1
|
Volkmann D, Tewinkel M. Gravisensitivity of cress roots: investigations of threshold values under specific conditions of sensor physiology in microgravity. PLANT, CELL & ENVIRONMENT 1996; 19:1195-1202. [PMID: 11539327 DOI: 10.1111/j.1365-3040.1996.tb00435.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The minimum dose (dose = stimulus x time), one of three threshold values related to gravity, was determined under microgravity conditions for cress roots. Seedlings were cultivated on a 1g centrifuge in orbit and under microgravity, respectively. After continuous stimulation on a threshold centrifuge, minimum doses of 20-30 gs for microgravity roots and 50-60 gs for roots grown on a 1g centrifuge were estimated, which indicated that microgravity roots have a higher sensitivity than 1g roots. These results do not confirm the threshold value of 12gs which was determined for cress roots using the slow rotating clinostat. Following application of intermittent stimuli to microgravity-grown roots, gravitropic responses were observed after two stimuli of 13.5 gs separated by a stimulus-free interval of 118s. Generally, this demonstrates that higher plants are able to 'sum up' stimuli which are below the threshold value. Microscopic investigations of the cellular structure corresponding to stimulations in the range of the threshold value demonstrated a small displacement of statoliths in root statocytes. No significant correlation was observed between gravitropic curvature and statolith displacement. If the statolith theory is accepted, it can be concluded that stimulus transformation must occur in the cytoplasm in the near vicinity of the statoliths and that this transformation system--probably involving cytoskeletal elements--must have been affected during microgravity seedling cultivation.
Collapse
Affiliation(s)
- D Volkmann
- Botanisches Institut der Universitat Bonn, Germany
| | | |
Collapse
|
2
|
Abstract
During the spacelab mission IML-2 threshold values concerning gravity controlled growth processes have been estimated in order to test the reciprocity law (dose = stimulus x time = constant) for the first time under exact physiological conditions. Cress seedlings have been cultivated from dry seeds under conditions of microgravity and on a 1 x g-centrifuge in the ESA-BIORACK. With the help of NIZEMI--the slow rotating centrifuge microscope--these seedlings have been stimulated by different doses ranging from 12 to 60 x g x s. Two different values of acceleration--0.1 x g and 1 x g--have been used. Graviresponses of the roots have been documented by video recording for 60 min under conditions of microgravity. The response of roots to accelerations of 0.1 x g was remarkably less than to 1 x g in spite of the same doses being applied to the seedlings. Roots cultivated under conditions of microgravity showed a higher sensitivity than those grown on the 1 x g-centrifuge. Displacement of statoliths in gravity perceiving cells was mainly less than 1 micron under the different stimulation procedures. These results together with results from former space flights do not confirm the validity of the reciprocity law. They indicate that transformation of the gravistimulus has to occur in close vicinity to the statoliths, probably mediated by the ground cytoplasm and the cytoskeleton suspended therein.
Collapse
Affiliation(s)
- D Volkmann
- Botanisches Institut der Universität Bonn, Germany
| | | |
Collapse
|
3
|
Griffing LR. Comparisons of Golgi structure and dynamics in plant and animal cells. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1991; 17:179-99. [PMID: 2013820 DOI: 10.1002/jemt.1060170206] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The Golgi apparatus of both higher plant and animal cells sorts and packages macromolecules which are in transit to and from the cell surface and to the lysosome (vacuole). It is also the site of oligosaccharide and polysaccharide synthesis and modification. The underlying similarity of function of plant and animal Golgi is reflected in similar morphological features, such as cisternal stacking. There are, however, several fundamental differences between the Golgi of plant and animal cells, reflecting, in large part, the fact that the extracellular matrices and lysosomal systems differ between these kingdoms. These include 1) the form and replication of the Golgi during cell division; 2) the disposition of the Golgi in the interphase cell; 3) the nature of "anchoring" the Golgi in the cytoplasm; 4) the genesis, extent, and nature of membranes at the trans side of the stack; 5) targeting signals to the lysosome (vacuole); and 6) physiological regulation of secretion events (constitutive vs. regulated secretion). The degree of participation of the Golgi in endocytosis and membrane recycling is becoming clear for animal cells, but has yet to be explored in detail for plant cells.
