Onion Root Meristems Research Articles

Removal of bentazone using activated carbon from spent coffee grounds

AbstractBACKGROUNDThis study aimed to produce activated carbon (AC) from spent coffee (Coffea arabica) grounds by chemical activation using zinc chloride (ZnCl2) and nitric acid to remove bentazone from aqueous solutions.RESULTSThe fresh spent coffee grounds were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the AC by X‐ray diffraction (XRD), infrared spectroscopy (FTIR), Brunauer–Emmett– Teller (BET), point of zero charge, scanning electron microscopy (SEM) and the Boehman method. Adsorption experiments were carried out in a batch system. The results showed a 70% efficiency in bentazone removal using ZnCl2 carbon. Kinetic studies indicate that the adsorption rate increased slowly up to 720 min; the first‐ and second‐order models fitted the experimental data at a concentration of 50 mg L−1. The adsorption equilibrium is represented by the Langmuir model with a high adsorption capacity of 279.33 ± 6.29 mg mg−1. The adsorption efficiency was also confirmed by toxicity analysis of the effluent with bentazone at 50 mg L−1, using the Allium cepa bioassay, a high‐sensitivity test for pollutants in water.CONCLUSIONBefore adsorption, the effluent caused significant cytogenotoxicity to onion root meristems. After adsorption, the generated effluent no longer caused toxicity to the test system, and the results obtained were similar to the control with distilled water. © 2024 Society of Chemical Industry (SCI).

Evaluation of cytogenetic effect of pesticides in onion root meristem

Farmers use chemical insecticides, fungicides and herbicides to control insect pests, diseases and weeds. Extensive use of chemical pesticides is becoming hazardous to the environment and human and animal health. Biopesticides have been used as a safer alternative. Cytogenetic analysis is needed to determine the effects of chemical and biopesticides in plants if these are used frequently in an improper concentration. This investigation assessed the effects of a chemical systemic insecticide ‘Actara 25WG’ and a bioinsecticide ‘Bio Sona’ for seed germination and on root mitosis of five onion varieties. Three concentrations of Actara 25WG were used as seed treatment, viz., 25 g, 50g (recommended) and 75 g/kg seed. Similarly, Bio Sona was applied @ 2 %, 5 % (recommended) and 8 % concentrations. Depressing effects of the two pesticides were recorded in seed germination percentage except for Bio Sona 2% in variety Bhima Shakti. Actara 25WG and Bio Sona showed either mitoenhancing or cytotoxic effects depending on dose and variety. These pesticides also induced genotoxicity at recommended and higher doses on root tip cells as indicated by the frequency of total chromosomal aberrations like binucleate cells, clumps, stickiness, disturbed stage, laggards, bridges and fragments. Bio Sona at higher concentrations showed more aberrations than Actara 25WG. There were differential responses of the varieties to the pesticide treatment. More research must be done on the effects of chemicals and biopesticides in plants to assess their cytogenotoxicity.

The Anti-Mitotic Effects of Annona Muricata Extracts to Allium Cepa Root Meristems

Guyabano (Annona muricata) harbors a wide array of bioactive compounds that confer significant therapeutic properties. In an attempt to uncover its anti-cancer properties, we investigated the antimitotic effects of guyabano seed extracts on onion (Allium cepa) root meristems.
 Methods
 The present study utilized the Posttest Only Control Group Design. Onion root meristems were exposed to four distinct concentrations of aqueous and ethanolic extracts of guyabano seeds for 48 hours. For baseline conditions, the negative control group was treated with water whereas the positive control group received methotrexate.
 Results
 Among the various concentrations of guyabano seed extract treatments, the 800mg/100mL concentration exhibited the lowest mean mitotic index (MMI) in both aqueous and ethanolic solutions (40.33±24.50 and 32.00±9.85, respectively). However, statistical analysis revealed no significant differences between the aqueous and ethanolic treatment concentrations when compared to the negative and positive controls (P=0.40).
 Conclusion
 The antimitotic effects of aqueous and ethanolic seed extracts of guyabano on onion root meristems were found to be insignificant. However, the lower MMI of both aqueous and ethanolic concentrations of 800mg/100 mL guyabano compared to positive control (methotrexate) warrants further research to assess the antimitotic effects of guyabano.

Влияние урбанизированных территорий на митотическую активность клеток меристемы корней лука репчатого (Allium cepa L.)

