Detailed karyomorphology of four morphotypes of Gloriosa superba is reported. In gross karyomorphology they were similar, but with respect to total chromosome size and chromosome structural details of certain individual chromosomes, recognisable difference was noticed between and among the different morphotypes. This is pointed out to shed light on the role of intraspecific karyotype changes and its bearing on the plant morphological difference evident in the species.
The volume of pollen, total number of pollen/flower, the percent of pollen germination and tube growth of long-styled flower were higher than the short-styled flowers in S. torvum. In addition, the pollination studies were conducted among the four selected sets for optimum fruit set investigation. Fruit set was not seen in both the first and second sets (_??_ short-short _??_ and _??_ short-long _??_). However, the maximum fruit set was obtained in the fourth set (_??_ long-_??_ long). Pollen grains of long-styled flowers irradiated with 1-800 krad were germinated in the basal medium. The percent of pollen germination and the tube growth was stimulated over the control with 1 and 50 krad dose exposures, but increasing dose rates inhibited both the above processes. Utilization of insoluble polysaccharides, and the synthesis of RNA and protein were enhanced over the control with the effect of 50 krad. The higher (800 krad) dose exposures inhibited all the above cytochemical constituents. Various dose-treated pollens were used to pollinate the stigma surface of the long-styled flowers. The fruit set, fruit volume, fresh and dry weight of fruits, and the number of seed set/fruit, were enhanced over the control by 1 and 50 krad, while the higher doses caused inhibitory effect. Interestingly, the fruit set was not caused by radiation doses 400 krad and above.
Testicular cells of grasshopper, Poekilocerus pictus Fabr., were subjected to standard C-banding procedure. Number of bands per genome during pachytene, diplotene and diakinesis varied from 15-20. Chromosomes were well spread and countable at metaphase-I and anaphase-I; however, no C-bands were observed at these stages, which might be due to high condensation of chromosomes. The 2n number was found to be 19, (9II+X) and the sex determining mechanism to be of XO type. The mean chiasma frequency per cell was 16.40±0.41 at metaphase-I.
A plant exhibiting semi-dwarf stature was identified from a gamma ray induced VM7 population. Cytomixis was observed in 30% of the meiocytes. Cytoplasmic connections were observed in all stages of PMCs ranging from early prophase stage to microspore stage. Movement of chromatin materials was also observed. A wide spectrum of cytokinetic aberrations was also noted. As a result of these abnormalities the plant showed total male sterility. In Hevea, male sterility can be exploited for the production of hybrid seeds and dwarf stature in breeding programme.
Eleven species and five subspecies of the genus Ixeris s. lat. were karyologically investigated. Somatic chromosome numbers and karyotypes of Ixeris polycephala (2n=16), I. chinensis ssp. strigosa (2n=24), I. transnokoensis (2n=14), and I. makinoana (2n=14) were examined for the first time. Further, the karyotypes of I. repens, I. chinensis complex, and I. laevigata, were also described. As a result, plants with x=8 and small relative chromosome length, and those with x=7 and large relative length, were recognized in the genus. The former group possesses the rod or round prochromosome type of resting nuclei, but the latter has the diffuse chromosome type. These karyological features proved to be good criteria for defining Ixeris and other related genera, since they match very well with gross morphological as well as anatomical characters. The species of Ixeris examined thus were divided into two groups on the basis of chromosome morphology. The first group, with x=8 and similar karyotypes, is composed of I. repens, I. stolonifera, I. debilis, I. longirostrata, I. polycephala, I. chinensis complex and I. tamagawaensis. The second group, with x=7, comprises the I. dentata complex, I. laevigata, I. transnokoensis, and I. makinoana. In conclusion, the species with x=7, which have been referred to sect. Ixeridium, no doubt represent a distinct phylogenetic group, and should be separated from those with x=8 as an independent genus.
Karyotype analysis were made using root tip, leaf tip, petal tip as well as pollen mitosis in 13 species of Nepal himalayas. The chromosome number of Primula atrodentata W. W. Sm. (2n=22); Primula deuteronana Craib (2n=22); Primula edgeworthii Pax (2n=22); Primula erosa Wall. (2n=22, 24); Primula irregularis Craib (2n=22); Primula rotundifolia Wall. (2n=22) are reported here for the first time. Genetical diversity has been recorded in Primula denticulata Sm. with having variable chromosome numbers of 32, 34, and 44. The chromosome number of Primula elliptica Royle is observed as 2n=24. Data on the chromosome numbers of Primula gracilipes Craib (2n=22); Primula malacoides Franch. (2n=18); Primula petiolaris Wall. (2n=22); Primula reticulata Wall. (2n=22); Primula sikkimensis Hook. f. (2n=22), reported in previous references have been confirmed. The basic number 11 is predominating in this genus studied. Critical notes are made in the karyotype characteristics and its interrelationship among species.
