Effect of cisplatin on Allium cepa root meristem cells

Allium cepa root growth was retarded by cisplatin treatment in a dose-dependent manner. A decrease in the mitotic index (MI) and an increase in the number of interphase cells was seen in cisplatin treated root tips. An increase in the frequency of abnormal mitoses and chromosomal aberrations was also observed in cisplatin treated groups which indicates its genotoxic effect on plant cells. The endogenous glutathione (GSH) level in the root tips decreased significantly after cisplatin treatment which may favour its increased interaction with cellular DNA thereby developing enhanced chromosomal aberrations and affecting cell divisions and root growth. It is suggested that the decrease in endogenous GSH may be related to the development of cisplatin-mediated genotoxic effects in plants.     

Cytotoxic and genotoxic effects of Br-containing oxaphosphole on Allium cepa L. root tip cells and mouse bone marrow cells

The continuous production and release of chemicals into the environment has led to the need to assess their genotoxicity. Numerous organophosphorus compounds with different structures have been synthesized in recent years, and several oxaphosphole derivatives are known to possess biological activity. Such chemical compounds may influence proliferating cells and cause disturbances of the genetic material. In this study, we examined the cytotoxicity and genotoxicity of 4-bromo-N,N-diethyl-5,5-dimethyl-2,5-dihydro-1,2-oxaphosphol-2-amine 2-oxide (Br-oxph). In A. cepa cells, Br-oxph (10(-9) M, 10 (-6) M and 10 (-3) M) reduced the mitotic index 48 h after treatment with the two highest concentrations, with no significant effect at earlier intervals. Mitotic cells showed abnormalities 24 h and 48 h after treatment with the two lowest concentrations but there were no consistent changes in interphase cells. Bone marrow cells from mice treated with Br-oxph (2.82 x 10 (-3) μg/kg) also showed a reduced mitotic index after 48 h and a greater percentage of cells with aberrations (principally chromatid and isochromatid breaks). These findings indicate the cytotoxicity and genotoxicity of Br-oxph in the two systems studied.     

The effect of butyrate on cell cycle progression in Allium cepa root meristems

Sodium butyrate at 4 m M and above blocked cell proliferation in root meristems of Allium cepa L. bulbs. Cytophotometric determinations in asynchronously growing cells, as well as cycle kinetics in synchronous binucleate cells. indicated that blocking took place at mid-G₁ and at, or close to, the S/G₂ border. Cell progression through S phase and mitosis was little affected. The cell cycle blockage induced by 6 m M butyrate was reversible when the drug was applied for periods of time not exceeding 12 h. Butyrate did not affect nucleic acid and protein synthesis activities, though its action on the cell cycle ressembled that produced by translation inhibitors.     

Salt-induced abnormalities on root tip mitotic cells of Allium cepa: prevention by inositol pretreatment

Salt-induced growth reduction of plants is a well-known phenomenon which poses major problem in crop productivity in places where vast majority of land plants are affected by salt. In this report, studies were carried out to reveal the effect of salt injury on the cell division pattern in roots and the role of myo-inositol in preventing the salt-induced ion disequilibrium on the chromosome and DNA degradation in roots. Present study revealed induction of various chromosomal abnormalities on the root tip mitotic cells of Allium cepa by treatment with different concentrations of NaCl (0–500 mM) for 24 h as also the amelioration of such effect by prior treatment of the roots with different concentration of myo-inositol (0–300 mM). Results showed that a narrow albeit definite range of extracellular myo-inositol (100–150 mM) is effective in preventing internucleosomal fragmentation which is the early response in roots under salt stress. Transgenic tobacco plants overexpressing Oryza (OsINO1) as well as Porteresia (PcINO1) cytosolic l-myo-inositol-1-phosphate synthase coding genes can withstand and retain their chromosomal and DNA integrity in 100 mM NaCl solution and can subsequently prevent DNA fragmentation, caused by intracellular endonuclease activity at this salt concentration.     

