The cytological features including chromosome counts and karyotype features have been investigated in 10 species of the genus Plantago from Egypt. A basic number of x=5 was recorded in P. albicans, P. crassifolia, P. cryposides and P. cylindrica, whereas x=6 was recorded in P. arabica, P. lagopus, P. lanceolata, P. major and P. notata. P. ovata is the only species in which x=4 was revaled. The chromosome counts of P. cylindrica, P. arabica and P. notata are reported here for the first time, while polyploid numbers are recorded in P. albicans, P. crassifolia and P. ovata. Polyploidy was not encountered in the species with x=6. The karyotypes of all species were described and compared. Moreover the impact of the cytological features on the taxonomic treatments and the relationships of the studied species have been discussed.
The nuclear DNA content in 14 taxa belonging to 9 species of Plantago from Egypt has been measured using cytophotometric methods. The recorded DNA amounts were related to the karyotype features of the studied species. In general the amount of nuclear DNA/genome is correlated with the basic chromosome number. Species having x=6 i.e. P. lagopus, P. lanceolata, P. major and P. notata contain higher amounts of nuclear DNA/genome when compared with the species having x=5 i.e. P. albicans, P. crassifolia, P. crypsoides and P. cylindrica. Three samples of P. ovata (x=4) were found to contain the least amounts of DNA/genome. It was also found that polyploid taxa contain higher amounts of 4C DNA/nucleus than diploid species. The impact of these results on the taxonomic relationships of the studied species is discussed.
In Theobroma cacao, taproots caps are characterized by a strongly polarized organization with sedimented amyloplasts in the lower part of the cell and nucleus in the upper part. Between the amyloplasts and the nucleus a well developed vacuolar system is found, which seems to be a common feature of statocytes in woody plants. Along longitudinal and transversal walls the endoplasmic reticulum forms elongated cisternae and coiled netlike elements between the amyloplasts and the lower wall. After rotations of 90° or 135° of the root system, the migration of amyloplats is synchronous neither in a same cell nor through the statocytes of a same cap. Migration speeds are similar to those registered in other woody species.
Meiotic studies were conducted in four Citrus sps./vars. of hybrid nature. Regular bivalent formation in Rough lemon, Rangpur lime and Chironja indicated absence of any large structural differences in genomes of these sps./vars. The presence of secondary association of chromosomes at metaphase I in Karna khatta in group of three indicates a hybrid origin of this sp./var. Based on the number of bivalent groups it has been inferred that three is the basic chromosome number in citrus. The pollen sterility in these sps./vars. was genic except for Rangpur lime where it seems to be genic as well as chromosomal.
Meiotic studies were conducted in two Citrus-Poncirus and one Citrus-Fortunella intergeneric hybrids. Regular bivalent formation and equal distribution of chromsomes at different stages of meiosis indicated similarity between the genomes of Citrus-Poncirus and Citrus-Fortunella. Cytomixis and secondary association of bivalents indicated a hybrid and polyploid nature of these genera. The basic chromosome number of Citrus and allied genera was reconfirmed as n=3.
Meiotic studies were carried out on 14 taxa representing 7 genera of the family Loranthaceae. The cytology of 8 taxa is reported for the first time. Heterozygosity for an interchange was observed in E. parasitica. Supernumerary chromosomes were observed in H. elastica and T. cuneatus. The difference in basic chromosome number and size of chromosomes in Elytrantheae and Lorantheae seems to convince the integrity of the two tribes. In contrast to the fixed basic number of x=12 in Elytrantheae and Nuytsieae, the tribe Lorantheae showed an aneuploid series of x=8, 9, 10, 11 and 12. In the tribe Lorantheae the primitive genera showed higher basic numbers compared to the more specialised genera which indicates that dysploid reduction from x=12 to x=8 occurred during evolution.
The present paper analyses the variability of chromosomes in two long term callus lines of Kallstroemia pubescens (G. Don) Dandy and regenerated plantlets. The two callus lines ‘C’ and ‘F’ were distinct in morphology and growth on two different hormonal regimes. Both lines revealed an increase in the frequency of hyperdiploid mitoses with increasing age of the cultures. In long term culture, the friable ‘F’ line, as compared to the compact ‘C’, retained more diploid mitoses. A significant feature was the regular occurrence of binucleate cells in both. The causes of numerical chromosomal instabilities in vitro have been discussed. Root tip cells of the regenerated plants were diploid.
Cytological studies were made on Centroceros clavulatum, a member of the Ceramiales of the red algae, which revealed a consistent chromosome number of 2n=30 with a normal and regular meiosis. It is concluded that this species is a stabilised polyploid form occurring on Visakhapatnam coast derived through processes of hybridization and polyploidization.
