companion cell


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Related to companion cell: Sieve cells

companion cell

n.
A specialized parenchyma cell, located in the phloem of flowering plants and closely associated in development and function with a sieve-tube element.
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[2.] Riedel C, Brinkmeier T, Kutzne H, Plewig G, Frosch PJ: Late onset of a facial variant of steatocystoma multiplex--calretinin as a specific marker of the follicular companion cell layer.
How a cell could function without a nucleus has long puzzled scientists, and we now believe that the close association of a sieve tube member with a companion cell allows for its regulation.
Since the vascular tissues in palms are nonrenewable, they must function indefinitely, and Tomlinson and Huggett point out that sieve tubes and their companion cells are remarkable examples of cell longevity as they maintain a long-distance transport function without replacement throughout the life of the stem, which could be for centuries.

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