Question

The stele present in Equisetum is
A. Haplostele
B. Actinostele
C. Plectostele
D. Siphonostele

Answer 1

Hint: Stele is present in the vascular plants. It is the central portion of the root or stem that contains cylinders of vascular tissues. These tissues are derived from procambium.

Complete answer:
• Equisetum is a plant genus in the family Equisetaceae. It is the only living genus in the family. The genus has 15 species which are pteridophytes that neither produce flowers nor seed. They reproduce by spores. Equisetum includes plants like ferns.
• Equisetum plants are commonly known as horsetails. The plants prefer wet environments and they are found over all continents except Australia and Antarctica. They are also not found in some south pacific islands like New-Zealand, Fiji etc.
• In ferns, the stele is made up of central pith and the cylinders of vascular tissues (xylem and phloem) surrounding the pith. Such a stele is called Siphonostele.
• Haplostele consists of a cylindrical xylem core surrounded by a phloem ring. It is found in genus Selaginella.
• Actinostele consists of alternating arrangements of xylem and phloem. It is found in some species of genus Lycopodium.
• Plectostele consist of parallel bands of xylem and phloem. It is found in some species of genus Lycopodium.

Hence, the correct answer is option (D).

Note: Siphonostele is a modification of protostele. In Siphonostele, the protostele is medullated. A protostele has a solid core of xylem which is surrounded by a phloem. If a protostele is modified in such a way that it is composed of a central parenchymatous region called pith surrounded by a tubular vascular region then it is called a siphonostele.