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Internal phloem is mostly primary, and begins differentiation later than the external phloem and protoxylem, though it is not without exceptions. In some other families ( Amaranthaceae , Nyctaginaceae , Salvadoraceae ), the cambium also periodically forms inward strands or layers of phloem, embedded in the xylem: Such phloem strands are called ...
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.
There are four primary patterns to the arrangement of protoxylem and metaxylem in stems and roots. Centrarch refers to the case in which the primary xylem forms a single cylinder in the center of the stem and develops from the center outwards. The protoxylem is thus found in the central core, and the metaxylem is in a cylinder around it. [45]
Albuminous cells have long, unspecialized areas with ends that overlap with those of other sieve cells and contain nutrients and store food in order to nourish tissues. [5] They enable the sieve cells to be connected to parenchyma, functional tissue in the organs, which helps to stabilize the tissue and transport nutrients.
Sugars are conveyed throughout the plant in the phloem; water and other nutrients pass through the xylem. Conduction occurs from a source to a sink for each separate nutrient. Sugars are produced in the leaves (a source) by photosynthesis and transported to the growing shoots and roots (sinks) for use in growth, cellular respiration or storage.
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.
Primarily, phloem carries dissolved food substances throughout the plant. This conduction system is composed of sieve-tube member and companion cells, that are without secondary walls. The parent cells of the vascular cambium produce both xylem and phloem. This usually also includes fibers, parenchyma and ray cells.
A sugar source is any part of the plant that is producing or releasing sugar. During the plant's growth period, usually during the spring, storage organs such as the roots are sugar sources, and the plant's many growing areas are sugar sinks. After the growth period, when the meristems are dormant, the leaves are sources, and storage organs are ...