The cytogenetic effects of sodium salicylate were investigated in the root meristem cells of Allium sativum L. Young roots were treated with 0%, 0.05%, 0.1%, 0.25%, 0.5%, 0.75% and 1% aqueous solutions of sodium salicylate for 2, 4, 6 and 8 h periods. Aberrations and dividing cells were determined from the root-tip squashes after a 24h recovery period. Sodium salicylate induced a significant increase in nuclear and chromosomal aberrations. This increase was dependent on both the treatment duration and the concentration of sodium salicylate. The observed aberrations consisted of micronuclei and fragments, nuclear degeneration, chromosome breakage, stickiness of chromosomes, spindle abnormalities, binucleate and polyploid cells. Sodium salicylate was also found to act as a mitodepressant.
The cytogenetic effect of fumigation of Vicia faba plants, with different concentrations of SO2 (5-150ppm) for five hours and 5 ppm SO2 for one, two and four successive days, has been investigated in the, PMCs, tetrads and PGs. Fumigation with 5ppm SO2 for a period of 5 hrs affected the induction of a highly significant percentage of abnormal PMCs/plant. Such effect increased proportionally as the concentration of the gas or the time of fumigation of the plants with SO2 was increased. Sulphur dioxide was effective in inducing abnormalities in the different meiotic stages, but the highest percentage of abnormalities was observed in the anaphase stages. The common types of irregularities observed in the PMCs were: stickiness, lagging and disturbance of the chromosomes, sticky bridges, fragments, bridges with fragments and multipolar ana- and telophases. PMCs with more than one type of abnormalities were frequenctly observed. More than four spores were the dominant type of abnormalities observed in the quartet stage. A statistically significant percentage of nonviable PGs was observed in addition to the small and deformed PGs. Taking chromosome fragmentation as the criterion for mutgenic potential, SO2 has been found to be mutagenic, even after 5ppm fumigation for a period of 5 hrs.
Meiotic studies in five species alongwith their different races/morphotypes of “Sanctum group” of Ocimum were made from pollen mother cells. The investigated taxa include one tetraploid (2n=4x=32), two pentaploids (2n=5x=40), one hexaploid (2n=6x=48) and one octoploid (with 2n=8x=64) species with basic chromosome number as x=8. The chromosomes in all the species were multiple of x=8 chromosomes. Meiosis was normal but for forming few loose bivalents anf few nuivalents. Anaphase segregation was regular with perfect fertility rate. The mean chiasma frequency per PMC and per bivalent has been studied. It was suggested that lack of multivalents formations in these polyploid species was due to short size of chromosomes having low chiasma frequency, established nature of polyploids and also other genic factors. Two base numbers x=8, 12 are suggestive for the genus Ocimum as a whole i.e. x=8 for “Sanctum group” and x=12 for “Basilicum group”.
By analysing chromosome preparation from 42 Gobius niger jozo specimens from the Gulf of Palermo (Sicily), four different karyotypes were observed: A (2n=52; NF=60), B (2n=51; NF=60), C (2n=50; NF=60) and D (2n=49; NF=60). A chromosome polymorphism due to Robertsonian fusion is present in this species.
A cold shock treatment (16°C) on fertilized eggs of Marsilea vestita induces important ultrastructural alterations. The transfer of eggs from 16°C to 24°C allowed all organelles, plastids, mitochondria, endomembranes and ribosomes to recover a normal organization. However, the return to optimal conditions (24°C) induces the formation of nuclear bodies and the individualization of bundles of microfilaments near the nucleolus. Comparison of our obtained results and investigations concerning other materials indicates a great sensitivity to temperature of Marsilea eggs which rapidly react to weak variations.
During the present studies, of the three lithium compounds tested, lithium carbonate has been found to be most effective in causing chromosome damage. The other two compounds of lithium viz. lithium chloride and lithium acetate cause less aberrations. All the three compounds caused slight increase in SCEs too.
