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All species have secondary xylem, which is relatively uniform in structure throughout this group. Many conifers become tall trees: the secondary xylem of such trees is used and marketed as softwood. angiosperms (Angiospermae): there are approximately 250,000 [9] known species of angiosperms. Within this group secondary xylem is rare in the ...
The cells in vascular tissue are typically long and slender. Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form should be similar to pipes. The individual cells of phloem are connected end-to-end, just as the sections of a pipe might be.
The cambium present between primary xylem and primary phloem is called the intrafascicular cambium (within vascular bundles). During secondary growth, cells of medullary rays, in a line (as seen in section; in three dimensions, it is a sheet) between neighbouring vascular bundles, become meristematic and form new interfascicular cambium ...
Although its primary function is transport of sugars, phloem may also contain cells that have a mechanical support function. These are sclerenchyma cells which generally fall into two categories: fibres and sclereids. Both cell types have a secondary cell wall and are dead at maturity. The secondary cell wall increases their rigidity and ...
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.
In vascular cambium, the primary phloem and xylem are produced by the apical meristem. After this initial development, secondary phloem and xylem are produced by the lateral meristem. The two are connected through a thin layer of parenchymal cells which are differentiated into the fascicular cambium.
Stained Xylem Vessel in Red/Orange (x400 magnification) In secondary xylem – the xylem that is produced as a stem thickens rather than when it first appears – a vessel element originates from the vascular cambium. A long cell, oriented along the axis of the stem, called a "fusiform initial", divides along its length forming new vessel elements.
There is also a tissue between xylem and phloem, which is the cambium. The xylem typically lies towards the axis ( adaxial ) with phloem positioned away from the axis ( abaxial ). In a stem or root this means that the xylem is closer to the centre of the stem or root while the phloem is closer to the exterior.