The article presents the results of the use of cytogenetic methods in assessing the impact of urbanized territories on the mitotic activity of cells of the onion root meristem Allium cepa L. The research was carried out on 4 sites with different anthropogenic load. The Allium test research method is based on the analysis of the values of the mitotic index of the meristem cells of the Allium cepa L. root sprouted on the melted snow water of the studied points. The study showed that pollution of urbanized territories has a mutagenic effect, causing the formation of chromosomal aberrations and other types of mitosis pathology in the cells of the apical meristem of the roots of Allium cepa L. Keywords: CYTOGENETIC METHODS, MITOTIC INDEX, ALLIUM TEST, ONION, URBANIZED TERRITORIES

Novel Insight into Utilization of Flavonoid Glycosides and Biological Properties of Saffron (Crocus sativus L.) Flower Byproducts.

Saffron (Crocus sativus L.) byproducts are considered as a cheap source of bioactive polyphenolics endowed with potential antioxidant effects. The saffron biowaste is utilized for extraction of flavonoid glycosides and their potential biological properties. The total amount of polyphenolics and polysaccharides was found to be higher in the tepal than in the stamen. The bioactive compounds quercetin-3-O-sophoroside (Q-3-sop) and kaempferol-3-O-sophoroside (K-3-sop) were analyzed using high-performance liquid chromatography equipped with a photodiode array detector (HPLC-PDA) and identified by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR). The antioxidant effects were studied using 2,2 diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), ferric ion reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC); Q-3-sop showed stronger antioxidant effects compared to K-3-sop, crocin-I, and crocin-II. Furthermore, Q-3-sop also inhibited cell apoptosis caused by H2O2 by reducing the levels of cellular reactive oxygen species (ROS). In terms of cytogenetic effects, Q-3-sop revealed no cytogenic effects on onion root meristem cells but chromosomal aberration was observed at the highest dose (200 ppm). Thus, saffron byproducts and its flavonoids could be utilized as natural antioxidant agents with no cytogenetic effects.

Genotoxicity Assessment of Bottom Sediments of the Chumysh River Using the Allium-Test

We performed a bioassay of aqueous extracts from the bottom sediments of the Chumysh River near the settlement of Talmenka (the Altai Territory of Russia) using the Allium test. The presence of toxic components that caused a decrease in the mitotic activity of onion root meristem cells was revealed. The frequency of pathological mitoses, significantly exceeding the background value (on average, 16.3 times), indicates the presence of factors with total mutagenic activity in the samples. We found violations of chromosome divergences (emissions beyond the spindle, lagging, running off and premature chromosome divergence), abnormalities of the mitotic apparatus (multipolar, asymmetric, monocentric mitosis, polyploidy), bridges (single and multiple). The prevalence of spindle pathologies suggests chemical contamination of the bottom sediments. Stress factors present in bottom sediments activate adaptive mechanisms of the test-object cells, aimed at maintaining their viability and reliability of the transmission of genetic information to the next cellular generations. Such adaptation mechanisms include the formation of micronuclei and cell polyploidization.

Assessment of the genotoxicity of water and soil in the places of storage of reserves of old pesticides by Allium-test

Pesticides and persistent organic pollutants (POPs) are a serious environmental problem for almost all countries of the world. The toxic and mutagenic activity of samples of natural water and water extracts of soils collected near the storage sites of old and prohibited pesticides located in the villages of Kyzylkairat, Amangeldy, Beskainar, Belbulak, Enbekshi. Territories of comparison Basshi village (Altyn Emel National Park) and near farmland, where pesticides were used in the past (Taukaraturk village, Almaty region) was investigated. Allium cepa L. was used as a biological test system. The mitotic activity and the frequency of disturbances at different stages of mitosis in onion root meristem were evaluated. Chemical analysis showed that in all soil samples the total content of 24 POPsPesticides exceeds the maximum permissible concentration (MPC). It was established that the level of mitotic activity of Allium cepa cells in all samples was slightly reduced compared with the control. In soil samples, the frequency of micronuclei in interphase cells (0.22-3.25%) is higher than in water samples (0.36-0.99%) (control 0.41%). The revealed increased level of cytogenetic disorders correlates with the total content of organochlorine pesticides.

Exposure to mobile phone radiations at 2350MHz incites cyto- and genotoxic effects in root meristems of Allium cepa.

