Karyotypic analyses were made using root tip mitosis in 19 species of South Indian Rosa-ceae. First record of chromosome numbers have been made in Rubus wightii (2n=14), R. rugosus (2n=14), R. fairholmianus (2n=14), R. gardnerianus (2n=14), R. micropetalus (2n=14), Fragaria indica (2n=14), Potentilla leschenaultiana (2n=28) and Alchemilla indica (2n=16). Most of the species studied show 2n=14 and 2n=28 chromosomes. Therefore, it is concluded that euploidy together with karyotype alterations of chromosomes play important role in speciation in Rosaceae.
Agrnonomic and cytogenetic analyses have been carried out in Trichosanthes anguina L., T. cucumerina L., T. palmata Roxb., and T. dioica Roxb. with its cultivars and wild relative. Some of the agronomic parameters such as flowering time, leaf and fruit morphology and yield have been found useful for delineating the cultivars. The higher yield is correlated with late flowering as demonstrated in ‘Kali’ and ‘Damodar’. The fruit weight is highest in ‘Damodar’ (46.05gm±3.35) while ‘Lata Bombai’ and ‘Sanjiban’ bear lighter fruits (31.42gm±5.30 and 30.54gm±6.75 respectively). The yield measured as quantity of fruits produced per plot (3m×1.5m) in a season varies between different cultivars. The cultivar ‘Kali’ shows by far the best performance in yield (120.20kg±12.08) which is followed by ‘Damodar’, ‘Kalyani’, ‘Lata Bomai’, ‘Sanjiban’ and the wild form. Uniformly 22 chromosomes have been recorded in the somatic complements of all the taxa investigated. The gametic number of 11 chromosomes is uniformly represented in all the members analysed. The genus Trichosanthes L. is characterized by a graded karyotype with metacentric to submetacentric medium sized chromosomes ranging in length from 5.74μm to 1.48μm. The somatic complements of the gynoecious cultivars of T. dioica and androecious T. palmata possess more than three pairs of chromosomes with secondary constrictions while the gynoecious form of wild T. dioica, monoecious T. cucumerina and T. anguina are distinguished by the presence of only three pairs of such chromosomes. A heteromorphic pair of chromosomes is represented in all the cultivars of T. dioica. The total haploid chromatin length has been found to vary between different taxa. The disparity index, in general, is lower in the wild taxa investigated. The heterozygous constitution of the taxa as indicated in the occurrence of chromosomal heteromorphy has probably arisen during long cultivation and selection. The significant role of structural alterations of chromosomes in inter-and intra-specific diversification has been demonstrated in the genus Trichosanthes L.
To assess the role of heterochromatin, if any, in intraspecific diversification, a detailed study of the distribution pattern of Giemsa C-heterochromatin in three gynoecious cultivars of Trichosanthes dioica Roxb., namely, ‘Kali, ‘Kalyani’ and ‘Sanjiban’ has been undertaken. The somatic chromosomes are characterized by distinct telomeric bands. The differential banding pattern can be conveniently used for distinguishing between the cultivars. The cultivar ‘Sanjiban’ stands apart from the rest in possessing seven chromosomes with one or more intercalary bands in addition to the telomeric bands at both arms. The cultivars ‘Kali’ and ‘Kalyani’, however, can be distinguished from each other by the presence of five chromosomes with two telomeric bands in each in the former while four such chromosomes are represented in the latter. The application of Giemsa C-banding method reveals a differential distribution of C-heterochromatin in the cultivars investigated thus demonstrating the active involvement of heterochromatin in intraspecific diversification of T. dioica.
Axopods have been found in the proximal region of the Malpighian tubules of two evolved blood-sucking hemipterans. They consist of a cellular expansion surrounding a sheath of regularly spaced microtubules, frequently accompanied by other cytoplasmic elements. The axopods reacted similarly to those of protozoa, retracting after 10-5 M CuSO4 treatment, but present after contact with dilute urea. These structures occurring more frequently in older and starved insects, they are assumed to be associated with the elimination of urate crystals, although participation in ion resorption could not be overlooked.
