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The trunk consists of five main parts: The outer bark, inner bark , cambium, sapwood (live xylem), and heartwood (dead xylem). [2] From the outside of the tree working in: The first layer is the outer bark; this is the protective outermost layer of the trunk. Under this is the inner bark which is called the phloem. The phloem is how the tree ...
In the stems of some Asterales dicots, there may be phloem located inwardly from the xylem as well. Between the xylem and phloem is a meristem called the vascular cambium. This tissue divides off cells that will become additional xylem and phloem. This growth increases the girth of the plant, rather than its length.
Since the valuable fibres are located in the phloem, they must often be separated from the woody core, the xylem, and sometimes also from the epidermis. The process for this is retting , and can be performed by micro-organisms either on land (nowadays the most important) or in water, or by chemicals (for instance high pH and chelating agents ...
Because phloem tubes are located outside the xylem in most plants, a tree or other plant can be killed by stripping away the bark in a ring on the trunk or stem. With the phloem destroyed, nutrients cannot reach the roots, and the tree/plant will die.
Damage or destruction of the phloem impedes the transport of photosynthetic products throughout the plant; in extreme cases, when a band of phloem all the way around the stem is removed, the plant will usually quickly die. Bark damage in horticultural applications, as in gardening and public landscaping, results in often unwanted aesthetic damage.
Most of these cells transform into xylem and phloem. But certain cells don't transform into xylem and phloem and remain as such. [clarification needed] These cells cut out by the cambium towards the periphery are phloem parenchyma while those towards the pith are xylem parenchyma. Both of these cells together work as secondary medullary rays.
Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem I 4. Phloem I 5. Sclerenchyma 6. Cortex 7. Epidermis. In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1]
Xylem is the water-conducting tissue, and the secondary xylem provides the raw material for the forest products industry. [26] Xylem and phloem tissues each play a part in the conduction processes within plants. Sugars are conveyed throughout the plant in the phloem; water and other nutrients pass through the xylem.