Healthy dry seeds of pusa ruby variety of Lycopersicon esculentum Mill. were irradiated with gamma rays at 10 KR, 20 KR, 30 KR, 40 KR and 50 KR dose levels. Meiotic studies were made in treated plants as well as in control plants. At metaphase I, meiotic abnormalities like clumping and stickiness of chromosomes, univalents, multivalents, fragments and irregular grouping of chromosomes were observed. At anaphase I, there were laggards and unequal grouping of chromosomes at poles. Germination percentage and pollen fertility were also studied. Pollen sterility seems to be the cumulative result of various abnormal meiotic stages as well as of physiological and genetic damages induced probably by breakage of chromosomes. The frequency of meiotic abnormalities with reference to the effect of radiation doses is discussed.
Autotriploid plants were obtained from the selfed progeny of C2 generation autotetraploids. Chromosome associations such as IVs, IIIs, Its and Is were observed both at diakinesis and metaphase I. The occurrence of quadrivalents is presumed to be either due to a single interchange or duplication in a certain chromosome of the genome. The mean chiasma frequency in them was found to be significantly less than one and half times to that of the corresponding diploid. Meiotic irregularities such as laggards and irregular distribution at anaphase I and II were encountered. Pollen and seed fertility is very low. The probable origin of triploids from the tetraploid progeny is discussed. The present findings are compared with those reported earlier.
Three plants with reciprocal translocation of chromosomes were isolated from M1 progeny of Sesbania aegyptiaca (Poir.) Pers., after treating the dry seeds with 10, 20, 30, 40 and 45 Krad doses of gamma rays. The cytological observation of these plants revealed that in each case a reciprocal interchange involving two non-homologous chromosomes has taken place. The plants have been studied for their meiotic behaviour, with particular reference to type and frequency of multiple associations, mode of orientation of interchange multiple at metaphase-I, disjunction at anaphase-I, and chiasma frequency. The consequences of these factors vis-a-vis the fertility has been discussed.
Karyotypes of ten taxa of the geuns Lycoris have been analyzed minutely. Chromosomes of Lycoris are fundamentally classified into three categories, M, T, and A type as mentioned in the previous paper (Kurita 1986). Chromosome number and formulated karyotype of each taxon are summarized in Table 13. L. aurea is highly sterile and it is supposed to be a hybrid or chromosomal mutant. In L. albiflora, a new cytorace having 2n=18 is found. Karyotype of this race consists of 5M, 1T, 11A, and lm type chromosome. The m type chromosome must be a by-product of Robertsonian fusion of two A type chromosomes. This may be a hybrid between L. traubii and L. radiata. Karyotype consisting of 3M, 5T, and 11A type chromosomes of L. cv. “lactiflora” is the flrst record in this genus. Origin of this sterile diploid plant is unknown. Other three triploid sterile taxa are also considered to be hybrids, but the exact origin of them is undecided. L. squamigera may be a hybrid between L. straminea and L. sprengeri as pointed out by Inariyama, and a parent of L. houdyshelii is supposed to be L. longituba according to its karyotype and gross morphology. The m type chromosome found in a complement of L. incarnata must be a by-product of Robertsonian fusion between two A type chromosomes of an unknown parent.
Eighteen genotypes of Costus speciosus originally collected from different geographical regions of India have been assessed for their somatic chromosome number, plastid number in the stomatal guard cells and diosgenin content of the rhizomes. Chromosome counts show that two are diploids, four triploids and the remaining twelve are tetraploids with 2n=18, 27 and 36 chromosomes, respectively. Clear differences between diploids, triploids and tetraploids for chloroplast number in the stomatal gurad cells suggest that plastid counts can be used as a parameter for identification of intra-specific chromosomal races. A limited variation for diosgenin content of the rhizomes which ranges from 1.232% to 1.670% is attributed to the genetic differences in these genotypes. No correlation is established between ploidy status and diosgenin content of the rhizomes.