Cytological analyses were carried out to follow the nuclear events occurring during growth and differentiation of calli derived from bulb scale explants of diploid Indian squill, Urginea indica Kunth. Although bulb scale explants had a negligible level of DNA variation, the dedifferentiating calli exhibited a large variation. The meristemoids consisted of predominantly diploid cells whereas dedifferentiating calli were highly polyploid. Regeneration occurred in 8-10 week old calli but not in older cultures. Fragmentation amitosis, multiplolarity, binucleate cells etc. were characteristic of older cultures but were not noted during induction of calli despite 2, 4-D being used for establishing cultures. Regenerated plants were predominantly diploid.
Somatic chromosome morphology from root meristems of five of the Indian species of the colchicine yielding genus Iphigenia Kunth (Liliaceae), I. indica Kunth, I. magnifica Ansari et Rolla Rao, I. mysorensis Arekal et Swamy, I. pallida Baker and I. stellata Blatter, was studied. All showed a chromosome number of 2n=22. One pair of chromosomes was the longest in the complement and the rest of the pairs formed a graded series. The karyotypes were asymmetrical. The individual chromosomes were identified and idiograms constructed. The general similarity of karyotype in the species indicated that the genus is homogeneous, but the presence of gross cytological differences between them in such features as the length of the longest chromosome, arm ratio, centromere and satellite positions, total chromatin length, relative lengths, F and TF values suggests that the occurrence of chromosomal repatterning and probably also the accumulation of gene mutations contributed in the differentiation of the species. On the basis of the similarity matrix of chromosome morphological features, the relative affinities between the species were assessed.
The influence of a long-term treatment with arsenic (As2O3 250 mg/l in drinking water for 2-8 weeks) on the frequency of chromosome aberrations induced by a single treatment with ethylmethane sulfonate (200 mg/kg i. p.) was investigated in mice. A chronic exposure to arsenic alone induced no increase of chromosome breaks and exchanges in bone marrow cells and in spermatogonia. The effects of a single treatment with ethylmethane sulfonate are low and not statistically significant. Statistical analysis indicated that the increase of chromosome aberrations observed in bone marrow cells after the combined treatment could be due to an additive effect and not to a synergism between both substances.
Meiotic studies were conducted in eight male sterile triploid banana varieties. Pollen mother cells degenerated at various stages of development and in none of the varieties, divisions were observed to take place after anaphase I. Sterility was attributed to genic causes.
A detailed karyomorphological investigation of three different populations of C. corallina var. and f. corallina from West Bengal was carried out following a new pretreatment schedule. All the populations showed n=42 chromosomes but differed in karyomorphological details like karyotype, length of chromosome, number of chromosomes with secondary constrictions, confirming that minute structural alterations have taken place in course of evolution.
This work has demonstrated that water extracts of the two medicinal plants, Boerhaavia diffusa (Fam. Nytaginaceae) and Vernonia amygdalina (Fam. Compositae) contain active substances which are mitodepressive in Allium cepa. The major observable effects are decrease in the number of dividing cells and changes in chromosome structure leading to stickiness. Higher concentrations of the extract from V. amygdalina lead to nuclear disintegration and cell death and this is believed to be due to the presence of the sesquiterpene lactones, vernodalin and vernomygdin.
