Four species of the genus Mystus viz., M. vittatus, M. bleekeri, M. cavasius and M. seenghala of the family Bagridae (Pisces) have been cytologically explored. The various cytological parameters such as chromosome number, morphology, funda-mental arm number (NF) and total complement length (TCL) have been determined in each species. In these species, the diploid chromosome number has been recorded to vary in the range of 2n=56±2. The meiotic studies have also been carried out in those cases where mature male individuals were encountered in the collections. The inter- and intraspecific diversity and the possible mode of karyotypic evolution within the genus Mystus has been discussed.
From diethyl sulphate treated barley cultivar DL 36 (2n=14), one asynaptic and three desynaptic mutants were obtained in M2 generation. Asynaptic mutant (DM 11-10) showed lack of chromosome pairing and invariably formed 14 uni-valents at prophase I and MI. Desynaptic mutants showed varying frequencies of univalents and bivalents at MI, range of univalents being 8-14 (DM 1-15), 4-6 (DM 6-6) and 0-8 (DM 16-7), and mean number of bivalents per cell being 1.3, 4.6 and 5.4 in the respective plants. Abnormalities observed at Al were unequal separation, multipolar separation and lagging of chromosomes. Formation of micro-pollen and presence of micronuclei in spores were often observed. Seed set in asynaptic mutant was 3.5 per cent while in desynaptic mutants it was 6.5 (DM 1-15), 68.0 (DM 6-6) and 66.3 per cent (DM 16-7). When crossed to the mother variety, these mutants showed 3:1 segregation in F2 indicating that they were governed by single recessive genes.
The effect of the pure insecticide dichlorvos has been studied on root-mitosis of Vicia faba plant (var. Giza 2). The roots were treated with 250, 125, 63 and 32 ppm of the insecticide for four hours. Dichiorvos treatments induced cells with chromosome abnormalities, which increased in number as the concentration of the insecticide increased. Disturbed meta- and anaphases where the chromosomes spread irregularly over the cell com-prised the main type of the observed abnormalities. Stickiness of the chromosomes anaphase-bridges, micro- and binucleated interphase cells were also observed. The effects of the insecticides dichlorvos and trichlorfon on root-mitosis of Vicia faba are discussed.
The paper records observations on the impact of genome multiplicity on the profiles of three types of nitrogenous compounds in four varieties of N. tazetta. The results demonstrate that polyploidy causes varied effects. It may or may not alter the biochemical profiles and whenever it does, the spectrum is either widened or narrowed. The same trend is followed even by the quantity of specific com-pounds. The possible explantations of such changes have been discussed.
Calli obtained from root explants of Zea mays exhibited chromosomal ab-normalities like inhibition of cell plate formation, chromosomal breakage, sticki-ness and clumping of chromosomes, asynchronous division, chromosomal grouping, laggards and micronuclei formation. Numerical variation in chromosome numbers including hypo- and hyperdiploid cells was observed. Structural changes have been detected with the aid of chromosome banding, along with the location of those points at which the chromosome breaks.
The cytology of one species each of the four genera Rottboellia, Mnesithea, Manisuris and Hackelochoa has been studied and the basic numbers recorded are 10, 9, 8 and 7 respectively. The chromosomes are large in size and the karyotype is less specialized and predominated by metacentric (m) chromosomes while sub-metacentrics (sm) are very rare and acrocentrics and telocentrics are totally absent. There is a blending of advanced floral morphology with primitive karyotype charac-ters in the sub-tribe Rottboellinae. This sub-tribe shows similarity to members of the Maydeae in cytological characters like the presence of large chromosomes with primitive karyotype characteristics, basic numbers of 5 (or 10), 9 and 8 and the occurrence of species with n=5 in both tribes. So there is enough cytological evidence to suggest the close relationship of these two tribes.
Castor plants (var. 279) were exposed to acute gamma rays (2000, 3000 and 4000 R) at seedling, meiotic, gametic and post-gametic stages. The mean chloro-phyll and morphological mutant frequencies with widest spectra and a substantial increase in phenotypic variability for days to flower, seed yield/plant and harvest-index were observed at gametic stage. The spectrum of chlorophyll mutants at this stage differed significantly from those of other three stages. Certain promising mutants with early maturity, dwarf stature and tetra-locular capsules were also recovered more frequently at gametic stage. Maximum mutagenic effectiveness and efficiency were recorded at the same stage. The data amply indicate that ‘gametic’ stage is the most suitable one for irradiation and recovery of useful mutants.
