Select the living cells from the following using the codes given below :
(A) Chlorenchyma
(B) Collenchyma
(C) Bast
(D) Prosenchyma
(E) Sieve elements

Question

Select the living cells from the following using the codes given below : 
(A) Chlorenchyma 
(B) Collenchyma 
(C) Bast 
(D) Prosenchyma 
(E) Sieve elements

Accepted Answer

The correct option is 1: A, B and E

The question requires a clear understanding of the maturity and function of various plant tissue cells, specifically distinguishing between cells that retain a living protoplast and those that are mature and dead. The correct answer identifies Chlorenchyma (A), Collenchyma (B), and Sieve elements (E) as living cells. **Chlorenchyma (A)** is essentially a type of parenchyma tissue that contains chloroplasts, making it the primary site of photosynthesis. As parenchyma cells, they are thin-walled, actively metabolic, and definitively living at maturity. **Collenchyma (B)** tissue consists of living cells with irregularly thickened primary cell walls, usually found in the cortex of stems and petioles. Its main function is to provide flexible, non-lignified support to young, growing parts of the plant, and these cells retain a full, active protoplast. Lastly, **Sieve elements (E)** are the main conducting components of the phloem. Although they lack a nucleus, ribosomes, and a large central vacuole at maturity, their protoplast is still metabolically functional and is essential for translocation. Crucially, they remain physiologically alive, relying on their adjacent companion cells, and are therefore classified as living components of the phloem.

The incorrect option is 2: A, B, D and E

This option is incorrect because it includes **(D) Prosenchyma**, which is a collective term for certain dead, supportive, or conducting tissues. Prosenchyma cells are typically long, narrow elements with tapering ends, which is a structural description often applied to highly elongated, sclerenchymatous fibers or tracheary elements of the xylem. Sclerenchyma fibers, which provide the bulk of rigid mechanical support in mature plant parts, develop thick, lignified secondary walls and, by definition, lose their protoplast and are non-living (dead) at functional maturity. Since Chlorenchyma, Collenchyma, and Sieve elements are correctly identified as living, the inclusion of Prosenchyma renders this option wrong.

The incorrect option is 3: A and E

This option is incomplete and thus incorrect because it excludes a major cell type that is unambiguously living at maturity: **(B) Collenchyma**. Collenchyma tissue, which is composed of living cells, is vital for the plasticity and structural support of actively growing stems and leaves. Unlike the highly specialized and partially reduced protoplast of a Sieve element, a collenchyma cell possesses a dense, fully functional protoplast and is metabolically robust. By omitting the living collenchyma from the list, the option fails to account for all the living cells presented in the question's list of codes.

The incorrect option is 4: A, B and D

This option is incorrect for two main reasons concerning the status of the phloem and the inclusion of non-living tissue. First, it correctly identifies Chlorenchyma (A) and Collenchyma (B) as living but wrongly omits **(E) Sieve elements**, which are the living cells responsible for sugar transport in the phloem. A critical aspect of phloem function is the living nature of the sieve elements, which distinguishes them from the dead conducting cells of the xylem. Second, this option incorrectly includes **(D) Prosenchyma**. As previously stated, prosenchyma is synonymous with certain non-living mechanical fibers, making its inclusion in a list of living cells factually incorrect and demonstrating a lack of precision regarding the state of these supportive tissues at maturity.