The exponential increase of electromagnetic field radiations (EMF-r) in the natural environment has raked up the controversies regarding their biological effects. Concern regarding the putative capacity of EMF-r to affect living beings has been growing due to the ongoing elevation in the use of high frequency EMF-r in communication systems, e.g. Mobile phones. In the present study, we tried to examine the cyto- and genotoxic potential of mobile phone EMF-r at 2350MHz using onions (Allium cepa L.). Fresh adventitious onion roots were exposed to continuous EMF-r at 2350MHz for different time periods (1h, 2h and 4h). The evaluation of cytotoxicity was done in terms of mitotic index (MI), phase index and chromosomal aberrations. Genotoxicity was investigated employing comet assay in terms of changes in % HDNA (head DNA) and % TDNA (tail DNA), TM (tail moment) and OTM (olive tail moment). Data were analyzed using one-way ANOVA and mean values were separated using post hoc Tukey's test. The results manifested a significant increase of MI and chromosomal aberrations (%) upon 4h, and ≥ 2h of exposure, respectively, as compared to the control. No specific changes in phase index in response to EMF-r exposure were observed. The % HDNA and % TDNA values exhibited significant changes in contrast to that of control upon 2h and 4h of exposure, respectively. However, TM and OTM did not change significantly. Our results infer that continuous exposures of radiofrequency EMF-r (2350MHz) for long durations have a potential of inciting cyto- and genotoxic effects in onion root meristems.

Identifying tissue sap toxicity in certain plantain species by bioindication

Toxic substances influence vitally important processes in plants. Studying plant reactions to environmental pollution is one of important objectives. Among pollutants accumulated in P. major L. and P. media L. plants, a group of heavy metals (As, Cr, Cu, Mo, Ni, Pb, Sr, Zn) was separated. Each species with its genotypic differences and specific degree of flexibility reacts to environmental exposure differently. Bioindication at tissue and cell levels is based on close process limits of biotic and physiological reactions. Its advantage is high sensitivity to disruptions, which allows identifying small concentrations of pollutants. Bioindication at these specific levels enables early identification of environmental disruptions. The work examined root meristem mitosis of Allium cepa L. The laboratory test recorded the frequency of abnormal and normal mitoses in the cells of onion root meristems (Allium cepa L.) given that the onion was treated with extracts of different concentrations (0.5… 5wt.%) of Plantago major L. and Plantago media L. growing in the anthropogenic areas of Tobolsk city (Tyumen region, Russian Federation).

Allelopathy and Anti-mitotic Effects of Cuscuta campestris and Cuscuta monogyna Extracts on Plant Cell Division

Some natural compounds of plants including phenols and alkaloids induce mitosis depressive that are blocked cell division. Field dodder (Cuscuta campestris Yunck.) and eastern dodder (Cuscuta monogyna Vahl.) are the most widespread obligatory parasitic species. In the present study, end of summer 2015, field dodder and eastern dodder are collected from Alhagi maurorum Medik. host and Vine (Vitis sylvestris C.C.Gmel.) host respectively from Markazi province of Iran and identified by department of botany of Islamic Azad University of Saveh. The aerial parts of dodders were used for aqueous extract. Dodders alkaloid and poly phenol were visualized by TLC and Dragendorff (for alkaloid) and ferric salt (for poly phenol) reagents. Total phenols and alkaloid were measured by using the calibration and spectrophotometry methods. Root length and roots tip meristem model of onion bulbs and barley seedlings were utilized to allelopathy and antimitotic effects of dodders aqueous extracts. Standard cytotoxic 8-Hydroxyquinoline served as controls. The bulbs and barley seedlings were treated at various concentrations: 0.05, 0.1 and 0.2 mgml-1 (dw) of and aqueous extract of dodders and 8-Hydroxyquinoline for 6 and 12 h. The inhibitory effect of dodders extract were evaluated on the growth and mitotic activity (Mitotic index) of barley seedlings and onion root meristems and the effect was compared with standard 8-Hydroxyquinoline. The One Way ANOVA test was used for statistical analysis. The poly phenols of field dodder was condensed tannins (include flavonoids) but for eastern dodder hydrolysable tannins. Like 8-Hydroxyquinoline, both field and eastern dodders extracts significantly inhibited the growth of roots and mitotic activity in incubation time and dose-dependent manner. However, C. campestris extract was more allelopathy and antimitotic potent in this regard and produced root decay and mitosis arrest. The extract of dodders had inhibitory and mitosis depressive effect on root tip meristem cells. In the present study we found, the dodders aqueous extracts can been used to produce desirable effects as it pertains to chromosome condensation and spread, and though the roles of these chemicals in spindle fiber inhibition have been elucidated, as 8-Hydroxyquinoline.

