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In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Ancient Greek word φλοιός (phloiós), meaning "bark". [3] [4] The term was introduced by Carl Nägeli in 1858. [5] [6] Different types of phloem can be distinguished. The early phloem formed in the growth apices is called protophloem.
Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There are also two meristems associated with vascular tissue: the vascular cambium and the cork cambium.
Ep = epidermis; C = cortex; BF = bast fibres; P = phloem; X = xylem; Pi = pith Women in southern Norway weaving with linden bast fibres Ndimbu mask from Tanganyika, made with wood, hair and bast Bast fibre (also called phloem fibre or skin fibre ) is plant fibre collected from the phloem (the "inner bark", sometimes called "skin") or bast ...
The phloem tissue arises from the cell facing outside and consists of sieve tubes and their companion cells. The function of phloem tissue is to distribute food from photosynthetic tissue to other tissues. The two tissues are separated by cambium, a tissue that divides to form xylem or phloem cells.
The rhytidome is the most familiar part of bark, being the outer layer that covers the trunks of trees. It is composed mostly of dead cells and is produced by the formation of multiple layers of suberized periderm, cortical and phloem tissue. [33] The rhytidome is especially well developed in older stems and roots of trees.
The phloem is the living portion of the vascular system of a plant, and serves to move sugars and photosynthate from source cells to sink cells. Phloem tissue is made of sieve elements and companion cells, and is surrounded by parenchyma cells. The sieve element cells work as the main player in transport of phloem sap.
The fascicular and interfascicular cambia thus join up to form a ring (in three dimensions, a tube) which separates the primary xylem and primary phloem, the cambium ring. The vascular cambium produces secondary xylem on the inside of the ring, and secondary phloem on the outside, pushing the primary xylem and phloem apart.
As tracheids evolved along with secondary xylem tissues, specialized inter-tracheid pits appeared. [3] Tracheid length and diameter also increased, with tracheid diameter increasing to an average length of 80 μm by the end of the Devonian period. [7] Tracheids then evolved into the vessel elements and structural fibers that make up angiosperm ...