Question

A component of xylem is

• A. Sieve tube
• B. Medullary rays
• C. Sclereid
• D. Tracheid

Answer 1

The correct option is D Tracheid

A mature sieve tube is composed of vertical cells, placed one above other with perforated sieve plates at their end walls to serve as the main conducting element of phloem.

Vascular rays (medullary rays) are derived from horizontally organized ray initials and serve in radial-transport of water and nutrients, storage and secondary metabolites secreted,; they are produced above each primary xylem.

Sclereids are broad and harder (due to the presence of higher amount of lignin) primary tissues and are grouped according to their various shapes. They are mostly present in cortex and pith of gymnosperms.

Tracheid is the fundamental single elongated dead cell of xylem. Tracheids show unequal cell wall thickening making the walls thick at some places and thin at others. They have a narrow cavity and pitted end walls.

So, the correct answer is option D.