Present work includes cytological studies on 13 species of the genus Panicum Linn. from North-Eastern India. Panicum auritum (2n=30, n=30, 36), P. cambogiense (n=9) and P. humidorum (n=18) have been cytologically reported for the first time. New chromosome numbers have been detected in P. notatum (n=36), P. repens (n=30), P. trypheron (n=21) and P. walense (n=18, 36). Evolution of base number x=9 from x=10 and polyploidy in the genus have been discussed.
With a view to investigate the possible reasons behind the yield reduction in chilli due to the application of higher than recommended doses of insecticides, the present studies were under taken with BHC and Nuvacron. It was observed that both germination and survival effected in all the treatments of BHC and Nuvacron and the injurious effect of Nuvacron on germination and survival was more than BHC. Similarly, both BHC and Nuvacron produced abnormalities in dividing PMCs and the frequency of these abnormalities was higher in Nuvacron than in BHC. Pollen sterility which was observed in 9th day after spray was very low in BHC and comparatively high in Nuvacron. Within each insecticide the decrease in germination and survival and increase in percent of anbormal meiotic cells and percent of pollen sterility followed an increasing trend. Yield was uneffected if BHC treatments, while it has increased in normal concentration (0.04%) of Nuvacron and decreased in highest concentration (0.12%). The yield is on par with control in Nuvacron 0.08 percent. It was concluded that 0.04 percent concentration of Nuvacron was the safest for the effective pest control and yield increase. The farmer should be more careful for not to use higher than the recommended dose since there is danger of break-down of genetic purity of the variety due to the chromosomal abnormalities besides the yield reduction at higher concentration of Nuvacron.
Mutagenic effect of single, pre- and postirradiation treatments with EMS, MMS and γ- rays was studied in highly drought resistant Tephrosia purpurea, in relation to germination, lethality of seed roots, survival, final height and chromosomal abnormalities. EMS and MMS in aqueous (pH 5.3-5.8) were more effective than in pH 7 and among the two chemicals, MMS is more potent both individually and in combination. In comparison to control, seed germination percentage increased at some dose levels. Preirradiation has been found to be more effective than postirradiation treatments. Some specific doses of pre- and postirradiation had pronounced synergistic effect.
Chromosomal investigation was carried out on 8 populations of Ocimum sanctum L., of which 34 chromosomes in somatic cell is a new report for the species. Mitotic and meiotic studies were made in the three common cultivars of this species found in India. No correlation could be established between the chromosome number and the phenotypes of the species. Inspite of the phenotypic variation and variation in chromosome number, the number of nucleolar chromosomes was always observed to be 4 in all the populations. However, minor structural differences do exist among them which vary from population to population. The presence of the constant number of 4 satellited chromosomes in all the populations studied suggests that they may contain certain vital genes for the survival of the species. It is also suggested that cytotypes with 34 and 36 chromosomes owe their origin to cells having 34, 35 and 36 chromosomes met with in some of the populations. This study was supported by the grant of CSIR, New Delhi.
Using various cytochemical techniques, the author has studied the way in which mucilage is secreted by the trichomes of Psychotria bacteriophila. As in all cells specialized for the secretion of mucilage, the dictyosomes play the most important role. However, their functioning in these cells is rather remarkable since they do not produce large secretory vesicles. The fenestrated cisternae on the secretory face bud small vesicle which open in the periplasm. Then the polysaccharide secretion condenses. More or less complete lysis of the cell wall then allows the mucilage to migrate to the outside of the trichome. In contrast with what happens in other mucilage-secreting cells, the endoplasmic reticulum plays a part in the secretory process, since it produces a protein fraction which, after expulsion from the cytoplasm, associates itself with the polysaccharide fraction. The trichomes are thus, in fact, the site of a twofold secretion; of polysaccharides (and perhaps of glycoproteins) in the dictyosomes, and of proteins in the cisternae of the endoplasmic reticulum. They produce, then, a complex kind of mucilage which constitutes a veritable culture medium for the symbiotic bacteria.
It has been found that the meiotic-cycle is normal as in other higher plants and is completed within a short-time (from 10 pm.-11 pm.). From diakinesis and second meiotic prophase, the chromosome number is 22.“Diffuse”stage was also observed. From the present investigation it can be concluded that X-like chromosomes had median centromere and spherical chromosomes were either metacentric or sub-metacentric.