Anti-mitotic and anti-genotoxic effects of Plantago lanceolata aqueous extract on Allium cepa root tip meristem cells

Plantago is the most important genus of Plantaginaceae family and is used in traditional medicine around the world for different purposes. Plantago coronopus L., Plantago major L., Plantago media L. and Plantago lanceolata L. are most commonly used species of Plantago in traditional medicine in Turkey. The main goal of this study was to investigate the eventual anti-mitotic and anti-genotoxic effects of P. lanceolata L. leaf aqueous extracts (15 g/L and 30 g/L) on Allium cepa L. root tip meristem cells which were treated with 0.7% hydrogen peroxide. For this purpose, two different experiments were performed under the same conditions. In the first experiment, Allium cepa onion bulbs were treated with 0.7% H₂O₂ for 1 h. After the H₂O₂ treatment, the onion bulbs were treated with two different concentrations (15 g/L and 30 g/L) of P. lanceolata extracts for 24 h. In the second experiment, A. cepa onion bulbs were treated with two different extract concentrations (15 g/L and 30 g/L) for 24 h and then with 0.7% H₂O₂ for 1 h. The test concentrations were determined according to doses which are recommended in alternative medicinal usage by people. As positive and negative control 0.7% H₂O₂ and tap water was used, respectively. As a result, it was determined that aqueous extracts reduced mitotic index and chromosome aberrations in treatment groups in comparison with controls. These results showed that P. lanceolata aqueous extracts have anti-mitotic and anti-genotoxic effects.     

Auxin deficiency at the onset on root growth in Allium cepa

Summary 3-Indolylacetic acid (IAA) increased the length of the epidermis cells of onion roots during the initial stage of root growth, when cell length has not yet reached its maximum value, by up to 50% (10^–11 M), while in the later, steady-state or dynamic equilibrium stage no promotive effects were present. It is suggested that the lesser elongation capacity of the cells at the onset of root growth is related to a deficiency in auxin while the steady-state phase is characterized by hormonal balance.     

Cytotoxic effect of chlorophenols on cells of the root meristem of welsh onion (Allium fistulosum L.) seeds

Chlorophenols are precursors to more dangerous environmental toxicants, which are characterized by mutagenic and carcinogenic properties. The methods of bioassay on plant test objects to study the influence of different pollutants allow one to connect the mutagenicity and cytotoxicity of investigated substances. The genotoxic and cytotoxic effects of pentachlorophenol and trichlorophenol solutions on root meristem cells of the Welsh onion Allium fistulosum L. shoots have been studied. Doze-dependent inhibition of seed germination of Welsh onions as a consequence of the influence of pentachlorophenol and trichlorophenol solutions with different concentrations shows a significantly greater toxic effect of pentachlorophenol, dependending on the doze, on seed germination than trichlorophenol.     

The effect of lead on Allium cepa L.

The effect of lead on Allium cepa L. at concentrations of 0.1, 1.0, 10, 50, 100 and 200 ppm were studied. Analysis focused on root growth, frequency of mitosis in a meristematic zone, and chromosomal aberrations. It was observed that lead reduces root growth and the frequency of mitotic cells in meristematic zones, and increases the frequency of aberrant cells. The intensity of the effects is a function of lead concentration.     

Genotoxicity of five food preservatives tested on root tips of Allium cepa L

The effects of the food preservatives sodium benzoate (SB), boric acid (BA), citric acid (CA), potassium citrate (PC) and sodium citrate (SC) have been studied on root tips of Allium cepa L. Roots of A. cepa were treated with a series of concentrations, ranging from 20 to 100 ppm for 5, 10 and 20 h. The results indicate that these food preservatives reduced mitotic division in A. cepa compared with the respective control. Mitotic index values were generally decreased with increasing concentrations and longer treatment times. Additionally, variations in the percentage of mitotic stages were observed. The total percentage of aberrations generally increased with increasing concentrations of these chemicals and the longer period of treatment. Different abnormal mitotic figures were observed in all mitotic phases. Among these abnormalities were anaphase bridges, C-mitosis, micronuclei, lagging, stickiness, breaks and unequal distribution.     

