Colchicine treatments induced three different types of c-metaphase cells; type 1-typical c-metaphase with all chromosomes randomly scattered all over the cell; type 2-c-metaphase with chromosomes grouped in two groups; type 3-c-metaphases with all chromosomes clumped in a single compact group. The frequencies of the different types of c-metaphase cells observed varied with the concentration of the colchicine solution and with the duration of treatments. For the same treatment no significant difference was detected between genotypes with two (diploid rye and hexaploid wheat) or more (tetraploid rye) chromosome complements of each genome. Comparisons between the behaviour of these genotypes with genotypes with only one chromosome complement of each genome present (in wheat-rye F1 hybrids) showed however a significant difference. It is therefore suggested that the induction of distinct types of c-metaphases is related to genome organization in the cell which emmerges probably because colchicine treatments besides affecting spindle microtubules during late prophase are also affecting the integrity of the nuclear membrane or of its attachent to the chromatin during late interphase.
In pearl millet (Pennisetum americanum (L.) Leeke, n=7), in the selfed progenies of a line L. S. 326-3, a mutant with plasmodial sporocyte (syncyte) formation, chromatin disintegration, desynapsis and centromere breakage was identified and its cytogenetic features were studied. Two to 24-nucleate syncytes were formed due to suppression of cytokinesis during premeiotic mitoses. In syncytes, chromatin degeneration occurred from prepachytene to telophase I stages, thereafter only masses of empty cytoplasm were found. In uninucleate PMCs, chromatin extruded in prepachytene stages in some, degenerated upto diakinesis in several, and either bivalents or univalents (ranging from 1 to 14) were formed in the rest. Centric misdivision leading to telocentric chromosomes (ranging from 2 to 14 per cell) occurred in a proportion of PMCs at anaphase I. There was high sterility of male and female gametes. F2 and test cross progenies of mutant X normal segregated respectively to 9:3:3:1 and 1:1:1:1 ratios of (i) completely normal meiotic behaviour, (ii) syncyte formation and chromatin disintegration but without desynapsis and centromere breakage, (iii) desynapsis and centromere breakage but without syncyte formation and chromatin disintegration and (iv) meiotic behaviour like the original mutant. Crosses between the recombinants (ii) and (iii) above yielded progeny with completely normal cytological behaviour. The original mutant thus was a double mutant. The genes were designated as snd (syncyte formation and chromatin disintegration) and ds cb (desynapsis and centromere breakage).
A study of meiosis in the PMC's of five populations of C. diffusa (2n=2x=30) belonging to three sub-species, diffusa diffusa, diffusa aquatica and diffusa montana, revealed varying degrees of chromosomal associations suggesting the presence of interchange complexes in these populations. Fertility estimates showed a high proportion of infertile microspores and concomitant reduction in seed set. These could be traced, at least in part, to the presence of interchange heterozygotes in these populations.
A study of meiosis in the PMC's of three populations of Commelina erecta (2n=4x=60) belonging to two subspecies, erecta and maritima showed regular bivalent formation in the former and irregular meiosis characterised by varying numbers of univalents, bivalents and laggards in the latter. Subspecies erecta produced ample and viable seeds which showed 61 and 65% germination respectively for the two populations studied while subsp. maritima gave 100% of infertile pollen and consequently no seed-set. The infertility of the pollens here was attributed to irregular chromosome pairing behaviour observed in meiosis.
In Gelidiella acerosa from Ervadi the diploid chromosome number 2n=12, with haploid number n=6 is discernible. Bivalents were observed in the dividing tetraspore mother cells. In situ germination of tetraspore mother cells dircetly by mitotic division points to apomeiotic propagation in this species. The occurrence of two cytotypes in the species suggests the existence of a polyploid series.
Structural aberrations of chromosomes of 150-day-old cultured cells of barley were examined by karyotypic analysis. Minor and major rearrangements were detected in chromosomes; all the metaphase cells analysed from the culture revealed the presence of aberrant chromosomes in them. Analysis of cultured diploid karyotypes showed the inclusion of 44% structurally aberrated chromosomes. It was observed that certain new karyotypes were originated due to chromosomal rearrangements, while the ploidy level remained same as that of original plant. Tetraploid cells carried greater frequency of aberrant chromosomes that diploid cells. Aneuploid cells of the culture also carried 48% structurally altered chromosomes in them. The significance of this study is discussed.