All the three salts of nickel viz. nickel chloride, nickel nitrate and nickel sulfate induced micronuclei in the polychromatic erythrocytes of mice. These also caused various types of abnormalities in the head of spermatozoa. The frequency of spermatozoa with abnormal heads was maximum with nickel nitrate.
Karyological investigations accomplished on sixteen local isolates of Phacus revealed the structure and pattern of mitotic division of nuclei to be atypical. The chromosome numbers ranged from n=10 in P. cylindrus to n=226±8 in P. longicauda, representing the widest range of chromosome numbers reported so far for euglenoid flagellates. All the chromosome counts made in this study proved to be new to science. Cases of the existence of cytological races are well-documented. The possible role of chromosomal rearrangements, euploidy and more specifically aneuploidy in speciation of the genus is suggested.
Comprehensive cytomorphic evaluation of C3 generation autotetraploids of Solanum viarum, a steroid bearing species used by industries, led to the detection of aneuploids in the population. These aneuploids included both hypoploids and hyperploids differing from eutetraploids by one or two chromosomes. In morphological characters aneuploids and eutetraploids were more or less similar but differences for berry yield and component characters were evident. Cytological studies revealed severl interesting features that have bearing on the causes underlying lowered fertility in eu-tetraploids, production of new cytotypes and chromosomal stability of eu-tetraploid population. These are discussed in the context of promoting eu-tetraploids as commercial crop varieties and the enhanced role of eu-tetraploidy in genetic amelioration of this South American introduction.
The karyotype of five species of the genus Zephyranthes Herb. was analyzed: Z. aff. mesochloa, 2n=12; Z. aff. stellaris, 2n=20; Zephyranthes sp. (accession 1), 2n=30 and 2n=31; Zephyranthes sp. (accession 3), 2n=40 and Zephyranthes sp. (accession 4), 2n=50. The karyotype found in the five species studied is in general symmetric except for Z. aff. mesochloa. Chromosome pairing at metaphase I of three species was studied. The results showed that Zephyranthes sp. (accession 1) and Zephyranthes sp. (accession 4) are allopolyploid and that a new basic number in the genus might well be x=5. The presence of associations with more than two chromosomes in Zephyranthes sp. (accession 4) suggests that this species is a segmental allopolyploid since the genomes which participated in their origin are homoeologous.
The somatic chromosome numbers (2n) were 48, 40, 44, 44 and 66 respectively in A. mexicana, A. filiculoides, A. pinnata Aftrica, A. pinnata Cuttack, India and A. pinnata (green isolate, Vietnam). The karyotype study revealed that chromosomes were small and asymmetrical. The total chromatin length (TLC) was employed as an index of species delimitation. Basing on absolute length (AL) the chromosomes were grouped into different sets and karyotypic formula was established for each species. Meiotic behaviour of microspore mother cells (SMC) of all species was almost similar except A. pinnata (Vietnam) and A. filiculoides. In all cases microspore mother cells (SMC) exhibited many common features. Usually quarterets of SMC were observed on pressing. Vacuolisation put the cytoplasm more clear during early prophase and gradual granulation brought more stainability in later stages. Marginal orientation of chromatic materials was noticed. Multivalents were observed in A. pinnata (Vietnam). In A. filiculoides, deformed spindle and unequal spore formation were noticed in some of the SMC. In A. pinnata (Vietnam) almost all spores were much smaller in size. A. mexicana, A. pinnata (India), A. filiculoides and A. pinnata (Africa) were considered to be true diploids whereas A. pinnata (green isolate, Vietnam) was a triploid.
Cytomixis, the spontaneous migration of chromatin material between adjacent PMCs was recorded in a sterile plant screened in the population of Sindhur variety of C. annuum. In 36.5% of cells cytomixis was effected through cytolpasmic bridges resulting in PMCs with variable number of chromosomes ranging from 4 to 36. Interestingly here, the phenomenon of cytomixis was associated with medium strong type of desynapsis. It was also observed that cytomixis has some sort of negative effect on desynapsis resulting in increased pairing in the cells involved in cytomixis. The cytogenetic manifestations of cytomixis and desynapsis are described and discussed.
