The mesophyll cell section of an unimbibed primary leaf appeared with a large number of protein bodies, a few mitochondria and 2 to 3 proplastids. The proplastids were identified as membrane bound structures with irregular shape and within the stroma appearance of one or two electron dense bodies and small portions of membrane (prothylakoids). The membranebound mitochondria can be distinguished from the proplastids by their small more regular shape and their electron transparent appearence at the centre. Cristae can be identified in a few of them. A close association between proplastids and mitochondria was noted. The starch grains were first detected in the proplastids from 12h imbibed leaves. A peak number of starch grains per plastid section was noted after 36h, after which this value fell. The protein bodies in the cell section were reduced in number accompanied by the development of starch grains in the proplastid section after 24h of imbibition. Proplastids became spherical and the most part of the stroma was covered with a number of starch grains in the mesophyll cells after 36h of imbibition. The most characteristic feature of this stage was the occurrence of plastid as well as cell division. During the next 2days the number of starch grains per plastid section fell although the number of grains per cell section remained fairly constant. The increase in the number of plastid sections per cell section indicated that plastid divisions occurred more rapidly than cell divisions during the first 4 days of dark growth. Therefore, this report identifies the proplastid in the dry embryonic leaf and the commencement of plastid division accompained by cell division after 36 h of imbibition. The development of etioplast from proplastid is characterized by the increase in number of starch grains in the stroma and the reduction of the number of protein bodies in the cytoplasm.
An interspecific hybridization was carried out between two edible Solanum species (S. aethiopicum and S. gilo) whith the aim of developing new plant types combining the parents' attributes. The F1 interspecific hybrid flowered, fruited and seeded normally. Meiosis was mostly normal although delayed separation and lagging chromosomes were observed among a few F1 PMCs. The pollen showed a high level of viability as determined by acetocarmine staining. The breeding implications of this successful hybridization was discussed.
The cytological effects of the organophosphorus pesticide, Phosalone were studied on root meristems of A. cepa. Different periods of treatment were carried out using different concentrations (0.25, 0.5, 0.75 and 1.0%) of the pesticide. Subsequent Knop's recovery was done for 96 hours after treatments of upto 24 hours and 48 hours. The pesticide induced mitostatic effects on root meristem cells, the mitotic index gradually decreasing with the increase in concentration and time of treatment. Mutagenic effect was noticed with abnormalities like chromosome breakage and erosion, sticky bridges, laggrads, multipolarity, polyploidy, clumping and pycnosis. There was a slow rise in the mitotic index after recovery for 48 hours and 96 hours of 24 hours and 48 hours treatments respectively. The percentage of total chromosomal abnormalities was found to have decreased fairly in the recovery set of 96 hours of 48 hours direct treatment, the percentage of total chromosomal abnormalities was found to increase in concentrations 0.25% and 0.75% and slightly to decrease in concentrations 0.50% and 1.0% respectively. Material treated with 0.75% and 1.0% Phosalone for 48 hours, failed to show marked recovery with death of roots.
Genetic control, time of ms gene action over microsporogenesis, plant phenotype and the breeding value of a diploid (2n=20) male sterile Ageratum conyzoides are described. The male sterility is controlled by a recessive gene on a single locus. This gene acts immediately after the microspores are released from the tetrads. The floral heads of the male sterile plants are compact and their stigma protrusion is slow. This trait differentiates them from the male fertiles in which the stigma exsertion is brisk and prolific. The breeding value of this male sterility is low.
Cytological information on the non-dividing (metabolic) and dividing nuclei from tetrasporophytic thalli of Herposiphonia tenella (C. Agardh) Ambronn. is reported now for the first time. At meiosis, there is prevalency of bivalency followed subsequently by regular meiotic events. On this basis it is determined that the 2n chromosome number is 46 for this taxon. It is concluded that H. tenella is nearer to the more advanced Ceramiales in its attainment of higher chromosome number. Its affinities to other polysiphonous Ceramiales have not become clear. This would become possible when other species of this genus and those related to it become cytologically better understood.
Comparative karyomorphological analysis of 21 types belonging to nine species of Capsicum revealed conspicuous intra- as also inter-specific variations. All types had 2n=24 chromosomes though they differ in the number of SAT-chromosomes. Total length of the complement was maximum in pubescens and minimum in testiculatum. Difference in longest and shortest chromosomes of a complement was highest in pendulum. Number of homobrachial chromosomes was more in wild and semiwild species whereas in cultivated species heterobrachial chromosomes were relatively more. Overall consideration of these observations suggests relatively symmetrical karyotypes in wild and semiwild species probably due to highly restricted distribution within the narrow ranges around centre of origin. On the contrary, cultivated species cover extensive areas and wide ranges of ecological habitats, resulting in relatively asymmetrical karyotypes.
