IGCSE Biology Paper-1: Specimen Questions with Answers 110 - 110 of 208

Question 110

Question

MCQ▾

Given diagram is showing internal structure of Phloem.

Which of the following option is Incorrect?

Structure of Phloem

Choices

Choice (4)

a.

A-Sieve plate, B-Sieve pore, C-Cytoplasm

b.

A-Cytoplasm, B-Sieve pore, C-Sieve plate

c.

A-Cytoplasm, B-Sieve plate, C-Sieve pore

d.

A-Sieve pore, B-Cytoplasm, C-Sieve plate

Answer

c.

Explanation

Phloem (Bast) : Term “Phloem” was given by Nageli. Its main function is the transport of organic food materials from leaves to stem and roots.

It consists of the following elements:

Sieve Tubes

  • They are long tube-like cells placed end to end, forming a continuous channel.
  • Their cell wall is made up of cellulose.
  • Their transverse wall is perforated like a normal sieve and hence they are called as sieve tubes.
  • They are anucleate living cells.
  • Callose pad may be visible in the winter season. P-proteins are also found.

Companion Cells

  • They are thin-walled cells which are associated with sieve tubes by plasmodesmata.
  • They contain nucleus and are therefore living in nature.
  • They are not found in Pteridophytes and Gymnosperms but are always present in angiosperms.

Phloem Fiber

Their main function is mechanical support.

Phloem Parenchyma

Their function is storage of food material. They are absent in monocots.

Storage of Food Material