Showing papers in "Cytologia in 1971"

Studies on the Cytology and Phylogeny of South Indian Grasses

Abstract: The cytology of 57 species belonging to 21 genera of the tribe Paniceae (sub-family Panicoideae) is reported in this paper. This includes 20 species which are studied for the first time. The somatic chromosomes of 29 species have been ex-amined from root tip cells and the meiotic divisions of pollen mother cells of 42 species have been studied. The chromosomes of most of the species are small-sized and about 1μ-1.5μ in length. The basic number 9 is found in 45 species and the other basic numbers recorded are 7, 8 and 10. Chromosome numbers in multiples of 8 is encountered in two species viz. Panicum maximum (2n=32) and Urochloa panicoides (n=16). About 77 per cent of the species now studied are polyploids. Intraspecific polyploidy is found in three species viz. Brachiaria ramosa (2n=36 and 72), Setaria verticillata (2n=18 and 54) and Paspalum commersonii (2n=40 and 60). The meiotic chromosome behaviour was regular in most species, but two species of Paspalum, viz. P. conjugatum and P. commersonii showed asynapsis of chromosomes. The three tribes Paniceae, Andropogoneae and Maydeae belonging to the subfamily Panicoideae have been recognised as a natural group in the recent systems of classification of the grasses. Data on chromosome numbers observed from this study and previous reports reveal that these three tribes represent one evolutionary line. It is evident that evolution of species in these tribes is accompanied by alterations in basic chromosome numbers and polyploidy.

Further Studies on Natural Triploidy in Viviparous Onion

Abstract: Triploid A. cepa var. viviparum has been earlier described as a genomic allotriploid with the genomic formula AAB. Studies conducted on the mode of chromosome pairing and used in conjecture with the nature of karyotype, however, favour segmental allotriploid status for the taxon with the genomic formula A A' A''. A. fistulosum and A. cepa are regarded as the progenitors of ‘Pran’ (3X A. cepa var. viviparum). The unreduced pollen grains of the F1 hybrid through backcrossing seem to have resulted in the formation of the triploid cultivar. Like many other polyploids, the latter has taken to vegetative mechanism of propagation to overcome the bottleneck of sterility.

Nuclear Behaviour in the Malpighian Tubes of Triatoma infestans (Reduv., Hemiptera)

Abstract: Nymphal Malpighian tubes of Triatoma infestans Klug have polyploid nuclei, as other insect groups. These nuclei, however, show heterochromatic bodies which have the number of replication steps not always in accordance with the euchromatin ones, in what they are similar to the Diptera. The nuclear volume does not follow the same increase in the DNA content per nucleus.

Cytotaxonomy of the Family Bromeliaceae

Abstract: Detailed karyotype studies have been carried out on 15 different species and varieties belonging to 7 genera of Bromeliaceae, viz. Ananas, Bilbergia, Caraguata, Cryptanthus, Dyckia, Neoregelia and Pitcairnia.Although gross homogeneity in the karyotype among the members of the 7 genera is noticed, yet a critical analysis shows that each species and variety is characterised by the distinctive karyotype of its own, particularly in nature of secondary constriction-so structural alteration of chromosomes has been the prime factor in evolution within the family.Out of the 4 tribes within this family, in Tillandsieae, the prevalent chromosome series is 8 or 16; in Bromelieae it is 9, 18 and 25 and in Pitcairnieae it is 25. It has been suggested that 8 represents the basic set for this family from which other numbers might have been derived. On the basis of past report and present investigations a rearrangement of different tribes is suggested-Tillandsieae with its basic set of 8 should represent primitive whereas Pitcairnieae with a series of 25 forms the present climax of evolution. The intermediate stages are possibly represented by Bromelieae some of which are common to Tillandsieae and others with Pitcairnieae.

