Root Directory
The organization of Monocot roots like Sugarcane is similar to that found in dicots like Ranunculus. However, tracheary elements may be absent from the center of the root. |
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 Epifluorescence Image of Smilax Root |
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Corn Root: Interface of the Stele & the Cortex-The cells with the largest Diameters are Vessel Members. Follow the Cortical Parenchyma from the top of the image to the first cells which have thick, red-stained walls. These are the Endodermis. |
The Endodermis usually develops exceedingly thick secondary walls at levels in the root which are no longer absorbing water. This obscures the Casparian Strips but makes the Endodermis more obvious.
There are usually more xylem arms in monocots.
The number of arms is indicated by the following terms.
| Two = Diarch |
| Three = Triarch |
| Four = Tetrarch |
| Five = Pentarch |
| Six = Hexarch |
| More than five = Polyarch |
Monocots are usually Polyarch.
Bundles of Phloem alternate with the Xylem arms. The xylem contains many lignified cells in older portions of the root. The phloem stands out because its cells have thin, unlignified cell walls.
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Cross-section of Clintonia (above) & Smilax (below) Roots. Count the number of xylem arms. Both are Monocots |
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Cross-section of Smilax Root. The tracheary elements of the Xylem are the cells with the largest diameters. Count the number of xylem arms. The Endodermis is the densely stained, lignified layer which surrounds the Stele.
The cell pattern is distorted by the extreme enlargement of the Vessel Members. |
Smilax root at higher magnification. Locate the Xylem and Phloem as well as the Endodermis, Cortex and Epidermis.
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 Inner Cortex and Stele of a Pineapple Root Stained with Toluidine Blue |
 Stele from Pineapple Root lightly Stained with Toluidine Blue |
| Locate the Endodermis and Xylem! | |
 Autofluorescence Image of an Orchid Aerial Root: Locate the Velamen and the Vascular Cylinder. |
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| The Velamen is an example of a Multiple Epidermis. This is the result of Periclinal divisions in the Protoderm which create Many Layers of Epidermis. The later differentiate to form the specialized Tissue called Velamen. | |
 Vanda Root Tip |
 Vanda Root Differentiation Zone |
 Vanda Root Tip |
 Vanda Root Tip |
 Vanda Root Tip showing the transition from a single layered Protoderm to a Multilayered Protoderm. This is due to Periclinal Divisions that create many layers from one layer. |
  Vanda Multiple Epidermis with & Without crossed Polarizers |
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| Vascular Tisues in the Root of Pili Grass Stained with Toluidine Blue (Left) & Phloroglucinol (Right). Note the high degree of Lignification. |
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