The effect of suberin lamellae on the vitality and symplasmic permeability of the onion root exodermis

1996 ◽  
Vol 74 (8) ◽  
pp. 1220-1226 ◽  
Author(s):  
Carol A. Peterson ◽  
Janet L. Waite
Keyword(s):  
Cell Types ◽  
Ion Transfer ◽  
Onion Root ◽  
Cell Vitality ◽  
Casparian Bands ◽  
Allium Cepa L ◽  
Suberin Lamellae ◽  
Form Part ◽  
Wall Permeability ◽  
Suberin Lamella

The onion exodermis is made up of two cell types, i.e., long and short cells. Both form Casparian bands, but suberin lamella development is absent or delayed in the short cells. Long cells did not accumulate fluorescein, a common test for cell vitality, because of reduced wall permeability due to suberin lamella development. Immature, long cells without lamellae stained in 15 min, whereas mature cells with lamellae required a 3.5- to 4-h treatment before staining was visible. Long exposure to fluorescein was needed to show that mature long cells were alive. Their vitality appeared to decline slowly with age but was not affected by drought stress. Fluorescein staining was apparent in the long cells only after treatment of paradermal sections; when dye was applied only externally to root segments, it did not enter the long cells from the epidermis or from the neighbouring short cells. This result indicates that the long cells were connected symplasmically to the cells of the cortex but were either unconnected, or connected by plasmodesmata of small functional diameter, to the epidermal and short cells. If they were unconnected, they would not form part of the symplasmic path of ion transfer into the root. Keywords: Allium cepa L., drought, exodermis, suberin lamella, vitality.

Development of cell wall modifications in the endodermis and exodermis of Allium cepa roots

2001 ◽  
Vol 79 (5) ◽  
pp. 621-634 ◽  
Author(s):  
Fengshan Ma ◽  
Carol A Peterson
Keyword(s):  
Electron Microscopy ◽  
Allium Cepa ◽  
Plasma Membranes ◽  
Casparian Bands ◽  
Transmission Electron ◽  
Allium Cepa L ◽  
Suberin Lamellae ◽  
Pit Field ◽  
Casparian Band ◽  
Suberin Lamella

The cytological events of wall modification in the endodermis and exodermis of Allium cepa L. roots were examined with fluorescence and transmission electron microscopy. In the endodermis, Casparian bands, suberin lamellae, and tertiary walls developed in succession. At the site of the future Casparian band, the plasma membrane was bound to the wall before deposition of detectable hydrophobic components in the radial wall. Suberin lamellae were deposited on the inner faces of the primary walls, first along the outer tangential walls and then the inner tangential walls. On both walls, segments of the lamellae were formed earlier in primary pit fields than at nonprimary pit field regions. Suberin lamellae then extended to the radial walls. When they reached the Casparian bands, the lamellae intruded between the bound plasma membranes and the walls, so that the cells' plasma membranes remained intact. In this way, suberin lamellae that were continuous around the cells were laid down. Later, tertiary walls were deposited internal to the suberin lamellae. None of the wall modifications interrupted the symplastic connections of the endodermis. During suberin lamella and tertiary wall formation, more dictyosomes and ER profiles appeared than during Casparian band development. In the exodermis, although Casparian bands were readily detected with fluorescence microscopy, they were rarely detected with electron microscopy. Suberin lamellae were formed in long cells severing their plasmodesmata. As in the endodermis, dictyosomes and ER were prominent during suberin lamella formation. Tertiary walls were not formed in the exodermis.Key words: Allium cepa, Casparian band, endodermis, exodermis, suberin lamella, ultrastructure.

Suberin deposition and band plasmolysis in the corn (Zea mays L.) root exodermis

1997 ◽  
Vol 75 (7) ◽  
pp. 1188-1199 ◽  
Author(s):  
Daryl E. Enstone ◽  
Carol A. Peterson
Keyword(s):  
Zea Mays ◽  
Zea Mays L ◽  
Lateral Roots ◽  
Root Surface ◽  
Casparian Bands ◽  
Suberin Lamellae ◽  
Tight Connection ◽  
Casparian Band ◽  
Apoplastic Barrier ◽  
Suberin Lamella