Induction of Callus Tissues Initiation from Different Somatic Organs of Rice Plant by Various Concentration of 2.4-dichlorophenoxy acetic acid

Abstract: Callus tissues were induced from different somatic organs of O. sativa variety Taichung No. 65. Specific 2.4-dichlorophenoxy acetic acid (2.4-D) concentration in a medium is necessary for the induction of callus from different organs. The optium 2.4-D concentration for callus induction from different organs are 0.5ppm for roots, 2ppm for scutellum and cotyledonous node, 6ppm for coleoptile and 8ppm for stem nodes and leaf-sheath. All cultures were incubated in darkness at 28°C.Anatomical studies showed that the initiation of callus tissues from leaf-and coleoptile are initiated from the meristematic cells located very closely by the immature vascular bundles. The initiation of callus in nodes seems to be similar to those of adventitious roots which are initiated near to the differentiating vascular tissue or directly from the procambium.

Meiotic Abnormalities Induced by Gamma Rays in Vinca rosea Linn

Abstract: Various meiotic abnormalities were studied in PMC's of plants raised from seeds irradiated with various doses of gamma rays. The timing of onset of meiosis is highly disturbed in these plants. In Prophase chromosomes exhibit stickness and clumping and towards the end of prophase irrespective of the dosage, the cells contain fragments of chromosomes, univalents and disturbed bivalent association resulting in different configurations of chromosomes. The number of fragments and chromosome chain appearing as multivalents become more apparent towards the end of diakinesis. Chromosomes of different configurations including fragments are delayed ins Metaphase orientation and they are seen laying scattered or in groups in cytoplasm. The disturbed formation of spindle and the orientation of chromosomes in groups in metaphase are remarkably high in PMC's. In anaphase formation of micronuclei of different numbers and sizes, lagging chromeomes, fragrpents of chromosomes and chromatids, bridges with or without fragments are also very common. These abnormalities are carried forward and are also very commonly observed during second meiotic division. The frequency of occurrence of fragments is proportional to the dosage of gamma rays and also the presence of multivalents increases with the dose. These abnormalities seem to induce pollen sterility which is proportional to dose of gamma rays. This pollen sterility seems to be the cumulative result of various aberrant meiotic stages as well as physiological and genetic damages induced probably by the breakage of chromosomes through the formation of antimetabolic agents in these cells.

Chromosome Studies in Three Species of Freshwater Decapods (Crustacea)

Abstract: The diploid number of chromosomes of Macrobrachium siwalikensis, Paratelphusa (Barytelphusa) masoniana, and Potamon (Potamon) koolooense is 100, 134, and 80, respectively. All the chromosomes in M. siwalikensis are metacentric, but in the remaining two species the centromere location could not be determined due to their small size.No morphologically distinguishable sex-chromosomes have been observed in any of the species studied.

Autoradiographic evidence of human male germ-cell differentiation in vitro.

Abstract: A method of culture of human male germ-cells is described. Autoradiographic evidence of germ-cell differentiation in vitro till the early spermatid stage is presented.

Induced Polyploidy in Legumes

Abstract: Seeds and seedlings of Glycine max variety Biloxi and C. max variety UPI have been treated with aqueous solution of colchicine. Seedling treatments have been found to yield tetraploid plants in both the varieties.In the tetraploids, deformed, thick and dark green leaves, stunted growth, delayed flowering, changes in size and frequency of stomata and pollen grains and reduced fertility have been observed and discussed with reference to previous observations. More than three leaf-lets have been observed in the tetraploids and the size of the leaf-lets has increased. C1 generation has also been studied.Meiotic studies in the tetraploid revealed different combinations of uni-, bi-, tri- and quadri-valents with tetraploid number of chromosomes. Exact doubling of chromosomes was observed in comparatively few cells. PMCs with complete set of chromosomes involving quadrivalent formation have not been observed. Occurrence of high frequency of bivalents has been discussed. Maximum number of quadrivalents has been found to be six.