Trypsin G-banding of chromosomes from North American cyprinid fishes was used to address phylogenetic problems within the group and to demonstrate the occurrence of G-bands which are not differentially rich in AT DNA base pairs. G-band homology of the long arm of the F', C', and E' NOR chromosomes found among six North American cyprinid species, in concert with a hypothesis of species relationships based on morphology, suggests that a NOR situated terminally on the largest chromosome in the complement may represent the plesio-morphic NOR character state within the large “Notropis”-like shiner assemblage. Outgroup comparison suggests that this chromosome may also represent a synapomorphy for the same lineage. Evidence exists which suggests that the F' NOR is ancestral and that the C' and E' NORs are derived. The occurrence in cyprinids of trypsin-induced G-bands which are not differentially rich in AT-/GC-DNA base pairs may indicate that the evolution of trypsin-induced G-bands preceded the evolution of differential AT-/GC-richness. The use of trypsin G-banding in cyprinids in expected to permit the identification of previously cryptic chromosomal rearrangements both within and among species.
The cytological effects on the pollen mother cells of Lathyrus sativus grown after seed treatment with different concentrations of two pesticides (rogor and bavistin) and an antibiotic (streptomycin) indicated that all the three chemicals were capable of inducing cytological disturbances. The dominant types of aberrations included: stickiness, univalents and multivalents, laggards, fragments and bridges. Besides these, some cases of cytomixis were also recorded. Streptomycin proved to be more efficaceous followed by rogor and bavistin. Thus, the genotoxic effect of these chemicals is established.
Detailed karyomorphology of five morphotypes of taro is reported. Although in gross karyomorphology Morphotypes I-IV were similar, with respect to finer details of morphology of certain individual chromosomes, recognisable difference was noticed between and among them. Between Morphotypes I-IV and Morphotype V there was striking difference in karyomorphology, particularly in the frequency of m-and st-type chromosomes. The degree of karyotype difference noticed is pointed out to shed light on the possible role of intraspecific karyotype changes and its bearing on the plant morphological difference evident in the species complex. The gross karyomorphological difference noticed between Morphotype V and the others is pointed out to be of taxonomic implication.
A procedure for in situ hybridization of nucleic acids was applied in order to detect chromosomal DNA sequences coding for leghemoglobin in Vicia faba L. genome. Tritiated cDNA from Lupinus lutus L. was used as a probe. Three different site of hybridization localized in three different chromosomes (I, II and IV) were found.
The cytology, reproductive behavior and fertility of seven different Paspalum species were studied to determine how they might be used in an interspecific hybridization program. Paspalum palustre Mez and P. bertonii Hack. were diploids with 2n=2x=20 chromosomes. Paspalum dedeccae Quarín; P. denticulatum Trin., and one P. distichum L. accession were tetraploids with 2n=4x=40 chromosomes. Another P. distichum accession, P. inaequivalve Raddi, and P. ramboi Barreto were hexaploids with 60 chromosomes. Meiosis was regular with primarily bivalent pairing in P. palustre, P. bertonii, tetraploid P. distichum, P. inaequivalve and P. ramboi. Paspalum dedeccae, two P. denticulatum accessions, and hexaploid P. distichum were meiotically irregular with univalent, bivalent and multivalent (primarily quadrivalent) associations at metaphase I. Megasporogenesis and embryo sac development in P. palustre, P. bertonii, and P. inaequivalve indicated sexual reproduction. Paspalum palustre and P. bertonii were self-incompatible and did not produce self-pollinated seed but P. inaequivalve was self-compatible. Paspalum dedeccae, P. denticulatum, P. distichum, and P. ramboi all reproduced by aposporous apomixis.
The Q-banded karyotype of pearl millet was successfully demonstrated. The banding patterns at different stages were analysed and polymorphism in banding pattern of homologues of chromosomes 1, 3, 4 and 6 was observed. They differed in having bands of unequal size or different band positions. The chromosomes showed Q-bands only in telomeric and centromeric regions and intercalary bands were absent.
Karyomorphological analyses of three male sterile lines of Pennisetum americanum, their maintainers, two inbreds and two hybrids, which are morphologically distinct showed variations in their karyotypes. The three male sterile lines 732 A, 834 A and 843 A revealed differences in karyomorphology. Comparison of karyotypes of male steriles with their 'maintainers broughtout differences between the two. The two inbreds (PT 1921 and PT 3095) showed contrasting karyotypes whereas the two hybrids (UCH 11 and ABH 66) derived from a common female parent showed minor differences. The above results were confirmed using karyograph analysis, which led to infer that morphological closeness (male steriles and maintainers) is accompanied by restricted karyotypic variations and recognisable morphological difference follows a marked karyotypic difference.
Karyotypes from five species of the genus Vernonia were studied utilizing root tip mitotic metaphases. Vernonia nudiflora and V. polyanthes were tetraploid with 2n=34 (X=17); V. flexuosa and V. simplex were tetraploid with 2n=40 (X=10). V. polyphylla with 2n=64 may be an allotetraploid with X=16 or an autoplolyploid with X=8, that became fertile by diploidization. The basic chromosome numbers are a series of X=7, 8, 9, 10, 15, 16, 17 and 19. We suggest that in Vernonia there is an evolutionary trend towards formation of aneuploid series and polyploidy.