The effect of the herbicide (Garlon-4) has been studied on root mitosis of Allium cepa (v. Giza-6). It contains triclopyr as an active ingredient and its chemical formula is 3, 5, 6 trichloro-2-pyridinyloxy-acetic acid. Root tips of Allium cepa were treated with a series of concentrations, ranging from 28ppm to 38400ppm for 3, 6, 12 and 24 hours. Examination of the roots was done in permanent root tip squash preparations stained by the Feulgen technique. Garlon affects the relative duration of each mitotic stage as compared with the control. It also caused reduction in mitotic index, indicating mitotic inhibition, and increase in the frequency of abnormal mitoses, the precentages of which are highly significant, except the lowest concentration (28ppm) which had no significant effect after 6 hours and induced a statistically significant percentage of abnormal mitoses from the control after 12 hours of the treatment. The types of abnormalities induced included: chromosome stickiness, c-metaphase, canaphase, tetraploid and restitution nucleus, star metaphase, laggards, bridges, tripolar, and disturbed meta- and anaphases. Micro- and binucleate cells as well as multinucleated cells at the interphase stage were also observed. The effect of Garlon-4 on root mitosis simulates that of colchicine in the type of abnormal meta- and anaphases (c-metaphase and c-anaphase) and the induction of polyploid cells as well as accumulation of metaphases.
The requirement for Ca2+ and Ca2+ uptake were determined both at the initial step and during the phase of commitment. The onset of RNA and protein synthesis, which occurred around 12h after stimulation, were not delayed by the early 12h Ca2+ depletion. On the other hand, DNA synthesis was delayed by both early and late Ca2+ depletion. The enhancement of Ca+2 uptake was observed at each stage. We concluded that Ca2+ is required for both the stages and that Ca2+ is more necessary for the time of commitment than it is for the early phase of lymphocyte stimulation.
Meiosis is normal in control plants. Radiation induced meiotic abnormalities increased with increased exposures to gamma-rays. The chromosomal aberrations included stickiness, clumping, precocious separation, bridges, laggards etc. Pollen sterility increased with dose and was directly proportional to meiotic irregularities. The percentage frequencies of anomalies were more numerous in M1 than M2 due to genetic recovery or elimination of the defectives.
Of 1, 072 rye plants originally collected in Greece and Turkey, three plants were triploids. They were collected at two different sites in Turkey. Based on chromosome pairing, it is concluded that they are autotriploids. They likely originated from the union of an unreduced female gamete produced spontaneously with a normal male gamete.
The present investigation concerns the influence of the water extract of Cymbopogon proximus (Halfa barr) on the mitosis in roots of Vicia faba. All the used concentrations caused mitotic delay, the action of the long durations was significant. The extract also brought about significant percentage of abnormal dividing cells. The effect of the extract may be determined as pre-prophasic. The number of prophases decreased while metaphase and ana- and telophase increased. The extract induced a number of chromosomal irregularities such as stickiness, disturbacny, lagging chromosomes and bridges.
Chromosome counts for three species and two varieties of Japanese Fragaria were determined. This is the first report of the chromosomes of F. nipponica var. yakusimensis. Fragaria nipponica var. nipponica, F. nipponica var. yakusimensis, F. nipponica var. yezoensis and F. vesca were very similar in karyotype morphology, but F. iinumae showed differences from those taxa.
Comparative morphological study of plant parts and floral parts in different chromosomal races of Saccharum bengalense Retz. complex is presented. Although variation between the cytotypes is basically of quantitative nature yet some of the characters help in distinguishing diploid (2n=20), tetraploid (2n=40) and hexaploid (2n=60) cytotypes in the field. A key has been suggested for this purpose. Hairyness of lower glume of sessile spikelet helps in distinquishing diploid from diploid with one to five accessory chromosomes, it being smooth in the latter. Stomatal size did not prove a reliable character to distinguish the diploids and the polyploids. Pollen size increased with the increase in ploidy level. Seed germination percentage was low in the polyploids compared to in the diploid. An interesting observation was that the gigas effect of ploidy existed upto tetraploid level only and in the hexaploid the effect is reversed. Karyotype was studied in different cytotypes and it was of symmetrical type.
Two distinct morphological types (types I and II) each of M. hastata and M. vaginalis having a different and stable chromosome number in each type were recorded. The chromosome numbers in these plant types were 2n=28 in M. hastata-type I and 2n=80 in type II and 2n=24 in M. vaginalis-type I and 2n=52 in type II in both RTCs and PMCs. Based on the morphological and cytological observations, a hypothesis has been proposed in which 52 chromosome plants (M. vaginalis-type II) are suggested to be an allotetraploid between 2n=28 and 2n=24 chromosome plants and 2n=80 chromosome plants as an autoallohexaploid between 2n=52 and 2n=28 chromosome plants and that they may be considered as new species.
