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1.
Two clones of Pinnularia brebissonii (Kütz.) Rabh. var. brebissonii were established and maintained in logarithmic phase of growth. Initial length of the cells was 37 μm. As cell division occurred, the mean length of cells in each population decreased as predicted by the MacDonald-Pfitzer hypothesis; however, the decrease in mean length was not uniform throughout the growth period. This nonuniformity is probably caused by nonrandom division of cells in the population or by a changing increment of size reduction due to division. The initial increment of size reduction was calculated as 0.7 μm/division. The smallest, cells observed were 8 μm long. As cells decrease in length, cell volume decreases and the proportion of cells with aberrant valve structure increases. More than 90% of the valves were abnormal in a population with mean length of 14 μm. The abnormalities of structure involved the raphe, the central area and the striae. 相似文献
2.
Dott. Alessandro Marcello 《Plant biosystems》2013,147(2):402-434
Abstract A study on the type and distribution of trichomes, morphological traits of the calyx and content of antioxidant compounds was conducted on Teucrium arduini L. populations in Croatia and in Bosnia and Herzegovina. Non-glandular trichomes, peltate trichomes and small capitate trichomes with four secretory head cells were observed on leaves, stems and calyx, whereas long capitate trichomes with a unicellular head cell were observed exclusively on the calyx. Average calyx length was 5.23–6.51 mm, calyx tube length 2.92–3.68 mm, lower lip length 1.25–2.42 mm and upper lip length 1.89–2.99 mm. The concentration of antioxidant compounds in all populations was the highest in leaves: total polyphenols (TP): 8.43–13.55%; tannins (T): 1.79–7.33%; flavonoids (TF): 0.28–0.40%; phenolic acids (TPA): 2.90–5.07%. Inflorescences generally contained the smallest amount of TP (5.89–11.42%), T (0.87–6.50%) and TPA (1.66–2.27%), while the smallest content of TF was obtained for the majority of stem samples (0.06–0.12%). The researched populations did not differ with regard to the type and overall distribution of the trichomes, though the Bosnian populations have a shorter calyx tube and longer upper lip. Some variability was observed in the TP and T content between sampling sites, while quite high variability was noted in the TF and TPA content. 相似文献
3.
Most cells experience an active and variable fluid environment, in which hydrodynamic forces can affect aspects of cell physiology including gene regulation, growth, nutrient uptake, and viability. The present study describes a rapid yet reversible change in cell morphology of the marine dinoflagellate Ceratocorys horrida Stein, due to fluid motion. Cells cultured under still conditions possess six large spines, each almost one cell diameter in length. When gently agitated on an orbital shaker under conditions simulating fluid motion at the sea surface due to light wind or surface chop, as determined from digital particle imaging velocimetry, population growth was inhibited and a short‐spined cell type appeared that possessed a 49% mean decrease in spine length and a 53% mean decrease in cell volume. The reduction in cell size appeared to result primarily from a 39% mean decrease in vacuole size. Short‐spined cells were first observed after 1 h of agitation at 20°C; after 8 to 12 d of continuous agitation, long‐spined cells were no longer present. The morphological change was completely reversible; in previously agitated populations devoid of long‐spined cells, cells began to revert to the long‐spined morphology within 1 d after return to still conditions. During morphological reversal, spines on isolated cells grew up to 10 μm·d?1. In 30 d the population morphology had returned to original proportions, even though the overall population growth was zero during this time. The reversal did not occur as a result of cell division, because single‐cell studies confirmed that the change occurred in the absence of cell division and much faster than the 16‐d doubling time. The threshold level of agitation causing morphology change in C. horrida was too low to inhibit population growth in the shear‐sensitive dinoflagellate Lingulodinium polyedrum. At the highest level of agitation tested, there was negative population growth in C. horrida cultures, indicating that fluid motion caused cell mortality. Small, spineless cells constituted a small percentage of the population under all conditions. Although their abundance did not change, single‐cell studies and morphological characteristics suggest that the spineless cells can rapidly transform to and from other cell types. The sinking rate of individual long‐spined cells in still conditions was significantly less than that of short‐spined cells, even though the former are larger and have a higher cell density. These measurements demonstrate that the long spines of C. horrida reduce cell sinking. Shorter spines and reduced swimming would allow cells to sink away from turbulent surface conditions more rapidly. The ecological importance of the morphological change may be to avoid conditions that inhibit population growth and potentially cause cell damage. 相似文献
4.