Nicotiana umbratica (n=23) was placed in the section Suaveolentes basing on its geographical distribution, morphology, chromosome number and karyotype. In the present investigation, N. umbratica was crossed with 18 other species from the section Suaveolentes and 13 species from other sections. External morphology and meiosis were studied in 21 of the 23 F1 hybrids obtained (including four intrasuaveolentes hybrids not involving N. umbratica) to determine the position of N. umbratica in the genus. The F1 hybrids were morphologically and cytologically uniform within the progenies. In general, the quantitative characters like plants height, leaf and flower size etc. in the F1 hybrids were intermediate between the two parents and certain qualitative characters like rosette habit, petiolate leaf, cordate leaf shape etc. were found in the F1 hybrids. Intersectional hybrids of N. umbratica showed very low pairing and intrasuaveolentes hybrids high degree of pairing, which establish the close affinity of N. umbratica with the species in Suaveolentes, thus confirming its position in this section. The intersectional hybrids showed ‘minimum’ of meiotic pairing forming zero to six bivalents with a mode of zero whereas intrasuaveolents hybrids, by and large, exhibited ‘Drosera scheme’ of pairing (where the mode of bivalents equals the number of chromosomes of the lower numbered parent). The pairing behaviour in the intrasuaveolentes hybrids could be assigned to the three categories recognised by Goodspeed (1954). Multivalents occurred frequently in the intrasectional hybrids indicating the inter- and intragenomic homologies of the parental species. The occurrence of multivalents, heteromorphic bivalents, AI and AII bridges associated with fragments indicates the significant role played by chromosome reorganisation in the differentiation of the species of Suaveolentes. Sterility observed in the intrasectional hybrids inspite of high degree of meiotic pairing could be due to gross and cryptic structural hybridity and segregational imbalances resulting from non-homeologous crossing over, as well as genic imbalance and genes affecting male and female fertility.
Cytological studies have been made on three species of Paspalum, two of which were collected from natural populations while P. scrobiculatum is a cultivated species. P. commersonii consists of forms with diverse morphological varieties, occurring either as mesophyte or hydrophyte. P. scrobiculatum and P. orbiculare show regular meiosis with n=20 and 2n=40. In contrast, in P. commersonii which has a somatic number of 2n=60 meiosis is very irregular with total asynapsis of chromosomes. This species is probably of hybrid origin and apomictic. The results of the present cytological studies clearly indicate that variations in morphological characters and habit shown by these species are correlated with cytological distinctness. Therefore these three taxa deserve separate specific rank as suggested by Bor (1960).
Breeding behaviour of any taxon is equally dependent on the cytogenetical nature and recombination pattern of both hereditary track. A complete analysis of cytogenetic behaviour must involve both sexes. From the study of male (PMC) meiosis of autotetraploid Trigonella, it has been concluded that it is quite regular and pollen fertility is also very high. To find out the meiotic behaviour on female side, MMC meiosis was studied in all the four genotypes of Trigonella. MMC meiosis was studied at metaphase I, anaphase I and telophase II. Chiasma frequency was equal during both types of meiosis. At anaphase I and telophase II, 100% normal behaviour was observed. Thus it has been found that megasporogenesis is as regular as microsporogenesis. Hence it has been concluded that there are some factors, other than meiotic anomalies, that are responsible for poor seed fertility in autotetraploid fenugreek.
Different doses of TEPA administered to newly emerged or 24 hour old weevils by fumigation method have shown various abnormalities in spermatocyte chromosomes after different time intervals. Most of the effects of this alkylating chemosterilant have been found to be gross or physiological effects involving all the chromosomes of a nucleus, like stickiness, stretching, unequal segregation, clumping etc. Only at few stages with high doses of TEPA, individual chromosomes were affected showing anomalies like bridges and laggards etc. 2-3μl TEPA also showed coiling of sperms. It is assumed that TEPA has a non-delayed (driect) type of effect which kills some sperms and incapacitates others by making them abnormal and nonmotile. The mode of action has been discussed.