Chromosomal Biotypes of Carica papaya Linn

Abstract: Five horticultural forms of Carica papaya growing in India have been studied. Karyotypes of them represent homogeneity. Slight structural difference in chromosomes of different varieties is noticed, which proves the role of structural alteration of chromosomes on the evolution of the forms. No heteromorphic pair, or unpaired chromosome or any chromatin body, suggesting chromosomal basis of sex difference in the species, could be recognized.

The Recovery Process of the Tannin Vacuole in the Motor Cell of Mimosa pudica L

Abstract: A crushed (semi-circular) tannin vacuole is observable in the motor cell of the Mimosa main pulvinus immediately after stimulation If the motor cell is then soaked in tap water for 15 to 20 minutes, the tannin vacuole begins to take a spherical shape Before stimulation, using anesthetized material, spherical tannin vacuoles are observableIn the presence of 001 M EDTA, the recovery of the tannin vacuole is accompanied by an increase in volume and surface area But in the presence of CaCl2, the recovery process of the tannin vacuole scarcely is accompanied by changes in its volume and surface area In the medium containing CaCl2 the recovery to a spherical shape is made by 15 to 25 minutes, while in the medium containing KCl it takes 30 to 40 minutes

Cytological Regulation of Recombination in Pennisetum and Brassica

Abstract: The restriction of recombination through chiasma frequency was investigated in Pennisetum and Brassica where outbreeding is controlled by two different genetic mechanisms. Lines with known inbreeding coefficients were utilised for this purpose. Self-compatible and self-incompatible Brassica material subjected to five generations of disruptive selection for flowering was also included.A consistent increase was observed in the mean chiasma frequency per cell of Pennisetum and Brassica inbreds as compared to the outbred populations. The increase was parallel with the degree of inbreeding in Pennisetum. Disruptive selection for flowering increased chiasma frequency in Brassica populations with the exception of late self-incompatible group.The buffering mechanism of chiasma frequency under inbreeding, referred to as cytological homeostasis, was examined from the viewpoint of the genetic diversity of the populations, the past history of selection, the ecological conditions under which the material is grown, the nature of the breeding system and the fitness-flexibility axis. It is concluded that a compromise between fitness and flexibility is arrived essentially by regulation of recombination through cytological homeostasis and the breeding system.

Studies on the Longevity of Pollen Grains of Rice, Oriza sativa L

Abstract: 1. Conspicuous morphological change was observed in rice pollen grains when they were left in the air after shedding.2. Within a few minutes, a lot of vacuoles appeared around each pollen grain. Inclusion of the vacuoles was exuded from inside of pollen grains, but chemical analysis has not been carried out in the present study.3. However, a rapid alteration in the physiological condition might have occurred to result in a decrease of germinability of pollen grains. And in part, this has been proved by TTC test.4. Above described transformation of the pollen grains was characteristically occurred when they were shed sparsely on the slide glass. But when they were scattered densely, there were also observed a few pollen grains which kept the viability for longer time.5. It was concluded that the rice pollen grains rapidly lost their viability by losing inner substances when they were left in the drought condition in the air. Further study on the physiological and metabolic disturbances in the course of losing viability, will throw light on the problem of longevity in rice pollen grains.

Triploidy and Seedlessness in Guava (Psidium guajava L.)

Abstract: The cytological behaviour and morphological characteristics of diploid and triploid forms of guava are presented. Meiosis is regular in the diploids with the formation of 11 bivalents. The triploids in general could be distinguished by their greater vigour, large leaves and thicker petals. Meiosis is characterised by a maximum association of chromosomes as 11 trivalents.The differential development of tissues (ovary wall and placenta) can be attributed to a difference in female sterility. The placenta development is greater in diploids which are fertile or where only partial (genic) female sterility is operative. In case of triploids which are highly seedless, genic sterility is superimposed on chromosomal sterility; the stimulation in placenta development is thereby retarded as fertilisation fails and there appears to result a greaster development of the ovary wall.