The nuclear cytology of 9 strains of Sirogonium is described. The interphase nucleus contains 1–3 nucleoli, a nucleolar-organizing track, and many (>100) chromocenters. During the division cycle the nucleoli are transformed into a nucleolar substance which becomes associated with the chromosome and is transported through mitosis on the chromosomes. All strains possess minute dot chromosomes varying in length at metaphase from 0.5 to 1.5 μ; satellite chromosomes are 2.5–3.5 μ long. The number of chromosomes varies from 48 ± 2 to 100 ± 2. No evidence of centromeric activity was observed. 相似文献
5.
Alberto Amato Luisa Orsini Domenico D'Alelio Marina Montresor 《Journal of phycology》2005,41(3):542-556
Pseudo‐nitzschia delicatissima (Cleve) Heiden is a very common pennate planktonic diatom found in temperate marine waters, where it is often responsible for blooms. Recently, three distinct internal transcribed spacer types have been recorded during a P. delicatissima bloom in the Gulf of Naples (Mediterranean Sea, Italy), which suggests the existence of cryptic diversity. We carried out mating experiments with clonal strains belonging to the most abundant internal transcribed spacer type. Pseudo‐nitzschia delicatissima is heterothallic and produces two functional anisogametes per gametangium. The elongated auxospore possesses a transverse and a longitudinal perizonium. The sexual phase was observed to occur over a wide size spectrum, spanning 19–80 μm and corresponding to almost the whole range of cell length observed for P. delicatissima. We also investigated cell morphology, valve ultrastructure and morphometry of parental, F1‐generation strains, and the progeny of crosses between parental and F1 strains. Although ultrastructural features match those described for P. delicatissima, variability in cell shape was recorded in the largest cells of the F1 generation as well as in valves with an abnormal arrangement of poroids. As many other diatoms, P. delicatissima undergoes size reduction over its life cycle, and cells of different size showed differences in growth rates and the amount of size reduction per cell cycle. Cells between 60 and 30 μm in length showed the fastest growth and the slowest rates of size reduction per generation. In culture, P. delicatissima cells can decrease to 8 μm in length; however, such small cells (≤30 μm) are not recorded in the sea, and this raises interesting questions about the factors that control their survival in the natural environment. 相似文献
6.
Biofilm formation by bacterial cells can be used to modify the subsurface permeability for the purpose of microbial enhanced
oil recovery, bio-barrier formation, and in situ bioremediation. Once injected into the subsurface, the bacteria undergo starvation due to a decrease in nutrient supply and
diffusion limitations in biofilms. To help understand the starvation response of bacteria in biofilms, the relationship between
exopolymer formation and cell culturability was examined in a batch culture. The average cell diameter was observed to decrease
from 0.8 μm to 0.35 μm 3 days after starvation began. Cell chain fragmentation was also observed during starvation. Cells
that underwent starvation in the presence of insoluble exopolymers showed a slower rate of decrease in cell diameter and in
cell chain length than cells without insoluble exopolymers. The rate of decrease in the average cell diameter and cell chain
length were determined using a first order decay model. Cells starved in the presence of exopolymers showed greater culturability
than cells starved without exopolymers. After 200 days starvation, 2.5 × 10−3% cells were culturable, but no increase in cell number was observed. During starvation, the exopolymer concentration remained
constant, an indication that the exopolymer was not consumed by the starving bacteria as an alternative carbon or energy source.
Received: 8 April 1999 / Received revision: 16 July 1999 / Accepted: 6 August 1999 相似文献
7.