Five taxa i.e. Sesbania aculeata ‘IL 2264’, S. sesban var. ‘bicolor’, S. macrocarpa ‘IL 1535’ and ‘IL 89’ and S. grandiflora ‘IL 211’ were studied for their mitotic complement. Out of these, first three taxa were diploid 2n=2x=12 and the other two taxa were tetraploid with 2n=4x=24 chromosomes in their mitotic complements. The karyotypic formula was found to be 4V+4L+4J in S. aculeata ‘IL 2264’, 6V+6L in S. sesban var. ‘sesban’ and S. macrocarpa ‘IL 1535’, 12V+12L in S. macrocarpa ‘IL 89’ and 6V+18L in S. grandiflora ‘IL 211’. The nucleolar organisers were in the form of satellites located on short arm of fifth set of chromosomes. No correlation was found between the number of nucleolar organising chromosomes and grade of polyploidy of different taxa, while six chromosomes (three homologous pairs) were found to be with nucleolar organisers in diploid species S. aculeata. Their number was found to be only two in other diploid taxa studied presently i.e. S. sesban var. ‘bicolor’ and diploid cytotype S. macrocarpa ‘IL 1535’. In tetraploid taxa i.e. S. macrocarpa ‘IL 89’ and S. grandifiora ‘IL 211’, the number of nucleolar organising chromosomes was four.
Out of the twelve taxa representing five species of the genus Sesbania, two varieties of S. aculeata, three varieties of S. sesban, three vaieties of S. macrocarpa and one variety of S. exasperata were found to be diploid with 2n=12 chromosomes, whereas one variety of S. macrocarpa and two varieties of S. grandtflora were found to be tetraploid with 2n=24 chromosomes. The diploid taxa showed regular formation of six bivalents and tetraploid taxa showed the occurrence of twelve bivalents at meiotic metaphase-I except in S. macrocarpa ‘IL 1535’ (diploid) and ‘IL 89’ (tetraploid) in which two per cent cells show an early disjunctional bivalent and/or two univalents. The subsequent stages of meiosis were quite normal resulting into 85.0 to 99.0 per cent pollen stainability. The minimum number of ring bivalents per cell (3.32) was found in S. macrocarpa ‘IL 1537’ and maximum (5.42) was recorded in S. macrocarpa ‘IL 1536’ in case of diploid taxa. The average number of ring bivalent per cell in tetraploid taxa varied from 7.9 to 9.7. Chiasma frequency per cell at metaphase-I varied from 9.6 to 12.64 in diploid taxa while it varies from 21.1 to 23.8 in tetraploid taxa. On an average the number of chiasmata per bivalent varied from 1.6 in S. macrocarpa ‘IL 1537’ to 2.1 in S. macrocarpa ‘IL 1536’. The average size of stainable pollen grains varied from 24.9μ to 28.8μ in diploid taxa, whereas it was found to vary from 28.8μ to 37.2μ in tetraploid taxa. However, the average size of stainable pollen grains in tetraploid S. macrocarpa was found to be 28.8μ which in turn was comparable to the size found in the diploid taxa.
The chromosomes of Vicia hajastana were isolated from partially synchronized cell cultures. Treatment of cells with hydroxyurea (5mM) for 24h followed by colchicine (0.01%) for 16h induced the maximal frequency of mitotic synchrony. The procedure for metaphase chromosome isolation involved lysis of cells with partially digested cell walls in citrate-phosphate buffer (pH 3.0) and the separation of the released chromosomes by filtration through polycarbonate filters. Isolated chromosomes retained a morphology comparable to that observed in the intact cells.
The chromosome number of 21 species belonging to 17 genera of Scrophulariaceae from South India has been studied, of which first record of chromosome has been made in Lymnophila heterophylla, Moniera cuneifolia, Ilysanthes tenuifolia, I. oppositifolia, Micrargeria wightii and Sopulia trfda. Chromosome numbers determined in the present study range from 2n=12 to 20=80. Chromsome numbers determined in the present study and those reported previously in the family (Fedorov 1974) reveal the presence of a continuous series of basic number between n=6 to 84. The commonest basic number in the famly is n=8 and it is assumed to be the original basic number of the family. It appears that aneuploid changes of chromosome numbers produced the basic numbers of n=6, 7, 8, 9, 10, 11, 12, 13 and 14 in the early evolution of the family, after which polyploid and dibasic amphidiploid gave rise to the higher basic numbers (n=17 to n=84) now found in the family. Karyotypes in the family also show differences in absolute chromosome size indicating changes in nuclear DNA in evolution. The meiotic chromosome number studied in 17 species is in confirmation with the mitotic chromosomes. The presence of mutivalents and quadrivalents along with bivalents and the presence of anaphasic laggards and bridges and triplar anaphases show evidences in support of the aneuploid and polyploid nature of the species.
