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A tracheid is a long and tapered lignified cell in the xylem of vascular plants. It is a type of conductive cell called a tracheary element.
A tracheid, once cavitated, cannot have its embolism removed and return to service (except in a few advanced angiosperms [40] [41] which have developed a mechanism of doing so). Therefore, it is well worth plants' while to avoid cavitation occurring.
A tracheid cell wall usually contains the polymer lignin. The phloem , on the other hand, consists of living cells called sieve-tube members . Between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through.
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 ...
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Parenchyma is a versatile ground tissue that generally constitutes the "filler" tissue in soft parts of plants. It forms, among other things, the cortex (outer region) and pith (central region) of stems, the cortex of roots, the mesophyll of leaves, the pulp of fruits, and the endosperm of seeds.
The presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants. It was once thought that vessel elements were an evolutionary innovation of flowering plants, but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re-examined; vessel elements in ...
Sieve cells are long, conducting cells in the phloem that do not form sieve tubes. The major difference between sieve cells and sieve tube members is the lack of sieve plates in sieve cells. [1]