Stele - Description of Vascular Tissues which develop from Procambium Everyting inside the Endodermis |
| Protostele Proto means first. Protosteles are relatively simple, and have been observed in the oldest fossil plants. Consequently, they represent the first steles. The simplest protostele is the Haplostele. This consists of a solid core of xylem surrounded by a layer of Phloem. An Endodermis surrounds the stele. |
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| Psilotum Rhizome Cross-Section |
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The Stele occupies a central region in the Psilotum Rhizome. Xylem is found in the center of the Stele.This is an example of a Haplostele. The Xylem stains Red because its walls contain Lignin. Lignin makes the walls water-proof and it add strength to them. It is surrounded by Phloem which stains Blue. The Endodermis is hard to see in this photo. You need a Ph. D. to see it! |
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| The Endodermis is clearly visible in this Stele. Its cell walls have become heavily impregnated with Lignin and are relatively thick. Xylem occupies the center but the Phloem occupies indentations in the Xylem. This makes the Xylem resemble a Star. Consequently this is called an Actinostele. Actino menas Star. |
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| Plectostele The xylem appears to be dissected into plate-like sectors in a Plectostele. Phloem surrounds the xylem. An Endodermis surrounds the entire stele. |
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| Siphonostele A Siphonostele has a pith in the center. An Ectophloic Siphonostele has Phloem on its exterior circumference. An Amphiphloic Siphonostele has Phloem on both sides of the Xylem. An Endodermis is typically present. on both sides of the stele |
Amphiphloic Siphonostele |
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| Dictyostele A dictyostele is essentially a divided Amphiphloic Siphonostele. The Stele consists of Individual Bundles of Vascular Tissue.These contain a central strand of xylem surrounded by Phloem with an Endodermis surrounding the bundle. The bundles are arranged in one circle around the axis. |
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Eustele Eustele is similar to the dictyostele except that the bundles lack an endodermis and are collateral. Collateral Bundles have xylem on one side and phloem on the other, and the absence of an Endodermis. The bundles are arranged in one circle around the axis.A Eustele is characteristic for Dicot Stems. |
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| Atactostele An Atactostele consists of collateral bundles distributed in more that one ring within the Stem. This does not mean that the bundles are randomly arranged. A complex organizational pattern is present, but it is not obvious to a casual observer. A Pith is not present. There is no Endodermis. This stele is typical for Monocots like Sugarcane. |
 Asparagus Vascular Bundle |
| Name That Stele | |
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