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  • 1
    Electronic Resource
    Electronic Resource
    Simulated weightlessness and hyper-g results in opposite effects on the regeneration of the cortical microtubule array in protoplasts from Brassica napus hypocotyls (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 106 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Enzymatic digestion of the cell wall of Brassica napus hypocotyls gave a heterogeneous suspension of protoplasts with the cortical microtubules (CMTs) randomly organised or CMTs organised in parallel. The effect of variable g-influences has been tested on CMT organisation. In contrast to the 1 g-protoplasts, which reorganised the CMTs into parallel arrays during the 96 h test period, the frequency of randomly-oriented CMTs in the protoplasts exposed to simulated weightlessness (0 g) on a 2-D clinostat increased significantly during the same period. The opposite effect was obtained when the protoplasts were exposed to hyper-g (7 or 10 g), where the reorganisation of the CMTs into parallel arrays was accelerated compared to the 1 and 0 g-protoplasts. These results indicate that a unidirectional gravity force is a necessity for the reorganisation of CMTs in protoplasts to parallel arrays and that CMTs act as responding elements that are able to sense different levels of gravity. Besides the inability of the protoplasts to reorganise the CMTs into parallel arrays, the quantity of CMTs in the individual protoplast decreased during 4 days of simulated weightlessness, both compared to the CMTs quantity in the protoplasts immediately after isolation and compared to the 1 g- and hyper-g-protoplasts after 24 and 48 h of g-exposure. The size of the protoplasts was also affected by the g-exposure. Protoplasts exposed to simulated 0 g increased significantly after 24 and 48 h, whereas the 1 g- and 10 g-protoplasts maintained the same size during the 48 h test period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.106309.x
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  • 2
    Electronic Resource
    Electronic Resource
    Random root movements in weightlessness (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 96 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The dynamics of root growth was studied in weightlessness. In the absence of the gravitropic reference direction during weightlessness, root movements could be controlled by spontaneous growth processes, without any corrective growth induced by the gravitropic system. If truly random of nature, the bending behavior should follow socalled ‘random walk’ mathematics during weightlessness. Predictions from this hypothesis were critically tested.In a Spacelab ESA-experiment, denoted RANDOM and carried out during the IML-2 Shuttle flight in July 1994, the growth of garden cress (Lepidium sativum) roots was followed by time lapse photography at 1-h intervals.The growth pattern was recorded for about 20 h. Root growth was significantly smaller in weightlessness as compared to gravity (control) conditions.It was found that the roots performed spontaneous movements in weightlessness. The average direction of deviation of the plants consistently stayed equal to zero, despite these spontaneous movements. The average squared deviation increased linearly with time as predicted theoretically (but only for 8–10 h).Autocorrelation calculations showed that bendings of the roots, as determined from the 1-h photographs, were uncorrelated after about a 2-h interval.It is concluded that random processes play an important role in root growth. Predictions from a random walk hypothesis as to the growth dynamics could explain parts of the growth patterns recorded. This test of the hypothesis required microgravity conditions as provided for in a space experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00198.x
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  • 3
    Electronic Resource
    Electronic Resource
    The growth and gravitropic responses of wild-type and auxinresistant mutants of Arabidopsis thaliana (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 60 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth and gravitropism have been studied in three mutant strains of Arabidopsis thaliana L, that are resistant to auxin-herbicide. Two of the mutations are allelic and recessive (aux-1 and aux-2) and are unlinked to a dominant mutation, Dwf, which confers a very high level of auxin-resistance and is apparently lethal when homozygous. The aux-1 and Dwf strains have altered response to gravity whereas aux-2 appears to be gravitropically normal.After 96 h in the normal, vertical position only minor differences in elongation were observed between roots of wild-type, aux-1 and aux-2, but the hypocotyls of aux-1 were significantly retarded compared with the gravitropically normal aux-2 and wild-type. In the progeny of selfed Dwf plants, where both normal (dwf) and agravitropic (Dwf) seedlings are present, the Dwf seedlings had much longer roots and shorter hypocotyls than dwf+. During 22 h of continuous stimulation the optimum angle for gravitropism in wild-type roots and hypocotyls was 135° (i.e. the organ points obliquely upwards), with decreasing responses in the order 90° and 45°. The agravitropic nature of the roots of aux-1 was confirmed as no significant response was obtained at any of the stimulation angles. In marked contrast, the negative gravitropic response of aux-1 hypocotyls was greater than the wild-type response in terms of the final angle attained at 22 h, but between 6 and 22 h the elongation rate was lower in aux-1. After varying stimulation periods in the horizontal position, the curvature which had developed, decreased rapidly and almost disappeared during ensuing rotation on clinostats (2 and 4 rpm). Rotation on the clinostats had no effect on the agravitropic behaviour of aux-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04920.x
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  • 4
    Electronic Resource
    Electronic Resource
