Chromosome numbers in Tripleurospermum Sch. Bip. (Asteraceae) and closely related genera: relationships between ploidy level and stomatal length

This study includes 24 reports of chromosome counts in Tripleurospermum Sch. Bip. (20 taxa), Anthemis L. (1 species) and Matricaria L. (3 taxa) belonging to the tribe Anthemideae of the family Asteraceae from Turkey. Chromosome numbers of these taxa are 2n = 2x = 18, 3x = 27 and 4x = 36. Nine counts are new reports, one is not consistent with previous report, and the remainder confirm earlier information. Statistically significant differences depending on ploidy level, stomatal length or environmental factors such as altitude were determined in Tripleurospermum. Several systematic and evolutionary aspects of the genera are discussed in the light of chromosomal data.     

Cytological studies of Angiosperms (174 species) from District Kangra,Himachal Pradesh (India)

During the present study, 360 populations of 174 species belonging to 82 genera and 23 families of dicots have been cytologically worked out from different localities of District Kangra (Himachal Pradesh) between 550 and 3,800 m altitude. As many as 10 species including Berberis ceratophylla (2n = 28), Caltha alba (2n = 32), Corydalis meifolia (2n = 16), C. thyrsiflora (2n = 16), Impatiens reidii (2n = 14), Indigofera hamiltonii (2n = 16), Potentilla thomsonii (2n = 14), Sedum trifidum (2n = 36), Stellaria semivestita (2n = 26) and Viola canescens (2n = 12) have been cytologically worked out for the first time at world level. New intraspecific diploid cytotypes have been recorded in 11 species while new intraspecific tetraploid cytotypes are noticed in 15 species. B-chromosomes have also been reported in 3 species viz. Anemone obtusiloba, Clematis grata and Ranunculus diffusus for the first time at world level. The species of the area are active state of evolution, depicting heterogeneity in chromosome numbers involving polyploidy (48 species, 28.18 %) as well as irregular meiotic behavior. The meiotic abnormalities have been witnessed in 69 species (39.65 %) showing different types of irregularities such as cytomixis, interbivalant connections, unoriented bivalents, chromatin stickiness, chromosomal laggards and bridges as well as abnormal microsprogenesis. All these meiotic abnormalities lead to reduced pollen fertility and formation of variable sized pollen grains in most of these species.     

Cytogeography and phenomenon of cytomixis in Silene vulgaris from cold regions of Northwest Himalayas (India)

Silene vulgaris is an important ethnobotanical species, but so far no thorough meiotic analysis has been performed, despite its wide occurrence in temperate and alpine Himalayas, this prompted us to undertake present study. We investigated original meiotic chromosome number and effect of cytomixis on meiotic course, microsporogenesis and pollen grain size and fertility. The paper also summarizes the previously published chromosome counts in the species and cytogeography of 2x and 4x cytotypes in the Indian Himalayas and elsewhere. Meiocytes preparations were made through standard squashed technique in 1 % acetocarmine. Two ploidy levels have been determined during the cytomorphological surveys, diploid (2n = 2x = 24) and tetraploid (2n = 4x = 48). Most of the presently scored populations were found to be diploid (2n = 2x = 24). Morphologically 2x and 4x individuals were indistinguishable from each other. Meiosis was perfectly normal in 4x cytotype. However, some of the 2x plants showed the phenomenon of cytomixis and associated meiotic abnormalities. Consequent to cytomixis, hypo-, hyperploid and enucleated pollen mother cells (PMCs) were resulted. Such PMCs combined with other meiotic abnormalities yielded sterile and variable sized pollen grains. On the basis of overall information, it is clear that 2x cytotype is the most widely distributed cytotype in the Indian Himalayas as well as elsewhere. On the other hand, the 4x cytotype seems to be less frequently present in the Indian Himalayas and outside of India.     