Fine Structures of Interphase Nuclei

Abstract: The initiation and replication sites of DNA synthesis in the plasmodial nuclei of Physarum polycephalum were studied with electron microscopic autoradiography. By using both thin sectioning and whole mount techniques, it was shown that the dense chromatin masses in the nucleus consisted of predominantly elementary chromatin-like fibrils, approximately 300 A in diameter while the electron transparent region in the nucleus consisted of predominantly finer fibrils, less than 100 A in diameter. With electron microscopic autoradiography it was found that (1) the initiation sites of DNA synthesis were definitely in the boundary regions between the dense chromatin masses and the electron transparent region, (2) the initiation and replication sites of DNA synthesis were definitely not on the nuclear membrane, (3) within a few minutes, replication sites migrated from the initiation sites to the electron transparent region and (4) in this electron transparent region, almost all of the nuclear DNA was synthesized.

Die Meiosis einer partiell sterilen Mutante von Brassica oleracea var. capitata

Abstract: Die Meiosis einer Mutante von Brassica oleracea var. capitata wurde analysiert. Hierbei wurden folgende Befunde erhalten:1. In der 1. Metaphase treten 0-12 Univalente je PMZ auf; der Mit-telwert lag bei 3, 8. Da im Pachytan normale Paarung aller Homologen zustande kommt, kann die Univalentenbildung nur auf einer Herabsetzung der Chiasmenfrequenz beruhen; die Mutante gehort folglich zur Gruppe der desynaptischen Formen.2. Einige der Univalente werden unmittelbar in die Tochterkerne der 1. Interphase einbezogen. Die ubrigen werden nachtraglich noch in die Aquatorialplatte eingeordnet, ihre Chromatiden wandern an die Pole. Die beiden Tochterkerne setzen sich folglich aus Chromosomen und Chromatiden in unterschiedlichen Zahlenverhaltnissen zusammen. Die fur alle ubrigen desynaptischen Mutanten anderer Species charakteristische Bildung zahlreicher Mikronuklei wird durch diesen Mechanismus vermieden. Als Folge hiervon liegt die Storungsrate auch in den spateren Stadien der Meiosis niedriger und es wird ein relativ hoher Anteil funktionsfahiger Pollen produziert; er lag bei etwa 30%.3. In Testkreuzungen konnte die Funktionsfahigkeit dieser Pollen bestatigt werden, wahrend die Mutante eine auserst geringe Anzahl funktionsfahiger Eizellen bildet. Es kann angenommen werden, das sich das mutierte Gen starker auf die Makrosporogenese auswirkt als auf die Mikrosporogenese.

Chromosome Behaviour at Meiosis in Punica granatum L

Abstract: The haploid chromosome number in forty accessions of pomegranate investigated upon was found to be 9. The most frequent chromosome association was 1IV+7II. The other associations viz., 2IV+5II or 9II were less frequent. One of the quadrivalents was nucleolar. The quadrivalent always disjoined as 2/2. The horticultural type in which most of the anthers become petaloid has the same chromosome number and behaviour as the other varieties studied. There was no deviation between the somatic and the gametic chromosome numbers. The chromosomal variation in pomegranate has been found to be very little and in improvement hybridisation between varieties would be more profitable than induction of polyploidy or mutations.

The Chromomeres of Pre-pachytene Chromosomes

Abstract: The arrangement of the chromomeres in relation to the chromosome axis in pre-pachytene chromosomes was studied with the light microscope in these plants: Vagaria parviflora, Fritillaria lanceolata, the garden tulip Mad. Lefeber and the hybrid lily Formobel. The fine structure of the leptotene chromosomes of some of these was also studied with the electron microscope.Evidence in support of the premise that chromomeres are formed eccentric to the axis of leptotene chromosomes, in order to segregate non-recombinational DNA from a pairing face, was obtained with the light microscope.The uncoiling of condensed parts of chromosomes, seen in pre-meiotic interphases and somatic nuclei of a lily, coincided with the onset of leptotene.Because of the alternation of chromomeres around the axis of the leptotene chromosomes, as a consequence of rotation, their eccentric alignment was difficult to confirm in thin sections with the electron microscope. The dense axial cores and less opaque chromomeral chromatin of leptotene chromosomes showed an equivalent staining behaviour with uranyl/lead ions and ethanolic phosphotungstic acid, thought to be largely specific for basic protein. No evidence was found of a close association of cores, indicative of pre-alignment of homologous chromosomes in pairs.

