Heterogeneous-sized Pollen Grains Research Articles

Chromosomal variation in some members of Malvales Juss. from Rajasthan, India

The present paper deals with the meiotic study of 15 species belonging to 7 genera of 3 families of order Malvales i.e. Malvaceae, Sterculiaceae and Tiliaceae from different geographical areas of Rajasthan. Out of 15 species, intraspecific cytotypes at tetraploid and diploid level of Triumfetta rhomboidea has been reported for the first time. The chromosome numbers of 6 species i.e. Abutilon pannosum, Sida ovata, Sida rhombifolia, T. rhomboidea are reported for the first time from India. Whereas, chromosome studies on Melhania magnifolia have been worked out for the first time, also the occurrence of new cytotypes of Abutilon ramosum (2n = 42) are the first record in global context. Meiotic course is found to be abnormal in case of T. rhomboidea, A. pannosum and A. ramosum with the presence of laggards, chromatin bridges, unoriented bivalents and cytomixis, leading to the reduced pollen fertility and heterogenous sized pollen grains.

Chromosome counts, chromosomal pairing, and pollen fertility in thirty-eight species of Asteraceae from Pangi Valley in District Chamba of Himachal Pradesh (India)

The current investigation includes detailed male meiotic studies, chromosomal counts, and pollen fertility on 38 species of family Asteraceae from the Pangi Valley, a part of cold desert Himalayas. The first-ever chromosome counts have been made for seven species viz. Aster albescens Wall. (n = 9), A. heterochaeta C. B. Clark (n = 9), Cirsium involucratum DC. (n = 34), Inula obtusifolia Kern. (n = 8), Saussurea piptathera Edgew. (n = 13), Senecio arnicoides (DC.) C. B. Clark, and Tanacetum robustum Hook f. et Thoms. (n = 9). Besides, new cytotypes are reported for Aster flaccidus Bunge (2n = 2x = 18), A. peduncularis Wall. ex Nees (2n = 2x = 18), and Youngia tenuifolia (Willd.) Babcock & Stebbbins (2n = 4x = 20). Out of the thirty-eight species, six species viz. Crepis multicaulis Ledeb., C. sancta (L.) Babcock, Erigeron multiradiatus (Lindl.) C. B. Clark, Scorzonera divaricata DC., S. arnicoides (DC.) C. B. Clark, and Taraxacum officinale Wigg., showed a number of meiotic abnormalities leading to reduction in pollen fertility and production of heterogeneous-sized pollen grains. The triploid cytotype of T. officinale Wigg. (2n = 24) depicted irregular meiotic course characterized by the presence of high frequency of univalents, abnormal sporads, and pollen malformation. B-chromosome has been reported for the first time in some individuals of S. arnicoides (DC.) C. B. Clark. Compiled information on the worked out species reveals the existence of considerable amount of chromosomal variations in some species involving the role of aneuploidy and polyploidy.

Impaired Male Meiosis and Multiple Associations in <i>Chaerophyllum</i> L. from the Western Himalayas, India

We present a cytological study of species of the genus Chaerophyllum L. (Apiaceae) by analysing five accessions covering three species from the Western Himalayas, India. The species are collected and studied for detailed male meiosis, multiple associations and pollen fertility. All the studied species exist at diploid level (based on x=11), and show a meiotic chromosome count of 2n=22 at diakinesis and metaphase-I, and regular chromosome distributions at anaphases-I/II. C. aromaticum is reported for the first time from India and found to be in conformity with the earlier reports of 2n=22 from outside India. Out of three studied species, two (C. acuminatum and C. aromaticum) showed the presence of multiple chromosomal associations at metaphase-I of meiosis-I. The paper herein discusses for the first time the occurrence of multiple associations in these species. The course of meiosis in all studied species shows impaired meiotic course in the form of cytomixis, chromatin stickiness, laggards and chromatin bridges. Abnormal microsporogenesis results in heterogeneous-sized pollen grains and reduced pollen fertility.