Protective Efficacy ofPhyllanthus amarusL against Radiation – Induced Chromosomal Damages in Onion Root Meristems

The protective effect of Phyllanthus amarus L in the irradiated roots of onion was evaluated. The results were indicated that the Phyllanthus extract showed a radio modifier effect by reducing the frequency of aberrant cells in the meristematic cells exposed to gamma rays.

Metaphase arrest and delay in cell cycle kinetics of root apical meristems and mouse bone marrow cells treated with leaf aqueous extract of Clerodendrum viscosum Vent

To study cell cycle delay and metaphase arresting activity of leaf aqueous extract of Clerodendrum viscosum Vent. (LAECV) in root apical meristems and mouse bone marrow cells. Cell cycle delay and metaphase arresting activities of LAECV were analysed, in root apical meristems of onion and wheat, and in mouse bone marrow cells, by scoring mitotic index, metaphase frequency and transition of cells from metaphase to anaphase. Colchicine was used as the standard metaphase arresting drug. Phytochemicals present in LAECV were detected and their phytotoxic activity was evaluated by analysing green-gram (Vigna radiata) seedling's root growth retardation and branch root swelling phenomenon. LAECV treatment resulted in dose-dependent root growth retardation of green-gram seedling root length (P < 0.01) and half maximal growth inhibitory concentration (IC(50) ) of LAECV was 0.87 mg/ml at 144 h. In onion and wheat root meristem cells the mitotic index decreased, metaphase frequency increased and transition from metaphase to anaphase reduced. Experimentation with mouse bone marrow cells indicated that LAECV induced metaphase arrest (164.3% increase in arrested metaphases per 300 mg/kg body weight, over 2.5 h). Phytochemicals like carbohydrates, glycosides, saponins, terpenoids, triterpenoids, tannins and trace amounts of alkaloids were detected in LAECV. It may be said that LAECV contains mitostatic and metaphase arresting components that are able to induce significant metaphase arrest in root apical meristems and also in mouse bone marrow cells.

Essential oils of Schinus terebinthifolius and S. molle (Anacardiaceae): Mitodepressive and aneugenic inducers in onion and lettuce root meristems

Essential oils constitute an important group of plant products and include a mixture of volatile low-molecular-weight terpenes. The present study aimed to determine the phyto- and cytotoxicity of essential oils from leaves of Schinus molle and Schinus terebinthifolius on lettuce and onion. These essential oils affected germination, initial growth, and mitotic and metaphasic indexes of the target species. Compared to negative controls, essential oils of S. molle and S. terebinthifolius reduced the mitotic index of onion by 21.05% and 82.03%, respectively. Similar results were observed for lettuce. The volatiles also induced chromosomal abnormalities such as spindle disturbance at late prophase, sticky metaphase, c-mitosis, micronucleus, and nuclear buds. Although the essential oils of both species shared the same major compound (α-pinene), more pronounced effects were observed in S. terebinthifolius treatments. The results suggest that major and minor compounds of these essential oils act in synergy, causing the inhibitory effects observed on onion and lettuce.

Comparative study of the sensitivities of onion and broad bean root tip meristematic cells to genotoxins

Chemicals which cause chromosomal aberration (CA) in plant cells frequently produce identical CA in cultured animal cells. Plant species however, differ in sensitivities. Onion and broad bean (BB) root meristem cells were compared for sensitivity to chlorpyrifos (CPF), mercury chloride (HgCl2), ethyl methanesulphonate (EMS) and garden ripcord (GR). Seeds were germinated on moist filter paper until radicles appeared and exposed to three doses of each chemical for 24 h. About 1 - 2 cm length of root tip was cut, fixed, washed and hydrolyzed in 1 N HCl. Root tips were transferred to microscope slides, cut 2 mm from the growing tip, stained, covered with cover slip and squashed. Cytotoxicity was inferred when the mitotic index (MI) of treated cells was £ ½ of control. All chemicals were toxic to onion cells but only EMS and HgCl2 were toxic to BB. Genotoxicity was determined by analyzing 100 anaphase and telophase cells for chromosome fragments, bridges, vagrant chromosome, c-anaphase, multipolarity and stick chromosomes and aberrations at each dose compared with the control using the chi-squared test. All chemicals were genotoxic (P < 0.05) to onion but only CPF, HgCl2 and EMS were genotoxic to BB. Onion was more sensitive to 10 of 13 genotoxicity indices used.