Cytology of the genus Artemisia (Anthemidae,Asteraceae) in the Western Himalayas

The present study revealed the varied frequency of natural chromosomal abnormalities in 13 populations pertaining to 9 species of the genus Artemisia L. from different localities of Himachal Pradesh (Western Himalaya). Intraspecific chromosome variability has been reported for the first time on worldwide basis in Artemisia vestita (2n = 2x = 36) and from India in A. macrocephala (2n = 2x = 18) and A. scoparia (2n = 2x = 36). Besides, B-chromosomes have been reported here for the first time in A. nilagirica and A. roxburghiana. Most of the populations show anomalous meiotic behaviour resulting in cytomixis, chromosomal stickiness, unoriented bivalents, formation of laggards and bridges which leads to abnormal microsporogenesis, and production of heterogeneous-sized fertile pollen grains along with reduced pollen fertility.     

Cytomorphological diversity in some selected members of Poaceae from Parvati Valley in Kullu district of Himachal Pradesh,India

The present work includes detailed male meiotic studies on 46 species of grasses falling into 59 accessions from different localities of Parvati Valley in Kullu district of Himachal Pradesh in the altitudinal range of 1,100 to 2,750 m. All the species have been studied cytologically for the first time from the study area. The meiotic chromosome count of n = 14 for Calamagrostis emodensis is the first ever chromosome report. Three species, namely Agrostis alba (n = 21), Avena byzantina (n = 21) and Bromus inermis (n = 14) have been studied cytologically for the first time from India. New intraspecific diploid/polyploid cytotypes have been reported for Arthraxon serrulatus (2n = 4x = 32), Iseilema laxum (2n = 12x = 60), Digitaria albudens (2n = 8x = 72), Festuca kashmiriana (2n = 2x = 14) and Stipa orientalis (2n = 2x = 20). The existence of variable number of B-chromosomes (2n = 60 + 0-5B) has been reported for the first time in the 12x cytotype of Iseilema laxum. Secondary associations of chromosomes in the tetraploid cytotype of Cymbopogon martini (n = 20) indicated its secondary polyploid nature. As many as 18 species showed various meiotic anomalies such as the phenomenon of cytomixis involving inter PMC migration of chromatin material, chromatin stickiness, interbivalent connections, abnormal spindle activity, presence of bridges and laggards during anaphases and telophases and abnormal sporads. These meiotic abnormalities consequently yielded sterile and heterogeneous-sized fertile pollen grains. The polyploidy and aneuploidy have played an active role in the evolution of grasses.     

Karyology of some Convolvulaceae species occurring in NE Brazil inselbergs

Eighteen species belonging to family Convolvulaceae occurring in northeastern Brazil were analyzed to identify the karyotypic variability among rupicolous and non-rupicolous species. The count of 2n = 56 for Evolvulus sp., is the first report of polyploidy for the genus. The similarities among the karyotypes of species of Ipomoea, Merremia, and Operculina suggest that x = 15 is the basic secondary number for these genera, while x = 13 has been observed in Evolvulus. The genus Jacquemontia, with 2n = 18 is karyologically distinct from the other genera of the family. Intraspecific numerical chromosomal variations were not detected, nor were any karyological variations related to the rocky habitat characteristic of inselbergs. The occurrence of other plant groups with polyploid forms linked to this type of habitat suggests that the family Convolvulaceae is karyologically stable. We discuss variations in chromosome numbers, base numbers, and their implications in the evolution of the principal groups within the Convolvulaceae.     

Cytological evaluation of Apiaceae Lindl. from Western Himalayas

The present paper deals with cytological studies on 31 populations covering 17 species belonging to 10 genera of Apiaceae from Western Himalayas. The chromosome numbers in the two species as Chaerophyllum capnoides (n = 11) and Heracleum brunonis (n = 11), along with additional cytotypes for Pimpinella acuminata (n = 9) and Sium latijugum (n = 12) have been reported for the first time on world-wide basis. The genus Pleurospermum, although cytologically worked out earlier from outside India, its species densiflorum (n = 11) makes first representation of the genus from India. Besides, the chromosome number in Chaerophyllum aromaticum (n = 11) have been worked out for the first time from India. The course of meiosis varies from normal to abnormal in different populations of Chaerophyllum villosum, Pimpinella achilleifolia and Sium latijugum while abnormal meiotic course has been observed in all the studied populations of Chaerophyllum acuminatum, C. aromaticum, C. capnoides, Pimpinella acuminata, P. diversifolia, Pleurospermum densiflorum and Vicatia coniifolia. Such taxa are marked with meiotic abnormalities in the form of cytomixis, chromatin stickiness, formation of laggards and bridges resulting into abnormal microsporogenesis. The occurrence of structural heterozygosity has been recorded in the Chaerophyllum acuminatum and C. aromaticum. The effect of these abnormalities is clearly seen on the pollen size and fertility.     