Induction of cytomixis affects microsporogenesis in Sesamum indicum L. (Pedaliaceae)

Cytomixis was recorded during microsporogenesis in sesame (Sesamum indicum L.), a member of the family Pedaliaceae. The phenomenon of cytomixis was observed at various stages of meiosis in 0.5% Sodium azide (SA) treated populations of Sesamum indicum L. Cytomixis was observed to occur through various methods, i.e., by forming cytoplasmic channels and direct fusion of pollen mother cells (PMCs), the former was more frequent than the latter. The migration of nuclear content involved all the chromatin/chromosomes or part of it from donor to recipient cell/cells. Some completely empty meiocytes were also observed. Stickiness, precocious movement, laggards, unorientation and micronuclei were observed in almost all the sets treated with various doses of SA. Increase in the doses of SA had a positive effect on the percentage of PMCs showing cytomixis and chromosomal abnormalities. The impact ofcytomixis on meiotic behaviour, reduced pollen viability and heterogeneous sized pollen grains were observed.

Meiotic Studies in Some Polypetalous Species from District Kangra (Himachal Pradesh), India

At present, meiotic studies have been carried out on a population basis covering 23 species belonging to 13 genera and 10 families of Polypetalae from District Kangra of Himachal Pradesh. New reports in the form of varied chromosome numbers have been marked for the first time on a world-wide basis for 13 species, namely Bupleurum lanceolatum (n=16), Impatiens bicolor (n=8), I. racemosa (n=7), I. sulcata (n=7), Medicago polymorpha (n=16), Fumaria indica (n=8), Geranium lucidum (n=13), G. ocellatum (n=13), Hypericum elodeoides (n=8), H. japonicum (n=16), Malva verticillata (n=21), Epilobium roseum (n=9), Geum roylei (n=14), Rosa macrophylla (n=14) and Triumfetta pilosa (n=16). Six species, namely Boenninghausenia albiflora (n=10), Circaea alpina (n=11), E. palustre (n=18), Rosa brunonii (n=7) and R. indica (n=7), have been cytologically worked out for the first time from India, along with additional cytotypes for 3 Indian materials, namely Abutilon indicum (n=7), E. cylindricum (n=9) and Oxalis corniculata (n=7). Amongst these species, the course of meiosis varies from normal to abnormal in different populations of Malva neglecta, Rosa brunonii and R. indica whereas all the studied accessions of Bupleurum lanceolatum, Geum roylei, Impatiens sulcata, Oxalis corniculata and Rosa macrophylla have been found to be abnormal. The meiotic abnormalities include various phenomenon such as cytomixis, chromatin stickiness, unoriented bivalents, laggards, chromatin bridges and multipolarity at different stages of meiosis along with abnormal microsprogenesis ultimately leading to reduced pollen fertility and formation of heterogenous sized pollen grains.

EMS-induced cytomictic variability in safflower (Carthamus tinctorius L.)

Seeds of safflower (Carthamus tinctorius L.) were subjected to three treatment durations (3h, 5h and 7h) of 0.5 % Ethyl Methane Sulphonate (EMS). Microsporogenesis was carried out in the control as well as in the treated materials. EMS treated plants showed interesting feature of partial inter-meiocyte chromatin migration through channel formation, beak formation or direct cell fusion. Another interesting feature noticed during the study was the fusion among tetrads due to wall dissolution. The phenomenon of cytomixis was recorded at nearly all the stages of microsporogenesis connecting from a few to several meiocytes. Other abnormalities such as laggards, precocious movement, bridge and non-disjunction of chromosomes were also recorded but in very low frequencies. The phenomenon of cytomixis increased along with the increase in treatment duration of EMS. Cells with these types of cytomictic disturbances may probably result in uneven formation of gametes or zygote, heterogenous sized pollen grains or even loss of fertility in future.