The exodermal Casparian band in corn (Zea mays L.) was first seen 10 mm distal to the kernel 4 days after planting. From its inception, the band usually occupied most of the radial wall (as seen in a cross section of the root). Subsequent maturation of the band around the root was asynchronous into the region of emerging lateral roots. Thus, a continuous apoplastic barrier would have been absent over much of the young root surface. Suberin lamellae development was also asynchronous, as these structures formed in those cells which had Casparian bands. Frequently, a lamella was initially deposited in patches, progressing centripetally until a continuous lipid layer was formed around the cell protoplast. Many instances of band plasmolysis (typical of the endodermis) were observed in the developing uniform exodermis. It could occur in cells with no detectable Casparian bands, suggesting that the tight connection between the plasmalemma and the wall that causes this phenomenon is not due to hydrophobic attractions. The results are consistent with the idea that there are strong attractions between proteins of the membrane and wall in the region of the Casparian band. The tight connection between the plasmalemma and the wall was broken during the later stages of suberin lamella development. Key words: Zea mays L., Poaceae, band plasmolysis, exodermis, Casparian band, suberin lamella.

Development of Casparian bands and suberin lamellae in the endodermis of onion roots

1992 ◽  
Vol 70 (11) ◽  
pp. 2233-2237 ◽  
Author(s):  
Alban D. Barnabas ◽  
Carol A. Peterson
Keyword(s):  
Allium Cepa ◽  
Small Region ◽  
Root Tip ◽  
Radial Wall ◽  
Casparian Bands ◽  
Suberin Lamellae ◽  
Casparian Band ◽  
Apoplastic Barrier ◽  
Endodermal Cells ◽  
Suberin Lamella

The endodermal Casparian band in onion (Allium cepa L.) roots is first evident 10 mm from the apex. It occupies a small region (20–30%) in the middle of the radial wall for a distance of 70 mm from the apex. However, with the development of suberin lamellae in most cells at greater distances from the root tip, the band expands symmetrically through the wall until, at 80 mm from the root tip, it fills the entire radial wall. Passage cells overlying some xylem poles have a delayed development of suberin lamellae, and in these cells the Casparian bands remain narrow. The sensitive stain, Fluorol yellow 088, detects precursors of the suberin lamellae in the outer tangential walls of the endodermal cells. The presence of complete lamellae is indicated by Sudan red 7B staining and resistance to acid digestion. Growth of the Casparian band during suberin lamella development may play a role in maintaining the apoplastic barrier in this layer by enlarging the contact area between the band and the lamellae. Key words: Casparian band, endodermis, suberin lamella, Allium cepa.

Deposition of Casparian bands and suberin lamellae in the exodermis and endodermis of young corn and onion roots

1986 ◽  
Vol 64 (9) ◽  
pp. 1873-1878 ◽  
Author(s):  
C. J. Perumalla ◽  
Carol A. Peterson
Keyword(s):  
Growth Rate ◽  
Age And Growth ◽  
Root Tip ◽  
Casparian Bands ◽  
Corn Roots ◽  
Suberin Lamellae ◽  
Casparian Band ◽  
The Individual ◽  
Suberin Lamella ◽  
Individual Root

The Casparian band of the exodermis of corn and onion roots matures further from the root tip than its counterpart in the endodermis. A complete suberin lamella in the exodermal cells usually develops about 10 mm proximal to the exodermal Casparian band. The distance between the exodermal Casparian band and suberin lamella in the endodermis was usually much greater than in the exodermis. Both the exodermal Casparian band and suberin lamella matured closer to the tip in onion than in corn roots. The distance from the root tip at which the exodermal Casparian band matured increased with root age during the 5-day period studied in corn grown in hydroponics and vermiculite, and onion grown in hydroponics. This difference was most pronounced in corn, in which the Casparian band matured 20 mm from the root tip when the root was 20 mm long but matured 120 mm from the tip 4 days later when the root was 170 mm long. When the growth rate of corn roots was drastically inhibited by adding polyethylene glycol to the hydroponic medium, the exodermal Casparian band and suberin lamellae were present within 10 mm of the root tip. The position in the root at which the exodermis matures is thus highly variable and can depend on the plant species, and the age and growth rate of the individual root.