1. If a certain character, visible or invisible, does occur in a cell not uniformly but having a tendency to appear toward a definite orientation, we consider that the cell has polarity in appearance of that character with respect to the polarity axis of that orientation. 2. The cell polarity is a non-specific property, appearing prior to and maintained throughout actual morphogenesis, so that, it would be an initiator and a leading principle of development. In such a sense, it can be called the “logos” of morphogenesis. 3. The cell polarity is considered to be based on an oriented framework system of microtubules supported by microfilaments in the cortical layer of the cell.
A scanning electron microscope comparative study was carried out on root, stem and leaf structures of Ammophila arenaria (L.) Link. and Phragmites australis (Cav.) Trin. ex Steud. These perennial grasses are characteristic of seashore sand dunes and aquatic environments, respectively. The structures of the organs referred to above are similar in both species, nevertheless each exhibits adaptive characters to its habitat. A. arenaria shows some adaptations to the dry conditions of its habitat, mainly in the leaves. Hence the stomata are found in furrows situated on the adaxial surface and protected from the surrounding environment by the leaf rolling up. The presence of broad bands of sclerenchyma in root and stem, and to a less extent in leaves, was observed in this species. In P. australis the presence of aerenchyma in the root and stem was an evident adaptation to its aquatic environment. This tissue permits gas diffusion among the submerged parts of the plant. The rhizomes of this species store considerable amounts of starch which was observed as grains in the parenchymatous cells of the cortex.
Comparative cytomorphological studies between diploid (2n=28) inbred and colchicine induced auto-octoploids of medicinally important solanaceous plant H. muticus were made. In auto-octoploids the increase in most of the morphological characters such as thickness of the main shoot, leaf size, floral parts and size of stomata and pollen grains was accompanied by reduction in plant height and number of branches. The meiotic chromosome behaviour of the auto-octoploid plants was studied in detail. The high percentage of pollen sterility and very poor or no setting of seeds were attributed mainly to the chromosomal irregularities recorded during meiotic division
Mitotic chromosomes from root tips of an inbred CIMAP/MP-41 of H. muticus were analyzed cytologically. The fourteen pairs of chromosomes were numbered from 1 to 14 on the basis of their descending order of length. The average length of metaphase chromosomes was 2.85μ, varying from 2.14μ to 3.88μ. There was only one pair of satellite-chromosomes, the nucleolus being organized by short arm. The arm ratio ratio ranged from 0.26 to 0.91. The six choromosomes had nearly median centromere and the remaining eight had nearly sub-median centromere. All the fourteen chromosomes could be identified on the basis of their total length and arm ratio when arranged in a specific manner. However, there remained a considerable risk of reversal-of-order error.
Histochemical distribution patterns of RNA, DNA, total proteins and insoluble polysaccharides were followed from the embryonal to the flowering stages of the shoot apex in Raphanus sativus Linn. Cells in the tunica and corpus in the plumular apex stained uniformly for all the above metabolites. Staining for RNA and total proteins in the vegetative apices revealed a well marked cytohistological zonation superimposed on tunica-corpus organization. The axial tunica and CMZ in the vegetative apex and the axial mantle and core in the reproductive apices showed lighter stained cells for nuclear as well as cytoplasmic RNA and total proteins. The shoot apex at all the developmental stages stained uniformly densely in all the zones for both DNA and insoluble polysaccharides with deeper stained nuclei and cell walls respectively.