Chromosome Information Service (CIS), XVI

Male meiosis and pollen fertility studies have been performed in 35 species belonging to 25 genera and 13 families of Polypetalae from the Dalhousie hills. Impatiens laxiflora (n= 6) was counted chromosomally for the first time. Corydalis cornuta (n=8), Erysimum hieracifolum (n=16), Arenaria serpyllifolia (n=10), Drymaria diandra (n=13), Geranium lucidum (n=14), Nasturtium officinale (n=16), Geum roylei (n=21) and Chaerophyllum reflexum (n=11) are worked out chromosomally for the first time in India. New cytotypes are recorded for Thalictrum saniculiforme (n=14), Drymaria diandra (n=13), Geranium lucidum (n=14) and Chaerophyllum reflexum (n=11). Present chromosome counts for the rest of the species substantiate earlier reports by other researchers. Intraspecific diploid (n=12) and tetraploid (n= 24) cytotypes recorded presently from Dalhousie hills in Oxalis corniculata are morphologically indistinguishable. The phenomenon of cytomixis involving inter PMC (pollen mother cell) migration of chromatin material has been observed in Ranunculus diffusus (n=16), Thalictrum foliolosum (n=7), T. saniculiforme (n=14), Gypsophila cerastioides (n=15), Oxalis corniculata (n=24), Murraya koenigii (n=9), Geum roylei (n=21), Potentilla atrisanguinea (n=21) and Pimpinella diversifolia (n=9). Cytomixis in these species results in various meiotic abnormalities and heterogeneous sized pollen grains. In the remaining species, the meiosis is normal, leading to high pollen fertility.

Male meiosis and microsporogenesis in west Himalayan Cyathula capitata Moq.

The present investigation involves the meiotic studies on three populations of Cyathula capitata Moq. (family Amaranthaceae) from west Himalaya. All the three populations uniformly revealed chromosome count of 2n=34 which is the first ever report for the species. Male meiosis was abnormal in all the populations characterized by occurrence of chromatin stickiness, laggards and bridges leading to abnormal microsporogenesis. The two populations showed the phenomenon of cytomixis resulting into heterogenous sized pollen grains.

Male Meiotic Studies in Some Plants of Polypetalae from Dalhousie Hills (Himachal Pradesh)

Male meiosis and pollen fertility studies have been performed in 35 species belonging to 25 genera and 13 families of Polypetalae from the Dalhousie hills. Impatiens laxiflora (n=6) was counted chromosomally for the first time. Corydalis cornuta (n=8), Erysimum hieracifolum (n=16), Arenaria serpyllifolia (n=10), Drymaria diandra (n=13), Geranium lucidum (n=14), Nasturtium officinale (n=16), Geum roylei (n=21) and Chaerophyllum reflexum (n=11) are worked out chromosomally for the first time in India. New cytotypes are recorded for Thalictrum saniculiforme (n=14), Drymaria diandra (n=13), Geranium lucidum (n=14) and Chaerophyllum reflexum (n=11). Present chromosome counts for the rest of the species substantiate earlier reports by other researchers. Intraspecific diploid (n=12) and tetraploid (n=24) cytotypes recorded presently from Dalhousie hills in Oxalis corniculata are morphologically indistinguishable. The phenomenon of cytomixis involving inter PMC (pollen mother cell) migration of chromatin material has been observed in Ranunculus diffusus (n=16), Thalictrum foliolosum (n=7), T. saniculiforme (n=14), Gypsophila cerastioides (n=15), Oxalis corniculata (n=24), Murraya koenigii (n=9), Geum roylei (n=21), Potentilla atrisanguinea (n=21) and Pimpinella diversifolia (n=9). Cytomixis in these species results in various meiotic abnormalities and heterogeneous sized pollen grains. In the remaining species, the meiosis is normal, leading to high pollen fertility.

Genetic Diversity in Different Populations of Artemisia absinthium Linn. from Kashmir Himalaya

The present study revealed the varied frequencies of natural chromosomal abnormalities in 4 populations of Artemisia absinthium Linn. collected from different altitudes of Kashmir Himalaya. All the populations are diploid showing n=9 with abnormal meiotic behaviour like quadrivalent formation at diakinesis, cytomixis at early prophase-I and laggards at telophases, resulting into reduced pollen fertility. Besides the heterogeneous sized pollen grains, occasionally inter pollen channels were also observed.

