Q.The specialised living cell that stays connected to a sieve tube element through pit fields and helps regulate its activity is the:

Companion cells assist the sieve tube elements in the phloem, so the answer is (C).

Phloem transports food (mainly sucrose). Its conducting cells are the sieve tube elements, which lose their nucleus at maturity. Each sieve tube element is associated with a specialised living, nucleated companion cell connected to it through plasmodesmata (pit fields).

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Companion cells are found in phloem, closely associated with sieve tube elements (sieve elements), whose functions they support.

In angiosperm phloem, each sieve tube element is closely associated with a specialised parenchyma cell called a companion cell. Both arise from the same mother cell by longitudinal division and remain connected throughout life by numerous plasmodesmata (pit connections). Because mature sieve tube elements lose their nucleus and much of their organelle machinery, they depend on the companion cell to maintain their metabolic activity, and the companion cell also helps in the loading and unloading of photosynthates (sugars) into and out of the sieve tubes.

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Phloem is the vascular tissue that conducts the food (organic solutes made during photosynthesis) from source (leaves) to sink (roots, fruits, storage organs) throughout the plant.

Phloem is composed of sieve tube elements, companion cells, phloem fibres, and phloem parenchyma. Unlike xylem (which conducts water and minerals upward, mostly by transpiration pull, in dead conducting cells), phloem transport:

• Moves in living sieve tube elements (which lack a nucleus but stay alive with the help of adjoining companion cells). …

Companion cells occur in phloem.

Companion cells are living cells that lie alongside the sieve tube elements of the phloem and help control their functioning (loading/unloading of food). They are a component of phloem, not of xylem or the ep …

Phloem (bast) fibres are elongated, thick-walled, lignified sclerenchyma cells that provide mechanical strength.

Phloem is a complex tissue made of four elements: sieve tube elements, companion cells, phloem parenchyma and phloem fibres (also called bast fibres). Unlike the first three, which are living conducting/associated cells, phloem fibres are sclerenchymatous — elongated, dead at maturity, with thic …

Companion cells are living cells found alongside sieve tube elements in phloem, connected by numerous plasmodesmata, and they help maintain the metabolic activity of the enucleate sieve tubes.

Phloem is composed of sieve tubes, companion cells, phloem parenchyma, and phloem fibres. Sieve tube elements lose their nucleus at maturity, so they depend on their adjoining companion cells (which retain a nucleus and dense cytoplasm) for the proteins and metabolic support needed to load/transport sugars (translocation). This intimate structur …