Showing papers in "Cytologia in 1982"
TL;DR: The possible cause of the XX zygote lethality and the eventual relationship between sex chromosomal polymorphism and density cycles in natural populations of A. azarae are discussed and evidence stressing the instability of deleted X chromosomes is presented.
Abstract: Akodon azarae (Rodentia Cricetidae) has a sex chromosome polymorphism which gives rise to XX females and females with a partial or total deletion of one X chromosome. Two hypotheses have been proposed to explain the findings in A. azarae. In the first it is assumed that XX, Xx and XO females are fertile and able to produce X, x and 0 ova to give XX, Xx and XO females after fertilization by a X-bearing sperm. The second hypothesis proposes and extreme mechanism of sex dosage compensation ranging from X-chromosome inactivation, to partial or total X chromosome elimination. These hypotheses are tested by analysing the chromosome complement in the offspring derived from mating pairs of A. azarae of known chromosome constitution.The offspring obtained from XX x XY mating pairs showed: a) a sex ratio of 0.67 females per male, b) an average litter size of 3.8 pups, c) the lack of Xx or XO females. The offspring derived from Xx females had: a) a sex ratio of 1.73 females per male, b) a ratio of 0.64 XX females per each Xx female, c) an average litter size of 4.8 pups. The results obtained do not fit the predictions of the fertilization or the sex dosage compensation hypothesis. However, they can be explained by combining the fertilization hypothesis with a rate of lethality of XX zygotes. The possible cause of the XX zygote lethality and the eventual relationship between sex chromosomal polymorphism and density cycles in natural populations of A. azarae are discussed. Moreover, it is presented evidence stressing the instability of deleted X chromosomes.
60 citations
TL;DR: The main purpose of this paper is to combine old findings together with results from the recent studies on cytoplasm and to discuss the importance of cy toplasm for plant breeding and evolution.
Abstract: The main purpose of this paper is to combine old findings together with results from the recent studies on cytoplasm and to discuss the importance of cytoplasm for plant breeding and evolution. Within a species, the study on cytoplasm can be conducted by observing dif ferences of F1 hybrids between the reciprocal crosses. However, the establishment of nucleus-cytoplasm substitution lines is needed for the detailed analysis for genetic studies on cytoplasm, especially in interspecific hybrids. In animals, e.g. in frogs, the nucleus-cytoplasm substitution can be accomplished by transplanting a paternal nucleus into the egg cell after the nucleus of an unfertilized egg is removed. In plant, it is achieved through a biological procedure, namely by backcrossing. Although I have shown in many occasions the procedure for obtaining the nuc lear substitution and restoration lines between two parental species in higher plants, I would like to illustrate a schematic diagram in Fig. 1. to show how these lines could be obtained. One example in my experiment of wheat and its relatives is as follows;
40 citations
TL;DR: Cytoganetical investigations were carried out in some species of Ocimum and it was found that O. canum Sims and O. americanum Linn, which have long been considered as synonym, are two distinct species.
Abstract: Cytoganetical investigations were carried out in some species of Ocimum. During the course of this investigation it was found that O. canum Sims and O. americanum Linn., which have long been considered as synonym, are two distinct species. The former has 2n=24 or its aneuploid form with 2n=26 chromosomes while the latter has 2n=72 chromosomes. It is suggested that O. americanum arose as a natural hybrid between the diploid O. canum (2n=24) and the tetraploid O. basilicum (2n=48) followed by doubling of chromosomes. An experimental evidence to support this hypothesis is provided by resynthesizing O. americanum from O. canum and O. basilicum. The interrelationship and evolutionary aspects of the species are also discussed.
24 citations
TL;DR: It was concluded that the normal concentrations of both planofix and lihocin are safe to use, however, the use of plan ofix warrants greater care at higher con-centrations.
Abstract: The present investigation was undertaken to study the undesirable effects of hormones viz., planofix and lihocin on yield and yield components of chilli at different dose levels. The first concentration of planofix and the first two concentrations of lihocin has stimulatory effect on germination. However, the survival percent was markedly effected in all the treatments of planofix and lihocin. Both the hormones under study produced meiotic abnormalities and the frequency is markedly high in planofix treated population than in lihocin. Pollen sterility which was observed from 9th to 19th day after spraying was highest in planofix treated population over lihocin treatments. The first concentration of planofix and lihocin significantly increased the yield compared to the control. Whereas the next two concentrations of lihocin has no effect on yield. However in planofix, the yield is reduced in last two concentrations and the reduction is significant at the highest concentration. It was concluded that the normal concentrations of both planofix and lihocin are safe to use. However, the use of planofix warrants greater care at higher con-centrations.