Lens esculenta, L.culinaris, Pisum sativum and P. arvense which were included in the present study belong to one of the economically imporatnt families-Leguminosae. The somatic chromosomal anomalies were studied after root-tip (1/2, 1 and 2 hr. treatment) and seed-soak (24 hr. treatment) followed by fixation in Farme's fixative. Root-tip squashes were made in 1% acetocarmine. The used concentrations of Benzene hexachloride (BHC), Lindane and Endrin were 0.01%, 0.02%, 0.03% and 0.04% and of Aldrin and Heptachlor were 0.05%, 0.1%, 0.2% and 0.3%. A considerable fall in mitotic index was noticed from control in all treatments. The most common chromosomal abnormalities induced by these pesticides were-inactivation of spindle mechanism, condensation of chromosomes below their normal size, chromatin bridges at anaphase and telophase. Multipolar spindles were observed after BHC, Lindane and Endrin treatments. Only BHC and Lindane were found to induce C-mitosis. However, Lindane was found to be a less potent polyploidizing agent. Multinucleate cells were observed only in BHC treatments. Fragments were observed occassionally in BHC, Lindane, Endrin and Heptachlor treatments.
The present study was carried out to test the mutagenic potential of some chlorinated pesticides using L. culinaris, L. esculenta, Pisum sativum and P. arvense. Studies were made through SEED-SOAK TREATMENT-pre soaked seeds were treated with different concentrations of pesticides and after thorough washing with distilled water were allowed to grow in experimental polts, and SPRAY TREATMENT-the normal plants were sprayed at flowering stage for successive 5 days. The flower buds were fixed in Farmers fixative and squashed in 1% acteto-carmine. The common abnormalities induces by all pesticides are sticky chromosomes and multivalents at metaphase-I. Laggards were frequently observed at metaphase-I but occassionally at anaphase-I and ana-telophase-II. In BHC, Lindane Heptachlor and Endrin treatment the fragments and bridges were observed in higher magnitude at anaphase-I than ana-telophase-II. Cytomixis was observed only due to spray treatment of BHC in L. esculentaL. culiuari. A few polyploid and binucleate cells were also noticed due to BHC spray treatment. Hence continuous and prolonged application of these pesticides may cause change in pure germ line.
The karyotypes of 21 samples of the genus Silene L. from the Mediterranean region, belonging to 10 species and 8 sections, have been investigated. Diploid chromosome numbers of 2n=24 are reported in S. succulenta, S. rubella, S. ligulata, S. biappendiuclata, S. alba, S. gallica and S. nocturna. In S. vulgaris both 2n=24 and 48 are recorded in different accessions. In addition 2n=20 is recorded in two accessions of S. conoidea, and 2n=30 in S. longipetala. Considerable variation in mean chromosome length was found. S. biappendiculata, S. succulenta have the longest chromosomes, while S. conoidea has the shortest chromosomes. The karyotypes are more or less similar with respect to centromere position, being composed of metacentric to submetacentric and acrocentric chromosomes. The cytological characteristics provide evidence for the separation of S. longpetala and to some degree S. conoidea from the rest of the species studied.
Cytomixis was recorded during microsporogenesis in three varieties of Urochloa panicoidesP. Beauv. (Poaceae) in different percentages as var. pubescens 10%, var. marathensis 12% and var. velutina 18%, while var. panicoides showed only occasional cytoplasmic connections. It was commonly observed during summer. Also, the robust plants raised in the experimental garden showed highest percentages of cytomixis. The phenomenon was more frequent in prophase I and noted upto anaphase II with decreasing frequencies. The amount of migrating chromatin was also reduced as meiosis advanced. The role of nucleolus was not clear. Cyto-logical analysis of cytomictic plants revealed the formation of upto 6% of hypo-and hyperploid meiocytes, triads, irregular tetrads and polyads. The seasonal occurrence and the intervarietal differences in the frequencies of cytomixis demonstrates that it is the expression of unbalanced genetic system of plants in response to environmental conditions. The pollen fertility and seed setting was not affected by this process indicating that the phenomenon is not of much significance.
