Question

The stele in which xylem forms several plates is
A. Haplostele
B. Actinostele
C. Plectostele
D. Polycyclic

Answer 1

Hint: Xylem is a connective tissue that is composed of more than one type of cells and all these work together as a single unit. The functions of an xylem is conducting tissue for water and minerals from roots to the stem and leaves. It also helps in providing mechanical support to the plant parts.

Complete answer:
- Haplostele: It consists of a cylindrical core of xylem around which there is a ring of phloem. It is a smooth ore of xylem.
- Actinostele: It is a type of protostele in which the core of the xylem is lobed and fluted. It is a type of exarch and is found in many species of club moss etc. Exarch protostele is an important characteristic of the lycophyte lineage.
- Plectostele: It is a type of protostele in which there is a xylem region which is plate-like and it is found in the transverse section around which there is a phloem tissue around it. These plates are connected in a longitudinal section. These consist of the core of the xylem which is broken into the parallel plates.
- Polycyclic: It has a vascular bundle which is present in the form of two or more concentric cylinders. It is the most complex stele and its connection is in such a way that they are commonly found at nodes.
Hence, the correct answer is (C) Plectostele.

Note: Plectostele is a type of dictyostele and it has two types of vascular tissues. Plectostele can also be derived from the actiontele. It is commonly found in Lycopodium clavatum.