21 citations
TL;DR: Results of detailed observations in maize microsporocytes from plants heterozygous for three different inversions are not readily explained by the first two models but are consistent with the third model.
Abstract: Predictions of associations among bridge and fragment elements (produced by the various crossover classes in cells heterozygous for paracentric inversions) differ for three models for the mechanism of chiasma maintenance until anaphase I. These models are: 1) that structural binding may be installed at the positions of crossover sites; 2) that telomeres may replicate or become effectively double very late (anaphase I); and 3) that generalized and persistent sister chromatid cohesiveness may exist. Results of detailed observations in maize microsporocytes from plants heterozygous for three different inversions are not readily explained by the first two models but are consistent with the third model.
17 citations
TL;DR: The present results have been discussed in relation to similar or contradictory observations of earlier authors on the metaphase I associations in advanced generations of autotetraploids.
Abstract: C10 autotetraploid lines in two grain species of Amaranthus viz A caudatus and A edulis were evaluated for their morphology and meiosis Morphologically the C10 plants in both the species maintained the general gigantism in the determinate parts like leaves, stomata, pollen and seed as observed in C0 and C1 The meiosis was typically autoploid with quadrivalents, trivalents, bivalents and univalents The mean quadrivalent frequency as observed at metaphase I varied from a minimum of 1600 to maximum of 3266 in A caudatus while the respective figures in A edulis were 1400 and 233 The mean quadrivalent frequencies for C0 generation in the two species were 6800±029 and 600±027, respectively These figures represented statistically significant reduction over C0 and C1 data The present results have been discussed in relation to similar or contradictory observations of earlier authors on the metaphase I associations in advanced generations of autotetraploids
16 citations
TL;DR: The B-chromosomes of Calycadenia are variable in size, morphology, and meiotic behavior and have probably had multiple origins, perhaps as abnormal meiotic products in structural heterozygotes produced by hybridizing populations or species or as by-products of aneuploid reduction.
Abstract: Cytological studies of seven taxa in four species of the genus Calycadenia revealed the existence of several types of B-chromosomes. Of special interest is the occurrence of at least three forms of nucleolar-organizing B's in a total of six taxa in three species of the genus. Also of note is the occurrence in one species of an unusual structure less than 1μ in length that is interpreted as a micro-B chromosome. Its morphology is reminiscent of that of a “naked” centromere. The B-chromosomes of Calycadenia are variable in size, morphology, and meiotic behavior. They have probably had multiple origins, perhaps as abnormal meiotic products in structural heterozygotes produced by hybridizing populations or species or as by-products of aneuploid reduction.
16 citations
TL;DR: The structural diversity of interphase chromatin in many distantly related plant species is described and it is suggested that heterochromatin is responsible for non random arrangement of chromatin, somatic association and structural diversityof chromatin arrangement at interphase.
Abstract: The structural diversity of interphase chromatin in many distantly related plant species is described. Heterochromatin, which is visualized by a new Giemsa banding technique remains attached to a specific point on the inner side of nuclear membrane and determines a species specific orientation of chromatin. It is suggested that heterochromatin is responsible for non random arrangement of chromatin, somatic association and structural diversity of chromatin arrangement at interphase.
16 citations
TL;DR: It was evident that chromosomal stickiness was the cause of most of the aberrations observed and the increase in dose of 2, 4, 5-T caused significant increase in the percentages of meiotic cells with chromosomal aberration in Ae.
Abstract: The meiotic effects of 2, 4-D and 2, 4, 5-T on hexaploid wheat T. aestivum L., tetraploid wheat T. durum Desf. and a diploid related species Ae. ligustica L. The two herbicides increased the percentages of abnormal meiotic cells significantly. The kinds of irregularities observed were lagging chromosomes, single and multiple bridges, fragments and asynchoronization in the disjunction of chromosomes during second anaphase. It was evident that chromosomal stickiness was the cause of most of the aberrations observed. The increase in dose of 2, 4, 5-T caused significant increase in the percentages of meiotic cells with chromosomal aberrations in Ae. ligustica L.
15 citations
TL;DR: In a sample of 30 specimens of Akodon sp.
Abstract: In a sample of 30 specimens of Akodon sp. (Rodentia, Cricetidae), diploid numbers of 2n=24 and 2n=25 along with two mosaic cases with 2n=25/26 and 2n=23/24 were found. The inter and intraindividual chromosome variability of 2n=24, 2n=25 and 2n=25/26 was due to the presence of supernumerary chromosomes. The 2n=23/24 mosaic resulted from elimination of the Y chromosome in somatic cells, the gonads showing a normal XY constitution. Heteromorphism of the X chromosome was also observed. G- and C-band patterns of mitotic and meiotic chromosomes are described.