Several environmental parameters influence the ability of Stauroneis anceps Ehr. to survive periods of dehydration to equilibrium with atmospheric humidity. Cells grown in soil-water are better able to survive desiccation than cells grown in defined medium and cells from older cultures survive better than those from young cultures. Since active culture growth and cell division do not hinder survival, the factor responsible for increased survival in older cultures may be the accumulation of secreted metabolites in the medium. There is no survival when drying occurs in artificial substrata with particles 50 microns or less in diameter. Survival occurs when the particulate matter is 100 microns or larger. Slow drying seems to enhance survival, perhaps by allowing cells to interact longer with environmental organic substances conferring some degree of protection. Desiccated cells are better able to withstand temperature extremes than are vegetative cells in an aqueous environment. Dry cells survived longer than 9 days at 60 C and longer than 8 hr at 80 C but normal cultures were unable to survive 1 hr at 60 C. Temperatures of —15 to —20 C were also sustained more consistently by desiccated cells. Cells stored at vapor pressure deficits of 11.9 mm Hg or higher survived longer than 16 months but storage at 5.9 mm Hg or lower reduced survival time. 相似文献
8.
The effects of various chemotherapeutic agents on the volume of Chinese hamster V79 fibroblasts and murine lymphoma L5178Y cells were studied by electronic volume spectroscopy. Cells arrested in the division cycle by a chemotherapeutic block continued to grow in volume resulting in abnormally large cells unable to reduce their volume by cell division. This was observed in cells treated with colcemid, vinblastine, excess thymidine, hydroxyurea, ARA-C, 5-fluorouracil, actinomycin-D and bleomycin, but not with puromycin or cycloheximide. Increase in cell volume of blocked cells was correlated with a decrease in cell survival as measured by clonogenic ability. The results suggest the possibility of volume spectroscopy for a rapid in vitro test to determine tumor sensitivity to chemotherapeutic agents and the in vivo monitoring of response to chemotherapy. Mechanisms for increased cell kill by a second agent acting selectively on enlarged cells are considered. 相似文献
9.
Arun Shanker Narain 《Journal of morphology》1972,137(1):63-69
The formed elements of the blood of L. corrianus are comprised exclusively of amoebocytes, whose total number is approximately 758 per cubic mm of blood. The blood cells are of three types, viz. acidophils, large basophils and small basophils, which are respectively 26.32%, 60.20% and 13.48% of the total blood cell population. The cytoplasm of the acidophils is filled with large acidophilic granules, while that of the basophils contains fine basophilic granules. Acidophils are the largest (7.6 μ × 6.7 μ), large basophils are smaller (6.5 μ × 4.9 μ), and small basophils are the smallest (4.1 μ × 3.8 μ). The nucleus occupies a very small volume of the cell (approx. 1/9th) in acidophils, a larger volume (approx. 1/4th) in large basophils, and a major volume (approx. 3/4th) in small basophils. The blood cells show amoeboid movement, which is brought about by means of broad lamellate pseudopodia. Large basophils move very slowly, acidophils move faster, and small basophils move quite fast. Fine bristle-like filipodia help the blood cells in getting entangled to form clumps. Filipodia are more abundant in large basophils and acidophils which pertake more actively in clumping than small basophils which rarely possess filipodia. Clumping is a reversible process which is promoted by mechanical agitation of blood. 相似文献
10.
The coarse of growth and cell division in synchronized cultures of Chlorella pyrenoidosa was studied after the addition of metabolic inhibitors at differing times during the cell cycle (14 h light - 10 h darkness with nitrate as nitrogen source. 12 h light: 12 h darkness with urea as nitrogen source). Dinitrophenol (DNP) added to a final concentration of 0.3 mM at any time in the synchronization cycle, the compound remaining in the suspension from the time of addition to the end of the dark period, inhibited spore formation completely. Growth measured as increase in cell volume was less sensitive to the action of the inhibitor. Chloramphenicol (CAP) added dining the 0–5 h interval to a final concentration of 0.1 mM resulted in 80 per cent inhibition of cell division. Similar treatment started at successive times thereafter resulted in a gradual decrease of the inhibition. Treatment at the 14th hour and during the dark period did not affect the sporulation. Similar experiments with 0.9 mM puromycin added at various times during the illumination period gave almost complete inhibition of cell division, while the growth was reduced by only 25 per cent. para-Fluorophenylalanine (p-FPhe) at 3.3 × 10?2 mM stopped cell division nearly completely irrespective of addition time in the light period. Addition during the dark period also prevented an increase in the number of tree cells. In this case about half of the cells produced spores which were not released. It is concluded that DNP inhibits all stages of preparation for cell division, as well as the division process itself. With CAP a genuine transition point of preparation for cell division was observed, although its interpretation as related to protein synthesis is somewhat uncertain. With puromycin and p-FPhe no transitions were observed. 相似文献
11.