Interspecific hybrids between S. lucani and S. surattense (violet and white varieties both) were successful in forward and reciprocal directions. The crossability index between them was low, which suggests low degree of crossability relationships between hybridizing parents. Meiotic studies on parental genomes showed normal bivalents, most of which were ring shaped and chiasma frequency was high. Interspecific hybrids showed abnormal synapsis and unpaired chromosomes/chromosome parts with less staining ability. Metaphase I was characterized by the appearance of univalents, chains of three or six chromosomes, Y-shaped trivalent and rarely tetravalent association. Most PMCs contained 9 bivalents of which 5-7 were ring bivalents suggesting full homology between 7 chromosomes of S. surattense and 7 chromosomes of S. lucani, and the remaining 2 pairing partners exhibited partial homology by showing rod bivalents. Failure of synapsis in the rod bivalents could produce occasionally univalents only. Asymetrical chain made of three or six chromosomes indicated interchange of unequal segments due to heterozygosity for reciprocal translocation, in which 3 chromosomes from each parent were involved. Formation of Y-shaped trivalents was due to joint of interstitial break points. Further, occurrence of chromatid bridge with or without acentric fragments, presence of univalents, lagging and eliminated chromosomes indicated heterozygosity between parental genomes which contributed to formation of sterile pollen. However, all hybrids showed partial fertility except S. lucani×surattense var. white which was completely sterile.
A cytological study has been carried out with Vicia faba and Hordeum vulgare to examine a number of techniques for diferentially visualizing sister chromatid exchanges (SCE) using the Fluoresent-plus-Giemsa and the Feulgen procedures. Factors which affect seedling growth and BrdU uptake of growing seedlings are important for sister chromatid differentiation. A variety of steps carried out after the root tips are harvested, including fixation and staining have been shown to affect both the quality of staining and differentiation of SCE. Other important factors to be considered if this technique is to be used in mutagenicity testing are the concentration of both BrdU and FdU, and the degree of squashing of the cells to obtain good metaphase spreads for visualizing the chromosomes. Treatments such as the removal of plant shoots and cotyledons, and the application of BrdU and FdU led to reductions in mitotic indices. However, it is not recommended to eliminated FdU, since it has been shown to enhance the uptake of radioactively labelled BrdU. A concentration of 100μM BrdU was satisfactory when root tips of whole plants were treated. The variance of the mitotic index within treatments when seedlings were treated was consistently high, implying that a range of tolerance to a given treatment existed among individual plants of the same cultivar. This variance caused the results of statistical analyses to be inconclusive with respect to differences between treatments. Fixation had a significant influence on the quality of staining and a fixation time of 7 hours is suggested. Fixation should be carried out at 4°C and storage of stained root tips for up to one month in 70% ethanol does not seem to adversely affect staining. Good differential staining was obtained in Vicia and in barley by means of the Feulgen procedure, but not the FPG technique.
164 whole mounted “screw like” chromosomes of Prorocentrum triestinum were morphometrically characterized by analyzing their axial length, coil number, diameter, pitch, tilt angle, total wings length and Weibel's lambda coefficient of form. Although the respective upper regions show to be similar, quantitative differences between chromosomes were found in the lower regions. The tilt angle increased 4° each of succesive coils, then progressivelly decreasing the chromosome diameter. To stablish the karyotype of a dinoflagellate for the first time, the chromosomes were ordered either by their respectives axial lengths and lambda coefficients of form. Thus, the 32 chromosomes of the Prorocentrum triestinum karyotype could be stablished.
Cytotoxic threshold dose of three commonly used pesticides (Malathion, Metacid and Lindane) was determined using relative division and abnormality rates in meristematic cells of Allium cepa root tip by using dose-response curves populated with varied number of smaller doses. The results obtained show such dose to be 25, 20 and 50 ppm for Malathion, Metacid and Lindane respectively.
Silver staining procedure has been modified to provide a rapid means of visualising nucleoli and NORs in a range of plant tissue including callus. Unlike the situation with beet, garlic callus was found to be composed of large numbers of cells possessing stained nucleoli. The number of nucleoli per cell varied depending upon the growth medium and hormone composition used for culture. On medium promoting organogenesis and subsequent plant regeneration, the nucleolar number per cell was lower than that in callus on non-regeneration medium, and similar to that in normal root tissue. Nucleolar number is therefore a marker for regeneration in callus. No such variation was found in beet, where no marker for regeneration was found.