13 citations
TL;DR: A satisfactory fixation and embedding technique for the sclerotium of Sclerotinia tuberosa is suggested, which can be applied to other samples with the same technical problems and should be preferred to a shorter time, as far as topographic research is concerned.
Abstract: Preservation of Fine Structure in the Sclerotium of Sclerotinia tuberosa, a Discomycete Fungus; a Model for Preparing Infiltration Resistant and Heterogeneous SpecimensThe sclerotium of Sclerotinia tuberosa is difficult to prepare for electron microscopy, on account of its resistance to infiltration and its heterogeneity. In this work, several preparative methods have been investigated. The effects of varying composition, concentration and pH of the fixative mixture, fixation time (from 2 to 24 hours), embedding medium have been discussed. This kind of sample re-quires a formaldehyde-glutaraldehyde mixture rather than glutaraldehyde only. The nature of buffer plays an important role in preserving the fine structure. It appears that buffers are to be valued for their capacity to restrict ionic leakage and protein extraction. From this point of view the citrate-phosphate buffer allows the best overall pictures to be obtained. However a long fixation time limits the characteristic effects of the buffer and should be preferred to a shorter time, as far as topographic research is concerned. It is also necessary to increase the post-fixation time in order to obtain a good contrast although this may be less important if the aldehyde fixation is sufficiently long. In conclusion a satisfactory fixation and embedding technique for the sclerotium of Sclerotinia tuberosa is herewith suggested, which can be applied to other samples with the same technical problems.
TL;DR: Male meiosis was studied in 6 diploid, 3 tetraploid and I pentaploid Rosa species and highly irregular meiosis, with 6-7 bivalents and remaining univalents, was observed.
Abstract: Male meiosis was studied in 6 diploid, 3 tetraploid and I pentaploid Rosa species. Chromosome associations at diakinesis and irregularities at anaphase and telophase were scored. Pollen fertility was also determined. The diploids and one tetraploid, R. s. pimpinellifolia showed regular meiosis and high pollen fertility. The tetraploid hybrid species, R. macrantha showed fairly irregular meiosis with only about one third of pollen fertile. Highly irregular meiosis, with 6-7 bivalents and remaining univalents, was observed both in the tetraploid R. glauca and, pentaploid R. canina. Additionally these had a very high frequency of laggards resulting in formation of more than four pollen grains per PMC thereby drastically reducing the pollen fertility.
TL;DR: Roots of stressed seedlings with attached cotyledons exhibited a drop in water potential, solute potential and turgor pressure demonstrating a close relationship between cell cycle responses and the water relations of root cells.
Abstract: Vicia faba seedlings with attached cotyledons were cultured in 20% polyethylene glycol 6000 (PEG). Under this condition the mitotic index and incorporation of thymidine into DNA of root tip cells decreased during the first 8 hours of treatment and remained lower than the control for 40 to 56 hours. After this period of time both parameters increased to near the levels of the control indicating a self-recovery response. Seedlings transferred out of PEG after 24 hours of treatment showed a recovery in mitotic index and incorporation, but not to the control levels. Those transferred after 48 or 72 hours recovered fully. PEG-stressed seedlings lacking cotyledons did not exhibit self-recovery, indicating a possible cotyledon role in this phenomenon. Roots of stressed seedlings with attached cotyledons exhibited a drop in water potential, solute potential and turgor pressure demonstrating a close relationship between cell cycle responses and the water relations of root cells.
TL;DR: Vicia faba L. a classical experimental plant with a pair of marker chromo somes has been a suitable material for cytogenetical investigations from a long back and in this investigation best result was obtained in this media.
Abstract: Vicia faba L. a classical experimental plant with a pair of marker chromo somes has been a suitable material for cytogenetical investigations from a long back. Earlier workers relied on undefined nutrient media for initiation of callus masses which was supplemented with yeast extract and coconut milk (Venkates waren 1962). Grant and Fuller (1968) reported less than 1% success in establish ing culture with this type of media. Mitchell and Gildow (1975) suggested Schenk and Hildebrandt's defined media and in our investigation best result was obtained in this media. Regarding chromosomal behaviour in the tissue grown in vitro a little amount of work has been done. It is well documented that during the culture of many plant species cells with variously altered chromosome complements appeared particularly in culture lines. Plant tissue culture has been done generally with a view to regenerate normal plant from the cultured cells. This regeneration has some relationship with the chromosome behaviour during culture. The stability of chromosome is thus a prerequisite step in the differentiation or regeneration of
TL;DR: Detailed karyomorphology of eight South Indian species of Vernonia falling under two basic series x=10 and x=9 has been studied and data appear to indicate that polyploidy and factors leading to karyotype asymmetry have been operating concomitantly in the species.