In the root epidermis of Hydrocharis morsus-ranae L. distinctive trichoblasts, which later grow out as root hairs, are formed by the unequal division of protodermal (immature epidermal) cells. The trichoblast is the more proximal product of this division. Trichoblasts differ from adjacent epidermal cells in manner of growth, in size, amount of cytoplasm, degree of succinic dehydrogenase and cytochrome oxidase activity, and in the structure of their plastids. Plastids in the trichoblasts gradually become colorless and of less complex structure with increasing distance from the root tip, in contrast to those in adjacent epidermal cells. The trichoblasts do not divide, but they elongate to a considerable extent in the most distal 3000 μ of the root tip and less extensively in the next 3000 μ. By contrast the sister cells and their products divide, but the individual products do not become markedly longer than the mother cell until situated more than 3000 μ from the root tip, when they undergo extensive elongation. The trichoblasts are thus characterized by delayed maturation and inhibition of cytokinesis; it is suggested that delayed maturation is a necessary prerequisite for differentiation of root hairs in this and other species. 相似文献
12.
The effects of N2, nitrate and ammonia as N sources were investigated in P-limited and nutrient-sufficient cultures of Anabaena flos-aquae (Lyngb.) Bréb. The maximum growth rate (μm) was highest at 1.34 d?1 with ammonia, compared to 1.18 with nitrate and 0.95 d?1 with N2. There was no difference in P requirement between N2 and nitrate cultures. Under P-limited conditions, the increase in cell P with growth rate (μ) was identical. With N2 as the N source, cell-N concentrations in P-limited cells increased with μ as did cell P, and the cellular N:P ratio remained the same (14) within the range of μ examined. With nitrate, however, cell N concentrations were high and independent of n, except at a low μ. It appears that this organism fixes atmospheric N2 only at the minimum concentration required to maintain a μ. The acetylene reduction rate increased with μ in both N2- and nitrate-grown cells, but the rate was lower in nitrate. Under P-limitation, there was no difference in net C-fixation rate per cell between N2 and nitrate cultures at a given μ. However, the rate per unit of chlorophyll a (chl a) was higher in N2 than in nitrate cultures, and the rate was independent of μ with N2 but was a linear function of nitrate supplied. The maximum C-fixation rate in nutrient sufficient cells was highest with ammonia, followed by nitrate and N2. The cellular chl a concentration was correlated with the total cell-N concentrations regardless of H and the source of N. 相似文献
13.
Michele D. DuRand Rebecca E. Green Heidi M. Sosik Robert J. Olson 《Journal of phycology》2002,38(6):1132-1142
Micromonas pusilla (Butcher) Manton et Parke, a marine prasinophyte, was used to investigate how cell growth and division affect optical properties of phytoplankton over the light:dark cycle. Measurements were made of cell size and concentration, attenuation and absorption coefficients, flow cytometric forward and side light scattering and chl fluorescence, and chl and carbon content. The refractive index was derived from observations and Mie scattering theory. Diel variations occurred, with cells increasing in size, light scattering, and carbon content during daytime photosynthesis and decreasing during nighttime division. Cells averaged 1.6 μm in diameter and exhibited phased division, with 1.3 divisions per day. Scattering changes resulted primarily from changes in cell size and not refractive index; absorption changes were consistent with a negligible package effect. Measurements over the diel cycle suggest that in M. pusilla carbon‐specific attenuation varies with cell size, and this relationship appears to extend to other phytoplankton species. Because M. pusilla is one of the smallest eukaryotic phytoplankton and belongs to a common marine genus, these results will be useful for interpreting in situ light scattering variation. The relationship between forward light scattering (FLS) and volume over the diel cycle for M. pusilla was similar to that determined for a variety of phytoplankton species over a large size range. We propose a method to estimate cellular carbon content directly from FLS, which will improve our estimates of the contribution of different phytoplankton groups to productivity and total carbon content in the oceans. 相似文献
14.