Chromatin Transfer during Male Meiosis Resulted into Heterogeneous Sized Pollen Grains in Anemone rivularis Buch.-Ham. ex DC. from Indian Cold Deserts

Presently, detailed cytological investigations have been carried out in 4 accessions of Anemone rivularis Buch.-Ham. ex DC, collected from the cold deserts of Lahaul-Spiti, Kinnaur, and Kullu districts of Himachal Pradesh (India). The phenomenon of cytomixis involving chromatin transfer among proximate pollen mother cells (PMCs) during male meiosis is recorded for the first time in the species. The effects of cytomixis on meiosis and pollen grains have also been discussed. In spite of the existence of intraspecific aneuploid and polyploid cytotypes (2n=14, 16, 24, 28, 48), all the accessions of the species unequivocally share the same diploid chromosome number, 2n=16. The accession studied from Kothi (Kullu) shows perfectly normal meiotic behaviour, cent per cent pollen fertility and uniform sized pollen grains. However, the accessions analyzed from Keylong and Kishori (Lahaul-Spiti) and Sangla (Kinnaur) show the phenomenon of cytomixis involving chromatin transfer among proximate PMCs, and associated meiotic abnormalities like chromosome stickiness, laggards and bridges at anaphase/telophase, micronuclei, some pollen malformation and pollen grains of heterogeneous sizes.

Impact of cytomixis on meiosis, pollen viability and pollen size in wild populations of Himalayan poppy (Meconopsis aculeata Royle)

We report the occurrence of cytomixis in wild populations of Himalayan poppy (Meconopsis aculeata Royle),which is considered to be an important and threatened medicinal plant growing in the high hills of the Himalayas. The impact of cytomixis on meiotic behaviour, reduced pollen viability and heterogeneous-sized pollen grains was also studied. Cytological studies in the seven wild populations from the high hills of Himachal Pradesh revealed that all the Himalayan populations exist uniformly at the tetraploid level (2n=56) on x=14. The phenomenon of chromatin transfer among the proximate pollen mother cells (PMCs) in six populations caused various meiotic abnormalities. Chromatin transfer also resulted in the formation of coenocytes, aneuploid, polyploid and anucleated PMCs. Among individuals that showed chromatin transfer, chromosome stickiness and interbivalent connections were frequently observed in some PMCs. The phenomenon of cytomixis in the species seems to be directly under genetic control; it affects the meiotic course considerably and results in reduced pollen viability.

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-I are tetraploid on x=8. Presence of eight large sized and eight small sized bivalents at M-I, 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.

Meiotic Studies in Species from the Cold Deserts of Lahaul-Spiti and Adjoining Areas (Northwest Himalaya)

Meiotic investigations were carried out on 29 species of 13 Polypetalae families from the cold deserts of Lahaul-Spiti and adjoining areas of north-west Himalaya. Additional/varied cytotypes have been reported for two species for the first time. The present chromosome count of 2n=18 in Hypericum elodeoides adds a new cytotype to the existing diploid (2n=2x=16) chromosome number. The meiotic count of 2n=2x=14 in Potentilla fruticosa var. rigida adds a new diploid cytotype to the already existing tetraploid (2n=4x=28) cytotype. The chromosome numbers of 10 species viz. Aquilegia fragrans (n=7), Silene vulgaris (n=12), Astragalus bicuspis (n=8), Cicer microphyllum (n=8), Potentilla fruticosa var. rigida (n=7), Melilotus officinalis (n=8), Rosa webbiana (n=7), Bergenia stracheyi (n=17), Sedum ewersii (n=11) and Datisca cannabina (n=11) are new records for India. The cytomixis involving the inter pollen mother cell transfer of chromatin is observed in Caltha palustris, Astragalus bicuspis, Meconopsis aculeata, Melilotus officinalis, Potentilla fruticosa var. rigida and Trifolium pratens. In Caltha palustris the cytomixis (20–28%) results into various meiotic abnormalities and heterogeneous sized pollen grains. In other species the frequency of PMCs (pollen mother cells) involved in chromatin transfer is very low (0.1–1%) without affecting the pollen fertility.