Chromosome morphology of six Chlorophytum species reveal symmetrical karyotypes in C. laxum (2n=16) and asymmetrical in C. glaucum and C. orchidastrum (2n=42). Remaining three species, viz. C. tuberosum, C. attenuatum (2n=16) and C. comosum (2n=28) appear to be intermediate in the karyotype symmetry. In C. attenuatum and C. orchidastrum two pairs of SAT chromosomes with variations in their sequence numbers and arm ratios have been observed, whereas in rest of the species only one SAT pair could be observed. Tentative basic chromosome number for the genus has been suggested to be x=8 and 7, possibly derived as secondary number from x=4. Role of polyploidy in the speciation process, centre of origin and geographical distribution in relation to karyomorphology have been discussed.
Karyotypes from six species of genus Mikania were studied utilizing root tip metaphase mitoses. Two species were diploid with 2n=36, M. cordifolia was diploid with 2n=34, M. laevigata, was diploid with 2n=38, M. micrantha and M. viminea were tetraploid with 2n=72 and 2n=68, respectively. Five out of the six species analysed had one pair of a comparatively long chromosome with a secondary constriction in the long arms, and one species (M. micrantha) had two pairs of such long chromosomes. The basic chromosome number of this genus is 18, and we suggest that there is an evolutionary trend towards formation of aneuploid series and polyploidy.
Various chromosomal variants like double trisomics, tetratrisomic, hypo- and hyper-triploids as well as hypo-and hyper-tetraploids isolated in pearl millet (2n=14) were studied for their origin, cytomorphology and fertility. These aneuploids were distinguishable from their diploid sibs by their reduced plant height, leaf length, width, panicles length and girth and a high degree of sterility. The cytological investigation reveals the involvement of both longer extra chromosomes in first double trisomic whereas in second trisomic at least one extra chromosome was the shorter one. In tetra-trisomic plant 40% PMCs occurred with a chain or ring of 4 chromosomes along with 1III+ 5II at diakinesis and MI. In hypotriploid (19-chromosomes) plant, more number of univalents/cell were recorded while hypertriploid (22-chromosomes) carried more number of trivalents at AI as compared to other categories. Aneuploids with 27-, 29- and 30-chromosomes were isolated with a low frequency in the progenies of induced tetraploids in C2 generation. These aneuploids were apparently recovered through transmission of aneuploid egg cells having different chromosome numbers. From this study some inferences have been drawn regarding the genomic structure of pearl millet and the probable cause of “preferential pairing” noted in specific aneuploids has also been discussed.
The effect of environment on pairing of chromosomes, chiasma frequency and chromosome associations at diakinesis and metaphase I was studied in a desynaptic double trisomic pearl millet. It was observed that during the periods when the day temperatures were low there was enhanced formation of trivalents and ring bivalents with concommitant increase in chiasma frequency. There was reduction in the frequency of chiasmata, trivalents and ring bivalents in the material analysed druring high temperature conditions. The difference in the expression of desynapsis in double trisomic during the period of analysis can be ascribed to the varying environmental conditions.
Fifty eight diploid varieties of cultivated apple (Malus pumila Mill.) having 2n=34 have been recovered from different orchards of Kashmir valley. Data on chromosome pairing reveal that meiosis is normal in most of these. Nevertheless, such anomalies as precocious or delayed disjunction of some bivalents, occurrence of secondary associations, heteromorphic bivalents and univalents, chromosome lagging and fragmentation, formation of micronuclei and unequal anaphasic segregation are frequent in some varieties and provide evidence of their gybrid nature. These observations also throw some light on the controversial problem of the base number of apple.