Collapse
Affiliation(s)
- L R Griffing
- Department of Biology, Texas A&M University, College Station 77843
| |
Collapse
|
4
|
Grolig F, Wagner G. Characterization of the isolated calcium-binding vesicles from the green alga Mougeotia scalaris, and their relevance to chloroplast movement. PLANTA 1989; 177:169-177. [PMID: 24212339 DOI: 10.1007/bf00392805] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/1988] [Accepted: 09/29/1988] [Indexed: 06/02/2023]
Abstract
The calcium-binding vesicles from the green alga Mougeotia scalaris were isolated and characterized after staining in vivo by neutral red or rhodamine B. They were found to possess, a protonated group with a pKa-9.9, typifying phenolic hydroxyl groups; upon titration, both, phenolic compound(s) and vital dye were concomitantly released from the vesicular matrix. A shift in peak absorbance from 450 nm to 540 nm of the vitally stained vesicles indicated that the neutral form of neutral red was bound to the vesicular, matrix as an intermediate form, stabilized via intermolecular hydrogen bonds to the phenolic compound(s). Up to 8.5.10(9) dye molecules were calculated to be adsorbed to a mean-size vesicle. Analysis of Langmuir adsorption isotherms, indicated that there were two binding sites each for both neutral red and rhodamine B. The isolated vesicles were devoid of calcium, probably because vesicular calcium, bound to the vesicle matrix, was displaced upon dye binding. Dye adsorption to the vesicles in vivo results in substantial inhibition of the reorientational movement of the Mougeotia chloroplast and is explained by dye-mediated disorder of the cellular calcium homoeostasis.
Collapse
Affiliation(s)
- F Grolig
- Botanisches Institut I der Justus-Liebig-Universität, Senckenbergstrasse 17-25, D-6300, Giessen, Federal Republic of Germany
| | | |
Collapse
|
5
|
Staehelin LA, Chapman RL. Secretion and membrane recycling in plant cells: novel intermediary structures visualized in ultrarapidly frozen sycamore and carrot suspension-culture cells. PLANTA 1987; 171:43-57. [PMID: 24227269 DOI: 10.1007/bf00395066] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/1986] [Accepted: 01/22/1987] [Indexed: 05/18/2023]
Abstract
Freeze-fracture electron microscopy of propane-jet-frozen samples has been employed to investigate vesicle-mediated secretion and membrane recycling events in carrot (Daucus carota L.) and sycamore maple (Acer pseudoplatanus L.) suspension-culture cells. Stabilization of the cells by means of ultrarapid freezing has enabled us to preserve the cells in a turgid state and to visualize new intermediate membrane configurations related to these events. Indeed, many of the observed membrane configurations, such as flattened membrane vesicles with slit-shaped membrane fusion sites and horseshoe-shaped membrane infoldings, appear to result from the action of turgor forces on the plasma membrane. Individual cells exhibited great variations in numbers and types of membrane configurations postulated to be related to secretion and membrane-recycling events. In the majority of cells, the different membrane profiles displayed a patchy distribution, and within each patch the membrane configurations tended to be of the same stage. This result indicates that secretory events are triggered in domains measuring from 0.1 to about 10 μm in diameter. Based on an extensive analysis of the different membrane configurations seen in our samples, we have formulated the following model of vesicle-mediated secretion in plant cells: Fusion of a secretory vesicle with the plasma membrane leads to the formation of a single, narrow-necked pore that increases in diameter up to about 60 nm. During discharge, the vesicle is flattened, forming a disc-shaped structure perpendicular to the plane of the plasma membrane. As the vesicle is flattened, the pore is converted to a slit, the maximum length of which coincides with the diameter of the flattened vesicle. The flattened vesicle then tips over and concomitantly the plasma-membrane slit becomes curved into a horseshoe-shaped configuration as it extends along the outer margins of the tipped-over vesicle. Some coated pits are present interspersed between the above-mentioned structures, but their numbers appear insufficient to account for an exclusively endocytotic mechanism of membrane recycling. Instead, our micrographs are more consistent with a mixed mode of recycling of membrane components to the cortical endoplamic reticulum and to Golgi cisternae that involves both internalization of membrane by endocytosis and of individual lippid molecules by unknown mechanisms (lipid exchange proteins?). To this end, overall flattening out of the horseshoe-shaped membrane infoldings is accompanied by a retraction and reduction in size of their central, tongue-like structure.