The regulatory effect of EMS on chlorophyll metabolism was studied in two hexaploid wheat genotypes. Presoaked seeds were treated with EMS 0.2%, 0.4% and 0.6% at 3½ hr., 7 hr. and 9 hr. durations respectively. Leaf extracts from treated as well as from control plant were compared spectrophotometrically to determine Chl. a, Chl. b and total chlorophyll contents, and its relationship to grain weight was established, using plants grown in pot conditions. Total chlorophyll content of treated plants demonstrated significant increase over their parents (control). Maximum increase (93.87%) in toatl chlorophyll content was recorded in variety Al-Samma at EMS 0.4% with 7 hr. duration, with subsequent increase of 35.89% in seed weight, indicating this treatment can effectively be exploited to evolve mutants with enhanced chlorophyll metabolism. Chlorophyll content was correlated to 100-seed weight on plant basis. Significant positive relationship between chlorophyll content and seed weight was detected in most of the EMS treatments. The improvement of genotypes with high chlorophyll content might result in the improvent of photosynthesis in wheat plants leading to the improvement of grain yield.
Spontaneous occurrence of coenocytism has been reported in the PMCs of purple-flowered strain of Digitalis purpurea from Ootacamund. Report of this kind is new not only for the genus but also for the family Scrophulariaceae. This phenomenon was visible right from the early stages of meiosis. Both synchronous as well as asynchronous nuclear division in coenocytes has been observed depending upon the stage of the PMCs taking part in fusion. The coenocytes are larger than the normal PMCs depending upon the number of PMCs involved in fusion. It is assumed that coenocytes were formed by the fusion of adjacent PMCs on dissolution of intercellular walls. It is also concluded that coenocytism in the present material could be due to natural mutations.
A detailed cytological and cytochemical investigation involving determination of somatic chromosome number, karyotype, total chromosome length, volume and estimation of 4C nuclear DNA were carried out in 9 different species and varieties of Agave. Of the nine species studied, five belonged to diploid level with 2n=60 chromosomes and the rest were triploid, tetraploid, pentaploid and hexaploid having 2n=90, 120, 150 and 180 chromosomes respectively. Inspite of a distinct bimodal karyotype with very long and very short chromosomes in the 5: 25 ratio and a constant base number of n=30 chromosomes featured in the detailed karyotype analysis, each species has got its own distinct karyotype, differing from the rest in minute details. The total chromosome lengths and volumes differed both within and outside the same ploidy level and the volume did not necessarily increase with the increase in chromosome number. The amount of 4C nuclear DNA, estimated through Feulgen microspectrophotometry and expressed in arbitrary unit of relative absorbances, did not show much variations in the diploid species, while the triploid species revealed slightly lesser value than that of one specific diploid species. The difference in the amounts of nuclear DNA was insignificant amongst the pentaploid and hexaploid species as compared to the difference of their chromosome numbers. No direct correlation could, however, be established between the cytological parameters and the amounts of nuclear DNA. On the basis of overall analysis, the influence of structural alterations in affecting the amounts of nuclear DNA as well as other cytological characters from diploid to hexaploid level has been suggested.
Crosses were made between S. scabrum Mill. and S. americanum Mill. with a view to understanding their interrelationship. The crosses were successful, only when the higher chromosomal form, i.e. S. scabrum was used as female parent. Cytomorphological features of the species and hybrid were studied. The F1 hybrid was tetraploid with n=24 chromosomes. Although 70% pollen mother cells showed meiotic irregularities, a large number of fertile seed and stainable pollen were recorded. This could be due to genetic harmony between the parental species. The break-down of meiosis seems to be primarily due to chromosomal cause. From the occurrence of as few as 12 bivalents in almost all the pollen mother cells, it is suggested that S. americanum or one of its close relatives has participated in origin and evolution of S. scabrum.
