterility (74-88 %). Even the apparently fertile/stained pollen grains were of irregular shape and of heterogeneous sizes. Meiotic behaviour of the 5x cytotype is like typical of allopolyploid. Individuals of 5x cytotype did not produce seeds and propagate vegetatively (root suckers) while 4x and 6x cytotypes exploited sexual (seeds) as well as vegetative means for propagation. Chromosomal pairing in pentaploid cytotype is like typical of an allopolyploid and we assume that it might have originated owing to natural inter-cytotype hybridization between 4x and 6x cytotypes in a mixed population. Analysis of geographical distribution pattern of cytotypes shows that Indian Himalayas represent the most cytotype-diverse region for A. eupatoria with the existence of all the four cytotypes (2x, 4x, 5x, 6x). This shows the dynamic nature of the species at chromosomal level in this part of the world.