Abstract: Detailed karyomorphology of eight South Indian species of Vernonia falling under two basic series x=10 and x=9 has been studied namely, V. anthelmintica (2n=20), V. beddomei (2n=18), V. bourneana (2n=20), V. cinerea (2n=18), V. conyzoides (2n=18), V. divergens (2n=18), V. elaeagnifolia (2n=40) and V. malabarica (2n=18).Karyomorphological data indicate that both the basic series are moderately asymmetrical (2A and 2B). In finer details, x=9 group is seen to possess greater karyotype asymmetry.Karyotype specialization in both the series has been more through shift of centromere position which in the case of x=9 species involves more number of chromosomes.Data on the solitary polyploid species, V. elaeagnifolia appear to indicate that polyploidy and factors leading to karyotype asymmetry have been operating concomitantly in the species.
TL;DR: Addition of a suitable concentration of ATP to the normal medium as well as the half-tone s-e medium was slightly stimulative in recovering mitotic activity of the generative nucleus in pollen tube.
Abstract: Effect of exogenous ATP on the generative nuclear division in pollen tube of Lilium longiflorum has been studied. Culture of pollen tubes was carried out on a coverslip with one out of the three kinds of media; i.e., stigmatic exudate (s-e medium), artificial medium (normal medium), and the 1: 1 mixture of the twos before mentioned (half-tone s-e medium). The artificial medium was supplemented with a graded concentration of ATP, 0.01%, 0.05% and 0.1%, in the final concentration. Pollen tubes have grown to a length of about 1 centimeter seemingly in good health in all media. Pollen tube generative nuclear division carried out satisfactorily in regular fashion in the s-e medium while it progressed very slowly in the normal medium when no ATP was supplemented. But the mitosis was completely inhibited in the half-tone s-e medium. Addition of a suitable concentration of ATP to the normal medium as well as the half-tone s-e medium was slightly stimulative in recovering mitotic activity of the generative nucleus in pollen tube. Exogenous ATP, however, has not played a leading role in chromosome separation.
TL;DR: It is concluded that the gametic numbers of 5 and 6 are derivatives of n=7 and might have played a significant role in speciation in the genus Vicia.
Abstract: Male meiosis investigated in twelve species of Vicia revealed that all the three gametic numbers (n=5, 6, 7) reported so far, in the genus, were present. Majority of them showed regular occurrence of 5, 6, 7 bivalents at diakinesis and metaphase I. The univalents, observed in some species, never exceeded two in number. The chiasma distribution was generally random and their frequency in each bivalent was dependant on the chromosome length. However, in V. hybrida, due to localization of chiasmata at distal ends in 5 out of 6 bivalents, the chiasma number was never more than two per bivalent. Highest recombination index was in V. faba and lowest in V. hybrida and in the former the terminalization occured very late. The three size classes among bivalents in PMC complements of various species and even the position of centromeres in bivalents could be clearly earmarked. The species differed markedly in overall chromosome size and on this basis they could be divided into four major groups. The distribution of chromosomes at anaphase I was normal in all the species. It is concluded that the gametic numbers of 5 and 6 are derivatives of n=7. The variation in gametic numbers, localization of chiasmata, pericentric inversions, differential chromosome size in various species and gene mutations might have played a significant role in speciation in the genus.
TL;DR: The effects of maleic hydrazide MH, indole-3 acetic acid IAA and colchicine were studied on the mitotic division and induction of chromosomal abnormality in Allium cepa root tips and inhibition of mitosis was brought about under all treatments.
Abstract: The effects of maleic hydrazide MH, indole-3 acetic acid IAA and colchicine were studied on the mitotic division and induction of chromosomal abnormality in Allium cepa root tips treated with 25, 50 and 75 ppm concentrations for 4, 8 and 12 hour durations. Inhibition of mitosis was brought about under all treatments except IAA which at lower concentration stimulated the division. For the inhibition of mitosis IAA was most effective and MH was least effective. The capacity to produce chromosomal abnormality was evidenced by the presence of chromosome and chromatid breaks, bridge formation, spindle fibre inhibition resulting in the formation of polyploid cells; chromosome erosion, lagging of chromosomes, micronuclei, stickiness and swelling of the nucleus.