The chromosome numbers of 178 plants from triploid × diploid crosses of maize (Zea mays L.) were determined and 171 plants were hyperdiploids with 2n=21 to 2n=28. The karyotype analysis of the hyperdiploid plants have shown that the chromsomes 1, 3, 9 and 10 were transmitted through the female gamete of the triploid in relatively higher frequency, whereas chromosomes 5 and 8 were transmitted less and chromsome 6 was transmitted the least. The longer chromosomes were not selectively transmitted and hence, it disagrees with the proposition of Einset (1943) that in maize the transmission of extra chromosome is a function of the length of that chromosome.
The most interesting and peculiar feature of mature pollen grains in S. speciosa is the presence of intine wall ingrowths and membranous labyrinths in the vegetative cell at the aperture region. The presence of mitochondria in the vicinity of these wall ingrowths makes the vegetative cell to behave as a transfer cell. The second important feature is the occurrence in the vegetative cytoplasm of large quantity of stacked endoplasmic reticulum, thus the vege-tative cell functions as storage organ. The third important feature is the presence of plastids in the vegetative cell cytoplasm whereas the generative cell cytoplasm is devoid of these, thus supporting the maternal inheritance of plastids.
In a certain clone of S. spontaneum L. from Bhagalpur, about 80% of anthers were found to have n=27. In the remaining 20% anthers, PMCs with both n=27 and 24 were observed coincidently. The frequency of former was about 85% and of latter 15%. Few PMCs with n=27 did exhibit two laggard chromosomes at anaphase-I. It is proposed that n=24 condition was derived from n=27 due to Robertsonian translocations in the basic number 9, to be followed by triploidy of 9 as well as of 8 forms.
Detailed cytological studies have been made on Coix gigantea, which occurs as a pest in the paddy fields of South India. This species is mainly distinguishable by the size and shape of leaves which are rather long and narrow, resembling paddy leaves (and so this species may be considered to exhibit mimicry). The chromosome numbers of n=6 and 2n=12, have not been previously reported in this genus. This species is unique in cytological features also, as it shows distintly larger chromosomes. This is a highly stabilized species which shows perfectly regular meiosis with typical diploid behaviour.
A light and electron microscopy examination of the pairing behavior of the mouse oocytes carrying paracentric inversions In (X) 1H, In (1) Rk, and In (5) 2Rk revealed loop formation, synaptic adjustment and significant asynapsis of the inversion segments.
Dicotyledonous plants usually found in habitats with more nitrogen were showing fewer, not more, chloroplasts in their guard cells of stomata, on average. Obviously, this effect is not one of nitrogen as a nutrient.-Ammonium sulfate added to nitrophilous plants with low chloroplast numbers increased these numbers, whereas nitrophilous plants with high numbers and non-nitrophilous plants with any numbers did not react. Some species need more nitrogen for reproducing their chloroplasts in guard cells to the specific level than do other species.
The paper reports the occurrence of diploid cytotype in natural populations of Physalis L. During floristic survey at different regions, we repeatedly collected a diploid cytotype which was previously included under P. minima L. Morphological and crossability studies revealed that they are reproductively isolated and genetically distinct from the other tetraploid taxa. Attempts have been made to determine its correct taxonomic status. This taxon resembles P. pubescens L. in several cytomorphological features. In addition, crosses between these two taxa produced normal fertile hybrids (F1), with regular meiosis and set fruits and seeds spontaneously. These features indicate that the two taxa are genetically uniform and together seem to constitute a single biological species-Physalis pubescens L. Future floras of India, therefore be amended accordingly and list P. pubsecens L.
Buffer and water extracted proteins were quantitatively measured by Bradford method (1976) for 18 taxa of five species of genus Lotus. The somatic chromosome number, chromosome length, and chromosome arm ratio were determined. The effect of supernumerary chromosome on protein percentage and an interpretation for the variation in protein quantities between the different taxa of each species were discussed.
The paper evaluates the degree of polyploidy in the leguminous genus Crotalaria, discusses its role in intrageneric evolution, impact on plant fertility and significance in solving the problem of base number of the genus.
The chromosome analysis and in situ DNA estimation of Ornithogalum thyrsoides (2n=12) in vitro revealed the maintenance of normal karyotype in leaf and bulb explants, in 300 days old calli and in roots and shoots of regenerated plants.
The chromosomal break points were reduced (from 0.31/cell to 0.12) significantly when essential oil of A. graveolens was administered to mice of Lacca strain intoxicated with carbontetrachloride. This shows the anticlastogenic effect of A. graveolens.
General pattern of the process of mitotic division was studied in thirty seven pennate diatoms. Even though normal mitotic division takes place in diatoms it resembles with that of animal cell division in having ring-like arrangement of metaphase chromosomes and cell furrow cleavage of cytoplasm. Most of the diatoms follow Mac Donald-Pfitzers hypothesis of size reduction after cell division in each generation.