The bactericidal broad spectrum drug Norbactin containing Norfloxacin has been proved to be genotoxic when human dose equivalent of it was orally administered into mice. The frequency of bone marrow chromosome aberrations assessed in 6 intervals between 15 min and 7th week and the micronucleated erythrocytes and first spermatocyte metaphase chromosome aberrations assessed in 6 hr, 30 hr and 72 hr and sperm with abnormal head morphology assessed in 6 hr, 30 hr, 72 hr, 1st wk and 7th wk was significantly high than that of normal specimens. All the four testing parameters were found to have dose-effect relationship when different set of mice were orally administered with 1/2, 1 and 2 doses of Norbactin. Therefore, like antibiotics of biological origin, the broad spectrum antibactericidal Norbactin belonging to the new class “Fluoro quinolones” has been found to be genotoxic agent by a battery of tests in experimentally treated mice.
Chlorpyrifos is one of the widely used organophosphorus insecticides. The compound and two of its main metabolites are known nucleic acid alkylating agents. Potential of the compound as a genotoxic agent was determined on the basis of chromosome damage and rates of sister chromatid exchanges in cultured human lymphocytes. Four treatments (0.02, 0.20, 2.00 and 20.00μg/ml), a solvent control and an untreated control were used in three replications of 4-hour and 24-hour exposures to assess damage to chromosomes. One replication of the four treatments and two controls based on 24-hour exposure was used to determine sister chromatid exchanges. Chromosome damage assessed primarily as gaps and breaks did not increase at a statistically significant level. The trend was almost similar for sister chromatid exchanges though for one of the controls, significance was reached for one treatment level. It seems that short term exposure to chlorpyrifos at these dosages is relatively safe. Efforts however, must continue for procurement of safer compounds that are not reactive to nucleic acids.
Higher polysomic constitutions occur very rarely among plants and animals and whenever they arise are constitutionally weak and usually highly sterile. A quadruple trisomic (2n=24, 2n+1+1+1+1) chromosomal constitution has been reported for the first time from among the selfed progeny of a spontaneous autotriploid (2n=30). Coix lacryma-jobi. Large number of PMCs showing four trivalents at diakinesis confirmed its quadruple trisomic nature. Inspite of polysomy this aneuploid is healthy and partly fertile.
Chinese Hamster chromosomes R-banded in vitro were gamma-irradiated and chromatid breaks and rearrangements examined by electron microscopy employing whole-mounting tech nique. Breaks were preferentially located at the point of transition between G- and R-bands where the chromosome showed an average diameter 71.65% of the wide condensed R-bands. This result was similar to the average diameter of narrow G-bands. Three chromosomes which were thin sectioned presented their broken terminal end organized as a coil constituted by two 23 nm wide chromatin fibers coiling together. Coils diameter was 43.70% of the mean chromatid diameter. The border of damage-breakage was analyzed in whole-mounted chromosomes where breaks were photoinduced in BrdU-substituted DNA. Measurements of the angle of the sharp border of damage with respect to the chromatid axis showed a tendency to be more perpendicular as condensation progressed. These results clearly correlate with the several levels of chromatin fiber organization of the metaphase chromosome.
Trisomics for two chromosomes have been isolated in the progeny of cross between disomic and aneuploid individual in Plantago lanceolata L. The karyotypic analysis and meiotic studies has revealed their primary nature and identification as Triplo-1 and Triplo-4. Attempt has been made to study impact of trisomy on plant phenotype and fertility. Due to the phenotypic plasticity within the species even at disomic level, the morphological variations induced by trisomy do not become vivid.
Interspecific hybridization in between L. operculata and L. acutangula brings out certain features of great relevance for tracing inter-relationship between these species. The F1 plants of L. acutangula×L. operculata and their reciprocal are fertile. All hybrids possessed the monoecious sex-form. A detailed cytological investigation in the F1 hybrid between L. acutangula×L. operculata and their reciprocal has been done. The inheritance studies of certain economically important characters like fruits in the hybrid have been made.
Long term use of barbital sodium in the albino mice mother during pregestation and gestation periods results in depressed adrenal function of the mother. Transfer of this agent through placenta and breast milk induces the adrenocortical activity of the newborns as a whole. Hence a biphasic role of this pharmacodynamic agent on adrenal function is observed which is interrelated not only with the days variance of treatment but also with the age of the animals. Results have been interpreted both histologically and histochemically.