Cytology of five species of subfamily Papaveroideae from the Western Himalayas

During the present course, population-based meiotic studies were carried out on five species of subfamily Papaveroideae from selected localities of Kashmir and Himachal Pradesh in the Western Himalayas (India). Varied intraspecific chromosome counts were reported for the first time in Argemone mexicana and Meconopsis latifolia, both existing on 2n?=?2x?=?14. The x?=?7, confirmed for the first time from the newly found diploid cytotype, is suggested to be the primary chromosomal basic number for the Meconopsis. Furthermore, meiotic course was noted to be normal in Argemone ochroleuca, it varied from normal to abnormal in the populations of A. mexicana and Papaver dubium whereas it was invariably found to be abnormal in all the populations of Meconopsis aculeata and M. latifolia. These anomalous taxa were marked with meiotic abnormalities in the form of cytomixis, chromosomal stickiness, unoriented bivalents, formation of laggards and bridges resulting in abnormal microsporogenesis, and production of heterogeneous-sized fertile pollen grains along with reduced pollen fertility.     

Cytology of SW Asian Chenopodiaceae: new data from Iran and a review of previous records and correlations with life forms and C<Subscript>4</Subscript> photosynthesis

The mitotic chromosome numbers of 35 species belonging to 25 genera from East Azerbaijan Province of Iran and meiotic numbers of five species of Salicornia from different parts of Iran of family Chenopodiaceae are reported. Some of them are first reports and some are first counts from Iran. Based on a review of previously published reports, 145 species and 46 genera occurring in SW Asia have been cytologically studied either based on populations within or surrounding regions. The nomenclature and generic position of all these species are updated based on recent phylogenetic and taxonomic studies. The polyploidy percentage of 26.2 % is beyond the average known in flowering plants, which is surprising for dominant plants of saline and desert ecosystems. The polyploidy of annual plants is only 16 % and that of perennials 19 %, respectively. It was found that C₄ plants represent lower polyploidy levels than C₃ plants. This is correlated by the fact that large number of annuals in the area is C₄ and secondly, polyploidy may constrain niche advantageous in C₄ plants. However, presence of different cytotypes in the widespread species is advantageous as they can occupy different niches. The basic chromosome numbers in chenopods is x = 9 with few derived exceptions in Spinacia (x = 6), Camphorosma (x = 6) and some species of Petrosimonia (x = 8).     

Meiotic studies in some selected members of Gamopetalae from Kashmir Himalaya

The present study is part of our research project on cytomorphology of gamopetalous flora of Kashmir Himalaya, a zone with rich biodiversity. Out of 134 species of Gamopetalae meiotically investigated, chromosome numbers for 30 accessions belonging to 17 species and six families are new or varied reports. Euphrasia paucifolia (n = 22), Lactuca decipiens (n = 8), Saussurea albescens (n = 17), Saussurea roylei (n = 16), Saussurea taraxacifolia (n = 16) and Veronica deltigera (n = 8) are first cytological reports for these species. Anaphalis nepalensis (n = 28), Codonopsis rotundifolia (n = 16) and Hieracium vulgatum (n = 27) are new euploid chromosome reports for these species suggesting potential speciation through chromosomal evolution. Besides, Androsace mucronifolia (n = 10), A. sempervivoides (n = 10), Cicerbita lessertiana (n = 8), Dracocephalum nutans (n = 5), Erigeron patentisquama (n = 9), Galium pauciflorum (n = 11), Onopordum acanthium (n = 17) and Xanthium spinosum (n = 8) are the first chromosome reports to Indian accessions of the species. Out of the 17 species, 9 species (52.9 %) viz. A. nepalensis, C. lessertiana, C. rotundifolia, D. nutans, E. patentisquama, Euphrasia paucifolia, L. decipiens, O. acanthium and V. deltigera show abnormal meiosis/microsporogenesis of one or other type, thereby leading to pollen anomalies.     