Bovine serum albumin (BSA) is used as an embedding medium to produce pellets of unicellular organisms that can be handled as single blocks during preparation for cytological studies. The microorganisms are suspended in a solution of BSA, concentrated by gentle centrifugation and the BSA pellet gelled with glutaraldehyde. Gelling occurs at room temperature and its consistency can be controlled by changing the concentration or the time of exposure to glutaraldehyde. The part of the gelled block containing cellular material is then sliced into smaller portions that can be subjected to different cytological treatments. These make the correlation of data from different cytological observations more reproducible and less time consuming since it avoids duplication of preparative steps. BSA embedding also minimizes compression and clumping of cellular samples; hence, it minimizes artifacts in the preservation of cellular structure. The technique can be used to handle on a routine basis large number of specimens of microorganims for cytological observations.
Cytological and morphological studies have been made on two morphotypes of Rottboellia exaltata, a “short” and a “tall robust” one, collected from different localities of Kerala State. The “short” morphotype is diploid (2n=20) and the “tall robust” is tetraploid (2n=40). The cytological evidence indicates that the “short” morphotype is one of the putative parents of the tetraploid “tall robust” morphotype. Morphologically the “short” morphotype differs from “tall robust” in several diagnostic characters. Apart form the variations in the size of plant, leaves, etc. these two morphotypes differ considerably in the size of the sessile spikelets and also in the size and shape of the pedicelled spikelets and the morphological features of the glumes of both spikelets. It is suggested that Rottboellia exaltata is an example of compilospecies which has reached the stage of young polyploid complex.
To determine the cytogenetical basis of breeding systems, detailed vegetative and floral features along with the chiasmata/nucleus/bivalent have been investigated in two successful colonising species Lippia nodiflora and L. geminata. These attributes have been compared with those in two non-colonising ornamentals, Verbena hybrida and V. bonariensis. The comparative analysis of data indicates that colonising species possess besides dynamic breeding mechanisms like vegetative, selling and outcrossing, a significantly higher chiasmata/bivalent resulting in high frequency of gene reshuffling. The ornamentals on the other hand have only sexual mode of breeding, mostly outcrossing, and lower chiasmata per bivalent. This differential behaviour between the two groups of species enables the colonisers to thrive in adverse ecological niches under rigorous natural selection whereas the ornamentals thrive only under human care and nurture.
Somatic chromosome numbers were studied from root tips of 18 F1 interspecific hybrids raised from a cross between a male sterile clone of Mentha spicata (2n=72) and a male fertile clone of M.×piperita (2n=120) of the germplasm. The chromosome numbers in the F1 hybrid progeny ranged from 36 to 115. The normally expected chromosome number (2n=96) was found to be the most frequent. Only one hybrid with 2n=36 resembling the female parent (M. spicata, 2n=72) suggested its origin either through female parthenogenesis or normal fertilization followed by selective chromosome elimination. The other hybrid genotypes possessing aneuploid chromosome numbers 2n=110 (13.34%) and 2n=115 (6.67%) possibly arose due to the participation of gametes containing abnormal chromosome numbers produced as a result of misdivision in meiosis of the parental clones.
Lateral roots of Vicia faba L. were grown for one cell cycle in presence of 5'-bromodeoxyuridme (BrdU), followed by another cell cycle in presence of thymidine. Between these treatments root tips were exposed to either quinacrine mustard or to UV-light, both known to induce structural chromosome aberrations of the exchange type and sister chromatid exchanges (SCE). An additional treatment with caffeine during the first cell cycle (pretreatment) led to a reduced number of exchange aberrations, whereas caffeine given during the second cell cycle (posttreatment) increased the frequency of exchange aberrations. SCE frequencies were not affected by caffeine. The effects of caffeine pre- or posttreatment on chromatid exchange aberrations and the relationship between exchange aberrations and sister chromatid exchanges are discussed.
1. The karyotypes and chromosome configurations in the F1-hybrids between Chrysanthemum lavandulaefolium var. sianense from China and Ch. boreale from Japan were investigated. 2. The karyotype of sianense is more primitive than that of boreale, because sianense has more symmetrical karyotype and more satellite chromosome than boreale. Therefore, it is assumed that sianense is a primitive species in genus Chrysanthemum. 3. In spite of the small difference in the karyotypes of both species, the genomes of both species are almost homologous because of the high rate of homomorphic bivalent formation in their F1-hybrids.