Collapse
Affiliation(s)
- L A Staehelin
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Box 347, 80309, Boulder, CO, USA
| | | |
Collapse
|
6
|
Hensel W. A role of microtubules in the polarity of statocytes from roots of Lepidium sativum L. PLANTA 1984; 162:404-414. [PMID: 11541064 DOI: 10.1007/bf00393452] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
When roots of Lepidium sativum L. are immersed in a colchicine solution (10(-4) mol l-1, the cortical microtubules of statocytes are affected such that the dense network of microtubules at the distal cell edges, between the endoplasmic reticulum and the plasma membrane, disappears almost completely, whereas the microtubules, lining the anticlinal cell walls are reduced only to a limited extent. Upon inversion of colchicine-pretreated roots, the distal complex of endoplasmic reticulum sinks into the interior of the statocyte. Germination of seeds in the cold (3-4 degrees C) leads to a retardation of statocyte development; the elaborated system of endoplasmic reticulum is lacking, and only a few microtubules are observable, lining the plasma membrane along the anticlinal cell walls. During an additional 4 h at 24 degrees C, groups of microtubules develop near the plasma membrane in the distal one-third of the statocytes, coaligning with newly synthesized cisternae of the endoplasmic reticulum. It is proposed that, particularly at the distal statocyte pole, microtubules in coordination with cross-bridging structures, act in stabilizing the polar arrangement of the distal endoplasmic reticulum and, in turn, facilitate an integrated function of amyloplasts, endoplasmic reticulum and plasma membrane in graviperception.
Collapse
Affiliation(s)
- W Hensel
- Botanisches Institut der Universitat, Bonn, Federal Republic of Germany
| |
Collapse
|
7
|
Volkmann D. The plasma membrane of growing root hairs is composed of zones of local differentiation. PLANTA 1984; 162:392-403. [PMID: 24253221 DOI: 10.1007/bf00393451] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/1984] [Accepted: 05/03/1984] [Indexed: 06/02/2023]
Abstract
Growing root hairs of cress (Lepidium sativum L.) were investigated using freeze-fracture and electron-microscopic techniques. Three zones of differentiation could be detected: the tip zone, the zone of vacuolation and the foot zone. Corresponding to these zones, the plasmatic fracture face of the plasma membrane showed areas of pronounced differentiation with respect to the distribution and frequency of intramembranous particles (IMPs). The tip zone was characterized by an irregular fracture plane caused by a large number of blisters which were more or less free of IMPs. These blisters coincided in size and shape with Golgi vesicles accumulated in the ground cytoplasm near the very tip. Outside these blisters, IMPs were randomly distributed. The surrounding cell wall was very thin and mainly composed of amorphous material. The plasma membrane of the vacuolation zone often revealed areas of hexagonally ordered particles (HOPS). Such patterns of particles were observed in chemically fixed and unfixed root hairs with a maximum surface density of 1200 HOPS per area. Mostly, however, 15-50 HOPS per area were found. The number of such areas increased with increasing distance from the tip up to five areas per μm(2). Additionally, imprints of large cellulose microfibrils could be detected in unfixed material; they were mainly parallel to the root-hair axis and sometimes ended in areas of HOPS. However, HOPS were observed only in approximately 60% of the root hairs. Otherwise, large areas free of IMPs were interspersed between areas of randomly distributed IMPs. The particle frequency was relatively low and varied greatly in the tip as well as in the vacuolation zone, that is, from 1200 to 2000 IMPs μm(-2). Finally, the plasma membrane of the foot zone showed a very constant number of approx. 2000 IMPs μm(-2). These particles were mainly distinct and randomly distributed. In this zone, HOPS were never observed in spite of the fact that the cell wall was composed of numerous parallel-running cellulose microfibrils. Since membrane material is mainly incorporated in the tip zone where IMPs are statistically distributed, the results indicate that the plasma membrane of the outgrowing part of the root-hair cells is characterized by a high lateral mobility of its components. Furthermore, they indicate that specifically arranged particles are involved in the synthesis of cellulose microfibrils. These areas of HOPS seem to be locally restricted and - or limited with respect to their lifetime.