Chromosome numbers,characterization of chromosomal pairing during meiosis,origin and natural propagation in polyploid cytotypes (4x, 5x and 6x) of Agrimonia eupatoria L. (Rosaceae) in northwest Himalayas (India)

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.     

Male meiosis,morphometric analysis and natural propagation in the 2× and 3× cytotypes of Tordyliopsis brunonis (Apiaceae) from northwest Himalayas (India)

Tordyliopsis brunonis (Apiaceae) is cytologically investigated here for the first time from India. The chromosome count of 2n = 33, ascertained here, represents a new intraspecific triploid cytotype in the species, supplementing the earlier report of a diploid cytotype with 2n = 22 from Nepal Himalayas. The diploid chromosome count (n = 11) has also been found in some of the presently investigated individuals which showed perfectly normal meiosis with 100 % pollen fertility and normal seed set. However, the individuals with triploid chromosome count showed irregular meiotic behaviour and abnormal microsporogenesis resulting in high pollen sterility (56.26 %) and no seed set. The irregular meiotic behaviour in the triploid individuals is attributed to the occurrence of variable number of univalents (1–7) at diakinesis and metaphase-I. In the subsequent meiotic stages, these univalents lagged at anaphases and constituted micronuclei in sporads. The triploid plants were also observed for natural propagation and it was noticed that no seeds were set. These plants were noticed to propagate vegetatively by rootstocks. Chromosomal pairing in triploid cytotype is typical of an allopolyploid. Based on the characterization of chromosomal pairing during meiosis, we assumed that the triploid individuals are probably alloploid in nature. Hypotheses concerning the possible origin of allotriploid in T. brunonis are also discussed.     

Centromeric and non-centromeric satellite DNA organisation differs in holocentric <Emphasis Type="Italic">Rhynchospora</Emphasis> species

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.     

Cytological studies of Brassicaceae Burn. (Cruciferae Juss.) from Western Himalayas

Cytological studies have been carried out on 12 species of Brassicaceae Burn. on population basis from different geographical areas of Kashmir and Himachal Pradesh in the Western Himalayas. Variable chromosome reports for Barbaraea intermedia (n = 16), Cardamine loxostemonoides (n = 8), Nasturtium officinale (n = 8), Sisymbrium orientale (n = 14) on world-wide basis have been added to the previous reports of these species. The chromosome numbers in seven species as Barbaraea intermedia (n = 8), B. vulgaris (n = 8), Capsella bursa-pastoris (n = 8), Descuriania Sophia (n = 10), Rorippa islandica (n = 8), Sisymbrium strictum (n = 7) and Thlaspi alpestre (n = 7) have been worked out for the first time from India. The meiotic course in the populations of seven species such as Barbaraea intermedia, Capsella bursa-pastoris, Coronopus didymus, Descuriania sophia, Nasturtium officinale, Sisymbrium orientale and S. strictum varies from normal to abnormal while all the populations of two species Barbaraea vulgaris and Sisymbrium irio show abnormal meiotic course. Meiotic abnormalities are in the form of cytomixis, chromosomal stickiness, unoriented bivalents, inter-bivalent connections, formation of laggards and bridges, all resulting into abnormal microsporogenesis. Heterogenous sized fertile pollen grains and reduced reproductive potentialities have invariably been observed in all the meiotically abnormal populations. However, the meiotic course in all the populations of Cardamine loxostemonoides, Rorippa islandica and Thalspi alpestre is found to be normal with high pollen fertility.     

