Question

In sieve elements, the pores in the sieve plate are blocked by a substance called

• A. Cutin
• B. Callose
• C. Suberin
• D. Lignin

Answer 1

The correct option is B Callose

Sieve-tube members are tubular in structure. These are continuously placed and have specialised sieve areas called as sieve plates which occur at the end. Sieve areas have several perforations through which the adjacent sieve cells are interconnected by protoplasmic strands. They are blocked by callose at maturity. Accumulation of callose occurs in an old, non-functional sieve elements and seals the old elements closed to keep the phloem translocation stream active.

So, the correct answer is option B.