In recent times, the work on genetic control of insect pests has been very much facilitated by the use of chemosterilants. The present investigation has been carried out with an aim to study the cytogenetic effects of Thio-TEPA (triethyllenethiophosphoramide and CAS No. 52-24-4) an important chemosterilant, in the brain cells of mosquito Culex pipiens fatigans. Two day old larvae were reared in 25 ppm and 5 ppm of Thio-TEPA separately. The chromosomes prepared from the brain cells of mid fourth instar larvae reveal that 25 ppm of Thio-TEPA induces chromosomal abberrations at a higher rate. The frequency of various kinds of chromosomal abnormalities were analysed, and the nature of action and damage caused by Thio-TEPA are discussed.
The somatic chromosome number in three different varieties of Cuminum cyminum L. and two varieties of Carum copticum Benth. and Hook. are 2n=14 and 2n=18 respectively. Most of the chromosomes in C. cyminum possess submedian or subterminal constrictions. Karyotype analysis shows gross morphological similarity in C. cyminum despite the evolution of different varieties. In length and volume of chromosomes, no marked variations among the varieties are found. The study of DNA content also reveals varietal constancy with slight variation in the different varieties of C. cyminum. A proportionate increase in DNA content is recorded with the increase in length and volume in the varieties. A gross homogeneity in chromosome morphology is also found in the two varieties of Carum copticum. Majority of the chromosomes possess either nearly median or nearly submedian centromere with little size difference of the chromosome complement. Along with minor karyotype differences in two varieties, a marked variation is found in total chromosome length and volume. However, 4C DNA value between the two varieties of C. copticum reveals a rather consistent picture. Therefore, the differences in chromosome length and volume may be attributed to differential spiralization and condensation of chromosomes along with the content of protein and DNA. The constancy in the amount of DNA in different varieties of same species is a clear index of the selective value of this amount.
Meiotic associations were studied at metaphase I in PMCs of autotetraploid and autotriploid plants of Russian wildrye (Psathyrostachys juncea). Autoploidy without the presence or action of the bivalentization system was demonstrated. In light of the meiotic behaviors in these autoploids, breeding strategies for Psathyrostachys juncea were suggested. Possible uses of these materials are described.
During meiotic study in a clone of S. spontaneum L. (2n=54), it was found that some (11.39±2.52%) PMCs undergo cytomixis during pre-metaphase-I. Unlike many instances, only 18 bivalents were found to migrate along with the nucleolus into the recipient cell, and 9 bivalents remained in the donor cell. This number is proposed to be suggestive of the existence of basic number of 9 in addition to previously reported basic numbers of 6, 8 and 10 in the polyploid series of this species. Possibility of existence of other diploid numbers in the series of 9 is discussed.
A chromosomal chimaeral plant with three distinct primary branches exhibiting diploid, mixoploid (diploid and tetraploid) and tetraploid numbers was recorded for the first time in colchicine treated plants of ×235, a local cultivar of chilli. Significant differences were observed in morphometrics of the three branches with regard to leaves, flowers, fruits and stomatal characteristics. The mixoploid branch displayed intermediate features of both diploid and tetraploid branches. Further, fertility and yield were high in chimaeral plant compared to those of the diploid and tetraploid sibs. The chimaeral nature can be attributed to the endoreduplication of some of the cells in the apical bud due to the differential activity of the colchicine. The mixoploid numbers may be formed as a result of spindle abonrmalities during premeiotic mitosis. The chimaeral plant has immense cytogenetic importance since it has the potentiality to generate polyploids and aneuploids in the progeny which in turn are powerful weapons in understanding the chromosomal architecture and cytogenetic relationships of the crop.
Wide variations in the number of nucleoli per nucleus was observed in a certain clone (2n=54) of S. spontaneum L. from Bhagalpur. Out of 563 PMCs analysed, 57% contained only one nucleolus, and the remaining had it ranging from two to seven. The number of cells with odd number of nucleoli were in abundance (37.66%). Some ratios were found between the volumes of nucleoli of different sizes, though the total nucleolar volume per nucleus never remained uniform.
Clastogenic effects of quinoline, isoquinoline and pyridine, three closely related members of the heterocyclic group of compounds have been studied in root tip cells of Allium cepa. Each substance was tested over a wide dose range. The untreated controls rarely showed the presence of fragments All the three chemicals produced marked clastogenic activity and induced a significant increase in the frequency of chromosome breaks and exchanges.