Question

Choose the elements in Column I with their corresponding features in Column II:

$\begin{array}{cccc}& \text{Column I}& & \text{Column II}\\ \text{A}& \text{Sieve tubes}& \text{I}& \text{Absent in monocots mostly}\\ \text{B}& \text{Companion cells}& \text{II}& \text{Sclerenchymatous cells}\\ \text{C}& \text{Phloem parenchyma}& \text{III}& \text{Nucleus controlling sieve tubes}\\ \text{D}& \text{Bast fibres}& \text{IV}& \text{Conducting element}\end{array}$

• A. A-I, B-II, C-III, D-IV
• B. A-I, B-II, C-IV, D-III
• C. A-III, B-IV, C-II, D-I
• D. A-IV, B-III, C-I, D-II

Answer 1

The correct option is D A-IV, B-III, C-I, D-II

Sieve tubes are the main conducting element of phloem. They are long, tube-like structures that are arranged longitudinally. Their end walls are perforated. At maturity, they lack nucleus and are associated with companion cells. They have peripheral cytoplasm and large vacuoles. The functions of sieve tubes are controlled by the nucleus of the companion cells.

Companion cells are specialized parenchymatous cells and they are non-conducting cells. Its nucleus controls the activity of the sieve tube element as mature sieve tube elements lack nucleus.

Phloem parenchyma are elongated, tapering cylindrical cells. They have dense cytoplasm and nucleus. They are absent in most monocots. They store food, resins, latex and mucilage.

Phloem fibres are formed of sclerenchymatous cells and are found in secondary phloem. They provide mechanical support to the sieve elements.