Testicular fragments are treated by hypophases (bidistillated water or KCl solutions) during 2-8 h. at 37°; the cells are spread on the surface of sheet grids covered with formvar plus collodion films; interesting stages are selected under LM before observation under EM. Leptotene shows single axes connected with numerous fibers. During zygotene the axes pair two by two and the synaptonemal complex is gradually formed. Pachytene is the most frequent stage, the SC shows the typical tripartite configuration; DNase treatment removes most of the chromatin fibers, but the tripartite structure persists; pronase treatment removes the central element and the transverse fibers, and induces a relaxing of the fibers. During pachytene and diplotene, the chromomeres are clearly individualized, numerous fibers connect the chromosomes with the nuclear envolope; inter-chromosomal fibers join the bivalents. At diakinesis and metaphase, chromosomes are highly condensed and no parts of SC were observed. The above results are compared to those obtained by other water spreading techniques.
Cytological investigations on Camellia sinensis, C. assamica, and their hybrid (Jat) were undertaken in the present study. The somatic chromosome number (2n=30) observed in the species C. sinensis and C. assamica is in conformity with the earlier reports. Also meiosis in pollen mother cells was regular in these species. However the meiosis was irregular in China-Assam hybrid. Localized unpairing at pachytene, stickiness resulting in apparent higher association, laggards, sticky bridges etc. and variations in the number of daughter nuclei at telophase II were encountered in the hybrid. It is concluded that these cytological abnormalities are caused by molecular level interactions between the genes from C. sinensis and C. assamica. In the light of the original geographical isolation of China tea and Assam tea, different morphology and the aberrant meiosis in the hybrid, it appears better to consider them as distinct species.
A natural tetraploid form of Matricaria inodora L. is analysed both mitotically and meiotically. Its karyotype was consisted of nine quadruples of structurally similar chromosomes. The meiotic behaviour of M. inodora in respect to the multivalent formation is similar to that of observed in M. chamomilla colchiploid. The results suggest autoploid nature of the present material.
The nucleoli and the NOR-carrying segments (bodies) of two clones of Allium sativum were cytologically studied during the mitotic cell cycle by use of a method devised from the C-banding technique, which allowed satisfactory demonstration of the nucleoli and the NOR-carrying segments as C-positive regions at the same time. The nucleoli of the two clones differed in size: one (clone A) had four equal-sized nucleoli while the other (clone B) had one large, two medium and one small nucleolus at interphase. The small nucleolus was found to originate from a nucleolar chromosome on which the secondary constriction was absent. The NOR-carrying segments were subject to condensation-decondensation (segmentation) during the mitotic cell cycle, that is, some of them were deformed into string-like elongated configurations at anaphase, segmented into minute C-positive granules within the nucleoli at telo-phase to interphase and reorganized into completely condensed C-positive segments through the string-like elongated configurations at prophase. But one of the NOR-carrying segments of clone B was not subject to the morphological changes as above and it always, persisted condensed state throughout the mitotic cell cycle. It seemed that the nucleolar size correlates with the morphological changes of the NOR-carrying segments. This observation also confirmed that the nucleoli never originated from the constricted portions but from the C-positive segments on the proximal region of the large satellite.
Pachytene nuclei of rice microsporocytes were examined about centromere constitution, chromomere pattern and nucleolar situation by flame drying method and Giemsa stain. Uridine treatment of intact microsporocytes before preparation distinctly revealed the centromere on late pachytene chromosomes, that is, four equal entities were detected in a centromeric region. Chromosomes treated in KCl solusion were stained clear enough to be analysed their chromomere patterns on 12 bivalents. Mid-pachytene chromosomes were suitable for chromomere analysis and capable of discriminating 12 bivalents with their chromomere patterns, centromere position and length. Supernumerary micronucleoli were frequently observed in a pachytene nucleus besides a macronucleolus. They were situated in three conditions; free from chromosomes, adhered to the surface of various intervening sites of chromosomes and adhered to the ends of chromosomes. In some nuclei micronucleoli appeared to be excised out from macronucleoli were noticed. These observation indicated the origin of micronucleoli.
The occurrence of polyploid cells in developing flowers undergoing meiosis following gall attack on the flowering stems is discussed. Tetraploid pollen mother cells in some flowers underwent normal meiotic division producing apparently normal tetrads. In others meiosis showed many abnormalities. Although much has been documented on effects of galls on mitotic cells no information has been available previously on effects on meiosis and its possible significance.
Active nucleolus-organizer regions (NOR) were identified on chromosomes 3, 4, 5, 7, 8, and 9 in a diploid Chinese hamster primary strain (CHFP-WG). However, they appeared only on one chromosome 4, both chromosomes 5, and the isochromosome for the short arm of chromosome 8 (iso 8p) in an established Chinese hamster line displaying gross chromosomal rearrangements (AK412). Some recognizable NOR sites, exhibiting active NOR in CHFP-WG cells fail to exhibit active NOR in AK412, suggesting that a specific suppression of NOR has occurred in the AK412 cells.