Chromosomal Association and Meiotic Behaviour of a Triploid Rice (Oryza sativa L.)

Abstract: Chromosomal associations in a triploid indica rice plant (T. 1242) at meiosis were investigated.Majority of metaphase I cells showed chromosomal association of 10III+3II. Precocious disjunction was observed in non-homologous bivalent and moved to opposite poles. The third chromosome of each trivalent separated first and moved irregularly to the poles.Majority of the anaphase I cells recorded 19/17 disjunction followed by 18/18 and 20/16. Fifty percent of the cells showed 1 to 5 laggards at telophase I.Triploid plant exhibited high percent of spikelet sterility and pollen abortion. There seems to be a close relationship between the number of microspores with micronuclei and the pollen sterility; more the micronuclei, greater is the pollen sterility.

A Karyological Study of Two Species of Tortoises from the Amazon Region of Brazil

Abstract: The two morphologically distinct species G. carbonaria and G. denticulata have 52 chromosomes. The same number found in Clemmys japonica and Geoclemys reevesii. This number is, however, about double that of the number described in species of genus Podocnemis of the Amazon Region of Brazil. The two species show marked morphological similarities in their chromosomes but the 12th pair is dissimilar, being metacentric in G. carbonaria and acrocentric in G. denticulata.

Cytogenetics of Some Species of Cornus

Abstract: Distinct karyotypic differences between species of Cornus were not detected during a study of mitosis in root tip cells. C. Nuttalli was found to have 2n=22. Several interesting cytological abnormalities during microsporogenesis were evident in five species. A B chromosome was observed in several cells of C. rugosa during first division but not in second division. Globules persisted in some diakinesis cells of most Cornus species and could often be confused with chromosomes. Weak asynapsis was evident in several species. C. altornifolia, C. rugosa and C. stolonifera exhibited polyspory at the quartet stage. The result of these anomalies appears to be the generation of variability within the genus.

Nucleolar Segregation by Cold, 2-4 dinitrophenol or Anoxia in Plant Cells

Abstract: Evidence is adduced for the fact that cold, anoxia or treatment with 2-4 dinitrophenol induced nucleolar segregation in root-tips of Allium cepa. This is the result of redistribution of the argyrophilic and basophilic components of the nucleolus, generally intermingled, into two clearly separate regions. The central region, appearing as highly argyrophilic, corresponds to the “pars fibrosa”, while the peripheral region, which is basophilic in character, consists of the “pars granulosa”. This morphological change in the nucleolus is exactly like the segregation that is induced in root-tip cells through the inhibition of RNA synthesis and the natural segregation observed in the prophase nucleoli of meiocytes from Allium cepa.

Colchicine and Caffeine in the Estimate of Cell Flow and Cycle Time in Allium Roots

Abstract: The meristematic cell flow or percentage of cells formed per unit of time is constant under standard experimental conditions. In this paper, the cell flow is measured directly under the action of the colchicine, by observing the cell increase at metaphase, and with the caffeine by observing the production and increase of binucleate cells in successive units of time.The analysis of different concentrations and periods of treatment has shown the 2hr treatment of 0.05% colchicine and the 4hr treatment of 0.1% caffeine as the more effective in order to measure the cellular increase.Both drugs have a depressive effect upon the division cycle as a whole, in a uniform and homogeneous fashion. Colchicine slows down the division cycle in a 50% and caffeine in a 60% of the normal cell flow. This depressing effect must be borne in mind in any estimate of the cycle time and mitotic rate by means of these drugs.