Crude extract of the cyanobacterium, Hapalosiphon sp., causes a cessation of root elongation and cell division in several plant species

The phytotoxic activities of the crude extract from the cyanobacterium, Hapalosiphon sp., on the initial growth and root cell division of several plant species were investigated. Although the germination percentages of the plants were not affected by the extract, their root and shoot growth were remarkably suppressed, depending on the extract concentrations. Roots were more sensitive to the extract than shoots and the sensitivity, determined by the I50 concentrations between the susceptible and tolerant species, differed by 5 and 11 times in dicotyledonous and monocotyledonous plants, respectively. The mitotic index for wheat (Triticum aestivum L. cv. Norin 61) root cells was not affected, but the mitotic index for onion (Allium cepa L. cv. Raputa II) was reduced with the increasing concentration of the extract. In the onion root meristem, the number of cells in prophase, metaphase, anaphase, and telophase were decreased significantly with 6 g DW L−1 (g dry weight of algae L−1). This suggests that the extract might inhibit the processes regulating the entry of cells into mitosis.

Nuclear ploidy is contingent on the microtubular cycle responsible for plant cytokinesis

Division of the plant cell relies on the preprophase band of microtubules (PPB)-phragmoplast system. Cells of onion (Allium cepa L.) root meristems were rendered binucleate by preventing the consolidation of cell plate formation in telophase with 5 mM caffeine. These binucleates developed either a single PPB around one of their two nuclei or two PPBs, one per nucleus, in the prophase of the ensuing mitosis. Prophase cells developing one single PPB were shorter in length (42.3 +/- 4.1 microm) than those developing 2 PPBs (49.8 +/- 4.1 microm), and interphase duration was inversely related to cell length. Cells whose length was less than or equal to 42 microm, i.e., which had not even reached the mean size of the small binucleates in prophase, were followed throughout mitosis. In metaphase, they always assembled two mitotic spindles (one per nucleus). However, the cells that had assembled a single PPB also developed a single phragmoplast in telophase, leading to polyploidization. As these meristematic cells were not wide enough to accommodate the midzones of both mitotic spindles in any single plane transversal to the cell elongation axis, the spindles tilted until their midzones formed a continuum where the single common phragmoplast assembled. Its position was thereby uncoupled from that of the preceding PPB. Subsequently, the chromosomes from two different half-spindles were included, by a common nuclear envelope, in a single tetraploid nucleus. Finally, the cytokinetic plate segregated the two tetraploid nuclei formed at each side of the phragmoplast into two independent sister cells.

The association of peroxisomes with the developing cell plate in dividing onion root cells depends on actin microfilaments and myosin.

We have investigated changes in the distribution of peroxisomes through the cell cycle in onion ( Allium cepa L.) root meristem cells with immunofluorescence and electron microscopy, and in leek ( Allium porrum L.) epidermal cells with immunofluorescence and peroxisomal-targeted green fluorescent protein. During interphase and mitosis, peroxisomes distribute randomly throughout the cytoplasm, but beginning late in anaphase, they accumulate at the division plane. Initially, peroxisomes occur within the microtubule phragmoplast in two zones on either side of the developing cell plate. However, as the phragmoplast expands outwards to form an annulus, peroxisomes redistribute into a ring immediately inside the location of the microtubules. Peroxisome aggregation depends on actin microfilaments and myosin. Peroxisomes first accumulate in the division plane prior to the formation of the microtubule phragmoplast, and throughout cytokinesis, always co-localise with microfilaments. Microfilament-disrupting drugs (cytochalasin and latrunculin), and a putative inhibitor of myosin (2,3-butanedione monoxime), inhibit aggregation. We propose that aggregated peroxisomes function in the formation of the cell plate, either by regulating hydrogen peroxide production within the developing cell plate, or by their involvement in recycling of excess membranes from secretory vesicles via the beta-oxidation pathway. Differences in aggregation, a phenomenon which occurs in onion, some other monocots and to a lesser extent in tobacco BY-2 suspension cells, but which is not obvious in the roots of Arabidopsis thaliana (L.) Heynh., may reflect differences within the primary cell walls of these plants.

