Question

Xylem is exarch in
(a) Leaf
(b) Petiole
(c) Stem
(d) Root

Answer 1

 
Hint: Complex tissues are made up of more than one type of cell. Exarch xylem is found in the parts of the plant which help in the absorption of nutrients from the soil as well as act as an anchorage.

Complete Step by Step Answer: Xylem is the chief water- conducting tissue of the plants. The Exarch condition of xylem is present in which the metaxylem lies towards the centre and the protoxylem towards the periphery. This condition is found in the roots of the plants. The xylem which arises early, i.e., during the primary growth of the plant body is called the primary xylem. It is further of two types based on their origin, Protoxylem and Metaxylem. - The first formed xylem is known as protoxylem and the later formed is known as metaxylem. - The arrangement of primary xylem occurs in two ways, Exarch and Endarch. - In the endarch condition, the protoxylem (the first- formed xylem) lies towards the centre (pith) and the metaxylem (the later- formed xylem) lies towards the periphery. Hence, the youngest lies closest to the periphery in this type of arrangement. - In exact condition, the protoxylem (the first- formed xylem) lies towards the periphery and the metaxylem (the later- formed xylem) lies towards the centre (pith) . Hence, the youngest lies closest to the centre in this type of arrangement.

So, the correct answer is, ‘(d)Root’

Note:  - The metaxylem is more mature than protoxylem. - Protoxylem has vessels with a narrow lumen and the metaxylem has vessels with broad diameter. - Endarch type of arrangement occurs in stems whereas the exarch condition occurs in the roots.