Meiosis in a highly sterile triploid clone of Jasminum grandiflorum Linn. was reported. Mean trivalent, bivalent and univalent frequencies were 7.85, 5.28 and 4.90 per cell respectively. Complete trivalent formation was observed in 1.22 per cent PMCs. On the basis of these observations, autotriploid nature of the present clone has been established. Reduction in frequency of trivalents and high frequency of univalents were attributed to small size of chromosomes or to desynaptic forces.
The interphase microtubular arrays of onion (Allium cepa L.) root meristem cells were visualized with indirect immunofluorecsence. Two kinds of cytoplasmic microtubules were distinguished in each interpahse cell: cortical and endoplasmic. The cortical microtubules are arranged in an irregular network in isodiametric cells, ribbons running round the long cell axis in some slightly elongated cells and ribbons or rings perpendicular to the long cell axis in elongated cells. The endoplasmic microtubules form a tridimensional network in the endoplasm. Both populations of microtubules behave as two distinct units during preprophase and they exhibit different sensitivity to the action of colchicine.
Germinating seedlings of Allium cepa L. were exposed to varying intensities of electrical field, for two hours in the morning and its effect on mitosis has been studied. Electric field was found to disturb the spindle organisation so that the chromosomes failed to arrange themselves on the metaphase plate. It also induced chromosomal breaks which resulted in the formation of fragments, bridges, loops, dicentric ring and eroded chromosomes at anaphase. Micronuclei were also observed at telophase.
Karyotype analysis of 11 strains of Pisum sativum L. shows gross uniformity in morphology. Somatic chromosome number, 2n=14, is constant for all the strains. Chromosomes are long to medium in length. Primary constrictions range from median to submedian. Secondary constrictions are present in 1 to 3 pairs of chromosomes. Each strain is characterised by its own karyotype, which may serve as an identifying criterion. Absoute chromosome length does not show marked variation, whereas absolute chromosome volume reveals a wide difference. Meiotic analysis discloses regular seven bivalents with a low frequency of irregularities. Karyotype data have revealed the importance of structural alterations in the evolution of different strains. Meiotic behaviour does not reveal any distinct manifestation of structural hybridity in these strains which has been suggested as due to the attainment of homozygosity for structural alterations through selection.
Mutagenicity of copper sulphate was evaluated in vivo by chromosome aberration, sperm abnormality and micronucleus tests in mice. Dose, route and time influenced significantly the frequency of chromosome aberration, incidence of micronucleus and sperm abnormality. Relative sensitivity of three assays are: sperm abnormality>chromosome aberration>micronuclei formation. The present results revealed the mutagenic property o CuSO4 in mouse in vivo test system.
A critical insight into the meiotic profile and behaviour of Balsaminaceae has been attempted. Fairly high recombination index, incapacity for outbreeding, the patent bivalent symmetry, endemic habit, circumscribed ecological location in marshy niches-all these would appear to stamp out the monotypic Hydrocera as a taxon that has reached evolutionary cul-de-sac. The four varieties of Impatiens balsamina have registered very intimate affiliation as reflected in their meiotic traits. Cytogenetical affinity between Impatiens latifolia and I. leschenaultii with each other is far more intimate than with the rest of the genus. I. clavicornu, among the different species of Impatiens, is unique in its meiotic profile and behaviour and affords a glaring example of the profound impact of karyogenetic factors on the phenotypes.
The seeds of CO.2 and Pusa Ruby, the cultivars of Lycopersicon esculentum Mill., were treated with N-nitroso-N-methyl urea (NMU) of 1 mM, 2 mM, 3 mM, 4 mM and 5 mM concentrations and ethyl methane sulfonate (EMS) of 10 mM, 20 mM, 30 mM, 40 mM and 50 mM concentrations. The cytological effect of mutagens in the immediate generation was studied. A number of meiotic abnormalities were observed. They included stickiness of chromosomes, univalents, multivalents, unoriented chromosomes, bridges, laggards and micronuclei. The frequency of meiotic abnormalities and pollen sterility demonstrated a linear relationship with concentration of the mutagens. Pollen sterility seemed to be the cumulative result of various abnormal meiotic stages as well as physiological and genetic damage.