An autotetraploid grain Sorghum plant was located in the hybrid progeny of BD 569×IS 2695 at 40 Krad dose of gamma irradiation in X1 generation. Decrease in plant height, increased size of spikelets, glumes, anthers, receptive prominent stigmas and poor seed set were characteristic features of the tetraploid plant. Pachytene studies revealed exchanges both in hetero and euchromatic regions Average number of chromosomes involved in quadrivalent formation ranged from 30% to 41.74%. Abnormal spindle formation at metaphase, irregular segregation of chromosomes at anaphase were partly responsible for increased pollen sterility and poor seed set percent.
The relative 4C nuclear DNA content in arbitrary units, in 16 different diploid (2n=14) species and varieties and two tetraploid (2n=28) species of Hordeum has been analysed with the aid of in situ Feulgen microphotometry with two wavelength method. In all the diploids, more or less same amount of DNA has been recorded and it is nearly double for the tetraploids. It has been suggested that the evolution of species and varieties of Hordeum has not been associated with marked differences in DNA content. This constancy in a widely distributed and cultivated genus reflects a strong selective advantage of this feature.
The morphological behavior of cell nuclei, mitochondria and mitochondrial nuclei during sporulation in Physarum polycephalum was investigated using light and electron microscopy. The plasmodia which reactivated from sclerotia on non-nutrient agar plates preferentially entered into sporulation. A night vision camera and time lapse VTR were available to monitor morphological changes and determine the exact time course. Sporulation processes were classified into six stages, by morphological characteristics. The initial event of sporulation was characterized by the formation of many protoplasmic knobs along plasmodium strands (protoplasmic balling stage). A papilla was projected from the apical region of each protoplasmic knob, elongated and changed to form a stalk (stalk elongation stage). The apical part of the stalk then began to expand until it reached a maximum point of stalk elongation, thereafter differentiating into the head of the sporangium (head expanding stage). After a stage without morphological changes (resting stage), the color of the sporangial head gradually changed from pale yellow to black (head blackening stage). After full blackening of the sporangial head, sporangia were completed (mature stage). 4'6-diamidino-2-phenylindole (DAPI) epifluorescence microspectrophotometry showed that the cell nuclear DNA content in sclerotia and starved plasmodia before the resting stage was the same as that in somatic diploid G2 phase nuclei. Only a single somatic nuclear division occurred at mid-resting stage. Meiotic DNA synthesis then occurred during the late resting and head blackening stages, when cytoplasmic cleavages occurred. After DNA synthesis, cell nuclei persisted in a long G2 phase of about one day and stopped at meiotic prophase I. In sclerotia and starved plasmodia, mitochondria were spherical or oval and contained one electron-dense mitochondrial nucleus (mtnucleus). Mitochondria and mt-nucleus became smaller in size in starved plasmodia. The DNA content per mitochondrial nucleus at that time was reduced by half as compared with that at the early starved plasmodium stage. Dumbbell-shaped mitochondria appeared during the resting stage; these had two mt-nuclei, each located discretely at either side of the dumbbell-shaped mitochondrion. Mitochondria containing 3-6 nuclei were also observed, at low frequency; multinucleated mitochondria persisted up to meiotic prophase I. The mitochondria in amoebae which originated from spores contained only one mt-nucleus. These results indicate that mitochondrial nuclear fusion occurs at some stage between spore germination and the amoeba stage, following mitochondrial fusion at the resting stage of sporulation in Physarum polycephalum.
Plants regenerated from callus cultures of diploid Urginea indica Kunth., Indian squill, showed variability in both chromosome number and morphology. In addition to diploids, regenerants included tetraploid, aneuploid and mosaic plants. Structurally altered chromosomes were detected in diploids as well as tetraploids. Structural alterations involved mainly the nucleolar chromosomes.