Impaired male meiosis, morphology and distribution pattern of different cytotypes of Bupleurum lanceolatum Wall. (Apiaceae) from the Western Himalayas

Detailed male meiosis, critical morphological observations and distribution pattern of diploid as well as tetraploid cytotypes of the Western Himalayan species, Bupleurum lanceolatum have been evaluated at present. A diploid (n = 8) cytotype is reported from Kashmir, whereas, both diploid (n = 8) and tetraploid (n = 16) cytotypes are available from two districts Kangra and Sirmaur of Himachal Pradesh. Out of these, the tetraploid cytotype makes new addition for the species on a worldwide basis. As per behavior, a tetraploid cytotype is characterized by abnormal meiosis leading to high pollen sterility and size variation of the pollen grains. Morphologically, tetraploids are noted to be luxuriant in comparison to the diploids.     

Karyological knowledge of the Italian vascular flora as inferred by the analysis of “Chrobase.it”

Abstract

Chromosome number knowledge of the Italian vascular flora is stored in the online database Chrobase.it, which includes 6723 records, referable to 3428 taxa, 2799 accepted species and subspecies (about 35% of the national flora), and 3410 different chromosome countings (cytotypes). Appropriate queries to Chrobase.it allowed us to calculate mean, modal and median chromosome numbers for the Italian vascular flora, for geographical subgroups (islands, south, centre, north) and for selected orders, families and genera. Chromosome number data were available for 41 out of 55 orders (74%) and 107 out of 428 families (67%), represented by 664 out of 1297 genera (51%). The most studied administrative regions are Sicily (844 taxa), Tuscany (592 taxa), and Sardinia (390 taxa), while the most studied families are Asteraceae (465 taxa), Fabaceae (266 taxa), Brassicaceae (158 taxa), and Poaceae (144 taxa). Chromosome numbers range from 2n = 6, occurring in several species of Hypochaeris (Asteraceae), to 2n = 240, occurring in Ophioglossum (Ophioglossaceae), Dryopteris (Dryopteridaceae) and Arenaria (Caryophyllaceae) (mode is 2n = 18, and median is 2n = 24). Chromosome number variability was analyzed by frequencies (linear plots) and ANOVA, resulting in significant differences among geographical groups (mean chromosome number increasing from islands-south to centre-north) and selected taxa. B-chromosomes occur in 5.3% of data (148 taxa) and their number is not significantly different among geographical areas, while they occur only in 14 orders, 17 families, and 56 genera. The number of B-chromosomes ranges from 1 to 13 (mode = 1, median = 2).     

Cytogenetics, Geographical Distribution, Pollen Stainability and Fecundity of Santolina impressa (Asteraceae: Anthemideae)

Santolina impressa (2n = 2x = 18) is an endemic species of Portugal, with restricted geographical distribution. The present study aimed to explore its chromosomal variation in respect to chromosome morphology, meiotic behaviour, and effects on pollen stainability and fecundity. Its karyotype formula was found to be either 12m + 2m^sat + 2sm^sat + 2st (75% of the individuals) or 12m + 2m^sat + 3sm + 1sm^sat (25% of the individuals). Univalents were observed in 29.21% of the meiocytes. Chromosome fragments due to breakage in the chromosome arm were observed in 10 meiocytes only (11.23% of the meiocytes). Chains and rings of trivalents were observed in 14.60% of the meiocytes (one trivalent per meiocyte was observed). Chains and rings of quadrivalents were observed in 21.34% and 11.23% of the meiocytes, respectively, with a range of 0–1 per cell. Nine plants (40.90% of the total) with 2n = 2x = 18 + 2B showed a quadrivalent configuration in diakinesis. Twenty abnormal anaphases with delayed disjunction of the four non-homologous and the two homologous chromosomes were observed. Simple chromosome bridges without fragments and interchromosomal adhesions were observed in 35.95% of the anaphases analyzed. B chromosomes showed bivalent association in diakinesis and their segregation at anaphase I was normal. Pollen was found to be fertile (mean ± s.d. = 89.57 ± 47.14%); the effect of univalent frequency and frequency of abnormal anaphase I on pollen stainability was strong and statistically significant.     

