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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.
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.
Phloem is a complex tissue, consisting of two main cell types, the sieve tubes and the intimately associated companion cells, together with parenchyma cells, phloem fibres and sclereids. [ 19 ] : 171 Sieve tubes are joined end-to-end with perforated end-plates between known as sieve plates , which allow transport of photosynthate between the ...
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 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.
The main functions of tracheid cells are to transport water and inorganic salts, and to provide structural support for trees. There are often pits on the cell walls of tracheids, which allows for water flow between cells. Tracheids are dead at functional maturity and do not have a protoplast.