C. Ritchie Bell 《American journal of botany》1959,46(9):621-624
Bell , C. Ritchie . (U. of North Carolina, Chapel Hill.) Mineral nutrition and flower to flower pollen size variation. Amer. Jour. Bot. 46(9): 621–624. 1959.—Mineral nutrition appears to affect the amount of variability of pollen size in both clone and heterozygous seedling material grown on 6 different, deficient, nutrient solutions. In no case did the controls on complete nutrient solution have the largest mean pollen size. No pattern of pollen-size variation related to blooming date or to type of mineral deficiency could be detected in this experiment: the largest mean pollen size for tomato clone 1 came from plants on the —N solution, the smallest from plants on the –S solution (a 5.4 μ difference); for petunia clone 1, largest on –K, smallest on –S (a 2.3 μ difference); petunia clone 2, largest on –N, smallest on –P (a 1.9μ difference); dill set 1, largest on –K, smallest on –N (a 2.9μ difference); dill set 2, largest on –S, smallest on –N (an 8.2μ difference); portulaca (both sets presumably heterozygous) set 1, largest on –Mg, smallest on Ca (a 9.7μ difference); portulaca set 2, largest on –N, smallest on –Mg (a 13.6μ difference), note that set 1 was largest on –Mg. In the case of petunia pollen, there was greater size variation from flower to flower on the same plant than between flowers from different plants of the same clone on different nutrient solutions. Such variation offers further proof of the danger of using pollen size as an indicator of polyploidy or as a taxonomic characteristic until such correlations have been proven, in each separate instance, to be valid. 相似文献
15.
B. M. Prüß 《Archives of microbiology》1998,170(3):141-146
Carbon sources that can be converted to acetate were added to the growth medium of Escherichia coli wild-type cells. Cells responded with an increased cell division rate. The addition of acetate also caused a decreased synthesis
of flagella. Mutants in phosphotransacetylase, which are incapable of synthesizing acetyl phosphate, and mutants in the osmoregulator
OmpR divided at a lower rate than did wild-type cells. The mutants did not increase their cell division rate upon the addition
of serine, as observed for wild-type cells. These data are consistent with the idea that the previously described effect of
serine upon the cell division rate is mediated by acetyl phosphate and phosphorylation of OmpR.
Received: 23 March 1998 / Accepted: 8 May 1998 相似文献
16.
The age-dependent, ultraviolet light (UVL) (254 nm)-induced division delay of surviving and nonsurviving Chinese hamster cells was studied. The response was examined after UVL exposures adjusted to yield approximately the same survival levels at different stages of the cell cycle, 60% or 30% survival. Cells irradiated in the middle of S suffered the longest division delay, and cells exposed in mitosis or in G1 had about the same smaller delay in division. Cells irradiated in G2, however, were not delayed at either survival level. It was further established, after exposures that yielded about 30% survivors at various stages of the cycle, that surviving cells had shorter delays than nonsurvivors. This difference was not observed for cells in G2 at the time of exposure; i.e., neither surviving nor nonsurviving G2 cells were delayed in division. The examination of mitotic index vs. time revealed that most cells reach mitosis, but all of the increase in the number of cells in the population can be accounted for by the increase of the viable cell fraction. These observations suggest strongly that nonsurviving cells, although present during most of the experiment, are stopped at mitosis and do not divide. Cells in mitosis at the time of irradiation complete their division, and in the same length of time as unirradiated controls. Division and mitotic delays after UVL are relatively much larger than after X-ray doses that reduce survival to about the same level. 相似文献
17.
