Stelar System in Pteridophytes II Types of Stele in Plants II Stelar Evolution in plants II Protostele, Siphonostele, Selenostele, Eustele, Atactostele I Free Notes I LetsBloomStudyMaterial I Plant Anatomy #biology #pgtbiology #kvs #nvs #emrs

What is Stele? 

Stele is the central vascular cylinder in plant parts like root, stem and leaves.

Vascular Cylinder represents the permanent tissues xylem and phloem arranged in a peculiar way.

Stele is the location of xylem and phloem.

TYPES OF STELES IN PLANTS

1) Protostele/ Haplostele:

In this the central core of xylem is surrounded by Phloem.

Pith is absent.

In protostele xylem break into different forms on basis of that it is following types:

TYPES:

a) Haplostele – A simple cylindrical core of xylem surrounded by phloem.

• Example: Selaginella (some species)

b) Actinostele – The xylem core has radiating arms, giving it a star-like appearance.

• Example: Psilotum (whisk ferns)

c) Plectostele – Xylem is broken into separate plates, appearing scattered.

• Example: Lycopodium clavatum(club moss)

d) Mixed Protostele: In this xylem scattered in phloem. 

• Example: Lycopodium cernum

2) Eustele:

The vascular tissues are arranged in discrete, separate bundles around a central pith.

The stele split into distinct collateral vascular bundles.

The splitting takes place due to overlapping leaf base.

Found in gymnosperms and dicot angiosperms.

3) Atactostele: 

• In this condition the vascular bundles are scattered.
• Seen Monocot stem of Angiosperms.

4) Siphonostele:

In this type the protostele is having pith/medulla in center. 

It is of two kinds:

a) Ectophloic: In this type, Xylem is surrounded by Phloem on Outer side only, Pith is present in center.

b) Amphiphloic: In this type, Xylem is surrounded by Phloem on Outer side as well as on inner side, Pith is present in center.

5) Solenostele:

In this type there is a central vascular ring which may or may not be disrupted by leaf gaps in some plants.

Perforations are there in places.

In Marsilea there is no overlapping leaf gap.

TYPES:

a) Ectophloic: In this type, Xylem is surrounded by Phloem on Outer side only, Pith is present in center.

b) Amphiphloic: In this type, Xylem is surrounded by Phloem on Outer side as well as on inner side, Pith is present in center.

Example: Adiantum pedatum

c) Dictyostele:

In this type of stele, whole stele of vascular cylinder is disrupted or dissected by leaf gaps.

Separate vascular strands were seen in dictyostele, they are called as Meristele, just like protostele it has central xylem surrounded by phloem.

Example: Ophioglossum lusitanicum, Pteris, Adiantum capillaris and Dryopteris 

This is seen in fern rhizome and in some gymnosperms.

QUESTION PRACTICE:

Select the correct pair - (RPSC)

(1) Plectostele   Lycopodium serratum

(2) Actinostele Lycopodium clavatum

3) Mixed Protostele - Lycopodium cernuum

(4) Amphiphloic siphonstele -Selaginella

Match List I (Types of Stele) and List II (Names of Genera) and find the correct answer with the help of codes given below:  College lecturer Exam)

A-ii B iii C-iv D-i

A-iii B ii C-iv D-i

A-iv B iii C-ii D-i

A-i B ii C-iii D-iv

A Stele without pith is called as: (KVS)

• Meristele

• Protostele

• Eustele

• Dictyostele