TL;DR: Continuous light, with or without aeration, did not eliminate the midday peak of the mitotic index in root tips of diploid and triploid Allium triquetrum, but aeration of the tap water in which the roots were grown increased the mitotics in 2X and 3X roots, indicating that a greater number of meristematic cells were dividing.
Abstract: Continuous light, with or without aeration, did not eliminate the midday peak of the mitotic index in root tips of diploid and triploid Allium triquetrum However, when plants were grown in continuous darkness with aeration, the midday peak of the mitotic index was no longer evident Aeration of the tap water in which the roots were grown increased the mitotic index in both 2X and 3X roots, indicating that a greater number of meristematic cells were dividing Triploid root tips had a higher mitotic index than diploid root tips, partly because of an increase in the length of mitosis
TL;DR: Investigation of the karyotype of male N. lugens revealed the alleged single X chromosome in the male consists of two elements of unequal length which separate reductionally in the first meiotic division and equitably in the second.
Abstract: The karyotype of male N. lugens has previously been reported as 2n=29 (1411+ X) giving an X O, X Y sex determining mechanism. However, this investigation revealed the alleged single X chromosome in the male consists of two elements of unequal length which separate reductionally in the first meiotic division and equa tionally in the second. From this, and by comparison with other X O species it was determined that N. lugens has an X Y sex determining system with a chromosome number of 2n=30(1411+XY) in the male.
TL;DR: The desynaptic plant showed univalents ranging from 0 to 13 at diakinesis and metaphase I, and in triploid plant 36 per cent of the cells showed eight chromosomes separating to one pole at anaphase I.
Abstract: The desynaptic plant showed univalents ranging from 0 to 13 at diakinesis and metaphase I. In triploid plant 36 per cent of the cells showed eight chromosomes separating to one pole at anaphase I. The morphology, cytology and sterility studies were conducted in all the trisomics isolated. All the primary trisomics showed 6II+1III or 7II+1I at diakinesis and metaphase I. The frequency of trivalents was reduced at metaphase I. The trivalent resumed in chain of 3, V-, Y-, frying pan, S-, J- and 4-shape configurations. Based on cytomorphological distinction, the 16 trisomics were grouped in five classes as bushy, awned, slender, dark green and tiny.
TL;DR: The occurrence of distinct bivalents in majority of the taxa studied, indicate that they represent ancient polyploids.
Abstract: The present investigation includes the meiotic study of 15 species belonging to the tribe Hibisceae and Ureneae of the family Malvaceae. Of which meiotic study of 7 species has been done for the first time. The meiosis is regular in most of the taxa. Few irregularities like laggards in anaphase and telophase I and II, irregular distribution at anaphase I and non-congressional bivalents, secondary association of bivalents at metaphase I are noticed in a few species. The occurrence of distinct bivalents in majority of the taxa studied, indicate that they represent ancient polyploids.
TL;DR: The duration of individual stages of meiosis and spermiogenesis in Anabas testudineus (Bloch) was estimated autoradiographically by using H3-TdR by finding that the leptotene, zygotene and pachytene last for less than a day whereas the duration of diplotene, diakinesis and metaphase I is comparatively longer.
Abstract: The duration of individual stages of meiosis and spermiogenesis in Anabas testudineus (Bloch) was estimated autoradiographically by using H3-TdR. The leptotene, zygotene and pachytene last for 0.33±0.08, 0.20 and 1.80±0.10 days respectively whereas the duration of diplotene, diakinesis and metaphase I is comparatively longer and last for about 1.30±0.20 days. The spermiogenesis is completed within 6.60±0.40 days whereas the total duration of meiosis and spermiogenesis is about 10.50 days.
TL;DR: In Bouganwillea phloem tubes characteristic P-plastids have been observed and have confirmed the importance of this plastid as a systematic character of Caryophyllales.
Abstract: The fine structure of plastids in hypsophyll at different stages of development and pigmentation has been followed in two short-days plants: Euphorbia pulcherrima and Bouganwillea.In Euphorbia the young chloroplasts observed in the embryonal green hypsophyll change into plastids of small dimensions when contained in the red expanded hypsophyll. Moreover in the green leaves, where red colour is afterwards superimposing, chloroplasts are undergoing a degenerative process. In Bouganwillea the plastid ultrastructure is changing from a young embryonal feature to a moderately developed state, while in the fully expanded hypsophyll degenerated chloroplasts are present together with a population of plastids characterized by numerous large globules and few residual membranes. The unlike chloroplasts behaviour observed in the two different hypsophylls is discussed keeping in consideration pigment synthesis and hypsophyll derivation.In Bouganwillea phloem tubes characteristic P-plastids have been observed and have confirmed the importance of this plastid as a systematic character of Caryophyllales.