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The major difference between sieve cells and sieve tube members is the lack of sieve plates in sieve cells. [1] They have a very narrow diameter and tend to be longer in length than sieve tube elements as they are generally associated with albuminous cells. [ 4 ]
All of the cellular functions of a sieve-tube element are carried out by the (much smaller) companion cell, a typical nucleate plant cell except the companion cell usually has a larger number of ribosomes and mitochondria. The dense cytoplasm of a companion cell is connected to the sieve-tube element by plasmodesmata. [10]
As a result, the concentration of sucrose increases in the sieve tube elements. This causes water to move into the sieve tube element by osmosis, creating pressure that pushes the sap down the tube. In sugar sinks, cells actively transport sucrose out of the sieve tube elements, first to the apoplast and then to the symplast of the sink.
Hartig was the first to discover and name the sieve tube element cells (as Siebfasern - sieve fibres and Siebröhren - sieve tubes) in 1837. His zoologist author abbreviation is Hartig. He described many gall wasp species.
It is the companion cells that are nestled between sieve-tube members that function in some manner bringing about the conduction of food. Sieve-tube members that are alive contain a polymer called callose, a carbohydrate polymer, forming the callus pad/callus, the colourless substance that covers the sieve plate.
Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem Detail of the vasculature of a bramble leaf Translocation in vascular plants ...
Sieve, in medicine, a "surgical sieve" refers to a very general list of diagnostic or pathological headings, against which any finding can be compared; Sieving coefficient, used in transport phenomena, in chemistry; Sieve tube element, an elongated cell in the phloem tissue of flowering plants
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