Meiotic chromosomal abnormalities observed in lettuce plants grown from aged seeds increased with the decrease in the viability of the seed lot. Univalents, fragments and a few cases of precocious segregation were observed in metaphase I. Abnormalities found at anaphase I and anaphase II included dicentric bridges with or without fragments, acentric fragments and lagging chromosomes and chromatids. The spread of the distribution for pollen and seed sterility increased considerably in some ageing treatments; however, average pollen and seed fertilities were not significantly different from the control.
Detailed karyotypic studies of Leptochloa fusca L. revealed 2n=2x=20 chromosomes. All the chromosomes possess a centromere in nearly sub-median (nsm) and nearly median (nm) region. The chromosomes are very small and structurally similar to rice chromosomes except for minor differences in the number of secondary constrictions and complete absence of sub-terminal chromosomes in L. fusca (kallar grass).
Protoplasts from line Tx4 (Nicotiana tabacum), a p-fluorophenyl alanine (PFP) resistant cell line that has lost the ability to regenerate whole plants, were fused using dextran with leaf protoplasts of DR (N. tabacum), a 2, 4-dichlorophenoxyacetic acid resistant and plant regenerable line that has lost flower initiation ability. Somatic hybrids were selected initially by culture in PFP levels which inhibit the growth of DR and then for plant regeneration. The plants suspected to be somatic hybrids were regenerated from two colonies (H-l, H-2) and formed flower buds within six months, while DR plants never formed even if grafted on normal plants. Callus induced from H-1 and H-2 showed resistance to both PFP and 2. 4-D with the resistance being expressed as semidominant characters. The results indicate drug resistance to PFP and 2, 4-D and morphogenic ability for plant regeneration and flower initiation were restored complementally through somatic hybridization.
Cytogenetical studies were carried out on the artificial F1 hybrids between Colocasia esculenta (2n=28) and C. gigantea (2n=28). Of 15 individuals 14 possessed 2n=28, the diploid level of x=14, while 1 of 15 showed 2n=42, the triploid level. The diploid hybrids contained two chromosome sets, one from each parental species. In spite of the similar morphology of chromosome complements to each other parental species, the PMCs of the diploid hybrids showed an abnormal feature in meiosis; almost all chromosomes formed univalents. This abnormal pairing form resulted in the complete sterility of its pollen grains. The triploid hybrid contained two chromosome sets from C. esculenta and one set from C. gigantea. The PMCs of triploid hybrid showed strikingly different aspects in meiosis from those of diploid hybrids; homologous chromosomes of C. esculenta formed bivalents, while chromosomes of C. gigantea formed univalents. The rate of good pollen grains increased to 21%.
A tertiary trisomic was located in the open-pollinated progeny of a second generation interchange heterozygote obtained in the progeny of a triploid Capsicum annuum for the first time. Phenotypically it was remarkable in exhibiting increased height, shortened internodes, dimorphic leaves. Meiotic studies revealed the chromosome number as 2n=25 and a maximum association was a chain of five chromosomes observed in 29.16% of cells. Meiosis was irregular with unequal separation and formation of laggards, micronuclei and polyads. Pollen fertility was reduced to 48.28%. The types and frequencies of meiotic associations formed, origin of tertiary trisomic from the interchange heterozygote and the resaons for altered morphology were discussed.
Detailed karyomorphology of five garden varieties of Clitoria ternatea (2n=16) namely blue single, blue double, violet single, violet double and white single have been studied. They shared many karyotype features in common. In finer details of karyomorphology, some recognizable differences were noticed among the five varieties such as total chromosome length, total short arm length, TF%, number and distribution of secondary constriction and especially the position of centromere on certain individual chromosomes. In the absence of gross structural chromosomal changes it is suggested that gene mutations or cryptic structural changes of chromosomes have played a role in the evolution of morphologically distinct varieties in the species.