Male meiosis of E. clandestina has indicated presence of seventeen bivalents at metaphase I, and segregation of 17: 17 chromosome at anaphase I and II, followed by normal pollen and seed fertility. This indicates that E. clandestina possesses a new gametic chromosome number (x=17). This basic chromosome number (x=17) has not been recorded in the genus Euphorbia, so far. In the present report, the probable origin of the new basic chromosome number has been interpreted in the light of relevant literature.
Embryogenic callus cultures and plant regeneration were obtained from cultured hypocotyl explants of Papaver somniferum L. (opium poppy). The cytological analysis showed chromosome abnormalities in embryogenic cultures, however, plants regenerated from them were uniformly diploid with 2n=22 and matched the plants grown from seeds in karyotypic details, meiotic behaviour, pollen stainability and seed set. The uniformity in regenerated plants seems to be on account of preferential selection and regeneration only from normal diploid cells.
The effects of CIPC, or isopropyl N-(3-chlorophenyl) carbamate, on nucleolar activity of Vicia faba root tip cells were examined. The nucleoli of CIPC-treated cells were smaller, frequetly had segregated contents, much lower RNA contents, and reduced biosynthesis of RNA by two-thirds. These facts are discussed in conjunction with the hypothesis that the mode of action of CIPC is somehow related to inhibition of gene derepression at the molecular level.
Treatment of flower buds of Chlorophytum amaniense with different concentrations of dye industry waste water resulted in the production of high percentage of abonormal PMCs. The abnormalities observed included stickiness of chromosomes, laggards, bridges, fragments and micronulcei. The higher frequency of stickiness observed is apparently responsible for some of the above abnormalities. It is concluded that dye industry waste water with rich amounts of heavy metals act as potential mutagens.
The meiotic behaviour of 7 X-ray induced weakly fertile desynaptic mutants of Pisum sativum was studied with regard to the number of univalents and the number of microspores per pollen mother cell. The genotypes can be subdivided into two groups according to the degree of desynapsis. If we consider the high degree of meiotic irregularities in microsporogenesis, an extremely low seed production should be expected in the first group whereas the genotypes of the second group should be completely sterile. Both groups, however, produce essentially more seeds than expected. The dfindings demonstrate that the 7 ds-genes studied influence microsporogenesis much stronger than macrosporogenesis.
Trispecific cross between F1 of (Atylosia albicans×Atylosia scarabaeoides) and Atylosia cajanifolia was successful and a semifertile F1 hybrid was obtained. Parental materials having different morphological traits and growth habits in the genus Atylosia have shown close affinity in their chromosome complements as evidenced by the formation of high degree of bivalents during meiotic cell division. Possibilities for developing better plant types through hybridization for rangeland forage production have been explored.
Two autotriploids were isolated in the F1 hybrid progeny of Ms×Cluster and Ms×Santaka. Triploids exhibited increased vigour in plant height and spread with no marked change in leaf and flower size. Fruits were few in number and small in size with very poor seed set. Trivalents ranged in number from 3-7 per cell. High frequency of univalents and bivalents along with a few trivalents and occasional presence of hexavalents and qudrivalents indicated that the plants are segmental autotriploids with some structural alterations. The triploids might have originated by the fusion of the unreduced gametes produced in the male sterile line with normal male gametes. The difference observed in the two triploids in cytomorphological features can be ascribed to the absence of uniform genetic background.
Second division restitution was found to be the cause of high fertility observed in an interspecific triploid hybrid in Arachis (cv. Co-1×A. chacoense Krap. et Greg. nom. nud., 2n=3x=30). Precocious centrometic division followed by equational division led to the production of unreduced gametes. Occurrence of a few multivalents at diakinesis indicated intergenomic exchange prior to SDR. Selfed progeny of the triploid predominantly contained hexaploids along with a few pentaploid, tetraploid and aneuploid segregants. Breeding implications of this fertile triploid in reducing the number of generations needed for gene-introgression from wild specied into cultivars were discussed.