The structural changes of the filamentous green alga C. brachygona growing in iron-ore tailing which contained high levels of manganese, cadmium, chromium, copper, iron, lead and zinc were investigated with the electron microscope. The most conspicuous ultrastructural change of the algal cells was the substantial increase in the thickness of the side wall and the cross wall between adjacent cells, which could trapped large amounts of metal precipitates. The well lamellated outer portions of the thickened side wall probably functioned in preventing rapid movement of the metal precipitates through the wall into the cell lumen. There was an increase in the number as well as the size of the lipid bodies in the metal-tolerant algal cells. Reduction of the size of the chloroplasts which showed a reduced internal organization was also observed. In addition, the presence of multivesiculate bodies in the cytoplasm which were not detected in normal algal cells, served as reservoir for the sequenstration of metal ions in the cytoplasm. Deposition of metal precipitates was not detected in the chloroplast, mitochondria and nucleus of the cell however. The metal tolerance exhibited by C. brachygona was therefore attributed to these ultrastructural changes of the algal cells, which enabled the algal filaments to survive and maintain growth in the metal-riched environment.
The effect of different mutagens on the induction of mitotic aberrations in diploid and tetraploid Solanum nigrum L. has been studied. All the mutagens were found to be effective in inducing mitotic chromosomal aberrations in case of both the diploid and tetraploid. The percentage of cells showing mitotic abnormalities was found to be more in the tetraploid S. nigrum as compared to the diploid.
The ultra-structural basis of Sertoli cell-germ cell interactions during mammalian spermatogenesis has been the subject of much study. While examining ontogeny-related interactions between differentiating germ cells and Sertoli cells in the colony-bred albino rat, we observed selective uptake of spermatogonial cytoplasm by adjoining Sertoli cells through the formation of double membraned “bleb-like” structures. In addition, evidence suggesting roles for pinocytosis and exocytosis in such intercellular communication was also obtained.
Three cytoraces were observed in L. traubii. The karyotype of these taxa consists of l0M+2T, 9M+4T and 8M+6T respectively. Measured and calculated numerical values of each chromosomes in the standard karyotype are summarized in Tables 2, 3 and 4. Proximal region of some T type chromosomes shows heterochromaty in aceto-orcein stained preparations. A small amount of C-banding positive heterochromatin is found in this region (cf. Kurita 1986). Cytological and morphological characters of these taxa rather indicate that each of the fertile taxa having 2n=12 and 2n=14 is independent biological species. Therefore, the sterile taxon having 2n=13 may be a hybrid between both fertile taxa. Some other intraspecific karyotype variations were found as shown in figures. One intraindividual karyotype mutation was found in a bulb from Yozadake population. In this case, one M type chromosome changed into A type chromosome by large deficiency.
1) In the germinal vesicle of Pseudorhyncus, a peripheral lamina was found lining the inner surface of the inner nuclear membrane. It consisted of lamina members running in various directions along the surface. 2) The lamina members were digested by the action of proteolytic enzymes. This demonstrates that they are proteinaceous in chemical nature. They remained resistant against the hot perchloric acid extraction after Douglas (1970). This implies that they do not contain deoxyribonucleic acid in appreciable amount. Therefore, the lamina corresponds to the so-called “fibrous lamina” (Fawcett 1966 and others). 3) The lamina members consisted of two structurally different regions, irregular and regular. The former region exhibited a fibrous or a vesicular pattern with no definite orientation. In contrast, the latter consisted of straight cylindrical tubules or rods, lying parallel with one another and perpendicular to the lamina length. These tubules are the fundamental constituent of this region. The existence of this tubular structure in the lamina may facilitate a possible migratory movement of some small molecules between the cytoplasm and the large nucleus reinforced by the lamina.
