What is the Difference Between Protostele and Siphonostele

The main difference between protostele and siphonostele is that the protostele consists of a solid core of vascular tissue without a central pith or leaf gaps, whereas the siphonostele consists of a cylindrical vascular tissue, surrounding the central pith and consisting of leaf gaps. 

Protostele and siphonostele are two types of arrangements of the stele, the central part of the stem and root. Protostele is the most primitive type of stele while siphonostele is a modification of the protostele.

Key Areas Covered

1. What is Protostele
     – Definition, Arrangements, Occurrence
2. What is Siphonostele
     – Definition, Arrangements, Occurrence
3. What are the Similarities Between Protostele and Siphonostele
     – Outline of Common Features
4. What is the Difference Between Protostele and Siphonostele
     – Comparison of Key Differences

Key Terms

Actinostele, Central Pith, Dictyostele, Eustele, Haplostele, Leaf Gaps, Plectostele, Protostele, Siphonostele, Solenostele, Stele Arrangement, Vascular Tissue

What is Protostele

Protostele is a type of arrangement of the stele in early vascular plants. It is characterized by the presence of a solid, cylindrical strand of xylem, surrounded by a ring of phloem. An endodermis surrounds the phloem, regulating the flow of water in and out of the vascular tissue. Therefore, the central pith is replaced by the vascular tissue in this arrangement.

Figure 1: Types of Protostele

Furthermore, the three types of protostele arrangements are haplostele, actinostele, and plectostele. In the haplostele, a cylindrical core of xylem is present and it is surrounded by a cylindrical ring of phloem. The xylem in this arrangement shows the centrarch development of the xylem in which the protoxylem in the center is covered by the metaxylem in a cylindrical manner. In the actinostele, the vascular core is either lobed or fluted. The primary xylem development is exarch here; this type of stele arrangement occurs in club moss. The exarch is the maturation of the metaxylem from the periphery towards the center. Finally, in the plectostele, the xylem occurs as plates in the transverse section are surrounded by the phloem.

What is Siphonostele

Siphonostele is a modification of protostele arrangement and it occurs in many ferns and some vascular plants. The main characteristic feature of the siphonostele is the presence of a central pith surrounded by the vascular tissue. Also, this type of arrangement has interruptions in the vascular strand where leaves originate. These interruptions are known as leaf gaps.

Figure 2: Types of Siphonostele

Moreover, the three types of siphonostele arrangements are solenostele, dictyostele, and eustele. Both solenostele and dictyostele arrangements are amphiphloic, which means their phloem surrounds the xylem in both external and internal sections. Solenostele arrangement occurs in ferns and it contains a single leaf gap. Dictyostele arrangement occurs only in ferns. It contains multiple leaf gaps. The third arrangement, eustele is ectophloic, which means that phloem occurs only in the external section of the xylem. In the ectophloic arrangement, the primary vascular tissue contains vascular bundles surrounding the central pith. And, this type of arrangements occurs in the root of the monocot flowering plants.

Similarities Between Protostele and Siphonostele

• Protostele and siphonostele are the two types of arrangements in the stele, the central part of the stem and root.
• French botanists P. E. L. van Tieghem and H. Doulton developed the concept of the stele in the late 19^th century. 
• Also, the stele contains the tissue that develops from the procambium.
• Besides, both types of arrangements are classified based on the development of the vascular tissue in the central part of the stem and root.

Difference Between Protostele and Siphonostele

Definition

Protostele refers to a type of stele in which the vascular tissue in the stem forms a solid core, with no central pith or leaf gaps while siphonostele refers to a type of stele in which the vascular tissue in the stem forms a cylinder surrounding a central pith and possessing leaf gaps. Thus, this is the main difference between protostele and siphonostele.

Occurrence

Moreover, another difference between protostele and siphonostele is the occurrence. The protostele occurs in primitive types of vascular plants while siphonostele occurs in some of the flowering plants and many ferns.

Central Pith

Also, the central pith is a major difference between protostele and siphonostele. Protostele lacks a central pith while siphonostele consists of a central pith.

The occurrence of the Vascular Tissue

Furthermore, the vascular tissue occurs in the center of the protostele while vascular tissue surrounds the central pith in siphonostele. Hence, this is also a difference between protostele and siphonostele.

Leaf Gaps

Besides, another difference between protostele and siphonostele is that protostele lacks leaf gaps while siphonostele contains leaf gaps.

Types

The three types of protostele arrangements are haplostele, actinostele, and plectostele while the three types of siphonostele arrangements are solenostele, dictyostele, and eustele.

Conclusion

Protostele is a type of arrangement of the stele where the vascular tissue forms a solid center in the stem and root. This means protostele does not contain a central pith. Also, it does not contain leaf gaps. Protostele occurs in primitive forms of vascular plants. In contrast, siphonostele is a modification of protostele, which occurs mainly in ferns. It consists of a central pith surrounded by a ring of vascular tissue. It also contains leaf gaps. Therefore, the main difference between protostele and siphonostele is the arrangement of the vascular tissue in the center of the stem and root.

References:

1. Gupta, Harika. “Stelar System of Plant: Definition and Types (With Diagrams).” Biology Discussion, 2 Feb. 2016, Available Here.

Image Courtesy:

1. “Protostele” By EncycloPetey at English Wikipedia – Transferred from en.wikipedia to Commons. (Public Domain) via Commons Wikimedia     
2. “Siphonostele” By EncycloPetey at English Wikipedia – Transferred from en.wikipedia to Commons. (Public Domain) via Commons Wikimedia