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In phloem, which of the following cells are dead cells?
Companion cells
Sieve cells
Phloem fibres
Phloem parenchyma
Phloem fibres
Phloem is a complex permanent tissue in plants responsible for the translocation of food. Among its four componentsтАФsieve tubes, companion cells, phloem parenchyma, and phloem fibresтАФthe phloem fibres (also known as bast fibres) are the only dead cells at maturity, providing mechanical support.
Phloem is a complex permanent tissue in plants responsible for the translocation of food. Among its four componentsтАФsieve tubes, companion cells, phloem parenchyma, and phloem fibresтАФthe phloem fibres (also known as bast fibres) are the only dead cells at maturity, providing mechanical support.
Think of phloem fibres like the steel rebar inside a concrete pillar; while the living cells (companion cells) manage the traffic of resources, the dead fibres act as the rigid 'scaffold' that prevents the plant from collapsing under its own weight.
P-F (Phloem Fibres) are Dead; S-C-P (Sieve, Companion, Parenchyma) are Living.
Phloem fibres are sclerenchymatous cells. During their maturation, they undergo secondary wall thickening with lignin deposition, which leads to the death of the protoplast. This structural modification provides tensile strength to the plant body.
Phloem tissue consists of four cell types: Sieve tube elements, Companion cells, Phloem parenchyma, and Phloem fibres.
Sieve tube elements, companion cells, and phloem parenchyma are living cells.
Phloem fibres are the only dead components of the phloem and are usually absent in primary phloem.
Lignification is the process responsible for the cell wall hardening in phloem fibres.
Phloem fibres provide essential mechanical support and rigidity to the plant stem.
Once matured, phloem fibres cannot perform metabolic functions like transport or storage due to the absence of a living protoplast.
Used commercially to produce ropes, mats, and sacking materials (e.g., jute, hemp, and flax fibres).
Acts as the structural skeletal system for plant stems.
Sieve tube elements are unique because they lose their nucleus at maturity to facilitate efficient sap transport.
Option A (Companion cells) are living cells that regulate metabolic activities of sieve tubes.
Option B (Sieve cells) are living, elongated cells involved in conduction.
Option D (Phloem parenchyma) are living cells involved in storage and lateral conduction of food.
C is correct тАФ Phloem fibres are the only dead cells present in the phloem tissue at maturity.
Always remember that in vascular tissues, 'fibres' (xylem fibres or phloem fibres) are almost always dead sclerenchyma, while 'parenchyma' is living.
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