Diverse chromosome complements in the functional gametes of interspecific hybrids of MT- and A-karyotype Lycoris spp.

The karyotype and numeric changes in chromosomes among taxa of Lycoris (spider lilies) have been attributed to whole-arm rearrangements; however, the history of karyotype evolution of Lycoris is still ambiguous. In the natural habitat, one-third of Lycoris taxa are interspecific hybrids that are mainly sterile and extremely diverse in morphologies. Lycoris are geophytes with the reproductive stage initiated inside the bulbs during the storage period, which brings some inconveniences in collecting meiotic materials for studying chromosome pairing. The partial fertility of an artificial F1 interspecific hybrid between L. aurea (2n = 14) and L. radiata (2n = 22) provides an alternative option for tracing the meiotic process in F1 hybrids. The chromosome compositions of those functional gametes generated by the F1 hybrid could be recovered according to the chromosome complements of backcross progenies. We perform genomic in situ hybridization (GISH) analysis on somatic chromosomes of 34 BC1 plants (2n = 14–22) to reveal chromosomal divergences in number and composition of those functional gametes. GISH results also indicated a high homology between the MT- and A-genomes of Lycoris, reflecting on the partial fertility and frequently homoeologous recombination at meiosis of the F1 interspecific hybrids. The diverse chromosome complements and recombinant patterns presented in these functional gametes suggested that interspecific hybridization is an important force in driving diversification among Lycoris species. We suggest that the MT-karyotype genome may be the ancestral type in Lycoris, and some other chromosomal rearrangements in addition to centromeric fission may have played roles in the karyotype evolution of Lycoris.     

Meiotic behavior and pollen morphology variation in Centaurium pulchellum (Gentianaceae)

Centaurium pulchellum is an annual herb native to Europe, but introduced in South America, where it is widely used in the preparation of digestive infusions and bitter drinks. In this species, a wide variation in the aperture pattern of pollen grains was reported and has been attributed to environmental factors or irregularities at meiosis. For this reason, cytological and palynological studies have been undertaken on two different populations. The pollen grain analysis showed that some types are more frequent within each population, but the most common forms were the typical 3-colporate and 4-colporate. The cytological analysis revealed that the analyzed populations of C. pulchellum have chromosome number 2n = 36. The presence of tetravalents at meiosis strongly suggests that these populations are autotetraploid based on x = 9. The meiotic behavior showed a significant percentage of irregularities in different phases: off-plate bivalents, precocious segregation, laggard chromosomes, bridges, and cytomixis. However these irregularities are not related to the variation in the aperture pattern of pollen grains. The heteromorphism in the pollen grains observed in C. pulchellum could be a normal condition to which the species is well adapted.     

Cytogenetic variations in eight species of Saussurea DC. (Asteraceae,Cardueae) from Northwest Himalaya

The genus Saussurea comprises many species with highly medicinal, religious or other economical values. The chromosome number in the genus ranges from 2n = 24 to 108, based on x = 12, 13, 16, or 17, but the primary base number is still not clear. The present meiotic study cover 8 species (14 populations) of Saussurea from the Northwest Himalayas, and add new or varied cytotypes, as an attempt to solve the enigmatic cytogenetic variations in the genus. The chromosome numbers in Saussurea auriculata (n = 16) is new to the world, while S. costus (n = 17), S. jacea (n = 17) and S. roylei (n = 17) reveal the varied cytotypes at world level. Besides, S. taraxicifolia (n = 16) is a first ever report for Indian populations. The meiotic studies on different populations reveal a substantial amount of meiotic abnormalities in the form of chromosome stickiness, un-oriented bivalents, cytomixis, laggards, etc. leading to the meiocytes with less (aneuploidy) or more (polyploidy) chromosome numbers. These abnormalities may produce unreduced pollen grains and adversely affect pollen viability. The high number of these meiotic abnormalities may be responsible for the chromosome number variation in the genus.