Xylem MCQ - Practice Questions with Answers

Complex Permanent Tissues - Xylem

• These are heterogeneous in nature, that is, they are composed of more than one type of cell.
• The vascular tissues - Xylem and Phloem are the complex permanent tissues.

XYLEM: 

• The term was given by Nageli in 1858. 
• Xylem is a vascular tissue that conducts water and minerals from roots to the aerial parts of the plants.
• The flow of water and minerals in the xylem is always unidirectional.
• On the basis of origin xylem can be of two types:

1. Primary xylem:  It originates from the procambium during the primary growth of the plant. The primary xylem which is formed early is called the protoxylem while the one formed later is called the metaxylem.
2. Secondary xylem: It originates from the vascular cambium during secondary growth of the plant. It constitutes the ‘wood’. 

Xylem consists of the following components:
 

TIP:

• In the stem, the protoxylem lies towards the centre and the metaxylem lies towards the periphery. This condition is called an endarch.
• In the root, the protoxylem lies towards the periphery and the protoxylem lies towards the centre. This condition is called an exarch.