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Difference between Eustele and Atactostele: A Detailed Summary

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Eustele and Atactostele: An Introduction

In a vascular plant, the stele is the important part of the root or stem containing the tissues derived from the procambium. Closed type of vascular bundle lacks in cambium. The plant stele includes the primary vascular system of the plant axis, the stem and its related ground tissues for example pith. These consist of vascular tissue, in a few instances ground tissue (pith) and a pericycle, which, if present, defines the outermost boundary of the stele. Outside the stele lies the endodermis, that's the innermost cellular layer of the cortex. The method of the stele was developed within the late nineteenth century through French botanists P. E. L. van Tieghem and H. Doulton as a version to get knowledge of the relationship among the shoot and root, and for discussing the evolution of vascular plant morphology. Now, at the beginning of the twenty-first century, plant molecular biologists are coming to recognize the genetics and developmental pathways that govern tissue patterns within the stele.

What is Eustele?

The vascular tissue in a dicot stem includes many vascular bundles which are part of the plant transport device. They transport food, vitamins and water up and down the stem. In the past nineteenth century, the stele was found by P.E.L Van Tieghem and H. Doulton for higher information on the evolution of the vascular device in plant life. In a vascular plant, it was determined that the stele became the important part of the stem and root which consisted of vascular tissue. The xylem became liable for transporting and storing water and water-soluble nutrients in plant life and comprised tracheids, vessels, and wood parenchyma. The phloem becomes liable for transporting protein, sugars and different molecules in plant life and comprises sieve elements, companion cells, phloem parenchyma, and phloem fibres. A supporting tissue like a pericycle becomes a plant tissue and present among the endodermis and the phloem and is liable for root initiation and preservation of meristematic activity. It shapes the outer boundary of the stele. An example is sunflowers.

There are unique kinds of steles found in a vascular plant, one is eustele. Brebner in 1902, found a derived model of siphonostele in seed plant stem and recounted it as eustele. In eustele, a tissue includes vascular bundles that surround the pith within the shape of 1 or rings. The vascular bundle within the eustele may be collateral, that is, the phloem is only present on one aspect of the xylem or bi-collateral, that is, the phloem is present on each aspect of the xylem. In eustele, the internal fascicular region and the leaf space aren't separated clearly.For example, conifers (gymnosperm), roots of monocot and dicot stem are common examples of eustele. Eustele is a derived shape of siphonostele and is now no longer an immediate category of stele. There are kinds of eustele:

  • Protostele – In this phloem surrounds the xylem.

  • Siphonostele – In this xylem is surrounded through the phloem and pith is present within the centre.


Atactostele is a kind of eustele, being greater complex. Atactostele is located in monocots, wherein the vascular tissue within the stem exists as scattered bundles; also it does not include a central pith. Most seed plant stems have a vascular arrangement, which has been interpreted as a derived siphonostele and is known as eustele. An example is corn.

Difference between Eustele and Atactostele



It is a type of siphonostele in which vascular tissue in the stem forms a central ring of bundles around the pith.

It is a type of eustele which is found in monocots in which vascular tissue in the stem exists as scattered bundles.

This type of stele is seen in dicot stem and the root of monocots.

Occurs in the stem of monocots.

There are vascular bundles arranged in the form of rings.

In atactostele, vascular bundles are scattered.

4 to 8 vascular bundles are there.

Numerous vascular bundles are there.

Vascular bundles are equal in size.

Here outer vascular bundles are smaller than the inner vascular bundles.

It does not contain a sclerenchymatous bundle cap.

It contains a sclerenchymatous bundle cap.

Vascular bundles are not surrounded by a bundle sheath.

Vascular bundles are surrounded by a sclerenchymatous bundle sheath.

There are many metaxylem elements present.

There are only 2 metaxylem elements present.

Protoxylem lacuna is absent in eustele.

Protoxylem lacuna is present in eustele.

Interesting Facts

  • Stele was rediscovered in 1901.

  • Stele is the upright core of a vascular plant which supports plants.

  • The most primitive type of stele is prostele.

  • Atactostele is found in monocots.

  • Eustele is the type of stele in dicot stem,roots of monocots, some conifers.

Important Questions

1. Define Amphivasal vascular bundle?

Ans: Amphivasal vascular bundle is a type of concentric vascular bundle which has xylem surrounding the phloem.

2. What is Atactostele?

Ans: Atactostele is a type of eustele which is found in monocots in which vascular tissue in the stem exists as scattered bundles.

3. Give an example of a stem having Atactostele?

Ans: Monocot stems have an atactostele.

Key Features of Eustele and Atactostele

  • Eustele is a form of siphonostele, containing vascular bundles organised in a single ring. This is common type of stele in dicot stem.

  • Generally, four to eight of such vascular bundles arise within the stem of dicots. Also, the central pith takes place internally to the xylem. Additionally, eustele additionally takes place within the root of the monocots.

  • Atactostele is a variation of eustele, containing several vascular bundles, which occur scattered during the stem.

  • Usually, atactostele takes place within the monocot stem.

  • In conclusion, the primary distinction between eustele and atactostele is the arrangement of vascular bundles and occurrence.

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FAQs on Difference between Eustele and Atactostele: A Detailed Summary

1. Write the similarities of eustele and atactostele.

  • Eustele and atactostele are forms of vascular tissue arrangements. 

  • Generally, each is a form of siphonostele wherein a ground tissue known as the pith inner to the xylem. 

  • Also, they arise in seed plants. 

  • They include each protoxylem and metaxylem.  

  • Their characteristic is to conduct water and sugar consequently thru the stem.

2. What is a stele made up of?

The stele includes vascular tissue, ground tissue or pith, and a pericycle. The pericycle especially forms the outermost boundary of the stele. Therefore, the stele may be defined as the vascular bundle. The stele consists of 3 tissues which can be the pericycle, the xylem, and the phloem.

3. What is the colour of the pith?

When new pith increase is generally white or pale in colour, due to the tissue ages it usually darkens to a deeper brown colour.