Intraspecific and interspecific relationship between Solanum melongena cv. Dorli, Round Black and S. surattense was investigated. Chromosome association and pollen sterility were also calculated for the parent and hybrids. The hybrid Dorli×surattense was possible only when the former was female parent. The fruits were obtained when the crosses were attempted between Round Black×Dorli but with sterile seeds. Some of these hybrids did not survive up to the flowering age. Round Black×surattense was unsuccessful in either direction. Cytological studies showed univalents frequently at diakinesis and metaphase I in the hybrid plants but not so in their parents. The univalents were due to the absence of pairing between homologous chromosomes. Laggards varying from 2 to 4 and bridges were observed in the hybrid plants.
Karyotypic studies on 10 species of sedges from North India showed that (i) there is no correlation between the number of chromosomes and haploid chro-matin length, (ii) by and large, the karyotypes are symmetrical, and (iii) in case of Fimbristylis dichotoma there is great variation in karyomorphology of individuals of various populations with the same chromosome numbers n=5 or 10. This brings to light the evolution that is operative at micro level and possibly this explains the variations in phenotypic characters so common in sedges which have the advan-tage of stabilizing of new genotypes through vegetative propagation.
Cytological studies with special reference to karyotaxonomy have been made in 14 taxa. First record of chromosome numbers has been made in 4 species and in the rest of the taxa studied, the present report confirms the earlier observations. The chromosome numbers determined in the present study range from 2n=6 to 2n=44. The karyotype analyses show that each taxa has a distinct karyotype of chromosomes. Even the closely related species of a genus with same chromosome number have distinct karyotype of chromosomes indicating the karyotype alterations of chromosomes playing important role in speciation.
Data on the distribution of binuclaeate and trinucleate pollen grains in 103 species representing 32 genera and 15 tribes of the Rubiaceae from South India are reported. In general, the pollen nuclear number showed remarkable constancy within individual tribes and genera except the tribe Hedyotideae and the genus Oldenlandia. In great bulk of the species the vegetative nucleus underwent degeneration during the course of microspore development. Pollen nuclear number showed recognisable relationship with pollen aperture number, the binucleate species posses-sing 3-aperturate grains and trinucleate ones six or more aperturate grains. The pollen nuclear number also showed an association with growth habit, the trinucle-ate condition being present exclusively in herbaceous genera. These associations appear to be suggestive of a non-random distribution of the two nuclear types in the family. The systematic significance of pollen nuclear number in the family is discussed, supplemented with evidences from chromosomal and palynological data. As regards the delimitation and systematic position of various tribes, Bremekamp's classification is shown to be by and large in agreement with the cytological and palynological data. Affinities of the Rubiaceae with other families are examined in the light of the present data, and it is shown that the Gentianalean affinity is more natural.
Roots of Vicia faba seedlings were treated with different concentrations of thinner and some of its main components (toluene, benzene, n-hexane, n-heptane and ethyl acetate) which induce chromosomal alterations in anaphase cells as sub-chromatid-type aberrations (subchromatid bridges), chromatid aberrations (single bridges and fragments), chromosome aberrations (double fragments and bridges), chromosomes with inactivated centromere, isochromosomes and multipolar ana-phases; as well as micronuclei in interphase cells. In each case total aberration frequencies increased with the concentration of the solvent, except for n-heptane which behaved independently of the concentration. C-mitosis was another effect caused by these components. Due to the fact that the solvents used showed a non-delayed effect in relation to the appearance of aberrations and since their induction was in accordance to the phase of the cycle in which the cells were affected, these components can be considered as S-independent agents. On their action upon cell division, it was observed that all the solvents tested had an inhibitory effect demonstrated by the analysis of the mitotic index, except thinner and ethyl acetate which caused stimulation. It seems that the stimulant effect of the thinner is due to the ethyl acetate component.
In the meristernatic root cells of alfalfa seedlings exposed to -1, 5°C, new spherosomes, 0, 1-0, 4μm in diameter, are observed each one within the terminal end of an endoplasmic reticulum (RE) segment. A two-unit membrane envelope surround these new organelles and the external membrane of their envelope is continuous with the RE. Those new spherosomes are filled with an osmiophilic and electron dense material. This osmiophilic material within the new sphero-somes is insoluble in petroleum ether, a solvent of neutral lipid, and soluble in ethylic ether: ethanol, 2: 1, a solvent of polar lipids.
