Allium Cepa Root Cells Research Articles

Effects of the herbicide Tribunil on root mitosis of Allium cepa.

The present work was carried out to investigate the cytological effects of the herbicide Tribunil on Allium cepa root cells. The roots were treated with different concentrations for different periods (more details in the text). The results obtained showed that Tribunil inhibits spindle formation and is mitodepressive in function. The herbicide induced also clastogenic effects such as laggards, bridges, breaks and fragments, and therefore it is recorded to be a potential mitotic poison.

Cell size of proliferating plant cells increases with temperature: Implications in the control of cell division

As chemical reactions related to the regulation of cell proliferation are governed by availability, amount, and concentration of relevant molecules, it has been suggested that cell size is an important factor in the control of cell cycle. We have measured the size of proliferating cells of Allium cepa roots in which growth rate was modified by changes in growth temperature. Two independent cell size parameters have been measured by cytophotometry: cell surface area projection and cell protein content. Average cell sizes of both the proliferating cell population and the subpopulation at the end of mitosis show that cell size increases with growth rate. Calculation of cell size at initiation of DNA replication clearly indicates that average cell size at this point is not growth invariant but positively correlated with growth rate.

Exponential pattern of cell age distribution in dividing cells of plant meristems

In order to determine the pattern of cell age distribution in proliferating cells of Allium cepa roots we have measured by cytophotometry two cell size parameters, protein content and surface area projection, in cells that correspond to the entire proliferating population or only to the ana-telophase subpopulation. The size values of ana-telophase cells have been employed to construct theoretical size distributions for the entire proliferating cell population of the root meristem by assuming either a uniform or an exponential cell age distribution. Statistical comparison of theoretical distributions with the experimental one rules out a uniform cell age distribution and strongly favours an exponential age distribution similar to that found in bacteria.

Effect of Copper Phthalocyanine Derivatives on Sister Chromatid Exchanges in BrdU-substituted Chromosomes of Allium cepa

Summary The effect of some copper phthalocyanine derivatives on sister chromatid exchanges (SCEs) in meristematic cells of Allium cepa roots was studied. A significant increase in SCEs frequencies was observed when BrdU-substituted chromosomes were subjected to the cationic phthalocyanines Alcian blue 8GS, Astra blue and Cuprolinic blue for 3 hours at the end of the G 1 period of the second division cycle. Among the anionic phthalocyanine compounds, only Luxol fast blue MBSN increases the SCEs over the control baseline.

Effect of copper coordination complexes on sister-chromatid exchanges in plant cells

The effectiveness of several copper coordination complexes in the induction of sister-chromatid exchanges (SCE) in meristematic cells of Allium cepa roots was studied. A significant increase in the frequencies of SCE was observed when cells were exposed to different concentrations of copper complexes for 3 h. This effect, which is concentration dependent, seems to be related to the possibility of intercalative binding modes between the planar copper complexes and DNA.

Effect of copper coordination complexes on sister-chromatid exchanges in plant cells

The effectiveness of several copper coordination complexes in the induction of sister-chromatid exchanges (SCE) in meristematic cells of Allium cepa roots was studied. A significant increase in the frequencies of SCE was observed when cells were exposed to different concentrations of copper complexes for 3 h. This effect, which is concentration dependent, seems to be related to the possibility of intercalative binding modes between the planar copper complexes and DNA.

Uracil-DNA glycosylase activity is modulated by the proliferation rate and is lost upon differentiation of Allium cepa root cells

Uracil-DNA glycosylase activity of dividing Allium cepa root cells correlates with the rate of cell proliferation. In non-dividing cells this DNA repair activity depends on the potential capacity of the cells to proliferate: dormant cells have a high uracil-DNA glycosylase activity, as high as proliferating cells, whereas differentiated cells show a sharp decrease in their capacity to remove uracil from DNA.

Regulation of G 1 and G 2 by cell size in higher plants

Two cell size parameters, protein content and surface area projection, have been measured in proliferating cells of Allium cepa roots. Cells increase in size at birth and DNA synthesis termination when grown in the presence of hydroxyurea; under these conditions, G 1 and G 2 are reduced without affecting the growth rate. Opposite cell size changes at the same points are induced by growth in the presence of anisomycin under conditions in which G 1 and G 2 are extended, the former in higher proportion to the generation time and the later in less proportion. These results, while being consistent with cell size regulation of G 1 and G 2, suggest that the nature of G 1 and G 2 controls is different.

The symplast concept a general theory of symplastic transport according to the thermodynamics of irreversible processes

The movement of solutes through the symplasm (from cell to cell via the bulk cytoplasm and cytoplasm filled plasmodesmata) is examined in the steady state according to the thermodynamics of irreversible processes. This analysis together with a survey of the biological literature has yielded the following tentative conclusions:o(1)Plasmodesmata are commonly found in a fairly wide range of plants (Laminaria, Tamarix, Allium, Viscum, Avena, Lycospersicum, Salix, Nitella, Zea, etc.).(2)Plasmodesmata occupy anywhere from 0·08 to 0·002 times the area in common between adjacent cells; a relative area of about 0·01 (found in the mature cortical cells of Allium cepa roots) is not unusual.(3)The plasmodesmata constitute the pathway of least resistance for the diffusion of all small solutes.(4)Diffusion will be the predominant mechanism of transport across the pores for small solutes.(5)Solute distribution within the bulk cytoplasm of each cell ought to be by a combination of self diffusion and cyclosis.(6)There ought to be nearly perfect mixing within the bulk cytoplasm of each cell.(7)In the course of the symplastic transport of solutes in the steady state there can be a significant coupling of water transport under proper conditions.(8)The concentration drop of salts between adjacent cortical cells of onion roots necessary to transport all the observed salt flux into the xylem is 0·1 mn per cell or about 1 mn over the entire width of the cortex. Plasmodesmata are commonly found in a fairly wide range of plants (Laminaria, Tamarix, Allium, Viscum, Avena, Lycospersicum, Salix, Nitella, Zea, etc.). Plasmodesmata occupy anywhere from 0·08 to 0·002 times the area in common between adjacent cells; a relative area of about 0·01 (found in the mature cortical cells of Allium cepa roots) is not unusual. The plasmodesmata constitute the pathway of least resistance for the diffusion of all small solutes. Diffusion will be the predominant mechanism of transport across the pores for small solutes. Solute distribution within the bulk cytoplasm of each cell ought to be by a combination of self diffusion and cyclosis. There ought to be nearly perfect mixing within the bulk cytoplasm of each cell. In the course of the symplastic transport of solutes in the steady state there can be a significant coupling of water transport under proper conditions. The concentration drop of salts between adjacent cortical cells of onion roots necessary to transport all the observed salt flux into the xylem is 0·1 mn per cell or about 1 mn over the entire width of the cortex.

High mitotic synchronization induced by 5-aminouracil in root cells of Allium cepa L

A high degree of synchronization of cell division with a mitotic index up to over 80 was obtained by a 24 hr treatment of a low concentration of 0.8 M (100 ppm) 5-aminouracil followed by a 15 min treatment of 1.0 m M (250 ppm) thymidine. This high efficiency of obtaining synchronization of cell division is caused by the great effectiveness of 5-aminouracil to induce a block in the mitotic cycle of the onion.