Consider the following statements about 'Sieve Tubes' in Phloem: 1. They are thick-walled cells with no perforations. 2. They are living cells at maturity. 3. They are responsible for the transport of water. Which of the statements given above are correct?

The correct option is (b). Explanation Phloem is a complex permanent tissue in vascular plants responsible for the translocation of organic nutrients (food). The main conducting elements of phloem are the sieve tube elements, which function in association with companion cells. - Statement 1 is Incorrect. Sieve tube elements are long, tube-like structures arranged longitudinally. Their walls are generally thin and cellulosic, not thick. Crucially, their end walls are perforated in a sieve-like manner to form sieve plates. These perforations allow for the flow of materials between cells. - Statement 2 is Correct. Sieve tube elements are living cells at maturity. Although a mature sieve element possesses a peripheral cytoplasm and a large vacuole, it lacks a nucleus. The metabolic functions of the sieve tube are maintained and controlled by the nucleus of the adjacent companion cell. - Statement 3 is Incorrect. Phloem is responsible for the transport of food materials (primarily sucrose) from leaves to other parts of the plant. The transport of water and minerals is the function of the Xylem tissue. Key Takeaway: Sieve tubes are living, enucleated cells found in phloem that possess perforated end walls (sieve plates) and are responsible for the translocation of food, not water.

Consider the following statements about 'Sieve… - NCERT Class 9 Science MCQ

NCERT Class 9 Science — Chapter 2: Tissues

mcqhard

Consider the following statements about 'Sieve Tubes' in Phloem:

They are thick-walled cells with no perforations.
They are living cells at maturity.
They are responsible for the transport of water.

Which of the statements given above are correct?

NCERT textbook question

From NCERT Science - class 9 · Page 64

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (b).

Explanation

Phloem is a complex permanent tissue in vascular plants responsible for the translocation of organic nutrients (food). The main conducting elements of phloem are the sieve tube elements, which function in association with companion cells.

Statement 1 is Incorrect. Sieve tube elements are long, tube-like structures arranged longitudinally. Their walls are generally thin and cellulosic, not thick. Crucially, their end walls are perforated in a sieve-like manner to form sieve plates. These perforations allow for the flow of materials between cells.
Statement 2 is Correct. Sieve tube elements are living cells at maturity. Although a mature sieve element possesses a peripheral cytoplasm and a large vacuole, it lacks a nucleus. The metabolic functions of the sieve tube are maintained and controlled by the nucleus of the adjacent companion cell.
Statement 3 is Incorrect. Phloem is responsible for the transport of food materials (primarily sucrose) from leaves to other parts of the plant. The transport of water and minerals is the function of the Xylem tissue.

Key Takeaway: Sieve tubes are living, enucleated cells found in phloem that possess perforated end walls (sieve plates) and are responsible for the translocation of food, not water.

Your note

More from Chapter 2: Tissues

Consider the following statements regarding 'Complex Permanent Tissues': 1. They are made of more than one type of cell. 2. Each cell in the tissue functions independently without coordination. 3. Xylem and Phloem are examples of complex tissues. Which of the statements given above is/are correct?

medium

Consider the following statements about epithelial tissue: 1. It forms a barrier to keep different body systems separate. 2. It is directly connected to the underlying tissue without any separating membrane. 3. It contains large intercellular spaces to facilitate the movement of materials. Which of the statements given above is/are correct?

medium

Consider the following statements about 'Smooth Muscles': 1. They are also known as striated muscles. 2. They control involuntary movements like the movement of food in the alimentary canal. 3. They are multinucleate. Which of the statements given above are correct?

medium

With reference to the fundamental differences between plants and animals, consider the following statements: 1. Plants have a large quantity of supportive tissue which generally consists of dead cells. 2. Growth in plants is uniform throughout the body, whereas in animals it is limited to specific regions. 3. Animals consume more energy compared to plants due to active locomotion. Which of the statements given above is/are correct?

medium

Which one of the following is the most appropriate reason for the skin being made of 'Stratified Squamous Epithelium'?

easy

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