    The Geotropic Curvature in Roots of Norway Spruce (Picea abies) Containing Anthocyanins (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 37 (1976), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seedlings of Norway spruce (Picea abies L.) have been found to synthesize anthocyanins in the root tips as well as in the hypocotyls upon irradiation with white light when kept at 4°C for 6–8 days. In addition, it has also been found that the elongation and the geotropic curvature of spruce roots are dependent on the light conditions.The course of the geotropic curvature in spruce roots containing anthocyanins has been followed during a period of 5 h, in which the seedlings were geotropically stimulated continuously in the horizontal position. When the stimulation was performed in white light and in darkness at 21°C, significantly larger curvatures were observed in the roots pretreated at 4°C in darkness than in the roots containing anthocyanins. The specific curvature (curvature in degrees per mm elongation), however, was approximately the same in both types of roots stimulated in white light. This was due to a retarded elongation of the roots pretreated with light at 4°C and containing anthocyanins. A smaller difference in elongation rate between roots with and without anthocyanins was observed in the dark than in the light, but even in the dark the anthocyanin-containing roots grew more slowly than roots without anthocyanins.In order to find out if it is the anthocyanin content or the illumination which affects the elongation and geotropic curvature in the roots, a series of similar experiments was performed using cress seedlings grown at 4°C in light or darkness. Roots of cress seedlings cultivated under conditions which would induce anthocyanin formation in spruce roots exhibited the highest geotropic responses both in light and darkness as compared to cress seedlings grown at 4°C in darkness.As in the case of spruce roots an increase in elongation was observed in cress roots illuminated during the geotropic stimulation. These similarities in the behaviour made it relevant to compare the development of the geotropic curvature in cress and spruce roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1976.tb03971.x
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  • 5
    Electronic Resource
    Electronic Resource
    Movement of Amyloplasts in the Root Cap Cells of Geotropically Sensitive Roots (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 21 (1968), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The root cap of Lepidium sativum under our culture conditions was found to contain 7 (or occasionally 8) storeys of starch-containing cells. In the youngest one (or two) of these storeys the amyloplasts are small and the cells appear embryonic. In the 6 non-embryonic storeys the amyloplasts are large. Upon inversion of the root, the amyloplasts in the 3 youngest of the 6 non-emhryonic storeys start falling toward the opposite end of the cell at about 72 μ per h (at 21 C), hut they maintain this speed for only 6 to 12 min, after which they virtually come to a stop. As a result, it takes 10 to 12 min before any of the amyloplasts get approximately as close to the ceiling as they were to the floor before the inversion; and this is true only of the 2 youngest of the non-embryonic storeys. When the root is placed horizontal, whether coming from the normal or the inverted position, the amyloplasts reach the lower, longitudinal wall in 15 min or less. The positions of the amyloplasts in the cells of the 3 oldest starch-containing storeys are erratic and show little, if any, dependency on the preceding time of inversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1968.tb07305.x
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  • 6
    Electronic Resource
    Electronic Resource
    Decarboxylation and Transport of Auxin in Segments of Sunflower and Cabbage Roots. II. A Chromatographic Study Using IAA-1-14C and IAA-5-3H (1971)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 24 (1971), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The polar movement of IAA has been examined in 5-mm root segments of Brassica oleracea and Helianthus annum. The movement was studied partly with IAA-1-14C and partly with IAA-5-3H. In both plants a slight acropetal flux of 14C and IAA-3H was found through the segments. The recovered radioactivity in the agar receiver blocks and in the receiver end of the segments increased as a function of time.A large portion of the applied IAA was converted on the cut surfaces and in the tissues of the segments. Chromatographic analysis indicated different destruction products when estimated by scintillation counting and by spraying with in-dole reagent (DMCA).Chromatograms run in isopropanol: ammonia: water, 8:1:1, yielded three different substances, one spot near the starting line and one near the front, neither of which has been identified. Finally there was a spot with Rf 0.4–0.6, probably representing IAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1971.tb03498.x
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure and movements of cell structures in normal pea and an ageotropic mutant (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 50 (1980), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The pea mutant (Pisum sativum ageotropum) and the normal pea (P. sativum cv. Sabel) were compared in order to see if there were any differences in root anatomy or submorphology which could explain the presumed ageotropic behaviour of the mutant. In both types the root cap consists of a central core (columella) distinct from the peripheral part. The core contains five to six rows of columella cells, each consisting of 10 to 16 storeys of statocytes. The ultrastructure of the columella cells in the two types is very similar; the main difference is confined to the distribution of rough endoplasmic reticulum (ER), which in the mutant statocytes is evenly distributed throughout the cell, while in the normal pea statocytes it is mainly concentrated in the distal part at the “floor” of the cell.Using light micrographs, the movement of amyloplasts and nuclei have been followed in detail during a 40 min inversion period. The pattern of movement of the amyloplasts is apparently identical in the two types and the distances moved during the inversion period are 39 μm and 44 μm in the normal and mutant statocytes, respectively. The nucleus has not been observed to move in normal pea; a slight rearrangement of the nucleus position can be observed during the period 30 to 40 min after the start of inversion of the mutant.Based on magnified electron micrographs of the statocytes a morphometrical analysis was made of five cell structures – amyloplasts, nuclei, mitochondria, vacuoles and ER – which appeared to be freely movable or redistributable under the influence of the gravitational force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1980.tb04463.x