Extensive analysis of morphological, anatomical and cytological characters was carried out on 14 different species and varieties of Calathea, Maranta and Stromanthe of Marantaceae. The morphological and anatomical features of these species vary between species to species and are correlated with chromosome number. These characters may serve as identifying parameters. Chromosome analysis has indicated the chromosome number to range from 2n=24 to 28 in Calathea, 2n=48 and 52 in Maranta and 2n=44 in only species of Stromanthe. The polyploid forms do not show an exact multiplication of the basic set. Duplication alongwith the minute structural alteration of chromosomes has played a role in speciation of these genera. A conspicuous variation was recorded amongst these species in length and volume of chromosomes. The length and volume did not show any direct correlation with chromosome number and a consistency in difference of these two characters was recorded as well. Differential coiling and uncoiling of the arm and ratios of different chemical components in the chromosome structure, have been suggested as responsible for this difference. The similarities in gross karyotype and morphological characters indicate a close relationship between these genera.
The diploid (2n=14) pachytene karyotype of Pennisetum americanum was established based on total length, arm ratio and length and position of heterochromatic regions of individual chromosomes. Of the seven morphologically distinct primary trisomics, the extra chromosome present in six of them was identified by comparing the pachytene chromosomes involved in the trivalent with respective individual chromosomes.
Distribution of reserve metabolites namely insoluble polysaccharides, total proteins and lipids has been studied in the cotyledons of Cajanus cajan, Vigna mungo and Vigna radiata during seed development. Entire developing period of the embryo is divided into four phases. Maximum synthesis of reserve metabolites occurs in the third phase and most of it is stored in the storage parenchyma region of the cotyledons. At maturity the cotyledons are rich in carbohydrates (stored in the form of starch grains) and proteins (in the form of protein bodies). A small quantity of lipid bodies is also present in the cotyledons. Time, site and formation of these metabolites are discussed.
The karyomorphology and morphometrics of chromosomes in brain cells of fourth-instar N. lugens Biotype 1 nymphs were studied. The following features were noted: mitotic index 67%, normal diploid complement 2n=30; karyotype formula, 28 autosomes, plus XX(_??_) or XY(_??_). Males had symmetrical chromosomes with higher relative mean lengths than the females' asymmetrical chromosomes. Mitotic chromosomes of brain cells possessed diffuse centromeres or were holocentric. During regular mitosis, prophase had the longest duration, followed by telophase. Metaphase and anaphase were short duration stages. At prophase, 8 differentiating forms of nuclei were observed. The karyological changes in the basic diploid number were either increases (agmatoploidy) or decreases (hypoploidy) in chromosome numbers. Hypoploidy was more frequent than agmatoploidy.
Urea, a common fertilizer used to supplement soil with nitrogen, has been found to cause a seven times increase in the incidence of chromosomal abnormalities like breaks, clumping, pulverisation and polyploidy in albino swiss mice fed with a 500 mg dose for 5 days. The breaks were non-random in their distribution-more common in larger chromosomes, and the middle and distal regions of the chromosomes. The agrochemical could act as a mito-inhibitor (by 21.05% decrease) in onion root-tip cells, where fragmentation of chromosomes was found to be the most common among the abnormalities induced (0.06% in control, 0.80% in treated).
The centromere separation patterns in the bone marrow cells of Rattus norvegicus and Cavia porcellus were investigated. In both the species the separation was found to be nonrandom. In R. norvegicus the sequence of centromere separation was: chromosome 1 followed by chromosome numbers 15-21, 2, 3, 5-14 and 4 respectively. In C. porcellus chromosome X was the first one to show centromere separation and it was sequentially followed by chromosome numbers 17-31, 2-16 and 1. The administration of two Herbal Ayurvedic Drugs, Kynotomine and Tefroli, to R. norvegicus did not disrupt the sequential separation but caused significant delayment in the centromere separation.
The effect of treatment of cultured Don Chinese hamster cells with sodium fluoride has been investigated with respect to induction of chromosomal abnormalities. Exposure of Don Chinese hamster cells to sodium fluoride (25μg/ml, 50μg/ml, and 75μg/ml) induced a higher frequency of chromosomal abnormalities as compared to control. The observed abnormalities included were bridges, bridges with fragments, sidearm bridges and tripolar and multipolar anaphases. Bridges and fragments were the most common type of abnormalities observed in all treatments.
Acrylamide monomer has wide variety of applications which lead to its release into soils and water ways. The cytogenetic effects of acrylamide were investigated in roots of Allium cepa. The chemical exerted mitodepressive action on mitosis and induced a number of chromosomal changes and mitotic abnormalities. Chromosomal changes produced comprised of chromosome and chromatid breaks, fragmentation and stickiness in metaphase cells. Anaphase cells showed multipolar arrangement, unequal distribution, chromosomal bridges and micronucleated cells. Some of these effects appeared to be irreversible. The study suggests that continuous exposure to acrylamide may lead to genetic effects in plants and even higher organisms.