The cytological changes produced by magenesium sulphate were studied in root meristems of Vicia faba. Roots treated with different concentrations of magnesium sulphate showed the presence of chromosome breakage, achromatic lesions, chromosome clumping, lagging chromosomes, micronuclei etc. Spindle abnormalities leading to the formation of polyploidy and aneuploidy were also observed. Magnesium sulphate exerted mitodepressive effects in higher concentrations. The present studies have revealed the cytostatic and clastogenic properties of magnesium sulphate.
The present communication puts on record the chromosome behaviour during reduction division in the pollen mother cells of 21 diploid species of Astragalus, growing wild in the Kashmir Himalaya. In all these species meiosis was by and large normal. The occasional segregational anomalies, observed in a few species, have also been described. The low frequency of PMCs with these anomalies indicate that these are not due to any genetic change but can be explained on the basis of occasional segregational errors only. It has been pointed out that there is a positive correlation between the recombination indices and the total chromatin lengths in these species.
Cytology of three species of Cordyline and ten of Dracaena is reported from South India. The gametic numbers observed in species of Cordyline is n=19 and in Dracaena are n=18, 19 and 20, of which n=19 predominated. Chromosome data show that both the genera have similar basic chromosome consitution (x=18, 19, 20) and small sized chromosomes. The x=20 in Dracaena is postulated to be the earlier evolved one by polyploidy from a possible x=10 primary condition. Polyploidy and aneuploidy appear to have played significant role in speciation and evolution in the genus. Systematic relationships of the genera is considered. Hutchinson's treatment of Cordyline and Dracaena along with Sansevieria and Cohnia in the same tribe (Dracaeneae) is pointed out to be justifiable on karyological grounds. But this tribe appears to have very little cytological likeness with the other tribes of Hutchinson's Agavaceae, and this supports the suggested removal of Dracaeneae from the Agavaceae.
The effects of mercuric chloride (HgCl2) and mercurous chloride (Hg2Cl2) as water pollutants, were tested on submerged Hydrilla verticillata Rich. Various concentrations of these compounds showed a much lower mitotic index and higher cytological aberrations than control. Growth parameters like root-length and shoot-length, fresh weight and dry weight of biomass to control. Both compounds showed inhibitiory effects in all the cases. After all it was noted that all the parameters were time and dose responsive.
The present paper deals with the cytology of Gracilaria corticata J. Ag. var. corticata J. Ag. collected from Guhagar, India. The chromosome number determined is n=7 which is the first record in the species.
Karyological studies were made in 5 cultivars of N. pseudonarcissus; ‘Telamonius Plenus’ (2n=14, 28), ‘Golden Spur’ (2n=21), ‘Emperor’ (2n=21), ‘Empress’ (2n=21+1B) and ‘Beersheba’ (2n=29). The basic set of 7 chromsomes bears broad similarity among these cultivars. Of the 6 long elements, 4 are submetacentric while the other 2 range between submetacentric and acrocentric. The short chromosome is submetacentric and satellited. Except in ‘Golden Spur’, where one triplet is heteromorphic, all the cultivars have homomorphic karyotypes. Diploid ‘Telamonius Plenus’, 3x ‘Golden Spur’ and 4x ‘Beersheba’ have 2, 3 and 4 satellited chromosomes respectively, whereas ‘Emperor’ and ‘Empress’, both 3x, have only one. The number of nucleoli at interphase matches with the number of SAT-chromosomes in ‘Telamonius Plenus’ and ‘Golden Spur’. ‘Emperor’ and ‘Empress’, however, have 2 and 3 additional, though vary small, nucleoli respectively.
Of 29 anther-culture-derived 2x-plants of cabbage (Brassica oleracea L. ssp. capitata L.), 45% were male sterile (ACMS) and 55% male fertile (ACMF). Chi-square test was used to compare the percentage of pollen mother cells (PMCs) with meiotic abnormalities in ACMF or ACMS plants with those in anther donor (control) plants. In metaphase I, univalents, trivalents and quadrivalents were frequently observed but only in the ACMS group were these abnormalities significantly higher than in the control. In anaphase I to telophase I, there were significantly higher occurences of laggards and other abnormalities including unequal chromosome segregation in both ACMF and ACMS groups; there were 2.6 time more laggards in the ACMS group. In anaphase II to telophase II, micronuclei, tripoles, unequal chromosome distribution and sporads with dyads and triads were frequently observed in both ACMF and ACMS but, in all cases, occurrences were markedly higher in the ACMS group accompanied by significantly lower 9-9-9-9 equal chromosome segregation. High incidence of sterility and chromosomal abnormalities in anther-culture-derived 2x-plants, particularly in the ACMS group, appears to be the result of homozygosity induced by anther culture.