Histochemical localization of two enzymes in cassava callus showing root and shootlike structures was carried out. Localization of peroxidase by the benzidine reaction showed granules in cells next to meristemoids, around root initials and tracheids and at the callus margin. They were also found close to the provascular region of the shootlike structure and parenchyma cells of its head. Phosphatase localization using the lead sulfide procedure showed black deposits in cells around the meristemoids and meristematic core of the stalk in the shootlike structure and in the vicinity of its base. They occur also in some cortical cells of the root and marginal cells of the callus.
Leaves of Ranunculus glacialis, harvested at 2600 m-2800 m altitude in the Alps, contain numerous peroxisomes in close association with mitochondria and plastids. Cytochemical staining for catalase by means of the DAB-reaction is found in peroxisomes only, while staining for peroxidase is also found in the tonoplast membrane. Phloem parenchym cells in the leaves store considerable amounts of lipids. It is conceivable, that during the short growing season under stress conditions peroxisomes participate in the break-down of the energy source “lipid”. Abbreviations: DAB, 3, 3-diaminobenzidine RuBP, ribulose-1, 5-bisphosphate
Less balanced diets are known to induce higher sister chromatid exchange (SCE) frequency in rats. The SCE frequency of various diet rat groups correlated well with the degree of variation among the fasting plasma profile equivalent (FPPE) values of amino acids in their diets. To narrow the differences among the FPPE values of essential amino acids, three limiting amino acids, lysine, tryptophan, threonine, were added to the regular diet (Diet P) and to a less balanced diet, Diet G. The amounts of amino acid supplemented were calculated based on the FPPE concept. It was found that the addition of the three amino acids could reduce SCE frequency of those rats treated with a mutagen, cyclophosphamide (CP), especially at a higher dosage of CP.
Cell populations in exothecium and endothecium of Allium cepa L. pollen sacs were studied throughout the time covering the development of meiosis in the accompanying pollen mother cells (PMCs). In both layers of the anther most of the cell population is already differentiated in G0, with a 2C DNA content, at early meiotic prophase. However, there is a subpopulation of cells, around 3.5% of the whole population which is still slowly replicating in exothecium during the whole PMCs meiosis, without reaching the 4C DNA content. In endothecium, there is also a minor subpopulation cycling throughout the whole development of the meiotic stages. The frequency of cells replicating reaches its maximum (3.8%) at pachytene. Such peak is followed by a maxium in mitotic index (3.6%) at diplotene-diakinesis-metaphase I, suggesting the existence of certain synchrony in such endothecial cycling population.
Karyotype analysis in 12 strains of Cicer arietinum L. shows gross morphological homogeneity. Somatic chromosome number 2n=16 is constant for all the strains. The chromosomes are small to medium in size with median to submedian primary constrictions. Secondary constrictions are present in one to three pairs of chromosomes. Supernumerary constriction has been located in a pair of chromosomes in a single strain. The characteristic feature in the karyotype of all the strains is the presence of marker chromosomes which are comparatively longer and always with secondary constrictions. Uniformity has also been noted so far as the total chromosome length and volume are concerned, though their range is quite wide. These characters of the chromosome morphology may be utilised as criteria for identifying different strains. Meiotic study reveals regular eight bivalents. However, certain irregularities are present in some of the strains.
Karyotypes of 12 species of North American cyprinid fish from the southern United States are documented. All 12 have a diploid chromosome number of 50; the estimated arm numbers of the species range from 88 to 96. Sex chromosomes were not detected in those taxa where specimens of both sexes were assayed. All available karyotypic data on the North American cyprinids indicate considerable conservatism in standard karyotypes within the group. The true extent of karyotypic variation among North American minnow species, however, will be known only after serially banded karyotypes are rigorously examined.