Question

Atactostele consists of vascular bundles
a. Arranged in a ring
b. Three in number
c. Scattered in ground tissue
d. Broken vascular bundles

Answer 1

Hint: Atactostele is a type of eustele which is found in monocots. Most of the seed plant stem contains vascular bundles, which are interpreted as siphonostele and are called eustele. There are various variants of eustele which are found in monocots, like rye and maize.

Complete answer:
Atactostele is a type of eustele which has vascular tissues in the stem that exist as scattered bundles. Eustele consist of vascular bundles in the form of one or two rings whereas an actostele contains numerous vascular bundles which are scattered in ground tissue throughout the stem. Atactostele occurs in the stem of monocots whereas eustele occurs in the stem of dicots. Eustele contains 4 to 8 vascular bundles but an actostele contains numerous vascular bundles arranged in scatter. Vascular bundles present in the eustele are of equal size whereas outer vascular bundles are smaller than inner vascular bundles in the atactostele.

Atactostele contains a sclerenchymatous bundle sheath and only two metaxylem elements are present per vascular bundle. Xylem elements are circular in shape and protoxylem lacuna is present. Atactostele do not have pith, pericycle and medullary rays in it. Ground tissue of an atactostele is not differentiated into stellar and extra-stellar tissue. In atactostele both phloem parenchyma and phloem fibres are absent.

Hence, the correct answer is option (C).

Note: Atactostele is a more complex variation of the eustele. As it contains numerous vascular bundles which are scattered throughout the stem as it does not contain a central pith. The main function of an atactostele is to conduct water and sugar throughout the stem of the plant.