1) Intraspecific variation in the karyotype of L. radiata was studied. Five hundred and nineteen bulbs from fifty-eight populations were examined. 2) Standard karyotype consisting of thirty-three A type chromosomes (2n=33=33A) was found in 97.3% of examined materials. 3) Standard karyotype includes two A type satellite chromosomes heterozygously. Namely the size of short arm of one satellite chromosome is smaller than that of the other. Moreover, four A type chromosomes having high r value are always included in the standard karyotype. 4) In some cells, three satellite chromosomes were observed. 5) Robertsonian fusion between two A type chromosomes had occurred in some bulbs, then M' and m type chromosomes were produced. So, this m type chromosome is euchromatic and it segregates normally and inherits into the daughter cells. This chromosome must be equivalent to m type chromosome observed in L. albiflora and L. incarnata. 6) The karyotype consisting of 31A and 1M' was found in the bulbs from Ebira population. This M' type chromosome might also be a product of Robertsonian change between two A type chromosomes, and in this case m type chromosome or fragemented short arms were eliminated. 7) Secondary constriction at the proximal region of long arm of one A type chromosome was observed in the complements of some bulbs from Uematsu population. 8) The birthplace of this triploid plant is supposed to be China, and its very stable karyotype also suggests that it is a prehistoric naturalized plant introduced into Japan from China with the traffic of men.
Autotetraploid has been raised in Lindernia crustacea, a medicinal weed, by treating the seedlings with 0.2 percent of aqueous solution of colchicine for 20 hours. Morphological and cytological characters of colchiploid and diploid were studied in detail. Cytology of colchiploid was highly non-synchronized and one interesting phenomenon was observed that the frequency of multivalents were very low whereas the sterility of pollen grains was very high. Other anomalies like clumping of chromosome at various stages, precocious separation of chromosomes, formation of univalents and unequal distribution of chromosomes at anaphase I and II were also observed and discussed. Pollen grains were variable in size.
Detailed karyotype of Lindernia crustacea and Lindernia multiflora have been studied for the first time. It has been found that the L. crustacea has a more asymmetrical karyotype than L. multiflora. It has been concluded that evolution in these species has been towards diminution in size and increase in unmber of the chromosomes.
Action of Teniposide on the Ultrastructural Aspect of Human Metaphasic Lymphocytes Chromosomes Teniposide tested “in vitro” on human lymphocytes cultures of 24 hours, at various concentrations, inhibits the formation of the mitotic metaphase plates and brings about thickening of the chromosomal fiber, observed in electron microscopy. After 3 hours of exposition in the culture, teniposide induces numerous chromosomal aberrations: gaps, breaks, exchanges.
A change in the chromosome number of some PMCs in an interspecific hybrid of Coix L. (C. gigantea×aquatica, 2n=16) through cytomixis is reported. In the cytomictic PMCs the chromosomal changes are both quantitative, having 2n=13 and 2n=17 chromosomes instead of the usual 2n=16 and qualitative, having variable number of parental chromosomes instead of the usual 10+6 gigantea and aquatica combination. Causes, places, types, consequences and nature of cytomixis are discussed. It is argued that in the PMCs, the displacement of chromatin from its nearly central position towards periphery, as if acted upon by some force and in preparation to migration, cannot be without any purpose, the latter though as yest not clear to us.
Study of meiosis in the pollen mother cells showed n=30 in Commelina paludosa, n=30 and 60 in C. erecta, n=15 in both C. hasskarlii and C. diffusa. The presence of n=15 or its multiple in these species suggests that they have a basic chromosome number of x=15. Nearly regular formation of bivalents even in C. paludosa and C. erecta, suggests that they are either old established autopolyploid or allopolyploid. Majority of the bivalents in all these species were ring-shaped with mostly terminal chiasmata. The mean chiasma frequency per bivalent and mean chromatin surface area per bivalent respectively were 1.71±0.04 and 9.34±0.38 in C. paludosa, 1.76±0.03 and 8.85±0.46 in C. erecta, 1.79±0.04 and 9.73±0.44 in C. hasskarlii and 1.83±0.05 and 6.89±0.39 in C. diffusa. The absence of any correlation between the mean chiasma frequency per bivalent and the mean chromatin surface area per bivalent supports genetic control of chiasma formation.