Spatial and temporal deposition of suberin during maturation of the onion root exodermis

Botany ◽  
2011 ◽  
Vol 89 (2) ◽  
pp. 119-131 ◽  
Author(s):  
Chris J. Meyer ◽  
Carol A. Peterson ◽  
Mark A. Bernards
Keyword(s):  
Soluble Fraction ◽  
Cell Types ◽  
Gas Chromatography Mass Spectrometry ◽  
Enzymatic Characterization ◽  
Dioic Acid ◽  
Onion Root ◽  
Suberin Lamellae ◽  
Metabolite Profiles ◽  
Cell Layers

Suberin is a complex biopolymer composed of a poly(aliphatic) domain (SPAD) and a poly(phenolic) domain (SPPD). Suberin is typically confined to specialized cell types including root exodermal cells, but its synthesis in a maturing exodermis is still not well understood. For the current work, Allium cepa roots were used as a model to analyze SPAD and SPPD synthesis in a maturing uniseriate exodermis. Roots were divided into four maturation zones based on their growth rate and the deposition of suberin lamellae in maturing exodermal cells. Exodermal and epidermal cell layers were separated from the underlying layers in each maturation zone, then soluble and insoluble suberin monomers were extracted chemically, and quantified and identified by gas chromatography – mass spectrometry. Temporal patterns for the synthesis of the SPAD, but not for the SPPD, were revealed upon resolution of the metabolite profiles. The composition of the soluble fraction was essentially unchanged as the exodermis matured. In contrast, the SPAD composition differed during maturation, mainly owing to significant increases in the deposition of C18:1 α,ω-dioic acid and ω-OH fatty acids. It is proposed that the exodermal maturation zones with their corresponding metabolite profiles be used as targets for the functional enzymatic characterization of suberin biosynthetic pathways.

Growth kinetics in the pericycle cell types along the apical meristem of the onion root

1990 ◽  
Vol 14 ◽  
pp. 101
Author(s):  
P CASERO ◽  
C GARCIASANCHEZ ◽  
P LLORET ◽  
J NAVASCUES
Keyword(s):  
Growth Kinetics ◽  
Apical Meristem ◽  
Cell Types ◽  
Onion Root ◽  
Pericycle Cell

scholarly journals Super-human cell death detection with biomarker-optimized neural networks

2020 ◽  
Author(s):  
Jeremy W. Linsley ◽  
Drew A. Linsley ◽  
Josh Lamstein ◽  
Gennadi Ryan ◽  
Kevan Shah ◽  
...  
Keyword(s):  
Neural Networks ◽  
Cell Death ◽  
High Throughput ◽  
High Throughput Screening ◽  
Morphological Characteristics ◽  
Ground Truth ◽  
Cell Types ◽  
Live Cells ◽  
New Paradigm ◽  
Cell Vitality

AbstractCell death is an essential process in biology that must be accounted for in live microscopy experiments. Nevertheless, cell death is difficult to detect without perturbing experiments with stains, dyes or biosensors that can bias experimental outcomes, lead to inconsistent results, and reduce the number of processes that can be simultaneously labelled. These additional steps also make live microscopy difficult to scale for high-throughput screening because of the cost, labor, and analysis they entail. We address this fundamental limitation of live microscopy with biomarker-optimized convolutional neural networks (BO-CNN): computer vision models trained with a ground truth biosensor that detect live cells with superhuman, 96% accuracy more than 100 times faster than previous methods. Our models learn to identify important morphological characteristics associated with cell vitality without human input or additional perturbations, and to generalize to other imaging modalities and cell types for which they have no specialized training. We demonstrate that we can interpret decisions from BO-CNN models to gain biological insight into the patterns they use to achieve superhuman accuracy. The BO-CNN approach is broadly useful for live microscopy, and affords a powerful new paradigm for advancing the state of high-throughput imaging in a variety of contexts.

scholarly journals Binding of 1-nitro-9- (3-dimethylaminopropylamino)-acridine to the DNA of the apical meristem cells of adventitious onion (Allium cepa L.) roots

2014 ◽  
Vol 53 (2) ◽  
pp. 217-222
Author(s):  
Danuta Antosiewicz
Keyword(s):  
Allium Cepa ◽  
Apical Meristem ◽  
Root Tips ◽  
Onion Root ◽  
Allium Cepa L ◽  
Covalently Bound

It was established that one half of the ledakrin (I-nitro-9-(3-dimethylaminopropylamino)-acridine) bound to the DNA in the cells of the studied onion root tips (<em>Allium cepa</em> L.), forms labile complexes with it, the remaining half is covalently attached to only one strand of the DNA. One molecule of covalently bound ledakrin falls on average to 10<sup>4</sup>-2X10<sup>4</sup> pairs of bases.

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