Developmental profile of intracellular compatments during Allium cepa root cell germination

The efflux kinetics of ⁸⁶Rb from 24 hr preloaded Allium cepacv. Evergreen Long White Bunching root tip cells through thefirst 120 hr of germination have been documented. Estimatesof the percent of isotope, the calculated amount present andthe halftime of efflux of the three root cell compartments presentwere made. Of the total isotope present the % in the vacuoledecreased from maxima of 64% to 40% with germination time, whilethe % of the isotope in the cytoplasm remained uniform near39%. The free space increased maximally throughout germinationto 20% by 120 hr. Rb content, based on specific activity calculations,of the slowest, intermediate and fastest compartments was seento rise from low levels at 52 hr germination toward maximalvalues by 96 hr. Speculation as to when a germinating root becomesfunctionally mature was attempted by comparing the times ofonset of major macromolecule synthesis (DNA, RNA, protein) tothat of maximal Rb content. Stable mitotic and DNA syntheticindices occurred at the 10 mm (72 hr) stage with the initiationof major macromolecules syntheses occurring prior to 2 mm (40hr). ⁸⁶Rb efflux data suggests that the compartments do notcontain maximal amounts until the 22 mm (96 hr) stage. (Received December 26, 1978; )     

Inter- and intrachromosomal asynchrony of cell division cycle events in root meristem cells of Allium cepa: possible connection with gradient of cyclin B-like proteins

Alternate treatments of Allium cepa root meristems with hydroxyurea (HU) and caffeine give rise to extremely large and highly elongated cells with atypical images of mitotic divisions, including internuclear asynchrony and an unknown type of interchromosomal asynchrony observed during metaphase-to-anaphase transition. Another type of asynchrony that cannot depend solely on the increased length of cells was observed following long-term incubation of roots with HU. This kind of treatment revealed both cell nuclei entering premature mitosis and, for the first time, an uncommon form of mitotic abnormality manifested in a gradual condensation of chromatin (spanning from interphase to prometaphase). Immunocytochemical study of polykaryotic cells using anti-β tubulin antibodies revealed severe perturbations in the microtubular organization of preprophase bands. Quantitative immunofluorescence measurements of the control cells indicate that the level of cyclin B-like proteins reaches the maximum at the G2 to metaphase transition and then becomes reduced during later stages of mitosis. After long-term incubation with low doses of HU, the amount of cyclin B-like proteins considerably increases, and a significant number of elongated cells show gradients of these proteins spread along successive regions of the perinuclear cytoplasm. It is suggested that there may be a direct link between the effects of HU-mediated deceleration of S- and G2-phases and an enhanced concentration of cyclin B-like proteins. In consequence, the activation of cyclin B-CDK complexes gives rise to an abnormal pattern of premature mitotic chromosome condensation with biphasic nuclear structures having one part of chromatin decondensed, and the other part condensed.     

Subcellular localization of chromium and nickel in root cells of Allium cepa by EELS and ESI

The ultrastructural investigation of the root cells of Allium cepa L. exposed to two different concentrations of chromium + nickel (Cr+Ni) (10 micromol/L and 100 micromol/L) revealed that toxic symptoms were induced by increasing heavy metal concentration and treatment time. Several significant ultrastructural changes were caused by 100 micromol/L Cr+Ni - deposition of electron dense material in cell walls; larger vacuolar precipitates surrounded by membranes inside vacuoles; increment of disintegrated organelles and high vacuolization in cytoplasm. The localization of the precipitates in which the metal ions were detected by electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI) was investigated. Chromium and nickel were localized in the electron dense precipitates of the root cells exposed to only 100 micromol/L Cr+Ni. None were found in the root cells exposed to 10 micromol/L Cr+Ni. Higher amounts of Cr+Ni were mainly accumulated in the cell walls and vacuoles of the fourth or fifth cortical layer.     

Genome size of man and animals relative to the plant Allium cepa

A direct Feulgen-cytophotometric comparison of the genomic DNA content (C value) was performed between the liliaceous plant species Allium cepa and a number of animal species to reassess the genome size ratios between plants and animals. These appeared unduly ambiguous as a consequence of divergent picogram estimates in several animal reference species. Taking 1C = 16.75 pg for Allium cepa, the estimates were (1C value in picograms): man, 3.11; Indian muntjak CCL 157 cell line, 2.68; domestic pig, 2.79; Chinese hamster, 2.66; CHO cell line, 2.73; laboratory rat, 2.65; mouse, 3.04; rat kangaroo Pt-K2 cell line, 4.21; fowl, 1.16; and the green toad, 4.30. These values are consistent with a number of independent absolute and relative DNA content determinations reported for animals, and therefore define a coherent set of animal and plant reference values for genome size determinations.