What is the Difference Between Protostele and Plectostele

The main difference between protostele and plectostele is that protostele contains a core of xylem surrounded by a region of phloem. But, plectostele contains plate-like regions of xylem surrounded by the phloem. Furthermore, the three types of protostele include the haplostele, actinostele, and plectostele. Thus, plectostele is a type of protostele. 

Protostele and plectostele are two types of arrangements of steles or the vascular tissue which occur in the earliest vascular plants. Generally, both of them contain a cylindrical strand of vascular tissue in which the xylem is surrounded by the phloem. Also, around the vascular tissue, these stems contain an endodermis. 

Key Areas Covered 

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

Key Terms 

Lower Plants, Phloem, Plectostele, Protostele, Stele, Xylem

What is Protostele 

Protostele is a type of arrangement of the stele, occurring in early vascular plants. Usually, the main characteristic of it is the presence of a solid, cylindrical strand of xylem, surrounded by a ring of phloem. In addition to that, there is an endodermis, which surrounds the phloem. Here, the endodermis is responsible for regulating the flow of water in and out of the vascular tissue. Besides, the stele or the vascular tissue replaces the central pith this arrangement. For example, the types of lower plants with protostele include some seed plants, pteridophytes, and lycopods.

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 a cylindrical ring of phloem surrounds it. Also, the xylem in this arrangement shows the centrarch development in which the protoxylem in the center is covered by the metaxylem in a cylindrical manner. Typically, haplostele occurs in some ferns and the root of some seed plants. In contrast, in the actinostele, the vascular core is either lobed or fluted. Apart from that, the primary xylem development is exarch here; this type of stele arrangement occurs in club moss. Also, the exarch is the maturation of the metaxylem from the periphery towards the center.  

What is Plectostele 

Plectostele is a type of protostele, mainly occurring in some of the modern clubmosses. Here, the xylem occurs as plates in the transverse section. Also, although these plates occur in a discrete pattern, they interconnect in the longitudinal section. Apart from that, each plate is the phloem surrounds the xylem plants, forming a core. Usually, plectostele is an advanced type of actinostele. 

Similarities Between Protostele and Plectostele  

• Generally, protostele and plectostele are two types of arrangements of vascular tissue in the stems of the earliest vascular plants.  
• Also, these arrangements of vascular tissue contain xylem in the core surrounded by the phloem, forming a cylindrical core of vascular tissue.  
• However,  these arrangements are responsible for conducting water and sugar throughout the plant accordingly. 

Difference Between Protostele and Plectostele 

Definition 

Protostele refers to a simple, primitive arrangement of conducting tissues in the stems and roots of certain lower plants, consisting of a solid cylinder of xylem surrounded by a layer of phloem. On the other hand, plectostele refers to a form of protostele in which the xylem elements are arranged in usually parallel plates. 

Correspondence 

The three types of protostele include the haplostele, actinostele, and plectostele. Thus, plectostele is a type of protostele. 

Arrangement of Vascular Tissue 

Protostele contains a core of xylem surrounded by a region of phloem while plectostele contains plate-like regions of xylem surrounded by the phloem. 

Occurrence 

Protostele occurs in some seed plants, pteridophytes, and lycopods while plectostele occurs in lycopodiales, which includes all of the core clubmosses. 

Conclusion 

In brief, protostele is a type of stele mainly occurring in pteridophytes. In which, the xylem occurs in a core while the phloem surrounds it. Also, the three types of protostele are haplostele, actinostele, and plectostele. Meanwhile, plectostele is the type of protostele with an arrangement of plate-like xylem in the core surrounded by a region of phloem. Significantly, it occurs in clubmoss. Therefore, the main difference between protostele and plectostele is the type of xylem arrangement and occurrence. 

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