E. Gantt 《Journal of phycology》1971,7(3):177-184
An ultrastructural examination of the periplast of Chroomonas sp. revealed a surface pattern composed of rows of plate areas. The plate areas are delineated by a series of ridges, which emanate from a common line at the posterior cell end, and lateral grooves which intersect the anterior-posterior ridges. Small ejectosomes (trichocysts) are generally located at the intersection of the lateral grooves and the ridges. Size of the plate areas varies, being smallest at the posterior and anterior ends and largest in the midregion of the cell. The average plate area is 1 μ in length and 0.7 μ in width. In section the periplast is seen to consist of 3 intimately attached layers of which the middle (plasma membrane) layer is continuous with the gullet region, flagella, and ejectosome chambers. Trypsin digestion resulted in the disappearance of the inner and outer layers, and in the loss of periplast stiffness. 相似文献
18.
Synchronously and normally grown Chlorella pyrenoidosa cell populations were analysed by countercurrent distribution in aqueous two-polymer phase systems and by a multiple sedimentatation technique. Partition of cells in aqueous phases reflects the surface properties of cells (primarily surface charge) and multiple sedimentation reflects the cells' size-density parameters. It was found that:
- 1. 1. Synchronized cells that have just divided have the lowest partition of any in the population. Surface charge (as reflected by partition) increases with time after cell division. Cells have the highest partition just prior to division.
- 2. 2. Synchronized cells that have just divided are the smallest of any in the population. Since size and sedimentation rate increase with time after cell division multiple sedimentation permits the separation of cells of different ages.
- 3. 3. Both countercurrent distribution and multiple sedimentation studies reveal considerable heterogeneity of synchronized Chlorella populations. The increase in both surface charge and size with cell age does not appear to proceed in a continuous fashion. Rather, it seems to go in a stepwise manner.
- 4. 4. Non-synchronized cells examined by either countercurrent distribution or multiple sedimentation show two distinct sub-populations. One of these corresponds to the youngest, just divided cells; and the other to cells just prior to cell division. It is suggested that a lag time just prior to cell division and just after cell division explains these results.
- 5. 5. Countercurrent distribution in two-polymer phases and multiple sedimentation at unit gravity in a suspension medium best suited for the cell under investigation seem to be methods of choice for tracing cell changes during division, maturation and aging and for sub-fractionating such cell populations.
19.
N G Maroudas 《Experimental cell research》1973,81(1):104-110
BHK and 3T3 cells were grown on small glass fibres and platelets (size range 20–250 μm) in agar gel, over a layer of mouse primary feeder cells. Under these conditions the growth of colonies (4–20 cells) from single control cells, suspended freely in the gel, was less than 1 %, while cells attached to the larger platelets yielded more than 95 % colonies. Fibres (average diameter 0.625 μm) induced somewhat fewer colonies (45–70 %). However, there was a significant induction of single divisions by fibres as short as 30 μm, while on 60 μm fibres more than half the cells had gone through at least one division, compared with 4–12% of freely suspended controls. Longer fibres promoted multiple divisions. Colony formation increased sigmoidally with fibre length from 30 to 250 μm, with a d50 around 115 μm. These figures resembled the observed range of lengths of freely growing BHK and 3T3 fibroblasts in tissue culture dishes. In another experiment, finer fibres (average diameter 0.075 μm) performed almost as well as platelets of equal length but of width 20–30 μm.Thus linear extension provides a stimulus for division of anchorage-dependent fibroblasts. It is suggested that this stimulus may arise from a change in conformation or tension in the cell membrane, rather than from increased surface, cell motility or interaction with substrate surface.The present results are discussed in relation to recent findings on the induction of tumours by solid particles. 相似文献
20.
Marvin W. Fawley 《Journal of phycology》1984,20(1):67-72
Cell division rate, carbon fixation per cell, cell width and chloroplast length of Phaeodactylum tricornutum Bohlin were determined at 30 different combinations of light intensity and temperature. Division rate peaked at 23° C or less depending on light intensity. For each light intensity studied, carbon fixation increased directly with growth temperature from 14 to 25° C. The slope of this relationship was modified by light intensity. Cells grown at 23–25° C tended to be larger than those grown at lower temperatures, possibly due to increased carbon fixation per cell coupled with lower division rates. Chloroplasts were largest at a combination of temperatures above 21° C and low light intensities. This effect could cause cells to sink at a higher than normal rate due to reduced vacuole size and is presented as a possible mechanism affecting the distribution of P. tricornutum. 相似文献