Collapse
Affiliation(s)
- D Volkmann
- Botanisches Institut der Universität, Venusbergweg 22, D-5300, Bonn 1, Federal Republic of Germany
| |
Collapse
|
8
|
Grim JN, Staehelin LA. The ejectisomes of the flagellate Chilomonas paramecium: visualization by freeze-fracture and isolation techniques. THE JOURNAL OF PROTOZOOLOGY 1984; 31:259-67. [PMID: 6470985 DOI: 10.1111/j.1550-7408.1984.tb02957.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Freeze-fracture procedures were used to visualize ejectisomes and adjacent plasma membrane specializations in the flagellate protozoan Chilomonas paramecium. The ejectisomes are membrane-bounded, cylindrically rolled, extrusive organelles. Small ones occur in large number beneath the plasma membrane of the body and considerably larger ones are located around the gullet membrane. The intra-membrane particle distribution is different in each type. In small ejectisomes, the portion of the membrane in contact with the plasma membrane of the body has a P-face rosette of five particles while the plasma membrane has not been observed with a rosette. Small ejectisomes and plasma membrane both contain aggregations of particles a short distance from the contact or docking site. Slightly beneath the plasma membrane is the periplastic sheet with which we speculate the small ejectisomes interact during the docking phenomenon. No obvious rosettes have been observed in large ejectisomes. Some other ejectisomal structures are presented and discussed.
Collapse
|
9
|
Hensel W. Microtubules in statocytes from roots of cress (Lepidium sativum L.). PROTOPLASMA 1984; 119:121-134. [PMID: 11540621 DOI: 10.1007/bf01287824] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Statocytes in root caps of Lepidium sativum L. were examined by means of ultrathin serial sections to evaluate the amount and distribution of cortical microtubules. The microtubules encircle the cell, oriented normal to the root length axis. In the distal cell edges, microtubules form a network, separating the distal complex of endoplasmic reticulum from the plasmalemma. Preprophase bands in meristem cells are observable rarely, structures which can be regarded as nucleating sites for microtubules are lacking. During ageing of the root cap cells, the number of microtubules increases in combination with a decrease of microtubule length. Development of the roots on a horizontal clinostat preserves a "younger" developmental stage of the microtubule system regarding amount and length of the individual microtubules. Evidence for an involvement of microtubules in graviperception is low, whereas their role in orienting cellulose microfibrils cannot be ruled out. Compression of the distal network of microtubules after centrifugation of the roots indicates that microtubules in statocytes of Lepidium sativum L. roots might function in stabilizing the distal complex of endoplasmic reticulum.
Collapse
Affiliation(s)
- W Hensel
- Botanical Institute, University of Bonn
| |
Collapse
|
10
|
Membrane Flow via the Golgi Apparatus of Higher Plant Cells. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/s0074-7696(08)62465-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
|
11
|
Volkmann D, Czaja AW. Reversible inhibition of secretion in root cap cells of cress after treatment with cytochalasin B. Support for the membrane flow concept. Exp Cell Res 1981; 135:229-36. [PMID: 7286078 DOI: 10.1016/0014-4827(81)90315-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
12
|
Schneider EM, Sievers A. Concanavalin A binds to the endoplasmic reticulum and the starch grain surface of root statocytes. PLANTA 1981; 152:177-180. [PMID: 24302412 DOI: 10.1007/bf00385141] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/1980] [Accepted: 11/28/1980] [Indexed: 06/02/2023]
Abstract
Using Concanavalin A (Con A) labeled with fluorescein isothiocyanate, we studied the intracellular localization of receptor molecules in the calyptra of 24-h dark-grown cress roots. Fixation in glutaraldehyde gave positive binding of the distal complex of the endoplasmic reticulum and the nucelus in the statocytes. In contrast, fixation in formaldehyde did not preserve the membrane-associated receptors, but revealed Con A affinity of the starch grain surface within the amyloplasts. Treatment of glutaraldehydefixed sections with non-ionic detergents led to partial solubilization of membrane components: the starch grain surface turned positive, though the positive binding of Con A to the endoplasmic reticulum and the nucleus remained unaffected. We therefore conclude that the Con A receptor in the membrane is a glycoprotein tightly inserted in other components of the compartment.
Collapse
Affiliation(s)
- E M Schneider
- Botanisches Institut, Universität Bonn, Venusbergweg 22, D-5300, Bonn, Federal Republic of Germany
| | | |
Collapse
|