Question

A stele consisting of numerous closed vascular bundles is called as
A. Eustele
B. Dictyostele
C. Atactostele
D. Solenostele

Answer 1

Hint: It is a variation of the eustele, being more complex. It contains numerous vascular bundles which are scattered throughout the stem. Also, it does not contain a central pith. It occurs in the stem of monocots. It does not contain pith.

Complete answer:
In a vascular plant, the stele is the central part of the root or stem which contain the tissues that are derived from the procambium. These include vascular tissue, in some cases pith and a pericycle.

Eustele – In this type of arrangement, the primary vascular tissue consists of vascular bundles, generally in one or two rings around the pith. The eustele also appears in the roots of monocot flowering plants.

Dictyostele – In this type of arrangement, multiple gaps in the vascular cylinder exist in any one transverse section. The various leaf gaps give a dictyostele the appearance of many isolated islands of xylem surrounded by phloem.

Atactostele - This is a variation of the eustele which is more complex. It means that it contains numerous vascular bundles, scattering throughout the stem and it does not contain a central pith.
Solenostele- In this type of arrangement, the cylinder of vascular tissue contains no more than one leaf gap in any transverse section i.e. has non-overlapping leaf gaps.

Hence, the correct answer is option (C)

Note: The main difference between eustele and atactostele is that eustele contains vascular bundles in one or two rings. But, the atactostele contains numerous vascular bundles, scattered throughout the stem.