Karyomorphological studies were carried out in three natural populations (Ss0777, Ss1276 and Ss0478) of Solanum surattense. A somatic chromosome number of 2n=24 was observed in all the three populations establishing that the base number of the species is x=12. Detailed karyotypic studies have revealed the dissimilarities in the length and quality of chromosomes which have been sup-posed to be due to asymmetrical karyotype. The climatic conditions and repat-terning of chromosomes have also been accounted for the diversification of karyo-type within the populations.
The prolamellar bodies (PLBs) in etioplasts of Phaseolus vulgaris were studied using thin sectioning and freeze-fracture electron microscopic methods. Comparison between constructed models and electron micrographs permitted an evaluation of the architecture of PLBs. The electron micrographs of the freeze-fractured planes represented the PLBs as wurzite type structure, in which a connecting center had tubular arms. From the connecting center of 4 arms, two types of structure, wurzite and zinc blend, can be formed. On electron micrographs, PLBs were observed as square, regular hexagonal and distorted hexagonal profiles in most cases. From the section-models of PLBs, the square lattice profiles were shown only by the zinc blend type, and the distorted hexagonal profiles only by wurzite type. But the regular hexagonal profiles were shown with both types. Thus, it is likely that both types of PLBs are in the etioplasts. From the examing of the model of PLBs, if two types of PLBs are formed with same frequency, the number of planes representing the profiles of both types was 4 planes in the square, 5 planes in the regular hexagon, and 3 planes in the distorted hexagon. On the other hand, the emergent frequency of the square, regular hexa-gonal and distorted hexagonal profiles on electron micrographs was estimated as 20.5, 24.5 and 16.3% respectively, which is a ratio of 4:5:3. This ratio was con-sistent with that of the profiles of sectioned PLBs. Thus, the zinc blend type and wurzite type of PLBs should be formed in same frequency in the etioplasts.
The effect of the insecticide “rotenone” has been studied on mitosis in the roots of Vicia faba (V. Giza 1). Two types of treatment were conducted: seed soaking and exposure of the roots. Examination of the roots was done in permanent root-tip squash preparations stained by the Feulgen technique. Three roots were examined from each of the 3 replicates and 2000 cells were scored from each of the 9 roots. Root-treatment for 4 hours with saturated aqueous solution of rotenone in-duced a statistically significant percentage of abnormal cells which increased by improving the solubility of the insecticide by dissolving it in a Tween: water mixture (1: 99). The types of abnormalities induced included: disturbed meta- and ana phases (where, the chromosomes spread irregularly over the cell) in a high per-centage, chromosome stickiness, lagging chromosomes and ana-telophase bridges. Cytomixis was observed in some roots and tetraploid cells were seen in a few roots. The effect of rotenone on root-mitosis simulates that of colchicine in the type of the abnormal meta- and anaphases (with X-shaped chromosomes) and the induction of tetraploid cells. Rotenone, on the other hand, did not affect the mitotic index nor caused accumulation of the metaphases.
Desynapsis, induced by water and temperature stress, was recorded in two varieties of Hemerocallis. Average ‘metaphase I’ association per cell during de-synapsis was 0.76II+20.48 I in ‘Love Song’ and 0.80II+20.39 I in ‘Sleeping Beauty’ whereas during normal meiosis 11 II were invariably observed in the same plants. Equatorial congression in desynaptic meiosis was lacking, but majority of cells at ‘anaphase I’ showed clustering of chromosomes into 2-4 groups. Chromosome decondensation following ‘metaphase I’ was non-synchronous. Second division of meiosis was completely blocked so that the microspores were produced directly from telophase I products.
The freeze fracture method was used to study changes in membrane particles during the development from prothylakoids to grana thylakoids in Phaseolus plastids. In the present study, the fact of the transformation of PTs to primary thylakoids via perforated membranes was confirmed. Particles, 70-80Å in diameter, were located on both PF and EF fracture faces of PTs. These may be considered core particles. As the thylakoids develop in the light, 70-80Å particles grew up to 165Å in diameter. However, except for the grana thylakoids, the total number of particles per unit area remained nearly constant throughout the development of monolayered thylakoids including PTs and stroma thylakoids. On illumination, it appears that the size increase of core particles in PTs proceeds in stepwise way. This indicates that the enlargement of particles occurs by the association of core particles with other ones.