Advances in Microwave Assisted Specimen Processing. Benefits and Limitations Analyzed in Plant Nuclei and Drosophila Embryos in Vivo

Abstract Abstract Recently, specimen processing using microwave irradiation was described as a potential tool to enhance a variety of procedures used in microscopy including fixations, embedding, antigen retrieval (AGR) and immunolabeling (1,2,3). A comparison of conventional staining and staining after microwave irradiation was performed for several fluorescent vital nuclear stains, Performing the labeling reaction under controlled microwave irradiation results in significant improvements in the labeling of nuclei, such as shortening the times of incubation and allowing the detection of otherwise inaccessible sites. In addition to investigate the basis of the enhancement, we have labeled intact samples such as living onion root meristems and Drosophila embryos. In both systems, vital fluorescent nuclear stains were applied to the specimen on a glass slide and was microwave irradiated using a variable wattage microwave (model 3451 Ted Pella, Inc.). This resulted in clear fluorescent labeling of the nuclei. This result has not been previously reported in the absence of microwave treatment, other than by microinjection.

Enhancement of the immunocytochemical detection of antigens by microwave irradiation. Benefits and limitations analysed in isolated plant nuclei and Drosophila embryos in toto.

Performing the antibody reaction under controlled heating through microwave irradiation results in significant improvements in the immunovisualization of antigens, such as shortening the times of incubation, lowering the antibody titres used and allowing the detection of difficult, inaccessible antigens. In addition to investigate the basis of the enhancement, we have extended to more intact samples such as isolated plant nuclei and in toto Drosophila embryos the results previously reported only with tissue sections. A drop of heterologous anti-nucleolin antibody covering isolated nuclei from onion root meristems spread on a glass slide was microwave irradiated, resulting in clear immunofluorescent labelling of the nucleoli. This result was never previously obtained in the absence of microwave treatment, even using the complicated procedure previously reported for the homologous identification of this nuclear protein. Using the much larger and to some extent impermeable Drosophila embryos, we were able to show that the incubation time and concentration of the anti-myosin antibody can be strongly reduced by performing the reaction at 45 degrees C under microwave irradiation. The controlled increase in temperature is the main factor responsible for these improvements; the importance of maintaining an adequate mixing of the samples is also emphasized. The proper implementation of these two experimental conditions will require the introduction of appropriate mixing accessories and temperature measuring probes for samples of small volume in current microwave laboratory ovens.

Timing the phases of the microtubule cycles involved in cytoplasmic and nuclear divisions in cells of undisturbed onion root meristems

The duration of the different phases of the microtubule and chromosome cycles were estimated in the native diploid cell populations of Allium cepa L root meristems proliferating undisturbed, under steady state conditions, at the physiological temperature of 15°C. The cycles were coupled by considering their fitting in relation to the short process of nuclear envelope breakdown. In the cycle related to cytoplasmic division, the preprophase band which predicts the future position of the phragmoplast made its appearance, as a wide band, 16 mm before the G 2 to prophase transition, ie it was only present during the final 5% of the total G 2 timing (5 h 30 mm). The band became narrow only 6 mm after prophase had started and it was present in this form for the remaining prophase time (2 h 24 mm). Its disappearance occurred strictly coinciding with nuclear envelope breakdown, at the end of prophase. No microtubules related to cytoplasmic division were apparent until 9 mm after telophase had initiated. The two initial stages of phragmoplast formation which followed occupied, respectively, 27 mm and 54.5 mm of the 2-h long telophase. On the other hand, the third and last stage in phragmoplast formation covered both the final 35 mm of mitosis and the 6 initial mm of the G 1 of the next interphase. A very short (less than 4 mm) stage of microtubular nucleation around the nuclear envelope took place immediately afterwards, before the cortical array of microtubules appeared. The microtubule cycle related to nuclear division started with the apparent activation of the future spindle poles 7.4 mm before prophase was over. The mitotic spindle developed in the 5.6 mm long prometaphase. The spindle functioned in metaphase for the 42 mm it lasted, half spindles being separated for the 37 mm anaphase occupied in these cells.