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  • 8
    Electronic Resource
    Electronic Resource
    Movement of Cell Organelles and the Geotropic Curvature in Roots of Norway Spruce (Picea abies) (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 42 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The geotropic development in roots of Norway spruce [(Picea abies (L.)] H. Karst, has been followed by light and electron microscopy and compared with the movement of cell organelles (statoliths) in the root cap cells. The geotropic curvature develops in two phases: (a) an initial curvature in the root cap region, which results in an asymmetry in the extreme root tip and which appears after about 3 h stimulation in the horizontal position; and (b) the geotropic curvature in the basal parts of the root tip, which after 8 h is distributed over the entire elongation zone. A graphic extrapolation, based on measurements of the root curvatures after various stimulation periods, indicates a presentation time in the range of 8 to 10 min.The root anatomy and ultrastructure have been examined in detail in order to obtain information as to which organelles may act as gravity receptors. The root cap consists of a central core (columella) distinct from the peripheral part. The core contains three to four rows of parenchymatic cells each consisting of 15 to 18 storeys of statocyte cells with possibly mobile cell organelles. Amyloplasts and nuclei have been found to be mobile in the root cap cells, and the movement of both types of organelles has been followed after inversion of the seedlings and stimulation in the horizontal position for various periods of time at 4°C and 21°C. Three-dimensional reconstructions of spruce root cap cells based on serial sectioning and electron microscopy have been performed. These demonstrate that the endoplasmic reticulum (ER)-system and the vacuoles occupy a considerable part of the statocyte cell. For this reason the space available for free movement of single statolith particles is highly restricted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb04105.x
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  • 9
    Electronic Resource
    Electronic Resource
    Geotropic Curvatures in Roots of Cress (Lepidium sativum) (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 28 (1973), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Roots of cress growing between two agar slices develop an asymmetry in the extreme root tip region after 10 to 20 min of horizontal stimulation. After prolonged stimulation (exceeding 50 min) the asymmetry disappears and after 3 h the curvature is distributed over the entire growing region. The course of the initial stages in the geotropic curvature has been followed by light microscopy and scanning electron microscopy. — When stimulated at an angle of 135° with the gravitational force, the asymmetry in the root tip is clearly visible after 10 min of stimulation.The asymmetry in the root cap can be explained by a difference in the elongation rate of the epidermal cells on the upper and lower sides of the stimulated root. The disappearance of the asymmetry is followed by a second phase in which there is a differential growth of the cortical cells on the two sides of the elongation zone. The average growth rate of cells in the upper half of the apical region during the first 50 min of continuous stimulation is 1.5 μm per min, while the elongation rate of the entire root is 16.2 μm per min. Only small modifications in the elongation rates were observed when stimulated and unstimulated roots were rotated parallel to the horizontal axis of a klinostat at 2 rpm.The ultimate curvature developed after 50 min is unaffected by stimulation times exceeding the reaction time which for cress roots has been found to be about 5 min.The two phases in the development of geotropic curvature are discussed in view of the statolith theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1973.tb01197.x
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  • 10
    Electronic Resource
    Electronic Resource
    Preparatory studies for the use of plant protoplasts in space research (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 76 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An experiment using plant protoplasts has been accepted for the IML-1 mission to be flown on a space shuttle in 1991. Preparatory experiments include studies of cell wall formation, cell division, the effect of simulated weightlessness using fast and slow rotating clinostats, and the development and testing of hardware for the IML-1 mission. After 24 h at 25°C, protoplasts isolated from hypocotyls or leaves of rapeseed seedlings, or from carrot suspension cells, show 60, 20 and 15% cell wall formation, respectively. The time course of formation of the cell wall and cell division could be delayed by treatment at low temperatures or immobilization in alginate or agarose. This aspect is of importance in connection with problems of late access to the space shuttle before launch. At 4°C only 18% of the rapeseed hypocotyl protoplasts had formed cell walls after 24 h. Protoplasts immobilised in agarose or alginate gradually regain their cell division capacity and after 72 h the frequencies are 51 and 26%, respectively, compared to non-immobilised control protoplasts. A significant decrease in cell division activity is observed after rotation for 6 h on the slow clinostat. A similar effect is not observed on the fast clinostat. Protoplasts, cultured in the specially designed plant chamber for up to 14 days established cell aggregates which have further developed into plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb06215.x
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